Hello Cor, If it was known that the electrolyte was at the standard height in the cell is to the bottom of the fill neck when new. The electrolyte would read about 1.275 sg. If they were only about 2 weeks old from the factory. Sometimes I had them older than that which read 1.265 sg which self discharge a bit.
Just charge them until the specific does not raise any more and read the specific gravity again. When we did maintenance of a battery in a battery shop, we would first discharge each cell to about 1.200 sg which is 50% SOC. This is like a balance charge. We could do this two ways. If the battery has external links connecting the 2 volt cells, then we had a battery charger that could charge a single cell at the same time up to 2.216 volts which is actually the 100% SOC. Now if the battery does not have external lead links, you still test the voltage of each cell. We had two battery caps that had a hole drill in it for a long test lead from a volt meter to go into the cell and just touch the electrolyte. You will the voltage between the two cells which should read about 2.21 v for a 100% SOC cell. If you read the end cells to the battery post, this will read something like 1.3 volts on one end cell and 0.9v at the other. Adding these two voltages together would read 2.2 volts. This would be a good battery. This is call a cadmium cell test, because the long probes are cadmium coated just like the test leads of a meter. If you find if the voltage of that one cell is low, then while the test lead is held in that one low cell, charge the battery until that cell reads at or close to 2.21 to 2.22. What causes the difference in voltages, is that the charging voltage increases to 2.22 volts when warmer than 80 F. as the electrolyte cools, the electrolyte reading is lower. I use a battery cell tester that you can get from some auto parts store or battery shops. My is a rubber cover meter that is acid proof that reads 3 to 0 negative or 0 to 3 volts positive where the 0 is the center scale. It is made by the Cal-Van tool company, #545. It does not hurt to charge lead acid batteries voltage rating of 6.67 volts to about 7.75 volts. If you have a battery specific gravity tester, The electrolyte may read hot when we just mix acid into the water. Sulfuric acid reads 1.8 sg while water reads 1.0 sg. We mix 3 parts of acid to 5 parts of water which is 8 parts. Dividing (1.0 + 1.0 + 1.0 + 1.0 + 1.0 + 1.8 + 1.8 + 1.8) / 8 = 1.300 sg hot The 1.300 sg acid cooling down to 80 F. should become 1.277 sg for 100% SOC. Do not put 1.277 sg acid into a discharge battery. Lets say the battery is discharge to 50% SOC which is the battery plates chemistry. You put in 100% SOC electroyte and start charging the battery, this will raise the 1.277 sg higher which will raise the level of the electro lite. You first must discharge the cells in the battery to the specific gravity level lower than 1.277 sg. We normally discharge the battery until the highest cell reads lower to about 60 to 70% SOC. Then charge the battery to about 7.75 volts. Watch that the lowest voltage cell electrolyte does not go below the top of the plates. It is normal for the level to drop while discharging and raise during charging. If the level is just below the top of the plates, just add just a little water to just touch the plates and then charge the battery. The battery may reach 7.75 volts , but that may be the average of the three cells. One cell may be higher than 7.75 volts while another is below the 6.67 volts which is consider 100 % SOC. Keep charging that battery until the lowest cells reads 7.75 volts. What is happening is the higher cell that was reading 7.75 volts, it specific gravity will stop raising or is slow down, while the lowest cell will catch up. This will take many discharge and charges to do this. On one battery we had a cell that was 50% out of balance which normally cause by over watering. When watering try to get the electrolyte level to the same level. After watering a battery for five years and a person just puts in a 1/8 inch more than the next cell, the cell has more water in it, thus the specific gravity becomes lower through out time. The only problem is time, to bring the battery in balance. I built Lee Hart's shunts to install on the battery which will help keeping the cells in balance. Roland ----- Original Message ----- From: Cor van de Water via EV<mailto:[email protected]> To: Electric Vehicle Discussion List<mailto:[email protected]> Sent: Sunday, August 10, 2014 8:43 PM Subject: [EVDL] Flooded lead-acid ooopsie and how to correct best? OK, confession time and I need the wisdom from the list how to handle this mess I created. Last night I was in a hurry and wanted to quickly water my pack since that was needed. So, I grabbed the first of the 3 gallons that I keep for watering, filled the auto-shutoff jug and started going through my pack. Two things happened, the first made a mess and the second is more serious: Because some battery boxes are between the frame rails, there are cross-members that are above the filling caps of some batteries, making access difficult so they can only be filled with the jug at an angle. Apparently having the jug at an angle can defeat the auto-shutoff because the jug kept on burping slowly (I thought that this was because it was at an angle and not running as fast as with the other better accessible cells) until I suddenly heard an agitated hissing from the baking soda on the top of the battery, being eaten by the overflowing acid from that cell. Oops. I have put extra baking sode around that fill hole after closing it carefully and I have since bought a plastic syringe with which I will remove some fluid from that cell and store it in a plastic bottle until enough water has evaporated from that cell to put the acid back in without overflowing. Anyone have a rule of thumb how much I should remove? until it is at the same level as the other cells filled with the auto-shutoff jug? The second issue is more disastrous and I can't still understand how I got so confused: after I used the 3 gallons to fill all batteries under the bed (the remaining 6 under the hood had to wait till I bought more water) I put the jug back at the shelf where I keep it.... and found the 3 gallons that I had purchased a couple months ago and stored there, near the auto-shutoff jug. They had been behind some wood for a project, so I had missed them earlier and I realized that I had used *plain tap water* to fill my batteries, because that is what I had used the old gallon jugs for - to store an emergency stash of drinking water... Quick calculation revealed that each cell received about 250ml of tap water, because I could fill almost 3 golf cart batteries with each filling of the 2 liter jug. Of course that is just a few percent of the volume of the cell, but I am wondering if the unwanted minerals in the electrolyte will cause premature damage to the cells (they are now 2 years old, 9,000 miles and I was hoping to go at least 1 or 2 more years with them, getting 15 or 20k miles out...) Do I need to have them emptied and refilled with clean acid or would the dissolved minerals not matter much in the grande scheme of things? I need to weigh my options and decide which route to go next & how much cost and benefit each would have. Your wisdom is appreciated! Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com<http://www.proxim.com/> <http://www.proxim.com<http://www.proxim.com/>> Email: [email protected]<mailto:[email protected]> Private: http://www.cvandewater.info<http://www.cvandewater.info/> <http://www.cvandewater.infom<http://www.cvandewater.infom/>> Skype: cor_van_de_water Tel: +1 408 383 7626 -------------- next part -------------- An HTML attachment was scrubbed... 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