Battery Location. Your Opinion Matters!

General Discussion about electric bicycles.
rlewis   100 µW

100 µW
Posts: 7
Joined: Dec 21 2018 10:26am

Battery Location. Your Opinion Matters!

Post by rlewis » Apr 15 2019 1:10pm

Traditional downtube mount or seatpost tube mount?
Attachments
20190415_135952-1280x960.jpg
20190413_134530-1280x960.jpg
20190415_140040-1280x960.jpg
Last edited by rlewis on Apr 15 2019 1:41pm, edited 1 time in total.

User avatar
cal3thousand   1.21 GW

1.21 GW
Posts: 3583
Joined: Mar 26 2012 4:47pm
Location: California

Re: Battery Location. Your Opinion Matters!

Post by cal3thousand » Apr 15 2019 1:40pm

You're already in the right place for the battery, between the tires. I think the flat one may be marginally better due to slightly lower CoG.

Personally, I would go with the one that was the most convenient for ingress/egress
Get a Cycle Analyst and a Multimeter, you're still a noob if you don't have at least one of each.

Planning on posting questions or buying anything on this site? Put up your country (at minimum) on your profile. This is a worldwide forum and we haven't reached clairvoyance.

qwerkus   100 W

100 W
Posts: 232
Joined: Jul 22 2017 4:00am

Re: Battery Location. Your Opinion Matters!

Post by qwerkus » Apr 15 2019 2:26pm

cal3thousand wrote:
Apr 15 2019 1:40pm
You're already in the right place for the battery, between the tires. I think the flat one may be marginally better due to slightly lower CoG.

Personally, I would go with the one that was the most convenient for ingress/egress
+1 Lower center of gravity improves the handling a lot. Now correct me if I'm wrong, but in this frame, you can fit 2x battery case of this size (if you need so much power). In that case, I'd mount the lower one first (albight a bit higher on the downtube) and than the second one. And on a sidenote, I'd go for a suspended fork. Aluminium + no fork suspension + small tyres = bumpy ride, even with that seat tube suspension.

rlewis   100 µW

100 µW
Posts: 7
Joined: Dec 21 2018 10:26am

Re: Battery Location. Your Opinion Matters!

Post by rlewis » Apr 15 2019 5:27pm

Thank you for your responses so far! I get the low center of gravity as a concept, but personally have no practical experience. So I appreciate your insite.

As an engineer, instinctively, I think vertical mount will provide a lower COG. Being that the weight y axis "lands" near the crankset.
Last edited by rlewis on Apr 16 2019 5:42pm, edited 1 time in total.

rlewis   100 µW

100 µW
Posts: 7
Joined: Dec 21 2018 10:26am

Re: Battery Location. Your Opinion Matters!

Post by rlewis » Apr 15 2019 5:38pm

Thank you for your responses so far! I get the low center of gravity as a concept, but personally have no practical experience. So I appreciate your insite.

As an engineer, instinctively, I think vertical mount will provide a marginally less COG. Being that the weight impact "lands" near the crank set.

From an ascetics perspective thoughts are welcome too.

User avatar
Chalo   100 GW

100 GW
Posts: 7701
Joined: Apr 29 2009 11:29pm
Location: Austin, Texas

Re: Battery Location. Your Opinion Matters!

Post by Chalo » Apr 15 2019 5:55pm

Center of mass matters relative to the ground when at crawling speeds, and relative to the roll axis when underway. Fast motorcycles intentionally locate their mass high up and close to the F/R center of the bike. They change direction more easily that way.

For a cargo bike or a pedal bike, low weight distribution works best. Whether higher or lower works for you depends on your speed and riding style.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

docw009   10 kW

10 kW
Posts: 945
Joined: Aug 02 2015 7:43am
Location: Chicago area suburbs.

Re: Battery Location. Your Opinion Matters!

Post by docw009 » Apr 15 2019 6:43pm

I like the downtube mount because more of the battery's weight rests against the cradle as opposed to the almost vertical position where I would surmise either the locking pin or the base of the cradle bears most of the weight.

