Re: [electricboats] BMS Recommendations

I have a a 16S 48V battery with 280AH cells (Eve).   They do have a 1C rating.  The highest load I have seen on testing is about 230A (making 6.8 knots). Typical operation is at 4 to 5.5 knots and less than 100 amps.  Occasionally I may have the need to punch through a wavy entrance for 3 to 5 minutes?  It's those situations that I might want max power.  That would be a bad time for the BMS to say "NO" and shut down output.  I generally like to size components with some headroom.   I was thinking 300amps capacity was about where I wanted to be.  Not sure about that.

Info on my battery build here:
http://dan.pfeiffer.net/10m/electric_drive_battery.htm

Thanks, Dan Pfeiffer

On 2025-06-01 2:28 am, Robert McArthur via groups.io wrote:

Dan,

I've got the JK inverter BMS going happily on a 16S 48V pack of 304Ah cells. It should handle your 280a which is only 1C - but not sure the size of your cells though. I must admit that I haven't tried it on a motor for real. I've had the bms running for 6-9 months without worry so far. Offgridgarage YT has done various tests on it. 

 

R

On Sun, 1 June 2025, 12:03 pm Dan Pfeiffer via groups.io, <dan=pfeiffer.net@groups.io> wrote:

I may need a new BMS for my 16S 48V LiFePo4 battery that I built in 2021.  Looking for recommendations.  I am running a 12kW motor and max current is on the order of 280 amps. 

I have the Thunderstruck BMS (Dilthium Design) and it seems to have failed.  I can't get it to see more than 10 cells and voltage readings are incorrect compared to my meter (Fluke) directly on the batteries or on the harness end plug using the breakout board supplied with the BMS for testing.  My connections on the harness all seem fine.  I have tried to reset the BMS from the computer using the USB interface.  No luck.  I suspect there is something wrong with the BMS itself. 

This Thunderstruck BMS does balancing and charge controlling but does not control input and output for the battery.  That's fine but it means I can only use a charger that the BMS can tell to shut down.  So there is some advantage to a BMS with input output control?  It can disconnect charging without needing to have communications with the charger.  That seems useful?  

So I am looking to see what others have done in this sort of installation. 

Thanks, Dan Pfeiffer
My Electric Drive Sailboat
http://dan.pfeiffer.net/10m/electric_drive.htm

Re: [electricboats] BMS Recommendations

Dan,

I've got the JK inverter BMS going happily on a 16S 48V pack of 304Ah cells. It should handle your 280a which is only 1C - but not sure the size of your cells though. I must admit that I haven't tried it on a motor for real. I've had the bms running for 6-9 months without worry so far. Offgridgarage YT has done various tests on it. 

R

On Sun, 1 June 2025, 12:03 pm Dan Pfeiffer via groups.io, <dan=pfeiffer.net@groups.io> wrote:

I may need a new BMS for my 16S 48V LiFePo4 battery that I built in 2021.  Looking for recommendations.  I am running a 12kW motor and max current is on the order of 280 amps. 

I have the Thunderstruck BMS (Dilthium Design) and it seems to have failed.  I can't get it to see more than 10 cells and voltage readings are incorrect compared to my meter (Fluke) directly on the batteries or on the harness end plug using the breakout board supplied with the BMS for testing.  My connections on the harness all seem fine.  I have tried to reset the BMS from the computer using the USB interface.  No luck.  I suspect there is something wrong with the BMS itself. 

This Thunderstruck BMS does balancing and charge controlling but does not control input and output for the battery.  That's fine but it means I can only use a charger that the BMS can tell to shut down.  So there is some advantage to a BMS with input output control?  It can disconnect charging without needing to have communications with the charger.  That seems useful?  

So I am looking to see what others have done in this sort of installation. 

Thanks, Dan Pfeiffer
My Electric Drive Sailboat
http://dan.pfeiffer.net/10m/electric_drive.htm

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[electricboats] BMS Recommendations

I may need a new BMS for my 16S 48V LiFePo4 battery that I built in 2021.  Looking for recommendations.  I am running a 12kW motor and max current is on the order of 280 amps. 

I have the Thunderstruck BMS (Dilthium Design) and it seems to have failed.  I can't get it to see more than 10 cells and voltage readings are incorrect compared to my meter (Fluke) directly on the batteries or on the harness end plug using the breakout board supplied with the BMS for testing.  My connections on the harness all seem fine.  I have tried to reset the BMS from the computer using the USB interface.  No luck.  I suspect there is something wrong with the BMS itself. 

This Thunderstruck BMS does balancing and charge controlling but does not control input and output for the battery.  That's fine but it means I can only use a charger that the BMS can tell to shut down.  So there is some advantage to a BMS with input output control?  It can disconnect charging without needing to have communications with the charger.  That seems useful?  

So I am looking to see what others have done in this sort of installation. 

Thanks, Dan Pfeiffer
My Electric Drive Sailboat
http://dan.pfeiffer.net/10m/electric_drive.htm

Re: [electricboats] Battery Recommendations

This is interesting information. I also have a couple of epropulsion motors and had not seen this information about storage. 

Too bad that the epropulsion forum is hosted on a social media platform. 

