Add a Bafang to a DD Hub Ebike?

[MeanGene36542]

I saw at least one user did this in an earlier thread. I didn't see many comments on it though. I currently have a 36v 500 watt DD w/ 16Ah LiFEPO4. I currently get 20+ miles "going fast"... 28-32 miles "normal" on my regular ride combining a fair amount of pedaling. But when I ride 40-50 miles fairly occasionally I get very nervous. I like to pedal because I want to... not because I have to! I need more range... a little more speed would be great but not mandatory. I can't add more capacity to the rear rack or a triangle bag in front. I do have room for a frame mounted "water bottle" style battery. I've been toying with the idea of two battery banks, LiFEPO4 in back, and 36v 16.5Ah-29E in a "bottle mount" on the frame. Now I wonder if just adding a Bafang along with a "bottle" battery would make as much sense? Any thoughts here?

 

[amberwolf]

I need more range...

<snip>

a little more speed would be great but not mandatory.

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I can't add more capacity to the rear rack or a triangle bag in front. I do have room for a frame mounted "water bottle."

<snip>

Now I wonder if just adding a Bafang would make as much sense?

If you mean adding a second motor system to the bike, without adding more battery: it's probably going to *decrease* your range, because of the added weight, plus if you set it up so you can go faster while using it then you'll end up using even more power even faster, and get a lot less range out of what you have.

If you want more range, you'll need more battery.

If you want more speed *and* more range, you'll need even more battery.

If you just want more speed, you may be able to add a higher voltage battery to the bike (replacing your existing one with a 48V 36Ah would probably net you the same range at the higher speed you may get out of it, assuming your existing controller tolerates the higher voltage (probably) and doesn't have a speed limiter.


For adding more battery, there's a few ways:
--a bottle battery, if it adds you sufficient Ah for what you want to do with it.
--fork-mounted battery; either on the fork legs (essentially front panniers; if they're low enough they may not make a huge difference to handling, if they're not really massive), or on the fork crown/headtube area. Both have been done here on ES (and elsewhere as cargo carriers), with good success.
--backpack; worn only when you know you'll need that extra range.

there's other ways too, but those three will probably give the best handling if you can't put it on the rear rack (or as panniers) and can't do a triangle bag or box.

 

[MeanGene36542]

I've clarified my OP a bit... either way I'm looking to add a "bottle" style battery. I was just noticing how little extra it would be to add a Bafang at the same time (EM3C). It would also give me option to go 48v if I wished, although I see that in bottle style the 36v has much more Ah available (16.5 vs. 11).

 

[amberwolf]

the wat-hours are pretty similar, though, so you'd get nearly the same total energy out of the 48V vs 36V.


If you have the money for it, nothing wrong with ordering the Bafang drive as well, and replacing the DD with it if you want to make the bike lighter (guessing that your hub is probably heavier than the middrive).

If you don't mind the reduced range / heavier weight you can add the middrive to the bike with the hub still on there.

How much the range is reduced depends on how many starts/stops you have to do, and how many hills or slopes vs flats. The more weight, the more power each of those takes.

It also depend son the speed you go--if you go faster, it takes more power, and the power cost increases dramatically past 15-20MPH. (not including headwinds/etc).

It also depends on how you use those drives, wheher you use both at once or one at a time, etc. Sometimes it's useful to have more power on tap for startups and hills, and usuing both mtoors at the same time would letyou do that--but it'll cost you in range.


(I have 2WD on CrazyBike2, and it uses significantly more power to use both hubs for startups than it does to only use one, but it gets me started and up to speed a LOT quicker, and most of my rides are short commutes to work (around 5 miles total each day). Longer trips (up to 50+ miles) are rarer, but I usually ride much more conservatively when I do those (and add my extra battery packs).

 

[wesnewell]

If you just want a little more speed and more range, then just go to a 48V battery pack. That will add about 5mph to what you get now which I guess is around 20mph top speed on 36V. BTW, I calc you should have a range of ~60 miles at top speed (20mph) with what you have now. 500w motor and 36ah 36V battery pack. Going to a 48V pack will increase your range by about 20 miles if you ride the same speed.

 

[MeanGene36542]

Sorry... its past my bedtime, I have 16Ah, not 36! I've corrected my OP.

 

[dogman dan]

The additional motor would in the first place, just be more weight when you aren't using it. That should reduce range some, but not a lot.

The main benefit could be getting up hills with less wasted energy, but able to coast unpowered when you don't need it. So there are specific ride conditions where it could mean getting up a huge mountain more efficiently, or even at all. But of no particular use on most peoples daily commute, unless you commute to a ski area or radio antenna.

To simply increase range, just find a way to carry more battery, or grab a quicker charge along the way. This is a good excuse to take the hobby king lithium cobalt plunge. For just occasional use, you don't need a fancy expensive lipo charger or a lot of investment in packs. Two 5000 mha (5 ah) 5s packs will make you a nice 36v 5 ah reserve pack. Then charge it with a dirt cheap 50w rc charger. Sure, it will take a long time to charge, but you only need it occasionally, not daily. A very small lipo stash won't be so hard to charge or store safely.

This (5ah) is so small you can literally carry it in your coat pockets. But I would look at handlebar bags, then put the packs into a stiff homemade compression box inside the bag. 36v 10 ah is still only about 8 pounds, and fits easily in a large handlebar bag. Having this extra 5ah reserve pack up your sleeve will take all the anxiety out of the long rides, or expand it to expand your rides. You could carry a shitload more in a knapsack if you wanted to.