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Re: Using online calculators - do they work?

 

I agree with Darin only in the respect that all those facets he listed are not currently being calculated and even if they were they will only get close to the reality?of the situation.? However, I think with some input from some learned people we could have something that can give us a calculation that gets really, really close.? Take resistance of boat X's hull.? If you have the number of hulls, length at the waterline of each, displacement and draft I think you can come up with a good measurement of resistance through the water and resistance to acceleration.? However, it won't be perfect because the shapes and state of the surface of the hulls make a difference.? But let's say you get as close an evaluation, based on descriptions like this that you can reasonably obtain, it would be a good start.? If trial found that the number generated for size and pitch was low by 10% based on performance numbers like we want to collect, maybe its' a good factor to adjust the calculation by to get the best approximation we can.? The question to me for the differences between the ice calculations and our motors is what does the even torque do for us.? In a car you can feel that difference in the acceleration.? There's no lag.? So does that only mean that the prop on our boats can be large so we can spin them quickly and get good acceleration?? Most of us don't really care much about that factor.? We, and I'm taking a small leap here, are interested in best efficiency at a reasonable speed in comparison with our fellow sailors out there.? IE I don't need to be able to run around at 15kt passing every snail boat around me.? But I also don't necessarily want to creep along at 3kts while every sail boat?around me passes me.? At least some number of us do outings with others and would like to keep up.? For those out on their own cruising the goal of 5kts is more to do with fighting currents and windage in certain circumstances.? But I think the reality is we want just enough to do what most ICE boats do now and keep using that amount of energy as long as possible.? If we propped our boats to do 15kts but we could only do it for 5 minutes with a ton of batteries we aren't interested.? But that is one of the values in the ICE calculator (what speed do you want to attain).? So does instant torque even help us more than a rabbit start from the dock?? Is it more efficient to spin a prop at 1000 rpm with a big prop or 2000 rpm with a small prop kw per mile?? And what is the right pitch for those? (big prop, small pitch, low rpm, or big prop, large pitch, low rpm, or big prop small pitch high rpm, etc)? The combinations should yield a power vs efficiency table that you could use in relation to the boat's resistance to get really close to ordering the right prop.?

Anyway, I think a calculator could be made really close if we can factor in the right elements of the equation.? It doesn't exist today so I went with my gut based on comments made here and what people are using.? I got a 15", 14 pitch folding prop for a 38' trimaran with a 3' draft and 9k lb displacement.? I just installed it a few weeks ago but still need to do some sea trials.? I'll share my data as soon as I get it.? BTW folding was a decision based on the incredibly high number of crab traps sprinkled around our local waters period.? I would have gone with fixed or if the wallet would allow, variable pitch if it were not for that issue.



On Tue, Jul 14, 2020 at 3:05 AM Darin <armyofpenguins@...> wrote:
Theo, good suggestion.? There have been some lengthy discussions about this topic in several forums, but the bottom line is this: You want to know what size motor to use for your specific application.? There's not really any good way to standardize that with a formula as there are so many factors such as prop diameter and pitch, gear reduction, water line length, beam, hull shape, etc, all factors which are part of the complex relationship between power and speed and which should be considered when choosing your motor.? In my case, I eliminated my transmission and installed a reduction gear, and changed my prop diameter and pitch.? All of these factors are different for each conversion and all affect each other.? There's some math for sure, but there's also a lot of educated guesses and experimentation necessary.? What I did was look for conversions of boats the same size as mine and try to learn from their successes and failures.? If you can, get them to share some data with you.? Ultimately, the most useful formula will be an empirical formula for how much power in kilowatts?it takes to get their?boat to a certain speed.? If you can develop that curve for their?conversion, and if your boat is a close?analog to theirs, you will then be able to select an appropriate combination of motor, nominal battery voltage, prop diameter and pitch, and gear reduction needed to move your boat efficiently and without burning up your motor or overdesigning (and overspending).? I've considered putting together a website where we can all submit our basic?info and data to?generate a power?curve.? Alas, the older I get, the more it's about time.? Cheers and welcome aboard!??

Darin

On Mon, Jul 13, 2020 at 8:54 PM Theo B <theo.brillhart@...> wrote:
Hi all - first time poster. I think I have some insights to the calculator question, but maybe not a totally straight forward answer.

What's missing in traditional calculators like VicProp is the torque that the electric motor brings to the party. The electric motor can supply almost constant torque across its RPM range and near full torque from the time you turn it on. So there's a mathematical relationship that predicts this power discrepancy and uncovers the false assumption that electric hp can be treated like ICE hp.

