The nimh battery build...

[deacon]

Not the final word on the nimh but a prelim conclusion not a very good project to do yourself. If someone had told me that I would have done it anyway, so take it for what it is worth.

I did find out a few things worth knowing. I can build a reliable battery pack if anyone comes up with a new cell that will work. I would like for it to be the light weight lead allow and acid cell. If they continue working on it, the it will be the cats pajamas. The reason they are still working on it, is that some batteries need to be able to release their charge quickly to start a car ect. Of course older less efficient electric motors need that as well.

So I plan to try to use then min a slak hybrid system. I have two versions that need testing now. One is an 18ah nkpk to be paired with a 17ah slak stytem. The other is ten ah nkpk and very old 12ah slak. So more testing is in order.

 

[deacon]

I got a really interesting test ride today. I rebuilt my test bike with an extra rhino drive. I threw together a really old worn out slak of 12ah with year old batteries. i could only get about a 13.4 charge on them, but I matched them up with the nkpk of 18 ah and off I went. I was totally shocked. The response to the throttle was better than I have had with any battery setup at all. It had huge torque, It would pull me off from a dead stop, and I started to climb a big hill from an almost dead stop at the bottom and it zipped right up it. It had acceleration no matter what speed i seemed to be doing.
'
To be honest I was dragging a junk trailer so i didn't go wot so I don't know how the speed was. I came in with well over 13v after a mile ride with batteries that really are in terrible shape. There might be something to this hybrid battery system but I'm not ready to say there is yet.

The acceleration and the torque is all in the slak im sure of that.

 

[deacon]

It's the strangest thing but suddenly the batteries are charging to a high capacity. I ran the test bike a second mile and the batteries had about an hour at one amp to charge they were up to over 14v after resting. '

The came back in after the mile at 13.8 or so. Very respectable numbers I would say. And the bike has great torque on the hills. The test bike is pure junk but it really did run well. I have a lot more testing to do but it seems that for now it is better news than the last few days have been.

I want to do an extended range test on the old 12ah slak nkpk combo meal to see what it does. I would love to buy a 7ah slak next time and mix it with the nkpk i have now. I doubt that will work. It would be way to convenient, someone would have thouight of it by now.

 

[zabac70]

Battery gremlins ?

 

[deacon]

1st cousin to the bike gremlins I have living in the shop. Today they have been feeling their spring fever for sure.

 

[deacon]

I decided to try to build my own NIMH battery pack. If I had listened to everyone and just done a thorough research and did all the math and theory, I probably would have realized that with my junk bike and antiquated drive system, that it would be a monumental waste of time and money. If I had gotten discouraged along the way and threw up my hands at the failures it would have been just exactly as they predicted that it would be.

Instead I was determined to use the information I had learned along the way. What happened was tha along the way I combined the Nimh battery pack with an SLA battery pack and go some pretty unique for older bike drive systems. They supply SLA battery packs with brushed motor kits for a reason more than just cost. SLA packs give you max energy whenever you call for it. Yes it does drain your reserve quickly. But if you are driving a 68 Dodge Charger do you really want a governor.

 

[deacon]

I decided to try to build my own NIMH battery pack. If I had listened to everyone and just done a thorough research job and done all the math and theory, I probably would have realized that with my junk bike, and antiquated drive system, it would be a monumental waste of time and money. If I had gotten discouraged along the way and threw up my hands at the failures, it would have been just exactly as they had predicted.

Instead I was determined to use the information, I had learned along the way. What happened was that early on along the way I combined the Nimh battery pack with an SLA battery pack and go some pretty Interesting results. So when the NIMH pack didn't perform well, I tried the hybrid system again and so far I have gotten some good results for the older bike drive systems.

I think that they supply SLA battery packs with brushed motor kits for a reason more than just cost. SLA packs give you max energy whenever you call for it. Yes it does drain your reserve quickly. But if you are driving a 68 Dodge Charger do you really want a governor. That seems to me to be what the Nimh battery pack was. When combined with a sla battery pack the governor is off and the battery drain isn't as noticeable as with a pure sla system. At least it seems that way at the moment.

What I guess I am trying to say is guys don't be afraid to try things and don't be afraid to fail. Every time you try, even if you fail, you learn something new. Nothing beats a hands on education. Now if I could only remember all this worthless information next time I try something I would be good to go.

 

[jeff96]

Deacon, I've been following your progress with the hopes of building a similiar nimh pack. I read an interesting article which seems to address some of the issues you've had with the c cell batteries. Information about Battery Packs

It seems that the capacity of the cell may be over-rated, realisticly it's more like 4000 mAh vs the advertised 9000. It also discusses a discharge or C rate, which corresponds well with some of your conclusions.

