Battery Rejuvenation

Anyone who has batteries in their backup or solar power systems will eventually have a battery go bad. Can it be brought back to life?

Maybe. Of course you want to take good care of your batteries in the first place to put the dreaded day farther down the road.

Let’s start with lithium, briefly. The Lithium Ion or Li battery packs are usually made of scads of little cylindrical cells welded together. Lithium Iron Phosphate or LFP batteries tend to be larger “prismatic” blocks bolted together. Many Prius owners have gotten the dreaded “Get a new battery pack” light and sold their cars cheap when the problem was only a loose or corroded interconnection. On your home solar batteries, if possible, periodically check all the battery connections. A loose or corroded connection can provide reduce or no output. This goes for any kind of battery. I have shown you pictures of batteries damaged by hot, loose terminals.

These are LFP cells for a 300ah, 48 volt battery. They are equalizing in parallel prior to assembly and charge.

The biggest frustration you may run into with lithium batteries is an over-discharge. Lithium batteries can be severely damaged by running to extreme discharge. To prevent this, and overcharge, they have a Battery Management System or BMS. These can be external or internal. Let’s say you let the battery get low and then left it alone. While neglected it self-discharges further. Now you have a battery that will not charge or discharge! Oops. Pay attention, now, because even though you may not have lithium batteries in your home power system, you have them. Power tools, phone batteries or that drone that got stuck in a tree for a month…all lithium. I have bought old stock tool and phone batteries on ebay that would not charge. The trick is to open up the case and jump off the battery to get the voltage above the BMS threshold to operate. Use a battery of similar voltage. It usually only takes a few seconds. I have done this many times. If an individual cell goes bad in the battery you may need to replace it or have a pro shop handle it.

Keep the terminals clean and tight, or this can happen. Or worse.

Now on to lead acid batteries. Oh goodness, get on the internet and you will find people offering to sell their books of secrets for reviving dead batteries. Many of these tactics will work to a point, some provide only short term relief or even cause more damage.

I added up what the approximate retail value of my batteries would be if I replaced them all and was stunned to find it is around $80,000. I did not buy new or retail, so it wasn’t anywhere near that. Nonetheless, there are literally tons of batteries and some go bad, both in the solar system and in all my vehicles and farm equipment. It makes me sad to buy new batteries.

The internet guys will try to tell you that you can put some aspirin or epsom salts or EDTA in your battery and all will be well. Chemicals may provide a short term boost, but understand that the end is near. Some of them will have you dump out all the acid, rinse with distilled water, charge with distilled water, rinse again and refill with acid. Why? Stuff flakes off the plates and falls to the bottom of the battery, especially when you let the electrolyte get below the level of the plates. Maybe the bottom fills up. Maybe the stuff lodges between the plates. Cells short out and the battery dies. (Or it blows up! A friend with a pair of 2000 lb. batteries had a cell blow, probably from not keeping the water up.) Ok, in theory, thoroughly cleaning out a battery may help, but is this safe or practical? Two of my batteries weigh nearly 2000 lbs. EACH. Let’s see you dump those! A pro shop can remove the individual cells from that type of battery, so it can be done. (My friend is having the blown-up cell replaced.) A golf car battery weighs 62 lbs. and a person can handle that, but do you want to be struggling with a heavy battery while trying not to get acid on you? Then what do you do with all of the old lead-tainted acid?

Since it has gotten cool, I have had several batteries go bad. I’ve brought two back to service, have 2 more in process, showing promise. I’ve only bought one battery for a really bad one in one of the tractors. My method is to check the electrolyte and put the battery on a slow charge. A simple charger may work best. Some smart chargers, which are common these days, are too smart for their own good and may or may not even start if the battery is severely discharged. In that case, use jumpers from a good battery to convince the charger to start. Use the 2 Amp setting and no more. This will take time. 2 amps into a 200 amp/hour battery is over 4 days, for a GOOD battery. A bad one will take a while. Check the voltage from time to time. Make sure the battery isn’t getting hot. Using a higher charge rate or letting a smart charger do its thing nearly always ruins the battery. A 12v battery needs to spend some time above 15 volts to break through all the sulphation and get it back into the electrolyte. If you get it that high, put a load on it to see if it has some guts. If the voltage drops quickly under load, put on a modest sustainable load and run the battery down and start over. It may take several cycles.

A very expensive AGM battery being discharged. The blue box is an inexpensive load tester. A neat and orderly workplace is essential for safety and efficiency. Wish I had one.

My quickest refurb was a 14 ah motorcycle battery, which took less than a week. (a week is maddeningly long when you want to ride the “new” bike.) It had not been run in a couple of years and now has no trouble starting the bike. Another battery, an Outback RE, was killed twice by a solar owner and then died in my tractor. It came back and is working fine. I have another Outback I am trying to revive for the 3rd time. My biggest challenge of the moment is a $1200 agm battery that powers my boxcar solar lighting system. It had a cell go bad. I have gotten it to accept charge, but it is not to the point where it really has any guts. I am on day 3 of discharging it with a light bulb. I have high hopes.

A week to rejuvenate a battery seems like a lifetime when you want to ride.

The key ingredient is patience. If you crank the charging rate up, you are asking for trouble. If your smart charger has a rejuvenate button, don’t use it until you first go through a regular slow rate equalizing charge. Good luck.–Neal