I will admit not being familiar with the cradle for that particular battery so all of the above could be flawed.

markz   100 GW

100 GW
Posts: 6826
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Battery Location. Your Opinion Matters!

Post by markz » Apr 15 2019 8:49pm

Your bike looks like the one I past today, I was clocking in pretty fast to show him how fast DIY'ers go, his motor did not even protrude past the largest freewheel gear. I twisted the throttle just that bit extra when I realized the bike was juiced. My seat tube broke on the crappy Norco, its junked, I had to ride low-rider style. I prefer a battery mount of black gorilla duct tape, plastic zip ties and metal zip ties. Anything that looks too good, like your e-ride, grabs un-wanted attention, but it also acts as a camo flaged as well, I like how its all black on black, very well done! Have you scratched your that ride yet, its that first scratch that gets to you, just give it up, use duct tape! :wink:

User avatar
RustyKipper   100 W

100 W
Posts: 107
Joined: Apr 13 2015 5:40am
Location: South Yorkshire UK the land of flat caps and wippets

Re: Battery Location. Your Opinion Matters!

Post by RustyKipper » Apr 16 2019 5:58am

Personally I would mount the battery as far forward as possible as you already have a fair bit of weight in the rear wheel, it won't make a huge difference on smooth roads but if you have to man handle the bike for storage or charging as I do then the less total weight of the rear makes a big difference. Also with too much weight at the back the ride will be very harsh on poor road surfaces. The only downside is that you will loose the water bottle mounts on the down tube if you need to carry any drink.
2017 Cotic BFE hardtail MTB
Sram 9 speed twist grip
CST rear drive
5P10S 16Ah home built battery with built in block heater
Con121 12FET controller
Sapim 2.3mm black stainless steel spokes
Sunringle 26 inch rims
26 x 2.1 Swarble Marathon Mondail tires
650gm downhill inner tubes --essensial
Shimano Zee 4 pot calipers front and rear
200mm / 203mm rotors
Thudbuster suspension seat post -- essensial
150 Mile per week muddy commute

User avatar
cal3thousand   1.21 GW

1.21 GW
Posts: 3583
Joined: Mar 26 2012 4:47pm
Location: California

Re: Battery Location. Your Opinion Matters!

Post by cal3thousand » Apr 16 2019 10:15am

I like the last point of offsetting your rearward bias with some additional forward weight. Mount it on the downtube.
Get a Cycle Analyst and a Multimeter, you're still a noob if you don't have at least one of each.

Planning on posting questions or buying anything on this site? Put up your country (at minimum) on your profile. This is a worldwide forum and we haven't reached clairvoyance.

User avatar
wturber   1 MW

1 MW
Posts: 1522
Joined: Aug 23 2017 8:52pm
Location: Fountain Hills,AZ
Contact:

Re: Battery Location. Your Opinion Matters!

Post by wturber » Apr 16 2019 1:28pm

Were it me, I'd choose a mount location based almost entirely on where I want to mount my water bottles.

I have my substantial batteries mounted in almost the worst possible location based on the various handling theories. I have about 10 lbs of batteries mounted on each side of my rear rack (20 lbs total). The only thing that would make this position worse would be to mount them higher. But I put my 10=15 lb backpack up higher in my milk crate on top of my rack. And oh - I also have my rather heavy Meanwell charger, locks, and motor controller in the same general area. So how does my bike handle? I dunno - seems fine to me. I routinely cruise at 20-28 mph and go down steep hills at nearly 40 mph. I don't have stability or handling issues with my moderately powered (750-1000 watts) rear direct drive bike. The biggest issue I have is that the back end of my bike is very heavy and hard to lift given the heavy motor and batteries and other stuff.

