View Full Version : Battery mounting...

12 September 2010, 0519
Anyone have some awesome battery mounting to show?

Here's my alltime fave, thanks to shakey Jake:


I know I'm gonna drive Ed nutty (er) by posting the link, but my story is here:

Here's the text, and maybe if I have time I'll post the photos, which are the best part, here, but I've been told we're going to breakfast... :D

The other bit of fabrication you need to tackle on a conversion is the battery mount. In most amateur conversions this is the least elegant part of the project- with all kindness, most builders put together some variation of steel angle-iron or box, and then cover it up with a fairing. My problem is my old buddy Bryce Larrabee. He’s a machinist and fabricator, and every time he sees an angle-iron construction he says it looks like a farmer built it. I can’t escape my early imprinting.

The other part of my problem is my basic notion of the beauty of a motorcycle. A pure motorcycle is a pure machine- one of the highest expressions of “form follows function”. A beautiful motorcycle is a design where everything is essential to the operation of the machine, and is honestly, and elegantly, presented. The batteries on an electric motorcycle are a huge challenge- it seems like there’s no way to make them look like big blocky afterthoughts.

One solution is the Brammo frame- it’s tied together with an extruded aluminum I-beam where the batteries sit. They’re using six Valence batteries, and they’re riding above and below that I-beam. It’s a logical solution, but the heaviest part of the entire build- the batteries- ride pretty high on the bike, making a fairly high center-of-gravity. This is the same strategy that Brammo uses on the Empulse- a naked-streetfighter/roadracing style, that is just awesomely cool looking for all the right reasons. Every bit is visible, and it’s all presented beautifully.


Another beautiful solution is the MotoCzysz design. Using smaller and more batteries- I believe they’re using the A123 cells- they assemble packs that attach to the main central core member, shown here.

This gives you something that looks like this, in full race trim:


(Photo courtesy of the Awesome Awesomeness of Asphalt and Rubber- thanks Jenson!)

Construction like this may be beyond the scope of an amateur builder- indeed, conceptualizing something like this is beyond the scope of normal mortals- something I don’t consider the designer, Michael Czysz, to be. There is simply nothing that I’ve seen that this guy hasn’t touched that isn’t brilliant- including his riding prowess, as demonstrated at the TTXGP this summer. But I digress.

The Czysz design inspired my own drawings to make modular battery packs center mounted, that could take various sizes and shapes of batteries, depending on what I decided to run at a future point. Here’s my mockup.

This array of four packs could hold 96 Headway 10aH cells, 24 40aH Thundersky cells, even about 22aH of AGM scooter batteries. In theory.

In practice, I made a rudimentary rack on my tube frame that allows me to clamp batteries in place. It’s made of aluminum, and can handle shelves, as shown here, that hold these AGM batteries, or lithium cells like Thundersky. It could also handle the packs I showed above, or an array of Headways. That said, it carries the batteries really high in the frame- although this bike weighs in at 250 lbs, (very, very light) the center of gravity is really high. If I added another 100lbs of batteries in this configuration, you’re looking at a really nasty handling problem.

I think one of the things we’re going to see in the coming years are some really resourceful designs for battery housings. Things like fast-switch packs, like what Zero is running, ultra-low battery mounts, integrated battery/frame designs- it’s of critical importance, and there’s a whole lot of room for improvement.

Oh, by the way- if you talk to any builder and they say they’ve never used zip-ties, duct tape and bungee cords to hold batteries in for the “test run”, as shown above from Jake Saunders’ creation… they’re lying. And duct-taping batteries? …an art all of it’s own.

12 September 2010, 0726
Part Two: Essentials

Elegant design notwithstanding, there are some fundamental realities of mounting batteries you have to be aware of.

First, batteries are heavy. And dangerous. Whatever you do, you have to make sure that the batteries are supported adequately. They’re corrosive. They, in the case of lithium, will catch fire under certain circumstances, one of which being if the lithium is exposed to water. Besides that, there’s the obvious- you have them wired together to produce high voltage and high current. This is all fine for normal running, but you also have to consider a design that will be as safe as possible in a collision or accident. What may be fine in a normal upright position may kill you, or an EMT, in the event of an impact.

Individual battery design will dictate how the mount is designed.

Specific considerations:

Flooded lead acid batteries (in my humble opinion, although a very cheap option, also an incredibly dangerous one) MUST be run in the upright position only. They, of all designs, should be enclosed in some sort of spashproof box, and the design of the boxes should be totally overkill- anticipating the worst accident considerations.

Sealed AGM batteries can be run in almost every position except upside down. See the manufacturer’s specs, but they give you a lot more flexibility in designing an enclosure. They won’t splash or spill, even if the case is cracked open in an impact.

