|
I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..?
I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
|
The leads you should really worry about being long are the high current wires.? If they're just sense wires, then they draw minimal current so don't worry about that length so much...within reason naturally. Noise pickup could theoretically be an issue at extremely long lengths.? That's why shielding is good for those.? Matching is generally no big deal except for the individual pairs.? Those pairs should be matched...and _twisted_ pairs.
However, the charging leads _do_ qualify as high current if you're charging at 250A, so there's that.? Even still, you really want them _shorter_ rather than matched.
Also, the LOOP AREA of the high current wires are a BIG DEAL.? Plus and minus should be next to each other and (ideally) also twisted for best results.? Twisting lengthens them slightly but you'll be generating a magnetic field relative to the amount of current.? The bigger the loop area the bigger the radiated field.? Twisting radiates it in such a way as to cancel with each successive twist.? Your compass probably will like that better.
Fair winds and following seas!
Dave
On Wednesday, May 3, 2023 at 04:54:20 AM CDT, aasmith970@... <aasmith970@...> wrote:
I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..?
I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
|
First of all, you can certainly split up a pack into multiple boxes---this has been done since the first EVs were produced back in the late 1800’s.? I have no comment about aluminum except to be sure that’s what you really want (vs, say, wood/glass/epoxy molded to the hull).? With my 700ah, nom. 42v pack on , I have my pack split into 4 subpacks, each of the same nom. 42v (31v to 49v Lithium Ion).? Same story with Dan Pence’s “Ginger” (one of the first noted E-boat conversions in recent decades and 3rd earliest or so at evalbum.com --- Dan uses the same battery modules as I use and has a row of batteries on the starboard and one on the port side. ?He has his mounted in a ply/glass/epoxy cavity originally built and sized for lead-acid batteries back in the late 1990’s---the cavities fit these ex-THINK EV Enerdel stacks well. ?He and I both use 4ga wire from each 35ah stack thru fuses to common points on each side.? Then larger gauge cable to connect the starboard and port packs. ? Details matter. ?You indicate your pack will be 280ah at 48v and that the cells themselves are 280ah. ?Given that, your splitting of the pack results in two 280ah 24v packs in series.? Size your cables based on how much current you ever expect to draw from the pack.? Let’s say max. 7.5kw, then we’re talking about 150amps max. ?So sure, a gauge of 1, 1/0 or 0 probably would be fine.? Make sure you have a fuse near each of your 2 half-packs. ? As for BMS connections, it’s not really as simple as presented by Dave.? Yes, the cell connection wires are “sense” wires but they typically are also “bypass” wires---that is, they need to pass the current that your BMS card attempts to bypass cells with.? And even 100ma of bypass current thru a tiny, long wire can cause millivolts of voltage drop which ruins the ability of the BMS to properly sense the voltage.? On an electric lift truck application I worked on, we found that 22 ga wires were inadvertently used instead of what we spec’d which was 20ga.? This difference caused cell balancing to be pretty ineffective.? Separate these functions (bypass and sense) and this problem goes away, however most of the BMS boards used until recently do not separate these.? Maybe yours does? ? Here details really matter. Cell balancing for our under 10kw boating applications should not require more than 1-2 amps of cell bypass current.? On my boat, I have 20 remote BMS cards.? Each has the capability of bypassing up to 12 series cell pairs at about 100ma of current from a 35ah pair of cells.? This results in about a 10mv/hour balance rate, which is plenty if your cells are not all out of whack and not daily charging and discharging the pack deeply for weeks at a time.? Here use-case is important. ? Your 250a Daly BMS makes me scratch my head---and the website for Daly doesn’t help me understand it any better.? Do you have better information on these?? Why on earth do they need to handle 250amps? ? Thanks. ? -MT (26’ The Reach Of Tide --- converted to electric in 2003) ?
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From: [email protected] [mailto:[email protected]] On Behalf Of aasmith970@...