 

[deacon]

Ill take a look and i thought it might be over rated... It's good information and i think the hybrid pack will be useful to double the range without all the weight but mine really has to have the sla as the gate keeper.

 

[deacon]

Don't ask me why but the batteries ran better today. They seemed to have drained fast but I only went a single block and they say they drop quickly then level off. The batteries moved the bike along pretty good except for the first hill. I had to pedal some but the bike motor helped me up the hill pretty good. With a better propulsion system, i think the batteries might be alright. I still plan to use them along with my slak. But every now and then I will test them by themselves to see how they are doing.

 

[deacon]

After the fiasco yesterday, I rebuilt a trailer with sealed bearings for the sla pack. I came home on the nimh pack and slightly impressed with them. Since I was forced to test them real world I found this to be true.

On my test track, If I head out one way, I have to make a left turn at the end of short block and go right into a tough hill. It isn't long but it does have a significant grade. The first couple of time I ran the nimh pk it wouldn't even get to the hill with enough kick to help at all.

The last time I checked them alone they did put me there with a little punch to help me up it. So i never did more than a single block before I declared them porkish. Yesterday I had no choice, if I wanted to make the last 1/2 mile on top of the bike rather than walking beside it. So I ran it home that last 1/2 with almost a totally drained sla pk. The mostly nimh pk (I think) helped me significantly.

I have a few things more to do with the rhino bike, tie the motor down and beef up a couple of joints on the trailer. Then I think I will put the hub motor on something and give the batteries another test.

After a night's rest my nimh batteries always start at about 13.6 +/- .1v Just my readings though.

Even on the rhino alone the last time I ran it with just minor tension the bike had pretty good speed. I think the hub motor geared down on the pedals might work pretty good. Even the rhino geared down and with minor tension on the drive might do well. I'm going to try both.

I will try to get to the rhino with minor tension geared down today. I swapped out the chain ring yesterday to gear it down. Having to struggle home yesterday made me decide that the chain ring needed to be geared down just in case. I had geared it up to keep the speed up with the rhino going uphill, but it makes it though to pedal assist at low assist from the motor. Fortunately I kept all the chain rings from the small bikes I tore up for parts, so I have plenty to choose from.

Ps just as a passing note I stripped the threads off one of my coaster rear wheels. I am down to just one, and it may not be reliable, so I think I will be bike shopping soon. My favorite thrift store has a shortage of bikes lately. Mostly they have 16" and 12" bikes. Maybe one 20" and hardly ever a 24" or 26". I may have to do some far a field looking for a bike for the hubber bubber. Since it has it's own forks, I can switch them out in most any frame. The balance isn't great in a small frame but it is doable. I tossed all my 26" junker wheels a while back and now I regret it. There is a frame for a 26" road bike at the thrift store nobody wants, because it is really in bad shape wheel and seat wise. I could use it just fine, if I had a wide rear wheel but alas mine is probably part of a car or washer now.

One more note on thrift store bikes. If I buy a 20" for the rear wheel, usually it is a girls bike that has the best rear wheels. Girls tend to do less riding of their bikes it seems. Daddy probably sticks it in the garage between rides. Anyway their wheels seem to be in better shape, but the tires are always white lol. I keep every black 20" tire that crosses my path.

 

[deacon]

Well scratch any further tests of the nimh pack alone. The bike runs like a pig and the output is flat and too low to be of much use. I still might put the hub motor on a frame since it is only 350 watt. The controller is probably pretty low power it might do something but I doubt it. That is a test for a day when I am REALLY bored.

What the thing really needs before I get any useful results is the wire ends I'm waiting for. With those I can get a positive connection every time. I can also vary the wiring as well. That would give me some really useful information.

I am going to make one test right now. I have a 12ah set of sla that is down to about 13v and I have a set of nimh which are up to about 13.5 or they will be before I test this theory. I want to see if the nimh batteries will raise the level of the sla pack while at rest, If so I can ride the bike to the lake on the sla batteries alone. that I know will work just fine. Then I can hook up the nimh pack and let it balance out while I'm having breakfast or lunch, then ride home with both packs hooked up.

I can test the balance thing out in my shop. So that a real world test won't leave me pushing a bike home.

 

[deacon]

As expected the nimh pack raised the voltage of the low sla pack. What that means in the real world is another thing all together.

 

[deacon]

I put my hub motor on a bike to try the nimh batteries and they didn't even turn the wheel. If I turned it, they would keep it moving so long as there was no load on it. I think it's time to build something non bike related using those batteries. I'm open for suggestions.

