Hi All.
My Hiace is a camper van. The battery that runs the camper portion is totally isolated from the running of the engine. The battery can only be charged by a battery charger when pluged in. I am considering connecting the battery to the alternator when the van is running, so I can not only charge the battery but also run the fridge. Would do this over taxing the alternator? Do I need a heavy duty alternator?
Thanks.
Sam

Yes, you can connect the battery to the alternator, and no you don't need to uprate the existing alternator.

Remember that the battery in a motor vehicle only has two purposes:

1. To start the engine

2. Provide power for the radio, lights etc when the engine is not running.

Whilst the engine is running, the battery serves no real purpose, as all power is now provided by the alternator.

Charging a battery from the alternator does not require much current, and I think the stock alternator in the Hiace is 70 amps.

What you do need for a camper set-up however is a battery isolator unit.

Have a look at this:

http://cgi.ebay.com/ebaymotors/120-AMP-Bat...sspagenameZWDVW

What this does is it electrically isolates your "camping" battery from the main vehicle battery, when the engine is not running. That way, you can draw power from the camping battery and not run the risk of flattening the main battery.
When the engine starts, it allows charging current to go to both batteries.

Thanks Hiace4x4 for the answer and the link. I can now make the mod with comforting thoughts that it would be OK. I did already buy a battery isolator, not the one you suggested but one that is like a switch. Made by the Brits. A green knob that you turn to connect/disconnect the battery. Which suits me fine since the battery is easily accessible. I just have to remember to turn the knob.

Yes, that will work, however after the first episode of you forgetting to turn the knob and having both batteries go flat, you will be heading out to buy the electronic isolator!

Trust me, seen this happen so many times before!

I heeded you warning Hiace4x4 and got myself a real battery isolator.
I want to tap into a wire that's hot only when the engine is running (not just by the key position to ON). The reason being I don't want the camper battery being charged when the alternator is not going which will drain the main batteries. This wire is for operating the solenoid relay only.

Any one knows?

There is NO wire that is live only when the engine is running. Not on a diesel Hiace anyway.

That is why you need the electronic isolator module.

It only allows the camper battery to be charged when the engine is running. When the engine is stopped,
it automatically isolates that battery from the main starting battery AND the alternator.

Trust me - get an electronic isolator and you will have your problem solved!

Your statement is so absolute that does leave rooms for questions. I know of one possibility – The switch/lock that prevents the gear shift from moving when the engine is not running. I am not certain how it works exactly, whether it is mechanical or electro-mechanical. If it is the latter, then there’s a wire I can tap into. I am again not certain if the wire (if there’s one) would carry enough current to activate the relay. It is too cold outside to fart around so I will leave this task until spring. I am certain there are wires that I can tap into only if I have a wiring diagram.

I can only work with what I got and that is an electro-magnetic relay. My resources here are limited being in such a remote place.

Regardless, thank you Hiace4x4 for your input.

The shift lock is usually operated by placing your foot on the brake pedal. This ensures the vehicle is stationary before selecting a gear. The switch on the brake pedal sends +12V to the solenoid which pulls a pin away from the shift lever.
Are you saying though that Toyota have improved on this and made the lock release automatically once the engine is running?
If they have, that's pretty techy! It may be relying on a feed from the alternator to tell the electronics that the engine is running.

I realise you are in a remote area but Ebay is your friend - I am sure there will be someone in CA who has an isolator and could post it to you - failing that, there are plenty of people in the USA who will post to CA.

Have a great Christmas!