I have 4) 12V LiPo batteries, rated at 16A-hrs. They'll be connected in series, to make a 48V system to power the motor on the e-Bike. I also plan to use a Predator 212 (Harbor Freight engine) to spin a single wire AC Delco alternator as an onboard recharger. How would I go about hooking this to the batteries to "recharge as I ride", so to speak?
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1What you're building, with that 6.5HP engine, is a motorcycle. Don't expect your licensing authority to accept "it only recharges the battery" dodge. – hacktastical Apr 17 '21 at 02:10
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Alternator efficiency is poor so net gain will be negative unless you just use field current as a brake to charge battery. – Tony Stewart EE75 Apr 17 '21 at 02:34
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Which '12V' 16Ah Lipo batteries do you have? – Bruce Abbott Apr 17 '21 at 03:46
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Charge as you ride is a wishful illusion of recycling energy from the same storage. – Tony Stewart EE75 Apr 17 '21 at 04:32
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You might as well save your muscle power for direct pedaling when your battery dies. You will be less tired. – DKNguyen Apr 17 '21 at 04:46
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@TonyStewartEE75 you missed the gas engine. It's a series hybrid, not a perpetual motion machine. It's not a very good series hybrid, but it's workable. – hobbs Apr 17 '21 at 04:50
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TY , I hadn’t heard of Predator engines before, just Briggs&Straton or Honda, I have a spare 10Hp B&S and looking for a good muffler – Tony Stewart EE75 Apr 17 '21 at 07:04
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Apart from the negatives to this approach that have been given, for the sake of experimentation let me suggest the following:
The alternator is not set up to charge LiPo batteries, so you'll need a suitable charger.
The batteries are 48V, so you'll need some means of increasing the voltage. One way is to rewind the alternator to increase the voltage. The current will also decease proportionately. Then you'll need to have a regulator to work at that voltage.
In all, your proposal isn't too unreasonable, but the implementation has a few hurdles, especially if you want it cheap and off the shelf. I'm thinking it would be one of those hard-core projects you see on YouTube where someone has done a lot of thinking and tinkering to come up with a slick result. I don't think we'd be able to give a step-by-step answer here.
Short answer - unless you want to spend an inordinate amount of time or a wad of cash, maybe look at another project.
Kartman
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Isn’t an alternator basically a variable reluctance current amplifier Iout/ I.field with Voc proportional to RPM but Vout determined by load then regulated , so it can be CC or CV limited by mechanical inertia and speed.? So the external charger could be brought on board to regulate while trigger control could brake lever pot control . – Tony Stewart EE75 Apr 17 '21 at 04:27
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four 12V alternators + four 12V LiPo chargers? Should work - especially as we don't seem to be too concerned about efficiency. I'd be leaning towards a weed-wacker motor at around 1hp - much lighter and smaller than a lumpy Chonda. A model gas turbine might be another choice - great sound effects and the thrust might help a little :) – Kartman Apr 17 '21 at 05:19