Wild_Bill has brought this to us :
An auxillary battery is generally connected to a battery isolator. The
isolator module allows charging of the aux battery while preventing the aux
load (winch) from depleting the vehicle's starting battery.

The wiring to the aux battery is 10ga minimum on a typical RV or other
vehicle, but should be heaver gage for longer runs, and include a fusible
link or circuit breaker at the source (isolator module).
Because a trailer connector is likely to be used, a heavy duty connector
should be installed.

I believe the isolator is generally selected to meet the charging demand of
the aux battery and the output capacity (amps) of the vehicle's alternator.

The output capacity for the load (Ah) may be increased by using two 6V high
capacity golf cart batteries instead of a typical 12V battery.

The most simple method of current limiting is a series LER (light emitting
resistor.. a bulb selected for the desired current level).

--
WB
.........


"Ignoramus17560" wrote in message
...
I need to install a 12v winch and a battery next to it, on a trailer.
This winch may need a huge amount of current.

I hope that this auxiliary battery will provide the power needed to
run the winch, however, I want it to be charged from the vehicle's
auxiliary 12v supply.

What concerns me is that when the winch is working, the battery may
demand a lot of current from the vehicle, and blow a fuse. At the same
time, after use, it may also require a lot of current with the same
result.

Ideally, I would like a current limiting device, of some kind, between
the vehicle and the wnich battery, that would limit current to some
low value, like 15 amps, happily supplying any amps under 15, but
automatically limiting the current to 15 amps only.

Is there anything of the sort, that I can purchase off-the-shelf?

I do realize that I can just wire a resistor in series, and I do have
a 1.4 ohm, 290 watt resistor and some others, but I was hoping for
something more elegant.

Thanks

i

Try the local Rec Vehicle agents. They do this sort of thing all the
time.

--
John G