RC Car batteries for e bikes

[m303625]

Hi guys
been following this thread with great interest, I also have a small geared brushless hub motor (not sure if it is a bafang but it looks very similar) with 36v 10ah lion battery and am looking at ways of getting more power out of it. I too only do a short commute to work and home of around 5kms each way.
my question is How do you go about keeping the seperate packs in balance and do you have to charge each pack one at a time?
and 2 are these things safer than lipo (keep looking at you tube video of rc plane exploding in mid flight)
any advice appreciated
thanks

 

[Richard1174]

Hi there

Thanks for showing an interest in this thread.

I have been running these packs for over 2 weeks now with no problems at all. I have 5 packs all in series to make up 60v as far as balancing is concerned 5 12v packs in series is only the same as a 60v pack made up as such. There is no balancing lead on nimh packs or nicads to plug into a cell balacer anyway. I think the balacing issue is much more important for the rc lipo packs which do require regular looking after. I bought a decent charger a pro peak constellation which can charge up to 25 nimh cells at a time so I tend to charge 2 packs in series 24v (x2) and one pack on its own at 12v and then I rotate which packs I series up for charging. I have used nicad and nimh packs in the rc world for a number of years without any problems and do be honest I have always been hard on them building very fast rc cars with very high current drain. I have noticed that the packs do get warm on charging and after a hard run on the bike, I just make sure that I always let them cool down before I put them back on charge. The only time I have ever seen nicad or nimh catch fire or explode is under a direct short circuit condition and never under just high load so I think they are safer than lipo under high load conditions.

Hope this helps you. A good quality charger is always a good investment, batteries will always have to be replaced as time goes by as they all have a limited life span but a good charger should last for ever if well looked after.

If it is a 250w bafang motor you are running then you won't be dissapointed if you up the volts even at 48v they seem to come much more alive at 60v they go really well. I have to run in top gear now if I want to pedal as I go and the power up hill is great. Just check your speed controller to see if you can read the voltage rating on the capacitors and the fets as although I bought a 36v kit these components in my speed controller are rated at 100v so you never know what you have in the little box of tricks until you get the lid off. I was advised to checked the guts of my speed controller when I first joined e/s and I'm glad I did.

 

[m303625]

Hi Richard, thanks for the info, photos of my motor is attached if anybody can recognise it??
I am checking for suitable packs on ebay Australia, seem to only be 7.4v available here.
have ordered a 48v controller from ecrazyman. but will check mine out also
will start with around 48v first and see how it goes!
this forum has been a great inpiration, what would we do without the net these days
my thanks to all
ps If any body can tell me how to alter the low voltage cutout of ecrazyman controller 48v 600w 28a max
that would also be appreciated (is it the same as the 72v version (which I have studied from this forum))

 

[docnjoj]

Yup! Definitely looks Bafangish! Check Knuckles posts, as he is Da Man here in the states for ecrazyman!
otherDoc

 

[RevDon]

I, too have been following this thread with interest, and have a question or two: First,Who is the manufacturer of the actual cells being used? There are lots of assemblers out there, but relatively few manufacturers. I've been surfing around some of the stateside suppliers, and have seen a lot of Tenergy NiMH cells that have been generally panned in the past. Have they gotten better? Is there someone making better NiMH cells? And who offers the best deal? OK, more than a couple of questions, but I like the simplicity of NiMH - no balacing worries like LiFePO, and the price is a factor. So, has anyone in the U.S. been doing what the U.K. crowd has

Don

 

[Miles]

Hi Don,

http://www.vapextech.com.hk/index.html appear to be the makers of the UK cells, we are using.

 

[Richard1174]

Thought I would give you a little update on how the cells are holding up as I have running on them for about 3 weeks now.

Well according to my watts up meter it consistantly uses around 2800maH on my 7.5 mile run and thats pretty much flat out all the time now I have got used to my extra speed and I like it. Voltage of the five series packs hot off the charger is 67.5 volts and after a run off load its between 61 and 62.5v and the lowest volts I have seen when on load up hill is 56v but I was pulling 900watts at the time. Once they are on load for about 10 minutes they seem to level out at 60v at full speed. I think I might be suffering from a bit of voltdrop in the cable run between the battery and the speed controller. The battery is in a bag on the rack at the back, I have a twin core running up to my watts up meter on the handle bars and then back to the speed controller which is about half way along the bike, so I guess its about 7 ft off 1.5mm 2 core flex. I have noticed that it is warm to touch after a full power run. I think I am going to put the speed controller in the same bag as the battery and move the watts up meter closer to remove all the cabling and see if it makes any difference. So a little bit of fine tunning to do but nothing major, I am considering getting another 5 packs and parrallel them up to 7400maH for some more range.
I have had speed controller or motor problems at all, no exesive heat or strange noises so I am pretty happy that it is just as reliable as before just alot faster.

Miles

have you got your charger yet I am looking to hearing how you get on.

 

[Toorbough ULL-Zeveigh]

not only more range but less sag too, meaning a little faster top speed which I think would be most noticeable uphill along with cooler running cells & probably longer cycle life to boot, so definitely worth the doubling.

 

[Miles]

Miles

have you got your charger yet I am looking to hearing how you get on.

Hi Richard,

Yes, I've just started using it.

I can charge the whole 38.4 string @ 3.5 amps.

On the second discharge (average 2C), I got 4.3 Ah out of the 4.6 Ah pack, so it looks like it will be well within spec. when it's fully conditioned.

 

[docnjoj]

Hey Miles! What do U discharge your NiMh with. The Astro charger only will go up to 1.25 amps in D/C mode?
otherDoc

 

[Miles]

Doc,

I meant discharge in use

For conditioning, I'm using the pack on the bike up to about 90% and then using the Astro charger to discharge the remainder. Is this ok?

 

[docnjoj]

Very sharp! Thanks. I thought i had to get some light bulbs or something wierd!
otherDoc