Strange case of the C

[deacon]

Yes it's a trick title. I'm hoping to get someone with some experience with a battery of one C to answer. It is looking more and more like my home brewed battery pack has only 1C.

My question is this. When I finally get to the 25amp hour level of true current in my pack, am I going to need to go far above it just to keep the bike running at full speed. In other words am I going to need 35or 50ahs of battery to get full performance.

It will run now at about half speed but when I throttle down or get to a hill it either cuts out or it gets very slow. Which tells me it has hit the upper limits of the battery without getting it's needed amps for max performance.

Someone who has real world experience or even good theoretical knowledge would be most helpful.

 

[snellemin]

What setup do you have right now?
It does sound like your batteries are not up to the task at hand. You might have to get some other batteries that can output more power.

 

[deacon]

Actually I'm building them as I go. It's an experiment as well as a battery to power a scooter I built.

What I don't know about the batteries. The true ah value the manufacturer lied. I am shocked at the chinese manufacturer would do that.

I am also shocked that the C is so low since I was told it was at least 1.7.

If I took the manufacture's numbers at face value I would have a 36ah 2c battery to power a 25 amp draw hub. Obviously one or both numbers are crap.

The fact that the pack isn't working now isn't unusual. It is just a matter of adding to the ah till I get enough. The question is even after there is enough to peak out the draw, how much will I need to give it some range.

Fortunately it is cold and wet and snowy here on the east coast so I have time to get it right. Just wondering what IC is like when it has enough power.

One thing that is interesting is that the volts hardly go down at all as it drains. Which is not like the SLA batteries which drain much more quickly I think.

 

[snellemin]

You can't trust these Chinese peeps that just want an easy buck. Good batteries cost money, unless you can put a pack together yourself. I will make a new one myself in a few months. Something that will be capable of 80-100A continuous.

What is the voltage you are running on. 25A isn't much torque at low voltage. If your setup truly pulls 25A, you will need a pack that for can push 70A peak. Going up hills does take up more amperage.

If your batteries are up to it, you can add some solder onto the shunt of your controller and gain a bit more torque.

Your range is greatly effected by the speed. The faster you go the less your range is. 20mph is the sweet spot for range on a bicycle, unless you have some aero fairings to reduce drag.
One of bikes for example takes 500W to do 20mph. 1000w to do 27mph. But it will pull over 6000W to do 50mph.

Post a picture of your scooter and batteries. How much does it weight with you on it? What voltage are you running it at? What speed are you looking for?

 

[deacon]

Its actually very light, till I get my fat butt on it. It is probably close to 300 with me on it. I am running 36 volts, but I'm considering going to 48volts. I have it going about 3/4 power now without faulting. This next addition should bring it close to peak, then I can work on the distance.

I didn't trust the mfg numbers to begin with. Think I heard somewhere that the true ah of the aa batteries is closer to 1500 mah rather than 3000 the mfg claims.

The true mah of the C cells is 6000 not the 9500 they claim. So we shall see when I get it to peak for a sustained period of time, I should be able to tell what the true ah is for the pack. Some one described it seat of the pants reckoning. After that I will work on the range issues. Frankly range is secondary for me. I'm an old guy and my body cant take a long ride anyway.

The scooter does better hitting peak than the trike. The trike is heavier and wont hit it's peak power at all yet. I expect this weekend to get the trike up to speed then it's a matter of adding ah to get the range to about ten miles.

The one thing I notice which could be just the ah shortage is that the voltage seems smoother on the nimh pack than on any of my sla packs.

 

[snellemin]

36V is the culprit. Translates to 36vx25A=900W You need at least 48V, which would get you 48vx25a=1200W. But since the total weight is 300lbs, you will need something that has more power. So a new controller that can to 48v@50A for a solid 2400W for climbing up hills. On the flats you'll still do 1000W or so with a smile on your face.

 

[deacon]

You are talking to a married man who two years ago fell off a gas bike at about 30 mph. (blacked out due to a brain tumor why I don't drive a car.) Broke six ribs my collar bone and collapsed a lung. Mama said no more bikes. But she agreed to a three wheeler and electric if I kept it down to 20mph top speed.

Then i flipped a three wheel scooter I was working on over and did some disk damage. That one I got to watch flip over backwards then jump up and down on me.

I gave mama my word to take it easy. The most I can get away with is 36volt 800 watt controller. I have run the controller on my trike at 48v same 20+ amps. it did just fine good speed and pull on the hills.

I might do something like that with this controller or buy a new one. Number one thing to do is figure out this battery pack which I expect to do before spring. Then I will probably tinker with the voltage since I can't stop tinkering.

The scooter looks more or less like this. I have changed the rear deck a little but not much.