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assi avatar image
assi asked

MPPT 100/30 showing absorption to early

We have 2x 315w panels feeding into a MPPT 100/30 controller. The controller feeds various components of a CCTV which pulls about 3.5amps and also feeds into 2 x 200ah lithium batteries. What has been happening is that during a sunny day sometimes even though the battery level is at 40% the battery voltage will exceed the set battery voltage of 14.2 sometimes up to 14.3 and go into absorbtion. This throttles the charging back and results in the batteries not charging

if we put the battery on a meter it only reads around 13.1 so for some reason the solar charger is pushing the voltage up too high causing it to go into absorption when battery voltage is actually quite low. I thought the controller would manage this

Is it simply a case of raising the voltage in the settings to say 14.6 to stop it going into absorption and continuing to fully charge. Apologies as just learning

MPPT Controllers
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ingo21 avatar image ingo21 commented ·

What kind of batteries do you have? brand , diy ??

is there a BMS ( BatteryManagementSystem ) installed?

i would not raise the charge voltage with lithium batteries that can destroy them.

your solarcharger could be to small too

2x 315w panels = 630Watt / 13V = 48amps

the mppt 100/30 controller is good for 30amps which is 440watt



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klim8skeptic answered ·

@ASSI if we put the battery on a meter it only reads around 13.1 so for some reason the solar charger is pushing the voltage up too high causing it to go into absorption when battery voltage is actually quite low.

Sounds like you have a bad case of voltage drop between the mppt and battery.

Long thin cables? Poor connections? Dodgy fusing or bad circuit breaker?

Could also be the battery BMS disconnecting charge.

945w of panels is enough for a 70a mppt. Check your sums.

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