Charging a 110AH Lead Acid Battery

[andya]

I have a 12v 110AH battery for camping.

I also have a car battery charger which was nice and affordable (�12)

However, the charger instructions recommend no more than 70AH for battery to be charged. Why is this? Surely a Lead Acid battery exhibits similar characteristics regardless of size

[chakka35]

A 110 AH battery draws more current from the charger than a 70 AH battery.  Plainly this would be too much for the charger you have.

[andya]

But isn't it constant? e.g. 4amp charger drops x volts over the battery at 4amps. I thought if you have big battery it just takes longer.

[Jay70]

The resistance of the battery will change as it's charging.  The resistance is directly proportional to the battery's level of charge hence it will draw most current when it when it is fully discharged.  So with your battery having such a large capacity the maximum current draw from your charger could exceed it's maximum rating if the battery were to be discharged to less than 36% of its capacity  i.e. 40Ah in the case of your battery. 

Also A leisure battery is designed to be able to withstand being discharged to a low level where as a car battery isn't even though they both consist of lead acid cells.  You would be better of using a high Ampage automatic charger  which also charges at a voltage that prevents 'gassing'.  I use one of these on my 80Ah camping battery and it has lasted for 6yr so far.  Hope this helps.