# another battery question



## jwinder (Mar 29, 2006)

hi 
would it be possible for some of you guys in the know to help with a bit of advice.
i have enough room in my leisure battery box to fit another battery which i intend to do, but i am going to charge it direct from the engine (not through the split charger) i have been given the combi relay to fit, so as not to drain the engine battery. but what i need to know is how long can i expect to get fom a 110 amp battery which will supply a lcd tv that uses a max of 38 watts
sorry for being a bit long winded but any help would be appreciated
cheers frank winder


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## Scotjimland (May 23, 2005)

Hi Frank.. I think you mean 3.8 amp ..?

For maximum life, a leisure battery shouldn't be drained more than about 50%, giving your 110 ah battery a useful capacity of 55a/h 

Divide the battery a/h by the TV current = aprox. 14.5 hrs 

Jim


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## sergeant (Jun 7, 2006)

Hi Frank, What you are proposing to do is an exact duplicate of the charging system already in place for your existing battery. All you need to do is place the second battery as close as possible to the first & connect + to + & - to -. If they are next to each other no fuse required but use 30a cable. The split charging system is more than capable of handling another leisure battery, Steve


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## DABurleigh (May 9, 2005)

I'm not sure whether Frank had this in mind, but some prefer keeping 2 leisure batteries isolated and using one for TV, say. Then when the TV fails, there is plenty left for more essential functions.

Dave


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## jwinder (Mar 29, 2006)

that is exactly right dave, i am using a cheap lcd tv from argos without the 240/12v transformer. 
i have modified it to run straight from 12v which is fine until somebody switches a light on or the water pump kicks in then i lose my sound. picture is still perfect but no sound until the voltage stabalises.
in my original thread i said 38 amp (max) sorry what i should have said was 38 watts (max).
so basicaly what i am trying to do is keep my power supply for my tv isolated from everything else but not have to mess about charging it or having to remember to charge it.
sorry to be so long winded
cheers frank winder


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## asprn (Feb 10, 2006)

jwinder said:


> ... long winded ..... frank winder


Surely it's winder by name, and........ :wink:

Morning. 

Dougie.


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## Scotjimland (May 23, 2005)

jwinder said:


> in my original thread i said 38 amp (max) sorry what i should have said was 38 watts (max).


Hi 
OK, that changes it a little, divide the watts by the voltage to get the amps 
that gives 3.16 amps 
We now have almost 18 hrs of corrie to suffer .. :lol: :lol:


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## sergeant (Jun 7, 2006)

Hi Frank, My apologies for not realising what you were trying to achieve. In that case do not connect your batteries together but just run a second cable from your existing split charge relay to that battery. No need for extra relays, Steve


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## DABurleigh (May 9, 2005)

Unless I misunderstand, that would connect the two leisure batteries with the engine off?


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## sergeant (Jun 7, 2006)

Hi Dave, Sorry obviously not making it clear. Provides two seperate leisure batteries, one for just the tv & the other for normal habitation purposes but both will be charged via the split charging system, Steve


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## DABurleigh (May 9, 2005)

It's been a long week. Still don't get it, Steve :-(

If Frank has a simple single relay, as in:
http://www.kampenwagen.co.uk/split charge relay.htm
then connecting a second leisure battery to pin 87 merely connects the two leisure batteries together. If one adds diodes to isolate, then the voltage drop means they aren't charged very well. We must be talking at cross purposes.

I think Frank wants fit-and-forget charging of all batteries, but with all 3 batteries isolated when engine off. I can't see how to do that with a single relay and no diodes (themselves undesirable).

Dave


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## eddievanbitz (May 1, 2005)

I am also confused! If a single relay is used, how will you get seperation?

I agree that the engine and leisure batteries will be in parallel when the engine is runing, but if you connect the new 2nd battery to the existing relay the two leisure batteries will be in parallel when the engine is switched off.

You would either need to split the supply with Diodes which as Dave said is undesirable due the the voltage drop across them or, better get a relay that has two poles, so the coil is energised in the normal way, the supply from the engine battery is common, but the "load" side of the contacts are seperated.

Allthough personally I would suggest hooking the batteries up in parallel and use the additional power all of the time. Power is like money, you can only spend it once

Cheers

Eddie


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