18650 vs 21700 battery packs.

[Retrorockit]

My 48V. 17.5Ah 18650 (Panasonic) pack is getting a little old after 3 years. Due to it's size it still has useful range, but it won't really power the 30A. BBSHD at full throttle for very long without falling flat.
I found a 13s 5P 40A. Panasonic 21700 pack that's more or less the same size physically. 48V. 24 Ah. Probably weighs a bit more.
18650= 18mm dia.X 65mm long cells
21700= 21mm dia.X 70mm long cells
It's from a US Vendor. So I'll see how this works out. It's a bit pricey, but comes with a charger. Since I own 2-48V. bikes a 2nd charger is a good idea for me anyway.
https://www.eco-ebike.com/collection...-40a-discharge

[Gigi Liu]

Maybe you can take Gimibattery ( www.gimi-battery.com) into consideration. The battery they have Brand cell as well.

[Diggs Ut]

Careful - A 14s pack requires a 52v charger. You can run a 52v pack in a 48v system but charging them requires different chargers.

[AZguy]

Retro isn't new to this and definitely knows about 14s vs. 13s

[Retrorockit]

Actually I'm new to battery specs.. It IS a 13S pack. So far I've only used the batteries that came with motor kits. This is my first battery shopping experience. But I'm always up for trying new stuff. I'm sticking with 48V because my TSDZ2 is also 48V. and I don't need more power form the BBSHD.
My BBSHD had a Reention case, and the TSDZ2 had a Hailong Shark battery. So they didn't swap. Now I'll be Shark on both bikes, so I'll have a 12Ah spare battery for the BBSHD, and 2 chargers so no waiting to charge either bike.I'm excited about the 24Ah capacity. I used to have to choose whether to ride fast, or ride far. Sometimes headwinds made the decision for me. 37% more capacity should eliminate that compromise.

[AZguy]

Haha - you've been around the board enough for long enough just figured you had more than one battery... my bad

I've got like half a dozen... if I were shopping I'd definitely go 14s (presuming controller compatibility)... I've found the cost delta is usually right about 14/13 so no real cost penalty (and no real cost benefit)

[AZguy]

My impression of the 21700's is that for a given Li-ion chemistry as a battery they will provide somewhat more energy mass density and a little more energy volumetric density

They take less intercell wiring but seem to be more expensive and haven't really become all that mainstream.... yet...

[Retrorockit]

My old 48V. Panasonic 18650 was 17.5Ah 840Wh No complaints with that battery.
The two 48V 21700 options were.
13S/4P, 19.2Ah 40A for $600 (with charger) Not cheap , and not much improvement 921Wh.
13S/5P 24Ah 40A for $50 more. 37% more capacity than my old battery had when new. 1152Wh I'll write a check for that!

FWIW the 21700- 52V. option at 14s/4P drops back to 19.2Ah. 998Wh, Small potatoes.

[AZguy]

Hardly voodoo

Dividing the sum of the initial voltage and the final voltage by two gets the average of the two so is a suitable approach to calculating energy capacity - and as explained if the discharge voltage was linear, entirely accurate

OTOH the accepted approach is to use the nominal cell voltage (3.7V) as I did in the latter example

The difference between the two methods for a 52V 20Ah battery would give the 974Wh as explained and if using the nominal cell voltage (optimistic since it would require running the battery to 0% which nobody does) would give 1036Wh - very close and higher as expected



But again, the *only* way to know what the capacity is (usable or total), is to measure it with a Wh/Ah coulomb counting meter

[stts]

waste of time

[AZguy]

Engineering isn't about exact, it's about being close enough

[Retrorockit]

Based on the number of 21700 cells in a battery pack to get the Wh up to around 1100 The other good configuration I found was 16s4p=64 cells.
With 40A and 60V. this would probably be a good match for a Ludicrous controller. Not something I personally feel the need for.

[Retrorockit]

For fast street riding it comes down to tires, and brakes. Plus the wheels and suspension to make it all work. 40+mph you're going to be out in traffic.
Not something I want to do in the first place. In the wide open spaces it might add up to something.

[AZguy]

We already know we both approach this from very different angles... I don't ride on the street and for hard surface BBSHD power is plenty... I do ride off-road but with short suspension you can't go very fast for the most part anyway and typically crawling up anything steep/rough... with longer travel then you could take advantage of more speed/power...

[Retrorockit]

That gets you back to looking at an E dirt bike to start with. Everything is flat here, so unless I decide to start riding up stairways at 68 years old, It's not for me.

[AZguy]

That gets you back to looking at an E dirt bike to start with. Everything is flat here, so unless I decide to start riding up stairways at 68 years old, It's not for me.

