for the electricians amongst you

[Spike666]

Hey H.F. I have a trickle from my battery to 2 marine batteries.you need to use a marine/deep cycle battery I use 2 you dont have to... I run a generator that converts 12VDC to 110-115VAC it's like an invertor but I have the amps. I run a mig welder/grinders/saws/key machines/anything.

but I have a $7.00 relay and 2 $2.50 15Amp auto reset circut breakers and 10 G wire.mabey $10.00 for the wire. I have it set so when i turn on my headlights the switch opens(relay) and allows current to flow to my secondary batts. they are used for plows and such so you cant use equip when it isnt turned on. use the relay to turn on a trickle charge with ign on/headlights on/running lights on/ whatever fuse you adapt to.

[toomush2drink]

If you use this set up you shouldnt get any problems, i use this daily and run everything off of my 2nd battery including an sds hammer drill with no problems.Oh and thats with a 3500watt invertor.

[toomush2drink]

Sorry forgot the link http://cgi.ebay.co.uk/NEW-FULL-SPLIT-CHARGE-KIT-battery-winch-fridge-etc_W0QQitemZ110089721892QQihZ001QQcategoryZ108845QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

[fonzie123]

If you use this set up you shouldnt get any problems, i use this daily and run everything off of my 2nd battery including an sds hammer drill with no problems.Oh and thats with a 3500watt invertor.

you can run upto 75 amps using the way i said possibly more lik i said 2 batterys and an uprated alternator with 2 inline fuses fonzie123

[maxxed]

I would recommend any system that will maintain the battery for you. In my van I have a relay that is switched by the vehicle ignition and that in turn connects the booster pack I have in the back. In my jeep I just used a diode on a switched circuit, this works but not as well as the relay, due to voltage loss from the forward bias on the diode.

[maxxed]

Im no sparky, but I would have thought of paralleling the battery with the autos battery to charge off the alternator, and using a switch to cut it from the parallel when cutting keys. Does that make sense to the sparkies?

it makes sense and that is what any of the systems for the dual batteries do