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The Rezistor - batteries are here
The two 36V 20Ah battery packs arrived yesterday. Pretty fast shipping, considering they shipped from China on Thursday. (sunglasses in the photo are for scale) Sam at YESA was able to have them configured two different ways so I can fit one (barely) where the gas tank was and the flatter one in the left cowl. I think I'll separate the BMS circuit boards and put them in the gas tank area where they're better shielded from the weather. The chargers (one for each pack) were a little bulkier than I had hoped, but they're light and I think I can fit them under the seat, where I'll also include the charging cord.
Thanks for the advice about checking the individual cells. The only real instrument I have right now is an analog multimeter; will I need more than this to check if the BMS is working properly?
Jake
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The Rezistor: 1970 Vespa 50S Special conversion w/ Mars brushless motor, Sevcon Millipak controller, 36V 40Ah YESA LiFePO4 batteries
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Re: The Rezistor - batteries are here
Looks nice - i'm jealous! do you mind if I ask how much they cost?
------------Re: The Rezistor - batteries are here
The BMS should charge each cell to its correct voltage and also cutout if a cell fall below a certain, it might also have overcurrent or temperature protection though this is less important as you can set the current draw anyway.
a multimeter is all you need. Check to see if that each cell is charged to no more than the max charge voltage when resting (normally 3.6 volt for lifepo4). undervoltage is harder to check for but it worth checking the cells a lot at first just to see what they're doing. A battery meter like the cycleanalyst or wattsup might come in handy too. are you running at 72 volt or 36 volt parallel?
there's another thread on yesa here
http://endless-sphere.com/forums/viewtopic.php?t=1972&highlight=yesa
Re: The Rezistor - batteries are here
Thanks for the advice and the link to the other forum. I'm going to run them in parallel to power a brushless 3-phase Mars/Etek motor at 36V.
Jake
------------The Rezistor: 1970 Vespa 50S Special conversion w/ Mars brushless motor, Sevcon Millipak controller, 36V 40Ah YESA LiFePO4 batteries
Re: The Rezistor - batteries are here
You might want to consider running at 48V - you'll draw lower amps and potentially have the ability to gear lower (because of the higher RPMs the motor will turn). You'd need to redo the packs though - so probably not worth it.
How did you come up with the decision of 36V? (AFAIK your motor/controller combo will handle 48V max)
BTW - how do you intend to drive the back wheel? i.e. are you going for a single, fixed gear or are you going to try and utilize a CVT gearbox (as is common on these small scooters - don't know about your particular Vespa).
------------Re: The Rezistor - batteries are here
LiFePO4 battery costs being what they are, I decided to go with only 36V and a total of 40Ah to try to get a little more range. Also, I was told the controller is not a 48V controller, even though the motor can run at 48V. If that's not actually the case, and it turns out that my performance really sucks, than I might change to 48V and sell the 36V batteries. Or maybe run them in series to power a 72V system on my next project.
I haven't worked out all the drive details yet. It will be a single fixed gear; I'm estimating a ratio of maybe 2.7. If I can find a smallframe Vespa engine case (no luck so far) that I can cut down and use as the swingarm, I might be able to use some of the existing gears inside that. If I have to build a swingarm from scratch, I think I'd prefer a belt drive (quieter, no lubrication needed) but I'll use a chain if I have to.
If you haven't noticed, I'm sort of figuring a lot of this out as I go...I have the wheel, so now I need to find the appropriately splined axle, find bearings for it, then decide how they attach to the swingarm. I guess there's no point in finding the cogs or gears until that's done.
Jake
------------The Rezistor: 1970 Vespa 50S Special conversion w/ Mars brushless motor, Sevcon Millipak controller, 36V 40Ah YESA LiFePO4 batteries