I wonder if the sudden drop you see is from it going into sleep mode, so that you can't read the actual voltage? The Activator manual says it will not activate a battery in sleep mode. I don't have an activator so I can't verify what you are seeing. 

Reading the activator manual, there seems to be some odd things:

They say after 10 days it will self discharge to 60%, but then they say it will discharge to 75% after 20 days? 

I use very little of the total capacity. I have never been below 80%. So how do I get it to the preferred 60%? Run the motor for a several hours? If it automatically self discharges to 60% after 10 days then why would I need to pre- discharge it? 

One thing that irks me about the battery, especially if the discharge level is so important, is why the battery has no indicator of charge state? As it is I have to hook it up to the motor and controller to see the state. Or buy the Activator I guess. 

And how do I charge it to 60%? I'd have to babysit the charger and periodically unhook the charger and hook up my motor and controller (or activator) to see charge state?

If charge state is so important then why don't they have a smarter charger that can keep the battery at the proper level? I imagine most use cases include long periods of storage. 

All that being said, I do like the motor. I am amazed at how long the battery can run. 

-Steve

On May 29, 2025, at 11:45 PM, Walter Pearson via groups.io <pearson1854=comcast.net@groups.io> wrote:



Thanks for comments on ePropulsion and GrenerPower batteries. The Spirit Plus battery is only specified as Lithium Ion Polymer. The BMS may be working well in that it senses a problem cell, but could it also be that it failed to provide the cell balancing function which would produce that problem cell? There is no communication between users and ePropulsion; the dealers are our only option and finding a responsive one is elusive. I joined the ePropulsion group on Facebook and did see posts from others experiencing sudden shutdowns, but the group is moderated by ePropulsion sales and marketing, so technical help is scarce. The only dealer I have found that would address the shut-down issue claims there can be three possibilities - corrosion at connections, failed BMS, or cell failure. Corrosion is not likely, but narrowing down between BMS and cell(s) requires shipping and testing and confirmation videos, etc., - not something I want to do – nor pay to have done. An excerpt from the manual regarding storage and self-discharge:

 

Before long time storage, ensure the battery charge level is 60% around, store the battery in 15°C ~ 25°C (59°F ~ 77°F) ambient temperature. 

If the battery level is larger than 60% for more than ten days without activity, the battery itself will discharge with a small current around 100mA until it reaches the 60% battery level.

• Battery will actively discharge to 75% after 20 days without charging or discharging.

• If battery level is low for a long time, it will enter sleep mode. Charge to wake it up.

• During long time storage, activate the battery every 3 months by a charge condition and keep the battery charge level at 60% around. This activation is very important and it can help to keep the battery in good condition.

• After long time storage, fully charge the battery before use.

 

From my self-discharge data, there is evidence that the mentioned 100mA load is applied which increases the self-discharge rate for a short period. It does not quite reach the 60% level before continuing at a lower rate. It's the sudden drop I don't like. I plan to test with bollard pull soon to determine whether this occurs under load and, if so, whether shutdowns repeatedly occur at the same charge level.

 

<RexGDDPxcjM0G7HG.png>

 

I previously used the term sudden loss of charge (SLoC), but from subsequent charging, it appears that the battery does not suddenly lose 40% of its charge. It just becomes unavailable due to shutting down. See charge plot:

 

<4EqioggODdPJkvHm.png>

Note that I have the Spirit 1.0 Evo Remote which has a permanently fixed remote throttle and display panel. When the battery is removed from the boat, there is no integral charge level indication. I purchased the ePropulsion Battery Activator that displays charge level. I now have a grid charger and solar controller for nominal 48V LiFePO4, so might try the GrenerPower battery again and hope for one at normal shipping charge condition.

[electricboats] Battery Recommendations

Thanks for comments on ePropulsion and GrenerPower batteries. The Spirit Plus battery is only specified as Lithium Ion Polymer. The BMS may be working well in that it senses a problem cell, but could it also be that it failed to provide the cell balancing function which would produce that problem cell? There is no communication between users and ePropulsion; the dealers are our only option and finding a responsive one is elusive. I joined the ePropulsion group on Facebook and did see posts from others experiencing sudden shutdowns, but the group is moderated by ePropulsion sales and marketing, so technical help is scarce. The only dealer I have found that would address the shut-down issue claims there can be three possibilities - corrosion at connections, failed BMS, or cell failure. Corrosion is not likely, but narrowing down between BMS and cell(s) requires shipping and testing and confirmation videos, etc., - not something I want to do – nor pay to have done. An excerpt from the manual regarding storage and self-discharge:

 

Before long time storage, ensure the battery charge level is 60% around, store the battery in 15°C ~ 25°C (59°F ~ 77°F) ambient temperature. 

If the battery level is larger than 60% for more than ten days without activity, the battery itself will discharge with a small current around 100mA until it reaches the 60% battery level.

• Battery will actively discharge to 75% after 20 days without charging or discharging.

• If battery level is low for a long time, it will enter sleep mode. Charge to wake it up.

• During long time storage, activate the battery every 3 months by a charge condition and keep the battery charge level at 60% around. This activation is very important and it can help to keep the battery in good condition.

