battery issues

For me it is not so much about the speed but the range. We can buy the size motor for the speed we want but the battery consumption is what it is not much you can do about it soooo. Lets start a thread to compare and give battery tips...

My suggestion is we use this formula.... battery ah rating divided by miles range (real world not a pipe dream mfg figure).

My motor is a hub 24volt 250 watt.... I figure its 4 miles on 12ah battery that would be a 1mile per 3ah rate.... I suggest we go with the 1/3 ratio and compare different motors. Mine is an ez-glide. That is riding it wide open not conserving batteries at all. Conserving I was able to get at least five miles probably 6 but it isn't nearly as much fun to ride that way.

When I get my friction built I will have a ratio number for it as well...

I really am curious as to your motor and it's ratio.... I will probably be buying more kits or building more bikes of my own. So please join in with your figures.

My test track is the hood where I live. I measured out two miles with my wife's car then ride it with my bike in laps. Please join in....


so in conclusion
ez glide 250 hub motor 1/3 riding wide open on hills and flats mixture of area 220 lb rider.

Does the litheum battery have an amp rating so we can kind of compare...

I did a very unscientific battery test today. I ran my hub motor a measured mile... then ran the friction drive the same course exactly. Both battery packs are the same type and rating. One is new the other has been charged a dozen times.

The results the used pack on the friction drive ended the course with a charge of 13.06 volts.

The hub motor ran the same course with the brand new batter pack with a full charge. It ended with a power charge or 12.87 volts.

I ran both of them at full throttle the whole mile. The hub had maybe 20 to 25 percent more power. It wasn't a great amount but it was noticeable. It was in both torque an speed. The hub motor is regenerative so it probably will last longer. I will start the range tests tomorrow. I will also have the better surface on the drive wheel of the friction bike tomorrow. The better drive will give more torque and maybe some speed but it might also negatively impact on the power consumption.

I was afraid that the new batteries might be bad so I took them out for a range test after I recharged them. They started flashing yellow at about the same time as the other so that isn't the problem. Obviously the hub motor pulls more current than the friction drive.

Which makes perfect sense if the hub motor has more power. Tomorrow is supposed to be cold so the range test for the friction drive with the better roller surface might have to wait a bit. I really am curious to know the deal with it.

rearengine said:

Deacon..
I will be watching for your post.. I'm about to make a purchase, hub, or chain like the Currie gear drive. What is the watts of your friction drive motor? Are we talking mostly SLA deep cycle batteries in our bikes? What I know about Amps & watts is silch..I've always been a gas man, but getting so I don't like the noise in my old age.. Bill

Click to expand...

I am running a hub motor 250 watts and is a low power helper unit at best. I have heard that the 600 watt is a good size but I think it is still less than a china kit for power. I bet the 1000 watt one is pretty close though.

By the way I like mine size and all. I need the exercise and I won't pedal unless I have to so it works for me.

I have two friction drives... I tested the 300 watt and it tests about 75percent of the hub motor. I have what I think is a larger motor but the tag is gone. I am going to test it tomorrow with a good drive wheel and see what the range is on it.


I am running heavy sla batteries 12ah versions. I can get about four miles on mine before they start to fail. I can get another mile out of them even when they are dying. I am going to do a range test on my friction drive tomorrow to see how it goes. By carrying a second set of batteries on a trailer that is low resistance I should be able to increase the range to ten miles.

I happen to have a couple of very old 12volt flooded lead acid batteries meant to be used on lawn tractors. I used them with one of my old old friction drive setups. Something to do with two engines. I think I will spend this rainy day testing a couple of them. Even if they don't have enough power I can pull them on one of my trailers to see how much drag they are on the hub motor.

