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VRLA AGM batteries
By C Via, Section Homebrewed Electricity Posted on Mon Aug 11, 2003 at 06:25:42 PM MST
charge controller set points for VRLA AGM 1440 AH batteries

Hi All,
New to the group and could use some advice.
I've just purchased a MSE 1440 battery pack.
It is 24 188 lbs VRLA AGM cells at 1440 amp at 8 hr. These are new in the crate
each cell checks between 2.09 to 2.1 volts now. What I need to know
is where to set my Trace charge controller for max. life for this type of
battery . I will use only about 2% daily. I have 6 80 watt and 3 100 watt
PhotoWatt panels for now and a small wind gen. 12 of the cells will be set for
12 volt and 12 for 24 volt.
Thanks for any help,
Caroll
Seminole County Fl.

VRLA AGM batteries | 4 comments (4 topical)

Re: VRLA AGM batteries (none / 0) (#1)
by Chuck on Tue Aug 12, 2003 at 09:02:17 AM MST

Caroll,

Look at my dairy on Battery connections for what I know about VRLA cells. I don't know if yours are similar to mine or not, so the specs I give may not be the same. Check with the manufacturer to be sure. It's too big an investment to guess.

Chuck

Re: VRLA AGM batteries (none / 0) (#3)
by Seth on Tue Aug 12, 2003 at 10:36:12 AM MST

i run my agm's at 14.4 bulk, 13.5V float.... no equalize.

And i have 4
Trying to move my solar pannels is fun.

Re: VRLA AGM batteries (none / 0) (#4)
by jubalearly on Tue Aug 12, 2003 at 12:31:16 PM MST

If these are the large 2.2v cells for tel-com use, they are probably lead/calcium batteries. That's a little bit different chemistry from the more commonly used deep cycle types. I mention this because you need to make sure that you are comparing recommendations for lead-calcium batteries. This type of battery is intended for float service & has high (IIRC) charge/discharge losses. They are not very efficient on charge or discharge with losses from 20-40%(IIRC, YMMV with age or condition) rather than the 10-20% losses for regular lead acid batteries. What you get in return is a much longer service life.

You don't lose much in efficiency if you minimize the amount of cycling (both number of cycles and % of capacity per cycle) which you often can do since these things are sold in fairly large AH capacity "sets". I don't think I'd bother with adding in a replacement cost in a life cycle calculation with these - 8yr. replacement schedules are common for wet cell lead acid batteries & should be considered.

If you use them properly & you can buy 5-6 times as much AH capacity for the same price as your next best alternative, and you have the space, I don't see how you can go wrong. You may well be ahead with much lower cost differentials, but it gets to be a case by case study........

Re: VRLA AGM batteries (none / 0) (#5)
by Chuck on Tue Aug 12, 2003 at 04:26:59 PM MST

Some good points jubalearly.

I don't really want to get into an efficiency dispute about the different types of batteries since I don't know a whole lot about it. However, I would like to point out a study done at Sandia Labs which indicates that battery efficiency is very dependant on state of charge. Depending on the state of charge, even a flooded lead acid battery can be 50% efficient, maybe worse. The study didn't deal with different types of batteries, but is a good read and an eye opener for anyone relying on batteries.

http://www.wind-sun.com/PDF_Files/batpapsteve.pdf

[ Parent ]

VRLA AGM batteries | 4 comments (4 topical)

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