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captainslow avatar image
captainslow asked

MPPT 75/15 reset itself to 24V and destroyed my battery?

Hi forum,

I've got a Victron MPPT 75/15 (and other Victron elements) on my camper and it's been working fine for two years or more. It's connected to a 120Ah 12V AGM battery.

A few days ago, while preparing to take the camper away, I noticed...

screenshot-2024-06-24-202433.png

Suddenly the MPPT controller was pushing 30V+ to the battery, and had been for the past couple of days, despite, as shown in the graph above, working fine beforehand.

Checking the settings in the app, the controller had set itself to 24V. Setting it back to 12V put the voltage back in the correct range but it was too late and the battery is cooked and won't hold charge.

I hadn't touched the app (or the camper for that matter, it was sat on my driveway and I was at work that day) the day the voltage changed, nobody else has the app installed for this installation, and the Bluetooth PIN is not the default one.

I've found one other thread ( https://community.victronenergy.com/questions/48449/why-mppt-is-overcharging.html ) which suggests that these controllers can reset the voltage to 24V by themselves. This seems dangerous.

Has anyone else experienced this? Is my MPPT faulty? Would you trust it with another battery? Or do I rip it out and put in something where I can set the voltage using an old-school jumper?

Thanks



MPPT ControllersMPPT SmartSolar
screenshot-2024-06-24-202433.png (121.7 KiB)
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kevgermany avatar image kevgermany ♦♦ commented ·
Please get the unit back to a dealer for testing under warranty.
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4 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hey all,

I’m glad to read that you found a more likely cause than a self-reset!

We’ve spent a ton of time doing a very complete analysis on all possible code paths that could lead to a change in the voltage setting. That was back in 2019, with regression testing happening since

-> I’m confident that its impossible for a solar charger to accidentally change its system voltage setting.


Also losing power, disconnecting from the battery, will never cause that. There are lots of systems out there with a main battery switch.

The only way for those settings to change is by the user, and the only way to set a unit back in auto detection mode is also by a user changing settings and/or reset to factory defaults.

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ejrossouw avatar image ejrossouw commented ·

@mvader (Victron Energy) That is good to know. Interestingly I recently disconnected my Victron EVCS to have a breaker replaced and it lost its settings and I had to go through the whole process of reconfiguring it. I did not have time to to carry out further testing, but is why I did not discount the same possibility for MPPTs.

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captainslow avatar image captainslow commented ·

Thanks for the response, that is reassuring to hear.

I am pretty sure there were incorrect (12V) settings doing harm to the battery for a long time, but I am still none the wiser as to how the SmartSolar controller ended up in 24V mode.

I am the only user of the camper with the VictronConnect app installed, the Bluetooth PIN is not the default, and the "digital wellbeing" log on my phone says I used the app for zero minutes that day. The camper was sat on my driveway under CCTV and nobody had physical access to it.

At 1359 Vbat was reading 16.6V, at the high end of 12V range, the next reading at 1432 it was reading 25.8V...

Drive-by Bluetooth hacking is about the only other possibility... perhaps I will use the "lock settings" option in future!

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ejrossouw avatar image
ejrossouw answered ·

@captainslow I would not discount also looking for a cause such as a disconnect / spike at the battery end due to an aging connection especially in a mobile application associated with movement. You may also want to look in much more detail at various other variables at the time leading up to the "reset". I have never personally seen this happen, but would be interested to know things such as the current firmware, settings, etc. Would be a shame if it is replaced under warranty and the problem arise again. Even if a software bug did show up after such a long time, it could be very difficult to find it without a lot more data that can help identify the actual trigger. Either way, worrying and curious at the same time.

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JohnC avatar image
JohnC answered ·

@captainslow

I don't think your problem started in those 7 days. The Vbat shows no plateauing at Absorb/Float, and was higher than normal anyway. The battery has possibly dried out from long term overcharge, so now you see the super-high V. Might have even been installed that way..??

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captainslow avatar image
captainslow answered ·

Thanks all - to @JohnC you might be right that the system was never set up correctly (the camper is a couple of years old, I've only owned it for a year) - as you say the Vbat seems like it was high even prior to the MPPT going into 24V mode - going back in time on the "trends" screen I am seeing a max battery voltage of 17.5-18V some days.

I've had multiple trips away with days off-grid and the system was performing fine, powering fridge + (gas blown air) heater etc, but maybe the high voltage from the solar was slowly killing the battery. The 24V+ spike could have just been the final straw.

Firmware was almost up to date (I think it was 0.01 below current firmware) so I don't think it was that. I had never changed the charging settings (I had stupidly assumed it was set up right) but after getting it out of 24V mode I now recall the battery preset was "user defined", I don't remember the voltage values before I changed the preset to AGM, but maybe someone's previous crazy settings was the cause of 17.5-18V battery voltages prior.

@ejrossouw you may be right too - if there was a momentary battery disconnect and the MPPT decided to detect the battery voltage again it may have seen a high enough voltage it thought it was a 24V system.

Thanks all for the insights.

The (rather expensive) lesson I've learned - don't trust that a new (to you) system is set up right...

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