VPower 24V 500W kit - TOTAL Newbie..

G

GaryJS

100 mW
Joined
Aug 3, 2011
Messages
37
Location
West Yorkshire, UK
Hey guys,

I finished building my first ebike last night and took it for a test ride (7.5 miles, 850ft climb)! I have a 24V, 500W Vpower.hk kit running off 2x 12V, 12AH SLA AGM batteries (until I save up for a LiFoPo4 battery). My plan is to be able to do a 14 mile journey to work in less than an hour so this is mainly just to help me up the hills (and there are plenty of those in the north of England where I live!)

One thing I was surprised about - the controller seems to max out at around 12mph - Does anybody know a way to up this top speed? I'm only looking for a few extra mph's? This is the kit: http://www.vpower.hk/product.php?id=43
(although the controller and the motor look different.. The motor is bigger and painted black, as is the controller - I'll try and post some pictures later...)

I can see this ebike thing becoming a slipply slope! I'm already looking at all sorts of accessories - watt meters, upgraded brakes etc... :)
 
maybe it's not your controller that's maxed out, maybe it's the batteries. you only have 288 watts. then you have to figure in the puekert effect. regular sla's are rated for discharge over 20 hours. agm's, i think, 5 hours. when you try to get it all in an hour, the efficiency goes WAY down. not to mention, at the lower speed, the motor is less efficient as well. forget the brakes, this bike isn't going any faster than you could normally pedal it. get some lithium. or you could just get another set of sla's, for a few more mph and more range.
 
Thanks for the reply :)

They are 12V batteries (wired in series to give 24V) with a capacity of 12AH.. Not a maximum current of 12Amps. I.E. They can supply loads of current, although at the cost of reducing the capacity since they are rated for a low C discharge but that's fine.. I'm sure they can supply 20A of current (24V x 20A = 500W) without breaking a sweat.. Although at 1.6C discharge the capacity will likely be more like 8 to 10AH at best (not that' I'll be pulling 20A for much of the time...)

A good way to think about it is in an ideal world where the discharge rate doesn't matter, when fully charged, these batteries would be able to deliver 12Amps for an hour before they went flat, 24 amps for half an hour, 28 amps for 15 minutes etc... Although as I say - lead acid batteries don't like to be discharged that quickly if you want them to survive long / give the rated capacity...

-- So I still think it's the controller.. I think the speed limit in China is 12.5mph and since they are based in Hong Kong I guess the limit is set to that...
 
Well, it's both the batteries and the controller. Both only supply 24v, well, maybe as much as 28 when just charged. In any case, 12-13 mph is about all you'd expect from that.

So what you really need is a 36v controller, and one more battery. Then you should see a bit more speed, somewhere in the 15-20 mph range. Often the 36v controllers can also be run at 48v, for even more speed.
 
Possibly. Look inside and see if the caps, which look like little cans, are marked 50v or higher. If so go for it. Chances are though, they will say 30v, which saved the manufacturer 10 cents per cap. But they may have been using the same controller for both voltages, and have 50v caps in there.
 
See.. I told you I was a newbie :) I didn't realise that the top speed was limited by the voltage :oops: - I thought it was just power...

I'll investigate! I have 2x 12ah batteries and 2x 7ah batteries so I can put one of the 7ah in series with the 12ah for a test if the caps are > 40V.
 
6s lipo is a good = to 24v. Starts out a bit lower than 24v nicads, but sags so much less that in use, the actual votage delivered to the controller is very similar. 7s would be nice too, but that is pretty hard to locate, forcing you to use 3s+ 4s to get 7s.

You might want to use whatever voltage you can get away with, with that controller. Take the max your caps can do, and divide by 4.2v for the number of cells you can run in series. Say you have 50v caps, then you could use 11s lipo. Likely though, 10s would be perfect, and less complicated for charging. So for a 15 mile ride one way, you'd need 6 , 5 ah 5s packs to make a 15 ah 36v pack. 8 even better, to have a lower depth of discharge.

But for a daily commute, having to charge at work safer, wanting the lowest cost per mile, the best bet would be a 36v 20 ah lifepo4, or a 48v 15 ah lifepo4. I've been riding a similar distance for three years, using pingbatteries. For me, they are perfect for the commuter bike.

