Lifepo4 upgrade?

[Phil_Fr17]

Same remark as sailingharry, try it as commercial action !


Thanks for the link, I appreciate, it seems to be a correct product. And for Paul, it seems this product can work at low temperature (-20℃ to 35℃)... ;-)


Question mark about the fact this is an internal BMS (rated at 200A MAX), but no information on the web site about consumption of this BMS (in case of parking your boat for a long time).

[Chotu]

Originally Posted by Phil_Fr17

Same remark as sailingharry, try it as commercial action !


Thanks for the link, I appreciate, it seems to be a correct product. And for Paul, it seems this product can work at low temperature (-20℃ to 35℃)... ;-)


Question mark about the fact this is an internal BMS (rated at 200A MAX), but no information on the web site about consumption of this BMS (in case of parking your boat for a long time).

I did not look at the BMS parasitic load because I have 1400 watts solar feeding it. The batteries will not be left a long time without charging. If I did have to do that, I would simply remove them from the circuit. That is the best way they tell you to store them.

[Phil_Fr17]

I was reading Will Prowse's videos on these batteries and he says the BMS's are very basic, and to me the diameter of the cables (inside) are a little small. The cells are 'generic', look like EVEs . To be monitored over the long term and according to your use.

[Chotu]

Originally Posted by Phil_Fr17

I was reading Will Prowse's videos on these batteries and he says the BMS's are very basic, and to me the diameter of the cables (inside) are a little small. The cells are 'generic', look like EVEs . To be monitored over the long term and according to your use.

Yes. They are basic batteries.

I currently have 220 amp hours of usable battery in the form of flooded lead acid golf cart batteries. Trojan T105.

I do not have a use for 400 useable amp hours of batteries at this time. They are oversized. But they were so lightweight, that I ordered more than I needed.

I have a low power consumption boat, other than the electric refrigerator/freezer.

My refrigerator uses 48 AH a day.

The chest freezer uses something like 80 AH a day, I think. The freezer by itself ran fine from solar with the 220 AH FLA batteries all last year.

Any other loads I have are minor. 15A maximum load from the autopilot is next biggest.

I will not be trying to pull 400A to test the BMS and I will not have high loads like induction cooking or air conditioning.

Generators run air conditioning and are available for battery charging.

[Chotu]

The last post I made reminded me I have to upgrade my battery charger. Question about that.

The charger puts out 14.7 V on the book charge. 13.6 on the float.

I think this is to accommodate a slight voltage drop of .1 V.

Is that reasonable?

The batteries call for 14.6 V bulk charging.

However, the documentation says it senses the voltage of the batteries, and cuts them off at 14.6.

[fxykty]

Originally Posted by Chotu

The last post I made reminded me I have to upgrade my battery charger. Question about that.

The charger puts out 14.7 V on the book charge. 13.6 on the float.

I think this is to accommodate a slight voltage drop of .1 V.

Is that reasonable?

The batteries call for 14.6 V bulk charging.

However, the documentation says it senses the voltage of the batteries, and cuts them off at 14.6.

Those are very high voltages for LFP battery longevity and I suspect are specified as such by manufacturers to be compatible with existing LA charging regimes. But if your LFP battery manufacturer says it’s OK then fine.

End of charging should be a combination of voltage and tail amps - 2.5% of C, eg 14.6V and 10A for your 400Ah capacity.

Are you able to lower the float voltage? 13.6V is still a charging voltage that will keep your battery near 100% SOC, while with LFP the float voltage should be such that the SOC is around 50% - 13.2V or so.

Do note that when your charger stops bulk/absorption charging it should not go into float unless you have float set to ~13.2V so that the SOC immediately starts reducing from 100%.

[Chotu]

Originally Posted by fxykty

Those are very high voltages for LFP battery longevity and I suspect are specified as such by manufacturers to be compatible with existing LA charging regimes. But if your LFP battery manufacturer says it’s OK then fine.

End of charging should be a combination of voltage and tail amps - 2.5% of C, eg 14.6V and 10A for your 400Ah capacity.

Are you able to lower the float voltage? 13.6V is still a charging voltage that will keep your battery near 100% SOC, while with LFP the float voltage should be such that the SOC is around 50% - 13.2V or so.

Do note that when your charger stops bulk/absorption charging it should not go into float unless you have float set to ~13.2V so that the SOC immediately starts reducing from 100%.

OK. That’s good advice. Thank you. My battery charger is kind of an interesting little unit. You buy separate little controllers for it. Physical controllers that you plug into it to get different charging parameters. I use it almost never. It will be only used when solar doesn’t keep up. That could actually be never.

So I have normal outback MPPT charge controllers with completely variable charging parameters. I can set anything to anything. So I will make sure to follow both the voltage and current requirements and advice you gave above.

[fxykty]

Originally Posted by Chotu

OK. That’s good advice. Thank you. My battery charger is kind of an interesting little unit. You buy separate little controllers for it. Physical controllers that you plug into it to get different charging parameters. I use it almost never. It will be only used when solar doesn’t keep up. That could actually be never.



So I have normal outback MPPT charge controllers with completely variable charging parameters. I can set anything to anything. So I will make sure to follow both the voltage and current requirements and advice you gave above.

For your regular charging, especially if easily adjusted in your controllers, I would also suggest more conservative charging voltages for bulk and absorption. Give away a little bit of capacity for greater longevity. 13.8V is a generally accepted conservative charge voltage for LFP. Again, specify the tail amps 2.5% C to ensure charging stops.

