Charge starter battery but not lithium (1 Viewer)

[Folkranger]

I've recently gone through the pain of a failed airbag ECU due to low battery state. The new van that I'm picking up next week has a solar/ lithium leisure battery set-up. Don't know details yet.

My question is...... Is it possible to keep the starter battery solar charged when not in use but switch off the charging to the leisure lithium battery?

Sorry about the lack of details on the kit.

 

[Googlebot]

A battery master from Vanbitz will keep your battery topped up. You can turn the solar off then.

It works by detecting when the engine battery is getting low and giving it a small charge from the leisure batteries. Obviously this won’t last forever but is a much better option with lithium.

 

[pete4x4]

My battery master didnt really work with Lithium, the charge to the starter battery is approx 0.8v below the leisure battery and in this case thats 13.2-0.8 = 12.4 volts at best, and bear in mind this is below the recommended minimum voltage that CrashData recommend to prevent the airbag warning late coming on.
Clearly if you are float charging Lithium higher than 13.2v then you will get charge.

I went with the Ablemail AMT12 which is designed for Lithium and works really well.

 

[autorouter]

and bear in mind this is below the recommended minimum voltage that CrashData recommend to prevent the airbag warning late coming on.

I don't believe that. Automotive electronics, especially safety-related items, must conform to rigorous standards to be passed as suitable for use in a vehicle. If it causes an unrecoverable error at 12.4V it is not fit for purpose.

 

[Raul]

Yep, when you crank start the battery can deep into 11v or lower on a normal operation.

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[pete4x4]

And there in lies the problem the Peugeot Airbag unit is not fit for purpose. Crashdata seem to be making a fortune out of owners who have allowed their starter batterys to get too low or even flat and the airbag module has failed on jump starting. The advice is to maintain the starter battery at a minimum of 12.4v at rest, anything less than that can cause problems on Peugeot based motorhomes from around 2014 on.
Note I said at rest and not cranking volts.

 

[stevewagner]

I have lithium leisure batteries and a Sterling Battery master that works well.

 

[John H.]

I think the best step I made to protect the ECU was to replace the engine battery with a new good quality one. (as big as would fit).

 

[Folkranger]

A battery master from Vanbitz will keep your battery topped up. You can turn the solar off then.

It works by detecting when the engine battery is getting low and giving it a small charge from the leisure batteries. Obviously this won’t last forever but is a much better option with lithium.

I'd rather have the solar bypass the lithium and keep the starter battery charged if possible.

 

[Folkranger]

Look, I know only too well that the fiat ecu is too sensitive. I still have the question which relates to:
A) It's necessary to keep the starter battery on charge and some solar systems don't do this. (Not sure if the new one does yet)
B) it's best to not leave the lithium on charge when not in use.

I'd like to keep the starter battery charged by solar but switch off charging to lithium. How can this be achieved?

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[Folkranger]

My battery master didnt really work with Lithium, the charge to the starter battery is approx 0.8v below the leisure battery and in this case thats 13.2-0.8 = 12.4 volts at best, and bear in mind this is below the recommended minimum voltage that CrashData recommend to prevent the airbag warning late coming on.
Clearly if you are float charging Lithium higher than 13.2v then you will get charge.

I went with the Ablemail AMT12 which is designed for Lithium and works really well.

Had a look at the description of these. I'm still not sure how they work as ideally I want no charge to go into the lithium when not in use.

 

[Folkranger]

I don't believe that. Automotive electronics, especially safety-related items, must conform to rigorous standards to be passed as suitable for use in a vehicle. If it causes an unrecoverable error at 12.4V it is not fit for purpose.

Its NOT fit for purpose but there are many thousands of Fiat, Peugeot and Citroen Van's that have been using this for the past decade. There is no problem with vans as they get used regularly. The problem arises when these Van's are used in motorhomes which are often laid up for prolonged periods. The pandemic has caused an epidemic of motorhome ecu problems.

 

[Folkranger]

And there in lies the problem the Peugeot Airbag unit is not fit for purpose. Crashdata seem to be making a fortune out of owners who have allowed their starter batterys to get too low or even flat and the airbag module has failed on jump starting. The advice is to maintain the starter battery at a minimum of 12.4v at rest, anything less than that can cause problems on Peugeot based motorhomes from around 2014 on.
Note I said at rest and not cranking volts.

Not just Jump starting. My mh battery seemed perfectly ok, starting the engine with ease after nearly a year lay up. But the airbag light came on.

 

[Folkranger]

I have lithium leisure batteries and a Sterling Battery master that works well.

Do you know that you aren't reducing battery life by charging lithium when not in use. Or risking ecu faults by not keeping on charge.

 

[Folkranger]

I think the best step I made to protect the ECU was to replace the engine battery with a new good quality one. (as big as would fit).

This thread is not about ecu faults. It is about protecting the lithium battery without putting the ecu at risk. Thanks for all the answers but is there anyone who is qualified to answer this specific point?

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[Dark_Comet]

Surely the solar panel controller which should be an mppt and not a cheap pwm, is designed to be left on all the time with any kind of leisure battery. Ensure the controller can be programmed to charge a lithium battery as not all are. If you cannot park your vehicle for a week or more and the starter battery loses the charge, you got a faulty battery.

 

[Tombola]

Do you know that you aren't reducing battery life by charging lithium when not in use. Or risking ecu faults by not keeping on charge.

I think you mean "are"
and yes you can. Fit an inline switch to direct the flow from the solar to the cables you can install (or maybe already installed) leading to the cab battery.
Some systems have this capability anyway, automatic, but we would need to know your electrical set up to determine.

the battery master would take a tiny trickle from the lithium over many weeks, so for a fast fix this is the best

 

[Googlebot]

As tombola said, just fit an online switchover from the leisure battery to the van battery via the solar charge cable from the controller.