Sent: Wednesday, May 3, 2023 2:54 AM
To: [email protected]
Subject: [electricboats] Splitting 48V System Into Two Boxes? ? I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..? I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
|
Just an FYI. Welding cable is not advised on a boat.? Its not tinned and has very fine strands which will corrode quicker. Some of it is not resistant to diesel fuel. Diesel can literally melt the insulation away. I assume you will not have any diesel on your boat, but still.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 3, 2023 at 01:19:42 PM EDT, Myles Twete <matwete@...> wrote:
First of all, you can certainly split up a pack into multiple boxes---this has been done since the first EVs were produced back in the late 1800’s.? I have no comment about aluminum except to be sure that’s what you really want (vs, say, wood/glass/epoxy molded to the hull).? With my 700ah, nom. 42v pack on , I have my pack split into 4 subpacks, each of the same nom. 42v (31v to 49v Lithium Ion).? Same story with Dan Pence’s “Ginger” (one of the first noted E-boat conversions in recent decades and 3rd earliest or so at evalbum.com --- Dan uses the same battery modules as I use and has a row of batteries on the starboard and one on the port side. ?He has his mounted in a ply/glass/epoxy cavity originally built and sized for lead-acid batteries back in the late 1990’s---the cavities fit these ex-THINK EV Enerdel stacks well. ?He and I both use 4ga wire from each 35ah stack thru fuses to common points on each side.? Then larger gauge cable to connect the starboard and port packs. ? Details matter. ?You indicate your pack will be 280ah at 48v and that the cells themselves are 280ah. ?Given that, your splitting of the pack results in two 280ah 24v packs in series.? Size your cables based on how much current you ever expect to draw from the pack.? Let’s say max. 7.5kw, then we’re talking about 150amps max. ?So sure, a gauge of 1, 1/0 or 0 probably would be fine.? Make sure you have a fuse near each of your 2 half-packs. ? As for BMS connections, it’s not really as simple as presented by Dave.? Yes, the cell connection wires are “sense” wires but they typically are also “bypass” wires---that is, they need to pass the current that your BMS card attempts to bypass cells with.? And even 100ma of bypass current thru a tiny, long wire can cause millivolts of voltage drop which ruins the ability of the BMS to properly sense the voltage.? On an electric lift truck application I worked on, we found that 22 ga wires were inadvertently used instead of what we spec’d which was 20ga.? This difference caused cell balancing to be pretty ineffective.? Separate these functions (bypass and sense) and this problem goes away, however most of the BMS boards used until recently do not separate these.? Maybe yours does? ? Here details really matter. Cell balancing for our under 10kw boating applications should not require more than 1-2 amps of cell bypass current.? On my boat, I have 20 remote BMS cards.? Each has the capability of bypassing up to 12 series cell pairs at about 100ma of current from a 35ah pair of cells.? This results in about a 10mv/hour balance rate, which is plenty if your cells are not all out of whack and not daily charging and discharging the pack deeply for weeks at a time.? Here use-case is important. ? Your 250a Daly BMS makes me scratch my head---and the website for Daly doesn’t help me understand it any better.? Do you have better information on these?? Why on earth do they need to handle 250amps? ? Thanks. ? -MT (26’ The Reach Of Tide --- converted to electric in 2003) ?
From: [email protected] [mailto:[email protected]] On Behalf Of aasmith970@...
Sent: Wednesday, May 3, 2023 2:54 AM
To: [email protected]
Subject: [electricboats] Splitting 48V System Into Two Boxes? ? I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..? I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
|
Nothing wrong with welding cable. I and many others have used it for many years without any issues.
Paul J. Thompson
Information Technology?Manager
Henry Brooks Co. (t/a Bathroom Direct)
M 64 21 275 5001(txt only please)?F?64 9 913 3113?
E?paul@...
PO Box 58031, Botany, New Zealand 2163
5 Smales Road, East Tamaki, Manukau City
? ?
The information in this email and any attachments is confidential.
This information may be subject to legal, professional, or other privilege.
It must not be disclosed to any person without our authority.
If you are not the intended recipient you are not authorised to and must
not disclose, copy, distribute, or retain this message or any part of it.
