Battery in backpack vs. mounted to frame

[drew12345]

I used for couple years. I stopped last year because I hurt my back in non biking incident. I actually liked it. I ride offroad a lot and made the bike light and agile.

If u check out my signature, my most recent backpack was very stealth and protective. It was camelbak with battery inside pelican case to protect it. The battery was 25r cells 17ah from em3ev. The prior backpack was using hardcase backpack with lipos.

I used anderson connectors for my tether cord and never had one accidentally disconnect and I was riding bumpy trails. It was perfect tension.

It did get sweaty though. It never felt heavy on my back but did when just carrying it around like to charge it.

I have an ebike frame now and have to say I prefer batteries in frame. Its easier and one less thing to think about.

 

[2old]

This could be (PROBABLY IS) a horrendous idea, but I had a weight vest with 40 pockets evenly spread around it with each one accommodating a one pound "18650 shaped" steel rod (used it when I thought I was a stud and trying to get stronger on my MTB). The weights were well protected and the vest wasn't noticeable (except for the weight which I now have some of around my midsection and my back would sweat in hot weather). Possible to fashion into a "battery vest"?

 

[parajared]

On road I prefer it on the bike. Off road I like it better on my back.

Same here, I like the bicycle itself lighter because you can kick it around, bunny hop and do wheelies and stuff on the trails. I have tried batteries on the rear-rack, batteries under the seat, batteries between the legs and backpack works best for me for trail riding.

 

[Grizzl-E]

Ya I honestly don't feel 1kw on my back but I really do on the bike. But that only adds around %5 to my body weight. Where as on my light 2wd bike I'm adding %20+ to the weight.

 

[Baron]

I actually got my battery backpack set up the other day, tested it out, but ran into some trouble. Probably because i made the battery tether wires too short. I made them 1 ft long when i really needed 2 ft. They connect to the controller wires which are attached to the seat post, you really need 2 ft of coiled tether if you want to stand up on the bike.

So now I'm experimenting with top tube pannier bags and/or a custom aluminum case that's attached under the bottom tube. My bike is an Ironhorse Yakuza Aniki for reference.

 

[Grizzl-E]

Oh I forgot to mention if you want to go super stealthy get some climbing webbing (nylon strap type stuff). It's usually hollow so you can run your cables through it. Plug in under your seat and No Visible Wires!

 

[parajared]

Give "coiled extension cord" a try for backpack use, gives you a little stretch when you stand on the pegs.

 

[craneplaneguy]

The only coiled wire cord sets I've seen seem to be 16 gauge or so, have you found some with 10 or 12 gauge? Just two conductor would be nice also.

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[Phife]

I made my own Coiled Cord after I had trouble finding 10 gauge coiled cord premade. There is a supplier, called Curly Cord http://www.curlycords.com.au/ they sell the 10 and 8 gauge coiled cord, I got a quote for the length I needed (16" Straight tail, 16" coil and 4" strait tail) in 10 gauge 2 conductor and it was around $90.. much too pricey for a piece of wire. Also, it only came in bright orange!

Heres what I did, I bought some 10 gauge power and ground wire from my local car audio store and put that through some heatshrink tube. Then I started wrapping that around a 3/8" metal rod, I heated and shrunk the heatshrink as I wrapped, then blasted the whole coil with the heatgun to really let it all get hot and take its shape. After cooling the wire held the coil and its been working great so far! Less than $25 for the whole thing including the antispark xt90's

Im using a Evoc FR Trail backpack, my luna cycle 52v 20AH NCRB pack fits in the backpack perfectly, right at the bottom, The camelbak sits just above it in its own water proof compartment. The pack is 20L so there is still lots of room for snacks, tools, and extra clothes. The backpack has a back protector plate that will save my back if I crash, and I wrapped the battery in 1/2" Neoprene Foam for extra protection. I very comfortable and I much prefer the battery on my back vs on the bike. My other bike has a dolphin pack on the downtube and that bike is not nearly as agile or light feeling.

The power wire runs out the bottom of the backpack and along the belly strap to the center clip, from there it goes to the XT90 connector just behind my bikes headtube. I have full range of motion this way. I love it! the XT90 pulls out with a bit of force in the event of a crash but holds tight otherwise.

More pics in my bikes thread below, check it out in my signature.

 

[craneplaneguy]

Ingenious!

 

[The Stig]

+1 for backpack battery working pretty well. too bad there's a lot of nay saying / some trolling on the first page of this thread. I know downhill riders that like it. I even like it on the road because taking the weight off the bike makes the bike handling so good.
You just need to set it up right:

- Battery under 5kg recommended, as dogman said the shape matters, slim is good, a flat pack is best, maybe 4-5cm (2") thick.

- XT90-s connectors. They're all around great and they pop out if you pull on them.

- Umbilical that has the right amount of flexy-ness, I think two 12 gauge wires, side by side, work well, I recommend that they are shrink wrapped all the way.

- Good backpack with waist buckle. For the wire coming from the battery, you can feed the umbilical around the waist belt so it points toward the front.
For the wire coming from the controller you can feed it in under the back of the saddle and make it stick out from under the saddle 6 inches toward the front of the bike.

 

[BikeB4Drive]

I would consider riding with a simulated battery weight at least a couple times and for about the same period of time you expect and the same terrain. I commuted a lot on my naturally aspirated bike before I built an ebike and I found once I exceeded a certain weight that I would end up with a sore back later or injure it doing something minor. Good luck, if you protect the battery and keep it from bouncing around with other hard stuff you can probably do it safely but I don't consider LiPO safe. Also, you don't want any chance of shorting wires either setting the disconnected pack down or while riding. Choose your wire routing wisely. A pack can come of quick if you're not unconscious.

 

[sketchism]

i tried it and liked it untill i went to 24S2p 32AH of multistars and it was just wayyyyyyyyy too heavy to wear on my back

 

[nutnspecial]

I totally hear the benefits of why on-back is desirable. The simple logic in weight ratios of batt to body vs frame is a good one. Even with 10lbs though - or maybe because of 10lbs- I don't wanna mess with a backpack and a tether.
I wanna jump on my bike, hit the key, and just go.
When choosing to use a backpack, it's for carrying all kinds of other stuff, and/or extra battery.

Good news is as batteries grow more energy dense, we will find less reasons to ever seperate them from the bike to ride?

 

[craneplaneguy]

I got lucky, just after installing a rear rack on my Sturgis Bullet (https://endless-sphere.com/forums/viewtopic.php?f=3&t=79113) I at first had some vague ideas of carrying an extra battery (or two) in pannier bags hanging off the new rack, but then I realized I had ended up with a space between the seat post and the front of the rack, wasted space as it were. Yesterday, I had my padded 11.6 AH pack I hang from the Montague's top frame (about the only place I have) off and something clicked: I tried to see if it would fit in the odd shaped space on the Bullet left by the rack, and it fit perfectly! And, I can use the same straps and quick click fasteners I use to hang it on the Montague to secure it to the seat post! I love it when things come together that well, like I had planned it, when it was only a dumb accident.

I went for a short ride, my first with two batteries on board (my regular pack on the Bullet is frame mounted) and couldn't tell any difference. Then I put my third battery from the trail Viper in my backpack so now I'm packing 3 packs, and it felt great. I think I just stumbled on how I'm going to max out my range when on epic Bullet rides I think I understand that several small packs are not as efficient as a single large pack of the same size, something to do with voltage sag and maybe overheating? But for not having the room for a monster pack, I think this will work for me OK. Plus it will be real easy to judge when to turn the hell around and head back, and for shorter rides, the norm, I'm happy with the range of my single pack and I save weight.