New battery SG

hemmjo
hemmjo Solar Expert Posts: 90 ✭✭
in Solar Beginners Corner #1
I finally got everything up and running on the new installation here in the Doninican Republic

I highly recommend the Midnite Solar, HydroVolt hydrometer. Turns out the Brady that I got from NAWS is not only hard to read but it is also just wrong. Assuming the HydroVolt is correct of course. Which I am hoping it is!

We now have two systems here at the mission in different buildings. One has 4 - one year old InterState GC-2 6v batteries in 12v strings. The SG on these was 1.255+ or - a tiny bit when I arrived here with the new hydrometer. Tweaking the settings over these 3 weeks has brought all of the cells up to 1.265, so I am very pleased.

The new system has 4 Trace T-235 6v also in 12v strings. They have been running now for 3 days. The SG on these varies from 1.255-1.270. I would suspect a wiring issue but all of the connecting cables are the same and a lot of the variation is within the same batteries. I did an EQ cycle yesterday but did not get to ckeck the results yet. I will check this morning when the sun comes up to see if they are equal.

The cells were not filled equally when we got the batteries, close but not eiixact. I added at most 2 ounces of water to a few of the cells to bring them all up to level. I do not recall which cells I had to add water to.

Would this affect the SG of the cells? Is it normal for new batteries to have such variation between cells?

Thanks,
John
Two systems in the Dominican Republic  http://villagemountainmission.org/
installed Feb 2014 at 19.796189° -70.893594°, Classic 150 + WBJR, KISAE SW1210, MN Battery Monitor, IOTA DLS 55/IQ4,  4- Solar World 275w, 4-6v x 225ah Trace Batteries
installed Feb 2015 at 19.795733° -70.893372°, same components  as above
Honda PowerMate PC0497000, 7000/8750w generator - powers the well and chargers maybe once a week






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Comments

  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #2
    Starting out with a full charge and a light, easy EQ is fine for commissioning. It's going to take 25-50 cycles before the plates get formed evenly, until then you can expect erratic SG levels in the cells.

    Anytime you add water you can expect lower SG levels until the water is mixed with the electrolyte. It takes at least a complete absorb cycle to do that maybe more. While there is some thermal mixing the bulk is from the hydrogen / oxygen bubbles during gassing. That is why it's important to allow a good boil to break up the stratification. GC-2's are so short they are easy to do.

    Yes, you'v got to love the Hydro-volt hydrometer, great invention.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,654 admin
    #3
    With larger cells, adding a few Oz. of water is not going to materially affect the final SG readings (by more than a point to two).

    NAWS is now selling the Hydrovolt hydrometer too:

    http://www.solar-electric.com/midnite-solar-battery-hydrometer.html

    Remember to use take a couple draws of distilled water to rinse out the hydrometers after use... The insides can become sticky if the electrolyte if left to dry inside.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Surfpath
    Surfpath Solar Expert Posts: 468 ✭✭✭
    #4
    Blackcherry04 wrote: »
    Yes, you'v got to love the Hydro-volt hydrometer, great invention.

    Yup, I used one for the first time this weekend, what a joy compared to the old 'turkey baster'.

    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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