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eyacht avatar image
eyacht asked

MPPT not charging but Victron Connect says it is

Hi everyone - I have an odd situation that I hope someone can shed some light on. I have an MPPT 75/10 that has my 48V propulsion bank connected as PV in and the battery out goes to my starter battery. There is no load connected. In the Victron Connect app, everything looks great - battery voltage is 13.4V and it's in float. I just went to turn on the generator and got no power at the panel. Having checked the breakers I took a voltmeter to the starter battery and it's completely dead - 3.5V. I have no idea how the app can read healthy voltage and the battery is pretty much dead. Any thoughts? Thank you in advance.

EDIT 10 Aug 23 - I followed advice and measured voltage from MPPT + to battery - and from MPPT - to battery +. The first was 2.4V and the other 10.3V so there is an issue somewhere with the positive wire from the MPPT. I suspect a dodgy fuse holder. Thanks everyone for your input and advice.

battery chargingMPPT SmartSolarAGM Battery
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2 Answers
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wkirby answered ·

If the MPPT reads 13.4V and the battery its self reads a different Voltage then that means that the battery is not connected to the MPPT for some reason, perhaps a wiring fault or a blown fuse or open circuit breaker.

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eyacht avatar image eyacht commented ·
The wiring is pretty straight-forward as described above .. but why would a blown fuse or open circuit breaker cause the MPPT to read 13.4V? If the breaker or fuse to the battery has gone, wouldn't it read zero?
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seb71 avatar image seb71 eyacht commented ·
The MPPT would output voltage at its battery terminal if it has voltage at PV terminals from a PV array, even if not connected to a battery at battery terminals.


But you should not connect PV without a battery on battery terminals.
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eyacht avatar image eyacht seb71 commented ·
Really? I thought it would read the battery voltage. So you're saying the reading in the app (and at the MPPT battery output terminals) is the "produced" voltage and not the actual voltage at the battery?
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seb71 answered ·

I have an MPPT 75/10 that has my 48V propulsion bank connected as PV in and the battery out goes to my starter battery.

Do not use a battery as PV input for any MPPT.

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eyacht avatar image eyacht commented ·
Why not? Input voltage is input voltage; panel or battery doesn't matter.
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