20150703-IMG_7206

Mounting Options for E-bike Batteries

June 28, 2015
12,639 Views

One of the first problems a new E-biker who wants to add a kit to their bicycle has to figure out is…Where do I mount the battery, and how? This article will help you see what the common methods are, and hopefully to help you decide what would work best for you.

Remember the ebike battery is the most expensive component in almost every ebike and also the most fragile. Which ever method you choose for mounting your battery, remember to use great care. Treat your battery like a carton of fresh eggs…and mount it with plenty of support and padding so that your cells do not become physically damaged. Ruining a few cells can ruin an entire pack. Never charge a damaged battery pack.

______________________________________________

Rear Cargo Rack

Mounting the battery on a rear cargo rack is a frequently used method on the most affordable kits. We don’t like them because they make the bike handle odd at the higher speeds, and if you use a common rear hub…most of the E-bikes weight is then located in the back. That makes the E-bike very awkward to lift and move around.

If you are using a large and very heavy Sealed Lead Acid (SLA) pack, the rear rack is often the only place that will fit, but…that is also the absolute worst place to put a large and heavy pack; high up and at the very rear.

 

xxx

Positioning a heavy hub and the battery both on the back is the “easy way”, but it handles poorly.

 

If this is for a kit, the cargo rack is usually the type that bolts onto your bike frame. These bolt-on cargo racks are usually too weak for the job they are given, and the bolts often work their way loose and squeak. Some factory turn-key E-bikes have a heavy-duty welded-on rack for a battery. For those, we still don’t like where the weight is located, but at least they are strong and don’t come loose.

______________________________________________

Triangle Mount

The absolute best place to locate the weight of a battery is as close to the center of the frame as you can, and as low as possible. One of the most frequent methods we’ve seen over the last two years to do this has been to use a triangle bag. If you have a hard-tail frame, you probably have a large triangle space, and that means you have a variety of affordable options when it comes to a triangle bag.

Here is where we recommend to buy affordable quality triangle bags made here in the USA: Luna Cycles

 

20150703-IMG_7206

 

______________________________________________

Water Bottle Mount Cylinder

When you Google “water bottle battery”, this is the type that comes up. It is a cylinder that holds 42 of the popular 18650-format cells. This limits either the voltage or the range, but it easily attaches to a frame adaptation rail that is bolted to the common 2-bolt water bottle attachment points. The range is dependent on the particular cell that is chosen.

 

xxx

The bottle battery size that is common and fits inside a bicycles frame triangle uses three stacked modules that hold 14 cells each. there is also a four-stack size with 56 cells, but it is very long and will not fit inside a frame triangle.

 

If you choose the 48V version of this pack, the number of Amp-hours (AH) can vary from 8-Ah up to 11-Ah. However, if you choose the 36V configuration (with the number of cells being fixed), having fewer cells that are configured in series means that more of them can be configured in the parallel groups. A 36V pack (as opposed to the same size pack at 48V) can have as much as 15-Ah, if a high-Ah per cell model is used.

 

xxx

This is the “water bottle” style of battery pack, on a Fat E-Monster from Lectric Cycles

 

______________________________________________

Dolphin Case

This aluminum hard case also mounts to the water-bottle attachment points that are now common on bicycle frames. In fact, in this picture you can see the second set of “2-bolt” water bottle attachment points on the seat-tube. Since the desirable 18650-format cells (cylindrical, 18mm diameter, 65mm long) can easily fit sideways between a riders legs without interfering with pedaling, this 80mm wide (3.2-inches) case is becoming VERY common.

 

xxx

The “Dolphin” style of hardcase is quickly becoming more popular.

 

This type of case holds 50 of the 18650’s, and to give you an idea of what’s possible…if you buy one of these cases from em3ev.com, and select the Samsung 29E cell (2900-mAh per cell), the 36V version can hold 16.5-Ah of range. Also, next year in 2016 there will be cells available to the public with as much as 3500-mAh per cell, meaning 20% more range with no other changes.

 

xxx

Here’s a peek at the insides of the increasingly popular Dolphin style of case.

______________________________________________

Top tube saddle case

Some builders have purchased cargo cases from bicycle sites that sit over the top-tube of the frame, with some storage space on either side. Kinaye Motorsports (shown below) puts their brick-shaped LiPo battery packs in a square-ish and affordable saddle-bag, and others who wanted even more volume have purchased a larger (and much more expensive) saddle-case from the German company Additive.

 

xxx

A saddle-bag style, that drapes over the bikes top tube.

 

Builders who like these, often have frames with the rear shock absorber located inside the bicycles frame triangle. They also often have a small triangle space, which doesn’t leave many options for battery placement.

______________________________________________

Front Cargo Rack

The pic below may look a little front-heavy, but many builders have recently tried this, and its not bad when you are using a large and heavy rear hub, like the Cromotor, the MXUS, or QS. With the overall weight of this E-bike polarised (half in the front, half in the back) it handles fairly well. Not as good as having a central battery and a mid-drive on an off-roader, but it actually isn’t bad…especially for a street bike.

