Battery placement for optimal bike handling?

[EdwardNY]

I want to add more batteries and I am trying to decide where to place them for optimal bike handling.

Right now I can fit 12 6s packs in the center of my frame. I can probably squeeze 14 of them inside the frame bag.

I would like to have about 24 battery packs in total.

Since I can not fit 24 of them inside the bike frame I may have to put some in the rear and or front of my bike.

I was wondering how to get optimal handling when having to place batteries in the front or rear of the bike. I remember reading something were someone said to place some in the front to even out the weight distribution. Is splitting the batteries between the front and rear important for handling?

If I could fit like 18 packs in the center of my bike, would I even notice the weight of placing 6 packs in the rear of the bike?

Is it important to place them all inside the frame triangle or just in the center of the bike? I may be able to attach 4 batteries just above and below the frame bag, on the sides of the frame.

When placing batteries in the center, below and above the triangle. Does it matter if you place them on the lower or upper bar? Does it make a difference keeping the batteries low vs high on the a bike?

Any tips, advice etc about battery placement and bike handling will be appreciated.

 

[ian.mich]

2.66kWh, now we're talking! i too have pondered the doubling of my 1.33kWh, but i need a 54xx to do that kind of weight
I think if you had 18 in the middle and 6 on the back it would be quite alright. 12/12 would be too much. the only real way i see that putting battery on the rear rack or handlebars would be practical is to put 18 in the middle, 6 on the front/rear, but i think you said th max you can fit is 12 in the frame. Also, what frame bag are you using?

 

[MadRhino]

I want to add more batteries and I am trying to decide where to place them for optimal bike handling....
I would like to have about 24 battery packs in total.

To fit 24 bricks of Lipo on a normal size bike, there is no question about where, they will have to be everywhere.
Handling ? That is a joke.
You need to build a trike or a motorcycle frame to handle good with such battery weight.

 

[spinningmagnets]

Keep the majority of the weight as central and low as possible. If you have a hub-motor on the rear, a handful of packs in the front might balance the bike bit if you run out of room in (and under) the triangle.

"Show us your home made battery housing"
http://endless-sphere.com/forums/viewtopic.php?f=3&t=12847

Square PVC below and above the down-tube, plus a frame-mounted front Pelican case:

 

[e-beach]

As many as possible inside the triangle of your frame. the rest should be as low as possible, so low hanging paniers off the back rack would work. You don't want a high center of gravity with an ebike.

 

[dogman dan]

Yeah, to pack that much, you will have them everywhere.

I don't think you expect it to handle light, but I get it you don't want it to suck more than it has to. Your frame will have to be very good, if you plan on loading it up. You need good lateral stiffness. Don't expect to be super comfy, but you can carry a lot of weight and go 25 mph no problems.

Fit what you can in the center of course, including the possibility of some under the frame. Then split the rest in half. Half in the rear, half in front.

Or, are you going to have panniers? if so just carrying all the rest low enough could be ok.

Or, get a bob trailer.

Lastly, longtail baby. This one handles 30 mph loaded up just fine. The longer wheelbase really helps the handling when loaded. It tolerates the high weight better than a short bike for sure. But I definitely carry some battery in the center first.

 

[EdwardNY]

I was able to fit 14 6s 5000 MAH packs in the Falcon EV bag. This was a pretty hard to do because my triangle is not large and the falcon EV bag is crushed into the center and has to fit around the rear shock. I spent a lot of time trying to cram 15 in the bag, but when I had to use connectors was only able to get 14.

I think 15 6s packs should suffice for a while. With 18s5p, I get about 20 miles of hard driving, I am talking grass, dirt, hills, almost no pedaling, and high speed driving and after that I am pretty drained anyway and happy I am in one piece and not arrested.

Since the falcon EV bag is wide at the bottom and overhanging the frame on both sides by about the width of a pack I am thinking about modifying it by sewing some extra compartments at the bottom to hold 4 more 6s packs, two on each side of the rear frame bar.

I think my bike frame is pretty strong, I notice no flex or anything like that. So far it handles 40MPH very smoothly and I honestly think it can actually do 50MPH smoothly. This bike is a German brand and is built very well, I think Germany makes very good bikes as biking is much more popular over there.

I remember some guy at a bike store saying my bike was heavy, maybe its built a bit beefier than most other cross country bikes. Could also be that I'm very skinny and do not weigh much, not sure how my weight influences frame vs battery weight attached to the frame. I'm probably 50lbs lighter than the average male biker if my weight has any influence on the frame.

 

[dogman dan]

I didn't go hunt down what you are riding.

Sounds like you have it figured out. If you do need to carry a lot more, put half on a handlebar bag or box, then the rest on the rear. Or low in panniers if you have that.

 

[neptronix]

Stick it in the triangle.
A rear rack battery is literally the worst place to put a battery. Coincidentally a lot of prebuilt ebikes come designed that way.

 

[Chalo]

As many as possible inside the triangle of your frame. the rest should be as low as possible, so low hanging paniers off the back rack would work. You don't want a high center of gravity with an ebike.

For handling while at speed, yes you do want the weight high. You want it close to the center of mass of the system as a whole, which in this case means close to the rider. Look at racing motorcycles-- they place the motor up high and then wrap the rider around it, reducing the percentage of system mass that is out at the extremities. The point is to reduce moment of inertia in the roll axis.

In the past, I rode tall Japanese four-bangers that were rather top-heavy. When one day I got to try my buddy's BMW R75/6 boxer twin with its weight placed very low, I was astounded at how much more of a production it was to swing the thing through a turn. The bike was much lighter than my bikes, but it steered like it was much heavier.

For handling the bike as an object-- like getting on and off, parking, and taxiing it around-- lower center of mass is better. Lower CoM also makes it sit more securely on a kickstand or centerstand. For the relatively limited performance envelope of an e-bike, these practical concerns may actually outweigh the importance of its handling qualities at the limits of speed, traction, and lean angle. That's why I put my wife's heavy battery pack as low on the sides of the rear rack as I could manage.

If the battery must be placed somewhere on the rear rack, then lower is better. But strictly from a high performance handling standpoint, the best place would probably be on the top tube.

Another tangentially related point is that when rack-mounting a battery, the rack matters. If it's laterally or torsionally flexible, it will harm handling when loaded much more than if it is stiff. Rack flex is the main thing that makes an e-bike feel "wiggly" or shaky. Racks with lateral triangulation (stays that go straight up and down in combination with stays that slope inward towards the center of the bike) are hugely stiffer than racks that are purely rectangular when viewed from the end. Mounting the front struts as solidly and as far apart as possible also helps.

 

[knighty]

20s1p headway 10ah cells mounted up front, fixed to the frame not the forks

handles great - I was worried about putting them up there, but it's hardly noticeable

I do 40mph everywhere, and I've hit speed bumps/pot holes at that speed without anything terrible happening (apart from filling my pants that is)

goes great in a straight line and I can corner quick/easy


I'm still getting the hang of going around corners fast tbh, I tend to slow down because there's cars around I need to watch out for, so when I have a chance to go faster I take it easy because I'm still surprised how far I can/have to lean over