Time for a Battery Master?

[KMarkN]

Hi, I'd appreciate some advice. I'm generally practical but not yet experienced with motorhome electrics - definitely still learning! After camping for 3 nights in Devon I noticed the van turned over a while before starting, and wondered if the cab battery was down a bit but thought no more of it.

We have Elddis pvc, a new CV60, with 100W solar panel that charges first the leisure battery (95aH AGM) and then the cab battery. Mostly we use EHU and I can easily hook up at home.

One week after returning from a trip, without any EHU at home, my cab battery showed 12.29v and leisure battery 13.75v. I then attached EHU and got readings of 12.29v cab and 13.85v leisure. How do I interpret these? Has cab battery run down (alarm has been on for one week) and leisure battery kept charged via solar, despite having little sun? Should leisure battery read higher voltage, both before and after hooking up? And can I assume that solar has not transferred over to cab battery, given it's lowish voltage?

Reading on here it seems a BM would work for me, given that we often use EHU, and can do at home. Especially at home, this would I think mean I dont have to run vehicle just to keep the van battery charge up?

Am I correct would you say? Many thanks in advance!

 

[Beryl]

We've got an Elddis 115, didn't pay extra to have the solar connected to both batteries and just got a battery master instead. That way whatever is topping up the leisure battery, be it EHU or solar, if the cab battery drops the battery master trickle charges it until it's back up.

 

[Cheshirecat57]

Hi, I'd appreciate some advice. I'm generally practical but not yet experienced with motorhome electrics - definitely still learning! After camping for 3 nights in Devon I noticed the van turned over a while before starting, and wondered if the cab battery was down a bit but thought no more of it.

We have Elddis pvc, a new CV60, with 100W solar panel that charges first the leisure battery (95aH AGM) and then the cab battery. Mostly we use EHU and I can easily hook up at home.

One week after returning from a trip, without any EHU at home, my cab battery showed 12.29v and leisure battery 13.75v. I then attached EHU and got readings of 12.29v cab and 13.85v leisure. How do I interpret these? Has cab battery run down (alarm has been on for one week) and leisure battery kept charged via solar, despite having little sun? Should leisure battery read higher voltage, both before and after hooking up? And can I assume that solar has not transferred over to cab battery, given it's lowish voltage?

Reading on here it seems a BM would work for me, given that we often use EHU, and can do at home. Especially at home, this would I think mean I dont have to run vehicle just to keep the van battery charge up?

Am I correct would you say? Many thanks in advance!

What makes you think the solar charges the cab battery??

 

[KMarkN]

What makes you think the solar charges the cab battery??

It's wired up to do that, and leds show it is happening. Very little sun in last week though?

 

[funflair]

Yes, fit a battery master and you should be sorted.

I should have added that a Vanbitz BM and other ones work quite differently and in my opinion the Vanbitz one is better suited to your needs.

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[Cheshirecat57]

Dont understand why cab battery is only on 12.29 with a soliar charge
But a battery master should sort it

 

[KMarkN]

Dont understand why cab battery is only on 12.29 with a soliar charge
But a battery master should sort it

Agree - that's why I posted. Van has sat unused for 10 days, with alarm on, and us going in and out a few times. So I guess that degree of voltage reduction is not unusual except for fact that solar charger is showing full charge??

 

[KMarkN]

I measured charge from jump starting points under bonnet, rather than directly from battery terminals. Would that make a difference?

 

[Cheshirecat57]

One way to find out

 

[KMarkN]

One way to find out

Haha true - but it's dark and raining now so I'll have to try that tomorrow!

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[RandallC]

Having looked at several spec sheets for solar charge controllers there is something most need to be aware of.

The controllers I've seen (NOT ALL) have a charge priority for the HAB batts,, if they are full or very near full then the controller will charge the starter battery.

ALAS if you have some demand on the Hab batts like the aerial amp and the Inet/Heating/hot water systems, albeit thought to be switched off, there is a small current drain. As the short days approach this becomes more significant and less solar spare capacity is available to the starter battery. Which may have the radio, alarm, tracker etc attached. So it's possible the starter batt never gets anything/too little fro the solar as the priority is the Hab system.

A Battery Master system ensures that the starter tracks the Hab within 1/2 a volt or there about.

Remember however short dismal winter days MAY NOT provide enough sun to keep your batts healthy. e.g. Keep and eye on them.

 

[KMarkN]

Having looked at several spec sheets for solar charge controllers there is something most need to be aware of.

The controllers I've seen (NOT ALL) have a charge priority for the HAB batts,, if they are full or very near full then the controller will charge the starter battery.

ALAS if you have some demand on the Hab batts like the aerial amp and the Inet/Heating/hot water systems, albeit thought to be switched off, there is a small current drain. As the short days approach this becomes more significant and less solar spare capacity is available to the starter battery. Which may have the radio, alarm, tracker etc attached. So it's possible the starter batt never gets anything/too little fro the solar as the priority is the Hab system.

A Battery Master system ensures that the starter tracks the Hab within 1/2 a volt or there about.