To be clear, I'm not suggesting that you duplicate what I've done. My setup is hardly optimal. My point is that if my clearly non-optimal setup is workable, then the choice of down tube or seat tube for a lighter battery should probably be made for reasons other than handling - unless you are super persnickety about how your bike handles. And if that's the case, then try it both ways and pick the one that has the subtle benefits you want.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

miro13car   1 MW

1 MW
Posts: 1574
Joined: Mar 26 2007 1:30pm
Location: Calgary, Canada

Re: Battery Location. Your Opinion Matters!

Post by miro13car » Apr 16 2019 4:05pm

The lower it is the better.
The worst place is on the luggage rack of course but it is popular location of course because it is most lazy way
Eplus, Bionx

User avatar
MadRhino   100 GW

100 GW
Posts: 5645
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Battery Location. Your Opinion Matters!

Post by MadRhino » Apr 16 2019 7:11pm

Ideal battery placement for a rear hub build has to be according to 3 factors: the weight of the battery, the weight of the hub, the speed that you ride.

You want to place the balance of the bike about the middle of its length. So, a heavy hub might force you to fit a very lightweight battery on the front, for an extreme example. Most are using a battery heavy enough that its best mount is inside the frame triangle. The down tube mount is common on factory built ebikes, for it is practical and good looking, considering the moderate speed and smallish battery of ´legal’ bikes.

The faster that you ride, the higher on the front you will like the battery weight, like the big gas tank of racing motorcycles. On the opposite, the slower and the most technical the ride, the lower center you will like the weight.
Make it fool-proof, and I will make a better fool.
Current bikes
Street: https://s20.postimg.org/ewrvugywt/Session_04_2015.jpg
Dirt: https://s20.postimg.org/lbqwr55ml/IMG_0157.jpg

User avatar
wturber   1 MW

1 MW
Posts: 1522
Joined: Aug 23 2017 8:52pm
Location: Fountain Hills,AZ
Contact:

Re: Battery Location. Your Opinion Matters!

Post by wturber » Apr 16 2019 7:13pm

miro13car wrote:
Apr 16 2019 4:05pm
The lower it is the better.
The worst place is on the luggage rack of course but it is popular location of course because it is most lazy way
Most lazy way? Hardly. Standard bottle/shark battery mounted to seat or down tube is about as simple/lazy as it gets.
Also, batteries disguised as luggage can have advantages if you are trying not to attract attention.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

rlewis   100 µW

100 µW
Posts: 7
Joined: Dec 21 2018 10:26am

Re: Battery Location. Your Opinion Matters!

Post by rlewis » Apr 16 2019 7:32pm

Thanks again for the feedback. I keep changing my mind... You guys are bringing up great points. Plan to drill and install a rivnut to anchor the battery good. First hole/scratch needs to be thought out. The battery is heavy for what it is. 52v 17.5ah 40a bms. Not a lighter weight version. So I want 3 fasteners holding the base.
I'm gravitating to the downtube and placing higher to accommodate a vertical water bottle. If I keep it low like the the first picture, I'll have no place for a water bottle at all.

User avatar
RustyKipper   100 W

100 W
Posts: 107
Joined: Apr 13 2015 5:40am
Location: South Yorkshire UK the land of flat caps and wippets

Re: Battery Location. Your Opinion Matters!

Post by RustyKipper » Apr 17 2019 4:08am

I've mostly mounted my water bottle on top of the down tube mounted battery either directly or by a bracket from the seat tube bottle bracket holes. Mounting the controller tidily is usually the biggest challenge.
bottle 2 small jpg.jpg
bottle 2 small jpg.jpg (225.77 KiB) Viewed 216 times
bottle 1 small jpg.jpg
bottle 1 small jpg.jpg (168.01 KiB) Viewed 216 times
2017 Cotic BFE hardtail MTB
Sram 9 speed twist grip
CST rear drive
5P10S 16Ah home built battery with built in block heater
Con121 12FET controller
Sapim 2.3mm black stainless steel spokes
Sunringle 26 inch rims
26 x 2.1 Swarble Marathon Mondail tires
650gm downhill inner tubes --essensial
Shimano Zee 4 pot calipers front and rear
200mm / 203mm rotors
Thudbuster suspension seat post -- essensial
150 Mile per week muddy commute

miro13car   1 MW

1 MW
Posts: 1574
Joined: Mar 26 2007 1:30pm
Location: Calgary, Canada

Re: Battery Location. Your Opinion Matters!

