Engine Battery low voltage

[cyberyacht]

Checked the engine battery voltage which was down to 12.3V . Lithiums, although not being fed by the solar atm, are a whisker under 13V. The batterymaster is displaying a steady green light and doesn't seem to be pulling anything from the leisure batteries. Is there a way I can check it is actually working. I'm not 100% sure it is one of Eddie VanBitz's gizmos. what voltage differential do these things kick in at?

 

[GeoffnDee]

Without the engine running If you put a load on the starter battery (turn headlights and fan on) the light on the battery master should turn red , I think that the differential is 0.8 v. (if a Vanbitz battery master). Green light = balanced --- Red light = charging

 

[Kannon Fodda]

Engine battery at 12.3V would still be reasonably charged. Not full but anything above 12.0V should be over 50%.

However, Lithium sits at a much higher fully charged voltage, usually comfortably above 13.0V, hence the need for the chargers to generally input at over 14V to create enough of a differential. If you aren't on solar, or EHU and the van has been unused for a while the lithium hab battery may now only have a limited charge. You can't monitor the lithium charge from voltage as it stays a lot more stable than the lead-acid types that lose voltage as they discharge. It could now be that there is limited capacity left in the lithium to be able to top off the cab battery.

 

[cyberyacht]

There are two lithiums in parallel. One sitting at 63%, the other at 87% although the voltages on both are, as I said a whisker under 13V so plenty of capacity. If, as you say, the differential is 0.8V then the engine battery isn'y quite low enough for the gizmo to kick in. I'm just a bit twitchy about the airbag ECU, having shelled out £400 on my last van for a new one.

 

[Tombola]

There are two lithiums in parallel. One sitting at 63%, the other at 87% although the voltages on both are, as I said a whisker under 13V so plenty of capacity. If, as you say, the differential is 0.8V then the engine battery isn'y quite low enough for the gizmo to kick in. I'm just a bit twitchy about the airbag ECU, having shelled out £400 on my last van for a new one.

Did I see a post form you OP sayng you had bluetooth BMS on your lithiums? (i think you are on KS energy like me) if so does it show the cells balanced on them, check if the cells are all balanced (or there abouts).

Also if you have had the battery a while, a good discharge and full recharge by the correct charger may be needed.

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[GeoffnDee]

The Battery master (Vanbitz) details state - The battery master measures the voltage on both batteries , if the leisure battery voltage is more than circa 0.8volts higher than the engine battery it will trickle charge the engine battery and bring the voltages back as close as possible.

 

[Raul]

There are two lithiums in parallel. One sitting at 63%, the other at 87% although the voltages on both are, as I said a whisker under 13V so plenty of capacity. If, as you say, the differential is 0.8V then the engine battery isn'y quite low enough for the gizmo to kick in. I'm just a bit twitchy about the airbag ECU, having shelled out £400 on my last van for a new one.

At 87% under 13v sounds low to me. I’m currently at 74,3% with 13,18v. As Tombola says, you may need to charge them up, it may need some cell balance to improve the pack voltage. Also, having two in parallel with such a SOC % difference, it does not help. I would bring them as close as possible in % SOC.

 

[cyberyacht]

I'm not sure the newer battery SOC% reading is correct. The voltages across all the cells of both batteries are within 0.01v of each other. The original battery is just over a year old and has done 27 cycles compared with only 1 cycle on the new one. I've read that they need a few cycles to show an accurate SOC %. I just checked a short while ago and the new battery was pushing about 0.7A across into the old battery for a brief period although the older battery was showing a fractionally (0.01v) higher voltage than the donor battery.

According to the info sheet supplied with the battery, there should be a decay rate of 2.5% per month but whilst the new battery is showing a steady SOC%, the original one is has declined at about 9% over 20 days - about 4 times the expected rate. Voltages on both batteries have declined by 0.06v over the same period.

 

[Lenny HB]

There are two lithiums in parallel. One sitting at 63%, the other at 87% although the voltages on both are, as I said a whisker under 13V so plenty of capacity. If, as you say, the differential is 0.8V then the engine battery isn'y quite low enough for the gizmo to kick in. I'm just a bit twitchy about the airbag ECU, having shelled out £400 on my last van for a new one.

No way would I risk starting the engine with the battery that low because of the Airbag ECU risk.

These are reckoned to be better for keeping the starter battery topped up when you have Lithium leisure batteries.

Ablemail AMT-12 Battery Maintainer – Wildebus

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