Mathematically, horsepower equals torque multiplied by rpm. Or, torque of one newton-meter, twisting a shaft at an angular speed of one radian per second, requires a power of one watt. So power is torque times angular speed (with no extra constants or conversions if you work everything in radians and SI units). So for the same angular velocity (RPM) the electric motor has all of its torque available starting at zero RPM, an ICE does not, and will not until the RPM gets sufficiently high. Thus the exaggerated discrepancies seen at slower speeds.

Given enough time and brain cells one could likely develop a compensation factor for typical ICE hp, but it would have to be non-linear due to the non-linear torque of the ICE. I've seen a 5:3 hp ratio tossed around in the electric car communities, but this does nothing to compensate for exaggerations at slower speeds. Might get you in the ballpark though.



--
Larry Brown
S/V Trident
Palm Harbor, FL
~~~~~~~~~~~~~~~~~_/)~~~~~~~~
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Re: Using online calculators - do they work?

 

Theo, good suggestion.? There have been some lengthy discussions about this topic in several forums, but the bottom line is this: You want to know what size motor to use for your specific application.? There's not really any good way to standardize that with a formula as there are so many factors such as prop diameter and pitch, gear reduction, water line length, beam, hull shape, etc, all factors which are part of the complex relationship between power and speed and which should be considered when choosing your motor.? In my case, I eliminated my transmission and installed a reduction gear, and changed my prop diameter and pitch.? All of these factors are different for each conversion and all affect each other.? There's some math for sure, but there's also a lot of educated guesses and experimentation necessary.? What I did was look for conversions of boats the same size as mine and try to learn from their successes and failures.? If you can, get them to share some data with you.? Ultimately, the most useful formula will be an empirical formula for how much power in kilowatts?it takes to get their?boat to a certain speed.? If you can develop that curve for their?conversion, and if your boat is a close?analog to theirs, you will then be able to select an appropriate combination of motor, nominal battery voltage, prop diameter and pitch, and gear reduction needed to move your boat efficiently and without burning up your motor or overdesigning (and overspending).? I've considered putting together a website where we can all submit our basic?info and data to?generate a power?curve.? Alas, the older I get, the more it's about time.? Cheers and welcome aboard!??

Darin

On Mon, Jul 13, 2020 at 8:54 PM Theo B <theo.brillhart@...> wrote:
Hi all - first time poster. I think I have some insights to the calculator question, but maybe not a totally straight forward answer.

What's missing in traditional calculators like VicProp is the torque that the electric motor brings to the party. The electric motor can supply almost constant torque across its RPM range and near full torque from the time you turn it on. So there's a mathematical relationship that predicts this power discrepancy and uncovers the false assumption that electric hp can be treated like ICE hp.

Mathematically, horsepower equals torque multiplied by rpm. Or, torque of one newton-meter, twisting a shaft at an angular speed of one radian per second, requires a power of one watt. So power is torque times angular speed (with no extra constants or conversions if you work everything in radians and SI units). So for the same angular velocity (RPM) the electric motor has all of its torque available starting at zero RPM, an ICE does not, and will not until the RPM gets sufficiently high. Thus the exaggerated discrepancies seen at slower speeds.

Given enough time and brain cells one could likely develop a compensation factor for typical ICE hp, but it would have to be non-linear due to the non-linear torque of the ICE. I've seen a 5:3 hp ratio tossed around in the electric car communities, but this does nothing to compensate for exaggerations at slower speeds. Might get you in the ballpark though.
Re: Using online calculators - do they work?

 

Hi all - first time poster. I think I have some insights to the calculator question, but maybe not a totally straight forward answer.

What's missing in traditional calculators like VicProp is the torque that the electric motor brings to the party. The electric motor can supply almost constant torque across its RPM range and near full torque from the time you turn it on. So there's a mathematical relationship that predicts this power discrepancy and uncovers the false assumption that electric hp can be treated like ICE hp.

Mathematically, horsepower equals torque multiplied by rpm. Or, torque of one newton-meter, twisting a shaft at an angular speed of one radian per second, requires a power of one watt. So power is torque times angular speed (with no extra constants or conversions if you work everything in radians and SI units). So for the same angular velocity (RPM) the electric motor has all of its torque available starting at zero RPM, an ICE does not, and will not until the RPM gets sufficiently high. Thus the exaggerated discrepancies seen at slower speeds.

