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I'm using a 48V E-bike battery pack in a proof of concept type experiment. The battery pack is rated at 20Ah, with a discharage of 50A, and max discharge of 100A.
The electric motor can pull up to 100A - so I'd like to put a circuit breaker in line with the battery, with the idea being that if someone accidentally gets too excited on the throttle, the circuit breaker would trip long before the BMS does.? ?(This is especially after the relevant post about the BMS protection circuits being an unknown quantity in sealed battery systems!)
Questions:
1) What is a good circuit breaker for a 48V system?? I'm thinking around 25-30A.? ?Most seem rated for 12V, some up to 48V.? I've only found one so far that is rated for 72V.
2)? Can I use a "48V (max?)" rated circuit breaker?? ?Is that intended for a 48V system that really goes up to 56-58V at peak charge, or is it really strictly limited for 48V (and intended for 32V systesms)??
3)? Is a standard 30A blade fuse ok to use in a 48V circuit?? Many don't seem to have voltage ratings...
Thanks, John
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Maybe these will work for you?
https://www.ebay.com/itm/30A-300A-AMP-Circuit-Breaker-Fuse-Manual-Switch-12-48V-DC-Car-Boat-Waterproof-/143422006751
On Sunday, May 3, 2020, 05:27:43 PM PDT, john via groups.io <oak_box@...> wrote:
I'm using a 48V E-bike battery pack in a proof of concept type experiment. The battery pack is rated at 20Ah, with a discharage of 50A, and max discharge of 100A.
The electric motor can pull up to 100A - so I'd like to put a circuit breaker in line with the battery, with the idea being that if someone accidentally gets too excited on the throttle, the circuit breaker would trip long before the BMS does.? ?(This is especially after the relevant post about the BMS protection circuits being an unknown quantity in sealed battery systems!)
Questions:
1) What is a good circuit breaker for a 48V system?? I'm thinking around 25-30A.? ?Most seem rated for 12V, some up to 48V.? I've only found one so far that is rated for 72V.
2)? Can I use a "48V (max?)" rated circuit breaker?? ?Is that intended for a 48V system that really goes up to 56-58V at peak charge, or is it really strictly limited for 48V (and intended for 32V systesms)??
3)? Is a standard 30A blade fuse ok to use in a 48V circuit?? Many don't seem to have voltage ratings...
Thanks, John
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I saw some similar breakers to those on Amazon.? The ones you mention below have a 50V rating.? The peak charging voltage for a 48V battery system is ~56V.? ? I'm reluctant to use a breaker that's only rated to 50V in a system that will regularly hit and slightly exceed that rating.
I ended up ordering this one from Amazon, with a rating of 12V - 72V:
Though, that one will take a couple of weeks to arrive.? I was thinking of temporarily putting a 30A inline fuse in the circuit while I wait.? ?And then....? discovered all the public boat ramps are still closed.? The fully qualified breaker may be here before I can get good access to a boat ramp.
The first test was to run the motor in a garbage can filled with water.? But that only allowed me to get the motor up to 100W (~2A).? ?
The next test will be to back the boat down a boat ramp so that the motor is in the water, and run the motor at the dock for about an hour at about 900W.? I'll be watching the voltage on the motor, and probably taking data points every 5-10 min.? At 900W (~18A) to 1000W (~20A@50V) - I am expecting that I'll end the test due to low battery voltage before I hit an hour.? ? But this will give me a good idea of how well the battery is working compared to the advertised rating.? ?And it will also give me confidence that I can run the boat a long enough to take it off the trailer and putz around.
From previous tests with AGM batteries, 600W got me about 4mph, while 960W only increased that another half mph.? ?Cruising at 500-600W? (~10-12A) should be about the sweet spot for this boat, and should hopefully get me well over an hour of cruising on a 20Ah battery, with some margin to spare.
John
On Sunday, May 3, 2020, 09:29:26 PM CDT, sw via groups.io <v1opps@...> wrote:
Maybe these will work for you?
https://www.ebay.com/itm/30A-300A-AMP-Circuit-Breaker-Fuse-Manual-Switch-12-48V-DC-Car-Boat-Waterproof-/143422006751
On Sunday, May 3, 2020, 05:27:43 PM PDT, john via groups.io <oak_box@...> wrote:
I'm using a 48V E-bike battery pack in a proof of concept type experiment. The battery pack is rated at 20Ah, with a discharage of 50A, and max discharge of 100A.
The electric motor can pull up to 100A - so I'd like to put a circuit breaker in line with the battery, with the idea being that if someone accidentally gets too excited on the throttle, the circuit breaker would trip long before the BMS does.? ?(This is especially after the relevant post about the BMS protection circuits being an unknown quantity in sealed battery systems!)
Questions:
1) What is a good circuit breaker for a 48V system?? I'm thinking around 25-30A.? ?Most seem rated for 12V, some up to 48V.? I've only found one so far that is rated for 72V.
