[Shop-talk] Hooking up a trickle charger to a truck with two batteries and a thermoswitch

[Randall]

> 1- Can I hook up a normal trickle charger to a truck that has 
> two batteries?  If so, how should I wire it?  I'm finding 
> confusing info on the web. 

Depends on how/why it has two batteries (which in turn determines how they
are wired).  Is it a pair of 6v batteries in series to make 12v?  Or a 12v
for starting plus an isolated 12v to power a camper or trailer?  Or a pair
of 12v batteries in parallel?  Or one of those screwy 12/24 volt setups that
normally runs 12v parallel but switches to 24v series for starting?

> 2- Is there a 120vac themo switch for a trucks block heater?  
> (so it only turns on the block heater if the outside temp is 
> below a certain temp?

Should be lots of choices available, as general purpose 120vac thermostats.
But make sure the set temperature can be set to the value you want, I found
a lot of them that cannot be set below freezing.

This one would need some mounting and wiring, but should do nicely
https://www.amazon.com/gp/product/B00OXPE8U6/ref=ask_ql_qh_dp_hza

>   (what would that temp ideally be?) 

How cold can it be before your truck doesn't want to start?  I might start
at freezing, then work up or down in 5 or 10 degree increments depending on
how easily it starts.

Just a thought: You said this truck won't be used very often, right?  You
might want to consider a manual switch that you can flip on a few hours
before you need the truck, rather than just heating it whenever it's cold.
When I was a kid, Dad had his wired to the front porch light, so on cold
mornings he could just flip the porch light switch on and it would be ready
to start by the time he finished his eggs & coffee.

-- Randall