Hymer Smart Battery and chassis battery voltage

[PDrill]

When the van arrived from the factory last May, the lithiums were dead and so was the AGM. The AGM was replaced but the lithiums didn't even communicate with the testing equipment so they were taken to the warranty process. I noticed the factory installed inverter was on, so I thought maybe the batteries have died because of that being the situtation probably for months. After 6 months (!!!) I finally got new lithiums, and I think there's something wrong with the system and I'm more than a bit worried the batteries might die again.

The thing is, even with everything turned off (and I have no aftermarket installations), the lithium may drop up to 10% per day. Then I noticed the chassis battery doesn't seem to go below 13.0 volts. Makes me think somehow the lithiums are keeping the chassis battery charged, and that's not sensible. The chassis battery was disconnected for ~36 hours due to a repair on the engine, and during that the percentage of the lithiums didn't seem to drop the same way. As the time was so short and I wasn't alert and monitoring the situation from the beginning, I don't have facts about this. I'm also not quite satisfied with the Smart battery performance during wild camping, but if it goes down almost 10% per day on it's own, no wonder the performance is slightly less than expected.

So my question is, what does your chassis battery and Hymer lithiums show if the van has been unused and cold without EHU for a few days?

 

[CAB96]

Many on here add a battery maintainer to do exactly that - keep the starter (chassis) battery topped up from the Leisure batteries, as modern vehicles have so many electrical systems that starter batteries can be dragged down in a few weeks of non-use.

But 10% a day? That's ridiculous. There is something wrong. Either the starter is being drained and in turn draining the Leisure, or something else is draining the Leisure.

 

[oldiesontour]

The lithium's should have some sort of BMS protection to stop them discharging below a set point,so should not be harmed by a continual drain...therefore the original lithium's should have been un harmed ... something very wrong or poor components(lithium's) and poor diagnosis/ rectification

 

[rod_vw]

I have 230Ah of Lithium, 200W solar and an Ablemail AMT 12-2 engine battery maintainer.

Whilst parked in the open in the present February weather and using internal lights plus some hours using my Eberspacher heater my lithium battery does not drop anywhere near 10% in a day usually no more than 3%.
The AMT 12-2 draws about 3.5A in three second bursts every 10 seconds as every opening of the doors starts various vehicle modules thus depleting the engine battery.

I would suggest that the OP monitors the BMS whilst removing various circuits either by switching items off or removing fuses to find the source of current draw. One (or more) of these operations will reveal the source of his problem.

 

[Lenny HB]

I have heard from someone in the trade that both Hymer and Carthagos with factory installed Lithium's have the starter battery losing charge very quickly.
My mate suffered it as well with his Carthago.

I avoided it by doing my own Lithium install.

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[LithiumConvert]

So my question is, what does your chassis battery and Hymer lithiums show if the van has been unused and cold without EHU for a few days?

Our 2022 Hymer Exsis came with some Hymer wiring and empty connectors only for the optional Hymer Lithiums.

But, it all seems pointless - because, if you just take out the Hymer fitted AGM battery and put in some Sterling Power LiFePO4 in its place, all you have to do is change some DIP switches in the Schaudt B2B and the EBL......
...... and then everything just works. - No other changes needed.

And the starter and leisure batteries stay charged as you would hope.