2)? Can I use a "48V (max?)" rated circuit breaker?? ?Is that intended for a 48V system that really goes up to 56-58V at peak charge, or is it really strictly limited for 48V (and intended for 32V systesms)??
3)? Is a standard 30A blade fuse ok to use in a 48V circuit?? Many don't seem to have voltage ratings...
Thanks, John
|
Hi John,
Unless the device has a specific fuse called for, the main purpose for the fuse or breaker is to protect the wire. You do not want to use a device that calls for a fuse or breaker of 25 or 30 amps If using 14 ga wire as the wire max is 15 amps or thereabouts. A device wired with that same wire however may call for an in line 5 amp fuse at the specific device, and there may be multiple devices connected to the same wire and breaker but the fuse or breaker at the start of the run must be sized for the wire. Look at your device maximum draw in amps and size the wire and matching breaker/fuse size for that amperage. There are many charts available on the internet that specify wire size for various amperage.
Cheers,
Ric Sanders
Ric Sanders
Rsandersemail@...
|
Ric,
I've been thinking about your response.
The original plan is to put a fuse or breaker near the battery that would blow or trip at about 30 amps - well below the rated current drain of the battery of 50A, and far below the peak battery current of 100A.? The intention of this was to make sure the BMS of the battery never tripped (as I don't know what the BMS will do - if it has an internal fuse, will self reset, or will blow FETs and "brick" the battery).
I had found an inline fuse holder on Amazon that came with a 30A fuse.? But the wire on the fuse holder is only 12AWG.? I found one online reference that said 12AWG wire could handle up to 41A for "chassis wiring", but it wasn't clear that this was for STRANDED wire, and not SOLID wire.
Makes me wonder if the wire on the fuse holder might get rather warm if I ran at 20A for an extended period of time.
The other BIG concern that I have is whether a 30A blade fuse can be used for a 48V system.? ?Most seem to be rated for automotive use, generally 12V systems, with some fuses marked at 32V.
John
On Monday, May 4, 2020, 09:06:01 AM CDT, Ric Sanders <rsandersemail@...> wrote:
Hi John,
Unless the device has a specific fuse called for, the main purpose for the fuse or breaker is to protect the wire. You do not want to use a device that calls for a fuse or breaker of 25 or 30 amps If using 14 ga wire as the wire max is 15 amps or thereabouts. A device wired with that same wire however may call for an in line 5 amp fuse at the specific device, and there may be multiple devices connected to the same wire and breaker but the fuse or breaker at the start of the run must be sized for the wire. Look at your device maximum draw in amps and size the wire and matching breaker/fuse size for that amperage. There are many charts available on the internet that specify wire size for various amperage.
Cheers,
Ric Sanders
Ric Sanders
|
Maybe u can use two parallel fuses?
On Tuesday, May 5, 2020, 08:34:04 PM PDT, john via groups.io <oak_box@...> wrote:
Ric,
I've been thinking about your response.
The original plan is to put a fuse or breaker near the battery that would blow or trip at about 30 amps - well below the rated current drain of the battery of 50A, and far below the peak battery current of 100A.? The intention of this was to make sure the BMS of the battery never tripped (as I don't know what the BMS will do - if it has an internal fuse, will self reset, or will blow FETs and "brick" the battery).
I had found an inline fuse holder on Amazon that came with a 30A fuse.? But the wire on the fuse holder is only 12AWG.? I found one online reference that said 12AWG wire could handle up to 41A for "chassis wiring", but it wasn't clear that this was for STRANDED wire, and not SOLID wire.
Makes me wonder if the wire on the fuse holder might get rather warm if I ran at 20A for an extended period of time.
The other BIG concern that I have is whether a 30A blade fuse can be used for a 48V system.? ?Most seem to be rated for automotive use, generally 12V systems, with some fuses marked at 32V.
John
On Monday, May 4, 2020, 09:06:01 AM CDT, Ric Sanders <rsandersemail@...> wrote:
Hi John,
Unless the device has a specific fuse called for, the main purpose for the fuse or breaker is to protect the wire. You do not want to use a device that calls for a fuse or breaker of 25 or 30 amps If using 14 ga wire as the wire max is 15 amps or thereabouts. A device wired with that same wire however may call for an in line 5 amp fuse at the specific device, and there may be multiple devices connected to the same wire and breaker but the fuse or breaker at the start of the run must be sized for the wire. Look at your device maximum draw in amps and size the wire and matching breaker/fuse size for that amperage. There are many charts available on the internet that specify wire size for various amperage.
Cheers,
Ric Sanders
Ric Sanders
|
I don't think that would be a good idea.? There would be no way to guarantee that the current was split evenly between the two wires.
And I'd still have the same concern about the voltage rating. I'm not having much luck finding fuses rated for 48VDC systems.
