Anyone have any experience with RC LiPOs?

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mingonn

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Oct 9, 2007
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Hi all,

I am thinking of converting my folding bike but really want to keep the weight down. My ride to work is only 13 km of relatively flat bike path and I can recharge there. A modest 15 km range and 25 km/h will suffice.

Have been looking at using RC (Remote Control) LIPO packs but not sure if they will be up to the task. Price and weight are right though.

http://cgi.ebay.com.au/Li-po-Lithiu...photoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

Not sure how to calculate peak Amps though, am hoping to get a 200w geared brushless motor and I weigh 70 kgs.

Thanks
Derek
 
Rated amps = C rate * C

That pack you listed is rated at:

15c * 5Ah = 75A
 
Hi Link,

Was actually after the peak motor draw, I think I have worked it out.

I peak current should be 200w/24v (I=P\V ) 8.3 amps, assuming the 200w rated motor is for peak power which should be the case according to Australian's backwards power restrictions.

Those cells should easily do the job event with the pessimist's .5 rated capacity rule.

Derek
 
That's also an easy one, but it's rarely determined by the motor.

Peak power = system voltage * controller amp limit

So, in my bike, it would look like:

48V * 33A = 1584W

That's theory, though. In reality, I have crappy batts. So it looks more like

41V * 33A = 1353W

Just FYI.

Lithium batteries should have much less sag, though. Also, the 1/2 capacity rule is usually meant for lead-acids to compensate for the Peukert effect. Most lithiums deliver close (or even more) than their rated capacity.
 
Li-poly rc batteries require extremely careful use... they can explode / burn your house down. They are usually a Lithium-Cobalt chemistry.

You might prefer a LiMn or LiFePO based pack. They are safe.

:!:
 
Would love to try LiFePo but they are expensive for what I need (24v 10ah packs cost $600+ here).
 
what is the current limit on the controller? if its less than 75A you're fine if not or there is no limit then you might be in trouble, if the motor is rated for 24V and can put out 200W at max power(you did mean max right not rated?) then it will be drawing close to ((200 / 24) * 2) because at max power a dc permanent magnet motor is at 1/2 stall torque and 1/2 no load speed and at most 50% efficient. so that means the peak current at 0rpm will be ((200 / 24) * 4) = 33A, but thats only if 200W is max power, if 200W is the rated current then the motor will probably be running at around 80% efficiency and around 80% no load speed so it would be somewhere around (8.3 / .80) / (1 - .80) = 51.9A, so i guess you would be good with out having to parallel any of those packs, i would check out the motor specs better though as this is just a rough calculation.
 
You can build packs from electric drill batteries by Millwaukee or Ridgid, they are LiMn. DeWalt are LiFe (by A123). I'm not sure about Makita and Ryobi chemistry.

Before you go with lipoly, search these boards on LiCo, Lipoly, fire, overcharge, overdischarge, balancing, explosion. Do the same on the boards at http://www.rcgroups.com. Try YouTube too. See if lipoly is worth the risk.

"Safe" a member here, is interested in a group-buy of thundersky cells... they are very affordable LiFe. Ping's (ebay) packs seem to be a good value, if you are patient to win an auction at a low bid.


:D
 
Hi Dirty_D,

Just trying to spec out a system at this stage and thought I would start with the batteries. Have wanted to convert my bike to electric for a while but after some very bad SLA experiences (dismal number of cycles) on an electric scooter I have been waiting for other chemistries to become more affordable/available. Thanks for the numbers, good to know what the range is.

Laws where I live are for a peak of 200w so that is what I am basing it on. A decent motor is next, have my mind set on a geared brushless but tracking one down that meets the 200w limit in Australia will be challenging. Harder to plead ignorance if you get busted on an 'illegal' ebike if there is public liability involved. If it all gets too hard I might just have to pay the $$ and buy a 'legal' ebike.

Derek
 
I think the Nano motor continuous is 250W. Peaks at 400W. You might be able to get away with that. Only 2.1kg, So it's very light. If you could figure out a way to mount it on the rear, it would be completely hidden by a sprocket cassette.

