Battery Master and Lithium: Quick question

[Ingwe]

Had a Battery Master (“BM”) for three years now and since then no flat starter batteries. I understand that the BM works by the starter battery receiving a small trickle voltage from the leisure battery when the starter battery voltage drops below a preset voltage relative to the leisure battery.

Now that I have lithium batteries fitted it has been 35 days since they were fully charged and they are at 78% state of charge. From the chart of approximate voltages, the voltage of the leisure battery should be about 13.2v.

So my question is, if the leisure battery is 13.2v the voltage of a fully charged starter battery is 12.7volts, then there is still enough charge in the leisure battery to keep the starter battery topped up for some time? Presumably at some point (from the chart of approximate voltages) when the leisure batteries reach 14% state of charge the approx voltage of 12.5 v will be too low to feed the starter battery? I’ve no intention of letting the leisure batteries get to below 50% state of charge before hooking up but was just thinking about the point where the starter battery starts becoming vulnerable to being unable to start the van.

I hope I’ve articulated my question well enough. Thanks in advance.

 

[funflair]

I am not sure which "chart of approximate voltages" you are referring to but if it is one for lead acid it is not applicable to LiFePO4, your leisure batteries should hold their voltage as basically a flat line and high enough to support the starter battery but without any solar it might be sitting at around 12.5v, that is my experience anyway.

 

[Jimbohorlicks]

Does your battery master still show a charge going to the starter battery from the 13.2 v lithium battery even when the starter battery is fully charged at 12.7 v?

 

[funflair]

Does your battery master still show a charge going to the starter battery from the 13.2 v lithium battery even when the starter battery is fully charged at 12.7 v?

If that's a question for me NO.

 

[Jimbohorlicks]

If that's a question for me NO.

Not really Martin ,it was for Ingwe .
It just that I will soon be fitting a lithium and wondered if could potentially overcharge the starter battery.

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[Ingwe]

I am not sure which "chart of approximate voltages" you are referring to but if it is one for lead acid it is not applicable to LiFePO4, your leisure batteries should hold their voltage as basically a flat line and high enough to support the starter battery but without any solar it might be sitting at around 12.5v, that is my experience anyway.

Thanks for the reply. This is the voltage chart supplied by the lithium battery installers. It may help with understanding why I asked the question.
I've just returned from checking the van (kept in storage with no solar) and today’s readings are: 67% SOC, voltage 13.26, current discharge -0.19A. That’s after 39 days, 4 hours since last fully charged.
The starter battery was 12.6v.

 

[pete4x4]

I replaced my Battery master with an Ablemail device. My battery went down to 12.4 with my Lithium at 13.2, 0.8v difference as stated by BM. I didn't like that, thought it too low.
The Ablemail trickle charger maintains the starter battery at 12.69v.

 

[Ingwe]

Does your battery master still show a charge going to the starter battery from the 13.2 v lithium battery even when the starter battery is fully charged at 12.7 v?

I think the answer to your question is no. I say this because after checking the leisure battery at 67% SOC, the green light was was showing on the BM and the starter battery was at 12.6v (which I believe is fully charged).
However, to check that the BM was working, I turned on the headlights and the BM light changed to the red light showing a trickle to the starter battery.

 

[WildBunch]

Has anybody got thoughts on the "Ablemail Electronics AMT12-2 Battery Maintainer instead of the normal Van Bits BM. It seems to pulse charge the start battery 3 sec on 15 sec off, is this good ?
I am reading the installation instructions & can't see where SW 1 & SW 2 are. "Is it me
?"https://www.ablemail.co.uk/sites/de...le Charge Installation Instructions Rev.A.pdf

 

[seanwinder22]

Just picked up on this thread I’m finding interesting
Can anyone tell me if the vanbitz works fine with lithium set up like it does lead acid ? Or will I need the amt-12 from widebus

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[Wissel]

Just picked up on this thread I’m finding interesting
Can anyone tell me if the vanbitz works fine with lithium set up like it does lead acid ? Or will I need the amt-12 from widebus

The Vanbitz one works great with Lithium.

Had one myself (with LiFePO4) for years, and fitted loads to other peoples vans.

 

[seanwinder22]

The Vanbitz one works great with Lithium.

Had one myself (with LiFePO4) for years, and fitted loads to other peoples vans.

Thanks buddy yes I’ve got one on now but it’s lead my lithium be in next week . I’m just going off what I’ve read on here everyone taking it out to have this Amy-12 ablemail

 

[Ingwe]

The Vanbitz one works great with Lithium.

Had one myself (with LiFePO4) for years, and fitted loads to other peoples vans.

What he said!

 

[funflair]

Ours works fine as well the van in indoors so no solar or EHU and the LiFePO4 keeps the starter battery around 12.5v which is enough to start which is all I care about, if it's outside and getting sunshine on the solar the starter would be higher.