Battery position

As a bike specifier the position of the battery has so many pros v cons that there appears no real answer as yet.

1) Behind the seat post....this has the advantage that the length and therefore the capacity of the battery can be increased up to even 20 Ah,it has the disadvantage that the wheelbase of the bike has to be extended,this makes the bike less handy and to my eyes gives the bike a dragster look,however the weight of the battery is near to the BB, which is good.

2) On the down tube....this is a good choice for weight balance and disguised as a water bottle it can look ok,it does not allow LifePo4 or bigger than 10Ah because the triangle is not normally large enough to take the bulk.

3) On the rear rack....allows bigger batteries,10Ah using LifePo4,16Ah using LiMn04,but it does make the bike tail heavy,the battery can be disguised using panniers.

4) Within the down tube or seat tube.....for appearance is probably best but the design of the batteries is often a one off so replacement batteries are normally expensive.

5) Pod style,hanging on the back of the seat post....cantilevered off the seat post,makes the mount bracket vulnerable to damage,max limit normally 9 Ah.

Is there an ideal choice or will every application be different?

Dave

Kudoscycles

Edited February 10, 201313 yr by Kudoscycles

IMO the best position on the bike for the battery is on the down tube like the water bottle type. I think this is best for the weight distribution and handling. If the shape of the water bottle is limiting max capacity then you could make bigger batteries that are not bottle shaped but mount in the main triangle of the frame perhaps a bit like d8veh's rocky mountain conversion

On a rack behind the seat could be a good solution, but all the manufacturers mount them too far back on hideous looking racks. The handling is hardly compromised if you can get the whole battery in front of the back axle and very low, which means wider and fatter batteries, and not a good possibility of fitting a normal rack.

 

Bottle batteries could be bigger if they unclipped sideways instead of upwards, but you need at least 10 extra cells (50 cells, so a squarer design with the cells standing on end would be necessary.

The real answer of course is for manufacturers to invest in the R&D to deliver smaller batteries with higher capacity (we've come a long way but not nearly far enough). Then the mounting options become far less of a problem as there's so much less weight and bulk to accommodate.

I would go for the behind the seat battery as I have on my Eagle for two reasons. A large capacity battery can be fitted and long range is key to the useability of my ebike. 10 a/hours is too marginal and would render most of my 'day trips' impossible. Secondly, I believe the 'silver fish' design is the most common and as such should facilitate ease of replacement at the most competitive price.

 

From a purely aesthetic point of view, I would plump for the bottle type in the frame triangle as D8Veh mentioned, but it would have to be a minimum of 15 a/h.

 

I don't like the battery on the rear rack, its just an appearance thing, but I feel it makes the bike look home made as though someone just strapped a battery on without any thought for integrating the battery into the design. Cost of the replacement battery is paramount. I would never buy a Bosch powered bike for this reason, regardless of how good they may be.

 

Perhaps the Xipi type might be workable, in the frame and 720 watt/hours. With a little styling to avoid the square box look, could be a go'er.

Edited February 10, 201313 yr by Eaglerider

Is there an ideal choice or will every application be different?

Dave

Kudoscycles

 

In my opinion, several solutions will be required. That is until battery technology moves ahead and gives us batteries a 1/4 of the current size.

 

It is always going to be preferable to keep the weight, low down and central. Particularly

on bikes required to have sharp, fast handling.

 

In, on or beneath the down tube achieves this.

Cost aside, my preference would be two smaller batteries on and or under the down tube.

 

A bike for nipping into town for a bit of shopping, may benefit from a rack and panniers.

Makes sense in this instance to fit the battery into the rack. Weight somewhat higher but I don't expect the use to be kerb jumping and or making fast turns.

 

Bikes for distance and touring, behind the seat post makes complete sense to me. Slightly longer wheelbase but nice and stable.

 

If I were going to design for example a low weight hybrid, I'd try the following:

 

Rear hub motor with bespoke controller fitted inside of the seat tube. The tube would act as the heatsink.

 

As for the batteries, I'd design them into a front hub. The shape of the cells lend themselves to this design. Obviously slip rings would be required for power take off.

 

The only downside of this is the wheel would need to be removed if you needed to charge off the bike.

 

About as stealth as you could get and allows for standard geometry bikes of all kinds to be used.