 

[jdcburg]

Hi Deacon - I found this site NiMH battery modules | Colorado Advanced Battery that builds NiMH packs that look powerful. They certainly aren't cheap! I read on another ebike forum that a guy uses these because his high-draw bike eats other batteries for breakfast. I've heard the Prius uses NiMH batteries and that must draw a lot of current. So I'm confused about why your system is so weak. Could be the batteries are overrated or you're losing power (amps) in the wiring or battery connections. I don't know if there is a way to check the resistance through a battery pack, but I wonder if there is some fundamental problem with your duct tape and foil packs. I remember my old days working in a garage. A bad connection at the battery or solenoid would cause the high draw of turning the starter to fail even though the meter said the battery had a full charge. It was so common the first thing we did was pull the clamps and clean the terminals. What if you found some tubing the right size and made some packs where the batteries stack nose to tail like a flashlight. 5 cells = 6V, 10 = 12V, etc. PVC and ABS pipe have different glued or screw-on caps available. That stuff is easy to fabricate and drill. Put different colored wires at each end and you can put them together in series or parallel. Might be worth a try - jd

 

[deacon]

Beats me but I have worked with batteries in my photography when i built lights. I have never worked with nimh but nicad and alkaline never had any power drops from the construction.

I have two types of batteries the c cells and the aa cells. both packs are pretty anemic but the C cells may be a little worse. Yesterday I put each pack separately on the hub motor the aa pack would turn it but the c pack which is supposed to be stronger wouldn't move it at all.

I know from my previous tests that the c pack will last longer but it seems to lack any punch at all. It could be that the packs would need to be massive to really work well. Or maybe they are rated incorrectly.

If the C cells are really 4ah not 9 then that might explain it. In that case the battery pack would be only 8ah and the aa would be 10ah giving it a little more punch. Most of the c cells on ebay are rated at 4ah and cost as much or more than the ones I bought,

I might just redo them into pvc pipe for a continuous no resistance circuit but I honestly dont think that is the problem. Still it is a minor adjustment so why not. I may find that I should have stayed with the aa batteries.

I am still evaluating their usefulness. I did find something unexplainable in my mind at that moment. I might figure it out later. The AA pack would turn the hub motor with no load but when I added the c pack it actually killed the AA pack so that I had to turn the wheel to start the motor to run on the battery pack. I think you might have something on the wiring situation now that I rethink it.

I think after I get the hub running again. I will take a crack at redoing the battery packs into long tubes like a flashlight.

 

[jdcburg]

Yes I think something's wrong somewhere. Running that 350W hub motor on the bench shouldn't take any juice at all, especially if you start it by hand. Isn't that a 24V that you are runing at 36V? Even an 8ah pack should be able to do that. Maybe the NiMH electrodes don't like aluminum foil or something weird like that. I'll be interested in what you find out if you try a reconfiguration. Also that $25 Turnigy watt meter might be a good investment if it tells you anything about current draw or output - jd

 

[Happy Jack]

Also that $25 Turnigy watt meter might be a good investment if it tells you anything about current draw or output - jd

Plus one on that advice!

I have worked at an electric utility company.
You MUST have a good meter to measure 1)Volts 2)ohms 3)Amps cause that darn electricity is invisible.

Amp meters are the hardest to get a good grasp of.
They often need what is known as an external shunt to keep the meter from getting fried with too much juice. Most small VOM meters will only handle a maximum of 10 amp DC , so they are pretty limited on an electric bikes that can easily pull 20amps +.
Half the old VOM meters I get have the internal fuse blown cause some former user flipped the dial to amps, and blew the fuse.

Those little Watt's Up meters can handle internal 0-100Amp DC peaks !!! , AND they are not just meters!
They act like little mini-computers to tell you what is happening with your motors load, your battery chargers output, your usage on a ride etc.

Get a good Watts Up Meter (or cheap Turnigy Meter) and a good digital bicycle speedometer and you will no longer pee-in-the-dark in your experiments. I use my Watts Up in the old motor-home, on my cell phone batts and charger, my laptop batts, my fishing boat, my generators, my solar cells .....
Best $49 I have spent all year. I am far from an expert on electricity , that's why I like them little "computational" meters to do the math for me.

My humble opinion is to get the W.U. meter and stick it out with them nimh's awhile longer. Most DC motor /battery problems are rooted in "either motor is drawing too much for you, or the batteries aren't putting out enough".
Without good numbers, how you gonna know for sure what the weak link is?

 

[BossCat]

Great minds think alike and all that....

I have just ordered one of those Turnigy 130A Watt Meter Power Analyser Watts Up thingys off ebay as I had read good reports about them. I think it'll come in handy, letting me know what state my batteries are in.

Regards
Tom

 

[deacon]

I took a look at fifty bucks that going to have to wait. It is probably something I will invest in should I continue building batteries e