NEED ADVICE: Best way to build battery box- LiFePo4

[chris22104]

Hi guys!
I've ordered my Ping 72v 15ah pack. This is my second e-bike, but my first lifepo4 battery. Being a full suspension bike without a center triangle frame, I'm going to have to fabricate a stainless steel battery box that mounts off the back of the seat post . A few questions:
1. I've read about these type of cells sometimes swelling, and that it's better to have a nice tight fit in the box. Is there any truth to this, or would it be better to have room for foam rubber cushioning on all 4 sides and the bottom? If the latter, how much foam rubber cushioning is necessary (space-wise around the battery,) so I have some idea how big to size the box.
2. The pack is available in one or two pieces. Considering it will all be going into one box, wouldn't the one piece configuration be better?
3. Once the s.s. box is built, assuming no cushioning (tight fit,) should I swiss cheese the box for cooling purposes?
4. Should I mount the bms on the outside the box for better cooling purposes?
Thanks guys!
Chris

 

[dogman dan]

That's gonna be a lot of ping hanging back there. I like to armor my pings with something first, then fit into metal boxes with just a bit of padding underneath. Possibly just a cardboard scrap. then I shim the ends to a tight fit with pieces of closed cell foam. One ping is armored with aluminum sheet, the other with plastic from a storage tub lid. I cut and fold into a very tight, custom box with an open top for the bms.

I'd say if possible, some kind of two boxes, pannier style arrangement would be best. Only the bms needs to be ventilated. When I carry two pings, getting the second one low in a pannier helps handling. Still handles like a whale with 50 pounds in the panniers for a long trip.

 

[jimw1960]

You are going to hate the way it rides with that much weight hanging off the back of the seat post. Why don't you build a box to fit in your triangle?
A lot of good ideas for battery boxes here: http://endless-sphere.com/forums/viewtopic.php?f=3&t=12847

 

[wineboyrider]

You are going to hate the way it rides with that much weight hanging off the back of the seat post. Why don't you build a box to fit in your triangle?

It's a full suspension bicycle. Most FS bikes don't have very much (if any) triangle? I have the same problem I have a FS bike that I would like to electrify, but want a nice place for the batts.
8)
Ykick has a pic. of his controller in a cool place that I might borrow. In fact, it's perfect for my mongoose...?

 

[chris22104]

I have no triangle. It's going to have to be up under and partially behind the seat. I'm thinking in a two piece configuration; one on each side of the seat post. This way, it won't all be hanging off the back. So a tight fit for the pack would be best around the sides of the box, with some foam rubber under the bottom? Again, each half of the pack will be enclosed in it's own s.s. box. Pics below. From those who've been there, your thoughts and ideas would be appeciated!
Thanks again guys!
Chris
PS: Note my full capture s.s. 3/8" and 1/2" torque plates I had water jetted...
http://img.photobucket.com/albums/v457/julian108/CopyofIMG_7660.jpg
http://img.photobucket.com/albums/v457/julian108/CopyofIMG_7661.jpg
http://img.photobucket.com/albums/v457/julian108/CopyofIMG_7662.jpg
http://img.photobucket.com/albums/v457/julian108/CopyofIMG_7663.jpg
http://img.photobucket.com/albums/v457/julian108/CopyofIMG_7664.jpg

 

[Mark_A_W]

I think you guys should get different bikes - ones with triangles.

Or split the packs and put the cells either side of the frame.


A rear battery is a handling mess, and I broke 2 racks, a seatpost, and a frame with a rear battery.

 

[chris22104]

I know it's not the ideal bike. But this is it for now. I don't intend on using a rear rack. I can't with the rear suspension anyway. I can mount the two seperate boxes from the 1/4" steel rods under each side of the seat, as well as a couple spots on the seat post itself. This really seems to be the only location the two packs can go. Again, any other thoughts? Thanks!

