Hello AllI have a 1990 Warrior on the 1 ton Toy chassis. I do not have a working generator and even if the old Tecumseh I do have ran (died 8 months ago) I wouldn't want to use it as it's smoke blowing rattletrap compared to new models out there. I also don't want to haul a portable and the fuel for it at that would be on the rack at the rear.So I'd like to beef up the coach battery capacity. The current battery is less than a year old and rated at 100 ah. I have a 4K W inverter it's hooked to and it will run a piece of med equipment I need for about 6 hours. I'd like 8-10 hrs. I thought of getting a small, sealed AGM battery that I could put inside the coach and connect it to the inverter too so that all 3 components would be wired together and the batteries would charge when driving. The smaller battery that I'v found is 35 AH. There seems to be a question among the people I've asked as to whether the smaller battery would just diminish the overall AH when I operated the coach from batteries only. So I thought that I could just connect the smaller battery to the inverter where the larger battery already is connected and everything would be happy and I'd get longer juice production.Can anyone give me an answer on this? Many,many thanks

It won't diminish capacity but it would be far better to get two new batteries that are identical, than to mix a smaller newer battery with a much older one.

Don is right, don't mix batteries because your efficiency will be greatly diminished.What I did with my rig might be of interest to you. My rig originally came equipped with a pair of 12V house batteries hooked up in parallel. After going thru two sets of 12V batteries, each set operated inefficiently after year #2, I replaced them with a pair of 6V batteries hooked up in series which operates so much better. I bought mine at Sam's club at an affordable price. Keep in mind that 6V batteries are bigger so your compartment needs to accommodate them.The trouble with 12V batteries in parallel is that one battery always drains faster than the other which then their combined voltage gets quickly diminished. Then the charger tends to over-charge the good one trying to wake up the weak one. That is why acid boil-overs are common with pairs of 12V batteries. The problem perpetuates when the weak battery won't take a full charge. Then everything goes into self-destruct mode with the charger constantly trying to charge up what can't be done.Two 6V batteries in series is wired like everything else that works on battery power, from flashlights to most every hand-held electronic device. Batteries in series drain in unison which utilizes their stored power much better. And in the case with 6V lead acid batteries in series, you get a much better recovery charge because they charge in unison.

Adding to Ron's informative post, even when the charger is off, the mischief continues. The stronger battery will attempt to charge the weaker one until it is dragged down to the weaker one's level.The extra discharging cycles will quickly degrade the good battery to equal the older one.

garyemunson wrote:Adding to Ron's informative post, even when the charger is off, the mischief continues. The stronger battery will attempt to charge the weaker one until it is dragged down to the weaker one's level.The extra discharging cycles will quickly degrade the good battery to equal the older one.Ah yes!

It's just like kids and dogs.....you put a good one in with a bad one and the good one always becomes bad, the bad one never becomes good. Batteries work on the same principal.

adding to coach battery capacity | Good Sam Community

ron_dittmer
Explorer II
Jul 20, 2017
garyemunson wrote:
Adding to Ron's informative post, even when the charger is off, the mischief continues. The stronger battery will attempt to charge the weaker one until it is dragged down to the weaker one's level.The extra discharging cycles will quickly degrade the good battery to equal the older one.
Ah yes!
garyemunson
Explorer II
Jul 20, 2017
Adding to Ron's informative post, even when the charger is off, the mischief continues. The stronger battery will attempt to charge the weaker one until it is dragged down to the weaker one's level.The extra discharging cycles will quickly degrade the good battery to equal the older one.
ron_dittmer
Explorer II
Jul 20, 2017
Don is right, don't mix batteries because your efficiency will be greatly diminished.

What I did with my rig might be of interest to you. My rig originally came equipped with a pair of 12V house batteries hooked up in parallel. After going thru two sets of 12V batteries, each set operated inefficiently after year #2, I replaced them with a pair of 6V batteries hooked up in series which operates so much better. I bought mine at Sam's club at an affordable price. Keep in mind that 6V batteries are bigger so your compartment needs to accommodate them.

The trouble with 12V batteries in parallel is that one battery always drains faster than the other which then their combined voltage gets quickly diminished. Then the charger tends to over-charge the good one trying to wake up the weak one. That is why acid boil-overs are common with pairs of 12V batteries. The problem perpetuates when the weak battery won't take a full charge. Then everything goes into self-destruct mode with the charger constantly trying to charge up what can't be done.

Two 6V batteries in series is wired like everything else that works on battery power, from flashlights to most every hand-held electronic device. Batteries in series drain in unison which utilizes their stored power much better. And in the case with 6V lead acid batteries in series, you get a much better recovery charge because they charge in unison.
pianotuna
Nomad III
Jul 20, 2017
It won't diminish capacity but it would be far better to get two new batteries that are identical, than to mix a smaller newer battery with a much older one.

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