 

A generic copy of a Pelican case, attached by accessory clamps to the stanchions of a dual crown fork.

A heavy duty and water-proof Pelican case, attached by accessory clamps to the stanchions of a dual crown fork.

 

The bike is a 2005 Giant DH Comp from endless-sphere.com forum member “Ohbse” in Aukland, New Zealand. The fork is the well-regarded Marzocchi 888 CR. The box is a Pelican brand, and he found the mounting clamps by searching Ebay for “Accessory Clamp 1.375-inch ID”. The clamps can be found for roughly $15 each. If you can’t find a clamp that is the exact ID of your stanchions, get ones that are larger and just shim them to fit with curved copper sheets made from copper tubing from a plumbing supply.

 

xxx

Generic aluminum tubing clamps and Pelican-style cases are easy to find in many sizes and shapes.

______________________________________________

Backpack

Our friend Miles uses a backpack for his lightweight eMoulton, and he does that to make this short and light commuter easier to carry into his work and back to the street. Very few riders do this, but it does completely free up the rider to use any frame they like without having to find a way to attach the battery in a secure way.

 

The backpack, cable, and connector that Miles uses on his daily commuter.

 

For builders who ride over 28-MPH, it is highly recommended to use a full-suspension frame, but…that also means that there is usually a shock absorber in the middle of the frame triangle (for most full-sus styles), which clearly makes it difficult to mount a battery anywhere.

Another benefit is that…in the very rare instance that the battery gets so hot that it starts smoking…it is easy to come to stop and dump the backpack, which prevents any damage to the rest of your expensive E-bike from a LiPo fire.

The battery is often the most expensive part of your E-bike system, and sadly…they are occasionally stolen. With a backpack battery, you will likely never forget to take the expensive battery with you, whether you are going into your home, a cafe, or some store.

Plus…if the controller or throttle freezes in the “ON” position (and won’t stop), all you have to do is bail out, and the battery will disconnect automatically when the connectors on the power cable pulls apart.

The pic below is courtesy of our friend Karl Gesslein from electric-fatbike.com

 

xxx

Using a backpack for your battery. This is Karl on his BBS02 mid drive fatbike

______________________________________________

Written by Ron/spinningmagnets, June 2015

 

Grew up in Los Angeles California, US Navy submarine mechanic from 1977-81/SanDiego. Hydraulic mechanic in the 1980's/Los Angeles. Heavy equipment operator in the 1990's/traveled to various locations. Dump truck driver in the 2000's/SW Utah. Currently a water plant operator since 2010/NW Kansas

  • Spoonman

    You mention issues with rear-mounted packs “at higher speeds”. What do you consider those to be? Over 20? 30?

    Also, you mentioned the scenario of the hub and pack in the back. How does it differ if hub is in the front, and pack in the back? Does that equalize it enough?

    I love the idea of the backpack, but worry about strapping a bomb to my back and heading out for the day. I already have a pack in which I keep things like my lights so I can swap between bikes easily, so that would be a simple upgrade. Plus, one battery for all my bikes. 🙂 Others in the thread have mentioned explosions, and I realize those were probably older, cheaper batteries in there (LiPos, I understand aren’t as explosive), but it’s still a worry.

    • roadkill612

      Been there as a young un. DONT.

      2 kilos on your back isnt 2kg when u hit a bump at speed – its massiver and sudden. spines were not built for it.

  • Bryan Martin

    I would like to see some actual statistics on 18650’s vs pouch cells. I understand thermal mangment is nessary as well as not pushing cells past there tolerance. 5 years ago people started building packs from laptop batteries that did not end well and since than they got a bad rap. How many ebikes really catch fire yearly? And are they home builds our production or professional conversions?

  • Magic Jeanie

    Im Sorry but i feel as though you have no idea on what your talking about, You bought Chinese batteries and that is your problem right there, Samsung use their 20 R and 25R cells in cordless drill and they are perfect for ebikes.

  • Magic Jeanie

    Jeff your rambling on about something you have no idea about, The reason your bike caught fire is because you have no idea on how to build a safe ebike by the sounds of it,
    I pull 60amps from my 5p of 18650 cells constantly and have over 10,000miles on the same pack with no problem at all. Stop telling ppl lies about your problems just because you have no idea.
    Any cells will burn if you dont know what your doing being pouch cells, 18650 or 26650. It all comes down to management and purchasing safe quality cells and going of your bike you would have gone as cheap as possible.

    • Richard Graham Poster

      Please learn the difference between your and you’re. You are = you’re. Your is posessive.

  • Wake and Vape

    wow what a story!

