Poor 8 D AGM battery life

[Durango318]

A little over two years ago I purchased three UPG brand 8 D AGM batteries. Two batteries are on an inverter and one is for the "house" circuit. The inverted bank shares a 45 amp "GO power!" brand GPC-45-MAX "smart charger", and house battery has another charger just like it for it's self. Up until recently all was working fine, but now all three batteries have fallen on their faces. During their life's they never got warm, never saw 11 volts, mostly recharged before they hit 11.5, they were recharged within a few hours and never sat a day discharged. The house battery had perhaps the least draw/discharge. They all had only about 35 cycles, the rest of their life was on charge then float. The chargers charge hard at first, but now as the voltage comes up quicker and go through the sequences sooner, like bulk, absorption and float.



Any ideas what went wrong? Too small a charger? lousy brand of battery? Anyone heard anything good about the VMAX XTR8D a USA made AGM?

 

[Scott Danforth]

11.5 volts is severely discharged. Running a battery that low often will kill it quickly

 

[KD4UPL]

I've never heard of that brand. I have seen some low cost 8D AGMs that said right on the battery "replace in 3 years."
Is your charger programmable? Do you have it set for the manufactures recommended charging parameters for Abosrb voltage and time, float voltage and time, etc? Do you have temperature compensation on your charger?
I would highly recommend Deka batteries from East Penn manufacturing (made in PA). I've installed over 100 of their batteries in various off grid homes and solar back-up power systems. So far the longest lasting set was a bank of 28 that went almost 8 years.

 

[bruceb58]

11.5 volts is severely discharged. Running a battery that low often will kill it quickly

11.5V is basically 100% discharged.

You should never discharge past 12.0V which is around 50% if you want your batteries to last.

 

[Durango318]

Well according to Deka's chart (if it was a Deka), you could discharge to 10.5 volts open circuit and you would be down to about 200 cycles. I had perhaps a few excursions to 11.5 under load and mostly well over 12. The house battery was treated far better and it's gone too. So this cant explain only 35 cycles and two years. I contacted a friend that got the same battery at about the same time. His is used as a standby with float charge and had not been used. He got concerned and tested it. No capacity. The clock is ticking fast from the time these thing are put together regardless of use, based on both of our experiences. No more Chinese batteries, half the cost at a quarter the life is no deal. Next time Deka, Trojan, Lifeline or VMAX batteries. Made in the USA.

 

[JoLin]

Well according to Deka's chart (if it was a Deka), you could discharge to 10.5 volts open circuit and you would be down to about 200 cycles..

Lifeline AGM batteries have similar stats. Surprised me when I looked it up- I wouldn't have thought they'd have that many cycles left (250-300) after a 100% discharge.

I have a pair of Lifeline Group 31 AGM's on my boat. One house, one starting that I alternate via the switch. They're going on their 6th year. My charger is an old Charles 2-bank unit that is original to the boat (1992) and has no 'smart' features. I use a portable smart charger to desulfate them once a year when I disconnect them for the winter. A Lifeline Group 31 costs as much as your off-brand 8D battery did (about $400).

I think your problem is that the cheapo batteries can't survive the discharges you subject them to. On the other hand I've never discharged below 12 volts, either. Wondering if your house bank shouldn't have a third battery to keep up with the demand?

My .02