Charging Voltages

[geoffd]

I have a bank of 12 Hoppecke Solar Power 7 Batteries.  These provide 24 volt 1300 Ah at C120.  The bank is charged from an Outback VFX3024 Inverter/Charger fed from a 3kw Generator.

The original spec was to provide 3kw / day for 5 days to a 80 percent discharge.

They don't get anywhere near this, they give about 3kw / day for 2 days, and I think it might be the values I use to charge them.  Currently I have the Boost Charge set to 31.2 volts for 1 hour.

Does anyone know how I can calculate the correct values, there is nothig on this on the Hoppecke website and they have not responded to any of my emails.

Best wishes

Geoff

[wpowokal]

Geoff,

      While I am not familure with your batteries and checking their site crashes my computer, I did get their sola batteries are flooded lead acid, try reading this.

http://www.trojanbattery.com/customercare_batterymaint9.html

http://www.homepower.com/magazine/downloads.cfm

I run a 24v system and per Kw out of the inverter requires 50A (OK slightly less but for ease of adding), so 3 Kw/day is 150 amps. Therefore 2 days is 23% of battery capacity.

My batteries are flooded lead acid, I use around 32V max. as equalising voltage and maintain that for around 3 hours.

I don't believe 1 hour is adequate, but thats debatable and how often one equalises is also cause for creating an argument however I like to try for once a week but if it's two weeks thats fine also. If the batteries require any topping up from other than Re sources I usually do it weekly and go through to equalisation, thats how I arrive at 1 week intervals.  

Hope this helps

regards Allan

[Ungrounded Lightning Rod]

The original spec was to provide 3kw / day for 5 days to a 80 percent discharge.

They don't get anywhere near this, they give about 3kw / day for 2 days, and I think it might be the values I use to charge them.  Currently I have the Boost Charge set to 31.2 volts for 1 hour.

That sounds like they need an equalization charge.

[Nando]

1300 amphour times 28 volts is 36 KWH

If you are charging 3KW for one hour that is 3KWH.

To attain the 36 KWH charge using a 3 KW generator, you will need a minimum of 36 KWH/3KWH = 12 hours of constant charge plus the additional time needed for the charging efficiency which could go as high as 30 % additional time.

You need equalize periodically but not continually or the bank will not last.

Equalization should be done if a deep discharge has been set on the bank.

Try to keep the charge above 45 % and the equalization will be minimized and maybe done once every 8 charging cycles ( you should have the a good DVM that can read up to millivolts) and keep records, as well as, the electrolyte conditions -- this will allow you to prolong the life of the battery bank.

There are good web sites with detailed battery info.

Regards

Nando

[geoffd]

Thanks everyone.

The system is newly installed, but I have not done an equalisation charge yet.  I will give it a go.

Cheers

Geoff

[troy]

Do you have an amphour meter.  This functions as a "gas gauge" for your battery pack.  Using voltage alone as an indication of battery charge gets tricky.  I use voltage plus periodic testing of electrolyte density (battery hygrometer).

Good luck and have fun!

troy

[geoffd]

No, the budget does not run to an Amp/Hour Meter yet, but it is on the wish list.

Does anyone have any recommendations as to the most cost effective.

Cheers

Geoff