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removalizer avatar image
removalizer asked

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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7 Answers
Alexandra avatar image
Alexandra answered ·

@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 avatar image removalizer commented ·

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 avatar image Alexandra ♦ removalizer commented ·

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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removalizer avatar image
removalizer answered ·

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 avatar image pwfarnell commented ·
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 avatar image klim8skeptic ♦ commented ·
@Removalizer post the settings from the SmartShunt.
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removalizer avatar image
removalizer answered ·

img-4348.png

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removalizer avatar image
removalizer answered ·

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klim8skeptic avatar image klim8skeptic ♦ commented ·
@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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removalizer avatar image
removalizer answered ·

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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removalizer avatar image
removalizer answered ·

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 avatar image kevgermany ♦♦ commented ·
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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onrbikes avatar image
onrbikes answered ·

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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