Post by miro13car » Apr 17 2019 10:43am

In my book luggage rack is for luggage, not battery.
You cannot cheat law of physics. Center of gravity low means stability
Eplus, Bionx

User avatar
wturber   1 MW

1 MW
Posts: 1522
Joined: Aug 23 2017 8:52pm
Location: Fountain Hills,AZ
Contact:

Re: Battery Location. Your Opinion Matters!

Post by wturber » Apr 17 2019 2:41pm

miro13car wrote:
Apr 17 2019 10:43am
In my book luggage rack is for luggage, not battery.
You cannot cheat law of physics. Center of gravity low means stability
And this is why everyone gets to customize their bike to suit their own preferences. In my book, a rack is a place to carry or attach stuff.

As for the physics of handling, please understand that when people mention "good handling" they do not necessarily mean "stability." It is more complicated than that. Standard bicycles have an inherently high center of gravity due to the person riding them. Nonetheless, they are very stable devices.

Also consider that one reason to keep added weight between the wheels is so that the bike has a lower polar moment of inertia and hence quicker and more nimble handling. That doesn't necessarily make the bike more stable, but for many types of riding it is a benefit. Others have mentioned the pros and cons of higher and lower centers of gravity and other aspects of weight distribution and how these things impact different kinds of riding. You might want to review those comments.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

User avatar
spinningmagnets   100 GW

100 GW
Posts: 10920
Joined: Dec 21 2007 10:27pm
Location: Ft Riley, NE Kansas

Re: Battery Location. Your Opinion Matters!

Post by spinningmagnets » Apr 17 2019 3:15pm

If you have a lot of power, I prefer the downtube. Both are low, but downtube is more forward.

Also, as stated above, when you hit a big pothole or land a jump, downtube mount seems like it would take force from that direction a little better

markz   100 GW

100 GW
Posts: 6826
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Battery Location. Your Opinion Matters!

Post by markz » Apr 17 2019 5:54pm

I have a wild idea after looking at the pics, make your battery look like an enlarged water bottle, for ultimate camouflage!

I know there are regular water bottles that are batteries, but there is not enough Wh in them to be of any good!

Have it look like this
2L (64oz) https://www.amazon.ca/Under-Armour-Insu ... rts&sr=1-5

Better yet, a thermos!
https://www.amazon.ca/iBaste-Stainless- ... rts&sr=1-4

Lunch Special 3L
https://www.amazon.ca/gp/product/B01M7Q ... -50-gen-20

Kidding aside, all I'd do is get some sheet alum, somehow curve it round, and figure out how to stuff the maximum amount of 18650 in there, and place it on the downtube. Then make your own big THERMOS sticker for each side, making sure its readable!

RustyKipper wrote:
Apr 17 2019 4:08am
bottle 2 small jpg.jpg
bottle 1 small jpg.jpg

User avatar
RustyKipper   100 W

100 W
Posts: 107
Joined: Apr 13 2015 5:40am
Location: South Yorkshire UK the land of flat caps and wippets

Re: Battery Location. Your Opinion Matters!

Post by RustyKipper » Apr 18 2019 2:04am

This was an Idea I was working on a while back, the carbon tubes carried the battery cells either side of the down tube and the water bottle was to hold the controller. I was hoping for a very stealth like silhouette, it would have been quite wide however.
water bottle battery jpg.jpg
water bottle battery jpg.jpg (169.7 KiB) Viewed 136 times
2017 Cotic BFE hardtail MTB
Sram 9 speed twist grip
CST rear drive
5P10S 16Ah home built battery with built in block heater
Con121 12FET controller
Sapim 2.3mm black stainless steel spokes
Sunringle 26 inch rims
26 x 2.1 Swarble Marathon Mondail tires
650gm downhill inner tubes --essensial
Shimano Zee 4 pot calipers front and rear
200mm / 203mm rotors
Thudbuster suspension seat post -- essensial
150 Mile per week muddy commute

User avatar
dogman dan   100 GW

100 GW
Posts: 34706
Joined: May 17 2008 12:53pm
Location: Las Cruces New Mexico USA

Re: Battery Location. Your Opinion Matters!

