High performance/heavy duty alternator battery charging

I wanted to do the same thing. After getting totally confused, being it gets complicated fast. What I fell back on was what I'm trying to do. Which is...Charge the battery. Get a good understanding of that process and rest will fall into line. See http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&page=Battery-Charging

It's four in parallel
But you can't force feed your batteries
Even with dual alternators you are limited to a max voltage of about 14.2 bolts at the alternator when cold
As the engine and alternator warm up , the max voltage drops to about 13.6
Amps are determine by what the batteries will accept
For dead 12vs might accept 100 amps for a short period before tapering to 65 or less and continue to taper down as they charge up and the voltage and internal battery resistance rise

I'm an Electrical Engineer, let me see if this helps--
The limiting factor is the wire gauge. Batteries have internal resistance, wire has resistance. Beyond input voltage, your rate of charge becomes self-limited to a certain extent by the wire. At most, you will have a 4 volt difference between the alternator and the TC - this assumes fully dead TC batteries and a cold just-started alternator. Most factory truck-to-TC charging circuits are between 20-40amps. Given that you have multiple batteries, it would just simply take longer to charge them back up. The wire is the limiting factor - there's no regulator beyond what's on the alternator, and no other device besides a fuse to limit current.

A lot of us have multiple batteries (I have 6) and had the need for a better charging circuit. Like most, I've ran a dedicated 4ga hot and ground wire back to my TC batteries. I have put 100a breakers at both ends, the truck and the TC side, in the (hopefully) unlikely event of a short. A short will exceed the wire's rating and pop the breaker, because now you're going from 14.7v to 0---versus 14.7 to 10.5(dead TC batts).

That being said, the TC batteries have never popped the 100a breaker on either end. Now, if I upgraded to 2ga, 1ga, or even 0ga, it's entirely likely the 100a breaker could pop, because the wire can now support the higher current at that lower voltage differential.

Did you mean you have 4 in parallel (12 V) ? You will never get 4 in series (48 V) to charge as you would need ~ 52 V to charge them and the alternator may produce just over 14 V.

Wo.ody wrote:

Can you send too many amps (too hot so to speak) back into the battery series?

Not really, because you aren't force feeding "amps" in to the battery. The batteries will take only what they need. If the charging system is small, then the batteries simple accept the maximum they need for a longer period of time, thereby increasing the amount of time that it takes to charge the battery.

I think the dual alternators are an option.

Wo.ody wrote:
Sorry, Ben Franklin I'm not.

Late model Chevy DuraMax diesels have twin 125 amp alternators. If you want to create hp/hd alternator-to-TC camper battery charging then a few questions. As an example, lest say the TC has 4 each 12 volt by 200amp AGE in series.

How do you determine the max input amperage(less 15%) your system can handle?

What component in the electrics determine what amperage is sent to the TC battery series?

Can you send too many amps (too hot so to speak) back into the battery series?

Thanks

Woody

THere isn't a component that determines what amperage "is sent to the batteries." The batteries will draw whatever current the require in order to get charged.
As the charging system increases the voltage it puts out, this causes the batteries to draw whatever current they need, or that the charging system can put out, based on the size of the battery bank, the size of the charging system, the size of the wire/cable, and the length of the cable run.

The smaller the wire, the greater the voltage drop, hence the less current the batteries can draw through that wire.