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Electric EZGO Electric EZ GO Marathon, Medalist, TXT and RXV. |
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01-01-2013, 11:01 PM | #1 |
Not Yet Wild
Join Date: Jan 2010
Location: Nor Cal
Posts: 25
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Battery math
So my battery pack is showing 40.4v a half hour after a full charge. I've read that 80% is as far as I should discharge the batteries for optimum life, which would be 32.32v? Please correct me if I'm wrong.
At this point I'm just hooking up the charger every couple of days or when I notice the performance start to lag, but I'd like to know when I should hook it up and why. I've done searches, but can't seem to find anything concrete other than the magic "80%". I don't have a state-of-charge meter, but do have a voltmeter. :p Possibly pertinent info: 1990 ez-go shuttle (pcx-954) 36v (6v x 6) Original "total charge" charger |
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01-01-2013, 11:50 PM | #2 |
......................
Join Date: Apr 2009
Location: FT Lauderdale FL.
Posts: 16,416
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Re: Battery math
You NEVER want to run your pack down below 50% 36.31 volts. A new pack of batteries is where you don't want to run the pack below 80% charged 37.49, for the first 20 charges, then after 20 charges then never below 50% charge 36.31.
32.32 is below 10% charge You can run your battery pack down below 10% capacity, but the number of times the pack will fully recover is reduced by the amount they are discharged. The Trojan battery company says you can get 5000 shallow discharge cycles from a battery or 700 deep discharges. Ideally you want to stay on the shallow side and recharge often, Keep in mind the cart is designed for golf. 100 minutes of peddle time easily does 18 holes. This is the expected run time for a stock golf cart. When you put bigger tires on them and bigger motors or increase the draw with lights, etc. run time will decrease. I hope this helps. |
01-01-2013, 11:57 PM | #3 |
Not Yet Wild
Join Date: Jan 2010
Location: Nor Cal
Posts: 25
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I get all that, and that's why I'm asking. What's the formula? I guess what I'm looking for specifically is what voltage equals a 100% discharge and why?
Thanks for the chart, that's the info I need, but I'd also like to understand how it was derived. :) |
01-02-2013, 12:06 AM | #4 |
Not Yet Wild
Join Date: Jan 2010
Location: Nor Cal
Posts: 25
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Also,according to the chart, a 10% discharge is only a 1% reduction in voltage?
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01-02-2013, 06:35 AM | #5 | |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: Battery math
Quote:
Plug the percentages, specific gravity, and voltages into Excel and plot your own chart, then try and derive a formula that approximates the curves. |
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01-02-2013, 12:22 PM | #6 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Battery math
I don't have the formula for the SoC vs Voltage curve, if there is one. (I think it is a plot from a lot of empirical testing and then rounded between averaged data points)
Here is a set of curves for a 12V battery, but you can divide or multiply the voltages on the left side to get whatever you want the scale voltages to be. Also, here is a chart showing projected life expectancy vs average SoC maintained. Golf Cart Batteries should be recharged after each use, no matter how slight. Also, to use the chart Rib posted, you have to let the batteries rest about 12 hours after the charger automatically shuts off to get an accurate SoC, or about 15 minutes after they have been used. A 3-5 minute ride after charging, followed by a 15 minute rest, will also get you on the chart, or close to it. YMMV, so you'll have to adjust ride time up or down for your cart and battery pack. |
01-02-2013, 12:30 PM | #7 |
Not Yet Wild
Join Date: Jan 2010
Location: Nor Cal
Posts: 25
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Huh. Alrighty then. Thanks for the info guys, I appreciate it. :)
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