John
On Tuesday, May 5, 2020, 10:37:42 PM CDT, sw via groups.io <v1opps@...> wrote:
Maybe u can use two parallel fuses?
On Tuesday, May 5, 2020, 08:34:04 PM PDT, john via groups.io <oak_box@...> wrote:
Ric,
I've been thinking about your response.
The original plan is to put a fuse or breaker near the battery that would blow or trip at about 30 amps - well below the rated current drain of the battery of 50A, and far below the peak battery current of 100A.? The intention of this was to make sure the BMS of the battery never tripped (as I don't know what the BMS will do - if it has an internal fuse, will self reset, or will blow FETs and "brick" the battery).
I had found an inline fuse holder on Amazon that came with a 30A fuse.? But the wire on the fuse holder is only 12AWG.? I found one online reference that said 12AWG wire could handle up to 41A for "chassis wiring", but it wasn't clear that this was for STRANDED wire, and not SOLID wire.
Makes me wonder if the wire on the fuse holder might get rather warm if I ran at 20A for an extended period of time.
The other BIG concern that I have is whether a 30A blade fuse can be used for a 48V system.? ?Most seem to be rated for automotive use, generally 12V systems, with some fuses marked at 32V.
John
On Monday, May 4, 2020, 09:06:01 AM CDT, Ric Sanders <rsandersemail@...> wrote:
Hi John,
Unless the device has a specific fuse called for, the main purpose for the fuse or breaker is to protect the wire. You do not want to use a device that calls for a fuse or breaker of 25 or 30 amps If using 14 ga wire as the wire max is 15 amps or thereabouts. A device wired with that same wire however may call for an in line 5 amp fuse at the specific device, and there may be multiple devices connected to the same wire and breaker but the fuse or breaker at the start of the run must be sized for the wire. Look at your device maximum draw in amps and size the wire and matching breaker/fuse size for that amperage. There are many charts available on the internet that specify wire size for various amperage.
Cheers,
Ric Sanders
Ric Sanders
|
For voltage issues you put the fuses in series, not parallel.
I've actually seen DC circuits with the fuses in series to get
the isolating voltage required.
Fuses (and circuit breakers) have a break voltage rating (and
fault current interruption ratings) that are sometimes a little
difficult to find. Every one thinks about the trip current and
forgets the rest.
The voltage and fault current ratings are rather important for
DC. Probably not so much an issue with 48v, but once to get into
the 100v plus region you have to pay attention.
DC arcs will not self extinguish and resulting plasma conduit can
have a very low resistance and sustain quite a significant current
flow indefinitely.
I recently took apart a 750v volt 400amp fuse that had blown. It
was full of sand. The idea being when the fuse element burns
through the sand fills the gap and stops the current flowing
across the gap in a plasma tunnel.
The DC circuit breakers in the same machine have magnetic quench
/ arch chute mechanisms to quench the arc. (The magnetic field
pushes the arc up the chute). A breaker designed for AC of the
same rating would probably self-destruct (and take much other
equipment with it) if mistakenly used the same location.
On 6/5/20 1:37 pm, sw via groups.io
wrote:
toggle quoted message
Show quoted text
Maybe u can use two parallel fuses?
On Tuesday, May 5, 2020, 08:34:04 PM PDT, john via
groups.io <oak_box@...> wrote:
Ric,
I've been thinking about your
response.
The original plan is to put a fuse or
breaker near the battery that would blow or trip
at about 30 amps - well below the rated current
drain of the battery of 50A, and far below the
peak battery current of 100A.? The intention of
this was to make sure the BMS of the battery never
tripped (as I don't know what the BMS will do - if
it has an internal fuse, will self reset, or will
blow FETs and "brick" the battery).
I had found an inline fuse holder on
Amazon that came with a 30A fuse.? But the wire on
the fuse holder is only 12AWG.? I found one online
reference that said 12AWG wire could handle up to
41A for "chassis wiring", but it wasn't clear that
this was for STRANDED wire, and not SOLID wire.
Makes me wonder if the wire on the
fuse holder might get rather warm if I ran at 20A
for an extended period of time.
The other BIG concern that I have is
whether a 30A blade fuse can be used for a 48V
system.? ?Most seem to be rated for automotive
use, generally 12V systems, with some fuses marked
at 32V.
John
Hi John,
Unless the device has a specific
fuse called for, the main purpose for the fuse
or breaker is to protect the wire. You do not
want to use a device that calls for a fuse or
breaker of 25 or 30 amps If using 14 ga wire
as the wire max is 15 amps or thereabouts. A
device wired with that same wire however may
call for an in line 5 amp fuse at the specific
device, and there may be multiple devices
connected to the same wire and breaker but the
fuse or breaker at the start of the run must
be sized for the wire. Look at your device
maximum draw in amps and size the wire and
matching breaker/fuse size for that amperage.
