R/C Hobbiest, worker, bicyclist...

[Bohh]

Hi all,

WOW! How exciting! I work at a Hobby Store and play with planes and cars all day. Along with that I'm really into bicycles. Now I find out that these two realms are somewhat combined!

Anyway, to get started, and to commute to work I was looking at purchasing the ampedbikes.com kit. It looks to be a fairly good setup. However, I'm at a lose for batteries. I use Lithium Polymers on my cars and planes, but it seems to get a good setup would cost a lot for a bike. I was thinking of getting some SLA's through the store I work at with my discount. However, I can only get 12v 7AH SLA's. Are this insufficient? What else could I use, that I might have access to?

Additionally, I see a lot of folks using outrunners for planes to drive the rear wheels. Would something like that be recommended? What kind of cost (just estimating is fine) would that be compared to the ampedbikes setup?

Thanks a lot!

-Mike

 

[AussieJester]

Welcome to the forum mate

Im pretty new here myself and also have a background in RC helicopters. Just recently a few fellas have started using the rc motors from what i can tell though its a fair bit of designing andmanufacturing of parts/reduction gearboxes/speedcontrol/servo tester modding owning a lathe and milling machine doesnt hurt either hehehe... I would think the kit you linked to would be the better otpion for the first build unless of course you are the handy type and have access to machinery then checkout Matts thread here http://endless-sphere.com/forums/viewtopic.php?f=6&t=3904 Would have to be the slickest rc motor build on a an ebike going around IMHO the man has mad skillz... As for batteries if you have the $$$ LifePO4 seem to be the ducks nuts at the moment, some are still hanging on to the SLa technology but they are no match for the newer technology the one thing they have going for them though is they are cheap. 12v 18ah is what your needing.

 

[docnjoj]

As a hobbiest and former R/C powered glider contestant I can truly say I want no part of that high tech machinest world. Aussie Jester and Matt are superb machinests and welders and I have minimal skills in those areas. I do like to ride and solve minor mechanical engineering problems. Read further and start with regular E-bike batteries and hub motors! If U then think that U can do better, the skys the limit! Get one working first! See Dogmans posts! Then look to the experts like Aussie Jester or Matt or Miles! Just MHO! Read all u can on this forum! If U have access to low cost Nicads or NiMh from the hobbyshop, then use those for power! Also, for those power sources, Astroflight rules!
otherDoc

 

[lazarus2405]

Those ampedbike kits are decent for beginners, especially if you're on a budget. There are lots of hub motors and hub motor kits out there, and in general they're pretty robust. As you might have noticed, the most popular motors are those made by Crystalyte; head on over to ebikes.ca to read up on them. As for RC motors, I'd only suggest that route if you would enjoy the building as much as the riding. To get good results you need to use a fairly expensive motor and build a solid drivetrain for it.

If you're starting a new build and want to use the battery in the long term, do not waste your time with SLA. Don't do it. They're heavy, big, difficult to mount, have a shorter lifespan, are adversely affected by temperature, require immediate charging after use, and take a terrible hit from the Peukert effect. Not saying it won't work, I'm just saying that in this day and age there are far better options. Perhaps if you can get them cheaply you could use them for the short-term, to test the bike or get a feel for it. If you get (or borrow ) them for free, though... that's a different story...

Naturally, if you build a battery out of RC-grade LiPos, it'll cost a pretty penny. The most cost-effective solution currently is the Ping battery (aka "duct tape battery", because of its appearance). That gentleman assembles Chinese-manufactured LiFePO4 prismatic cells and sells them on eBay (ebay store: http://stores.ebay.com/PingBattery). You could also buy one of any number of ebike/scooter batteries, or build your own from powertool batteries or individual cells, etc. One suggestion is to just browse these forums for people's build threads and look at what battery setups they're using.

As for how much you need, that depends on how far you want to go, how fast, and over what sort of terrain. Work backwards from those power and distance requirements to find your capacity requirement. A well-built ebike can expect to use 20Wh/mile (remember that watt-hours are V*Ah) at 20mph, 28Wh/mile at 25mph, and >80Wh/mile at 40mph.

So how far is your commute? How fast would you want to go (consider it is a bicycle, but also consider what speeds you need to be safe in traffic on the roads you'd want to use)? And can you recharge at work or do you need to fit a round-trip in one charge?

And what else are you curious about, with respect to ebikes? We're here to help, so fire away.

 

[Bohh]

Thank you all for the replies. I appreciate it. I think I will be going with the Ampedbikes kit then. Now to decide on a power source. To get cells from work, even with a discount I'd be paying 300-400 for the cells. At that point it would be smarter to get a LifePo4 battery. But, I can't really spend that much right now.

I have the opportunity to get an used Giant Esuede 9ah 36v battery. Lightly used and in good health for $200.00. Is this a good deal? Will it support the ampedbikes kit sufficiently? Will I make it to work and back? About 15 miles round trip. OR will I have to charge at work?

The Esuede, from what I understand used a 260-300W motor - that's less than the Ampedbikes kit at 500W.

