After doing the same thing, only then did I realize how much money I saved at a local battery shop that was clearing out floor space. I got 4 40AH 'matched' batteries for $1/AH. They became the backbone of my power pack, and I ended up with almost double the storage for 1/3 less cost than the single 90AH battery recommended for my panel.
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I need a lawn-mowing room-mate!!
I talked to my alarm company technician friend last night and it sounds like I can have as many used 12v 7Ah batteries as I can take, probably gratis. He says they replace many each week. Some are actually worn out, but others are still good (e.g. replaced when one battery in a parallel string setup croaks before the others, but they replace the whole string). I'm meeting him at their shop this afternoon, where he says they have a milk crate full. Then I'll just need to set up a testing rig to figure out which ones still have life in them & measure their capacity. |
Woo, good news.
Testing shoudl be pretty simple, charge em up, put them on an inverter and time how long it takes to discharge them at ~1C. A 75W bulb would do nicely. |
That's the plan!
12v battery > DC-AC inverter > Kill-a-watt meter (to record time & watts used until inverter disconnected) > 110v load = good battery condition data |
Cast-off Electric Mower
Awesome...I hope to acquire an electric mower by similar means, and replacement batteries using tips from the other posters. Then I take one more step away from the prevailing petro-culture...:cool:
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Update: batteries won't be free! Sadly, my guy found out that someone already comes and buys the used batteries from his company on a regular basis. Pays 200 bucks for about 3 milk crates full (about $2 per 7 Ah 12v brick, by my estimate).
I'd happily pay that amount, but I'm not sure if my guy has the authority to sell them to me. Still investigating! |
and that guy probably takes them to the local swapmeet and resells for more
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Probably something like that. There aren't any swap meets around here that I know of, but I wouldn't be surprised if it's someone from out of town making the rounds of the alarm companies.
Anyway, I got one freebie used 12v/7Ah from my friend. Haven't tested it yet. One isn't really useful to me at all. I asked him to ask his boss if he would sell me some (I'd take a dozen for sure) at the same price he gets from the other guy. |
an embarrassment of lawnmowers
Mower #2 ....
OK, maybe I need to start another thread... This morning, there was another electric mower at the curb - literally at the neighbouring house to the one that chucked out the battery mower last week. This one's a small "corded" 110v AC machine, 7A rating. The handle is pretty bent, and has been repaired (not very well) a few times. I knocked on the door to make sure they were actually throwing it out: "Yup!" "Does the motor work?" "Yup -that handle is no good. Squashed it with the car." So I rolled it over to my place, plugged it in and cut the grass with it :). The handle definitely needs some patching/welding - it's work fatigued in several spots (not too far from breaking) and has been lightly patched up with tin & screws. And 7A might be small enough that the inverter at the shack will be able to fire it up so I can cut the grass there with the solar power setup. Gives me something to use while I'm sorting out the battery situation. |
At 7 Amps, you'd need 1000W inverter minimum to supply the constant current, and since that supply would be continous you're going to need heavy cabling to handle it. Drawing that constant current from a smaller battery may exceed its chemistry.
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