LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[ebaugh]

At 7000 cycles, 19 years as Terry mentioned one cycle per day, I would like to see some analysis of calendar aging. I think this will eventually be a hurdle for the battery engineers, perhaps become the limiting factor in cell life, especially in real life environmental conditions.

[I.Grind]

Like they say, if its too good to be true.....too bad I won't have these trucks for 19 years or I would report my findings. I thought you guys might like to check it out, always keep a watch on the horizon.

[T1 Terry]

They won't last that long in an EV, unless you figure out a way of not discharging them faster than a 0.5CA rate and not below 30% SOC, but there are a few on the EV forums that are on their 3rd yr with them, not sure if that is as a daily driver though. The guy who supplies our Winston cells here in Aust says he has around 3 yrs on his as a daily driver, but he has lost a few cells during that time. The loads on the cells in an EV are quite high, over 5CA at times, as house batteries they would never see loads like that.

T1 Terry

[gael]

Originally Posted by T1 Terry

They won't last that long in an EV, unless you figure out a way of not discharging them faster than a 0.5CA rate and not below 30% SOC, but there are a few on the EV forums that are on their 3rd yr with them, not sure if that is as a daily driver though. The guy who supplies our Winston cells here in Aust says he has around 3 yrs on his as a daily driver, but he has lost a few cells during that time. The loads on the cells in an EV are quite high, over 5CA at times, as house batteries they would never see loads like that.

T1 Terry

Hi ,
Runing dayly basis since 2009 with my CALB 130Ah.
Every couple of days I crank the watermaker so 0.25C for one hour.
Time to time climbing on the mast my 200pounds with the windlass
Never going below 20% discharge.
I do not see dramatic effect of the QOS.
cheers

[senormechanico]

Originally Posted by hellosailor

Steve, are you planning to use a BMS or balancing them manually?

I'll start by connecting them all in parallel for a week or so and using a small variable power supply to get them top balanced.
After connecting them all in series for 24 volts, I'll install a Clean Power BMS.

I'm very happy with the BMS on the 200 aH set on my boat.

BTW, we just returned from 5 weeks vacation in Desolation Sound.
The only failure on the boat in that whole time was the zipper pull on our sailcover.

Steve

[Maine Sail]

Originally Posted by senormechanico

BTW, we just returned from 5 weeks vacation in Desolation Sound.
The only failure on the boat in that whole time was the zipper pull on our sailcover.

Steve

Totally unacceptable failure... That zipper could have caused a chain reaction that clearly could have caused you to endanger people... Jeez what a slacker.....

[vturbo]

Hi guys, just joined up, and come across this thread.

I am hoping one of you could advise me on how i should proceed with a new LiFePo4 battery charging set up?

I would like to charge my Sinopoly LiFePo4's battery bank from my alternator as quick as i can. However, i am worried that i may end up frying them or the alternator or both?

I feel i should only charge them at 1C max but don't know quite how to achieve this without fancy Smart regs etc.

Ant advice/ideas would be much appreciated.

[Thumbs Up]

My engines have small, cheap auto type internal regulated alternators. It was suggested here somewhere that these type have temp sensor effects built into them to keep them from overheating. Has any body here tried charging them on internally regulated delco type alternators and how fast do they burn up? I don't have lithiums but would be more likely to get them if I didn't have to replace my charging system. I wonder what the smallest sized possible bank of lithiums would be that I could get away with and assuming I am going with deep charge cycles but still want a little safety margin.

[ebaugh]

Originally Posted by vturbo

Hi guys, just joined up, and come across this thread.

I am hoping one of you could advise me on how i should proceed with a new LiFePo4 battery charging set up?

I would like to charge my Sinopoly LiFePo4's battery bank from my alternator as quick as i can. However, i am worried that i may end up frying them or the alternator or both?

I feel i should only charge them at 1C max but don't know quite how to achieve this without fancy Smart regs etc.

Ant advice/ideas would be much appreciated.

The smallest deep cycle bank I've heard anyone using is 400Ah. I'd suggest you stick to .5C or less, for 400Ah, that's 200A. The only way to get that, or much of anything more than 100A is with an external regulator, with a temperature sensor connected to a large frame alternator.

I've had good luck with small Leese Neville/Prestolite alternators, but I have their built in regulator adjustment pot set at 13.25V, measured at the battery. I only get 40-45A from a 90A alternator that way, and no temperature issues. Other users have reported issues with stock alternators with completely fixed internal regulators overheating to self destruction. If they didn't self destruct, they would overcharge if you ran the engine too long.

I could probably get 70A or so, with a good external regulator. But I'm a powerboat that normally uses the genset and inverter chargers to reload the LFP bank.

To get the most of your alternator with LFP, the external regulator is pretty much a requirement.

[ebaugh]

Originally Posted by Thumbs Up

My engines have small, cheap auto type internal regulated alternators. It was suggested here somewhere that these type have temp sensor effects built into them to keep them from overheating. Has any body here tried charging them on internally regulated delco type alternators and how fast do they burn up? I don't have lithiums but would be more likely to get them if I didn't have to replace my charging system. I wonder what the smallest sized possible bank of lithiums would be that I could get away with and assuming I am going with deep charge cycles but still want a little safety margin.

I don't know which brand alternators have had problems overheating, but unless there is a voltage set point, something, ie. an external adjustable regulator, or the like needs to reduce charge when they fill up.