If it isn't too much, I might give them another try. They are not very expensive and very easy to find in any town. Most are under two hundred max amps, I am not sure what that is in amp hours. I will have to see if I can find a calculator for it.

alas they don't seem to work out that way math wise. I used them with my friction drive before and thought there were about the same as an eight amp hour battery so here is the math best I can figures

lawn battery at 20 bucks

cold cranking amps 180

reserve capacity of the battery =cca / 5 or 36amps

amp hours = reserve capacity/6 or 6amp hours

watt hours = amp hour x volts = or 24x6 = 144 watt hours.

144 watt hours/250 watt motor =a little over a half hour of operation. and that would be complete drain which a modern controller should not allow.

my 12ah sla batteries 288 watt hours should give over an hour of run time. They won't the controller starts to shut it down at about half charge. So I figure I can get half the time on the batteries.


Toy I bought (2) 12amp hour batteries on ebay for about 50 bucks delivered. They seem to be okay so I bought two more to pull on a trailer behind. That will give me 576 watt hours if the math is right that is over two hours if it ran all the way down since it doesn't I figure it at about an hour or ten miles.

I'm not going to try the lawn and garden batteries after all.

Now I'm no battery expert and no math whiz either so this may all be wrong but.

The sla 12ah 24 volt =288 watt hours.... With a 250 watt motor is should run just over an hour but the controller shuts it down before then to save the battery life. I checked when I came in on yellow and it was 12.25 left on the battery. They say 11.50 is dead for all intents and purposes. So effectively I got about half an hour on the batteries. I have gotten as much as five miles on them without shut down but it was running in the yellow off and on.

five miles at ten miles an hour equals half of the charge. So the math seems close to me. But I would not swear to it. Battery life and ebike range is still a mystery to me. But i'm trying to understand it so that I can do better predictions. I don't want to run out of power several miles from home.

Tomorrow's trip when the weather clears off some, is to the senior center. I want to check to see if they have a coffee club there. If not I will try some other place.

I'm going to read the battery charge after that about 2 1/2 mile trip. The reason I chose that trip is that it is almost all slight incline or slight decline. I should get a pretty good indication of what a trip that size will eat up.

If I keep a log, I should have a good indication of what the batteries will do on any given day. I have found already that the yellow light means very little since it will do off if I pedal or if the bike hits a downhill stretch. I think it is more an indication of the drain more than the reserve battery strength.

let the unscientific test begin.
test one

all this just pertains to my e z glide 250 watt hub motor. using 12 ah batteries for 24volts. First tests will be with two 12 volt sla batteries in series to give the 24volts.

First of all let me state that the lights on the throttle don't mean a lot except to let you know you are draining the battery. The bike will run an amber light for several blocks then switch back to green if you kill the throttle while going downhill.

I am using a measured distance pulling out of my drive with a full charge and measuring it when I return. Mileage is determined by yahoo map service. The route is simply reversed so the hills and valleys should pretty much even out.

Test one 3.28 miles round trip. I rode this wide open throttle almost all the time. Battery conservation was not an issue at all on this trip. The battery pack left my drive at full charge over 13 volts. It returned at 12.57 volts. Most of the last 1.5 miles the amber light was on indicating low voltage. I felt the drop in voltage only one time and that was on a long hill that I had to work to climb because the voltage was down some I suppose. The battery light returned to green for seconds when I released the throttle and coasted some. I did not do it for conservation but simply because the road was rough.

As stated before the bike would probably do five miles or so without too many shutdowns. The next test will be this same route while doing battery conservation to see how much if any difference it makes.

How big do you want.... I have a 250 watt that give about the same power as a 25cc weed eater friction drive. I paid 275 for mine but Now this one is pretty cool.

This guy is selling out his inventory of rear wheel drive because they dont sell as good as the front wheel. One of these kits went for just over two C's....

http://cgi.ebay.com/REAR-WHEEL-36V-...|66:2|65:12|39 :1|240:1318|301:0|293:1|294:50

The last ones have gone for more but you might still catch one at an off time. But I have recently heard that the ones with the emotor and go through the chain like the Izip have more power and you can use the gears to kick it up a notch, Of course I only found this out after I bought the hub motor. Still I am better off with the custom bike thing.