  • Wake and Vape

    thats a beautiful frame….thanks for sharing

    • Chaim Halberstam

      I built myself an off road Electric Endurobike using this DS frame from China, about 7 or 8 months ago. I have a humongous and heavy (19 kilo) 24s1p 30ah Lifepo4 A123 prismatic pouch cell battery rated @76v Nominal with a 60a-120a BMS and mated to an 18fet lyen edition controller running @55a constant 135a peak. It’s powering my 16*4 wound, Leafmotor 1500w nom (tbh it’s really more like a 2.5kw nom, and) My CA v3 confirms the 3500+w, or so on acceleration bursts and this Direct drive motor is really powerful and lifts you in the saddle when you start. The same factory that builds the frame, seem to now have a few pre-built models of different power ranges from 250w – 5kw as well as just the frame for sale, BUT the components used are not as good as those you’d put in your own build, and when going FAST(er) on a bike (even purpose built Carbon Steel!) Imo you’ll want good quality matching components to take that kind of abuse…
      Also the smaller 72v 20ah battery the Leili factory uses (also available to buy separately, @just over a thousand bucks + shipping but uses generic Chinese 10a pouch cells in a 24S2P config) for their TOP 5kw model, has a range that’s limited to 20-25 miles or so, but they’re also able to fit the controller inside the frame just above the battery, using some kind of PC fan to vent the controller’s heat, out through the seatpost gaps (Obv they cut and drill the cover over there.)
      Personally I chose an outside placement of my controller for better cooling, and I constructed a kind of shell casing to protect it and the exposed controller wiring, from stones and road debris, the controller itself is waterproofed though. I’m not sure how the factory fan method, will avoid inevitable water from getting inside the case!! in say a typical heavy NYC rainstorm?
      I love the Bike, loved the thrill of the building project, but I recognize that for the same money I could probably have bought a new Motorcycle! and if any problems occur from bad consruction I CANNOT blame anyone but myself 😉

  • Jeff Wilkins

    Hi first of all i have been making my own battery.s for the last two
    years using a programmable BMS and no problems ,so i don’t know why you
    would think i have no idea, i did not make the battery packs that
    caught on fire,it was nearly 3 years ago now you could not even get good
    Samsung18650 cells back then,and the only thing cheap is the small size
    of your Battery pack i,m not really a peddle bunny myself .I use NEC/
    NISSAN Cells, Capacity 35-37 AH Continuous Discharge 5C(180A) Momentary
    Discharge 10C(360A) on my bike,i don,t think 60A would even get my cheap
    V2,3000 motor warm or that 5P would last very long trying to get my fat
    ass up a hill.

  • scumbag

    bullshit

  • roadkill612

    A very important issue. Kudos.

    Some pragmatic non technical fundamentals as it seems to me:

    Go standard. A classic mountain bike frame. Its hard enough as it is.

    Mainly, my point is, slung from the crossbar is nearest to ideal, so assemble from pouches that best fit this model in one simple pack (the crossbar bag in the story seemed to be two separate packs which makes it a custom battery arrangement.).

    We mortals should avoid combo battery packs and balance charging etc. Thats where safety problems arise it seems.

    Why is anyone even talking 18650s when lifepo4 pouch seems such a no brainer now?

    There is no real reason any one format of pouch should be much cheaper due to volume than another. Only needs a different capacity or shape bag to offer options.

    I fancy the pouches which seem to be 15 ah, and are a long rectangle that should hang well from the crossbar. Pouches all seem 1cm thick so a 36v stack of 12 between your knees should be fine. NB a 20ah pouch is ~1cm (1/3″) thick x us a4 paper size & weighs .5kg. So you can work on 20ah 36v being 6kg e.g.

    Failing that, my second choice would be ON the crossbar. Much roomier, central & still lower than a bakrak. 6 kg there would scare me even on a mid-drive..

    OR

    3/ certainly for a front hub motor, why not controller & battery on a side front pannier rack just next to the hub. Off balance, but very low/ easy wiring.

  • roadkill612

    Where am i wrong?

    I read recently that only charging 18650s to 4.1v greatly extended their longevity.

    It seems most problems are due to eking out that last ounce of voltage – balancing.

    Personally, i would like the option to be happy with 4.1v.

    It seems even less important to stress a lifepo4 cell given their high discharge rates.

  • roadkill612

    I have long agonised over how to upgrde my crap bottle battery.

    Sadly, i didnt keep a snap to illustrate, but verbally…

    picture a MTB w/ no rear rack or fenders.

    Between the seat and the wheel is a spot for a lifepo4 brick if you think on it – resting on and strapped the rear fork struts where they join the seat post. I will run with a 15ah lifepo4 pouch setup – ~6kg.

    Its quite low and forward/central, a lot more so than a rack prism battery.

    Its a big flaw in a great bike. The frame is great, but has little space in the triangle for a big battery.

  • William Deleenheer

    I’d like to know about experiences with the dolphine case but on a female/step thru frame. Is it possible to put it on the downtube on these bikes?

  • Christopher Waggoner

    I call BS on this one. The Chinese batteries come with BMS and impossible to behave in this manner. Let’s have a look at a device that has the rawest and most dangerous connection on the planet for an 18650 battery… The e-cig. There has been 2 known catastrophe reported with those and both were under conditions equivalent to plugging in a radio while in a swimming pool.

  • Ron

    On the dolphin mount for the Killer Whale, how far does the batter have to slide back to take it off the mount? or do you need to take it off the mount to charge it?