Batt voltage rises w/o charge [RE-wrenches]

[bbassett at rockisland.com]

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Concordes are indeed valve regulated sealed lead acid batteries, and so 
are gel cells. Valve regulated just means that there is a pressure 
relief valve to allow some pressure build-up in the cell to promote a 
bit of recombination of gases within the cells. This is true of both gel 
cells and AGM cells, which make up the two common types of sealed lead 
acid batteries. Gel cells have, as the name implies, a gelled 
electrolyte. I believe that the electrolyte is gelled by adding a small 
amount of fumed silica, that is a fine powder with very large surface 
area. AGM stands for absorbed glass mat, where the electrolyte is 
immobilized because it's absorbed in a mat of very fine fiberglass. 
There is lots of discussion about the merits of each type. I get the 
impression that gels might have a bit longer cycle life, and that agm's 
are a bit more tolerant of higher voltage excursions. Also, the MK gel 
cells are electrolyte limited instead of active plate material limited. 
This means that you can fully discharge them and do no more damage than 
discharging most other batteries to 80% discharge, but their ultimate 
capacity, if not their usable capacity, is lower for the same size 
battery. That's also why they list 100% depth of discharge as a point in 
their cycle life charts. 

However, other than service factors, I think that quality of the 
manufacturer is probably the most important factor in the battery 
lifetime in relation to other comparable batteries. Both of the common 
manufacturers used in the solar biz these days, MK and Concorde are high 
quality batteries from what I've seen. There were some other sealed 
batteries used in the past that were pretty bad.

Brad
AEE 


Drake wrote:
> 
> 
> >
> >Just for the record, Concorde batteries are not gel cells.
> 
>  From their web site I see you are right.  They are valve regulated 
>  sealed 
> lead acid batteries.
> 
>
> 

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