New Forklift Battery

FeensterFeenster Registered Users Posts: 9 ✭✭

I got delivery of a 48V forklift battery 5 weeks ago (Sunlight 750Ah (C5)). I also got a single 2V cell, just in case I need to replace one of the cells in the 48V battery.

It came from a company that deal with forklifts. They know nothing about solar charging, etc.

When it arrived the voltage reading was 49.7V. I didn’t check the sg readings.

4 weeks later (just last week) I got a reading of 49.6V (indicating a 75% charge). The sg readings were low around 1.200 (suggesting a charge of 60%). The Voc didn’t match the sg readings.

I checked the single cell. It gave a Voc of 2.12V (equivalent to 50.9V for a full set of 24 cells) but to my surprise there was no electrolyte. Upon further investigation I found that there was just acid at the bottom of the cell.

My assumption is this. The forklift company gets supplied with batteries that have the acid in the bottom. When they sell them on they add deionised water. Thus the s.g readings are from the top of the battery and they are going to be lower than one would normally want. Is this a correct assumption?

Now my main question is this. What do I do next? I plan on connecting the battery to the inverter/charger before the end of the week. I already used a small power supply (about 5 Amps for 4 or 5 hours) and brought the Voc up to 50.1V (which surprised me). Do I just connect the battery to the inverter/charger, allow the charger to do its daily charge or should I do something else? I have about 6kW of panels but at this time of year it can be end and miss with the weather.

Also, the battery is outside, under a canopy. Because of its size I couldn’t get it into the shed. The canopy is closed on 3 sides and I plan on closing the open side. Its on the north of the house. It will hardly go above 20 celsius in summer and below freezing in winter. Should I put insulation around the battery?


  • geosierranevadageosierranevada Registered Users Posts: 56 ✭✭✭

    The first thing I would do is contact the battery manufacturer and tell them what you have checked. Ask them what you should do next. 
    I would do an equalizing charge and keep checking sg. I would hope that they are not GB batteries, because their warranty is worthless.
    Mine lasted 3 years when I started losing cells. I then went with lifep04 batteries and now wonder why anyone would purchase lead acid they are 1000% better (but expensive). Good luck.

    Off grid for 20 years. 5KW panels, Trace sw4024, Bergy XL1 wind generator, 3 EG4 Lifep04 200amphr batteries  3 SQF 2 well pump, 12kw back up gen.  Not easy living in the wilderness but it keeps you busy
  • FeensterFeenster Registered Users Posts: 9 ✭✭
    The battery manufacturer hasn't got back to me. I will probably go with a full charge on Thursday. Just need to get the wiring done to the new set of batteries.
  • PhotowhitPhotowhit Solar Expert Posts: 5,976 ✭✭✭✭✭
     I then went with lifep04 batteries and now wonder why anyone would purchase lead acid they are 1000% better (but expensive). 
    Answered your own question. Just retiring my 12 year old 660ah forklift battery. $2525 delivered. LiFePo4 would be @$4500 to replace and require moving battery or heating battery in place. 
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former, 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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