Mounting your battery, Center of Gravity.

Mounting your battery.

With my new Ebike build in progress, I am faced with where exactly to mount my battery.

My first idea was to get my battery made in two packs. One pack on each side of my rack, placed down a little lower to lower my weight distribution. Of course, I talked to Ping, and he said he could make a battery in two packs, but it would take some time, and mounting the single big battery is easier. This is true.

So, reality has me thinking. Mounting the battery as one pack, on top in the center will be much easier to do, and keeps it close to the controller. Also, it allows me to move it forward a little, to keep all the weight in front of the rear hub.

So, I am thinking I'll mount it on top of the rack instead.

However, with the 25lbs up there, including controller, etc, how much of a differance would I feel while handling and riding the bike with this much weight mounted up so high? Of course I will be going with a rear hub, which is 25lbs down low, but not sure what this will do to the overall stability of the bike.

Has anyone had a hard time with this?

That would include just about everyone on this forum ! welcome to the clan.

Mounting big bulky packs to a bicycle rear rack, hmm.. it absolutely changes the handling of the bike, but you change the way you ride it to compensate. ie: If you stand up off the seat and try to crank hard on the pedals you have to keep the frame steady, if you wobble left to right the whole pack high up shifts and makes the ride interesting to say the least.

25lbs, not that bad tho.. i have 48v 12ah of SLA for a while at 40 lbs and that was nuts.

Look at bike racks with saddle bags( side bags ) even with the battery on one side hanging low, once you ballance the other side with a bike " kit " like chargers, tools, volt meter, beer, rain suit, beer, etc etc etc.. and you have the top of the rack for more storage.

Mounting in the triangle frame is another option if the pack is narrow enough.

Backpack batteries are ok on a BMX for short range rips, but no good for a long range ..

what size pack ? ah V ?

I'm looking at getting one of PIng's 48v/20ah lifepo4 packs. total weight about 20lbs, plus the controller, and I may even mount the charger inside as well. Probably closer to 30lbs for everything. That way I can recharge at work. I'll need it for my 23mi commute with a 5303 rear hub motor.

My objective is to try and maintain a semi-ridable bike, even if the battery goes dead on the trip home, so I won't have an out of control top heavy behemoth to climb hills with. However, I'm build the steel FB roadie with a triple using a 32-28t low gear for steep hills.

With an X5 on your bike, lets face it.. if that battery quits.. you are screwed !


Well worth the wait if you can get 2 packs instead of one, and 2 chargers.

Placing a battery, and controler on the rear rack with a rear mount motor, will give you an ungainly tank of a bike, and that's the polite version. All that weight will also increase the chance for flats & spoke breakage to boot.

I strapped my battery low behind the seat with nylon straps you get for roof mounted car carriers with buckles. I sewed them on the frame at one end and buckle the other, much like a ribbon on a present, 90 deg to each other, amazingly secure, but my bike is probly different than yours.

I had a similar quandary. I wanted to go big with the batteries. I opted for a chopper style bike frame that afforded loads of room of low center of gravity battery mounting, plus a long wheelbase for stability and comfort. And it looks cool 8). I have 72V 20AH mounted with room to spare, and I am using the X5 motor, too.

As a cheap temporary solution it works fine. I've had 25lbs of batts strapped on a spindly wiggly standard bike rack for over a month, and in terms of handling, leaning into a curve with the knobby tires that I've yet to swap out is a far greater concern. It gets me on the road while I figure out a good long-term solution that takes aerodynamics, center of gravity, and protection of expensive batteries all into account. Of course being on the road means construction of something better has slowed to a crawl.