More info. here: http://nano-motor.co.uk/

What's the deal with the power limit laws there anyway? Is it a limit on the rated power of the motor? That would be easiest, but we all know that any motor can be pushed 8). Or is it the system? System would be hard to enforce, though, because they'd have to do a full blow dyno test to actually prove that if was capable of going over the limit.

:?

Anyway, I'd look into getting a Ping Pack if I were you. The 24V 10Ah model is like $199+ shipping. That would power a nano (if kept at the legal limit) for a really long time.

You also wouldn't have this problem here. Fun starts at 0:50 :D.

[youtube]vS2hGoJVmlA[/youtube]

Fourth of July ain't got $#!+ on us 8).
 
Link,

Do you have a link to Ping's site?
 
He's an eBay seller.

Here's a link to his store: http://stores.ebay.com/PingBattery

I'm sorry, I was mistaken. The 24V 10Ah pack is not $200. The 24V 15Ah pack is. :p

He doesn't have any 24V 10Ah packs for sale right now, though. You can either get a higher capacity pack or ask him to make one.
 
Found Ping's ebay store, great value there. Will be getting one of those packs I thinks. Thanks for the heads up!!

Cheers
Derek
 
No prob.

They're a little low on power for my purposes (only 1C rated, 1.5 max continuous), but for a lower powered bike, they seem to be about the best value you can get.
 
My booster pack for my bike is 4 x 2600mAh 11.1V RC lipos in parallel.

They get discharged/charged every work day...for about 5 months now.


They work fine. Yes they can catch fire. No they don't catch fire in the real world, assuming a minor level of care is taken.

Lipos are everywhere, they aren't that dangerous at all. Just don't overcharge or pierce them.
 
Lipo can be dangerous. But they are in everything from Cell phones to Laptops to those musical greeting cards, and kits toys Like those little flying helocoptors and tiny foam planes. Lipo batterys are everywhere.

They can explode, and the danger increases with size, but if you handle them with the same resect you would handle Gas (You guys call it Petrol?) then it should be safe. I.E: Don't expose it to open flame, Don't use it if the container is damaged, don't refuel (recharge) indoors. Keep it out of the reach of children.

I Fly RC planes exclusivly on Lipo. I've had a couple incidents with Lipo, but no explosions, not even smoke, and one of those Lipos was exposed to a 100mph hit into solid ground. (nice crater) The battery was destroyed, but didn't catch fire.

I am also now using Lipo on my Ebike. The packs I have are half the size and weight of LiFePO4, and they aren't nearly as good as the RC grade packs. My packs have been used to 105% and still were above minimum voltage. Lipo are one of the few batteries that will often give you 100% of the rated capacity



A note on your 200W motor law. My understanding is thats the rated power, meaning what it draws at full speed. a quirk of Electric motors is that they will draw a lot more power while accelrating, so a 200 watt motor may draw 500 watts when starting out. WHen chosing a battery for these motors, it might be a good idea to pick one that can handle 3 times the motor's rated needs, so a battery that can handle 25 amps at 24 volts would be all you should ever need.
 
Nup it's 200w max output.

Everyone ignores it, as a 200w bike is NOT WORTH THE EXTRA WEIGHT. You'd be better off getting a lighter road bike with the money instead of a motor.

Got any pics of your Lipos ebike pack Drunkskunk?

I've been adding the numbers up on DIY'ing a 60V 12-15Ah Lipo pack. Have you got a BMS? How do you charge? I just use a bunch of el-cheapo E-sky chargers + timer to shut them off...just in case one keeps charging.
 
200 watt max? Ouch. I think I'd be printing out a 200Watt lable to stick on a Puma. :twisted:

What I have came from Itselectric.ca 37v, 8.2 amp, and I use 2 of them. BMS is built in. its the silver thing on the end, but its a crude BMS It doesn't balance the charge, but it does have a tap for an external balancer. Only pic I have of it, I took it as a Joke for the RC forum.

P1010072.jpg
 
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