AGM battery?

Glad we could help....yes, differing opinions are bound to happen now and then, it's not arm-twisting, it's just that each person has different experiences and knowledge....some people like Fords, some like Chevys...and oh I've heard of this new upstart named Stellantis....what's that about?

Originally posted by jato Interesting that for us in the north, the typical life span for a set of 6v golf cart batteries, with exceptional maintenance is 4 years.  That is on an older 36 volt system.  The same batteries, in the same golf carts, with the same maintenance program in the south will garner 6 years of longevity.  For the past 10 years, with Yamaha golf carts leading the way have gone to a 48 volt system using 6 eight volt batteries.  Longevity of these in the north is up to 5 years but the caveat of all this is that my basic 12v Interstate batteries are 10 years 5 months and 10 years 2 months old and still work very well for us as we normally boondock without the addition of solar panels or a generator.  So . . . .  when these decide to 'retire' I may very well replace with another pair of 12 volt batteries.

Let's see if we can unmuddy this a bit with a little deeper dive into lead acid battery performance. Fair warning, this is probably too nerdy of most folks.

There are two distinct impacts of temperature on lead acid batteries which we need to separate here. Both are related to the fact that elevated temperatures increase the rate of chemical reactions.

The two chemical reactions to keep track of in PbA batts are internal corrosion rates and charge/discharge reaction rates.

First, internal corrosion. You've got lead immersed in sulphuric acid, so corrosion is continuous in any PbA batt. The corrosion rate roughly doubles for every 8-10 degrees C. This corrosion is irreversible and means that the same batteries in hot climates will reach end of life sooner, everything else being equal.

Depending on what function the battery is designed for the basic room temperature corrosion rate shelf life can vary from a few years to 20 years of more. But all of them will be have their corrosion life reduced at higher temps.

The second chemical reaction is the charge/discharge reaction when the battery cycles. That goes slower when the battery is cold so in effect acts as an internal resistor in series with the battery voltage source. That means that the battery voltage drops faster when the battery is cold, and that effect increases with higher currents. But the capacity is still there, you just need to draw current more slowly or increase the battery temp to get it out. So this effect is reversible.

Like with corrosion the impact of temp on capacity is going to depend on the battery design, so this is only true when comparing indentical batteries at different temps.

Golf carts batteries are expected to provide a certain minimum amount of current and amp hours regardless of what their temperature is. So if it's cold they start out with less useful capacity to do that and appear to reach end of life sooner. But if you were to warm up those batteries they would must likely still work fine, and do so for longer than batteries which had say in a hot climate since day one.

So Jato you might want start a business to collect those well maintained 4 year old batteries in MI and take them to FL where they might get another year or two out if them.

For your rpod case, obviously you wouldn't be getting 10 years out if SLI batteries if you were cycling them heavily. But you are clearly very careful in managing discharge in your batteries.

So I don't think in your case you should go to deep cycle batteries. They wouldn't last as long because they have a different plate chemistry which allows for deeper and more frequent discharge at the expense of higher internal corrosion rates and self discharge rates. Typically this is done by alloying antimony with the lead in the positive battery plates.

For most of us that aren't quite as careful in managing battery discharge deep cycle batteries are more tolerant and can handle more cycled but at the expense if shorter shelf (corrosion) life.

For anyone interested in making a deeper dive into battery wherefores and whatnots check out the Battery University website. Lots (most?) Of what you see on the internet is just someone spouting their baseless opinions but Battery University is well grounded in the science and engineering. Good stuff.