Post by dogman dan » Apr 18 2019 8:57am

Well, I'm going to disagree a bit with everybody. Because of the small size of all the batteries you show in the pictures, mount them anywhere you want. Seat tube, down tube, under the top tube, handlebars, rear rack, in a backpack, whatever.

But of course, always better to mount 8 pounds in the mid frame, if your bike has a frame triangle. But my point is that up to about 10 pounds is pretty tolerable, requiring only for the rider to make a slight change in riding position even on highly technical, or steep off road riding. My current off road ride has a Y frame, making a frame mount difficult. I carry 8 pounds of lipo on a seatpost rack that does not wiggle, and I'm just fine. In a RACE, I would not be winning, but I can ride dirt as hard as I ever do no problems.

15 pounds back there, problem for dirt, not too bad for street commute. Big battery, you need mid mount. This is why I built this frame. I wanted to carry up to 40 pounds of battery in the frame, fore and aft, but concentrating the weight nearest the seat post as possible.
Finished cargo mixte..jpg
Finished cargo mixte..jpg (133.85 KiB) Viewed 120 times
If you are making a street ride, and must carry a heavy battery, then split in half, and carried in panniers as low as possible works ok. As for width of a frame battery, I really think anything over 5 inches wide is for bikes you do not pedal. One 18650 wide is plenty narrow enough to pedal easily around, so a big triangle battery in the frame is the best bet for a large battery, if of course, your frame is that kind.

User avatar
RustyKipper   100 W

100 W
Posts: 107
Joined: Apr 13 2015 5:40am
Location: South Yorkshire UK the land of flat caps and wippets

Re: Battery Location. Your Opinion Matters!

Post by RustyKipper » Apr 18 2019 9:22am

I once made the mistake of buying a set of Lifepo4 cells so I had to spread the weight around the frame in 3 battery boxes, 6 cells high up at the rear, 4 on the seat post and 2 under the down tube, unfortunately the ally frame would flex like it was made from rubber every time I hit a bump, with 18650 cells it would have been much better, even so the bms wiring was something special!
Attachments
battery boxes.jpg
2017 Cotic BFE hardtail MTB
Sram 9 speed twist grip
CST rear drive
5P10S 16Ah home built battery with built in block heater
Con121 12FET controller
Sapim 2.3mm black stainless steel spokes
Sunringle 26 inch rims
26 x 2.1 Swarble Marathon Mondail tires
650gm downhill inner tubes --essensial
Shimano Zee 4 pot calipers front and rear
200mm / 203mm rotors
Thudbuster suspension seat post -- essensial
150 Mile per week muddy commute

rlewis   100 µW

100 µW
Posts: 7
Joined: Dec 21 2018 10:26am

Re: Battery Location. Your Opinion Matters!

Post by rlewis » Apr 20 2019 2:10pm

This is where I'm leaning for battery, controller and water bottle. It's a good bit higher in the frame than I originally wanted, but is a compromise for water.
Attachments
20190420_150058-1280x720.jpg
20190420_150109-1280x720.jpg

E-HP   100 W

100 W
Posts: 252
Joined: Nov 01 2018 9:20pm

Re: Battery Location. Your Opinion Matters!

Post by E-HP » Apr 20 2019 4:06pm

rlewis wrote:
Apr 20 2019 2:10pm
This is where I'm leaning for battery, controller and water bottle. It's a good bit higher in the frame than I originally wanted, but is a compromise for water.
Good choice. If you keep the water bottle full, then it's a similar center of gravity as with the battery placed lower, but without a bottle.

Post Reply