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drowdad asked

Smart solar 75/15 not charging adequately

I have a camper trailer with a couple of LED strips plus a fridge. I have been running an AGM battery using a 200w solar panel and a cheap PMW controller for a few years with no problems until a couple of weeks ago when the battery would just not hold it’s charge. I guessed it was time for a new battery.
I now have a new 12v 140 amp hour AGM deep cycle battery. I also bought a SmartSolar 75/15 Victron controller. At the start of my trip the battery was showing around 13.4v using a multimeter and a digital cigar lighter meter - I always measure using 2 different devices, just to be sure. The trailer had been plugged into the mains for a couple of days since I installed it just before setting out.

A few days later, after being in unpowered camp sites, I noticed that my voltage was down to 11.9 - 12.3 even though the battery had been charged during daylight hours by the 200w solar panel. The Victron smartphone app tells me it is getting 19.9v from the solar panel and pushing out 13.2v to the battery. I have confirmed both those readings with my multimeter. But the battery itself never gets to the level it reaches when I recharge it through the mains - something I’ve never experienced with my old set-up.

Why is my batter charge so low. Who does it it get to 13.4v?

I don’t know what settings the controller needs to have to do a proper charging job. Any help would be appreciated.

Thanks

David

MPPT Controllers
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2 Answers
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drowdad answered ·

Please close this post – the resolution is shown in the reply above

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rgrver answered ·

If you have the Victron app your phone, connect to the MPPT and tap HISTORY near the top. You'll then see the battery min/max for each day. I have the same MPPT.

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drowdad avatar image drowdad commented ·

Thanks for your reply, but the problem turned out to be a very bad connection in the 15cm length of cable from the MPPT controller to the Anderson plug that then connects to the battery. So bad that no current was getting through to the battery at all!

The tip off was the ZERO value items that the app showed in its Status display

Solar: 0W

Voltage: 20.74V

Current: 0.0A

Battery Voltage: 13.73V

Battery Current: 0.00A

Battery State: Float

We found an article / blog post that said the Zero values for current and solar suggested a circuit with no continuity – that is a blown fuse, a switch in the off position or some other break in the circuit.

We then tested every part of circuit for continuity and found the culprit and fixed it by applying some solder. The battery is now happily charging with the Watt and Amp readings being non zero.

The Battery voltage value in the app also started to match what my multimeter was reporting. The MPPT device had constantly reported that my battery was at 13.37v which was exactly the same as as the target Float Voltage in the settings section. That seems to be what the app says when it is not connected to a battery. Arguably it should show 0v or an error. Had it done so, I may have located there problem much sooner.

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