There are many charts available on the
internet that specify wire size for various
amperage.
Cheers,
Ric Sanders
Ric Sanders
|
On 6/5/20 1:41 pm, john via groups.io
wrote:
I don't think that would be a
good idea.? There would be no way to guarantee that the
current was split evenly between the two wires.
And I'd still have the same
concern about the voltage rating.
I'm not having much luck
finding fuses rated for 48VDC systems.
Look for Telco surplus. Telco systems are traditionally 48v DC.
|
Higher amps but 48v
On Tuesday, May 5, 2020, 08:41:39 PM PDT, john via groups.io <oak_box@...> wrote:
I don't think that would be a good idea.? There would be no way to guarantee that the current was split evenly between the two wires.
And I'd still have the same concern about the voltage rating. I'm not having much luck finding fuses rated for 48VDC systems.
John
On Tuesday, May 5, 2020, 10:37:42 PM CDT, sw via groups.io <v1opps@...> wrote:
Maybe u can use two parallel fuses?
On Tuesday, May 5, 2020, 08:34:04 PM PDT, john via groups.io <oak_box@...> wrote:
Ric,
I've been thinking about your response.
The original plan is to put a fuse or breaker near the battery that would blow or trip at about 30 amps - well below the rated current drain of the battery of 50A, and far below the peak battery current of 100A.? The intention of this was to make sure the BMS of the battery never tripped (as I don't know what the BMS will do - if it has an internal fuse, will self reset, or will blow FETs and "brick" the battery).
I had found an inline fuse holder on Amazon that came with a 30A fuse.? But the wire on the fuse holder is only 12AWG.? I found one online reference that said 12AWG wire could handle up to 41A for "chassis wiring", but it wasn't clear that this was for STRANDED wire, and not SOLID wire.
Makes me wonder if the wire on the fuse holder might get rather warm if I ran at 20A for an extended period of time.
The other BIG concern that I have is whether a 30A blade fuse can be used for a 48V system.? ?Most seem to be rated for automotive use, generally 12V systems, with some fuses marked at 32V.
John
On Monday, May 4, 2020, 09:06:01 AM CDT, Ric Sanders <rsandersemail@...> wrote:
Hi John,
Unless the device has a specific fuse called for, the main purpose for the fuse or breaker is to protect the wire. You do not want to use a device that calls for a fuse or breaker of 25 or 30 amps If using 14 ga wire as the wire max is 15 amps or thereabouts. A device wired with that same wire however may call for an in line 5 amp fuse at the specific device, and there may be multiple devices connected to the same wire and breaker but the fuse or breaker at the start of the run must be sized for the wire. Look at your device maximum draw in amps and size the wire and matching breaker/fuse size for that amperage. There are many charts available on the internet that specify wire size for various amperage.
Cheers,
Ric Sanders
Ric Sanders
|
Any fuse rated over the voltage of the system will work.? Any fuse rated under the system voltage will arc and should not be used.?
Example would be a 230 fuse would work. It's about the gap or length of fuse wire.? You are protecting amp with fuse not volts.?
You could put 500 volts to that fuse and nothing would happen till you exceeded the amp rating, then you would have a fireball because the gap would be to small to break the circuit.?
Ric,
I've been thinking about your response.
The original plan is to put a fuse or breaker near the battery that would blow or trip at about 30 amps - well below the rated current drain of the battery of 50A, and far below the peak battery current of 100A.? The intention of this was to make sure the BMS of the battery never tripped (as I don't know what the BMS will do - if it has an internal fuse, will self reset, or will blow FETs and "brick" the battery).
I had found an inline fuse holder on Amazon that came with a 30A fuse.? But the wire on the fuse holder is only 12AWG.? I found one online reference that said 12AWG wire could handle up to 41A for "chassis wiring", but it wasn't clear that this was for STRANDED wire, and not SOLID wire.
Makes me wonder if the wire on the fuse holder might get rather warm if I ran at 20A for an extended period of time.
The other BIG concern that I have is whether a 30A blade fuse can be used for a 48V system.? ?Most seem to be rated for automotive use, generally 12V systems, with some fuses marked at 32V.
John
Hi John,
Unless the device has a specific fuse called for, the main purpose for the fuse or breaker is to protect the wire. You do not want to use a device that calls for a fuse or breaker of 25 or 30 amps If using 14 ga wire as the wire max is 15 amps or thereabouts. A device wired with that same wire however may call for an in line 5 amp fuse at the specific device, and there may be multiple devices connected to the same wire and breaker but the fuse or breaker at the start of the run must be sized for the wire. Look at your device maximum draw in amps and size the wire and matching breaker/fuse size for that amperage. There are many charts available on the internet that specify wire size for various amperage.