I have lots of lipo too, which I beat the snot out of riding bikes just for fun. Dirt and racing, etc. I could care less about cost per mile then.
 
GaryJS said:
See.. I told you I was a newbie :) I didn't realise that the top speed was limited by the voltage :oops: - I thought it was just power...

I'll investigate! I have 2x 12ah batteries and 2x 7ah batteries so I can put one of the 7ah in series with the 12ah for a test if the caps are > 40V.
Click to expand...

Hope it works out for you. Dogman asked you to look inside the controller to see what the caps are. If you are testing without knowing you might run into trouble.

Gary
 
Thanks guys :) Especially dogman for the really helpful advice. Much appreciated. I'll get saving.. Those ping batteries are not so cheap! They are about 33% more than vpower.hk's equivalent...

Well.. I made it! First commute!

http://maps.google.co.uk/maps/ms?msa=0&msid=211150202879810676935.0004a9bcb714aa5e83031

I need to have a look inside that controller.. It's not quite as easy as it sounds since I've taped it on pretty well and have run out of tape! Step 1 - buy more tape! The other problem is that there are lots of screws down the side - my guess is that they might be holding fets to the metal frame for heat sinking but that only makes it a bit of a faff - not impossible.
 
Often you can just remove the end cap, and see enough to read the caps.
 
Great news! 63V caps and 75v FETS (STP75NF75)! I needed to remove one end plate and slide out the top plate to be able to read the values.

6011538018_2d7f53f8bf_z_d.jpg
6010988419_3883af2402_z_d.jpg
 
hey Garry, that seat post rack looks good, I think I will get one of them for my batts, Do you think it is strong enough? I see you are also in UK, can I ask where you got it from??
 
Hey Flanders!

I got it from a mate who is doing a similar project. He has gone AWOL at the moment but I'll ask him when I see him (I need to get him a replacement anyway....)

I've had 2x 12ah lead acid batteries on it and ridden it over a few pot holes and so far, so good - the only problem is that with all that weight so high up, the bike is quite unstable (no standing up and peddling!) - if you have SLA's you might be better with something that holds the weight lower..
 
Just a little update - I have tested the wheel with 36 and 48V and everything was OK :) Top speed was up.. About 22mph for 48V! 16mph for 36V vs around 12mph with 24V
 
The speds seem low!
I have 2 24v500w hubs and on 36v hey hit 26+ and on 48v over 32mph. Not sure of which Chinse co made them.
One looks like a Golden and other looks like a Conhis.
I wll say they sure have a great deal of power. All are run on a 12 fet controller and have been reliable.
Dan
 
Hey DanD,

I've retested with 12AH fully charged SLAs and top unassisted speed was more like 19mph on the flat with a slight following wind (although I could feel it 'helping' me peddle at 21mph ish).
 
So tempted to get rid of the bricks but I need to save up for a while! Lifepo4 would be ideal since I charge it at work but I'd be looking at £300 ish I guess :S
 
On the other hand.. a 5s4p (37v 10ah) lipo pack with charger, psu, and leads would be about £175 :) But it'd be a bit dodgy charging it in my office!
 
Hi guys,

With my batteries plugged in I can't exceed about 27 miles an hour down hill (not that I want to go much faster!) due to the back emf reaching the charging voltage of my batteries - great if I want to put a bit of charge in my batteries going down long hills but not so great if I want to go faster. Unplugging the batteries at the top of hills allows my speed to freely increase to 35+mph (just to prove thr point..) but the voltage on the exposed plug reaches around 60v - that should be OK since the capacitors in the controller are rated at 63v (note to self - do not exceed 35mph or the caps will pop and don't touch the exposed plug!!). So... I could either fit a switch to disconnect the batteries (the advantage been that on longer runs I could charge batteries down hills) or fit a diode to not allow current to flow into the batteries (fully 'automatic').

It seems a bit too obvious so I don't understand why it's not built into the controller or commonly discussed - unless there is some kind of problem with doing this? Or is it just that everybody but me is running 72v lipo? :D
 
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