Battery questions

hillside · January 2016

I'll try to be brief..
I bought 4 new batteries that don't seem to take a full charge. Tried a day's worth of charging using a regular charger at 2 amps.
On a new hydrometer tester, they all stayed at 1.225-1.250. None would show 1.275. These are 6 volt, supposedly deep cycle. But it doesn't state on the batteries "Deep Cycle", so, is there a way to actually tell if they are?
Should a new 6 volt battery, if fully charged, show more than 6.35 volts?
Battery co. rep says 1.225-1.250 is fully charged. True? Every battery I've ever owned for car, trucks, etc. showed 1.275 at full charge.
I think I'm being played here and in my location in the Caribbean I have limited sources to buy batteries.
Is there a way to tell if my charge controller is not up to par? With the batteries installed last week, I showed 27v. to the cc, and 27 at the batteries when in almost full sun.
(515 watts in panels, 24 volt system, Samlex 3000w. inverter)
I got 5 years out of the previous batteries but bought new ones when power levels dropped quickly, (and they read 1.275 for almost 5 yrs.)
Thanks

BB. · January 2016

What AH is your battery/battery bank (I.e., 6 volt @ 200 AH in two parallel strings for 400 AH battery bank)?

In general, I would suggest ~5% to 13% rate of charge for "normal charging"... And if you are trying to equalize, around 2.5% to 5% rate of charge (elevated charging voltage).

What is the charging voltage of the battery bank? 6.35 (12.7 volts for a 12 volt bank) is basically the "resting voltage" of a fully charged flooded cell lead acid battery bank.

You should be charging at (good minimum voltage) of 14.4 volts for normal charging. And if you are trying to equalize, somewhere around 14.8 to 15.0 volts (some industrial deep cycle batteries may need 15.5 volts or a bit more).

If the battery was fully charged--You should see ~14.4 to 15.0 volts on the terminals when charging. And if really near 14.8+ volts, you should see around 1% to 2% of bank capacity charging current (i.e., 400 AH => 4-8 amps) as the charging current (or less).

I agree, that your S.G. seems low. But could be "normal" for that mfg:

http://forum.solar-electric.com/discussion/comment/181142/#Comment_181142

Specific Gravity vs Applications
1.285 Heavily cycled batteries such as for forklifts (traction).
1.260 Automotive (SLI)
1.250 UPS – Standby with high momentary discharge current requirement.
1.215 Geral applications such as power utility and telephone.

As mentioned earlier, the specific gravity (spgr.) of a fully charged industrial battery, or traction battery, is generally 1.285, depending on the manufacturer and type. Some manufacturers use specific gravities as high as 1.320 in an attempt to gain additional Ah capacity, but at the cost of a shorter cycle life.

If you are trying to figure out a full charge SG reading (always a good idea for new batteries, and log the numbers over time), I would suggest a 5% rate of charge at ~14.75 volts and hold that voltage. You should see significant gassing, and check the SG every 30-60 minutes. When the SG (of all cells) stops rising--That is your 100% full number. Also watch battery temperature, you really do not want to get much over 110F (even 2.5% to 5.0% rate of charge can overheat a fully charged battery).

If your charging voltage is low, and/or you do not see any gassing, then the battery is probably not yet fully charged.

-Bill

mike95490 · January 2016

Some batteries in warm climates come with a "Tropical Acid Fill" which is less acidic to last longer in the warm climate, but it also de-rates the AH capacity.

hillside · January 2016

Thanks but at this time I'm dealing with the battery vendor over these questions:
1) with no labeling, is there a way to determine if a battery is deep cycle or not?
2) why did the old set of batteries (deep cycle, labeled as such) show 1.275 sg for almost 5 years, then drop to 1.225, and the "supposed" new ones will not go above 1.250? (I'm beginning to suspect they have been stored in tropical heat too long)
3) if these actually are starting batteries, shouldn't they read 1.275 after charging?

BB. · January 2016

Deep cycle batteries are supposed to have thicker plates--However, I am not sure you can really tell by just looking down the fill tube (perhaps somebody here can help).

Another possibility--Flooded cell lead acid batteries have fairly high self discharge rates... And should only be stored (at ~70F or less) for a maximum of 30 days--At that point, the battery(ies) should have been sold and placed into service, or put on a charger and recharged back to 100% SOC.

If these batteries have been sitting "on shelf" for 6 month, they probably have sulfated and will have low specific gravity/resting voltage/capacity.

-Bill

hillside · January 2016

thanks, BB, that is useful info. I suspect these batteries have sat around for some time.

littleharbor2 · January 2016

Another question comes to mind, What panels do you have and in what configuration? If you have 60 cell panels (not true 24 volt nominal) in parallel you wont be able to achieve high enough voltage to fully charge your batteries, especially in hot climates.

South Africa · January 2016

Is it not an option to use each batteries weight to try and determine if they are deep cycle or not?

vtmaps · January 2016

South Africa said:

Is it not an option to use each batteries weight to try and determine if they are deep cycle or not?

Not at all. Weight has more to do with capacity than with cycle life. Two batteries can have the same weight (and therefore similar capacity), but one battery has thin plates and more of them (starting battery) and the other has fewer, thicker plates (deep cycle battery).

--vtMaps

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