# How to charge cab battery from solar panel



## jiwawa (Jun 22, 2007)

We have a 130w solar panel feeding 2x125A leisure batteries and that works well.

However, we're now having to park our van away from a source of electricity for long periods of time, and I need a way to keep the cab battery tanked up. We went out today to take it for a run today to make sure it was ok. Dead as a dodo!!

Is what I'm looking for a battery-to-battery charger? I wouldn't be fitting it myself.

I also want to get an inverter - should I get them fitted at the same time or does it not matter?

I'd appreciate any recommendations for whatever's needed to keep the cab battery charged.

Many thanks.


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## camoyboy (May 9, 2005)

You need to get a "Battery Master" to connect between your cab battery and leisure batteries. This will allow a trickle charge to the cab battery from the leisure batteries, which are being kept topped up with the solar panel.

A battery to battery charger is for rapid charging the leisure batteries from the cab battery while driving.

You can get an inverter fitted any time.

Colin


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## veevee (Nov 6, 2011)

I've used a CBE CBS-2 for around 3 years, tops up cab battery when leisure batteries are at a charged level. Vehicle out in the sun (1 solar panel) all year summer and winter and never ever had a flat cab battery yet even though don't start the engine but about once each month. Also never connected to mains when left standing.


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## lgbzone (Oct 8, 2008)

The CBS devices are fantastic and a fraction of the price of the battery master, i've been using them for years, highly recommended.
Lee


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## Pudsey_Bear (Sep 25, 2008)

JWW said:


> We have a 130w solar panel feeding 2x125A leisure batteries and that works well.
> 
> However, we're now having to park our van away from a source of electricity for long periods of time, and I need a way to keep the cab battery tanked up. We went out today to take it for a run today to make sure it was ok. Dead as a dodo!!
> 
> ...


Keep it simple

http://www.motts.org/BRIDGING FUSE.htm

As for an inverter, it's a simple enough DIY job if you like doing jobs on your van, connect to battery, and then either run some cable to a single socket or more, some just use the socket on the inverter, care needs to be taken in choosing sufficient wattage output, but not more than you need, IE figure out what you are likely to plug in and look at the label for its watts.


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## dghr272 (Jun 14, 2012)

Kev, like the simple approach.

What size of cable for the b2b connection ?

Terry


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## Pudsey_Bear (Sep 25, 2008)

dghr272 said:


> Kev, like the simple approach.
> 
> What size of cable for the b2b connection ?
> 
> Terry


It needs to be big enough to take the charge amps so unless you have a large array 2mm2 with a 10amp fuse might be enough, make sure it is fuse at the LBs and VB terminals as well as the bridging fuse to err on the side of safety as I can't see your layout, use grommets if going through metal.


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## Pudsey_Bear (Sep 25, 2008)

useful guides

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

http://www.12voltplanet.co.uk/fuses-guide-uses.html


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## tugboat (Sep 14, 2013)

Simple is OK, but what about convenience. Personally, I can't be ***ed to swap fuses around when getting in and out of the van, and think such a set-up would look rather amateurish and out of place in a nice vehicle.

For 70 quid, I reckon the Battery Master is good value, fit and forget. Mine is under the bonnet, and each time I check the oil I look at the BM and the light on it tells me if the batteries are 'equalised'.

Just my 2cents worth.


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## Pudsey_Bear (Sep 25, 2008)

tugboat said:


> Simple is OK, but what about convenience. Personally, I can't be ***ed to swap fuses around when getting in and out of the van, and think such a set-up would look rather amateurish and out of place in a nice vehicle.
> 
> For 70 quid, I reckon the Battery Master is good value, fit and forget. Mine is under the bonnet, and each time I check the oil I look at the BM and the light on it tells me if the batteries are 'equalised'.
> 
> Just my 2cents worth.


Valid point Geoffrey :wink2: but it's nice sometimes to just do it simply, and get some man points by doing it yourself :surprise:


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## subfiver (Oct 15, 2011)

Have you got an MPPT solar controller (you should have..)

Votronic make (in Germany) MPPT solar controllers that charge the domestic batteries and simultaneously trickle-charge the vehicle start battery. My vehicle is parked in Lancashire all summer and keeps my starter battery tip-top (I can remotely monitor the voltage via the fitted tracker).

The Votronic controllers can also make your Dometic fridge switch over from gas to DC when the vehicle is (a) stationary and (b) enjoying copious amounts of sunshine.


