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----- Original Message ----- From: "Richard Furniss" <[EMAIL PROTECTED]> To: "EV List" <[EMAIL PROTECTED]> Sent: Saturday, October 12, 2002 8:18 PM Subject: Battery Charger > Hi All; > > I have been helping my co-worker with the fleet of golf carts we have, > about 20 of them. The education process has been going slow, I just keep > nudging him in the right direction (in my opinion) on the care and feeding > of the batteries, it's the only thing there having a problem with. When the > cart would no longer last all day on a charge he would just put in a new set > of batteries, what I have found is that it's only one or two stinkers > causing the problem so we built up a surplus of, good, used batteries to > replace the stinkers with instead of replacing the whole pack. > > The problem that I'm finding now is an imbalance in the battery pack, > most of the chargers are Lester chargers and they taper to about one amp and > stay there until unplugged or timed out, my plan now is to do a equalization > charge as part of the regulator maintenance on the carts. > > Please correct me if the above strategies is incorrect or needs to be > changed. Your intention is good. > The charge and equalization charge needs to happen in six hours or less > during the regular maintenance, my first thought was a variac with a > isolation transformer, You can do much better than this. The current tapers off quickly with increasing battery voltage. What you want is a constant current source, not a taper charger. > then there was a bench top power supply it all ready > has isolation, Good choice if it has a constant current mode. > then there was putting the variac in front of the Lester > charger. Bad idea. Many Lester chargers have a ferroresonant transformer that tries to keep the voltage constant on the output. Turning down the input voltage has a very limited effect on the output. It is not linear and makes a terrible equalization source. > I like the idea of the bench power supply, that way I can dial in the > amps and set the voltage high and it will do the 36v and 48v carts, I have > looked but haven't found anything that fits, yet, I'm thinking 70v and 10 > amps. What do you guys think. You don't need 10 amps. 6 should do it. The excess current capacity of the 10 amp unit won't hurt anything if you keep it turned down to about 6 amps. 48 volts of golf cart battery should not go over 60 volts under charge. Some may so you might need 64 volts out of the power supply. You should add a voltage recorder. A DMM with an RS232 port and data logging software is available for under $100 on sale from Radio Shack. Dataq (www.dataq.com) had a free starter kit a while back would do the job. The starter kit has changed and they now supply a four channel module for $24.95 (http://www.dataq.com/194.htm). You need this view to see when equalization is over (when the voltage stops rising) to shut it down. If six hours has passed and the voltage is still rising, then the battery is not done equalizing and needs more time. Joe Smalley Rural Kitsap County WA Fiesta 48 volts NEDRA 48 volt street conversion record holder [EMAIL PROTECTED]
