Strange starter battery voltage on EBL227 of over 20v

[RogerIvy]

Hoping someone may have experienced this problem to save us some investigation time.

Someone came in with an Adria that has a EBL227 and Schaudt booster.
During a hab check it was discovered that his starter battery is reported by the control panel to be over 20v.
We checked the starter battery - normal voltage of 12.7-ish
Checked where the starter cable comes into the back of the EBL227 - it’s around 25v
Checked where the starter cable comes into the booster - around 25v
We disconnected the starter battery cable from the back of the EBL, checked that cable and it’s 12.7-ish. The starter battery in the control panel slowly coming down to around 9v and settles there.
At the same time the incoming feed to the booster also drops to around 9v.
Reconnected the feed from the starter to the EBL and immediately jumps to over 20v, feed into the booster also over 20v

So it seems something in the EBL is “back feeding” a high voltage to the starter battery, luckily the starter battery is not actually going higher than 12.7-ish. But TBH I’d not trust that it won’t go higher, and so is the owner of the vehicle.

He has had numerous issues with this particular motorhome and isn’t sure when this particular problem started, it may have been there since he bought it.

It seems to be a possibility that the EBL is faulty. But I’ve never known this sort of problem. Unless I need to think further out the box. He’s going to contact Apuljack to see if they have any ideas and to see if a repair is feasible.

Has this happened to anyone else, and if so what caused the problem and what was your fix?

 

[Googlebot]

I had a weird event like that once, when I changed over to lithium.

Can’t remember the sequence of events but crapped myself as something wasn’t working and the voltmeter on the display was off the scale. This was confirmed with a cheapo voltage meter plugged into a 12 outlet on the hab side.

Turned the 12v feeds off and on via the dial push switch thing above the door and it went and hasn’t come back since. No damage that I can find years later. I vaguely recall it was after I connected the hab batteries up.

Tried thinking about how on earth I managed to get 24v through the system, couldn’t work it out and gave up.

Sorry, that probably doesn’t help, I am sure the EBL was the problem though.

 

[Pausim]

After installing a Votronic B2B and Sterling mains charger on my Hymer I had strange 20V plus surges when the engine shut down. I realised I had created a loop back to the engine battery through the split charge relay. After I rectified the loop back the problem voltage surges went away. However I could not see why removing the loop could affect a problem that only occurred after the engine shut down had broken the unwanted loop. I never did find the reason but decided that wiring out the loop must have incidentally separated two components that were interacting, perhaps as their capacitors decayed after being shut down. The likeliest candidates were the Sterling charger and the B2B outputs which became separated by the EBL after my removal of the loop. Before that the two outputs were both wired directly to the leisure battery.

It all happened 6 or 7 years ago and I can’t remember all the details of what I did at the time.

 

[Raul]

The only 20v plus source possible, could be a solar panel, or, starter battery somehow on series with habitation source.

 

[mitzimad]

is this 20v when the engine is running?

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