# Battery Advice Please



## Knauser (May 26, 2005)

Hi,

Our Knaus came with one Exide Multicraft 95aH battery for the leisure part of the vehicle. With blown-air heating, tv and satellite and a plethora of lighting I guess I'm going to be lucky to last a night without electric hookup during the winter.

I was going to fit a second 95aH leisure battery in parallel ( Knaus has space dedicated for two batteries ) but this doesn't seem to be a size of battery available in the UK, and Exide don't sell the Multicraft into the UK

I know the 'perfect' solution is to have two batteries the same size, but is there a techie here who knows if I'll be damaging a battery if I fit a 110aH as the second battery??

Thanks

Knauser


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## 89202 (May 16, 2005)

Hi,

Exide ( ex Sonnenschein ) produce batteries with " gel " filling. 
If you add a second, you must choice the same type and size, or you must install a " charging distributor " ( repartiteur de charge in french... )
No mix between " gel " and lead...

with kind regards,

duc


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## 93795 (May 1, 2005)

Hi Knauser, I think that you need to have 2 identical batteries, same type, same age, same capacity. So if you have sufficient space it would be best to install two 110 AH batteries and dipose/sell the other one.


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## olley (May 1, 2005)

Hi knauser the ideal is two identical batteries, but i don't see a technical reason why you cannot mix different amperage without a problem, as long as they are close in size, as yours are. 
Pity gt is not about as if there was a technical reason, he would soon let us know :lol: 

As has already been stated you must not mix different types.

Olley


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## 91929 (May 1, 2005)

Ignor what Olley says yes you can put different Ratted batteries in but one will K------r the other 

The lower amperage battery will tend to be charged out of the new one
Also assuming that the 95Ah battery is old and you fit a new battery of the same size the same will probably happen 

If you have rechargeable batteries for say a camera you are told NOT TO MIX types, or batteries with different states of charge

Fit two 110Ah if you have the space; but remember that they will take twice as long to recharge

Ex electrical lecturer


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## olley (May 1, 2005)

Hi pamnpete surely once the voltages have equalised no flow from one battery to the next will occour? and irrespective of amperages battery voltages are the same.

I am not a battery expert but if each battery is at the same voltage then there will be no current flow. please explain.

olley


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## 89008 (May 11, 2005)

I too only have one leisure battery and that does last over a weekend!  

If we cannot find a 'pair' of batteries would it be an idea to obtain a new 2nd battery and devise a method of charging both at the same time but incorporating a switch so that only one is used for power at any time. Then as that one is low on volts we could switch over to the 'full' one?
This would allow the use of miss-matched batteries and the need to only replace one at a time.
I'm sure I could use a split charging relay and a few diodes but perhaps someone has already done it and could share their knowhow? :roll:


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## 88905 (May 10, 2005)

State of charge is not the same as capacity.
The first is a measure of the then existing charge, the second is the measure of what the battery is capable of.
It is not ideal to mix two different ratings but if they are both near identical then little harm would be expected. However as abattery begins to deteriorate from day 1 then the disparity between old and new may be too great to be acceptable. 
If it were me i'd buy two new ones.If we can afford many thousands for a van then we should be able to afford a new pair of batteries when needed.

nobby


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## 91929 (May 1, 2005)

Well if you cant understand how two batteries of different capacities can charge & discharge through each other 

This is not the place nor do I have the time or patience to try and teach non believers the intricate technical details that I have learned over the past 55 years


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## olley (May 1, 2005)

PamNPete said:


> This is not the place nor do I have the time or patience to try and teach non believers the intricate technical details that I have learned over the past 55 years


If this isn't the place then what is this site all about?

Olley


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## Knauser (May 26, 2005)

hmmm ... thanks for the replies ... but I'm more confused than before.

Sounds like mixing a 95aH and something different is a nono.

So if I look to buy a pair of new batteries ... which to go for. They are mounted outside the van so gassing is not a problem.

Flooded, 'Sealed for Life', Gel, AGM ... which is best and most cost effective for motorhomes?

Knauser


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## 91929 (May 1, 2005)

take a looin the @[email protected] sectioin there are some leads to sites that explain things

Problem is I ahve losy all the links to a power failue (NO NOT a surge) that caused a fatal system failure

Took quite a long time to clean and reinstall things

Lots of files and links have been removed from my PC


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## RobinHood (May 19, 2005)

Knauser said:


> So if I look to buy a pair of new batteries ... which to go for. They are mounted outside the van so gassing is not a problem.
> 
> Flooded, 'Sealed for Life', Gel, AGM ... which is best and most cost effective for motorhomes?
> 
> Knauser


Recent post gave a good reference for this specific info

http://www.motorhomefacts.com/ftopic-9628.html&highlight=battery


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## DABurleigh (May 9, 2005)

Knauser,

Flooded.

http://www.sterling-power.com/htm/faqmain.htm

http://www.victronenergy.com/upload/documents/ElectricityonBoard_rev8_july2004.pdf

Dave


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## spykal (May 9, 2005)

Hi

Wiring a second battery of any sort so that it can be used to extend your "staying power" can be done by with a simple change over switch or just "quick clamp" battery clamps that you manually change. Your extra battery can be anything....a new 110 amp or just an old battery that has a bit of life left in it. Depending on how you use the van the arrangements for charging will need sorting too....but again it is not rocket science to independently charge two batteries of different sizes.....the problems start when you connect them into a bank of batteries.

