I am adding an IOTA 12V battery charger to my VW Westfalia camper-van to be powered when ever I plug into shore-power. As you know, the engine is in back and the batteries (chassis and house) are in front. I want to mount the charger in the engine compartment and connect to the positive and negative that are right close on the alternator on the engine. Question: will the alternator's charging current, while the engine is running, hurt the charger? Another way to ask the question: will the charger hurt the alternator and/or will the alternator hurt the charger?

 

The answer lies in the charger chosen. Most will care less about this situation, others might but since most chargers have more than ample voltage output a simple diode could be connected in series with it to prevent a worst case stuation of 12V feeding back into the charger. They make large blocking rectifiers that could be installed to prevent this specifically for the RV market when a dual battery setup is used.

Any mention of "reverse polarity protected" would be a good sign that it was totally protected from this situation. Some of our warehouse equipment is battery driven and the charger is an integral part of the device. It remains connected to the batteries at all times, only coming into play when it's plugged into a 120V outlet.

If in question hook one up and, without it pluged into the AC, see if any current trickles from the batteries back into the charger. If none does you're probably 100% safe.

 

Thanks so much for your info. Great site!
Q: do I put the amp-meter on the positive
or negative wire at the charger to check for "trickle?"

 

If I need a diode, what type do I get? Where? And where
do I install it?

 

Wouldn't metter which lead you checked for current onif it's flowing through the charger it's making a complete circle.

Most any RV supply store will have one of those giant islation rectifiers used to separate batteries, they're used such that you can run all your stuff off one battery without also draining the one used to start the engine,yet when the engine is started back up both get charged.