Hi we have spent many months looking at the Kube Battery It includes the controller inside we can now supply a 48 volt 20AH battery with a 50A BMS and a 18 mosfet 50 A controller I Know it looks Square but designed to fit into as many bikes as possible At 160 X 160mm X 135 wide for the 15AH 48 volt Kube Including a 12 mosfet 33A controller total weight 6 kilos

 

we looked at a vacume formed molding to fit in the triangle still on the drawing board

 

For the Baby Kit we have a prototype being made to fit on the down tube including controller and battery only 10ah

 

 

The Kube is fixed NOT removable for charging

 

Because it is Made in Banbury we can make in other colors

 

 

Frank

Edited February 10, 201313 yr by banbury frank

Mostly by accident, rather than by design, I have arrived at a practical set-up for my own purposes:

 

Bottle battery on the down-tube gives me 20 - 30 miles range & ezee flatpack bungee'd on the rack; or vertically in, against the "air back" frame of, my day pack if the trails are rattly; until needed for an extra 30+ miles. (I carry an extenion cable, but have never used the battery in the pack).

 

With the weight of the bottle battery in situ I honestly don't notice that of the flatpack - Balance & handling feel fine.

In addition the the eZee rear mounting FP (flat pack) and the VP (vertical pack) batteries we also have a 37v 11.6Ah LiPo BT (down tube mounting battery) as shown below, which can be fitted in addition to either the FP or VP batteries or supplied with an eZee conversion kit.

 

In theory, it would be possible to have 3 eZee batteries, 20Ah VP, 14Ah FP and 11.6Ah BT mounted on an eZee bike and wired in parallel giving a total of 45Ah.

 

The obvious downside is it would be heavy, but capable of a long range.

 

[ATTACH]5084.vB[/ATTACH]

I have my batteries in the panniers so the weight is further down compared to a standard rack mount. I do intend one day making cases and brackets for the sides of the rack. Maybe you makers can consider doing this for a decent touring bike?

In addition the the eZee rear mounting FP (flat pack) and the VP (vertical pack) batteries we also have a 37v 11.6Ah LiPo BT (down tube mounting battery) as shown below, which can be fitted in addition to either the FP or VP batteries or supplied with an eZee conversion kit.

 

In theory, it would be possible to have 3 eZee batteries, 20Ah VP, 14Ah FP and 11.6Ah BT mounted on an eZee bike and wired in parallel giving a total of 45Ah.

 

The obvious downside is it would be heavy, but capable of a long range.

 

[ATTACH=CONFIG]5084[/ATTACH]

 

What is the life span of these bottle battery's, 1-2 years or longer.? and the cost please.

 

Thanks

I personally prefer the look of the bottle battery on the down tube, it does seem the most natural position compared to rear fitted positions, which all look like a last minute after thought in design

My preference is (1) Behind the seat tube, followed by (2) In-frame but not necessarily on the down tube, this latter preference for off-road types of bike.

 

I don't think the behind the seat tube additional length a disadvantage in road riding, it keeps the battery weight low and out of the way of any cycling function and it easily accommodates step-through frame designs or folders. I see no reason why an e-bike should not look like an e-bike, and trying to pretend it's not with a mock bottle battery fools very few.

I have my batteries in the panniers so the weight is further down compared to a standard rack mount. I do intend one day making cases and brackets for the sides of the rack. Maybe you makers can consider doing this for a decent touring bike?

 

We have battery bags specifically for the eZee FP and VP batteries shown below.

 

VP battery bag for side mounting.

[ATTACH]5085.vB[/ATTACH]FP battery bag for side or top mounting. A carrying strap is also included.

[ATTACH]5086.vB[/ATTACH]

What is the life span of these bottle battery's, 1-2 years or longer.? and the cost please.

 

Thanks

 

Hi Jebb,

 

The bottle batteries supplied by eZee come with a 2 year warranty and the cost is £475 including charger and delivery within the UK.

 

The cases my may look like cheap generic type, but the cells and BMS are not.

 

A newer version is now available with a different case as shown below.

 

[ATTACH]5087.vB[/ATTACH]

My preference is (1) Behind the seat tube, followed by (2) In-frame but not necessarily on the down tube, this latter preference for off-road types of bike.