Given enough time and brain cells one could likely develop a compensation factor for typical ICE hp, but it would have to be non-linear due to the non-linear torque of the ICE. I've seen a 5:3 hp ratio tossed around in the electric car communities, but this does nothing to compensate for exaggerations at slower speeds. Might get you in the ballpark though.
Re: Mounting the sevcon gen4?

 

I have a bulkhead just aft of the motor. I cut out a section to match the heat sink. I mounted the Sevcon on the forward facet of the bulhead with the heat sink penetrating into an open area over the shaft. Works like a champ.?
Re: Mounting the sevcon gen4?

 

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These were taken during the install. ?The backside where you can see the heat sync if you notice the nuts on the right side they are the bolts holding the chargers on the back side. ?They also have thermal grease between the aluminum plate and the aluminum stand.



On Jul 13, 2020, at 6:48 AM, Bob Jennings <heatnh@...> wrote:

?
Picture of my compartment

On Mon, Jul 13, 2020, 6:42 AM Bob Jennings via <heatnh=[email protected]> wrote:
I used the optional heat sink. It was short money when I purchased the 10kw kit. Not sure if it makes?a difference but the controller is mounted in the engine compartment so figured it couldn't hurt.

On Mon, Jul 13, 2020, 1:09 AM Ryan Sweet <ryan@...> wrote:
How have you folks mounted the sevcon controller? With the heat sinks on there doesn¡¯t seem to be a natural way to mount it. Do you put it on rods?? Or mount it with the heat sinks up against a panel?

Pictures anyone?

Thanks!


<20200506_131724.jpg>
Re: Mounting the sevcon gen4?

Bob Jennings
 

Picture of my compartment

On Mon, Jul 13, 2020, 6:42 AM Bob Jennings via <heatnh=[email protected]> wrote:
I used the optional heat sink. It was short money when I purchased the 10kw kit. Not sure if it makes?a difference but the controller is mounted in the engine compartment so figured it couldn't hurt.

On Mon, Jul 13, 2020, 1:09 AM Ryan Sweet <ryan@...> wrote:
How have you folks mounted the sevcon controller? With the heat sinks on there doesn¡¯t seem to be a natural way to mount it. Do you put it on rods?? Or mount it with the heat sinks up against a panel?

Pictures anyone?

Thanks!
Re: Mounting the sevcon gen4?

Bob Jennings
 

I used the optional heat sink. It was short money when I purchased the 10kw kit. Not sure if it makes?a difference but the controller is mounted in the engine compartment so figured it couldn't hurt.


On Mon, Jul 13, 2020, 1:09 AM Ryan Sweet <ryan@...> wrote:
How have you folks mounted the sevcon controller? With the heat sinks on there doesn¡¯t seem to be a natural way to mount it. Do you put it on rods?? Or mount it with the heat sinks up against a panel?

Pictures anyone?

Thanks!
Re: Mounting the sevcon gen4?

 

I should clarify that my gen4 is mounted on stainless steel sheet, which acts as a heatsink itself.? I've attached a sketch.? Hope this helps.?

Darin

On Mon, Jul 13, 2020, 2:15 AM Thierry <thierry.lequeu@...> wrote:
Dear Ryan,

The first question is whether the SEVCON GEN4 controller heats ...

A simple 6mm aluminium sheet can be used as a support and heatsink:?

With a heatsink slightly larger than the controller, it is possible to first attach the heatsink and then the controller to the heatsink:?
Caution: The heatsink fins must remain vertical in the direction of the natural air flow.

And when the motor mount is designed to accommodate the controller, it's easier!??

Thierry
Re: Mounting the sevcon gen4?

 

¿ªÔÆÌåÓý

I mounted the sevcon and 2 of the TS2500 chargers on a sheet of aluminum bent into a u shaped stand. ?I bolted the sevcon to the aluminum with the heat sync on the back side with thermal grease on each surface. ?Based on others' comments I get the impression this was overkill but I figured if I'm going to give it my best shot, why not. ?


On Jul 13, 2020, at 5:15 AM, Thierry <thierry.lequeu@...> wrote:

?Dear Ryan,

The first question is whether the SEVCON GEN4 controller heats ...

A simple 6mm aluminium sheet can be used as a support and heatsink:?

With a heatsink slightly larger than the controller, it is possible to first attach the heatsink and then the controller to the heatsink:?
