question

jokees avatar image
jokees asked

PWM float voltage below LiFePO4 battery voltage

When in the dark (no solar charging), the voltage of my LiFePO4 battery drops below the float voltage of the PWM only when the battery is drained to around 55%.
This means that the PWM does not start loading (blinking charging arrow on the display) during the day until my battery is around half full.

Ofcourse I would like the PWM to start loading earlier.
The LiFePO4 battery type setting (b04) of the PWM has a float voltage of 13.35 V.
The battery specifications: 13.5V float voltage (14.2…14.6V load voltage and 11-13.5V operational voltage).

Question:
Can I safely set the battery type to b02 (LEAD-ACID [Gel]) which has a float voltage of 13.7V and the same absorbtion voltage?
Or has this other unwanted implications?

Configuration:
- 12V 80W solar panel
- BlueSolar PWM Charge Controller–LCD-USB
- LiFePO4 battery with BMS


battery system voltagesmart solar charging behaviourfloatBlueSolar PWM
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Alexandra avatar image Alexandra ♦ commented ·

@jokees

In theory no, as there is temperature compensation in the GEL profile.

Which pwm controller do you have?

At float that will be ok, but at absorption may go high enough to trigger battery protection.

Although it does not sound like you have enough solar to charge your battery at all.

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3 Answers
jokees avatar image
jokees answered ·

Hi Alexandra, Thank you for your answer.
I have the Victron BlueSolar PWM 12/24V-10A LCD&USB.
On a sunny day the solar panel can adequately fill the battery. Often I first have to reset the PWM to make it start a new loading sequence, due to the problem described above.

So, there is no solution for this as I understand.

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madmaxx answered ·

How did you determine the 55% figure?

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jokees answered ·

The 55% comes simply from following the voltage and remaining capacity on the app of the battery management system (BMS). The values fluctuate a bit, but somewere between 50 and 60 % the voltage comes around 13.3 volt.

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