Generator batteries
 

I am sure this subject has been covered before in another thread but I can't find it. Should the generator start and operate off of the truck batteries or coach batteries? Any thoughts/input welcomed.
MMM

My generator starts from the truck chassis batteries. I like it this way. I can boondock and use up my house batteries for a few days and when they get low I can start up the generator and charge them up. And, if I use up my house batteries I have no worry about being able to start up the generator. I know some use a volt meter to keep track of the house batteries and if they get low they can start the generator. But, wouldn't it be better to just use the truck batteries to start the generator? I don't know but I trust the company that built my truck to do it the best way, even though they seem to have succumbed to the terrible market and gone out of business.

Mine will start off of either. I think mine is off the truck batteries but if my truck batteries are low I can hold a switch and start off the house batteries.

I have a separate battery for the generator:reasoning, if the truck batteries go dead, I can use the battery charger (connected to the generator) to start the truck. If the generator battery goes dead, then I can jump off the truck batteries. I have thought about unifying the battery system, but for now, this is the way I have it.

Thanks everyone for the input. I like the idea of being able to start the generator even if I run the coach batteries down. I am assuming the voltage regulators will adjust accordingly if the truck and the generator are running at the same time since both will be charging the same set of batteries. I also like the idea of hooking them together via a solenoid and a switch just in case.
Next question: I have sized the battery box to hold three group 31 batteries. I am leaning toward Optima 31T yellow top batteries. Have any of you used these batteries or is there a better one available that is reasonably priced?
MMM

My Gen batteries are primarily powered by my house batteries. If for some reason my house batteries die, (and they did once) I have a switch that I hold while starting the Generator, this switch momentarily draws from the Truck batteries . The Gen then starts and charges everything up again, this seems like a good system IMO, G

I assume you're talking about the coach batteries? yellow tops aren't really a true deep cycle battery, and do NOT like being run down dead. In offroading, we have lots of experience with yellow & red tops, and an insider who did some work at the factory some years back found out the only difference in the 2 (red vs. yellow) was the warranty. Blue top optimas are their deep-cycle ones.

Thanks Eskimo,
You are correct.I did more research and the blue tops are what I need.
MMM

Are the AGM batteries as long life as a flooded battery? Seems to me I remember a battery guy saying the AGM (absorbed glass mat, gel type sealed ones like Optima) aren't as good durability as a flooded acid battery. He told me the only benefit to the AGM's are being able to mount it in any position since they won't spill. I'd talk to like an Interstate guy or something and see what he says. You'd think if they were as good, or better, all the big trucks would be using them? Or they'd use them in golf carts, wouldn't they? I think also if you use AGM batteries you need to use a different type of charger to charge them up?

Another note about how my coach was built. The truck chassis has the standard 3 12v truck batteries to start the engine and the generator. The coach has 2 12v deep cycle batteries to run all the house needs. Now, when those run down I can start the generator to charge them since the generator starts from the chassis batteries. But, the generator doesn't "actually" charge those 2 house batteries. There is an Iota charger/converter mounted in that storage bay. So, when the generator starts producing 120 volts a/c the charger kicks in and charges up those house batteries. There is also a 3 position battery round switch there. One position connects the house batteries to the house 12v wiring. One position connects the 3 chassis batteries to the house wiring. The middle position connects all 5 batteries together. So, if you're running the generator and you switch to the middle so all 5 batts are linked then that Iota charger charges them all. Or if you're on shore power, same thing. Or if the truck engine is running it'll charge all 5, since the truck engine alternator is charging the chassis batts any time the engine is running. What I like to do is set that switch for just the 2 house batteries when I'm shut down. That makes those two do some work and get some excercise. Then when they're low I either plug in or start the generator. By setting the switch tying them all together it won't use the house batts to start the motor, the wiring from that switch is just too small to allow enough amps to flow that way. I mostly use that switch so that when running down the road the engine will charge the house batts without turning on the generator. It took me awhile to figure out the best way to use that switch but I think it works pretty good for me this way. I think it's good to give all your batteries some excercise so doing it this way allows that. Often when I'm plugged in at a park I'll just unplug my Iota charger so the house batteries get some good use. Then when they're low I just plug the charger in and fill them up. I have a plug in thing to stick in the cigarette lighter in the coach to tell me what the house battery voltage is. I've also noticed that when the house batteries get kind of low the toilet valve thing stays open at the end of the flush. Silly thing but that's what I've noticed.

Now Bob you are making me think again. I like the idea of the three way switch. As for the AGM batteries, I really don't know much about them. Looks like I need to do a little more research. Thanks Michael

Just judging from size alone, I think the reserve capacity is lower than many of the flooded batteries found in coaches and trucks?