Cheers,
Ric Sanders
Ric Sanders
|
John,
Can you clarify what your application is please?? You mention an electric motor that "can pull up to 100A" to be used "in a proof of concept type experiment".
Are you putting the motor aboard a vessel or testing on the bench?? [More specifically, what's the potential degree of loss in the event of a fire?? If you're running your system on a bench in a controlled environment where the loss might be a burnt wire, that's one thing.? But taking people aboard a vessel on the water requires an entirely different standard of care!]?
Do you know what motor (nominal rating in watts) the battery pack was intended to power? And what concepts are you looking to prove?
Ampacity of a wire is a function both of diameter/gauge *and* length.? In some situations, a 12 awg wire might safely carry 50 amps for brief periods, but it would not be prudent to create such a situation where there's meaningful risk of property or life.
I'm not an engineer or expert by any definition, but I would take the cautious approach, and size my load wires for the maximum expected load and required length of wire.? For 100 amps, over a few feet or so, that would mean 8 awg to me.? [I'm using 150 amp ANL type fuses and 7 awg wire to my motor that could pull 150 amps.]
Will there be any other loads on your battery?? Ideally, each load would have its own fuse, and your battery fuse sized to allow for the entire system.
Take a look at <
Good luck, and have fun!
[-tv]
Tom VanderMeulen
"Grace O'Malley"
Cape Dory 27
Monroe, MI
|
Tom,
That is a great resource!
Thank you so much for posting it.
Cheers,
Ric
Ric Sanders
Rsandersemail@...
|
Lots of solar energy systems are 48 volts. The solar, golf cart, and fork lift companies have DC fuses and DC breakers. Or electronics companies such as Mouser might have something:
On Tuesday, May 5, 2020, 8:55 PM, Matthew Geier <matthew@...> wrote:
On 6/5/20 1:41 pm, john via groups.io
wrote:
I don't think that would be a
good idea.? There would be no way to guarantee that the
current was split evenly between the two wires.
And I'd still have the same
concern about the voltage rating.
I'm not having much luck
finding fuses rated for 48VDC systems.
Look for Telco surplus. Telco systems are traditionally 48v DC.
|
Thomas, Below are some details of the application:
Boat:? ?The test platform is a home build plywood boat. Length:? 13' Beam:? 5'8" Weight:? ?(guess)? under 400 pounds
The boat has been re-powered with a Torqeedo Cruise 4R outboard.? 48V, max input 4KW.
The first experiment was to power the Torqeedo with a bank of four Group 31 Deka AGM 12V batteries. It worked, but the batteries were excessively heavy, took up a LOT of space, and provided no backup in the event that the primary bank died or suffered any kind of technical failure.
For the next experiment, I'd like to try running the boat on a lithium battery bank, for improved power density, depth of discharge, and overall weight/space.
Since I have zero prior experience with lithium batteries - the first step will be to use an Ebike battery from Amazon.? This is a bundled system: 48V Nominal 20AH rating Sustained current drain:? 50A Peak current:? 100A
The battery pack has a built in BMS.? However, there are no details about what happens if the BMS trips.? It may permanently disable the battery to prevent a catastrophic failure.
In this setup - the motor can pull up to 4KW, but the battery can only provide half that on a sustained basis.? If the operator accidentally or carelessly pushes the throttle to full speed, I would expect the battery BMS would trip - possibly permanently "bricking" the battery.
Therefore, I would like to put a fuse or breaker after the battery to gate the max drain of the battery to no more than about 40A.? The thought was that if I used a fuse or breaker of about 30A, it would blow before the battery BMS kicked in - giving me the opportunity to either replace the fuse or reset the breaker, and move on.
Protecting the battery with a 30A fuse or breaker should be a very conservative step.? All other wiring is being sized to support the current drain potential of the motor - which far exceeds what the battery can supply at this time.
From other responses - it sounds like the fuse/breaker must be rated for DC usage, and that the voltage rating should comfortably exceed the 48V system (with a max charging voltage of about 55V).
John
On Wednesday, May 6, 2020, 09:32:53 AM CDT, THOMAS VANDERMEULEN <tvinypsi@...> wrote:
John, Can you clarify what your application is please?? You mention an electric motor that "can pull up to 100A" to be used "in a proof of concept type experiment". Are you putting the motor aboard a vessel or testing on the bench?? [More specifically, what's the potential degree of loss in the event of a fire?? If you're running your system on a bench in a controlled environment where the loss might be a burnt wire, that's one thing.? But taking people aboard a vessel on the water requires an entirely different standard of care!]? Do you know what motor (nominal rating in watts) the battery pack was intended to power? And what concepts are you looking to prove? Ampacity of a wire is a function both of diameter/gauge *and* length.? In some situations, a 12 awg wire might safely carry 50 amps for brief periods, but it would not be prudent to create such a situation where there's meaningful risk of property or life. I'm not an engineer or expert by any definition, but I would take the cautious approach, and size my load wires for the maximum expected load and required length of wire.? For 100 amps, over a few feet or so, that would mean 8 awg to me.? [I'm using 150 amp ANL type fuses and 7 awg wire to my motor that could pull 150 amps.] Will there be any other loads on your battery?? Ideally, each load would have its own fuse, and your battery fuse sized to allow for the entire system. Take a look at < Good luck, and have fun! [-tv] Tom VanderMeulen "Grace O'Malley" Cape Dory 27 Monroe, MI
|
Hi John,
I'm betting I have the same one, just the 30AH version. Typically I'm not a fan of pre-packaged "black box" but this one has served me well. It capacity tested to exactly 30AH. While I don't recommend doing it often, if pushed to the limit, the BMS cuts power for a few seconds and automatically comes back on. Being its only a 20AH battery, for maximum cycle life of the battery I wouldn't push the 50 amp continuous limit for too long. That's a 2.5 C rate.?