 

I don't think the behind the seat tube additional length a disadvantage in road riding, it keeps the battery weight low and out of the way of any cycling function and it easily accommodates step-through frame designs or folders. I see no reason why an e-bike should not look like an e-bike, and trying to pretend it's not with a mock bottle battery fools very few.

 

I completely agree with you Tony.

 

The only bottle battery that looks in anyway stealthy is the one from Cytronex, but that has a relatively small 4Ah capacity.

Hi Jebb,

 

The bottle batteries supplied by eZee come with a 2 year warranty and the cost is £475 including charger and delivery within the UK.

 

The cases my may look like cheap generic type, but the cells and BMS are not.

 

A newer version is now available with a different case as shown below.

 

 

Thank you.

The real answer of course is for manufacturers to invest in the R&D to deliver smaller batteries with higher capacity (we've come a long way but not nearly far enough). Then the mounting options become far less of a problem as there's so much less weight and bulk to accommodate.

 

I've read somewhere that IBM (International Business Machines) the computer firm has said that it has entered the battery design field and hopes to use its computer chip nano technology to increase current battery capacity up to five times that at present for the same size units.

 

Yours sincerely

 

Linfitter.

We have battery bags specifically for the eZee FP and VP batteries shown below.

 

VP battery bag for side mounting.

[ATTACH=CONFIG]5085[/ATTACH]FP battery bag for side or top mounting. A carrying strap is also included.

[ATTACH=CONFIG]5086[/ATTACH]

 

Not a lot of people know that..... I certainly didn't

I've read somewhere that IBM (International Business Machines) the computer firm has said that it has entered the battery design field and hopes to use its computer chip nano technology to increase current battery capacity up to five times that at present for the same size units.

 

There's already been much research in this area for some years now, but nothing has successfully emerged from a lab yet The chances of such a multiple being achieved in the near future are very slim. Higher capacity can be gained with any battery chemistry technology, but always at the cost of reducing the discharge rates. And that's where e-bikes are compromised, since they need very high discharge rate capability from batteries that of necessity on a bike are small and low weight.

Perhaps the less discussed topic of rapid charging could help all shapes of battery. I did see a charger advertised a while back that claimed a full 10a/h recharge in about an hour. At the time it was muted this might dramatically reduce battery life expectancy, but perhaps if it was only used occasionally whilst out on long trips and at all other times use the normal slow charge system.

 

It would be great to stop for an hours lunch and get a 10a/h recharge.

My preference is for rack mounting but as Dave said earlier most standard fitted ones are too far back and high, I managed to move the one on my Alien down and forward and it looks much better and neatly hidden by a small pannier set. Next preference would be for the behind seat post mounting position and then un frame mounting. I don't like the water bottle batteries they don't fool anybody or look particularly nice.

Its so interesting everyones idea of the ideal position of the battery-if you read back the first 5 postings each one has selected a different location. Its this variety of choice that makes these ebikes such an interesting engineering challenge but also the reason why there is no uniformity and that is why no volumes of scale can produce cheap batteries.

We have used the same water bottle style of battery on all our new performance range and that same battery is used by many of my competitors so at least that size/shape should have some volume and ready replacement availability,it is cheap at £198.00 so volume does have an affect.

Thanks for all your inputs but it seems very personal as to the best solution.

Dave

Kudoscycles

What is the life span of these bottle battery's, 1-2 years or longer.? and the cost please.

 

Thanks

 

Zebb,the LiMn04 battery also Lithium Ion,Lithium Polymer have about a life of 2-3 years,the LifePo4 batteries could have a life of 5 years plus....but LifePo4 has a lower energy density(is heavier and bulkier)so its difficult to mount in the water bottle position. I did approach a battery supplier at the Shanghai cycle show and we calculated that in the same size bottle it would only be possible to sqeeze 6 Ah of LifePo4 cells against 10Ah LiMn04,6Ah is too small range-for that reason LifePo4 batteries tend to be rack mounted or mounted behind the seat tube.

Dave

Kudoscycles

I did approach a battery supplier at the Shanghai cycle show and we calculated that in the same size bottle it would only be possible to sqeeze 6 Ah of LifePo4 cells against 10Ah LiMn04,6Ah is too small range

 

It's not just the range. You can't get enough power out of a LiFePO4 battery that small unless you use A123 cells or Headway cells, both of which are relatively heavy and expensive.