Probably not. It's just the manufactures recommendation it be done monthly. 8 Trojan T105's for 24 volts...You're not kidding about expensive. I just bought another 10kW of panels from Santan because... solar.
Are you sure you need to equalize your batteries? Does the specific gravity indicate you should do so?
Thank you for digging this up. I'm frustrated with myself trying to understand all there is to know about batteries. I think what I've learned is that I have more panels (1600w) then I can use most days unless I load the inverter, while I don't have enough battery (450Ah) to get nowhere through the night to supply that load. I think I'll treat the batteries as a UPS, and run the PIP 2424 to do Solar/Util/Bat in the future, and start planning my next move.Actually, Trojan has more specific criteria for equalization based on SG. I have 8X T-1275 for 48V.
Trojan Battery Company is the worldwide technology expert for long-lasting deep-cycle batteries. In addition, we have become one of America's most successful independent battery manufacturers.www.trojanbattery.com
I. Specific Gravity Test (Flooded batteries only)
The readings should be at or above the factory specification of 1.277 +/- 0.007. If any specific gravity readings register low, then follow the steps below.
- Do not add water at this time.
- Fill and drain the hydrometer 2 to 4 times before pulling out a sample.
- There should be enough sample electrolyte in the hydrometer to completely support the float.
- Take a reading, record it, and return the electrolyte back to the cell.
- To check another cell, repeat the 3 steps above.
- Check all cells in the battery.
- Replace the vent caps and wipe off any electrolyte that might have been spilled.
- Correct the readings to 80º F (26.6º C):
• Add 0.004 to readings for every 10º F (5.6º C) above 80º F (26.6º C)
• Subtract 0.004 for every 10º (5.6º C) below 80º F (26.6º C)
- Compare the readings.
- Check the state of charge using Table 1 below.
If any specific gravity readings still register low then follow the steps below.
- Check and record voltage level(s).
- Put battery(s) on a complete charge.
- Take specific gravity readings again.
- Check voltage level(s).
- Perform equalization charge. Refer to the Equalizing section for the proper procedure.
- Take specific gravity readings again."
If you want to get the most out of your batteries, you really need to study both of those resources and develop a maintenance plan.
When I realized that 21v was super bad, I bumped that to 23.7, but that only is realistically a few hours with a load of 700 watts. I am thinking about getting a transfer switch so I can at least get more watts from the panels without running extension cords everywhere, and top the batteries off daily. (load/battery/util). That seems to be the best use of what I built.If you're flattening your batteries, you're going to kill them in a year. If you're cutting off after about 225Ah, then you'll get several years with proper maintenance.
"UPS mode" is probably better. If there are times of day where you can use their power to offset higher costs and charge them when power is cheaper, that makes sense too. You just shouldn't discharge them below 50% in any situation but an emergency.