Old AGM Lead-Acid Batteries...

Old 08-23-17, 06:41 PM
Thread Starter
Join Date: Aug 2017
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Question Old AGM Lead-Acid Batteries...

So, i got myself 4x 12v 18ah agm batteries that were "new" for about $10.
In the box the invoice says 2012.

When i hooked one up, it read 11.9 - 12v; i charged them via solar panel for about 30-40 minutes. reads 12.6v, disconnected panel, reads 12.4v.

standby voltage 13.4 - 13.8v cycle voltage 14.4 - 14.9v.

any idea if these are ok? should i attempt to refill them and then charge? these are for a solar system in my truck, so; if i refill them, would i guess gorilla glue work for resealing? wouldn't be a problem if they accidentally rolled around or something?

also, is it worth it to refill agm batteries? i can get old lead acid batteries for about $0.3/lb from where i work.

no idea what the min voltage should be / voltage i should never go under. i read 12.2v, but i'm having trouble finding straight answers.

one last question, got a mohoo ( made in china; blue model u see every where ), what voltage should i set for the float charging? 13.8 or 14.9?

basically a noob when it comes to lead acid batteries. reading material would be appreciated
Old 08-23-17, 08:12 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,675
Received 4,101 Upvotes on 3,683 Posts
Welcome to the forums.

Lead acid is one thing. AGM is another.

standby voltage 13.4 - 13.8v cycle voltage 14.4 - 14.9v.
These voltages are for charging.

If you use the battery in something like an alarm panel.... it would be charged at the standby voltage. In other words.... on continuous charging.

If it was a use like a kids "ride on" toy it would be charged at the cycle charge rate.In other words.... only charged after using.

Float charging would be 13.8vdc.

You mentioned "fill with water" and "AGM". As far as I know.... AGM batteries have never had filler caps. They are 100% sealed and should never be pried open. AGM= absorbed glass mat and doesn't use a liquid acid. I believe it's like a paste.

On a float charge it could take 6-8 hours to charge those batteries. They should be charged until they at least get to 13.8v and then checked. From what you've tried.... they sound ok.
Old 08-24-17, 04:46 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 28,148
Received 2,265 Upvotes on 2,018 Posts
I would charge the batteries with a proper mains powered battery charger and bring them up to full charge. Then check the battery voltage under a reasonable load. Even a bad battery can show a decent charge when not being used but it will crash (voltage will drop very low) when a load is applied.

Also, if your work is getting rid of old, bad batteries why do you think they will be good? Do they simply replace batteries even when they are good?
Old 08-24-17, 08:12 AM
Join Date: Sep 2013
Posts: 115
Upvotes: 0
Received 14 Upvotes on 11 Posts
2012 AGM batteries probably have a lot of life in them. My 2007 VWs are still using the original AGMs.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: