The nimh battery build...

[deacon]

Oh by the way I took the ten hour aa battery pack apart today and I have no idea what the devil is going on. Almost all the cells read either dead or very low voltage. I tried putting them into pvc tubes but I can't get a handle on what is going on with those cells. I checked the C cell pack and it looks fine. I have no idea what I'm going to do except sleep on it over night.

Tomorrow I'm going to try the hub motor with just that c cell pack, then I'm going to go with the hybrid pack and see what that does. I have a feeling it is going to do better with the lower wattage motor. The rhino is really 900 watts since it is 600watts at 24v but running at 36v. That system is so inefficient I'm not sure any modern chemistry will work on it at a reasonable cost.

The hub motor is really 250watt at 24 but I'm running it at 36v as well. I expect it will burn up any minute and good riddance. I am going to see if I can salvage a few of the AA nimh batteries for power packs for photo equipment I have but seldom use. Unless some miracle happens over night I will probably be able to save 10% of them.

One more by the by duct tape will take the wrapper off the china cells. I have about half of them naked but wrapped with black tape at the moment. That might be the problem they my be shorting out on my tester. I'll know more tomorrow.

 

[deacon]

I tore apart the aa battery pack and found all kinds of problems. I am pretty sure I cooked parts of it trying to parallel charge three batteries with a 6 amp charger to speed things up. I was hitting it an hour at a time but I must have gotten it one time too many.

It looks as though I am going to be able to save some of it. So I have to reconfigure my big battery pack tomorrow. Fried catfish is much better than fried battery.

 

[jdcburg]

Just an FYI - there is a Prius NiMH battery thread on endless-sphere at Endless-sphere.com • View topic - Prius Batteries - How to make them work Started almost 2 years ago but still current - 100+ replies. Might be something interesting for you there - jd

 

[deacon]

thank jd ill take a look. I have decided to buy enough aa cells once a month to add 2.5 ah to the battery pack until I have it hot enough to run the motor. I have a pretty good feel for it now I think. I am still learning about the batteries as I go.

I was able to save most of the cells only a few got cooked, I'm glad it was the aa they are a lot less expensive. At least that's how it seems. They are cheap enough to do that buy a few at a time and build a ever larger pack.

I will not parallel them with a high amp charger again. Or it might have been trying to use so small a pack with something that screams for that many amps. I'll figure out what cooked it but I'm almost positive it was the charger.

 

[corgi1]

Deacon,that Prius batt. site leads to other interesting sites too,I just looked at a bunch of it for a litttle over an hour

 

[deacon]

cool beans...

 

[deacon]

Looks as though there is a great deal of difference between what I have and the batteries they are using. Frankly I redid my pack last night and today and tried it loaded down at 24v and it was terrible. I couldn't even get it to turn the wheel. I think that the pack needs to be 36v for sure maybe even more. If definitely needs more amps I think as well. The reason I say that is that the throttle is calling for more power and the bike just does nothing. The battery still shows good charge so it's the amp thing I'm pretty sure.

I am going to run it 36v hybrid for a while as I build the size of the pack. I can take a day and weed out the bad cells now and then.

One thing I think is that be balance might not be as difficult as I imagined. The balance as i understand it is to prevent one cell over charging while trying to charge a weaker cell. That is the parallel thing going on. I like to tinker so what I plan to do is use a timer on my charger. When it hits 13.6 for the pack, I will just take it apart and check to see that all the cells are at least 13.6 I can charge those that aren't separately, just a little bit on the timer. I plan to consider any pack over 13.6 as charged enough. That will give me a lot of battery the way this thing drains.Also I only need to take the positive leads loose as the common ground is fine to check cell charge.

 

[deacon]

I just read on another forum that I am charging the battery way too often. Sla they say never let it run empty. The other forum say empty your nimh at least once a month. So I'm going to put the battery in the trailer as a hybrid and let it run till it is empty. I expect I will charge the sla five or more times before the nimh is empty.

That should be an interesting experiment as well. I never really thought of that part of the equation. If I charge it only a few times the balance problem with be negligible. Well I'll see how it goes anyway.

I switched everything over to the new schwinn girlie girl bike so it will all be interesting for the next couple of weeks. It's a little squirrely at the moment but it does pretty good. I need to rig a second brake to do that I might have to replace the front fork again. I have 26" fork with a 20" wheel in it. I know but I like to be a little weird.