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## eurajohn (May 9, 2005)

What main controller is your van fitted with?
If it is a Schaudt Electrobloc, buy one of their solar controllers (LR1218 I think) it comes with English instructions and all the necessary wiring, plugs, fuses etc. then connect straight up to Electrobloc as per instructions and you will have not only leisure and vehicle batteries charged you will also be able to see/monitor what the panels are giving via you control panel.
They can be bought for around €70 (that's Euros not pounds) from France.


.


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## jiwawa (Jun 22, 2007)

We have the Schaudt Elektroblok EBL-99G, and yes, we do have an MPPT - pr202_._

Can this MPPT be used to tank up the van battery the way subfiver mentions above?

Thanks to all for the contributions.


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## Penquin (Oct 15, 2007)

BatteryMaster is three wires only to connect, VERY simple and it is 100% reliable, I fitted on 8 years ago and it has worked perfectly ever since with all batteries remaining charged using the 2 x 80w solar panels.

Remembering to remove a fuse would not suit me..... fitting it and forgetting about it is what I like...... and there is even a little lght to tell you it is working well!

BatteryMaster every time - cannot give a stronger recommendations.

Dave


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## jiwawa (Jun 22, 2007)

I'm also in the camp that might (would!) forget to remove/replace a fuse so fit'n'forget for me. 

I was reading further on all this and found a warning that if you're likely to be sitting off-grid for long, and using your 12v equipment there may not be enough solar left over to charge the cab battery. 

We do tend to stay for maybe a week off-grid without moving. And when we do move, we don't usually travel very far. 

In the past there's always been solar power going to waste. But we've now got electric bikes so would be charging up 2x600w batteries from time to time. 

But I guess that would happen so seldom that we would just need to take the van for a drive to counteract that. 

I suppose my main need is when it's lying idle, not being used at all. And at the moment our has batteries are well-stocked by the solar so the cab battery should be looked after OK. 

Thanks all, for the input.


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## 747 (Oct 2, 2009)

JWW said:


> I'm also in the camp that might (would!) forget to remove/replace a fuse so fit'n'forget for me.
> 
> *I was reading further on all this and found a warning that if you're likely to be sitting off-grid for long, and using your 12v equipment there may not be enough solar left over to charge the cab battery. *
> 
> ...


You seem overly paranoid to me. We are never ON grid. The only time I am likely to plug in the hookup cable is on our driveway so the Mrs can use the Hoover in the van. We have spent around 90 nights away so far. None of it on hookup.

I have a 100 watt fixed panel on the roof and I carry a freestanding 90 watt panel in the garage for long spells of bad weather. I have used the second panel about 4 times. That is when we have been stationary for long periods on C&CC THS. If we were wilding, I could leave the second panel at home because it is good manners to move on every couple of days at most. The alternator does the rest. We will continue into the Winter months without problem.


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## Pudsey_Bear (Sep 25, 2008)

I'm not certain how, but I'm pretty sure a relay could be used to break the connection when the ignition is turned on, making the fuse method redundant.

I just hate paying high prices for fancy boxes with very little in them.


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## jiwawa (Jun 22, 2007)

747 - that's good to know I'm just being paranoid (really!)

I've never been able to get my head round electrics. 

Certainly, in the 2 years we spent mostly off-grid we'd few problems with our current setup, but I was unaware that the cab battery wasn't being charged. With a lot more standing, not being used and not on EHU, I think a battery master or similar would be a great asset. 

Thanks for all the help.


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## 747 (Oct 2, 2009)

Don't worry, it is common amongst motorhome owners to always opt for the most expensive option. :grin2:

If you were to go with the cheap option (as promoted by Kev) all you need to do is fit a switch in one of the spare slots on your dash. Get one with a red LED so that it is illuminated when the van battery is being charged (the circuit is made). You should not forget to switch it off and it has the advantage of looking like an extra alarm is fitted. :wink2:

Simples.

Another option would be to buy a new Burstner Elegance and fit a solar panel and Schaudt Regulator ........ the cost? Around £90,000. >


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## jiwawa (Jun 22, 2007)

....when you put it like that....;-)


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## Pudsey_Bear (Sep 25, 2008)

747 said:


> Don't worry, it is common amongst motorhome owners to always opt for the most expensive option. :grin2:
> 
> If you were to go with the cheap option (as promoted by Kev) all you need to do is fit a switch in one of the spare slots on your dash. Get one with a red LED so that it is illuminated when the van battery is being charged (the circuit is made). You should not forget to switch it off and it has the advantage of looking like an extra alarm is fitted. :wink2:
> 
> ...


I fit a alarm LED, which flashed different patterns, I put it right in you eye line as you get in so I never blew the fuse, but I used a ten way fuse box so had 9 spares anyway, think it cost £2 more than a two way


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