Something I believe you have to consider is how you plan to use your bike. eg My commute is about 20ft, so my bike doesn't come into play. I use it for errands and joy riding. The problem with errands is where to put the stuff you go pick up, and how to safely take the kids for a ride too. The roads here are lacking, so any kind of 3 wheeler as a load carrier is out of the question. It's hard enough finding a good line with one wheel trailing the other. A detachable trailer might work, but after a lot of looking around I've decided to go with the "extracycle/world bike" approach and extend my wheelbase 15". This relatively simple procedure will free up plenty of space within the frame for batteries and electronics. Plus I can get rid of that hideously uncomfortable "saddle" for a comfortable "chair" like Justin has for his transcontinental ride across Canada, and still leaves room with a strong rack for one of the kids and a bunch of bags of groceries at the same time, or a surfboard, kayak, whatever. I really like the concept of a sport utility bike, which will go a lot further toward eliminating my car than just a bike with a motor. It does mean that I need a second bike though for installing a multi KW RC motor or 2 like Recumbent is doing, but that will have be a 2nd bike, somewhere between a downhill bike and a motorcycle anyway, not a load carrying comfort cruiser. Oh well, back to 3 vehicles again, but a van and 2 ebikes seems a whole lot better than 2 gas guzzlers and a motorcycle.

John

recumbent said:

Placing a battery, and controler on the rear rack with a rear mount motor, will give you an ungainly tank of a bike, and that's the polite version. All that weight will also increase the chance for flats & spoke breakage to boot.

I strapped my battery low behind the seat with nylon straps you get for roof mounted car carriers with buckles. I sewed them on the frame at one end and buckle the other, much like a ribbon on a present, 90 deg to each other, amazingly secure, but my bike is probly different than yours.

Click to expand...

A tank of a bike yes, especially since I'm used to my 15lbs weight-weenie roadie. The beast will undoubtedly weigh upwards of 85lbs when complete. But I don't think I'll be that much more prone for flats than other normal bikers. I plan on using more rugged tires, like Schwalbe Marathons. Also, I figure the motor and battery adds about 50-60lbs total weight.

I only weigh 175lbs. So, collectively it would be no worse than a 225lbs rider on a regular touring bike. Just gotta watch out for potholes.

What I'm most concern with, is how it will feel with the batteries mounted up high on the rack behind the saddle, instead of low in the panniers. I guess I shouldn't complain, since I see most of the MTB conversions with the battery on the back as well.

Using a front hub myself, i find the 15 pound Ping I carry on a seatpost rack is hardly noticeable. but 33 pounds of sla's sure was! If you have no other choices though, I daresay you will get used to the ride. My 80 lbs of ebike feels light to me now since the power is there, but I still like my 27 lb vintage motobecane for shorter rides.

having a battery on a rear rack is noticable. the heavier, the more so. you'll feel the bike being top heavy.

but if you ride with anything on a rear rack, you'll experiance the same problem. Its something you have to get used to, but not that big of a deal.

The lower the better. Putting one heavy battery in a panier is better then putting it on the rack, even if it is unbalanced.

Just carry the battery on one side, and a six pack on the other. Sooner or later everybody breaks down. Drink the beer while you wait for your ride home.

dogman said:

Just carry the battery on one side, and a six pack on the other. Sooner or later everybody breaks down. Drink the beer while you wait for your ride home.

Click to expand...

Warm beer? A nice box of red wine would be OK at room temperature. And it might match your battery better.

Ypedal said:

With an X5 on your bike, lets face it.. if that battery quits.. you are screwed !
Well worth the wait if you can get 2 packs instead of one, and 2 chargers.

Click to expand...

Couldn't agree more on this. Rather than a single 20AH pack, IMO it's is much better to go with two, 10AH packs running in parallel (via schotky diode).

A - If one fails, you will have another to get you home.

B - Splitting the load across two packs, cuts the amps pulled from each in half, extending their lifespan.

C - It is much easier to distribute the weight two smaller packs on your bike than one larger one.

D - Using two chargers on two separate packs will cut recharge time in half.

..

Few years ago, Heinzmann ebikes seperated thier battery boxes, one per side of rear carrier, just above the axle. That way you can still use your trunk for groceries and stuff.

This is my thought process.




1. If I went with two packs, one on each side, I would then use an Otivia trunk for the controller and charger. I could mount all of the electronics in the front part of the Otivia, seperated by a wall, and use the rear of the trunk for my lunch. If I did it this way, I would not want to use big panniers on the sides for the batteries. I would probably use some waterproof plastic containers, hard mounted to the rack, with wiring conduit going into the Otivia for the controllers. I wouldn't use large panniers for the batteries, because I wouldn't want to haul other stuff in the same bag as the batteries.