 

[deacon]

I am beginning to think (after running data through my slow built in computer) the the most basic problem with my nimh test has been the fact that the c cells are way, over rated ah wise. For future figuring I'm going to rather them 5ah not 9ah as the mfg/seller on ebay stated. The aa packs seem more realistic.

Just for mass of chemistry I would thing that the c cell would be about 5ah so thats my new guess. (I know, I know buy a meter)...

So I am back to the AA batteries and am going to buy about 30 or 60 at a time to add to the pack until it is up there about thirty amp or more. Right now after the melt down, I figure the pack is at 17ah or so. The weight and size as compared to a slak will be much better.

The down side is for shot trips you can use smaller sla pks ten to twelve amps are pretty good. To even get out of the drive it seems I need a bigger nimh pack. I hope to test it as a stand alone all the way up the scale to figure out what exactly I need to run the motor.

That is in addition to the hybrid tests I am running.

So far I know that the 17amp I now have in the pack will not run the bike. I have sixty more batteries on the way. That will add five amps to the pack. At that point it should be 22ah. Still not enough I think on this power source but moving in on the right figure. Patience is the key to getting this guess right.

 

[Catfisher]

Deacon, I really appreciate the time you take to share your experiments. As it was said earlier, I want to learn from your mistakes 'cause I sure can't afford to make'em. I was really pulling for the NiMH C cells to work, as it would be something I could build myself.

Would you say, at this point, that the only 2 realistic choices for a 500 or 750 watt hub motor setup are SLA or LiFePO4 batteries? Doing a ebike commute at 8 - 10 miles each way I need reliability.

Any and all feel free to educate me, thanks.

 

[deacon]

Deacon, I really appreciate the time you take to share your experiments. As it was said earlier, I want to learn from your mistakes 'cause I sure can't afford to make'em. I was really pulling for the NiMH C cells to work, as it would be something I could build myself.

Would you say, at this point, that the only 2 realistic choices for a 500 or 750 watt hub motor setup are SLA or LiFePO4 batteries? Doing a ebike commute at 8 - 10 miles each way I need reliability.

Any and all feel free to educate me, thanks.

To be honest I'm not through with the nimh tests yet. I have high hopes for the hybrid pack the way I'm going to try it next. I believe that if you are running a high efficiency motor and want to pedal a lot the nimh pack will work for you. the problem comes when you want the BIKE to pull the hills not pull them yourself.

I doubt seriously that the nimh will provide the punch to do that alone. I think the Lithos for now are the only real option for a long ride, however the 'buyin' for the power I need is still five to ten times what I pay to build a bike. It just is not something I'm willing to do. I live in a town called high point. it is called that for a reason. The geography here is terrible for bikes. On a 17ah sla battery I can get five miles on one of my rides then the batteries are almost useless.

I have said before If I was going to ride to work on the bike, litho on a high efficiency hubber bubber would be the way to go. I tinker so it isn't. Of course a brush less motor on a chain drive would be as efficient I expect. Then the litho might be the absolute best thing for that setup as well.

Hold on for a while longer, if you can. I am closing in on a definitive answer to the nimh pack. One thing I can tell you for sure. The testing has been skewed by the manufacturer's dishonesty with the battery strength. In looking back over my results I can tell you I was close before I cooked the batteries, but had way over estimated the ah of my pack. It the ah had been correct the battery might have been close to what I'm looking for.


Just before the melt down (I have not written his before because I haven't been able to do it again) The bike actually accelerated half decent. Even then on the same ride it wasn't consistent but it did accelerate a couple of times pretty well. So give it a month or so If you can and follow the hybrid test as well.

And frankly I can't afford it either I'm just too darn stupid to do all the research that would tell me not to even try lol. or maybe I'm just rock hard headed.

I really have not give up on the nimh yet. If I get the power the cell management will become an issue. Even if and when I make the power setup, I still have a lot to learn about managing the home made battery pack. So lets stay at it, like you a modern power source that can be built and managed inexpensively is the holy grail of ebikes for me.

 

[Happy Jack]

deacon:
I also hope you get the Nimh to work. I would love to pair them up with my SLA's.

