> On 14 Oct 2002 at 12:26, Tom Martin wrote: > > > I bought a load tester and checked all 24 of the Trojans and > > found no defective batteries. > > What kind is it? I've tried the cheap load testers (like the ones Harbor > Freight sells) and found that they couldn't identify even the crummiest > old batteries in the pack. I guess it's not enough of a load. > > David Roden > Akron OH USA
All those "cheap" load testers are probably for testing starter batteries, which is a whole different duty regime. The only way to test deep-cycle batteries is to deep cycle them. Need an appropriate resistor to run the batteries at a given amperage (depends on the battery - 25A, 75A, etc) and see how long they go at that amperage before they fall below a certain voltage (10.5V, 5.25V, etc). Also, bring some books to read, as testing this way takes a long time, although if you can test the whole pack at once, life gets simpler. For instance, in my last pack, I had a 6V US2300 battery (#4) lose a cell. I figured out which battery was causing my pack voltage to sag and do other funk by having the good luck of having a darkroom thermometer placed between the batteries, and noticing that it was reading rather warm after a 25-mile run. Keep in mind this was my first experience with finding a bad cell. I used my hydrometer's thermometer to find the bad cell. So sometime later, I finally got around to load testing the pack. #4 kept going and going fine in the voltage department with a 75A load for 45 minutes. By this time, I was beginning to wonder what was going on. However, in another 5 to 10 minutes, the battery went off the literal cliff, as the voltage in the bad cell went to 0, and I was down at 4-something volts. Yep, that works! Interesting thing is that I was able to revive that battery well enough with some long-term trickle charging for a year or two so that when I had some more batteries go bad in the pack at that point, it went back into the pack. By hook or crook, I managed t o get six years and 17-18000 miles out of that pack, and still always get back up my steep hill. It was a little short and a little slow sometimes, though :-( About the only thing one of those starter battery testers will tell you vis-a-vis a deep-cycle battery is the instantaneous resistance (how warm and well charged) of the battery. If the voltage nosedives under one of those testers before the smoke starts to pour out, the battery is (nearly) dead. Chuck Hursch Larkspur, CA www.geocities.com/nbeaa
