12V / 6V  245Ah  AGM  Recommended charging profile - Page 1
Forum section: electronics / general

author: JoeyG
author_rank: Regular Contributor
timestamp: March 10, 2022, 08:32:15 am
content: I am the new proud own of these batteries. Where can I find the recommend charging profile for these batteries.Are they different to Lithium / SLA and other batteries that have different charging profiles.THanks in advance.

author: Renate
author_rank: Super Contributor
timestamp: March 17, 2022, 07:40:10 pm
content: Huh? You've got "golf carts"? 2 x 6V batteries? I've been running 2 x 6V x 224Ah AGM for a few years now. During the summer I've got electrons running out my ears. At Xmas, I have to ration them.AGMs are good, but like all SLAs the problem is, "You can lead a horse to water, but you can't make them drink". I've seen as much as 60A go into my batteries (1/4 C) if they were discharged and I switched the truck alternator to them. Normally they have to just take the solar and 25A is about the peak that they want to take. Right now (12:36 local time), they are seeing 13.76V and are taking 2A. They will love to sip 2A, then 1A until the sun goes down. LiFePO4s are hogs, they will take what you give them.What can I say? Boost to 14.4, charge to 13.6, equalize to 14.8 (once a month, which is why solar controllers pick the 28th of the month so that February doesn't get short-changed).

author: edpalmer42
author_rank: Super Contributor
timestamp: March 17, 2022, 08:47:05 pm
content: You should be able to find all the charging info at the manufacturer's website.But in general, AGM charge profiles are a bit different from ordinary wet-cell lead-acid batteries and are a lot different from lithium batteries. Note that AGM (Absorbant Glass Mat) batteries are a type of SLA (Sealed Lead Acid) batteries so the terms are sometimes used interchangeably. Since you can't add water to AGM batteries, it's important to not overcharge them because they'll lose water. If you undercharge them, they'll sulfate. Both will reduce the battery's capacity and life. But the proper charge voltage is temperature-dependent so it's a real balancing act to get maximum life from the batteries. That's why you go back to the manufacturer to get all the numbers that apply to their particular batteries.Ed

author: floobydust
author_rank: Super Contributor
timestamp: March 17, 2022, 10:29:32 pm
content: Yes do get the manufacturer's specs for those particular batteries.There is no equalize phase for AGM, although no battery has perfectly identical cells and I could see a need for occasional mild overcharge to bring up the lesser cells, but it does shed water and shorten life.Typically tempCo is -5mV/°C/Cell, 14.4V bulk charge, but I do see lower float voltages spec'd ~13.5V instead of the usual 13.8V for flooded types.If the batteries are on a cold floor that can be a problem because of "cold feet" as I call it, the top of the battery can be warmer from convection air currents. There's many wive's tales about this, but I would put some thought into mounting them. It depends on the room and heating.

author: trobbins
author_rank: Frequent Contributor
timestamp: March 19, 2022, 12:43:25 am
content: Your use/discharge profile can also be important, so best to describe that in detail, as well as the charger you are using.