My new NiMH battery packs

[s4w2099]

I recently got 210 NiMH cells from ebay for my high voltage electric bike (260Vdc). 260Vdc is very dangerous, your death is guaranteed if you get hit by it so dont take the idea from me if you are inexperienced with HV machinery. I just wanted to show how I built the packs inspired by someone in this forum that did something similar some time ago. I added some nice features to mine.

The construction only needs 1/2" PVC pipe and caps, springs, 1.5 inch bolts and nuts for them.

The batteries:

The cap:

Now drill a hole right on the center of the cap to snugly fit a bolt through it:

Put the cap on the previously cut to length pipe and fill the pipe with the batteries.

Slide the spring inside another bolt and slide it through the hole on another cap. The spring stays compressed in between the bolt head and the cap. This creates preassure against the batteries making a very nice contact. The bolt head must be small enough to fit inside the pipe.

Repeat

I was talking to Zeus last night and its a good idea to glue one of the caps to seal it off nicely and the other cap could be made removable (for servicing) by threading the pipe perpendicular to the batteries and inserting a bolt across the end cap to hold it in place.

The "subpacks" as I call them, can now be connected in series by using wires and terminals in between two nuts per bolt. Bolt resistance is not an issue for me as peak current will be about 5A and I used 5/16" bolts.

[Blutoy]

Daddy likes

[gotwind2]

Looks way too dangerous for my tastes..

I have always questioned why AA batteries are circurlar in sectional area.

Surely a square section AA battery would increase capacity and stack far better.

Just a thought.

Ben.

[s4w2099]

Yes, I guess rolling them is easier. I dont mind HV as I work with it for a living so I am quite used to it.

Though I just wanted to show how I made the subpacks in case someone was looking to build a pack, they can also be connected in parallel is wished for.

[s4w2099]

BTW, each subpack is 15V nominal

[zeusmorg]

 I wish my packs were going so smoothly! I tried making battery boxes out of some old acrylic I had around,, bad idea!

 Looking for a different solution now. I want to keep my weight low, and the areas I have available to place them are rather difficult to utilize. Nothing "off the shelf" I've found will work.

 Of course I am attempting to use stuff I have lying about. And it never fails,, I'll hang on to things and then finally toss them just to find, well s*** that would've worked perfectly! I tossed some computer cases recently, and the sheet metal out of them would've been easy to make into battery boxes!

[ghurd]

Looks good!

The inspiration could have been Norm.

You wouldn't catch me spitting in the direction of 260VDC.

There is a "graphic" train video going around that reminds me why I like 12V.

G-

[Bruce S]

Question about the tightness of the batteries in the PVC, just how much room is there in there?

Are you using thin walled or thick? Since Ni-based batteries will get "warm" during charging, I'd be a little concerned about the middle section getting much hotter than the ends and not being able to vent.

I do like the idea, similar to Norm's of using bolts and springs to keep positive pressure for a good solid contact.

Just curious, but why so high a voltage? going to be using this on a h-voltage DC motor?

Looks very well done.

Cheers!

Bruce S

[Bruce S]

G-

That is a very good video of why not to play with high-voltage!! Yuck-OO

Bruce S

[s4w2099]

I thought about the temperature rise but I will be using very low current because of the high voltage. The thermal conductivity of PVC is about the same as that of plastic used in toys/cell phones and other electronics that have batteries inside. The batteries have about 1mm play so they dont really bounce inside. I do need to make some little vents on them in case they get hot (but I doubt it).

Because of that reason I dont think this is a good idea for low voltage machine. At low voltages you need more current to get the same power so they would just get cooked inside.

Anyways because they need charging, there will be a thermistor inside to monitor the charging process. This thermistor could be used to monitor battery temperature as well when the pack is being discharged.

At work I often find myself dealing with DC voltages of over 1000Vdc so I dont really mind 260V. There are procedures to do this safely but I do not recommend this to someone that have never dealt with such voltages before.

It is just a personal opinion but I think electric vehicles should not be low voltage just because its too hard to squeeze the needed amount of power at low voltages. Just think about the controller that would need to be built to handle 20HP or so at say 48V? Thats about 300Amps. Imagine now the stress that such currents impose on the electronics, wiring etc. There is a lot of efficiency to loose because of that.

Again this is just MY opinion.

:-)

[Bruce S]

Seems to be a "learned" opinon :-)

If you've worked with Z- on his 48v'er you probably saw the thermistor's built into those packs. They work perfect for these voltages.

Fast acting and most of the times, will reset once cooled.

I tend to recycle these out of burned out NiCd units, so if you're in need of some to test the thermistor theory let me know. An enevelope of them wouldn't weigh an ounce.

Most vehicles in the over 500lb range are already in the high-voltage range. Windstuff Ed- was working on one and there's a few e-truck owners on here I believe.

For me, I believe voltages can and should be chosen for the job at hand.

Even the newer CFL ballast we're seeing as replacements are now listing 120vdc and usable as well.

In Germany, there is/was a motor designer who designed velomobiles around AC motors, sighting better control and more effiecent use of available power.

Beyond; building this pack up. What are your plans for it?

Cheers;

Bruce S

[Norm]

Just like you have it ...but cut the pipe in half, a small hinge to swing the two halves open.

a short piece of pipe that fits over it break the

halves open like a shot gun....load both halves

with the batteries swing the halves shut ...slide

the short section of pipe over the end of the

two halves...locking it in the straight position.

Worked for me with AA NiCads.

[Madscientist267]

Ouch... Yeah that sucks, although it almost looks like he maybe never even felt it...

I think I'll stick to <=48 just to stay 'uncrisp'...

Steve

[s4w2099]

Thank you but I have lots of thermistors. These will go into an electric bicycle with a 2.5HP motor. So not a toy anymore. i really would like to use it to commute daily.

I have done some tests already at about 170Vdc and I tell you it was a blast to ride that bike. No problems with hill climbs or anything. And gets up to 30MPH quickly.

My plan is to keep this as practical as possible. So in the future I want to use a 3Phase AC motor if this version does not work out ok.

The reason I started this project with such voltages is because I have everything I need for it at hand. I had a motor controller that I made a while ago that can do up to 600V@50A (I will only use 5A peak though) its a bit overkill, I had the motor also, bicycle, the throttle Zeus is giving it to me for free. I will have to get fuses and interconnects now.

If anytime I need to reconfigure the voltage to use another lower voltage motor I can do it and controller will still be OK until 50A. Would just need to get another motor. I think 100Vdc@2.5HP motor would be nice.

[dnix71]

I guess you don't plan on riding in the rain. Otherwise you might pedal real fast if something shorts.

[divemaster1963]

Your work reminds me of the hybrid trash truck that we are using at the City of macon,ga. It has a battery pack made of 600 aa lithium ion batteries. It looks like a small vw straped to the side of the truck. Go to city of macon web site. I think they have a photo of it. I'm one of the mech. thats get to have fun working on it. the other mech. don't want to touch it. healty fear. Caution comes first.