Please return this message to the sender immediately and delete any
and all copies from your system.On Thu, May 4, 2023 at 12:12?PM Matt Foley < matt@...> wrote: Just an FYI. Welding cable is not advised on a boat.? Its not tinned and has very fine strands which will corrode quicker. Some of it is not resistant to diesel fuel. Diesel can literally melt the insulation away. I assume you will not have any diesel on your boat, but still.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 3, 2023 at 01:19:42 PM EDT, Myles Twete < matwete@...> wrote:
First of all, you can certainly split up a pack into multiple boxes---this has been done since the first EVs were produced back in the late 1800’s.? I have no comment about aluminum except to be sure that’s what you really want (vs, say, wood/glass/epoxy molded to the hull).? With my 700ah, nom. 42v pack on , I have my pack split into 4 subpacks, each of the same nom. 42v (31v to 49v Lithium Ion).? Same story with Dan Pence’s “Ginger” (one of the first noted E-boat conversions in recent decades and 3rd earliest or so at --- Dan uses the same battery modules as I use and has a row of batteries on the starboard and one on the port side.? He has his mounted in a ply/glass/epoxy cavity originally built and sized for lead-acid batteries back in the late 1990’s---the cavities fit these ex-THINK EV Enerdel stacks well.? He and I both use 4ga wire from each 35ah stack thru fuses to common points on each side.? Then larger gauge cable to connect the starboard and port packs. ? Details matter.? You indicate your pack will be 280ah at 48v and that the cells themselves are 280ah.? Given that, your splitting of the pack results in two 280ah 24v packs in series.? Size your cables based on how much current you ever expect to draw from the pack.? Let’s say max. 7.5kw, then we’re talking about 150amps max.? So sure, a gauge of 1, 1/0 or 0 probably would be fine.? Make sure you have a fuse near each of your 2 half-packs. ? As for BMS connections, it’s not really as simple as presented by Dave.? Yes, the cell connection wires are “sense” wires but they typically are also “bypass” wires---that is, they need to pass the current that your BMS card attempts to bypass cells with.? And even 100ma of bypass current thru a tiny, long wire can cause millivolts of voltage drop which ruins the ability of the BMS to properly sense the voltage.? On an electric lift truck application I worked on, we found that 22 ga wires were inadvertently used instead of what we spec’d which was 20ga.? This difference caused cell balancing to be pretty ineffective.? Separate these functions (bypass and sense) and this problem goes away, however most of the BMS boards used until recently do not separate these.? Maybe yours does? ? Here details really matter. Cell balancing for our under 10kw boating applications should not require more than 1-2 amps of cell bypass current.? On my boat, I have 20 remote BMS cards.? Each has the capability of bypassing up to 12 series cell pairs at about 100ma of current from a 35ah pair of cells.? This results in about a 10mv/hour balance rate, which is plenty if your cells are not all out of whack and not daily charging and discharging the pack deeply for weeks at a time.? Here use-case is important. ? Your 250a Daly BMS makes me scratch my head---and the website for Daly doesn’t help me understand it any better.? Do you have better information on these?? Why on earth do they need to handle 250amps? ? Thanks. ? -MT (26’ The Reach Of Tide --- converted to electric in 2003) ? From: [email protected] [mailto:[email protected]] On Behalf Of aasmith970@...
Sent: Wednesday, May 3, 2023 2:54 AM
To: [email protected]
Subject: [electricboats] Splitting 48V System Into Two Boxes? ? I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..? I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
|
Go ahead and use it if you wish however its incorrect and dangerous to say "there is nothing wrong with it". Before marine cable was available boat builders used it. They do not anymore. It will not get passed a surveyor and you may not be able to insure your boat.??
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 3, 2023 at 08:29:06 PM EDT, Paul J. Thompson <bathroomdirectit@...> wrote:
Nothing wrong with welding cable. I and many others have used it for many years without any issues.
Paul J. Thompson
Information Technology?Manager
Henry Brooks Co. (t/a Bathroom Direct)
M 64 21 275 5001(txt only please)?F?64 9 913 3113?
E?paul@...
PO Box 58031, Botany, New Zealand 2163
5 Smales Road, East Tamaki, Manukau City
? ?
The information in this email and any attachments is confidential.
This information may be subject to legal, professional, or other privilege.
It must not be disclosed to any person without our authority.
If you are not the intended recipient you are not authorised to and must
not disclose, copy, distribute, or retain this message or any part of it.