You have not provided near enough information to size a LFP bank. But I can give you my personal rule of thumb...at least 80% of the capacity of the lead acid bank that meets your needs.

[vturbo]

Thanks for the advice so far.

However, i am only using a small bank of LiFePo4, 100Ah to start with.

i will require an alternator to charge this bank at 1C target. I was planning to obtain an alternator rated at around 180Amps as to not overwork it.

The problem is how to protect the bank from overcharging and overheating etc. These batteries will take whatever amps they can get i guess.
I have been told an alternator is not the best way to charge LiFePo4 as they were never intended for that purpose. What other options are there?

I expect i will need an ext reg of some sort, but the regs i have found so far seem to only cater for lead acid and AGMs.

Any suggestions as to a non-expensive reg that will fully charge the Li's quickly without problem? I'm assuming there is no way i can just use the standard reg built into the alternator?

[senormechanico]

[QUOTE=ebaugh;1302539]The smallest deep cycle bank I've heard anyone using is 400Ah. I'd suggest you stick to .5C or less, for 400Ah, that's 200A.
/QUOTE]

I rely mostly on solar for my charging (in fact, it's all I really need), but my bank is only 200 aH. That's the whole enchilada. No separate start.
100 amp rated alternator with adjustable fixed voltage regulator set as low as it will go (14.3v). It rarely gets much use.

[durundal]

Originally Posted by vturbo

Thanks for the advice so far.

However, i am only using a small bank of LiFePo4, 100Ah to start with.

i will require an alternator to charge this bank at 1C target. I was planning to obtain an alternator rated at around 180Amps as to not overwork it.

The problem is how to protect the bank from overcharging and overheating etc. These batteries will take whatever amps they can get i guess.
I have been told an alternator is not the best way to charge LiFePo4 as they were never intended for that purpose. What other options are there?

I expect i will need an ext reg of some sort, but the regs i have found so far seem to only cater for lead acid and AGMs.

Any suggestions as to a non-expensive reg that will fully charge the Li's quickly without problem? I'm assuming there is no way i can just use the standard reg built into the alternator?

The lifepo is perfectly happy charging at a constant voltage to full, you don't need to try and maintain them charging at a constant current of 1C. As the voltage of the bank rises the voltage differential between charger and bank decreases, which drops the current going into the bank down. So long as the output of the alternator regulator is less than the max voltage of the bank you should be ok, it might not charge as quickly as something upping the charging voltage to maintain constant current, but its less complex and the slower charge rate only comes into being when the bank is starting to get topped off. A separate solar charging circuit could handily take care of the last 5-10% of capacity given time.

If your charging setup is incapable of exceeding the battery max voltage you are guaranteed to never overcharge, at the expense of trying to quickly charge the last 5-10% of capacity (below max battery voltage you will probably be current limited by your charging source, which wouldn't need to exceed max battery voltage to provide its max current). For the low voltage case you can add a low voltage cutoff that drives a contractor, once the voltage dips enough it opens the load circuit so charging sources can still charge but loads are shed to prevent overdischarge.

What alternator setup do you have already? Remember that a lower charge and discharge rates will improve battery longevity, if you don't need the 1C rate you could go longer on the same set of batteries.

Andy

[Lagoon4us]

Originally Posted by durundal

The lifepo is perfectly happy charging at a constant voltage to full, you don't need to try and maintain them charging at a constant current of 1C. As the voltage of the bank rises the voltage differential between charger and bank decreases, which drops the current going into the bank down. So long as the output of the alternator regulator is less than the max voltage of the bank you should be ok, it might not charge as quickly as something upping the charging voltage to maintain constant current, but its less complex and the slower charge rate only comes into being when the bank is starting to get topped off. A separate solar charging circuit could handily take care of the last 5-10% of capacity given time.

If your charging setup is incapable of exceeding the battery max voltage you are guaranteed to never overcharge, at the expense of trying to quickly charge the last 5-10% of capacity (below max battery voltage you will probably be current limited by your charging source, which wouldn't need to exceed max battery voltage to provide its max current). For the low voltage case you can add a low voltage cutoff that drives a contractor, once the voltage dips enough it opens the load circuit so charging sources can still charge but loads are shed to prevent overdischarge.

What alternator setup do you have already? Remember that a lower charge and discharge rates will improve battery longevity, if you don't need the 1C rate you could go longer on the same set of batteries.

Andy

Agree our 400amp cells are charging essentially from 750watts of solar through a GSL MPPT controller built for Lithium.

Our Dolphin charger handles the Lithium nicely.

Main engines alternator also tops up the Lithium without overcharging.

This without BMS.

Our cells were supplied 'ex-China' 5 weeks old and precisely charged to identical voltages.

Cells have not changed in behaviour.

Right this moment they are sitting on 13.1 volts and are at 80% charged.

The GSL Controller is set on 'long life' option.

Cells are sweet and system has been running for 3 months now.

Cheers.

[ebaugh]

I guess there are a few small banks! For 100Ah, solar is a great option if you have the space for that.

There is nothing wrong with using an alternator, the problem is the simple controllers. Balmar's 614 or ARS regulator will work with LFP since they have custom charging profiles. But so will many others.

But either way, the chargers need to charge to your target voltage of 14.0-14.4V, then stop charging by regulating at 13.6 or less. Held long enough, anything over 13.6, will overcharge.