Personally, I wouldn't worry about a fuse for testing.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 6, 2020, 04:37:36 PM EDT, john via groups.io <oak_box@...> wrote:
Thomas, Below are some details of the application:
Boat:? ?The test platform is a home build plywood boat. Length:? 13' Beam:? 5'8" Weight:? ?(guess)? under 400 pounds
The boat has been re-powered with a Torqeedo Cruise 4R outboard.? 48V, max input 4KW.
The first experiment was to power the Torqeedo with a bank of four Group 31 Deka AGM 12V batteries. It worked, but the batteries were excessively heavy, took up a LOT of space, and provided no backup in the event that the primary bank died or suffered any kind of technical failure.
For the next experiment, I'd like to try running the boat on a lithium battery bank, for improved power density, depth of discharge, and overall weight/space.
Since I have zero prior experience with lithium batteries - the first step will be to use an Ebike battery from Amazon.? This is a bundled system: 48V Nominal 20AH rating Sustained current drain:? 50A Peak current:? 100A
The battery pack has a built in BMS.? However, there are no details about what happens if the BMS trips.? It may permanently disable the battery to prevent a catastrophic failure.
In this setup - the motor can pull up to 4KW, but the battery can only provide half that on a sustained basis.? If the operator accidentally or carelessly pushes the throttle to full speed, I would expect the battery BMS would trip - possibly permanently "bricking" the battery.
Therefore, I would like to put a fuse or breaker after the battery to gate the max drain of the battery to no more than about 40A.? The thought was that if I used a fuse or breaker of about 30A, it would blow before the battery BMS kicked in - giving me the opportunity to either replace the fuse or reset the breaker, and move on.
Protecting the battery with a 30A fuse or breaker should be a very conservative step.? All other wiring is being sized to support the current drain potential of the motor - which far exceeds what the battery can supply at this time.
From other responses - it sounds like the fuse/breaker must be rated for DC usage, and that the voltage rating should comfortably exceed the 48V system (with a max charging voltage of about 55V).
John
On Wednesday, May 6, 2020, 09:32:53 AM CDT, THOMAS VANDERMEULEN <tvinypsi@...> wrote:
John, Can you clarify what your application is please?? You mention an electric motor that "can pull up to 100A" to be used "in a proof of concept type experiment". Are you putting the motor aboard a vessel or testing on the bench?? [More specifically, what's the potential degree of loss in the event of a fire?? If you're running your system on a bench in a controlled environment where the loss might be a burnt wire, that's one thing.? But taking people aboard a vessel on the water requires an entirely different standard of care!]? Do you know what motor (nominal rating in watts) the battery pack was intended to power? And what concepts are you looking to prove? Ampacity of a wire is a function both of diameter/gauge *and* length.? In some situations, a 12 awg wire might safely carry 50 amps for brief periods, but it would not be prudent to create such a situation where there's meaningful risk of property or life. I'm not an engineer or expert by any definition, but I would take the cautious approach, and size my load wires for the maximum expected load and required length of wire.? For 100 amps, over a few feet or so, that would mean 8 awg to me.? [I'm using 150 amp ANL type fuses and 7 awg wire to my motor that could pull 150 amps.] Will there be any other loads on your battery?? Ideally, each load would have its own fuse, and your battery fuse sized to allow for the entire system. Take a look at < Good luck, and have fun! [-tv] Tom VanderMeulen "Grace O'Malley" Cape Dory 27 Monroe, MI
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John,
My limited experience with the type of battery protection circuits you're dealing with in that bike battery is consistent with Matt's.? Calling it a BMS is overly generous, in my view, since it really only provides the functionality of an auto-resetting circuit protector.? When you're charging, it cuts off the charger flow when one of the cells reaching High Voltage Cutoff, and when you're discharging, it cuts off the flow when it reaches Low Voltage Cutoff or Maximum Current.? Depending on the design the over-current reset may indeed be quick as Matt describes.