 

[zabac70]

Inexpensive e vehicle is holy grail for everybody who has interest in it. For example , if someone has friends in US Army , he can obtain NANOSafe batts , which are Carbon based chemistry (nano tubes with different potential) , much less expensive than LIthos (any kind) and has about the same (or better) energy density(similar weight) as Li based batts. Used in electric combat vehicles (and some experimental stuff). And no , you can't buy them directly from the manufacturer (g men has something to say abut it).
For now , for ordinary people , LiFePO4 is the best solution, regardless of the rest of the system on the bike. Better yet, if paired with brush less hub motor. Of course , it comes with a price , so anything that will do you a job is great (meaning , whatever you can get your hands on). NiMH is somewhere in between (for the middle solution I prefer NiCd ) , but not that cheap if you approach it in the right way , meaning , using BMS and dedicated charger (and right type of NiMH cells).

 

[deacon]

I am beginning to like nimh better all the time. I fried the aa battery pack by using a TOO HOT charger. But I have been able to successfully salvage well over half that pack. So it would meet my, be able to repair it myself, criteria. Mixed with the sla to pull the hills, if it works, it would cut down on the size of both the pack needed and might out range litho. That is probably a pipe dream, but I will see. At the moment I have the most faith in the hybrid battery system. It would be a system most likely not something bike, or battery manufacturers would bother with, but that does not mean it won't work for me.

From what I hear they are still working on a light weight lead acid battery. One made with some alloy. That would be great. If they could get the weight down, I would prefer to haul around 30 ahs of those.

 

[jdcburg]

I'm sure it's been said here a million times, but old failed tool packs can be a good source of cells of different types. Sometimes if you take one apart you'll find that 1 or 2 cells are bad but the rest are fine. Those can be decent quality cells that are made for high-draw use. If you ask around at hardware stores you might find there is a local tool repair place that would be willing to give you defective battery packs - jd

 

[deacon]

I asked if home depot recycled but they wouldnt even talk to me lol/

 

[zabac70]

I don't understand it...Here, where I live (and we are a low tech country in terms of industrial surpluses - there isn't much motors or battery's on scrap yards and we don't even have salvage yards) , I can find a lots of power tool parts (including battery packs from battery drills) , so I don't know how you can't find it in America ? Any bigger tool shop must have some damaged batt packs or surpluses or returned ones (warranty issues) and you don't really need the plastic , just cells. Cheap ones (replacement battery packs-12 or 14.4 V / 3.0 AH) cost about $25 here , so it must be cheaper over there.

 

[Catfisher]

Because I am so new to all of this, and so ignorant when it comes to electricity; I am reading tons to catch up a little. Someone posted this link and the organized way they pesent the information has been very helpful.

Information about Battery Packs

This paragraph under AMP-HOURS caught my eye.

" In general, the size and cost of a cell will scale directly with its amp-hour capacity. To a first order, twice the amp-hours would mean twice the size, twice the weight, and twice the cost. In practice this deviates a little due to different packing densities and production scales, but it's usually pretty close. For instance, the familiar 'AA' NiMH has about 2 Ah, a 'C' cell has 4 Ah, a 'D' cell is about 8Ah, the large 'F' cells are 12-13 Ah, and double-D cells are 18-19Ah. "

If 'C' cells have a basic limitation of 4 Ah, why would someone advertise them as 9Ah ( I think that's what you said)? So is this paragraph accurate in general? If it is, then is the only way to increase Amp Hours to double a set linked in parallel?

 

[deacon]

In general it is. I have no idea why they are adv them as 9am but a lot of people are suddenly maybe they are. I can't swear to the 4ah either someone just said it somewhere and it sounds more likely than 9ah by my calculations. I have no idea what the truth is it's kind of like the coca cola formula. A big butt secret/...

Lately the AA have gone from 2500 to almost 3000 but I count them all at 2500 anyway.our of them make 10ahs. This project is not going to be cheap just cheaper lol.

I have decided that I can't wait I'm going to wire the packs to run on the coast on the nimh and gut it out on the sla pack. I can add more to the nimh to get better performance on the coaster but I want to see how the adding and removing the sla effects the bike. I just have to know lol. Tomorrow's project since it's supposed to rain.

Ps. if the manufactures number are correct I should have plenty of coaster power. If not I will need to add more batteries. I have more on the way anyhow.

 

[deacon]

I broke down and order 5 more ah of batteries. I have ten more AH's in the mail, or so I think. By my rough calculations which are probably way off, that will make about 27ah which should be enough to run the bike on the flats.