AGM battery advice

tplife wrote:
As a researcher by trade, I tend to over-research my purchases, but rarely pay more than I need to, nor get burned because of that habit. OPTIMA has great press because of so many satisfied users. They offer more batteries than just the smallest Blue-Top, and depending on application a Red- or Yellow- version may work better. Go to any SoCal car show and tell me what you see under so many hoods! They work well and are priced accordingly. There are several quality AGM manufacturers out there with varying prices, AH ratings, and applications. We have a 2008 OPTIMA that has done great service and is still working like new, kept charged with a $25 Schumacher float charger, just like on the $40K Harley and (SOLD) $45K BMW.

I would not be surprised if classic shows have batteries chosen by the looks, not by performance.
12 years ago I bought the cheapest golf-cart batteries I could find at Sam's. Still remember $46 a piece.
Having 24V coach I used the battery bank for welding. Not much, just for fun but it worked.
Usually for winter storage I would leave the batteries disconnected in storage. Often for 7 months. Still after 12 years they hold some charge, while using them for camping they would power my coach for 3 days with 1 liter of coffee made on battery power every morning.
For strange reasons batteries values are like airline fares.
You just never know when you can strike good deal.

Optimas are too low capacity for RV use and have also had quality issues after they were bought out. My Lifeline AGMs are still going strong since 2007. You really get what you pay for as far as bateries go.

In fact, I think it explains why I boiled off the Interstate batteries in the coach. I was letting the coach, plugged into shore power, charge the batteries, and apparently that's not a good idea, as the "floating" charge point is too high.
thanks again.

smkettner, thanks, that's a very useful site.

ticki2, you may be right, I'm only stating what they told me. When you hook up the batteries in series you double the voltage but the current available remains the same. They say it's 230 amp hours (at 77 degrees) and you divide that by the 20 hour industry rule (where THAT came from, nobody seems to know:)
What part am I missing?

gitpicker2009 wrote:

Okay, so with the the two 12 vdc Interstate batteries that I had (the SRM27's that came with the Arctic Fox) I had 88 ampere/hours. That works out to about 4.4 amps/hour.
With the 2 6vdc batteries in series, it's offering 230 ampere/hours--- HUGE increase! That's 11.5 amps per hour before reaching the recharging point.

gitpicker

I could be wrong but I think you made an error in your comparison between the 6 and 12 volt batteires . The general rule is to not discharge below 50% . Your numbers on the 12v batteries are correct . With the 6v batteries they are 230AH total ( to make 12v ) so you have to take 50% for the usable AH's which is 115 AH divided by 20 = 5.75 AH . Still a gain but not quit 11.5 AH .

As a researcher by trade, I tend to over-research my purchases, but rarely pay more than I need to, nor get burned because of that habit. OPTIMA has great press because of so many satisfied users. They offer more batteries than just the smallest Blue-Top, and depending on application a Red- or Yellow- version may work better. Go to any SoCal car show and tell me what you see under so many hoods! They work well and are priced accordingly. There are several quality AGM manufacturers out there with varying prices, AH ratings, and applications. We have a 2008 OPTIMA that has done great service and is still working like new, kept charged with a $25 Schumacher float charger, just like on the $40K Harley and (SOLD) $45K BMW.

Guys, I did some research and spoke to the reps at Interstate Battery- learned a few things.
One: I'm switching from 2 12vdc batteries wired in parallel, to 2 6vdc golf cart batteries wired in series.
The Ampere/hour/discharge rate had me confused but now I've got it.
Since I'm not using the batteries to start an engine (other than the small Onan 2.5kw generator) the "cold cranking amp" rating is fairly unimportant. What MATTERS is the amount of current it can discharge over time. I never understood the "20 hour" rating thing they were doing but now I do:
If the battery is rated for 100 amp/hours that means you divide the 100 by the 20 our rating, and you get 5 amps per hour performance before you're reaching the point that you don't want to pass (Interstate says it's 10.8vdc)
Okay, so with the the two 12 vdc Interstate batteries that I had (the SRM27's that came with the Arctic Fox) I had 88 ampere/hours. That works out to about 4.4 amps/hour.
With the 2 6vdc batteries in series, it's offering 230 ampere/hours--- HUGE increase! That's 11.5 amps per hour before reaching the recharging point.
I have two choices the normal wet cell flooded types are only 140 each- pretty reasonable. The same battery in the AGM version is 300 each, but can last 12 years with virtually no service. I'm leaning towards the AGM version.
I just wanted to pass on the info I learned, hopefully it'll clear up some stuff for ya'll like it did for me.

anthony

I second the bestconverter.com / Universal Battery idea. I got 2 of the UB121000's about a year ago and they are awesome.