Please return this message to the sender immediately and delete any
and all copies from your system.On Thu, May 4, 2023 at 12:12?PM Matt Foley < matt@...> wrote: Just an FYI. Welding cable is not advised on a boat.? Its not tinned and has very fine strands which will corrode quicker. Some of it is not resistant to diesel fuel. Diesel can literally melt the insulation away. I assume you will not have any diesel on your boat, but still.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 3, 2023 at 01:19:42 PM EDT, Myles Twete < matwete@...> wrote:
First of all, you can certainly split up a pack into multiple boxes---this has been done since the first EVs were produced back in the late 1800’s.? I have no comment about aluminum except to be sure that’s what you really want (vs, say, wood/glass/epoxy molded to the hull).? With my 700ah, nom. 42v pack on , I have my pack split into 4 subpacks, each of the same nom. 42v (31v to 49v Lithium Ion).? Same story with Dan Pence’s “Ginger” (one of the first noted E-boat conversions in recent decades and 3rd earliest or so at --- Dan uses the same battery modules as I use and has a row of batteries on the starboard and one on the port side.? He has his mounted in a ply/glass/epoxy cavity originally built and sized for lead-acid batteries back in the late 1990’s---the cavities fit these ex-THINK EV Enerdel stacks well.? He and I both use 4ga wire from each 35ah stack thru fuses to common points on each side.? Then larger gauge cable to connect the starboard and port packs. ? Details matter.? You indicate your pack will be 280ah at 48v and that the cells themselves are 280ah.? Given that, your splitting of the pack results in two 280ah 24v packs in series.? Size your cables based on how much current you ever expect to draw from the pack.? Let’s say max. 7.5kw, then we’re talking about 150amps max.? So sure, a gauge of 1, 1/0 or 0 probably would be fine.? Make sure you have a fuse near each of your 2 half-packs. ? As for BMS connections, it’s not really as simple as presented by Dave.? Yes, the cell connection wires are “sense” wires but they typically are also “bypass” wires---that is, they need to pass the current that your BMS card attempts to bypass cells with.? And even 100ma of bypass current thru a tiny, long wire can cause millivolts of voltage drop which ruins the ability of the BMS to properly sense the voltage.? On an electric lift truck application I worked on, we found that 22 ga wires were inadvertently used instead of what we spec’d which was 20ga.? This difference caused cell balancing to be pretty ineffective.? Separate these functions (bypass and sense) and this problem goes away, however most of the BMS boards used until recently do not separate these.? Maybe yours does? ? Here details really matter. Cell balancing for our under 10kw boating applications should not require more than 1-2 amps of cell bypass current.? On my boat, I have 20 remote BMS cards.? Each has the capability of bypassing up to 12 series cell pairs at about 100ma of current from a 35ah pair of cells.? This results in about a 10mv/hour balance rate, which is plenty if your cells are not all out of whack and not daily charging and discharging the pack deeply for weeks at a time.? Here use-case is important. ? Your 250a Daly BMS makes me scratch my head---and the website for Daly doesn’t help me understand it any better.? Do you have better information on these?? Why on earth do they need to handle 250amps? ? Thanks. ? -MT (26’ The Reach Of Tide --- converted to electric in 2003) ? From: [email protected] [mailto:[email protected]] On Behalf Of aasmith970@...
Sent: Wednesday, May 3, 2023 2:54 AM
To: [email protected]
Subject: [electricboats] Splitting 48V System Into Two Boxes? ? I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..? I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
|
Matt is of course 100% correct on the fineness of the welding cable strands being more susceptible to corrosion.? Finer strands _do_ lower the inductance though, which might be an advantage depending on your controller but...
In any case I go with Diesel Locomotive Cable for anything exposed to elements.? It's tinned, has finer strands than the standard stuff, and is about as rugged as you'll find without going to something exotic.? You should at least tin the _connections_ if you aren't using tinned cable.? I know you said properly crimped, but tinning afterwards goes a long way to combat the corrosion.? It always starts on the ends.? Shrink wrap too afterwards regardless.
I'm sceptical about the other fellows recommendation regarding the bypass for cell balance though.? You mentioned having eight wires for each bank, which I assumed was two for each 12V cell for charging and two for sense.? 16 total.? Double check in the charger's docs but it would be unusual if the charging was through one pair but the balance was through the sense wires.? The charging will be through the bigger wires.
