GoldenMotor.com Forum
General Category => Magic Pie & Smart Pie Discussions => Topic started by: dofbikes on September 18, 2012, 10:13:59 PM
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Hi everyone.
I've a question about batteries.
What do you think in the association of two LiFePO4 (12V/20Ah) batteries in series for use with magicpie2? It will be 24v 20Ah. http://www.ev-power.eu/LiFeYPO4-batteries-12V-1-1/Lithium-Battery-LiFePO4-12V-20Ah.html (http://www.ev-power.eu/LiFeYPO4-batteries-12V-1-1/Lithium-Battery-LiFePO4-12V-20Ah.html)
There's the need to buy/create a BMS and charger. Do you see any performance problems with this configuration?
Then, my throttle is 48V and the motor is configured to 48V. Is there the need to change both?
Thank you all,
Rui
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The battery must be managed as a single monolithic 12V block.
How are you planning to incorporate BMS into these batteries exactly?
Nice deal though. At 48V (4 batteries, duh) the price would be about half of what I paid. Mind you, mine has BMS, but that doesn't seem to justify a 100% increase in price.
I'd be temped the run these without BMS. Sacrilege perhaps, but the RC geeks run LiPo without BMS and that's a whole bunch more volatile. You'll just have to keep an eye on cell voltages. A Cycle Analyst would probably help. It would only give you a voltage reading of all cells in series though.
24V will be underwhelming as far as speed goes (is this for your grandmother? ;) ). And yeah, your 48V throttle is a problem. It likely won't work. Maybe someone else knows how to run a 48V throttle on 24V, but i'd probably just buy another $15 throttle.
I don't think your motor is configured for 48V, unless there's a drive parameter I can't think of at the moment. Your motor will be rated at 720W (24V x 30A). Note that the specs for your battery list 0.5C as "optimal discharge rate". It'll do 3C for 15 minutes, so let's say you can safely discharge at 1C. That's only 20 amps. Problem is that the motor will happily draw 30 amps under full load.
That configuration looks like it's going to strain your cells.
Jeff
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It's not unreasonable to charge the batteries independently. As long as they each have a bums you would be safe.
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It's not unreasonable to charge the batteries independently. As long as they each have a bums you would be safe.
Bums, lol....
Gary
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It's not unreasonable to charge the batteries independently. As long as they each have a bums you would be safe.
But it will work? I don't think so....
BMS is just for 24V pack and your charger output is for 48V pack...... >:(
So you have to charge them separate...
O well 48V throttle is just some leds and resistors.
So if know the right resistor for the 24 voltage pack you can change it that's all (no rocket science).
Maybe you could measure the resistor? it's for 48V pack.
So for 24V can can maybe use half of total ohm of the 48V resistors.