Naw - not looking for e dirt bike, more like a downhill fat tire bike... looking for much less weight than the e dirt bikes... travel doesn't weigh much

I'm within a few years of your age too

There aren't any fat tire e dirt bikes (or fat tire downhill bikes) I'm aware of regardless so it doesn't really matter... I'm just not interested in anything less than 4" if only because of all the deep sand and gravel, but frankly for many other reasons. I found one or two longish travel fat tire downhill forks but even those seem to border on unicorn and fat tire long travel frames just don't exist - if they do I really want to be corrected (preferably if they're not ferrari pricing)...

Just got my new permits for some of the off-road out here ($15 for year of az trust land and $6 for 6mo of local place called bulldog canyon https://www.fs.usda.gov/recarea/tont...a/?recid=35555) and expect to be out during some of the upcoming weekends <salivation>

[Retrorockit]

Travel might not weigh much, but light weight can get real expensive!

[AZguy]

I think the greatest issue is finding stuff for the fat tires... if I was content with 2.5" or likely even 3" this would be pretty easy, most any long travel downhill frame would do... I get why the downhill guys don't do fat but I still think a downhill bike with fat tires would be perfect for my use case... and I'm not the least bit interested in downhill "style" riding...

[calfee20]

Naw - not looking for e dirt bike, more like a downhill fat tire bike... looking for much less weight than the e dirt bikes... travel doesn't weigh much

I'm within a few years of your age too

There aren't any fat tire e dirt bikes (or fat tire downhill bikes) I'm aware of regardless so it doesn't really matter... I'm just not interested in anything less than 4" if only because of all the deep sand and gravel, but frankly for many other reasons. I found one or two longish travel fat tire downhill forks but even those seem to border on unicorn and fat tire long travel frames just don't exist - if they do I really want to be corrected (preferably if they're not ferrari pricing)...

Just got my new permits for some of the off-road out here ($15 for year of az trust land and $6 for 6mo of local place called bulldog canyon https://www.fs.usda.gov/recarea/tont...a/?recid=35555) and expect to be out during some of the upcoming weekends <salivation>

It seems you and I have been looking for the same nonexistent bike. My enduro is my first try at a solution. It is too tall even for my long legs and too heavy. Then it has a hub motor which is not your cup of tea but vector bikes "https://vectorebike.com/" has a photo that is constantly rolling around in my head. I might try it some day soon and it might be what you are looking for.

[calfee20]

Here is a DIY in the same style.



This one has a longer wheelbase. It was built many years ago and I think some of the bikes out there are knock-offs of this rig.

https://www.electricbike.com/drunkskunk-fat-bike/

[AZguy]

Cool picture with the fat mid (although I'd likely prefer a double crown) - I ran across vector a while back but they seemed very focused on the more electric light motos than bikes and also rear hubs instead of mids

Yucky website though... sort of frustrating. I clicked on something that took me to a mid-drive like the one with the fat tires but they were skinny and now no matter what I click on can't get back to it... no real specifications either - wanted to see if I could find the travel

[calfee20]

I just about had to stand on my head to get that photo to post. I made two orders with Vector for around $1500.00. My second order was poorly wrapped and DHL man-handled it, so I lost a $44.00 front hub. Vector's response was VERY poor, and I have not bought anything since.

I believe Stealth makes a similar frame. I have a 100mm BBSHD that isn't doing much. Maybe it is time for another bike.

[AZguy]

Do it! If I had resources ($ *and* time!) I'd be chasing this stuff

[Retrorockit]

The 21700 battery arrived yesterday. They didn't tell me it had been shipped, and I wasn't expecting Sunday delivery, but whoomp there it was. I now have 3 different 48V. batteries with 3 different chargers, and 3 different mounting brackets. Nothing interchanges. Oh well.
I did some measuring and the new Shark is the same width as the old Shark on the TSDZ2 bike. A little wider than the Reention 16.5Ah battery I had before The height is exactly the same as the Reention 16.5Ah battery It IS an inch longer. The biggest physical difference is weight. The old one is just under 9#, the new one is just over 13#. About 45% more.
The new one has 65 21700 cells inside. 13sX5P=65 cells.
The old battery had 48V.X16.5Ah= 792Wh
The new battery has 48Vx24Ah=1152Wh
1152Wh/792Wh= 1.45 the same 45%
So lets look at cost effectiveness of the 21700 battery. I paid $650. subtract $50 for the included charger lets say $600 is pretty close.
$600/1.45= $413 I don't recall seeing large 48V 18650 packs for that price from known US vendors. It's rated 40A continuous so good enough for a BBSHD.
The price looks a little steep at first but for a BBSHD I think it's the right choice.

Unfortunately the new bracket doesn't line up with the water bottle holes like the old one did. I'm going to have to add a couple more to get the battery low in the frame where I want it. Considering the weight increase an extra mounting or 2 makes sense anyway. I'm pretty sure this weighs more than a water bottle.

[AZguy]

That definitely seems like a really good deal

[Retrorockit]

I think this should allow me to take long out and back rides, plus do some dicing with traffic if the need arises. I'd probably have to work at it to run this battery down in one ride. The 16.5Ah wasn't bad about this when new. Almost 50% more capacity is going to be something else.

