battery condition

[windspeed]

my hawker powersafe gel batteries seem to be holding very little charge even though the volts are at 12.5 settled they go from full to low very quickly according to the controller

I am useing very little power from them

They are about 7 years old

has anyone got any ideas ....are they finished

Windspeed

[scottsAI]

Windspeed,

SLA are often called gell cells.

My 1kw UPS use 12v 12ah SLA. They last about 5 years.

Interestingly the ones cycled seem to last longer. Go figure.

For testing I keep a couple loose batteries (not in UPS). The weaker ones.

Noticed printed on the side: charge to 14.00v, cycled 14.50v.

So charged to 14.5v. after messing with the higher charging a couple times, battery seemed to have more AH, tested and confirmed went from 6ah-ish to just shy of 10ah? (Battery rated at 12ah)

Accidentally went to 15v recently, battery was warm, in the short term did not seem to harm it any. Did not hear bubbling noise... Still has 10ah capacity.

The UPS charges to 13.78 to 13.89 (measured several units, None make it to 14v). Based on the battery it should be charged to 14.5v if cycled.

Must have 4 or more brands of SLA, not all list the 14.5v. Your millage may vary.

Consider charging to a higher voltage, I think of it as a SLA equalizing charge.

Your batteries are failing, what do you have to loose?

I keep my old SLA, make good weights to hold things down when doing my wood working projects. Couple recently retired batteries will be tested out with the reverse charging recently posted here.

How has your Banki project come along?

Have fun,

Scott.

[zap]

If you haven't before now, go here and read.  If you don't have time to read the whole thing, read Part Two, BU35-"How to restore and prolong lead-based batteries".

I have a pair of pre-Hawker Powersafe 6vj9, Chloride Industrial Batteries Ltd., made in the UK in July of '96.  I got them when they were 10 years old, found by a dumpster, having sat there through at least 1 cold winter.

The place I found them had very high security, I couldn't even enter the offices without an escort, so I couldn't find out anything about their past life.  They showed around 12v when I got them home so I charged them up.  They showed 13.2v after a good, long rest and they've been hooked to the solar system ever since.

In the past year or so they've slowly started to drop to around 12.8v by morning without much of a load at all.  I plan on doing a careful 15v equalizing charge and see what happens.

There's some darn good info at batteryuniversity.

If you haven't read it, you might be interested in the discussion on sulphated vrla batteries a few down from this post.

Good luck.

[zeusmorg]

 It may be possible to partially rejuvenate these batteries by topping off the lost water.

 All lead acid batteries loose water content over time, the gell cells were the first to attempt to slow this process. over-charging causes the water to "boil off" slightly and the valves ing off gel cells is ometimes difficult at best,and impossible in some.

 It depends on the caps and valves used. Removal of some destroys the valves.

 If you can remove the caps and valves, top off only with distilled water. The topping off process is slow, as the water has to be absorbed by the gell substance,and air bubbles come out slowly. DO NOT OVERFILL! If you overfill, getting the acid mix right is impossible.

 It is up to you whether you attempt to fill them. I'VE HAD VERY LITTLE LUCK WITH THE SMALLER ONES I'VE TRIED ON. You have already gotten longer usage out of them than they were designed for.

[windspeed]

thanks scott

I think my batteries are actually agm but I did try higher charge 14.5 volts and they seem better......... can you equalise agm type batteries

about the banki

early trials showed output of 1.5 Amps at 12 volts

head is only 14" we hope to raise this to 20"

and usually the flow is higher.......... flume design is tricky

the dam is as much work as the gen but we are learning fast

thanks for your assistance

Windspeed

 

[scottsAI]

windspeed,

My thinking, if the battery is not serving your needs, experimenting has little risk to damaging it.

According to http://www.dcbattery.com/agmtech.html

"In addition, AGM technology batteries can be charged at normal lead-acid regulated charging voltages, therefore, it is not necessary to recalibrate charging systems or purchase special chargers."

I have an OPTIMA battery (AGM), have accidentally equalized it. Battery charger had a brain fart. Cooked it, 139F battery temp about 10 hours. Still works, not deep cycled since.

Please beware, the AGM does not have a way to add water, any electrolyte you loose is not replaceable.

Equalize as a last resort. I would charge and let it bubble noise for couple hours, still below full equalizing charge but may help things out. Considering charging to 14.5v seemed to help.

I would try reverse charging before I did a full equalizing charge on it.

Have fun,

Scott Beversdorf.