Given your application, I'm inclined to agree with Matt on skipping the fuse or breaker at this point in your system development.? As you continue to develop your configuration, you might also want to track down the ABYC standards for electrical work, storage batteries, and electric propulsion just to stay on the safe side.? Just a thought.
[-tv]
Tom VanderMeulen
"Grace O'Malley"
Cape Dory 27
Monroe, Michigan
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Matt, Thanks for the response - that's very encouraging to hear!
The battery I ordered is the 20Ah version of this one from BTRPower:
From what I've seen so far - it seems pretty good.? I just haven't had a chance to test it under load yet.
I agree with you that I really don't want to run it for more than a burst at 50Ah! From data I collected with the AGM batteries, the boat moves about as fast as it's going to go (under batteries) at roughly 1000W or less (~20A).? ?Running at 12A should be about the sweet spot near 4mph, and should give me reasonable run time, even with just a 20Ah battery (at least for a short putter around trip...).
John
On Wednesday, May 6, 2020, 04:28:23 PM CDT, Matt Foley <matt@...> wrote:
Hi John,
I'm betting I have the same one, just the 30AH version. Typically I'm not a fan of pre-packaged "black box" but this one has served me well. It capacity tested to exactly 30AH. While I don't recommend doing it often, if pushed to the limit, the BMS cuts power for a few seconds and automatically comes back on. Being its only a 20AH battery, for maximum cycle life of the battery I wouldn't push the 50 amp continuous limit for too long. That's a 2.5 C rate.?
Personally, I wouldn't worry about a fuse for testing.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 6, 2020, 04:37:36 PM EDT, john via groups.io <oak_box@...> wrote:
Thomas, Below are some details of the application:
Boat:? ?The test platform is a home build plywood boat. Length:? 13' Beam:? 5'8" Weight:? ?(guess)? under 400 pounds
The boat has been re-powered with a Torqeedo Cruise 4R outboard.? 48V, max input 4KW.
The first experiment was to power the Torqeedo with a bank of four Group 31 Deka AGM 12V batteries. It worked, but the batteries were excessively heavy, took up a LOT of space, and provided no backup in the event that the primary bank died or suffered any kind of technical failure.
For the next experiment, I'd like to try running the boat on a lithium battery bank, for improved power density, depth of discharge, and overall weight/space.
Since I have zero prior experience with lithium batteries - the first step will be to use an Ebike battery from Amazon.? This is a bundled system: 48V Nominal 20AH rating Sustained current drain:? 50A Peak current:? 100A
The battery pack has a built in BMS.? However, there are no details about what happens if the BMS trips.? It may permanently disable the battery to prevent a catastrophic failure.
In this setup - the motor can pull up to 4KW, but the battery can only provide half that on a sustained basis.? If the operator accidentally or carelessly pushes the throttle to full speed, I would expect the battery BMS would trip - possibly permanently "bricking" the battery.
Therefore, I would like to put a fuse or breaker after the battery to gate the max drain of the battery to no more than about 40A.? The thought was that if I used a fuse or breaker of about 30A, it would blow before the battery BMS kicked in - giving me the opportunity to either replace the fuse or reset the breaker, and move on.
Protecting the battery with a 30A fuse or breaker should be a very conservative step.? All other wiring is being sized to support the current drain potential of the motor - which far exceeds what the battery can supply at this time.
From other responses - it sounds like the fuse/breaker must be rated for DC usage, and that the voltage rating should comfortably exceed the 48V system (with a max charging voltage of about 55V).
John
On Wednesday, May 6, 2020, 09:32:53 AM CDT, THOMAS VANDERMEULEN <tvinypsi@...> wrote:
John, Can you clarify what your application is please?? You mention an electric motor that "can pull up to 100A" to be used "in a proof of concept type experiment". Are you putting the motor aboard a vessel or testing on the bench?? [More specifically, what's the potential degree of loss in the event of a fire?? If you're running your system on a bench in a controlled environment where the loss might be a burnt wire, that's one thing.? But taking people aboard a vessel on the water requires an entirely different standard of care!]? Do you know what motor (nominal rating in watts) the battery pack was intended to power? And what concepts are you looking to prove? Ampacity of a wire is a function both of diameter/gauge *and* length.? In some situations, a 12 awg wire might safely carry 50 amps for brief periods, but it would not be prudent to create such a situation where there's meaningful risk of property or life. I'm not an engineer or expert by any definition, but I would take the cautious approach, and size my load wires for the maximum expected load and required length of wire.? For 100 amps, over a few feet or so, that would mean 8 awg to me.? [I'm using 150 amp ANL type fuses and 7 awg wire to my motor that could pull 150 amps.] Will there be any other loads on your battery?? Ideally, each load would have its own fuse, and your battery fuse sized to allow for the entire system. Take a look at < Good luck, and have fun! [-tv] Tom VanderMeulen "Grace O'Malley" Cape Dory 27 Monroe, MI
|
On May 6, 2020, at 6:25 PM, john via < oak_box@...> wrote:
Matt, Thanks for the response - that's very encouraging to hear!
