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Erratic solar charging and battery voltage


My partner and I are travelling on our Renault Trafic with a fairly basic solar system set up as follows:

190w mono-crystalline solar panel

Victron energy 75/15 MPPT

100ah Platinum Leisure AGM Plus battery

This powers a number of things in our van, including a Dometic CRX50 fridge, USB chargers, LED lights and diesel heater. The fridge is the only load item that’s always switched on and kicks in as and when it thinks necessary

This has all been fine for light use for months but we’re now travelling properly and have had a couple of things raise eyebrows and cause concern. We’ve been stationery at a campsite for the past few days and the solar has been doing well from the sunshine in southern England recently.

While we were in bed the night before last, our carbon monoxide alarm suddenly sounded and showed a reading of 263PPM We weren’t burning anything at all and there were no flames. The fridge might have been going but I couldn’t say for sure. Near to the alarm was my mobile phone plugged into our CTEK CS Free to charge. We couldn’t determine a source for the CO, but obviously aired out the van immediately first anyway. After this, we watched the CO alarm drop to zero in one go. Without being able to identify the source, we started considering if it could be battery related.

We’ve noticed that the victron app has showed us the battery voltage dipping quite low during the day (usually at the fridge kicks in) and then it recovers soon after. This has been happening frequently, however the day after the alarm went off (yesterday) the app shows irregular behaviour and fluctuation in our battery voltage and solar watts, as below:


The CO alarm has remained silent since it went off, so could it be a one-off false alarm? Or is it set off by the battery venting/gassing (same thing, right?) excess hydrogen? In which case, that could be a major concern..? Or is it something else we just don’t know about or understand but hopefully someone here will be able to help with?

I appreciate there might be loads more information you need to answer this, so please do let me know if you need more details. We’re grateful for any help you can give. We’re in the van full time at the moment so it’s really important to us that we get it sorted out or at least put our minds at rest.

I should also mention that I contacted the company we bought the battery from (purchased in January last year) and they told us that we might be overcharging it by having it on the wrong profile, and they advised me to change it to AGM Spiral which I have since done. They also pointed me to a page where I can buy vent pipes for the battery, though I always thought those were unnecessary for the type of battery we have.

Thanks again for any help you can give.

smart solar charging behaviour
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