Best of luck!? :-)
On Wednesday, May 3, 2023 at 07:12:15 PM CDT, Matt Foley <matt@...> wrote:
Just an FYI. Welding cable is not advised on a boat.? Its not tinned and has very fine strands which will corrode quicker. Some of it is not resistant to diesel fuel. Diesel can literally melt the insulation away. I assume you will not have any diesel on your boat, but still.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 3, 2023 at 01:19:42 PM EDT, Myles Twete <matwete@...> wrote:
First of all, you can certainly split up a pack into multiple boxes---this has been done since the first EVs were produced back in the late 1800’s.? I have no comment about aluminum except to be sure that’s what you really want (vs, say, wood/glass/epoxy molded to the hull).? With my 700ah, nom. 42v pack on , I have my pack split into 4 subpacks, each of the same nom. 42v (31v to 49v Lithium Ion).? Same story with Dan Pence’s “Ginger” (one of the first noted E-boat conversions in recent decades and 3rd earliest or so at evalbum.com --- Dan uses the same battery modules as I use and has a row of batteries on the starboard and one on the port side. ?He has his mounted in a ply/glass/epoxy cavity originally built and sized for lead-acid batteries back in the late 1990’s---the cavities fit these ex-THINK EV Enerdel stacks well. ?He and I both use 4ga wire from each 35ah stack thru fuses to common points on each side.? Then larger gauge cable to connect the starboard and port packs. ? Details matter. ?You indicate your pack will be 280ah at 48v and that the cells themselves are 280ah. ?Given that, your splitting of the pack results in two 280ah 24v packs in series.? Size your cables based on how much current you ever expect to draw from the pack.? Let’s say max. 7.5kw, then we’re talking about 150amps max. ?So sure, a gauge of 1, 1/0 or 0 probably would be fine.? Make sure you have a fuse near each of your 2 half-packs. ? As for BMS connections, it’s not really as simple as presented by Dave.? Yes, the cell connection wires are “sense” wires but they typically are also “bypass” wires---that is, they need to pass the current that your BMS card attempts to bypass cells with.? And even 100ma of bypass current thru a tiny, long wire can cause millivolts of voltage drop which ruins the ability of the BMS to properly sense the voltage.? On an electric lift truck application I worked on, we found that 22 ga wires were inadvertently used instead of what we spec’d which was 20ga.? This difference caused cell balancing to be pretty ineffective.? Separate these functions (bypass and sense) and this problem goes away, however most of the BMS boards used until recently do not separate these.? Maybe yours does? ? Here details really matter. Cell balancing for our under 10kw boating applications should not require more than 1-2 amps of cell bypass current.? On my boat, I have 20 remote BMS cards.? Each has the capability of bypassing up to 12 series cell pairs at about 100ma of current from a 35ah pair of cells.? This results in about a 10mv/hour balance rate, which is plenty if your cells are not all out of whack and not daily charging and discharging the pack deeply for weeks at a time.? Here use-case is important. ? Your 250a Daly BMS makes me scratch my head---and the website for Daly doesn’t help me understand it any better.? Do you have better information on these?? Why on earth do they need to handle 250amps? ? Thanks. ? -MT (26’ The Reach Of Tide --- converted to electric in 2003) ?
From: [email protected] [mailto:[email protected]] On Behalf Of aasmith970@...
Sent: Wednesday, May 3, 2023 2:54 AM
To: [email protected]
Subject: [electricboats] Splitting 48V System Into Two Boxes? ? I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..? I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
|
I want to say thanks to all of you for the depth of knowledge and the thought you all put into your responses.?
I will reply with some pics when I install over the next couple weeks.?
toggle quoted message
Show quoted text
On May 3, 2023, at 9:08 PM, Dave Yamakuchi via groups.io <dyamakuchi@...> wrote:
?
Matt is of course 100% correct on the fineness of the welding cable strands being more susceptible to corrosion.? Finer strands _do_ lower the inductance though, which might be an advantage depending on your controller but...