Most lithium batteries, like Thundersky or CALB, can also be run in almost any position except upside down, but they want to be bound pretty tightly. They expand and contract, and the cases aren’t really designed to withstand that stress without support. Many resellers will configure packs for you, with your configuration specs, and strap them accordingly for your safety. This is all good, but you have to know what you’re doing, and what will work in your configuration.

Many lithium batteries are running their outside shell as a positive, or, at least, very close to the positive- as in the Headways. It’s a really bad idea to use a conductive material for holding these things together- a little abrasion and you’re direct to positive of the pack. Keep in mind- carbon fiber, however strong and light, is made of carbon- one of the best conductors on the planet.

I’ve tossed around a few ideas for modular rack systems for mounting the cylindrical Headways- I figure a high strength plastic like Delrin might be the best material to cut them out of- here’s what they look like.

My best advice, though, is to get the batteries in hand before you commit to a mounting system. It’s one thing to toss around theory and design something- it’s quite another to be holding over 100lbs of batteries in your hands, and imagining what would happen in a 50mph crash. In the motor mount chapter I suggest designing only for the minimum stresses. In this case, I don’t think you can overkill the design enough.

Keep all this in mind in your fabrication, too. If you’re not trained in this stuff, don’t have a feel for it, new to welding, or considering a light-weight frame or box structure held together with bolts, or looking at an exotic or untested material, you’d be wise to look to some experienced help- either a motorcycle frame guy or a good builder- and listen carefully to their advice.


12 September 2010, 1346
Nuts? who is nuts?

I am errrrrrr ,I think I am errrrrrrrrrr The drugs ar not taking effffefffefct ....


BTW, great info!

Nutty Ed

12 September 2010, 1702

Guess I'm just

Farmer Bruce:eek:

Tony Coiro
12 September 2010, 1713
I'm tellin' you Bruce, you're gonna need more batteries than that....... :D

12 September 2010, 1715
I'm tellin' you Bruce, you're gonna need more batteries than that....... :D

ROFL!!! Yea, 10 Ah is not going to cut it!!!!

Funny stuff!!!

12 September 2010, 1733
But it's a 100Ah battery!?!??!!!

(Not to worry, it has 23 brothers......)

12 September 2010, 1740

Great! I was worried!!!

12 September 2010, 1813
Here is my most recent pic. Just finished drilling the holes in the aluminum for the compression bolts and reassembled the rack. 1 24inch length supported at one end can support 120lbs. The rack is supported at 8 points. I would say it is indeed more than needed. Once I am happy with it I will most likely get it welded in almost all locations. I hope to get flat stock cut this week and then assemble the pack and mount the motor.


13 September 2010, 1442
Guess I'm just

Farmer Bruce:eek:

Well you're certainly out-standing in your field... :D

13 September 2010, 1554

Sound like one of my jokes!!!! LOL

CrAzY Ed

13 September 2010, 1622
"Out-standing in your field"..................... oh dear, punny. :D

SWR1 (The Mistress) in its early stages, I miss the CVT..... :::sigh:::


I love CAD (Cardboard Aided Design)

13 September 2010, 1647
I know these battery trays are severely under utilized.
I can always add more batteries, as funding allows.

13 September 2010, 1714
I know... really, the truth is, every time I'd go to pick up a piece of angle iron I'd be thinking to myself, so what exactly is so wrong with this again? ;)

What can I say, he was a cranky old git. Think I have to add a little bit of a disclaimer...

17 September 2010, 0631
Flooded lead acid batteries (in my humble opinion, although a very cheap option, also an incredibly dangerous one) MUST be run in the upright position only. They, of all designs, should be enclosed in some sort of spashproof box, and the design of the boxes should be totally overkill- anticipating the worst accident considerations.

I've seen this stated by others before, but every ICE bike I've had came with flooded lead acid batteries, and they are common in 4 wheeled vehicles and boats too. Yes, there are real safety concerns, but they don't seem that incredibly dangerous to me. I've never seen one fully enclosed in a motorcycle. I've received numerous battery acid burns over the years, none of which was nearly as serious as a burn from a soldering iron, or what would happen to flesh in contact with a 72 volt arc.

17 September 2010, 0652
True, true... I'll play devil's advocate and say that I've also seen the corrosion around the battery box on literally every bike I've ever worked on that had a flooded battery. Not a safety issue, really, but there definitely is leakage, and you've got to consider the 200lbs+ that some people are running. I know it's certainly a subject of debate, and I think you'd be hard-pressed to find examples of some catastrophic incident involving flooded batteries.

Still, I'm sticking to my guns... I think it's a completely unnecessary risk, especially when discussed in a how-to context. But that also begs the point- I should really talk about the risks of lithium a little more, you think?