The unscientific test part two
Part one recap. full charge from my driveway to the senior center and return full throttle all the way.... 12.57 reading on each battery when the 3.25 miles ride was ended.

Today I made the same trip over the same roads. The only thing different was that I kept power consumption in mind. the speed was down a little bit since I rode the bike no faster than I could pedal it. I coasted free wheel only down all the hills. I used the pulse throttle method as I do for a friction drive. I would turn the throttle on just enough to help on long inclines... off completely during the downhill runs and run the throttle enough to get up speed on flats then let it drain off with the throttle off. I would repeat that when the speed got to slow.

The batteries read 12.83 each when I returned.

I have not checked but I think the battery pack leaves the house at about 13.25 volts as this is considered full charge. At 12.25 I think the motor shuts down until the bike regenerates enough power to run again. I find the difference significant but only if I were going a greater distance. For distance up to 4 miles I don't see a real advantage in the power management mind set.

Later today I have to work on the trailer range test. Right now I am recharging the battery pack but If I had to run another errand i have a second battery pack already charged. I will use the second pack on the trailer to test the range on the bike with both packs at the same time. I will probably give that a try this afternoon.

Unscientific test three
2sets of 12ah batteries in parallel wide open throttle

The weather was nice so I hooked up the trailer with my second battery pack and off i went. I rode the 3.25 mile test track.

test one was one 12ah battery pack wide open throttle. when i got home the batteries read 12.57volts.
test two was one 12ah battery pack with power conservation in mind.... when i got home the batteries read 12.83..
test three was two battery packs with wide open throttle. When I got home the batteries on the bike read 12.94 The ones on the railer read 13.02

I'm going to guess here when I say one pack wot all the way about 4.5 miles max
one pack power conservation 6miles max
two packs wide open throttle approx 9miles
two packs power consevation approx 12 miles

I really think the two packs will do better than my estimate for some reason.

I also have both packs charging at the same time so that should be interesting as well.

You are right batteries do tend to restore a bit with rest.

My main interest in this test is to see how far I can go with my own power packs and with methoodes of control I can easily handle. Mainly its so that if I need to go to home depot, I know how much battery it is going to take and If I need to be careful with it. If a destination is about four miles I can just go all the way wide open. If its over four miles. I will do a lot more pedaling. If it's over six miles I'll hook up the trailer. That was my purpose.

The only real serious pedaling is on one hill that is about three blocks long and pretty steep. I could not make it up at all without the motor.

copy of a post from another thread... this might be of interst to those who come looking for batter info.... or not
How I rig my diy battery packs.

I use an extension cord to connect all my diy battery packs. The big hole and big prong are ALWAYS ground. you wire twelve volt batteries series to get the volts up. then you wire them to the female end of an extension cord.

You wire the controller battery wires to the male end. The reason the ends are important where they go is that you don't want the battery end with the prongs on it. It will short out on the bike frame... (yes experience is the best teacher)

Now when you have that you can switch the packs around. To double your range you just make yourself a cord with two male ends. One end goes into each of the packs. That way they are in parallel. You have the same voltage but twice the amps. It will run twice as long with no switch. With most extension cords you have two or more taps. If you tap the cord with the controller end you are into the parallel system 24volts double the range.

Yes you could do this with even more battery packs. The number of backs is limitless as long as your bike has enough power on the drive to pull the traile

The reason this forum is so good for me is that when I write some of this stuff down I see it more clearly. On another thread my bike battery trailer came up and I remembered how well it pulled. I thought you know I need to test it without the bike battery pack. Just the trailer pack to see what if any effect it had. So In an hour or so I'm going to do just that.

I am going to move the battery pack from the bike to the trailer so it will be the exact same pack I have been using. I am going to make the current test ride and read the battery amount left. I am going to do it wot most of the way just to see what if anything is left. The last half mile is mostly down hill so I can manage even if it dies.