Hi All.

I've just picked up 32 twelve [12] volt AGM Dynasty Batteries for $40 each, they weigh 105 lbs each and are 2 years old.

I will not be able to use the batteries for about 3 months. So the batteries are on three skids in my garage.

The batteries are at about 80-85% state of charge. They were part of a 640 set of batteries for backup power for servers from a now defunted Chicago area Dot Com company. There are ~300 still left for sale.

Does anyone have a simple suggestion as to how I can maintain a float charge of 13.62 volts/battery [2.27/cell] on these batteries until I am ready to install the batteries?

Thanks, Art.
Lawrence, Michigan.

I advise buying a decent bench type adjustable power supply - the type with analog meters is fine as long as you also own a digital volt meter (which you should also buy).

Just connect the power supply to several connected in parallel at a time - then move it to another set occasionally. Once a month even charging would be fine for these. Charging them continuously is really not required or even advised.

Hi,

As Christopher says, parallel several at a time for charging. In addition, I would group them an bunches as they will be used in the final system. If you are going to use them in a 48V system, group them in sets of 4, mark them and charge them togeather in those groups so every battery that will be in the same string is treated the same.

Ron

Hello Ron and Chris.

Thanks for the info.

FYI, the server team at my company will replacing it's server UPS batteries this week.

I've snagged these 12 volt batteries as well, 32 gel cells that weigh 70 lbs each. The batteries were installed in late 1999 in preparation for Y2K. The batteries have only been used for 24 hours each year since as part of annual disaster recovery exercises on our network servers.

Qustion, how can I harmonize my two banks of gel cell batteries? One set is made up of 32 12 volt 105 lb batteries, the other set will be made up of 32 12 volt 70 lb batteries?

Thanks, Art Toy
Lawrence, Michigan.

Hi Art,

How many volts is your system?

Hi Ron.

It is a 48 volt system using a Xantrex [Sorry about that Chris] SW5548 GTI inverter.

The 105 lb batteries are Dynasty 12 volt gel cells rated at 134 AH @ 20 hours.

The 70 lb batteries are Dynasty 12 volt gel cells rated at 100 AH @ 20 hours.

Hope that helps, Art.

Just wanted to correct myself.

The Dynasty batteries are AGMs, not gel cells.

-Art

Hi Art,

Before doing anything, I would number them and record their voltage. Then I would float charge them four in parallel at a time at 13.8V.

After about 4 days at 13.8V, I would measure the charge current of each battery and record it. I would then set the batteries asside while charging another parallel bank of four.

2 days after a group of four has been taken off of charge, I would measure and record the voltage. Then I would put a standard load such as a headlamp across each battery one at a time and measure and record the batteries voltage at 10 seconds and 5 minutes.

After you have recorded all of this data, the data will probably be fairly obvious on how consistant the condition of the batteries is. Group them is similar strings of 4 and just put them in parallel with your other bank. Take power out from opposite corners of the bank to keep wire losses to all the strings as close to the same as possable.

Hi Art,

Look here to see what I mean about taking power from opposite corners of the bank:
http://www.homepower.com/education/syspartshouse.cfm

The battery bank in the bottom of the schematic is similar to yours.

Hi Ron.

Like the headlamp idea.

I was wondering as to what can be used as a consistent standard reproducible low cost load.

Thanks, Art.