The battery I ordered is the 20Ah version of this one from BTRPower:
From what I've seen so far - it seems pretty good.? I just haven't had a chance to test it under load yet.
I agree with you that I really don't want to run it for more than a burst at 50Ah! From data I collected with the AGM batteries, the boat moves about as fast as it's going to go (under batteries) at roughly 1000W or less (~20A).? ?Running at 12A should be about the sweet spot near 4mph, and should give me reasonable run time, even with just a 20Ah battery (at least for a short putter around trip...).
John
On Wednesday, May 6, 2020, 04:28:23 PM CDT, Matt Foley < matt@...> wrote:
Hi John,
I'm betting I have the same one, just the 30AH version. Typically I'm not a fan of pre-packaged "black box" but this one has served me well. It capacity tested to exactly 30AH. While I don't recommend doing it often, if pushed to the limit, the BMS cuts power for a few seconds and automatically comes back on. Being its only a 20AH battery, for maximum cycle life of the battery I wouldn't push the 50 amp continuous limit for too long. That's a 2.5 C rate.?
Personally, I wouldn't worry about a fuse for testing.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 6, 2020, 04:37:36 PM EDT, john via < oak_box@...> wrote:
Thomas, Below are some details of the application:
Boat:? ?The test platform is a home build plywood boat. Length:? 13' Beam:? 5'8" Weight:? ?(guess)? under 400 pounds
<1588795948729blob.jpg>
The boat has been re-powered with a Torqeedo Cruise 4R outboard.? 48V, max input 4KW.
The first experiment was to power the Torqeedo with a bank of four Group 31 Deka AGM 12V batteries. It worked, but the batteries were excessively heavy, took up a LOT of space, and provided no backup in the event that the primary bank died or suffered any kind of technical failure.
For the next experiment, I'd like to try running the boat on a lithium battery bank, for improved power density, depth of discharge, and overall weight/space.
Since I have zero prior experience with lithium batteries - the first step will be to use an Ebike battery from Amazon.? This is a bundled system: 48V Nominal 20AH rating Sustained current drain:? 50A Peak current:? 100A
The battery pack has a built in BMS.? However, there are no details about what happens if the BMS trips.? It may permanently disable the battery to prevent a catastrophic failure.
In this setup - the motor can pull up to 4KW, but the battery can only provide half that on a sustained basis.? If the operator accidentally or carelessly pushes the throttle to full speed, I would expect the battery BMS would trip - possibly permanently "bricking" the battery.
Therefore, I would like to put a fuse or breaker after the battery to gate the max drain of the battery to no more than about 40A.? The thought was that if I used a fuse or breaker of about 30A, it would blow before the battery BMS kicked in - giving me the opportunity to either replace the fuse or reset the breaker, and move on.
Protecting the battery with a 30A fuse or breaker should be a very conservative step.? All other wiring is being sized to support the current drain potential of the motor - which far exceeds what the battery can supply at this time.
From other responses - it sounds like the fuse/breaker must be rated for DC usage, and that the voltage rating should comfortably exceed the 48V system (with a max charging voltage of about 55V).
John
On Wednesday, May 6, 2020, 09:32:53 AM CDT, THOMAS VANDERMEULEN < tvinypsi@...> wrote:
John, Can you clarify what your application is please?? You mention an electric motor that "can pull up to 100A" to be used "in a proof of concept type experiment". Are you putting the motor aboard a vessel or testing on the bench?? [More specifically, what's the potential degree of loss in the event of a fire?? If you're running your system on a bench in a controlled environment where the loss might be a burnt wire, that's one thing.? But taking people aboard a vessel on the water requires an entirely different standard of care!]? Do you know what motor (nominal rating in watts) the battery pack was intended to power? And what concepts are you looking to prove? Ampacity of a wire is a function both of diameter/gauge *and* length.? In some situations, a 12 awg wire might safely carry 50 amps for brief periods, but it would not be prudent to create such a situation where there's meaningful risk of property or life. I'm not an engineer or expert by any definition, but I would take the cautious approach, and size my load wires for the maximum expected load and required length of wire.? For 100 amps, over a few feet or so, that would mean 8 awg to me.? [I'm using 150 amp ANL type fuses and 7 awg wire to my motor that could pull 150 amps.] Will there be any other loads on your battery?? Ideally, each load would have its own fuse, and your battery fuse sized to allow for the entire system. Take a look at < Good luck, and have fun! [-tv] Tom VanderMeulen "Grace O'Malley" Cape Dory 27 Monroe, MI
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Ric Sanders
Matthew Geier
THOMAS VANDERMEULEN