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post #1 of 6 (permalink) Old 13-11-2011, 19:19 Thread Starter
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batteries,charging and all that

Hi all

I have read through hundreds of posts trying to find answers to the the few questions i have but of all the things i have read i'm even more confused .

I have an autosleeper symbol single 85hr batt under seat.

i want to replace this with two 110hr lucas xv premium batts, moving them to a box i have built under the side settee.

the questions i have,the charger i have fitted is a plug in systems.

which ouputs 13.8v, @ 12amp, looking through the posts, i would appear this will not be enough to fully charge new batts, i will need something like a 25amp, 3 stage charger is this correct?.

Also if i have two 110hr batteries, i can only use 110hr out of them without damaging them,if this is correct why are they sold as 110hr
and not 55hr?

i look forward to the answers


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post #2 of 6 (permalink) Old 13-11-2011, 20:02
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Yes, I would not recommend a 12A, constant 13.8V charger. 25A, 3 stage would be a minimum, but adequate, choice.

It depends on your definition of damage

Buy bog standard "leisure" lead acid batteries, and run them down each time until the lights go out, and their life will be considerably curtailed, especially if you don't fully recharge them immediately.

Run the same ones down to 50% of their capacity each time, and their life will be as good as they can be (notwithstanding other forms of battery abuse!).

Buy expensive traction batteries and they will be FAR more robust to running flat.

Which is why I'm a fan of battery monitors as they take out the guesswork and give you a remaining capacity gauge, akin to gauges for diesel, fresh water, waste water, etc.

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post #3 of 6 (permalink) Old 13-11-2011, 20:16
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Many batteries now sold quote the advised level of discharge and how many cycles they can perform before they can be expected to deteriorate in capacity....

550 cycles to 50% seems to be about the best and are only a very small premium in price over a battery with half the cycles.....

As for your charger , many vans will be running fine on a twin battery 13.8v charge....

But its better to be able to equalise them at around 14.4 to 14.8 v and benefit from the extra capacity they store as more fully charged and help extend the life of them .....

A 20 a charger should more than surfice as i dont believe in forcing more through without temperature control on hot continental days and it will do the job in 5 or 6 hours and you can switch back to your 13.8v van float charger all topped up .......
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post #4 of 6 (permalink) Old 17-11-2011, 12:23 Thread Starter
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Ok thanks for the info

So i have brought one of these

question is do i disconnect the existing charger & replace with this
one or just add this new one as well??

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post #5 of 6 (permalink) Old 17-11-2011, 16:44
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The charger you bought doesn't specify a voltage; as mentioned for most batteries 14.4V is an optimum charging voltage for the so called bulk stage. After a specified number of hours it will go down, usually to 13.8V.

Best to check the spec for your batteries.

As to the depth of discharge, the more/deeper you discharge, the more the batteries will suffer. A 50% discharge will give a number of cycles that the batteries can do this for, e.g. 500. If you discharge less each cycle, the number of cycles will increase, so it all depends on the depth of discharge. Less is better.

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post #6 of 6 (permalink) Old 17-11-2011, 18:02
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i have that charger and it runs to 14.7v then cuts to 13.7v float..

it gives the full 20a in its spec and i run my van charger in tandem which adds 4a as thats its rating plus what ever the solar is kicking out= 20 + 4 + solar output...

When it cuts to float i turn it off and leave the van charger on simply because although the float charge is 13.7 on either, run together when charged if both are left on you have double the float amperage thus double the watts and its too much to leave on constantly when fully charged....
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