Remember however short dismal winter days MAY NOT provide enough sun to keep your batts healthy. e.g. Keep and eye on them.

Thanks, that makes a lot of sense. The hab battery was reading 13.75v would that register as full with the controller?

 

[Kannon Fodda]

For a majority of MHs the cab battery is charged only by the engine. Leisure battery will be charged by engine, solar and EHU charger. Engine though may not give the charge you think to the habitation, unless you have a B2B, as many alternators are signalled to ramp down the amperage when they sense a fuller battery in the loop i.e. the cab.

If on EHU, unless there is some special switching your cab battery won't be getting a charge, yet standard wiring means the cab radio if used whilst parked up, alarm, and similar will be draining the cab battery.

Some systems do have the solar enabling a small portion of the solar to divert to the cab battery (which as above may only send power to the cab if the hab is close to full charge), or as they had wired my Autotrail a switch allowed you too select solar charge entirely to hab or cab.

Battery Master, at least the VanBitz version, will trickle charge up to 1A the cab battery when it senses a slightly lower voltage in the cab battery. That way, all solar, EHU can be put into the hab, and the hab will deal with the slight drain when parked up from alarm, radio or whatever.

Note that whilst being charged, or there is a reasonable load, the voltages across batteries may be misleading. You need to let them stabilise for half hour or so, to be closer to the real storage.

 

[JockandRita]

This wee chap will come into it's own to charge the cab battery by up to 4A, once the leisure batteries reach a voltage of around 13.3v, whether you are on solar, alternator, or mains charging.

Great when in storage for keeping the cab battery charged when the alarm is on, and there is solar power.

Cheers,

Jock.

 

[bigwood]

As others have said fitting a battery master is a case of fit and forget. The solar panel on our motorhome was only connected to the leisure battery when we bought it. The only way to charge the vehicle battery was from the engine when we were on the move. On hook up we could select leisure or vehicle battery charging.
Fitting the battery master means the vehicle battery is charged whilst stood from the solar panel and we only need to leave the the battery charger on leisure when on hook up.

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[JockandRita]

This wee chap will come into it's own to charge the cab battery by up to 4A, once the leisure batteries reach a voltage of around 13.3v, whether you are on solar, alternator, or mains charging.

Great when in storage for keeping the cab battery charged when the alarm is on, and there is solar power.

Cheers,

Jock.

Oops, I forgot to add the link.

CAK Tanks BCM12.

Cheers,

Jock.

 

[funflair]

Oops, I forgot to add the link.

View attachment 431096

CAK Tanks BCM12.

Cheers,

Jock.

I thought that was 13.6v Jock? thats why I added the VB battery master to the Flair as the CBE CSB2 wasn't always charging the starter when solar was low and the leisure bank was below the threshold, plus I wanted to join the batteries so they all dropped together allowing the EFOY to auto trigger but that is another thread

 

[JockandRita]

I thought that was 13.6v Jock?

I wasn't exactly sure Martin, hence my post. ...................

once the leisure batteries reach a voltage of around 13.3v,

Cheers,

Jock.

 

[Jev88]

Doesn't appear that your solar controller is actually sending any charge to cab battery? What happens if you disconnect the leisure battery so the controller can only send juice to the cab battery?

 

[Vipar]

Oops, I forgot to add the link.

View attachment 431096

CAK Tanks BCM12.

Cheers,

Jock.

Thanks Jock. ordered and awaiting delivery

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[KMarkN]

Doesn't appear that your solar controller is actually sending any charge to cab battery? What happens if you disconnect the leisure battery so the controller can only send juice to the cab battery?

That's right. Although the led on the controller is showing that the cab battery is fully charged? Is it safe to simply detach the two wires leading to the leisure battery, to try your suggestion?

Cab battery had dropped a little more today, to 12.2v, so I took it for a drive. It started fine. On return, voltage was 14 with engine running, and 12.9 when I switched off. So alternator seems to be working.

 

[Jev88]

That's right. Although the led on the controller is showing that the cab battery is fully charged? Is it safe to simply detach the two wires leading to the leisure battery, to try your suggestion?

Cab battery had dropped a little more today, to 12.2v, so I took it for a drive. It started fine. On return, voltage was 14 with engine running, and 12.9 when I switched off. So alternator seems to be working.

Yes alternator is good, but it looks like your controller is simply not sending any power to cab battery.
Can't do any harm to disconnect the leisure battery as you would ave to do this when replacing the battery. Then measure voltage at controller and voltage at cab battery (no engine running and not just after engne has been run). Is there an APP that you can control your solar controller? Or do you have a diplay with buttons? It is also possible it is set wrongly ?

 

[Diabalo]

On the pro version there is a Bluetooth app, not sure if the OP's has that function.

 

[jeffcav]

In addition to the wonderful advice above here is something else to consider, the victron Cyrix CT range, it includes an optional start assist button which will switch the hab battery in for 30 secs to start your van. here is the details link - https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-ct-120A-230A-EN.pdf