soc

petertearai · June 2011

Hi got the soc down to 88% over the weekend . Checked the sg reading 1240 to 1245

Looked up the sg charts I have, and find they all give a different answer to whot 1240 = in soc.
Question is there a definitive chart to use .

BB. · June 2011

Re: soc

Have you checked out the battery Manfacutuer's website/manual? Different brands/models of batteries can start out with different initial specific gravity fill.

I ran across this page on why different types of batteries have different starting s.g. fills... Is pretty interesting:

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 General 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.
...
Higher Gravity = vs Lower Gravity =
More capacity / Less capacity
Shorter life / Longer life
Higher momentary discharge rates / Lower momentary discharge rates
Less adaptable to "floating: operation / More adaptable to "floating" operation
More standing loss / Less standing loss

Add that you need to measure the temperature too of the electrolyte to compensate--you got lots of numbers to juggle.

As a first guess--I would estimate your top SG from the "fully charged" and "equalized" readings. And use the bottom SG of 1.110-1.130 for the zero charge battery.

-Bill

petertearai · June 2011

Re: soc

Thanks
Sg was 1280 when new / Rolls Surette solar 600 6 volt 450 ah at c20.

Problem for me is that being a weekend place the sg is usually around 1280 when i arrive. The next day after a charge witch ends in float, and battery monitor gets to 100% soc But sg will read 1260 to 1265.
An eq will get it back up to 1280.

Thanks Bill for the info.
Will check the rolls info I have. Unfortunately my hard copy is up at the weekend place.Rolls info needs a email to them to get info from them ( I don't know why).

petertearai · June 2011

Re: soc

Rolls info http://www.rollsbattery.com/content/battery-user-manual
100% =1.255 to 1.275
75% =1.215 to 1.235

Quite broad range but my values look ok

Vic · June 2011

Re: soc

It might seem a bit misleading, but most, if not all of Surrette Solar batteries have capacity speced as if they were shipped with 1.280 SG electrolyte, but really ship with 1.265 electrolyte.

EDIT: AND, the battery capacity difference represented by this 15 point reduction of SG is 5%. This is why my sigmatire line equates 4KS25s as 1280 AH instead of 1350 AH ... perhaps putting too fine a point on this, as capacity values are reduced as batteries age anyway.

Many manufacturers do not want to loose the specmanship game.

Vic

Joe_B · June 2011

Re: soc

Vic wrote: »

It might seem a bit misleading, but most, if not all of Surrette Solar batteries have capacity speced as if they were shipped with 1.280 SG electrolyte, but really ship with 1.265 electrolyte.

Many manufacturers do not want to loose the specmanship game.

Vic

I have found the same with my Trojan L16RE-B's, Trojan claims the S.G. should be 1.277 but its really like 1.265 as well. Cant trust anyone nowadays huh?

Cariboocoot · June 2011

Re: soc

These inaccurate SG readings: measured with which hydrometer at what temperature and altitude?

It's all relative, you see.

soc

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