Restart charging when SOC falls to at least 60%, or lower in decent solar conditions. LFP batteries love being within 40-60% SOC.

[Chotu]

Yep. My new Trojan t105 lead acid bank was destroyed through lack of care.

I was doing some microwaving today at 6C and they couldn’t keep the voltage up to the cutoff voltage of the inverter. The batteries were at 100% SOC too.

They even had 700 watts of solar giving a boost on a bright sunny day and still voltage dropped.

It was kind of strange behavior.

It was a cycling. Once every second or so, the voltage would drop, then recover, then drop, then recover. I assume this was the solar charge controller helping out, then backing off for some reason.

Things got done on my boat but my list of destroyed items (including batteries, a hatch, the entire deck, unchecked rainwater ingress, insect infestations, scratched exterior finish paint) is huge.

Makes me wonder about boat sitting. You’d really need to find someone with a verifiable track record of caring for boats.

[RaymondR]

Originally Posted by Chotu

Yep. My new Trojan t105 lead acid bank was destroyed through lack of care.

I was doing some microwaving today at 6C and they couldn’t keep the voltage up to the cutoff voltage of the inverter. The batteries were at 100% SOC too.

They even had 700 watts of solar giving a boost on a bright sunny day and still voltage dropped.

It was kind of strange behavior.

It was a cycling. Once every second or so, the voltage would drop, then recover, then drop, then recover. I assume this was the solar charge controller helping out, then backing off for some reason.

Things got done on my boat but my list of destroyed items (including batteries, a hatch, the entire deck, unchecked rainwater ingress, insect infestations, scratched exterior finish paint) is huge.

Makes me wonder about boat sitting. You’d really need to find someone with a verifiable track record of caring for boats.

Sulphation.

One of things which used to be done to de-sulphate them was to drain the electrolyte, refill them with distilled water and put them on a trickle charger for a month or so to bring the voltage back to fully charged. After a couple of cycles of this they would be refilled with fresh acid and put back into service. Worth trying if you stack your boat for the winter.

[Chotu]

Originally Posted by RaymondR

Sulphation.

One of things which used to be done to de-sulphate them was to drain the electrolyte, refill them with distilled water and put them on a trickle charger for a month or so to bring the voltage back to fully charged. After a couple of cycles of this they would be refilled with fresh acid and put back into service. Worth trying if you stack your boat for the winter.

Some sulfation. But also the fact that they were allowed to run completely empty and dry. So only half the plates are working anyway.

But it makes no difference I’m just complaining. I already bought the lithium bank.

I don’t have time to change them yet. I have to get to the Rigger.

[Chotu]

Great. I didn’t realize the extent at which he damaged the batteries. Here is the data. They are unusable.

440AH bank (starting from 100% full SOC), but only showing 12.1V when down 75AH at night (solar is only charging source)

So roughly 3/4 of the capacity of the batteries was ruined.

I was awakened by the inverter low voltage alarm.

Batteries completely destroyed.

Now I have to definitely install the lifepo4 bank before I leave in 2 days (along with a LOT of other stuff).

Question:. Can I install one of them, use it for a month, then install the other? I know that would be a no for FLA batteries. But I'm not sure I have the space to install both lifepo4 batteries in the current configuration without redoing the entire electrical system and all battery box connections and stuff. It's on the list but no way I can do that before going to the rigger.

[RaymondR]

Can't see that it would cause a problem, cycling one more than the other for 30 days with batteries which are good for 3,000 odd cycles is only about a 1% difference over the lifetime.

[Chotu]

Originally Posted by RaymondR

Can't see that it would cause a problem, cycling one more than the other for 30 days with batteries which are good for 3,000 odd cycles is only about a 1% difference over the lifetime.

Thank you!

I was thinking the same, but I didn’t know what I didn’t know here. Brand new to these types of batteries and I have never even read about them.

installing just one will allow me to do it quickly, just changing the charge parameters on my solar charge controllers.

and of course I should change the charge parameters on my generator powered charger also.

The battery manual gives a charging voltage of 14.1V for these batteries I bought. I am guessing the BMS takes this higher voltage and manages it correctly to charge the cells properly.

I'll give it a finishing voltage of 13.2 or something. Essentially switching off the BMS for charging at finish.

Sound about right for the finishing voltage?

Also, my new batteries will be full a lot. I know. Bad.

So if I finish my charging at 13.2, turning off the BMS for charging, will the solar controllers pick up the high loads when I turn them on? Things such as microwaving? Power tools? Shop vac?
Will these run off solar during the day leaving my batteries topped off to be used at night like I had been doing with the FLA batteries?


Note:. It may have been 14.6. I'll double check that today before installing. Going off memory and my memory cup runneth over. Too many details right now.

[RaymondR]

I'm pretty well in the same boat myself having only started the demystifying process about two years ago and not progressed very far.

One of the things I am finding baffling myself is the allowable charge current, designated as C which appears to generally be between 0.5 and 1.0 of the amp hour capacity.
but is generally stated without any voltage limitation.

This raises the question of why one should observe voltage limitations whilst recharging since the BMS is supposed to prevent overcharging and over discharging. Is it that there might be a damaging heat buildup or is it that one should not entirely trust the BMS to remove the charging source and that limiting the charge voltage will ensure that excessive overcharging will not occur because the rising battery back voltage will prevent over charging if the charge source output voltage is set low enough to allow this mechanism to come into play.