 

[Drunkskunk]

instead of under the seat, try either side of the top tube. That much weight on the back of a hard tail is a problem. but that much weight on the back of a sull suspension is going to be a handaling disaster.

 

[auraslip]

I don't intend on using a rear rack. I can't with the rear suspension anyway.

It's actually been done using hose clamps.. I think he had to bend the rack though. Very important to make sure it's completely immobile. That's a big issue WRT to handling. Mounted to the seat post it'd be to easy to swing around.

As far as splitting the pack, you'll have to do some disassembling unless you message ping ASAP and ask him to split the pack up for you. If you manage to split the pack, defeinitly mounting it in two boxes on either side of the TT as far forward as you can to keep your knees from hitting it when you pedal.

As dogman says, shim it with cardboard or something similar. Cooling the bms may or may not be an issue.

 

[chris22104]

The pack is coming in two pieces, and the two halves are the exact size of the boxes shown in my pics.

 

[chris22104]

I dropped the bike and battery packs off at my machinists today to have some stainless boxes made and mounted on each side of the seat. The weight will be supported off the heavy gauge frame supports in front of the seat post tube, and the rear of the boxes will be supported with s.s. plates at an approx. 40 degree angle, going up to an adjustable collar higher up the seat post. All adjustable so the seat can be raised or lowered as needed. It should be plenty strong, and no chance of side to side movement. Unfortunately, this is the only place on the bike this large of a battery will fit without interfering with my rotating feet/ knees, etc. Poor initial choice of a bike on my part (with no triangle,) but considering I'm using it on the road only, going in a straight line 20 miles at a time, I don't think handling will be a big issue. I'll post some pics as soon as it is fabricated....

 

[dumbass]

I don't know the size of your 2 packs but I have 2 TunderSky 24v packs and I mount them in a Currie (EZip) rear rack. The rack mounts to the rear dropout assembly and the back of the seat frame. You would need to modify to allow for the suspension but this is a small problem. The rack is made from alm and I custom made 2 HDPE plastic boxes that slip quickly in and out of the rack. The rack even has a lock to hold the pack in. The rack is avable for under $50 at Currie on line and else where.

Bob

OOPs, sorry it's $55 now.

http://www.curriestore.com/1271-ezip-rack-rmb.html

 

[maydaverave]

I went through four racks before I found axiom racks and haven't had a problem since. Their stuff is cheap and over built I would think even their seat post rack would last you for a while.
http://www.axiomgear.com/products/gear/racks/rear-racks/phoenix-le-seatpost/

 

[dogman dan]

That might work. It always seemed like that mounting spot would be too wide for me to straddle a battery.

I constantly rub my shins on my frame tube mounted battery box, but you soon learn to pedal a bit bowlegged.

 

[dumbass]

That might work. It always seemed like that mounting spot would be too wide for me to straddle a battery.

I constantly rub my shins on my frame tube mounted battery box, but you soon learn to pedal a bit bowlegged.

Actually I had (have) a simular setup on my old bike. I am 6'2" tall so it wasn't a problem to me. And I was running a Cyclone motor kit with an extra long crank shaft. This tended to pull my legs and knees away from the pack. You can also buy special peddle arms that are offset for mounting e-motors and packs. The offset crank arms widen the peddle path so it wouldn't be a major problem.

Bob

 

[chris22104]

Thanks for the ideas guys; all very good. I'll see what my machinist/fabricator can do, and will post some pics as soon as available....Chris

 

[Dave Sloan]

Your arrangement looks like a good one as far as strain on the seat post is concerned. The best thing to do is ride around with those cardboard models with some lead weight in them just to see what feels best. I would hate to see the results if the stainless steel was to make contact with you. I would put some protection for your legs in case there is a possibility of contact

 

[chris22104]

OK, almost finished! My fabricator/machinist took forever, but what a sweet (and sturdy) custom fit stainless steel set-up he made! Now just to finish up the wiring....