• After long time storage, fully charge the battery before use.

 

From my self-discharge data, there is evidence that the mentioned 100mA load is applied which increases the self-discharge rate for a short period. It does not quite reach the 60% level before continuing at a lower rate. It's the sudden drop I don't like. I plan to test with bollard pull soon to determine whether this occurs under load and, if so, whether shutdowns repeatedly occur at the same charge level.

 

 

I previously used the term sudden loss of charge (SLoC), but from subsequent charging, it appears that the battery does not suddenly lose 40% of its charge. It just becomes unavailable due to shutting down. See charge plot:

 

Note that I have the Spirit 1.0 Evo Remote which has a permanently fixed remote throttle and display panel. When the battery is removed from the boat, there is no integral charge level indication. I purchased the ePropulsion Battery Activator that displays charge level. I now have a grid charger and solar controller for nominal 48V LiFePO4, so might try the GrenerPower battery again and hope for one at normal shipping charge condition.

Re: [electricboats] Battery Recommendations

[Edited Message Follows]

Ok then, "self discharging" disconnect at around 40% means that your BMS is working fantastic, better than most. I am surprised that the epropulsion people didn't tell you as much.

Lithium batteries will completely not work again if you drain them down to zero volts. It is recommended to store lithium batteries long term at around 50%. So having a BMS that disconnects at around 40% could very well be a battery saver. To store them over the winter you need to charge them a little every month or get a programable charger that you can set to turn on at 45% and turn off at 55%. Since batteries "wear out" more on the top and bottom of the charge, this "middle charging" will have the least degrading effect on the batteries.

This is especially helpful with a battery that only has 500 cycles. This tells me that it is not a LFP (LiFePO4) battery but some kind of Lithium, maybe LMC (Lithium Manganese Cobalt), because the lowest cycle count I have ever seen on a LFP was 1000.

It being something like a LMC battery tells me that it is most likely a 12S battery when they call it a 48V and will need a 50.4V charger for a 12S lithium battery.

The GrenePower 51.2V, 32Ah LiFePO4 that I found on amazon is a LFP battery and will need a 58.4V charger for a 16S LFP battery. If you have a programable charger then you can charge either one of them to whatever you want.

Most LFP batteries that are called 48V are this 16S (16 cells in series) and output their power at mostly 51.2 Volts, but you have to be careful, I have seen some 15S LFP batteries. These 15S LFP batteries would put out most of their power at 48Volts which would be fine for your electronics but would need a special charger (limited at 54.7V) because if you used a standard 58.4V charger on one it would kill the batteries.

 

Being that weight is your primary concern, your best bet might be to stick with the Greenpower 32Ah, if you can get one that works.

 

The Greenpower looks like it uses the cylindrical cells in a 16S, 8P configuration. Couple reasons I personally don't like cylindrical cells is there is a lot of empty space between them, so they are less power dense for their size. Another is that for every P more than 1, the battery is that many more times likely to fail, for example an 8P battery is 7 times more likely to fail than a 1P battery.

But I don't know of any LFP batteries that small that don't use the cylindrical cells. I think all the LFP batteries that are less than 100Ah use them, so it might be your only option. 

You might be able to find an even lighter battery that uses LMC chemistry (or more Ah for same weight) but they will be more expensive, and they can catch fire.

 

So again, your best option may be the Greenpower (or similar).

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Re: [electricboats] Battery Recommendations

Ok then, "self discharging" disconnect at around 40% means that your BMS is working fantastic, better than most. I am surprised that the epropulsion people didn't tell you as much.

Lithium batteries will completely not work again if you drain them down to zero volts. It is recommended to store lithium batteries long term at around 50%. So having a BMS that disconnects at around 40% could very well be a battery saver. To store them over the winter you need to charge them a little every month or get a programable charger that you can set to turn on at 45% and turn off at 50%. Since batteries "wear out" more on the top and bottom of the charge, this "middle charging" will have the least degrading effect on the batteries.

This is especially helpful with a battery that only has 500 cycles. This tells me that it is not a LFP (LiFePO4) battery but some kind of Lithium, maybe LMC (Lithium Manganese Cobalt), because the lowest cycle count I have ever seen on a LFP was 1000.

It being something like a LMC battery tells me that it is most likely a 12S battery when they call it a 48V and will need a 50.4V charger for a 12S lithium battery.

The GrenePower 51.2V, 32Ah LiFePO4 that I found on amazon is a LFP battery and will need a 58.4V charger for a 16S LFP battery. If you have a programable charger then you can charge either one of them to whatever you want.

 

Being that weight is your primary concern, your best bet might be to stick with the Greenpower 32Ah.

 

The Greenpower looks like it uses the cylindrical cells in a 16S, 8P configuration. Couple reasons I don't like cylindrical cells is there is a lot of empty space between them, so they are less power dense for their size. Another is that for every P more than 1, the battery is that many more times likely to fail, for example an 8P battery is 7 times more likely to fail than a 1P battery. I don't know of any LFP batteries that small that don't use the cylindrical cells. I think all the LFP batteries that are less than 100Ah use them.