In any case I go with Diesel Locomotive Cable for anything exposed to elements.? It's tinned, has finer strands than the standard stuff, and is about as rugged as you'll find without going to something exotic.? You should at least tin the _connections_ if you aren't using tinned cable.? I know you said properly crimped, but tinning afterwards goes a long way to combat the corrosion.? It always starts on the ends.? Shrink wrap too afterwards regardless.
I'm sceptical about the other fellows recommendation regarding the bypass for cell balance though.? You mentioned having eight wires for each bank, which I assumed was two for each 12V cell for charging and two for sense.? 16 total.? Double check in the charger's docs but it would be unusual if the charging was through one pair but the balance was through the sense wires.? The charging will be through the bigger wires.
Best of luck!? :-)
On Wednesday, May 3, 2023 at 07:12:15 PM CDT, Matt Foley <matt@...> wrote:
Just an FYI. Welding cable is not advised on a boat.? Its not tinned and has very fine strands which will corrode quicker. Some of it is not resistant to diesel fuel. Diesel can literally melt the insulation away. I assume you will not have any diesel on your boat, but still.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Wednesday, May 3, 2023 at 01:19:42 PM EDT, Myles Twete <matwete@...> wrote:
First of all, you can certainly split up a pack into multiple boxes---this has been done since the first EVs were produced back in the late 1800’s.? I have no comment about aluminum except to be sure that’s what you really want (vs, say, wood/glass/epoxy molded to the hull).? With my 700ah, nom. 42v pack on , I have my pack split into 4 subpacks, each of the same nom. 42v (31v to 49v Lithium Ion).? Same story with Dan Pence’s “Ginger” (one of the first noted E-boat conversions in recent decades and 3rd earliest or so at evalbum.com --- Dan uses the same battery modules as I use and has a row of batteries on the starboard and one on the port side. ?He has his mounted in a ply/glass/epoxy cavity originally built and sized for lead-acid batteries back in the late 1990’s---the cavities fit these ex-THINK EV Enerdel stacks well. ?He and I both use 4ga wire from each 35ah stack thru fuses to common points on each side.? Then larger gauge cable to connect the starboard and port packs. ? Details matter. ?You indicate your pack will be 280ah at 48v and that the cells themselves are 280ah. ?Given that, your splitting of the pack results in two 280ah 24v packs in series.? Size your cables based on how much current you ever expect to draw from the pack.? Let’s say max. 7.5kw, then we’re talking about 150amps max. ?So sure, a gauge of 1, 1/0 or 0 probably would be fine.? Make sure you have a fuse near each of your 2 half-packs. ? As for BMS connections, it’s not really as simple as presented by Dave.? Yes, the cell connection wires are “sense” wires but they typically are also “bypass” wires---that is, they need to pass the current that your BMS card attempts to bypass cells with.? And even 100ma of bypass current thru a tiny, long wire can cause millivolts of voltage drop which ruins the ability of the BMS to properly sense the voltage.? On an electric lift truck application I worked on, we found that 22 ga wires were inadvertently used instead of what we spec’d which was 20ga.? This difference caused cell balancing to be pretty ineffective.? Separate these functions (bypass and sense) and this problem goes away, however most of the BMS boards used until recently do not separate these.? Maybe yours does? ? Here details really matter. Cell balancing for our under 10kw boating applications should not require more than 1-2 amps of cell bypass current.? On my boat, I have 20 remote BMS cards.? Each has the capability of bypassing up to 12 series cell pairs at about 100ma of current from a 35ah pair of cells.? This results in about a 10mv/hour balance rate, which is plenty if your cells are not all out of whack and not daily charging and discharging the pack deeply for weeks at a time.? Here use-case is important. ? Your 250a Daly BMS makes me scratch my head---and the website for Daly doesn’t help me understand it any better.? Do you have better information on these?? Why on earth do they need to handle 250amps? ? Thanks. ? -MT (26’ The Reach Of Tide --- converted to electric in 2003) ? From: [email protected] [mailto:[email protected]] On Behalf Of aasmith970@...
Sent: Wednesday, May 3, 2023 2:54 AM
To: [email protected]
Subject: [electricboats] Splitting 48V System Into Two Boxes? ? I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank..? I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars.?
Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?
280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor?
thanks for any and all comments.?
Aaron?
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