24v battery questions

[Eleanor]

The rest voltage is related to the concentration of the acid ie higher concentration gives a higher voltage. Standard Traction DIN EPzS cells have SG 1.28+ and the manufacturer of the cells we have at the moment says that they have to reach 2.13V/cell and SG 1.285 before shipping so 12.78V and 25.56V respectively for 12V and 24V. I've seen 2.14V for some cells after resting the bank for a few hours. The OPzS cells have SG 1.24 resulting in a rest voltage of around 2.07V.

[greenhouseparos]

still no joy with the manufacture. They also appear to have changed their web site recently and not much available info there.
again a good amount of sunshine with clouds in late afternoon and an evening voltage of 25.2v (at least their consistant)
thanks for all the info .
 

[rogeriko]

Do you have any meters that show charging amps during the daytime, thats what we need to know. If the batteries are full then nothing is ever going to change. The voltage should rise when the sun is out but if the cells are full then the charge controller will have disconnected the panels and the batteries are sitting on float charge. Does the controller have a display to tell you whats going on. Somewhere on the Sunlight webpage you can find a phone number for technical information, (210 624 5600) they are the only people who can explain what you need to know.

[greenhouseparos]

Roger
the charger has a display and shows the charging amps to be virtually 0. after an hours absorbing charge it spends the rest of the day on float.
i know that all the info points to charged batteries (even the charger manual has 25,2v as charged) but as this is all new to me i want to check.
I've called that no. and been given the mobile no. for their tech guy but he is not answering.

Still it is a good feeling after many years of planning many months of building and many hours of fretting to stand in the house that you have built with your own hands and to turn on a light that is indirectly powered by that huge fire ball in the sky.
15Th Feb is our moving in day. 

[billi]

When you start cycling/using  your battery ,the absorption time should be set longer than one hour

i have an  email contact  who replied fast recently   d.dervitsiotis---at--sunlight.gr

Billi

[rogeriko]

OK so NO PROBLEM the batteries are full. Next time it is full sun and charging amps are near 0 turn on inverter and plug in at LEAST 2kw of something, heater toaster kettle everything and you will see charge amps jump up to 60/80 Now we're talking...

[billi]

   yeah   its great to see the AMPS

[greenhouseparos]

have receved the operating manual for my batteies. it doesn't state the voltage for a fully charged cell but it does give the gravity For fully charged battery it should be 1,24 ± 0,01 at 20° C.
as i don't have hydrometer handy is there a way to convet this into voltage
Eleanor you say that an sg of 1.24 results in a rest voltage of 2.07. why does it? 

[Eleanor]

Paul, if they are OPzS cells the Open Circuit Voltage should be 2.08 ± 0.01V at 20°C. I'd get this piece of information confirmed by Sunlight. I don't know why the Instructions don't tend to include the OCV for this type of cell, it may be to do with the fact that they are intended for float use but it would still be useful information to have. Here are some Instructions for the same type of cell from another Manufacturer which state the OCV of 2.08V:

http://www.hbl.in/brochures%20pdf/OPzS%20Installation%20&%20Operating%20instructions.pdf

There is a formula you can use to calculate approximate OCV from the SG :

OCV = SG + 0.84

SG = 1.24 for a fully charged OPzS cell

So OCV = 1.24 + 0.84 = 2.08V

Hopefully you'll have a hydrometer soon