Do you need to disconnect the battery when charging ? . I've a twin batt setup and its a pain to disconnect otherwise I would as a rule

Easier to disconnect and isolate alt wires to make sure?

bongo1 said:

Do you need to disconnect the battery when charging ? . I've a twin batt setup and its a pain to disconnect otherwise I would as a rule

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What does your hand book state, is the vehicle full of unprotected electronic control module’s, does the second battery have an isolated switch?

Other wise, No but only if the charger cuts off when the battery is fully charged (smart charger) which have been around for years now, if you have a reason and wish to leave the charger connected then use a ‘maintenance’ charger.
Isn’t the alternator charging while the battery connected.

The batteries don't know whether the charge is coming from the alternator or an external charger.

Intelligence can be a mixed blessing in battery chargers. Fortunately batteries - at least the ones likely to be fitted in cars - remain reassuringly dumb.

Usually it’s only a boost charger 30 Amps or above that could cause a problem, if it’s a trickle charger 4 amp
Or there abouts then you shouldn’t have a problem,

That's what i thought as its not got an ECU , nothing apart from a radio alternator and 2 batteries . its a 1996 DEF not a nice new one with electric gizmos . I have disconnected them to be safe . My idea was to charge via the Anderson socket on the seat box , then there would be no reason to remove seat base etc . Im thinking of getting a CTEC or similar and squeezing it in the battery box .
My problem is i don't do a lot of mileage and even less over xmas , so most ive done is only a 5min trip stop and return with heater heated rear window , and 4 /5 days between . Its not had a chance to charge , it started ok but slightly sluggish and the dual charge lights were showing low , . New alternator and 2x new batteries Main battery 100AH/900 other deep cycle .
So i think a maintenance charger is the way forward , Do i need one for each battery ????

No you can connect them together with a jump lead as long as they are both serviceable,
But don’t leave charger connected unless it’s plugged in as they often consume a small amount of power
And you will end up with two flat batteries,

I purchased a £52 Ctek XS 3600 charger must be 20 + years ago for my classic car which only gets used in the summer and when its sunny, a long while and never had any issues with it, the initial charge is low for this model of Ctek charger so was left charging for 48hours when connected to my disco 72Ah battery.

Now I also have for the last three years a maintenance charger £14 from Lidl which is very similar in performance which use I keep for the disco, if the disco is left unused for more than three weeks it won’t crank so out comes the Lidi charger for a quick boost over night, again no issues with this charger and works justas well as the expensive Ctek