I have posted my solution before but for what it is worth I repeat it again. It would not suit everyone but for us it is perfect........I run two separate 85 amp leisure batteries. One hooked into the normal power circuit..the living area , the other has the sole task of powering the TV, Digibox,Dvd, laptop and all the other "entertainment" stuff.....if we stay in one place too long and this battery gets used up we just do not get to watch TV anymore but we will still have no problem with the main leisure battery so we stay warm and well lit!
Charging is looked after by a combination of the on board charger , the altenator and a Ctek.....I manually switch between all three to suit...but the batteries are never used together or charged together in the same circuit.

Mike


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## Road_Runner_644 (May 9, 2005)

Hi All

Olley Said

"I am not a battery expert but if each battery is at the same voltage then there will be no current flow. please explain"

It's one of those that is a "gimme" to the techs.

I dont understand it either, and in the absence of George who was always right, we seem to be at a loose end on this one.

I've followed the advice, but can't grasp it.

Help 

Dave :?


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## DABurleigh (May 9, 2005)

"I am not a battery expert but if each battery is at the same voltage then there will be no current flow. please explain" 

Nothing to explain on that one; you are perfectly correct. No voltage difference, no current flow. However, what matters is the differing internal resistance and different charging efficiencies of the different batteries during charging, which makes both batteries less well charged for capacity and long life on a good multi-stage charger, plus how their terminal voltages are slightly different after charging and on discharge, causing current/ charge flow between the batteries. It all ends up over time as the total being less than the sum of the parts. The Victron reference explains the effect of different cells within a battery requiring periodic overcharging/ equalisation. Consider different batteries (different design or different age/use of same design) making this situation much worse, as the cell population is more diverse.

Obviously different composition batteries (gel, etc.) require different charging regimes anyway.

So, rather than have two good but different batteries connected together, personally for convenience I'd buy two cheap lead acids of the biggest capacity that would fit and connect them together, and if not that have the discipline to keep them manually switched or disconnected electrically but neither left in a discharged state.

Dave


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## olley (May 1, 2005)

Thanks dave, I wasn't trying to cause an argument, i just hate it when people say "you can't do this or that" I am the expert! and refuse to explain. 

I like to know the reasons why, so I can make my own mind up, experts are not always right, as we have found out to our cost over BSE ect.

Your explanation makes sense, thanks.

Olley


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## Knauser (May 26, 2005)

One last ( hopefully ) question ...

Is there any advantage/disadvantage on using a flooded sealed for life type??

Knauser


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## DABurleigh (May 9, 2005)

Knauser,

I would go flooded with checking caps. Your motorhome isn't a boat that can capsize (and if it did your batteries would be the least of your problems), and you will probably be using a charger that is more likely to generate some gassing than a car alternator.

Dave


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## RobinHood (May 19, 2005)

Actually, I did capsize one of my vans.

Quite dramatically and on a French Autoroute.

The 'domestic' battery was under the driver's seat, and leaking battery acid caused a certain amount of damage (to the van, to clothing, to me.....)

(You are correct, however - that fact was fairly low down on my list of problems at the time 8O 8O 8O 8O )


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## Road_Runner_644 (May 9, 2005)

Cheers for the post DAB Dave

I get the picture a bit more now.

I wonder if It throws a bit of a spoke in for my set up where I have a battery master connected from the leisure’s to the starter battery. The battery master is supposed to keep the starter battery behind the leisure batteries in voltage terms, but by the looks of the meter the voltage is pretty much the same when the ctek charger goes into "boil em for a bit" mode on the leisure batts.

The leisure batts are 2 x 110 and the starter a 85ah I think.

It's been on for about a year now, that’s the age for all three.

Dave


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## DABurleigh (May 9, 2005)

Your batteries will be fine with the Battery Master/ Ctek on leisure. The engine battery charge is limited to a small 1 Amp and flows only from the leisure battery.

My Victron charger has an independent 1A output for the engine battery, which effectively does the same, when on mains, as a Battery Master. 

Dave


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## Road_Runner_644 (May 9, 2005)

Cheers Dave

You know what i'm like for immediate solutions, the setup will now remain the same.

Dave


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