200a Portable Lifepo + BMS + Balancing

[rgleason]

Engine is 30hp. Have 65a very old balmar with replacement non oem stator. Planned on getting a new 120a balmar and using the ARS or 614 regulator belt program to drop it's output to 80-90a, but that was for charging FLA.

[newhaul]

Originally Posted by rgleason

Engine is 30hp. Have 65a very old balmar with replacement non oem stator. Planned on getting a new 120a balmar and using the ARS or 614 regulator belt program to drop it's output to 80-90a, but that was for charging FLA.

the 120 would work just fine.
With it you would recharge your daily needs in less than an hour.
( don't know your ah usage but likely below 75ah. )

[john61ct]

Originally Posted by rgleason

So ventilation under the seat would not be a big issue?

None IMO. But measure, fix if it becomes so.

> 100amps. Would we need to be concerned about heat when charging?
Only the cell temp, assuming robust wiring.

> Would it be 150amp but dropped to 100 or 120 by belt load manager

Fine, or triple that

[john61ct]

Originally Posted by rgleason

Engine is 30hp.

if you go to 200A that's over third of your power, make sure to put in a field current kill switch

[john61ct]

So LFP will accept whatever you can put out, is the bottom line

[newhaul]

Originally Posted by john61ct

So LFP will accept whatever you can put out, is the bottom line

Yep and that leads into the small dc generator thread. 300 amp at 12 volts would be really nice for most lfp installs.

[tanglewood]

Originally Posted by john61ct

So LFP will accept whatever you can put out, is the bottom line

I don't think it's that simple. The batteries may accept it, but it can be damaging.


As best I recall the research papers, voltage differentials develop in the cell during charge, and are of course proportional to the charge current. If one of the internal voltages exceeds a certain limit, in addition to the desired electro-chemical reaction taking place, electro-plating starts to occur on the SEI layer that is permanent and irreversible. That electro-plating reduces cell capacity.


I haven't seen it stated anywhere, but I expect this is the reason why LFP cell specs state 1C as the max charge rate, and recommend "normal" charging in the 0.25C to 0.3C range; It's to keep the internal voltage drops below the electro-plating threshold.


That said, Newhaul, you mentioned that your cells can take a 5C charge rate? Any chance you can share the spec sheet for those cells? That's a real diversion from what I've read so far.


Cell heating is the other consideration. For kicks I just ran the numbers for my CALB cells. They have an internal resistance of 0.6 milli-ohms. At 1C charge rate, that generates 20W of internal heat in the cells. I didn't expect it to be that high at all, but it certainly explains why EVs often have elaborate battery cooling systems. Take that charge rate down to 0.5C and the internal heating drops to less than 5W.

[rgleason]

All very good points and new information to me. Thank you.
Our needs cruising and anchoring are about 80ah and at sea underway 140ah. The 120a alt belt program limited to 80a or 90a would cover the cruise load in an hour. It might be a good idea to get a 140ah alternator so that it could recharge the sea load more quickly (a long hour) if cut back to 120a max with the belt load program reset.
But I should be careful of the electroplating issue and not charge too fast. Not over.0.3C. This appears to be the only reason I have found so far to have a bigger bank.

I'd rather use a smaller cheaper bank and closer to its full practical capacity and recharge more frequently with alt or small solar while on the mooring.

The sea use is less frequent, if I were to charge at say .4C or .45C what would be the result, reduction in capacity or reduction in number of cycles?

[tanglewood]

Originally Posted by rgleason

All very good points and new information to me. Thank you.
Our needs cruising and anchoring are about 80ah and at sea underway 140ah. The 120a alt belt program limited to 80a or 90a would cover the cruise load in an hour. It might be a good idea to get a 140ah alternator so that it could recharge the sea load more quickly (a long hour) if cut back to 120a max with the belt load program reset.
But I should be careful of the electroplating issue and not charge too fast. Not over.0.3C. This appears to be the only reason I have found so far to have a bigger bank.

I'd rather use a smaller cheaper bank and closer to its full practical capacity and recharge more frequently with alt or small solar while on the mooring.