I would however advise you turn the panels off somehow with a switch or cover them with cardboard when you do this. Some controllers are sensitive to voltages and might not like the quick flick between while powered up.

 

[stevewagner]

A battery master from Vanbitz will keep your battery topped up. You can turn the solar off then.

It works by detecting when the engine battery is getting low and giving it a small charge from the leisure batteries. Obviously this won’t last forever but is a much better option with lithium.

This thread is not about ecu faults. It is about protecting the lithium battery without putting the ecu at risk. Thanks for all the answers but is there anyone who is qualified to answer this specific point?

In my case the lithium batteries have a built in BMS which is programmed to stop taking a charge from the solar panels at 90% full. The solar MPPT controller is set for lithium profile so also won’t charge more than is required. The battery master trickle charges the cab battery to keep it fully charged. The CBT charger is now permanently switched off as it is no longer needed. I also have a Sterling B2B charger which fast charges the lithium’s when the engine is running. For me this is the perfect set up as we go off grid quite a lot and never had an issue.

 

[autorouter]

You want the starter battery to be charged/maintained from solar while the vehicle is not in use. You want the leisure battery to be charged to a predefined value, perhaps 60%, then isolated.

I suggest you get a small mppt controller, connect it to the starter battery on a lead-acid profile, then put one of the panels, about 100W, on a changeover switch (manual or relay). That way the starter battery gets a dedicated controller with enough power to keep it maintained, even over a few days of bad weather..

When it's time for action, switch the panel over to the main mppt controller, so it feeds to the leisure battery. Adding/subtracting one parallel panel will not affect the main solar controller, especially as it's not charging the leisure battery anyway.

If I had this problem. I'd be thinking of putting the airbag ECU supply on a stabilised 12.8V supply. Something that will supply 12.8V when the input voltage is 10 to 30V. That's what should be built into the ECU in the first place.

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[Raul]

This thread is not about ecu faults. It is about protecting the lithium battery without putting the ecu at risk. Thanks for all the answers but is there anyone who is qualified to answer this specific point?

I have the perfect solution for you. Ignore the switch over from leisure to starter from the controller. It doesn’t work that way. Your controller needs to be connected to a battery without interruption. Using the same solar panels but two controllers. One for the leisure lithium with appropriate settings, and one connected to the starter with lead settings. Have a switch over at the solar coming in to the controllers. You can pick controller 1 for Leisure Li, or controller 2 for starter lead to dump the solar into. All you need is extra wire, a manual switchover contactor, and a additional controller like victron 75/10 for the starter. This is by far best way no compromise and sure way to cater for different charging profiles from the same solar source.

 

[the1andonly]

I'd like to keep the starter battery charged by solar but switch off charging to lithium. How can this be achieved?

I achieve this by using a votronics 250 mppt controller the main output is set Lithium the second output is factory set to Pb acid (info from uk distributor in daventry) the main out has a switch to Lithium battery.

 

[Folkranger]

I think you mean "are"
and yes you can. Fit an inline switch to direct the flow from the solar to the cables you can install (or maybe already installed) leading to the cab battery.
Some systems have this capability anyway, automatic, but we would need to know your electrical set up to determine.

the battery master would take a tiny trickle from the lithium over many weeks, so for a fast fix this is the best

That's what I was hoping to hear. I'll know more when I get the van and see the exact charging layout.

 

[Folkranger]

I think you mean "are"

I asked if he knows that he isn't damaging his battery because he leaves it charging.

 

[Tombola]

I asked if he knows that he isn't damaging his battery because he leaves it charging.

Ahhh, sorry, I thought you had meant to tell him can be damaging them.
Yes then Lithium dont like being constant float charged

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[Folkranger]

In my case the lithium batteries have a built in BMS which is programmed to stop taking a charge from the solar panels at 90% full. The solar MPPT controller is set for lithium profile so also won’t charge more than is required. The battery master trickle charges the cab battery to keep it fully charged. The CBT charger is now permanently switched off as it is no longer needed. I also have a Sterling B2B charger which fast charges the lithium’s when the engine is running. For me this is the perfect set up as we go off grid quite a lot and never had an issue.

That sounds like a good set-up. I read somewhere on this site that lithium should be down to 50% when left for extended periods.

I have the perfect solution for you. Ignore the switch over from leisure to starter from the controller. It doesn’t work that way. Your controller needs to be connected to a battery without interruption. Using the same solar panels but two controllers. One for the leisure lithium with appropriate settings, and one connected to the starter with lead settings. Have a switch over at the solar coming in to the controllers. You can pick controller 1 for Leisure Li, or controller 2 for starter lead to dump the solar into. All you need is extra wire, a manual switchover contactor, and a additional controller like victron 75/10 for the starter. This is by far best way no compromise and sure way to cater for different charging profiles from the same solar source.

I'm beginning to think that life was much simpler with my two lead acid batteries.

 

[Raul]

Nothing stops you to revert back to “simpler”. I fail to see how is simpler with lead.

 

[pete4x4]

Considering a Battery Master is almost the same price as an Ablemail AMT-12 I would go for the AMT-12 because unlike the Battery master it is designed with Lithium in mind and will not flatten the Lithium battery in favour of the starter if you leave it for a long time.

 

[pete4x4]

That sounds like a good set-up. I read somewhere on this site that lithium should be down to 50% when left for extended periods.

I'm beginning to think that life was much simpler with my two lead acid batteries.

Lithium is indeed best stored at 50% when disconnected but if you have a load on it such as something to maintain the starter battery then it needs to stsrt off at 100%.

 

[Folkranger]

Nothing stops you to revert back to “simpler”. I fail to see how is simpler with lead.

No chance I'm going back, it's just doing my head in trying to understand all this.