Caution: The heatsink fins must remain vertical in the direction of the natural air flow.

And when the motor mount is designed to accommodate the controller, it's easier!??

Thierry
Re: Mounting the sevcon gen4?

 

Dear Ryan,

The first question is whether the SEVCON GEN4 controller heats ...

A simple 6mm aluminium sheet can be used as a support and heatsink:?

With a heatsink slightly larger than the controller, it is possible to first attach the heatsink and then the controller to the heatsink:?
Caution: The heatsink fins must remain vertical in the direction of the natural air flow.

And when the motor mount is designed to accommodate the controller, it's easier!??

Thierry
Re: Mounting the sevcon gen4?

 

Ditto I have been using a Gen 4 Sevcon without a Heat Sink for two years and overheating is not a problem. It will depend on the rating of your Sevcon, but heat dissipation?will be improved if your mount it to aluminum?plate with a large surface area. Forced air over the heat sink is also another option.


On Mon, Jul 13, 2020 at 4:16 PM Darin <armyofpenguins@...> wrote:
Ryan, I did not use a heat sink and haven't had any problems with it getting warm.? FWIW, I have a 37 ft sailboat with the same 10kW Thunderstruck kit I think I saw that you are using.? I typically run the motor around 30 to 60 amps, and have taken it up to 125 amps or above for 10 minutes or so without ever having an overheating problem with either the motor or the controller.??

Darin

On Sun, Jul 12, 2020 at 10:09 PM Ryan Sweet <ryan@...> wrote:
How have you folks mounted the sevcon controller? With the heat sinks on there doesn¡¯t seem to be a natural way to mount it. Do you put it on rods?? Or mount it with the heat sinks up against a panel?

Pictures anyone?

Thanks!




--
Kind regards Mick 0414 264 312
Re: Mounting the sevcon gen4?

 

Ryan, I did not use a heat sink and haven't had any problems with it getting warm.? FWIW, I have a 37 ft sailboat with the same 10kW Thunderstruck kit I think I saw that you are using.? I typically run the motor around 30 to 60 amps, and have taken it up to 125 amps or above for 10 minutes or so without ever having an overheating problem with either the motor or the controller.??

Darin

On Sun, Jul 12, 2020 at 10:09 PM Ryan Sweet <ryan@...> wrote:
How have you folks mounted the sevcon controller? With the heat sinks on there doesn¡¯t seem to be a natural way to mount it. Do you put it on rods?? Or mount it with the heat sinks up against a panel?

Pictures anyone?

Thanks!
Mounting the sevcon gen4?

 

How have you folks mounted the sevcon controller? With the heat sinks on there doesn¡¯t seem to be a natural way to mount it. Do you put it on rods? Or mount it with the heat sinks up against a panel?

Pictures anyone?

Thanks!
Re: Lake Test - 13' plywood runabout with Torqeedo 4R, and 50Ah eBike battery bank

 

Bill,

The boat was the "Playboy", designed by William Jackson, 1907-1973.

Plans are here:




Feel free to contact me off-list if you have any questions.

Here's my web page describing the construction:







On Monday, July 6, 2020, 06:38:44 PM CDT, Bill Feyerherm <feyerhw@...> wrote:


John?

a bit off topic, but I really like the looks of your test boat. ?Wonder if you can provide links to plans For the boat?
Bill

?
Re: Lake Test - 13' plywood runabout with Torqeedo 4R, and 50Ah eBike battery bank

 

John?
a bit off topic, but I really like the looks of your test boat. ?Wonder if you can provide links to plans For the boat?
Bill

?
Re: House systems - separate or together with drive system?

 

¿ªÔÆÌåÓý

?
Thank you everyone for all of the answers!

In the end I think I like the idea of having one set of inputs (shore power/solar) and two banks (house/drive system), and some way to use the house system as a backup.?

Either way I think the biggest challenge I¡¯ll have is cleaning up all of the apocryphal wiring from 50 years of lighting and equipment that has evolved over the lifetime of the craft.?

On Jun 25, 2020, at 5:06 AM, john via groups.io <oak_box@...> wrote:

Ryan,

How much house power do you need, and what is the relative balance of motor power vs. house power?

If the house requirements are tiny, then running a converter to regulate the 48V down to 12V may be a good answer.? On my small boat, this is what I have done - at least for now.

