fitting leisure battery charger/power supply

My ancient 92 trident does not have a charger onboard for leisure battery. I want to fit one that is powered from mains hook up and charges leisure battery. Can anybody explain in simple language why I can't use one of those CTEK tiny chargers as opposed to the big transformer style ones with fans?
Thanks.

Hi there,

I am not an electrician but:

1.  It will depend on how many Amps you are using from the Leisure battery.

2.  For light loads I can see no reason why a charger similar to this one cannot be hooked into the Leisure Battery circuit.

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It could be linked to the existing system via a switch that allowed the battery to be charged on an "Either/Or" basis (i.e. Either car alternator Or EHU but not both.)

We have managed to run the TV and lights (LEDs) for up to three days (with a couple of hours of heating per day) without any re-charging of our 65Ah leisure battery so the 3.8Amps available with this little charger would satisfy our usage for sure.  (i.e. available Amps in 24hrs is 91.2 Amps which is much more than we normally use.)

I'm sure that someone will come along with a circuit suggestion and/or a better alternative pretty soon, but hope this helps anyway.   

Best regards,
 

An onboard charger is normally capable of supplying sufficient current (say, 12 amps) to power your 12v systems, plus charge your battery, when you're on electric hook-up.
The small CTEK chargers do not have that capacity.

G


Dutto beat me to it!

A 5A ctec charger could provide 120AH in 24 hours. Much more than you are likely to need, although it does depend on what you are running. 
What are you running?