Also, what concerns do I have to have when using NIMH and reaching the end of the charge? The bike will slow down, but will I damage the cells if I go too low? I know on SLA's you can. On my R/C cars we run the NIMHs down all the way if we want to without fear of damage, but then again the most expensive pack I have is $60.00.

What is better about this pack then 3 SLAs?

Thanks a lot!

 

[Larry]

Welcome,

Three 7ah SLA batteries running in series at 36 volts will get you about 6 or 7 miles wide open throttle with no pedalling with a 20 amp controller. That's assuming a fairly flat terrain and a 200 pound rider. You'd have to help them by pedalling even on fairly small hills. I don't think you would be happy with them for your commute--unless you are into pedalling a lot. With SLA's you would want to charge immedieately after use so you would want to charge at work if at all possible. Three 10ah SLAs should be barely ok one way. Three 12ah batteries just might get you 15 miles.

I wouldn't expect generic SLA batteries to last very long--a few months at most. B&B brand SLA batteries seem to have a good reputation, though. I've tried cheap generics and B&B brand batteries and the B&B brand (at least the BP series) definitely last longer and are worth the small extra cost. Even with good SLAs, you can't really expect more than about 9 months to a year out of them with daily use. AT least that has been my experience.

I think most people start out with SLAs on their bikes. But, if you can get a deal on nimh or nicd and chargers through your work, I would go that route-if you can't swing the cost of Lifepo4 or lithium manganese right now. Most ebiker's won't use Lipo batteries on their bikes due to concern about explosion.

 

[johnrobholmes]

NIMh can be run down all the way with no worries. All good suggestions here too.


Fellow RCer, biker, and now Ebiker too.

 

[safe]

NiCads last longer and are more durable. Here's a deal I went for and they've been working out well for me.

http://cgi.ebay.com/96-NiCd-Sub-C-2400mAh-Batteries-for-PowerTools-Flat-Top_W0QQitemZ330198582341QQihZ014QQcategoryZ40975QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

 

[johnrobholmes]

How do you charge your nicads, safe?

 

[Bohh]

Thanks for all the thoughtful replies. It seems that everyone is leaning towards the Lfepo4 batteries. But is a 9ah nimh going to be good for me? Is it going to be really set back on any attributes (power, distance, etc?)

It would be better than a 9AH SLA, correct?

The Ampedbike kit will only pull a max of 20 amps going uphill, according to Danny. Will the Giant Battery perform for this requirement? I've read that some batteries just can't do it!

 

[Bohh]

The more I read the more confused I become. It seems to me that everyone thinks Lifepo4's are the best way to go right now. And flying LiPo's in planes and rc cars I can agree. However, it sounds like I will be greatly dissappointed if I get a NIMH pack. Is this true? Should I be spending 500+ on a battery?

I also can't seem to find out if the 500W motor of the amped kit will be too much for the Giant battery (if I were to go NIMH) as the giant was only 300W.

 

[Link]

Lightly used and in good health for $200.00. Is this a good deal?

Not by a long shot. 36V/9Ah works out to about $0.61Wh, and thats BEFORE peukert. After factoring that in, I come to about $0.88Whr. That's getting into low-end LiFe prices.

Thanks for all the thoughtful replies. It seems that everyone is leaning towards the Lfepo4 batteries. But is a 9ah nimh going to be good for me? Is it going to be really set back on any attributes (power, distance, etc?)

It would be better than a 9AH SLA, correct?

The Ampedbike kit will only pull a max of 20 amps going uphill, according to Danny. Will the Giant Battery perform for this requirement? I've read that some batteries just can't do it!

Not if you get decent Ni. Good NiMH/Cd will do 5C or more, meaning that even a 10Ah pack will be able to handle a 50A controller. Thing is, decent Ni will cost you about the same as LiFe.

Since you only need 20A, though, this 36V 15Ah battery from Ping will handle that and should be able to go at least 15 miles. 20 or more if you pedal.

 

[Drunkskunk]

You should be fine with the NiMh pack. RC Lipo are great, but short lived, and LiFePO4 are even better, but more expensive. NiMh and NiCad both are still great options.

Forget the SLA. Trust us.

 

[Bohh]

Thank you! I think I will go with NiMH then, because of the Giant pack I can get.

Do you think that will handle 19 amp bursts (up hills?)

The C rating would have to be 2.1 for that. I sent an email to someone at Giant who deals with these bikes and he doesn't know what the C rating is. The Giant pulls 300 watts, but the amped kit pulls 500w. Any thoughts, please?

Thanks!

 

[lazarus2405]

Forget the SLA. Trust us.

Indeed.

It seems to me that everyone thinks Lifepo4's are the best way to go right now.

LiFePO4 and LiMn, yes.

Is this true? Should I be spending 500+ on a battery?

If you'll be riding the ebike, yes. If it'll sit in your garage, just go ahead and get some used SLAs, play with it for a weekend, and forget about it.

Now, good lithiums are initially expensive, but they'll last longer. That is, they'll be useful for more charge and discharge cycles. A good set of SLAs might last you a year of frequent use, while good lithiums will last 3-5 years. Considering the longer lifespan, it's worth the investment and cheaper than other chemistries over the lifespan of the pack.