QuestionQUESTION: I have a 1500 Amp-hour inverter battery used with a 1500VA power inverter. Recently, the summer heat evaporated a large amount of battery water and I didn't notice it until the battery began to fail and the level was well below minimum. I have now refilled the water, but I would like to be able to test the battery and see how badly it was damaged during the dry up. Since I don't know much about batteries, I would be glad if you could advise me. For instance, should the battery acid be replaced? If the battery is damaged, can it be refurbished at a reasonable cost or is there no choice but to replace it with a new one? Thanks.
ANSWER: With a modern lead-acid battery there is no way to refurbish or repair it; the best you can do is to recycle it, i.e. buy a new one and trade in the old one for the core charge. If you are doing this, keep in mind that a big battery like this is worth more than a standard automotive battery because it has a lot more lead in it, which is the only part that actually gets recycled. So, since most places sell these batteries outright (no core charge) you should get more than the standard $5.00 for the old one.
However, you may not have trashed the old one. This is a deep cycle battery; it is designed to be completely discharged and recharged a number of times without damage. The principal form of damage to any battery from repeated deep cycling is the accumulation of sulfate deposits on the plates. Each cell consists of two layers of plates, one positive and one negative, interleaved like a deck of cards when you shuffle them. They hang from the top of the cell and do not touch each other; the only connection between them is through the chemical reaction of the electrolyte (battery acid). When enough sulfate deposits form on the plates, they bridge the gaps between the plates, shorting out the cell. One or two shorted plates in a cell will not cause a lot of damage, but if you have some in each cell, the weakening of the batteries capacity can become a problem. So, you need to find out if you have done any serious damage. First, refill the cells with water. You should use distilled water if you can get it. All supermarkets carry distilled water in gallons for use in steam irons, which are not supposed to use tap water (I didn't know this until I was told, who reads the directions on an iron?). Never add acid to a battery after the initial fill when it is new; acid consists of sulfate ions suspended in water, when the water evaporates (which is what happened to you) the sulfur stays behind. And the last thing you need is more of it. After you refill the battery, let it sit for 24 hours, and then put it on the charger and keep an eye on it. You don't want to overcharge it, but you do want it completely charged up. Once it is charged, check the cells with a battery hydrometer. Any good auto parts store will have several types; if you can get one of the fancy ones with a thermometer attached to compensate for the ambient temperature, so much the better. the hydrometer will have a chart on it telling you how to interpret the readings that you get. Put the tube on the end of the hydrometer in the first cell of the battery, which should still be full, and draw up enough of the electrolyte to lift the little float in the hydrometer. Read the value on the float where the electrolyte crosses the scale, and then check it against the chart. Make sure that you put the electrolyte from each cell back into the cell that you got it from. If all six (or however many you have, 12V batteries have six cells) cells read in the good zone, then you should be OK. You will have to check the battery every day or two for a while to make sure that it maintains its' usefulness. If you get a cell that reads completely "bad," you will have to replace the battery. You could try and limp along with the bad cell, but you won't be able to trust the battery to have a charge whenever you need it. This type of battery will last a very long time if it is maintained properly, and proper maintenance consists mainly of topping it off with water when some evaporates, which it will do, no matter what.
Good luck.
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QUESTION: I bought a battery acid hydrometer and tested all the cells. Of the four 150 Ah batteries, I got the following readings:
1) 1.13-1.15
2) 1.15-1.18
3) 1.21-1.25
4) 1.20-1.27
Any suggestions based on these readings of what I should do? Do I need to dispose of cells 1 and 2 or might they still be usable?
ANSWER: Assuming that the cells are full of water, and they have spent some time on a smart charger and will not take any more charge, then I would say that the first two cells are shot. They may still be producing something close to 12.5 volts, but their capacity to deliver power (amperage) and the amount of power actually stored is much diminished. If this is something that you use a lot, or want to be able to depend on in a pinch, then they should be replaced.
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QUESTION: It seems that when I topped up the water, that I overfilled it somewhat. I filled it well above the Top Level line. Could that explain the low density readings, and the acid vapor smell that I have been noticing since then?
Answer It could. It's almost as important not to overfill as it is to keep it full. If you look into the fill holes, you will see that there is a little rim around the bottom with a slot cut across it. When the liquid rises to that level surface tension causes it to form a noticeable bulge in the hole. That's where you want to stop filling it. When you have the charger on it, the electrolyte will bubble. This can cause spattering of electrolyte, and that will cause the sharp smell that you noticed. Check this website: http://www.batterystuff.com/tutorial_battery.html , it has a lot of useful info.
