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| S. Heslop:
I found this real jumble of a thread on endless sphere. Any decent information on how to do anything is hard to find. I'm not a fan of the ES forums in general. http://endless-sphere.com/forums/viewtopic.php?f=14&t=26383&sid=a0ae404381381478ccb07127d6820426 I'd assume laptop batteries are adequate because a fair few people seem to be using them for electric bikes. But everyone seems to be using them now so the price of second hand batteries has really gone high. Looking at those hobbyking batteries linked, at 5Ah and £15 each, £60 worth (not far off what people are paying for the old laptop batteries) would make a 20Ah cell, which is pretty adequate. Plus it probably won't require all the fiddling to sort and test the cells. |
| vtsteam:
Sorry Steve, but that's 10AH for that money. You need one each of the 4S and a 3S (S stands for cells in series) to make up the 7S you need for the voltage your system was spec'd at (if I remember correctly). That's why I gave two listings -- one for 3S and one for 4S packs. In other words you connect a 4S and a 3S in series to make the equivalent of a 7S. It is still 5 AH total. You could hook two of those sets together in parallel to get 10ah -- so that's 4 batts together and your 60 quid. Used laptop cells might not have a full life or capacity left -- usually they don't, in my experience. 1 Lipo cell = 3.7 V nominal so 3S = 11.1 V nominal 4S = 14.8 V nominal 7S = 26 V nominal 10Ah still seems like a usable amount if your target consumption is 500 watts: 10 Ah * 26V = .26 kWh .26 kWh / 500 W = ~ half hour duration at full design power |
| vtsteam:
One caution, remember you now have a 2.6kW capable motor system, not just 500 watts. If you (well, I mean not you but uhh, somebody else...) starts hot-rodding around you could conceivably get a 6 minute duration at max throttle before you wrecked your batts. Absolutely essential to have a voltmeter on board as well as an ammeter. You would want to switch off and start pedaling at a red line minimum battery voltage. And always keep throttle below your 100 amp max ESC rating. 500 watts is going to be more like 20 amps. And a 100 amp fuse, and box of spare fuses as well. |
| S. Heslop:
One of each of those batteries costs £35 (although maybe they'll rob me with delivery charges). I suppose it's not too much to take a risk on, and if it works out I can buy maybe a couple more packs to get more range. I also need a balance charger. I see this one in alot of videos and the price doesn't seem so bad. I guess I should buy a better multimeter too since my current very cheap one isn't that reliable. The costs add up! Usually I try not to think too much about the price of things and get surprised when I suddenly run out of money, but for this project i'm keeping a log of everything I spend. I'm curious to see how much I spend in total (tools n all) so I can compare it to just buying an electric bike. I also suspect if I make a video it'll be the first thing people will want to know. eBike videos on youtube tend to have real bitter comments. People getting upset that it was based upon a cheap bike, people getting upset that it's cheating and an affront to the purity of cycling, people getting upset that it's too complicated for them to bother building, etc. So i'll be interested to see how a video I'd make would fare. |
| S. Heslop:
Well the secret delivery cost and paypal's own currency conversion being off by a few pounds bumped the price up to £43.54 for the batteries. And just like that i've almost spent almost £100. It's frightening how quickly you can buy stuff online. I had a friend who spent something like 150 USD on useless mobile phone software when he was drunk one night. He had that one click purchase so there was really nothing stopping him from going hog wild. So far i've spent about £150 on materials for the bike, including the bike itself. I'll probably spend another £50 on metal and bearings this weekend and that should be everything excluding extra batteries (or extra speed controllers if i bugger this one up). With the cheapest eBikes costing £500 new it's still cheaper, but not amazingly so. |
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