09-01-11, 10:34 PM | #81 |
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I got mine from the local EV club guys who salvage parts from whatever they find. I would imagine you could find them on ebay quite easily. The one thing you must know is what mV drop the gauge is designed to use, and then you must get a matching shunt. Most are 50, 75, or 100mV drop shunts.
Here are a few auctions: Ammeter: Rectangle White Plastic Housing DC 0-200A Range Ammeter | eBay Shunt: Shunt Resistor for DC 200A 75mV Current Meter Ammeter | eBay Ammeter and shunt with a digital display (nice because bumps throw the analog one all over the place). 200V 200A DC Digital Blue LED Amp Volt Meter Shunt NEW | eBay
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09-02-11, 07:27 PM | #82 | |
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Quote:
1 meter for volts and amps, all you need, I think I'll buy 1 or 2. |
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09-03-11, 07:43 PM | #83 |
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Project finished.
Today I got the batteries snugged down & wedged in place, wire connections cleaned up (taped), the mower "hood" back on, and the digital voltage gauge installed. Ran into a slight snag with the gauge: it's hard -- OK, practically impossible -- to read an LED gauge in direct outside light! Didn't consider that when I bought it. So I couldn't mount it directly on the mower's motor cover, like I had been planning. The workaround for the problem: I made a deep "visor" for it, from a black plastic bottle, by cutting the bottom out and cutting the neck open enough to mount (tape) the gauge inside at that end. Looks like this now:
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09-03-11, 07:47 PM | #84 |
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Oh - and the gauge is not very accurate! It reads .2 volts lower than my multimeter.
No real surprise there (cheap junk!). It's not really a problem though, since it's pretty consistently .2v low across a range of voltages I tested. Even so, with this gauge installed, the batteries should enjoy a longer life -- free of battricide! I won't be accidentally over-discharging them. PS - the gauge can also be disconnected so it's not drawing power when the mower's not being used.
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09-03-11, 07:50 PM | #85 |
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Good stuff, keep us posted with updates as to how the batteries are doing.
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09-03-11, 10:04 PM | #86 |
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Will do! I plan to cut tomorrow, weather permitting.
Since I took on this mower project, I've also slightly reduced the amount of lawn needing to be cut, through a combination of creative landscaping and the acquisition of a back yard shed (to house said mower, among other things). The reduced run time means the life of the mower's jury-rigged battery pack should be extended a little bit more. Future plans for the yard are to reduce the amount of lawn even further. The best lawn is a minimal lawn, in my opinion!
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09-04-11, 12:05 PM | #87 |
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The LED gauge works great.
25 minutes running time today to cut the whole lawn saw the voltage eventually at ~11.1 indicated (~11.3 actual) under load by the time I was finished. (Though by the end, battery sag when starting up the motor was pretty bad @ ~9v, then quickly rising to ~11).
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09-15-11, 08:25 AM | #88 |
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My neighbour asked me last week how much it cost in electricity to run the battery mower.
Answer: less than 5 cents for 3 uses. ~8 months/season * ~3 mows/month = ~24 mows/season, or $0.40/season He said his gas mower uses ~1 litre of gasoline in 3 uses, or about $1.25 ~8 months/season * ~3 mows/month = ~24 mows/season, or $10.00/season EDIT: I did also remind him that batteries are "consumables" though, and if you're not getting them for free or cheap, you have to factor their replacement cost into the overall operating cost of an electric mower. ... then again, if you are getting them for free, and you get money back when you recycle them, you could possibly be in a net positive financial situation when it's all said and done!
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09-15-11, 09:27 AM | #89 |
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Haha, a net profit off free batteries. I laughed.
I estimate I use about 5 kWh per mow on average since I don't always mow the entire yard when I mow. 5 * 24 = 120 kWh per season for mowing. I pay about $0.12 per kWh. That gives me about $14.40 a season. I'm guessing I'd be over $100 per season if I was using gas. Thats a pretty decent savings.
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10-18-11, 03:31 PM | #90 |
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Post script:
Got a lead acid battery pack that just has enough capacity to do the job in warm weather? Well it won't quite have enough juice to do it when it gets colder out. Ask me how I know. (Also, there are some leaves down, which take more power to mulch along with cutting the grass.) So now I'm down to doing half the yard, recharging, then doing the other half later.
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