[Retrorockit]

I got it mounted today. I must say I don't like the bracket on this specific battery. I can usually just stick a bracket in position and transfer the location of the holes and get it mounted. This bracket is in 3 pieces, and 2 of the holes are covered unless you disassemble it. I got it mounted with 4 steel water bottle mounts (only 1 of the existing ones). They also come in Aluminum. I don't recommend those. Tip- It's real easy to drill 2 holes in a straight line. 4 of them not so much. My advice is make a drill guide out of wood. Bolt it to the existing holes. The multi piece bracket is useless for this.
I only ended up with 1 extra hole. I'll wire it up tomorrow. It was too rainy to ride today anyway. I can feel the extra 4# under pedal power.
Eco Cycles sent me a notice to day that the battery had been shipped. 2 days after I already received it. Now that's fast service!

[Retrorockit]

Basically what they did was put the plug between the battery and the bracket on the bottom where it takes the place a middle mounting bolt would go.This leaves a pair of mounting holes at either end of the bracket.This means if your bottle bracket is in the middle of the tube you will be S.O.L.as far as mounting this and riding away. The front bracket is a short piece of aluminum that's not attached to anything. It's free to slide into the plug area until it's bolted down. if you use just this to bolt the battery down the only connection between the 14# battery and the bike will be a section of plastic bracket about 3" long. I think the very minimum to mount this would be 1 hole at each end. Way too far apart for any bottle mounting to work. Plan on adding another bottle mount for this battery.Since you will be adding them at the end of the tube where room for a drill is limited plan on having an angle drill, or 90* drill adapter to do this.
Reention avoided this by putting the plug at the back of the bracket, having holes along the whole length, and the 2 metal pieces were bolted to each other. Move it an inch either way and you have 2 holes to use. I guess Hailong expects the bike to be built to fit the battery. I guess having the bolt holes further apart is a more secure mounting. But not user friendly for the casual DIY project.

[AZguy]

..pictures?

[Retrorockit]

I'll get some pics. later. Getting the bike running again is job#1.
Looking for comparable batteries I'm finding the 52V. Lune Dire Wolf with 1100Wh $795 (85 x 18650 cells), and some triangle packs with 24AH in the $800 range.
So I think it's worth doing, and the extra mountings actually make sense. Just be prepared for some fabrication to get this installed. I didn't have everything I needed on hand when I started this. Chasing down steel bottle lugs, and special drilling tools took some time. It wouldn't be much trouble if you're prepared ahead of time. LBS rats would have this stuff on hand already.
Drilling 4 holes in a a straight line, on round tubing, in the corners of a bike frame takes a little planning. The disjointed bracket is almost useless as a fixture.
You could probably get away with 2 bolts. But they will be far, apart so drilling will be required. I underestimated this thinking it would be a bolt on deal. It's not!

[Retrorockit]

To be fair Eco Cycles sells something from Grin Products called a Triple Bob battery mount. This is an adapter to attach the battery using 2 or 3 hose clamps.
For this particular battery it might move it back into the bolt on category.
https://www.eco-ebike.com/collection...cts/triple-bob
I didn't order one because I don't want hose clamps over the nice Gary Fisher graphics this bike has. This also means your battery can be stolen with a screwdriver.
My other 2 battery brackets both have 3 slotted holes. To get a lower profile on this battery they moved the electrical connector down inside the bracket and removed the third slotted hole.
There are 2 holes hidden inside the metal electrical box. But nothing in the middle part of the bracket.

[Retrorockit]

The lock on this is different too. It's a dead bolt type. if you're used to sticking the battery on the bracket and it's locked you would be wrong. This one needs to be locked with a key.
On my other brackets the lock bolt goes into a blind hole. So there's no way to push it back in with a tool and take the battery. On this one the bolt is exposed at the bottom. Probably to make a thinner bracket. So it needs a deadbolt design to avoid the above mentioned exploit. So if you don't lock it with a key, it's not locked! I suppose someone could drill a hole in the plastic and take the older type that way, so I guess it's better as long as you're aware of the need to manually lock it.

[AZguy]

Just use a pry bar?

[Retrorockit]

Probably. it's still worth something for scrap metal.

[Retrorockit]

I got a ride in. Cool weather almost no traffic at night so I went for a long one and used more power than I would have before. At the far end of the ride ouit I ran it at 900W for about a mile. It dropped 1 bar. I had a cup of coffee and it came back to full. About 5 miles later it dropped 1 bar again and stayed there. About a mile from home where the other battery would have been getting thin i gave it full power for about a 1/2 mile and it dropped to 50%. At home I ran it up and down the street at full power until I got bored. It never went down to 25%. So this thing does have some staying power. I'm going to have to watch the batteries on my headlights with this thing. I think it can out last 2 of them if I'm not careful.