Charging 2 "house 6 volt" batteries on Vehicle's alternator. Good/bad/possible?

[AUTO360]

So, I bought 2 Trojan 105 6 volt batteries that I will run in a series for 12 volts. Main charging duties will be from a 20amp charger run by the generator. But....on days that involve mostly driving I was thinking of running a cable from my frame mounted 2nd starter battery (diesel) up to the Trojans and charging them with the alternator. Two concerns that I can think of. 1) Anyway to keep the alternator from over charging them? 2) Can a stock alternator even give them much of a charge?

[Rockfish]

Search on sailboats battery setups. I have a sailboat and I used to have a cranking battery and two 6v house bateries. This is common on boats. Resentely I change my house bats to 1 12v gel. I did not have to change anything on my set up. All my bateries get charged by the shore power( charger) and the alternator.

[doug720]

I have a motor home with 6 - 6v Trojan 145's and charge them with the stock system with no issues. I have had this same set up for almost 10 years and on other MH's prior to this one with the same results. I also have 6 solar panels and controller when parked.

Just connect them up and you're ready to go.

Doug

[kevint]

I have 2 T105s in my trailer that I want to be able to charge via the power connection on the 7 pin. I'll be interested in the responses you get.

One problem I've had with the T105s is minor spilling of electrolyte during backcountry travel. They were loosely constrained in the back of my pickup in a battery box. Maybe if they were strapped down tight I wouldn't have had a problem. I just spattered out a few teaspoons over four days of intermittent travel but it was still a pain to clean up. I hope your experience is better.

Other than that, I love them. They hold a lot of power.

[dwh]

The alternator won't overcharge them. The voltage regulator switches the alternator on and off to maintain a "12v bus" voltage of between (usually) 13.5v (switch the alternator on) to 14.5v (switch the alternator off). On and off, on and off. The end result is a bus voltage that hovers around 13.8v - 14v.

In fact, don't count on the alternator setup to actually get those batteries up to a full charge. At the voltage your "12v bus" is being held at by the voltage regulator - it could take a couple of long days of driving to get a pair of T-105s totally topped off.

But yea, use the alternator by all means. If you're driving anyway, might as well dump something into those batteries. You can always fire up the gen and the good charger to get them topped up later, and it will take less gen run time if they're part way there already from driving.

[AUTO360]

Cool, thanks dwh. Thats what I wanted to hear.

[dwh]

Also, if I were running (new) T-105s, I would definitely invest in Water Miser cell caps, which more or less turns the battery into a sealed battery - but that can also be opened to check the cells. Best of both worlds, if you ask me:

http://www.flowsystemsusa.com/water-miser-vent-cap.html

[olsen_karl]

But yea, use the alternator by all means. If you're driving anyway, might as well dump something into those batteries. You can always fire up the gen and the good charger to get them topped up later, and it will take less gen run time if they're part way there already from driving.

This is the approach I took, with a pair of 6V golf cart batteries in my truck camper, and with help from dwh in getting a beefy solenoid + wiring set up. I start each trip with fully-charged batteries (charge them on a standalone battery charger at home), and then use the "free" charge from the truck's alternator while driving to keep them somewhat replenished.

Thanks again to dwh for his assistance in getting my wiring set up correctly!

[AUTO360]

Hey Olsen K,

What type of solenoid to did you buy? Did you have a thread on how you set it up? I just ordered a 35amp charger from batterystuff.com and I will mount it in the van.

[dwh]

http://www.expeditionportal.com/foru...y-setup-for-50