AGM Battery voltages

Gary, The AGM batteries I use are 12V 1150CCA, when fully charged they read 13.8V.

These are used in electric boats in Parallel/Series configurations for voltages of 24, 36, 48, 72 and 144. There are anywhere from 2 batteries up to 36 batteries depending on the run time and how many screws are required. I am not familiar with the Morningstar Controller. Are you using 6V due to size constraints? I think possibly the problem is the Controller is for 12/24/48V. Tying 2 6V in series = 12V could be the issue as the batteries are not seeing the full cycle from the charger and the charger is shutting down early. You are not specifying the app. Is it possible for you to move to 1, 12V batteries, or 2, different charger? I suspect the issues are more related to the batteries than the charger, the charger seems a bit more amps than required for the amount and size of batteries.

Hi Jim

Thanks for the comments.

The controller size was selected so as to allow for another set of PV panels at a later date.

I had intended to look at 12v batteries, but the cost didn't fit with the budget, so I retained the prior existing setup of 6v. The controller and PV system is setup for 24v.

Your comment on the AGM's being fully charged at 13.8v (27.6v on my system) against the normal 12.7v (25.4v) of a flooded lead acid would seem to fit in with what I am seeing.

Thanks

Gary, The one thing I failed to look at was the input voltage on the controller. I assumed it was 120VAC 60Hz. If you are using the charger input voltage from the PV. This I have no experience with yet. That I am about to embark on this mission starting tomorrow as many of our customers want to incorporate PV and WG on their boats to charge their battery banks while underway. So now I am seeing the bigger picture of what you are working on. You really need to look at larger capacity batteries. I understand costs. My cost from the MFG for the AGM batteries right now stands at $435.00 Ea. Put 36 of these in someone's boat and you get Really BIG Eyes looking back at you after our markup, installations costs. Throwing PV and WG and related systems. I can only imagine the costs to go through the upper atmosphere. Then, I expect to get really HUGE eyes!

The system that we use here is 230v 50hz, a household supply using a Victron 24v 3000va inverter to convert the battery outputs to AC. The controller controls the PV panels outputs with 24v feeding into the batteries

I would think that for boats, you would use wind generators for the main supply and PV for backup.

The specified fully charged open circuit voltage of AGM batteries varies a little with manufacturer. For this voltage to be valid, the battery must sit off-charge for a full day. Then, the difference between flooded and AGM is about .1 - .15V (with AGM being slightly higher. Heres a link to data for different LA types. I'd use it only as a guide, however, because some manufacturers are quite particular re the voltages that should be used.

Any state-of-charge indicator which uses voltage as the indicator is likely to be inaccurate.

Hi K Fry

Thanks for the comments. However, there wasn't any link included in your message.

Whoops:

http://www.bethandevans.com/pdf/Batterydata.pdf