The sea use is less frequent, if I were to charge at say .4C or .45C what would be the result, reduction in capacity or reduction in number of cycles?

The manufacturers I've looked at say you can charge up to 1C, and lots of the research projects do just that. I haven't seen anything that shows objectively what the effects are of slower charging on life, etc. Only that for whatever reason the same manfacturer's talk about "normal" charging at lower rates. It's anybody's guess what's actually behind those statements.



The obvious impact of faster charging vs slower is heating, so the faster you charge, the more important it will be to monitor temp and slow down charging if necessary. There is lots of research showing the negative effects of heat, and explaining exactly what goes astray in the battery's chemistry.

[newhaul]

Originally Posted by tanglewood

That said, Newhaul, you mentioned that your cells can take a 5C charge rate? Any chance you can share the spec sheet for those cells? That's a real diversion from what I've read so far.

.

no problem I will attach a screenshot of the spec sheet.
These cells are from the camel battery company.
( the company that makes the cells for Nissan )

[rgleason]

So, I may need to leave some room for a small computer fan mounted in the old drawer front area with similar area for exhaust, with t'stat activation.
In any event the drawer front should be redesigned allow free air flow.

Do these batteries ever leak acid or anything? I don't think so. So there is not any real need for a full container. Just strap them in well, sideways and tied down.
Is this correct?

[tanglewood]

Originally Posted by newhaul

no problem I will attach a screenshot of the spec sheet.
These cells are from the camel battery company.
( the company that makes the cells for Nissan )

Thanks. Interesting and confusing at the same time.


They say "normal" charge/discharge of 0.5C, but then have 45A in parentheses. 0.5C on a 25Ah battery is 12.5A, not 45A. So I'm confused.


And yes, 5C is a really big charge current compared to others I have seen. Maybe they have some magic in their cell construction.

[newhaul]

Originally Posted by tanglewood

Thanks. Interesting and confusing at the same time.


They say "normal" charge/discharge of 0.5C, but then have 45A in parentheses. 0.5C on a 25Ah battery is 12.5A, not 45A. So I'm confused.


And yes, 5C is a really big charge current compared to others I have seen. Maybe they have some magic in their cell construction.

only thing I can think of as to the 5C fast charge would be for the ev application with a short burst charge.
The spec sheet for their 100ah cells reads the same just changed the battery capacity entry . So the .5C listing 45amp is likely a clerical error.
However once my bank is built and installed I will never even get the .5C charge point.
(100 ah 4p4s with 400 watts solar ) so charge would be more in the .25C )

[tanglewood]

Originally Posted by newhaul

only thing I can think of as to the 5C fast charge would be for the ev application with a short burst charge.

The spec sheet for their 100ah cells reads the same just changed the battery capacity entry . So the .5C listing 45amp is likely a clerical error.

However once my bank is built and installed I will never even get the .5C charge point.

(100 ah 4p4s with 400 watts solar ) so charge would be more in the .25C )

Sounds like you will be in good shape. I think it’s pretty hard to even get to 1C of charging capacity, let alone more.

[john61ct]

Originally Posted by newhaul

300 amp at 12 volts would be really nice for most lfp installs.

All depends on bank size.

Originally Posted by tanglewood

I don't think it's that simple. The batteries may accept it, but it can be damaging.

I just meant for the size ranges OP was talking about.

If you have BMS circuitry between the cells and the charge source that will limit you.

Otherwise even well over 1C is no issue with robust wiring.

Temp protection on the bank would let you go much higher.

> internal voltages exceeds a certain limit

good voltage regulation, in my case 13.8V, is assumed, and OVD protection even if only bank level should be enough

AGM makers often spec a max charge rate way below what is perfectly safe with temp protection.

I think it's just legal CYA BS, since so many setups don't have robust wiring infrastructure.

EV charging is at much higher rates than 1C, day in day out.

House bank usage this really is just not a concern in 99.9% of cases. Not many setups have say only a 100AH bank but charge sources offering 300A.