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Golf Cart batteries / What I have learned
Larry wrote:
Jim wrote in ink.net: I'm upgrading my charger to a Xantrex "True Charge" 40 amp, 3 stage charger. The "Equalizer" function is important to maintain the batteries. The batteries only need 20A, so that leaves you with 20A of load current while the charger is on. The specs call for the 20 to charge a bank 100 to 400 amps. the 40 calls for 400 + I will have 440. I know it's ONLY 105 over . . .my thinking is to buy the right one the first time. The battery store guy should know better. He said two 6v 220 amp batteries will give 12v, 440 amps. 220 ampere-hours has nothing to do with 220 amps. Ampere-Hour is a measure of the stored energy in the battery. The "rating" only holds true for ONE load, the load that drains it in 20 hours (that's about standard in the battery biz). 11 amps will drain it in 20 hours, so that would be the "standard load" for this battery. The slower you discharge it, the more ampere-hours of energy it will produce, way beyond its rating. The FASTER you discharge it, more than 11 amps, the LESS its ampere-hour capacity is at that load. This is caused by chemistry and physics. The chemistry is the speed at which the acid can eat away at the soft lead plate's surface area. Quickly discharging it with a heavy load, the acid by the plate is quickly consumed into lead sulphate ions in suspension, blocking more acid from attacking the plate surface. So, it's not some incredible limit. Starting batteries overcome this problem with an incredible number of plates producing an incredible surface area that can produce an incredible instantaneous current.....but for a price. To keep the physical battery size, the plates have to be very thin. Their amp-hour rating is actually very low, as anyone who has been cranking a dead motor for a few minutes when the lights go out can attest. Deep discharge batteries use thick plates with lots of lead to eat and much more acid to eat them....at a slower rate, 20 hours standard. At 50A, and I'm only guessing as I don't have a chart in front of me but you can find them on the net, the AH rating of the 220 AH battery is probably about half, maybe a little more. Well, you get the picture. It's not a bottomless pit of power, actually kind of small for its weight. Nice charger, but you'll only see 40A charging them for a few minutes before the charge quickly tapers off to a safe charging level below 20A. If you never discharge them below specific gravity of 1.125, they'll last a long time. |
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