Doing it like this will leave me with very little storage space for anything other than my lunch for work. Which is fine, but not good if I ever want to use my bike for in town errands, and shopping.

2. The other alternative, is to mount the battery and controllers in the Otivia, all in one. This is the easiest way to set it up. Everything would be weatherproof in the cargo trunk, easier to work on, and neatly packed together.

The benefit of this, would allow me to use large panniers on the sides, which would allow my lunch , clothing, and avything else I want to haul, including groceries for errands, etc. This seems like a good idea, but as this thread indicates, I'm worried about the weight distribution with the battery, controller, and charger all mounted on the top of the rack in the Otivia trunk.

This is a big debate for me, but I thank everyone for their insight.

Keep it coming!!!

Patriot said:

Mounting your battery.

With my new Ebike build in progress, I am faced with where exactly to mount my battery.

My first idea was to get my battery made in two packs. One pack on each side of my rack, placed down a little lower to lower my weight distribution. Of course, I talked to Ping, and he said he could make a battery in two packs, but it would take some time, and mounting the single big battery is easier. This is true.

So, reality has me thinking. Mounting the battery as one pack, on top in the center will be much easier to do, and keeps it close to the controller. Also, it allows me to move it forward a little, to keep all the weight in front of the rear hub.

So, I am thinking I'll mount it on top of the rack instead.

However, with the 25lbs up there, including controller, etc, how much of a differance would I feel while handling and riding the bike with this much weight mounted up so high? Of course I will be going with a rear hub, which is 25lbs down low, but not sure what this will do to the overall stability of the bike.

Has anyone had a hard time with this?

Click to expand...

welcome here Patriot!!


That 's exactly what i wanted to ameliorate on my present ebike when i built it!

I choosed a bike that allow me to place the batterie close to the oppositte wheel of the hub motor and under the frame.. so with a rear X5 motor, i placed the battery (40lbs of lithium!) rear to the front wheel

see:

The control and handling of the bike is just perfect!!

Doc

The above picture is of my bike with the e-bikes.ca triangle NiCd pack and frame bag. The high forward mounting has little effect on my bikes handling. (the 15lb of extra weight in the front wheel has a MUCH worse effect)

Marty

P.S. that picture is from http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=3742

My ride:

Polycarbonate, stainless steel, 2 x heavy duty racks, filled the seat post tube with oak and JB weld, don't even ask how long this took.

Triangle mount is working great for me so far. I want to go full suspension at some point, but would have to build something new to accommodate that idea.

dirtdad said:

dogman said:

Just carry the battery on one side, and a six pack on the other. Sooner or later everybody breaks down. Drink the beer while you wait for your ride home.

Click to expand...

Warm beer? A nice box of red wine would be OK at room temperature. And it might match your battery better.

Click to expand...

Reminds me of an old joke:

Q: Why do the British drink warm beer?



















A: Lucas makes refrigerators.

Cute! Is "the Prince of Darkness" still in business?
otherDoc

72V 20AH (approx 1.5KWH), you cant get a much lower center or gravity

Having a low center of gravity for lots of batteries is the primary reason I opted for a chopper bicycle frame. Not only are the batteries low, but the rider is, too. And putting your foot down when you stop is obviously no problem.

The handling makes it a lot of fun to ride hard. You can lean into sweepers, counter lean and lean forward for tight stuff, keep it upright in sand or rain for stability, etc. It handles like nice motorcycle, minus the suspension.

Nothing carries the batteries as good as the choppers or stretch beach cruisers. Someday i'd like to make one with old school rear suspension, like two shocks, and a downhill mtb fork, and run about 72v or so of rear hub on it. Pretty much ride it in the recumbent position.

The six of beer will still be light on one side, but not if you carry it in an ice chest! Or a 12 pack if it's cool weather. Some of the spots I've run out of battery, warm beer wouldve been fine though. If its not too late allready, I'd get the battery made to split in half and carry it in panniers or saddlebags. 15 pounds on my rear rack is no sweat, but any more would get a bit funky i think. I am allways amazed at what I can carry in my messenger bag. I like it much better than a backpack. It doesn't make me sweaty here in the desert.

That red chopper's missing something.

technically, I think it needs to be a licensed vehicle now. It has no chain or gears. That's really pushing the limit.