# Dual Battery System Questions



## Garcia (Mar 5, 2010)

Having just fitted a refillable Gaslow (tho I've not tested it yet!!).....I now turn my attention to the elecs....

I THINK my leisure battery is on the way out....it's still working but becoming a little erratic.
(eg at the weekend, we overnighted with no EHU . We were out all eve till midnight . Nothing left on in the van. Battery reading minimum volts when we got back. Wouldn't even retract the step! Yet after the drive and a sunny day it was 17.5 when we went out just before it got dark!).
So I'm keeping an eye on that...it's happened twice now tho worked fine at other times. We've no long trip planned till spring , so plenty of time to sort any prob.
I'm thinking if the battery is a "gonna" then it's the ideal time to replace with a 2 battery system . 
Done lots of reading of back posts on here and elsewhere. Looks straight forward. I've room for a battery box next to the passenger seat, though WHAT Hymer were thinking of when they installed so many inaccessable bolts to hold in the seat under which the battery lies. Overkill or what it strikes me!!

Couple of questions :
1. if the rest of the system remains the same, when I push the battery button on the Hymer control panel, will I be reading the v from the collective double bank or just reading the v from the battery in the original position??
2. Does a double system use and charge one battery first , then the other or is it just a collective "use" of the available power?
3. There's no room on the roof, but would I get any advantage from adding in a freestanding extra solar panel (notwithstanding the theft problem and finding a way thru to connect it.
4. The existing factory fitted panel seems to work fine.....how could I tell if it would cope with charging a 2 battery bank?
5. If I did get an extra panel , would I connect it to the first or second battery, or would it make no difference.
Garcia


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## listerdiesel (Aug 3, 2012)

Firstly, investigate that 17.5 volts immediately, that is WAY too much for a 12V battery.

If two batteries are in parallel then they will charge and discharge as a pair, as long as they are the same capacity, age and technology.

A bigger/extra solar panel will help charge the increased capacity.

Peter


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## 747 (Oct 2, 2009)

First of all it would help if you say which control unit your van has (eg EBL99).

As for your second solar panel, I used a freestanding solar panel for 4 years without it getting nicked and that included a lot of wildcamping. More recently I bought a second panel and occasionally had them both working together. There is nothing to stop you having a second panel either as it comes in handy when the Sun is hidden for days. You would need to think about storage for the second panel when not in use. Luckily I have never had a problem in this area.

My latest van has a fixed 100 watt panel on the roof and the second (freestanding) 90 watt panel has a plug on the end of its cable which I plug into a socket fitted to a junction box in a locker.


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## Garcia (Mar 5, 2010)

listerdiesel said:


> Firstly, investigate that 17.5 volts immediately, that is WAY too much for a 12V battery.


sorry ,my mistake.......it was 14.5.......just below the red max indicator

Garcia


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## Garcia (Mar 5, 2010)

747 said:


> First of all it would help if you say which control unit your van has (eg EBL99)


it is nindeed an EBL 99

GARCIA


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## pippin (Nov 15, 2007)

Just to reiterate what others have said.

If you have two batteries in parallel (which is how you should install them) then any load system, voltage monitoring meter, charging system whether solar or via mains or alternator split - they will simply regard the two batteries as one.

Yes - you will have double the capacity but it will take longer to charge them with the existing arrangements if they are at the limit of their current output.

However that is unlikely to be the case.

Is your solar system connected to the EBL99 front panel dedicated socket?


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## DABurleigh (May 9, 2005)

You need to establish whether you have a duff battery or a good battery with a constant load/ bad earth.

Easiest done with a multimeter, which is cheap from Maplins.

Dave


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## pippin (Nov 15, 2007)

"multimeter, which is cheap from Maplins"

What is not cheap is the years of education and experience on learning how to use one and more importantly how to interpret the results!


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## wakk44 (Jun 15, 2006)

First thoughts are; if uprating to a couple of leisure batteries in the habitation area make sure they are the sealed type and if necessary vented to the outside.

The 2 leisure batteries should be connected in parallel and so will charge equally from whichever charging source is used.

If the the Hymer control panel is the same analogue one as mine it will read the voltage of the leisure batteries one way and the engine battery the other.

Do you really need a second solar panel?They are excellent in the warmer months but not very efficient in winter.If the existing solar panel is wired directly to the ebl 99 unit then it will charge the leisure batteries first and then the engine battery,the same applies when on ehu.

One further point ,check the sliding switch on the ebl99 is set to the correct battery setting.My van was supplied with 2 gel batteries which have been replaced by 1 large sealed lead acid so the selector switch had to be altered accordingly as they run at slightly different voltages.Also check the solar regulator is set to the correct battery type.(if you have a separate one)

Finally I would start from scratch and get new leisure batteries,it can be frustrating messing around with duff batteries.


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## bigtwin (May 24, 2008)

pippin said:


> Yes - you will have double the capacity but it will take longer to charge them with the existing arrangements if they are at the limit of their current output.


If you have the same 'deficit' (I.e. are comparing 'like with like') it won't take any longer to charge them!

However, if you use twice as much power, it will take twice as long (roughly) to charge.


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## DABurleigh (May 9, 2005)

pippin said:


> "multimeter, which is cheap from Maplins"
> 
> What is not cheap is the years of education and experience on learning how to use one and more importantly how to interpret the results!


Ohm's Law is not exactly rocket science.

If the OP can't address their problem with a multimeter and the help of a forum, then as soon as anything goes wrong the only advice is stick it in the garage and pay whatever they say :-(

Dave


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## 747 (Oct 2, 2009)

I disagree DAB.

Rockets have complex electronic circuitry and the designers will use Ohms Law when designing it.

It is probably fair to say that it may not have a Leisure Battery but it probably has a starter battery somewhere. :lol:


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## pippin (Nov 15, 2007)

Bigtwin - you are of course perfectly correct!

However, I was working on the assumption that given more capacity then that would be used up more quickly - with gay abandon.


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