Restoration Equalization

[CMcD]

Hello all

I am new to this forum, and I joined because I am in trouble. Briefly, we have been living off-grid for 17 years now. We have been slowly adding to and improving our solar installation. We have ample reserve in our system, both storage and PV. I have maintained the system well, including regular equalization charges to keep the lead plates clean.

My problem. Lightning stuck the ground. It did not actually strike anything electrical, but was so close that the surge blew my inverter. My wife and I both work from home, so we purchased the first inverter we could find in stock and available for immediate pick-up. We brought it home and I installed it right away, so my wife could get back to work. I later discovered that, as shipped, the low voltage cut-off is a default setting of 10.5 volt. Why a solar supplier would do this is beyond comprehension, when everybody knows this is ridiculously low. A convenient for Lithium Ion customers, but it destroys Lead Acid.

I have been doing an equalization charge to try and restore the batteries. It is working, slowly, getting better than yesterday. Before posting this, I did review the sticky postings in this section, but I still have a few questions.

I have read elsewhere that excessive equalization will damage the batteries (flooded). I am monitoring the charging, both specific gravity and temperature. I stop every so often, to let the batteries cool and fill the generator. The batteries were in reading as discharged, and are now in the low 12s. Do I just keep going? Am I right in assuming that if the specific gravity and temperature are low, I am not doing any damage?

Is there any advantage to breaking up the strings and moving the batteries around? I was thinking of stringing the best gravity readings together, and concentrating on them first. Then do the next group. I am assuming the smaller groups would get more benefit from the charge and recover faster.

Any other suggestions would be greatly appreciated. Thank you.

[PNjunction]

... I later discovered that, as shipped, the low voltage cut-off is a default setting of 10.5 volt. Why a solar supplier would do this is beyond comprehension, when everybody knows this is ridiculously low. A convenient for Lithium Ion customers, but it destroys Lead Acid.

I'll let the experienced floodie users comment, but this LVD is pretty common as a default. Sometimes 11.7v is seen. Especially on small portable inverters.

Why? Simplistically, 10.7v (at the C/20 rate) represents 100% discharge. While it will take a toll on cycle life, it won't *chemically damage* the battery. If one ran out of power, and needed the inverter for an emergency, they just may want to be able to take the battery to 100% discharge.

I call this the "dead-man switch" rather than a true LVD, which as you noted should be much higher under normal use.

For capacity testing, the inverter's dead-man switch of 10.7 can come in handy. Every so often I'll discharge at the C/20 rate until the inverter shuts off, and see how much time and current the battery was able to supply. 20 hours? Brand new and well charged. Only 5 hours until the inverter shuts off still using the C/20 discharge rate? Pretty much trash.

Don't mean to harp on it, but that voltage is normal. Raise it higher of course to suit your needs.

[littleharbor]

When your SOC is, say 75% and you hit your inverter with a heavy load, and surge, your batteries voltage will momentarily sag below 12 volts, depending on the health of your batteries , possibly way below 12 volts. once the surge has passed your batteries should rebound back to their actual voltage. If the inverters cutoff was too high it would cut off unnecessarily early.

[Matrix]

There is also a delay option in better inverters to allow for short heavy loads such as motor start-up surge. I have my inverter set to 22.9v with a 60 second delay, This prevents any unnecessary shutdowns when the well pump kicks on at 65% SOC

[CMcD]

Thank you for the replies. As I said, this was an emergency replacement. My old (really old) had a default of 11.2v, which I still raised to 12.0v. I guess with lithium coming on, the manufacturers have lowered the settings. Again, this is a convenience for lithium, but harms lead acid. People are going to change the LBCO (up or down) to their own preference anyways. Why not ship the product with a setting that causes no harm. Just my own private rant.

Like Matrix, I have always set my LBCO to 12.0v, but there is a delay so the pump can surge for a short period on startup.

In the meantime, I have a new question. What role does temperature play in equalization? For example, if you heat water, sugar will dissolve faster. As the batteries are coming back, the temperature is now starting to rise significantly. It is still nowhere near the danger zone. Should I let the temperature rise? Like the sugar example, will this help dissolve the sulfation? Or, should I open the door wide to let more cool air in? Is there an ideal temp I should be aiming for?

Thank you