Charging lithium batteries

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removalizer asked Mar 27, '24

Charging lithium batteries

Hi

I have 2 x 100 ah Lithium batteries on my sailboat

My MPPT 100/50 SOLAR charger will not charge them as the SOC depletes it is always in float mode however it will charge if there is a heavy load such as water maker etc, same happens with my wind charger and alternator. The batteries have been to a low charge state and I have to keep using my Victron IP22 to top up the batteries. Both the solar controller and IP22 are set to Lifepo4

I have a Victron 500 smart shunt

Charged voltage 14.6v

Discharge floor 20%

Tail current 3%

Charged detection time 3m

Peukert exponent 1.05

Charge eff 99%

Current threshold 0.1A

Time to go average period 3m

Any ideas ?

smart lithium

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Answer 1 · 2024-03-27T12:12:03Z

Alexandra answered · Mar 27 at 12:12 PM

@Removalizer

I have some ideas but need to know more about your system.

Do you have a GX? Is is purely a DC system?

If not what is the rebulk offset on the MPPT itself? Did you use the lithium profile and adapt it to your battery needs.

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removalizer commented · Mar 27 at 01:44 PM

Thanks for the reply, the rebulk offset is 0.4

The absorption rate is 14.4

Float is 13.8

It is purely a dc system I don’t know what GX is

yes I use Lithium profile on all devices

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Alexandra ♦ removalizer commented · Mar 27 at 01:55 PM

Ok. That's great. I just wanted to know if there was another control system in place.

I would set the rebulk off set to 0.1v the charger will then maintain float or rebulk so will continue to produce rather an drop so far below float. It works better with lithium anyway.

And your charge detection voltage? Is that above float or set at absorption?

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Answer 2 · 2024-03-28T06:12:32Z

removalizer answered · Mar 28 at 06:12 AM

Adjusted the rebulk offset to 0.1 and its improved

Not sure what you mean about charged detection voltage ? The charged voltage section shows absorption at 14.2 and float at 13.5

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pwfarnell commented · Mar 28 at 07:09 AM

You listed the charged voltage as 14.6V in your table above, you need to set that to 14.0V, 0.2V below absorption voltage. Some people call it the charged detection voltage but the proper name is just charged voltage.

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klim8skeptic ♦ commented · Mar 28 at 06:33 AM

@Removalizer post the settings from the SmartShunt.

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Answer 3 · 2024-03-28T08:07:06Z

removalizer answered · Mar 28 at 08:07 AM

Attached image

img-4348.png (244.4 KiB)

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Answer 4 · 2024-03-28T08:07:49Z

removalizer answered · Mar 28 at 08:07 AM

attached image

img-4347.png (204.2 KiB)

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klim8skeptic ♦ commented · Mar 28 at 11:10 AM

@Removalizer you have 0.8v difference between the mppt's battery terminals and the SmartShunt.

That sort of voltage difference needs to be investigated and remedied.

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Alexandra ♦ klim8skeptic ♦ commented · Mar 29 at 10:41 AM

@Removalizer

@klim8skeptic is right on with the observation.

This is definitely a big part of the issue. That voltage difference is quite something.

You can try the ve smart network, might help. But the root cause (maybe undersized cabling or a long run or high resistance connection). Either way 0.2v can be accepted but not 0.8v

The mppt already things the battery is charged then so no production makes sense now.

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Answer 5 · 2024-03-28T11:45:18Z

removalizer answered · Mar 28 at 11:45 AM

Ok thanks for all the input, I have been watching off grid garage on you tube, he had the same problem, he dropped the solar absorption to 13.45 and float at 13.4, saved it then switched off the charger for an hour, restarted it, I did the same and it worked, it’s belting out 10 amps into the batteries now

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Answer 6 · 2024-03-28T12:40:48Z

removalizer answered · Mar 28 at 12:40 PM

Well that didn’t last long in bulk, it’s now back in absorption at 0.1 amp with 66% charge, back to the drawing board then

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kevgermany ♦♦ commented · Mar 29 at 04:59 AM

What are the recommended charge parameters for your batteries? Default lithium settings often need changing depending on the battery/BMS maker.

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Answer 7 · 2024-03-29T03:37:38Z

onrbikes answered · Mar 29 at 03:37 AM

Not sure if this helps. I have an easy solar with a smart shunt.

Lifepo4 8 x 3.2v cells 200ah, with a Daly BMS.

I've only had these batteries a week so this is very new to me. I've had lead acid before this and am fluent with getting around the settings.

My shunt is set at 28.8v (14.4v)

Discharge floor is 30%.

Inverteris as follows

Absorption is set at 28.4v (14.2v)

Float 27.5v

All your other numbers are identical.

My understanding is the lower the discharge floor the more you can discharge. Do by increasing the discharge floor charge should come in earlier.

Altering the float on the inverter allows more to go in.

This may not be of use to you but My Daly BMS decides when the batterues have had enough and shuts the voltage down.

My victron is just in there but don't think I really need it.

But I'm just learning

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