question

Jodel avatar image

MPPT 75/10 not charging

Hi, I have a 100 watt flex solar panel on my boat connected to a MPPT 75/10 . The system is less than a year old and was working fine. Now it is no longer charging. I am not sure if it is the panel or the controller. The open circuit voltage on the panel is 18.6. When I connect the panel to the controller it's voltage drops to 16.5. The battery voltage is 13.5. there is a mains charger connected also, but this has never effect things before.

VE direct shows voltage but no amps from the solar panel and battery state as off.

Any suggestions as to how I can fault find the issue?

Jodel

charging batterySolar PanelMK3
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1 Answer
Matthias Lange avatar image

PV voltage has to be 5V higher than battery voltage to start charging. After that it has to be 2V higher.

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Thanks. I'll switch off mains charger to get battery voltage to drop.

Just wondering why it has to be 5 volts higher to start. Can this value be changed?


No, it can't be changed. It's the way this MPPT works.

I switched off my mains charger this morning and when the differential reached 5 volts the solar kicked in.

I have a 12 volt 45watt compressor driven fridge running full time so it should be drawing approx 4 amps.

It midday here in full sunshine and the max the panel produced all morning was P max. 9 W. It has now stopped charging again. I thought it might go into float mode

The battery voltage is 12.77.

I would have expected the panel to be producing the 4 amps that the fridge is consuming.

Is my panel suspect?