1.3 specific gravity?

andyrud

I just got off the phone with Interstate Batteries and they told me that the specific gravity of their golf cart batteries is 1.3.  That sounds high to me.  What do you think?  And why is it so high compared to other manufactures?  Any ideas?
Thanks in advance,
Andy R

vtmaps

Raising SG increases capacity, but shortens battery life.  In hot climates it is common to reduce SG because the heat alone increases capacity and shortens life.

--vtMaps

dropkick

I found my now week old Costco Interstates to be at 1.30 as well after initial charges to Interstate's recommended voltages (which also seem way too high and stink up the area something fierce!).  I slowly ran them down over the last 24 hours to sg 1.26 which by other standards isn't much but I know I sucked out 1.9KWh.  I'm probably going to drop the voltage to something less than 15.3V for the next charge as that just seems like a lot. Maybe not for the first few cycles tho, sort of a mini-EQ I guess.

grizzzman

Interstate have been idiots as far as getting the correct information to there customers. Interstate numbers are 2.41 volts per cell bulk. The 15.3 is a finish absorb after a full charge where amps are clamped at say 2% of C20 rate. Then the voltage is aloud to rise to 15.3 volts. You need a charge controller that is set up to do this correctly. If you want to know who built the batteries for Interstate just look up us battery charging specs on google.

MGar

in a book from 1922:
"A question which may be considered at this point is why in automobile, work a specific gravity of 1.280-1.300 is adopted for the electrolyte of a fully charged cell. There are several reasons. The voltage of a battery increases as the specific gravity goes up. Hence, with a higher density, a higher voltage can be obtained. If the density were increased beyond this point, the acid would attack the lead grids and the separators, and considerable corrosion would result. Another danger of high density is that of sulphation, as explained in a later chapter. Another factor which enters is the resistance of the electrolyte. It is desirable that this be as low as possible. If we should make resistance measurements on various mixtures of acid and water, we should find that with a small percentage of acid, the resistance is high. As the amount of acid is increased, the resistance will grow less up to a certain point. Beyond this point, the resistance will increase again as more acid is added to the mixture. The resistance is lowest when the acid forms 30% of the electrolyte. Thus, if the electrolyte is made too strong, the plates and also the separators will be attacked by the acid, and the resistance of the electrolyte will also increase. The voltage increases as the proportion of acid is increased, but the other factors limit the concentration. If the electrolyte is diluted, its resistance rises, and the amount of acid is insufficient to give much capacity. The density of 1.280-1.300 is therefore a compromise between the various factors mentioned above. " powerstream

jonr

It would be interesting to see discussion of exactly when it makes sense to dilute the acid and reduce 100% SOC SG.    If you have more capacity than you use, why not reduce SG and get longer life from the batteries?  We know that battery manufactures compete directly on AH capacity.   Battery life is more nebulous and may not be given enough weight by the marketing types.

30% acid (least resistance) would be a SG of about 1.220 (compare to a more common 1.265 to 1.300).  Evidently some applications go as low as 1.215.

http://www.giantbatteryco.com/GLOSSARY/Specific.Gravity-Industrial.Batteries.html

jmd

It’s been my experience that higher sq increases capacity, internal corrosion, freeze resistance and self discharge. On the other hand the lower lower the gravity the better as far as battery life goes. The really long life stationary flooded L A batteries all seem to have 1.125 to 1.250 gravity. Battery mfg build them hot to get the highest energy density per cubic foot, per pound and per dollar but definatly not per year of service or lifetime cost.

The best performing, longest lasting and most efficient choice for stationary off grid applications IMO are sealed tubular Gel 2 volt cells

known as OPzV cells . They are the perfect choice for off grid solar. Buy the right product once and be done with it. Of course one can ruin any battery by failing to recharge it, adding chemicals to it, severe over charging or extended extreme high temperatures.

BB.

Welcome to the forum Jim(?).

If you "jmd" and "gjim" are the same person--It would work better if you choose just one login name to use--That way we can have one discussion with "you".

-Bill

Niki

sorry about that, I’m an old codger just learning my way around your excellent forum.  Niki only from now forward.
4 kw solar, whisper 1500 32v  vintage Wincharger model 260 -1500w 40 KWH tubular 36 v 
6.6 kw OB 32 v inv,