llile
1 kW
- Joined
- Dec 18, 2010
- Messages
- 457
Well, I'm going down the adventure road of building a battery from scratch. I've built everything else on an E-bike from scratch almost, so why not?
Batteries - I found a deal on some panasonic INR1865015L's. They aren't the highest capacity 18650's, but they'll do. 1500maH. My goal is to add 15-20 amp-hours to my fading existing battery. It is a different chemistry, so this will be a "spare" that I'll kick in by unplugging the old one and plugging in the new one when the main battery falters. I'll set the Cycle-Analyst low voltage cutout up where both batteries are well protected, with plenty of reserve capacity so I'm not reducing life. If the old 40AH nee' 36 AH LiFEPO4 battery ever bites the dust, I'll use all 18650's on the bike and shed some weight. Right now, the old battery will go till it drops.
Charging and discharging an 18650 bang to bang it has a life of about 500 cycles. If one charges say 90% to 20% the life is increased dramatically, possibly thousands of cycles. This corresponds to a charging voltage of maybe 4.0 volts per cell and a low voltage cutout of maybe 3.45 volts per cell. Depends a lot on the load. In a 72 volt battery this would mean 20 cells in series (up to 84V fully charged to 100%). But wait! I've got another E-bike that's 36V. And my buddy has a 36V bike. So I'll make two 36V batteries and put them in series.
I'm looking for about 15 amp-hours derated capacity (70% of full capacity). That's about 19-20 amp-hours full capacity. These are 1500mAh batts, so 13 in parallel would be 19.5 amp hours derated 70% = 13.65 amp-hours. A little light, however when I sorted my battery order, I've got 263 good ones, so that's where I'll start.
Batteries - I found a deal on some panasonic INR1865015L's. They aren't the highest capacity 18650's, but they'll do. 1500maH. My goal is to add 15-20 amp-hours to my fading existing battery. It is a different chemistry, so this will be a "spare" that I'll kick in by unplugging the old one and plugging in the new one when the main battery falters. I'll set the Cycle-Analyst low voltage cutout up where both batteries are well protected, with plenty of reserve capacity so I'm not reducing life. If the old 40AH nee' 36 AH LiFEPO4 battery ever bites the dust, I'll use all 18650's on the bike and shed some weight. Right now, the old battery will go till it drops.
Charging and discharging an 18650 bang to bang it has a life of about 500 cycles. If one charges say 90% to 20% the life is increased dramatically, possibly thousands of cycles. This corresponds to a charging voltage of maybe 4.0 volts per cell and a low voltage cutout of maybe 3.45 volts per cell. Depends a lot on the load. In a 72 volt battery this would mean 20 cells in series (up to 84V fully charged to 100%). But wait! I've got another E-bike that's 36V. And my buddy has a 36V bike. So I'll make two 36V batteries and put them in series.
I'm looking for about 15 amp-hours derated capacity (70% of full capacity). That's about 19-20 amp-hours full capacity. These are 1500mAh batts, so 13 in parallel would be 19.5 amp hours derated 70% = 13.65 amp-hours. A little light, however when I sorted my battery order, I've got 263 good ones, so that's where I'll start.