If your house requirements are large, then getting a sufficient regulator becomes more of an issue.

You might also consider how "critical" each supply is.? One reason house banks are kept separate from starting battery banks on many boats is to prevent the owner from accidentally running down the battery so far that he/she is no longer able to start the main engine.? ?In your case - would you want separation of the banks so that you didn't accidentally run down the power so much that you couldn't get home?

If you have a backup generator - then that is much less of a problem.

One other option is that if your house needs are small enough, you could consider a separate house bank - but keep it at 48V and use a regulator anyway.? That would allow you to have the house bank and the motor bank both at 48V, so that your house bank could be a "backup" for your motor, if anything bad happened to your main motor bank (i.e. if you ran it down unexpectedly).

Ultimately, it's a judgement call for you.? As with so many engineering problems - there are many answers.? Some less efficient, and often no single obvious perfect answer.

John

On Thursday, June 25, 2020, 12:46:09 AM CDT, Ryan Sweet <ryan@...> wrote:


Wow, I apologize for not editing for autocorrect typos. Hopefully the ones below make sense in context.

> On Jun 24, 2020, at 22:42, Ryan Sweet via groups.io <ryan=[email protected]> wrote:
>
> ?I am at the beginning of a conversion for a 32¡¯ ketch, and I have the 10kw thunderstruck kit, charger, reduction, and battery bank all working on my bench under artificial load. She will be at a dock soon where I can pull the diesel and begin refitting with the EV drive.
>
> The boat has an existing house system with four 6v golf cart batteries in 2p2s for both the 12v house loads and the starting motor, along with two 50w solar panels and a charge controller. During the summer in the Pacific NW the solar keeps up with the house loads at anchor all summer, she is usually at a dock plugged in for much of the winter.
>
> I originally intended to leave all the existing 12v system in place, and keep the 48v ev system separate, but I¡¯m realizing that once the old motor comes out, it¡¯s really prime time to simplify as many things as possible, so I¡¯m wondering about the necessary equipment and pros/cons of running the house load off of the same battery bank as the EV (right now I am working the EV with 4x 12v 200ah AGM in 4s).?
>
> What becomes complicated or inefficient about running them together (with a 48v to 12v step down) vs having separate systems?
>
> I halfway thought that I would try leaving the existing house system as-is, adding the EV with the AGM bank separately, and if it is all working well, then switching the EV drove to a m bank of lifepo4 and rewiring the AGM bank in 4p at 12v,? replacing the older system which is nearing end of life in the next few years anyway.? But I also am drawn to the simplicity of only having one set of batteries to worry about for all loads.
>
> What are the practical considerations that you guys have encountered for each scenario?
> My boat will mostly be used for crushing near shore, likely with power though most winters, and at anchor or underway in summers.
>
>



Re: House systems - separate or together with drive system?

 

¿ªÔÆÌåÓý

One of the best sites I have seen can give you a pretty good answer for LiFePo, for how much total capacity lost for each voltage cutoff. ?For example at 3.6 volt per cell will only cost you a max of 2%. ?That would be around 14.4 volts for a 12 volt equivalent, or 57.6 for 48 volt equivalent. ? You can run the math for other cut off points.?


?

On Jun 26, 2020, at 12:13 PM, john via groups.io <oak_box@...> wrote:

?
Myles,
I'm following what you're saying, and appreciate improving the life of the lithium battery by not fully charging it to the max allowed voltage.? But would you be giving up a significant portion of the battery capacity?

And I guess all of this depends on the exact details...

There was one "12V" Lithium battery I peeked at:


It's rated for a max charging voltage of 14.4V, with a standby voltage of 13.8V.
So I guess if your "48V to 12V" converter actually put out 13.5V (typical of many automotive systems),? then you'd probably be in pretty good shape.

If it only put out a true 12V, then your 50Ah battery (from above example) would never get close to being fully charged, and you'd get a significantly reduced fraction of the 50Ah life out of it before needing more charging.

Right?

John

On Friday, June 26, 2020, 11:03:56 AM CDT, Myles Twete <matwete@...> wrote:


There¡¯s another consideration here: the house battery ¡®type¡¯.

What Reuben says is correct if one is using PbA batteries for the house battery (12v or 24v or¡­).? Lead acid batteries need to be charged much higher than their nominal voltage rating and need to ramp the charge current down as that voltage gets near the end and then halt current (or possibly provide a trickle or maintenance charge after cooling down).

However, if instead of PbA batteries, you were using lithium for your house pack and that the lithium battery was rated, say, as a replacement for 12v (PbA) batteries.? Most of these are rated to 14.4v or so and there is no penalty at all in charging them only to 12v.? In fact, the lifetime of the batteries is improved by keeping the voltage lower, so¡­? And so, in the case of lithium batteries used as the house battery, you would not need (nor maybe would it be advisable) to use a 48vDC-12vDC charger unit (unless it were configurable for lithium) but simply use a 48/12v DCDC and you¡¯d be just fine.

?

From: [email protected] [mailto:[email protected]] On Behalf Of Reuben Trane via groups.io
Sent: Friday, June 26, 2020 7:37 AM
To: [email protected]
Subject: Re: [electricboats] House systems - separate or together with drive system?

?

A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually ¡°killed¡± the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can¡¯t handle the higher amp loads.?

Re: House systems - separate or together with drive system?

 

Myles,
I'm following what you're saying, and appreciate improving the life of the lithium battery by not fully charging it to the max allowed voltage.? But would you be giving up a significant portion of the battery capacity?

And I guess all of this depends on the exact details...

There was one "12V" Lithium battery I peeked at:


It's rated for a max charging voltage of 14.4V, with a standby voltage of 13.8V.
So I guess if your "48V to 12V" converter actually put out 13.5V (typical of many automotive systems),? then you'd probably be in pretty good shape.

If it only put out a true 12V, then your 50Ah battery (from above example) would never get close to being fully charged, and you'd get a significantly reduced fraction of the 50Ah life out of it before needing more charging.

Right?

John

On Friday, June 26, 2020, 11:03:56 AM CDT, Myles Twete <matwete@...> wrote:


There¡¯s another consideration here: the house battery ¡®type¡¯.

What Reuben says is correct if one is using PbA batteries for the house battery (12v or 24v or¡­).? Lead acid batteries need to be charged much higher than their nominal voltage rating and need to ramp the charge current down as that voltage gets near the end and then halt current (or possibly provide a trickle or maintenance charge after cooling down).

However, if instead of PbA batteries, you were using lithium for your house pack and that the lithium battery was rated, say, as a replacement for 12v (PbA) batteries.? Most of these are rated to 14.4v or so and there is no penalty at all in charging them only to 12v.? In fact, the lifetime of the batteries is improved by keeping the voltage lower, so¡­? And so, in the case of lithium batteries used as the house battery, you would not need (nor maybe would it be advisable) to use a 48vDC-12vDC charger unit (unless it were configurable for lithium) but simply use a 48/12v DCDC and you¡¯d be just fine.

?

From: [email protected] [mailto:[email protected]] On Behalf Of Reuben Trane via groups.io
Sent: Friday, June 26, 2020 7:37 AM
To: [email protected]
Subject: Re: [electricboats] House systems - separate or together with drive system?

?

A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually ¡°killed¡± the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can¡¯t handle the higher amp loads.?

Re: House systems - separate or together with drive system?

 

¿ªÔÆÌåÓý

There¡¯s another consideration here: the house battery ¡®type¡¯.

What Reuben says is correct if one is using PbA batteries for the house battery (12v or 24v or¡­).? Lead acid batteries need to be charged much higher than their nominal voltage rating and need to ramp the charge current down as that voltage gets near the end and then halt current (or possibly provide a trickle or maintenance charge after cooling down).

However, if instead of PbA batteries, you were using lithium for your house pack and that the lithium battery was rated, say, as a replacement for 12v (PbA) batteries.? Most of these are rated to 14.4v or so and there is no penalty at all in charging them only to 12v.? In fact, the lifetime of the batteries is improved by keeping the voltage lower, so¡­? And so, in the case of lithium batteries used as the house battery, you would not need (nor maybe would it be advisable) to use a 48vDC-12vDC charger unit (unless it were configurable for lithium) but simply use a 48/12v DCDC and you¡¯d be just fine.

?

From: [email protected] [mailto:[email protected]] On Behalf Of Reuben Trane via groups.io
Sent: Friday, June 26, 2020 7:37 AM
To: [email protected]
Subject: Re: [electricboats] House systems - separate or together with drive system?

?

A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually ¡°killed¡± the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can¡¯t handle the higher amp loads.?

Re: House systems - separate or together with drive system?

 

A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually ¡°killed¡± the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can¡¯t handle the higher amp loads.?
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