Possibly you can use a DC buck converter to drop 80v down to work with Bafang 48v, just keep output under 60vdc.

Appreciate the feedback regarding lithium battery power. I got what I got with these two 40 volt / 5 Ah Ryobi batteries. Each of them weighs 3.2 pounds. My hope was to use them in both the mower and an e bike but the voltage is only going to work for a lower volt motor and all the stuff I was considering is at least 48v range.

clearly I am no electrical engineer…putting these two batteries together to produce 80 v … is there a way to do that with a higher voltage motor?

Update on my battery setup:

I just ordered a new Echo 56v 5aH eForce battery from ebay, turns out the seller was sending out defective batteries without checking them before shipment. While I'm waiting for refund for the battery (probably 4-5 bad 18650 cells, easy to rebuild if you're in the business), I went back to my old standby Greenworks 60v 4aH, which is wired in parallel to Echo 58v battery. Greenworks automatically feeds the lower voltage which prevents error code 07h and engine shutdown.

Note my solar panel on upper right. I typically pull in 22 volts straight with no loads. I use a booster voltage converter to keep it at a steady 58v output for the Echo battery.

Basically an all day trickle charger that is outside and avoids house fires from defective cells.

Unless you're sticking with 36v ebike systems, I'd go with the 48v Bafang midengine which is 48v and can run 58v Echo batteries. I prefer Echo batteries because form factor is very compact and allows mounting in tighter locations as you can see below:

Note the newer Echo 56v 5aH battery on rear rack. Everything stays put with hose clamps. Unfortunately the older style 58v 4aH Echo batteries are being phased out but IMHO they are the ideal setup of an ebike. You can also run a 60v Greenworks battery in parallel that will prevent an over-voltage cutoff when Bafang controller detects +60vdc. Anything between 48vdc and 59vdc will run the motor. I also prefer the smaller 24in tires with dual suspension MTBs. I've seen new ones as cheap as $150 at local sports stores or online. I got mine for $40 at a campus police auction of surplus bike sales. Rear wheel was laced for Nexus 3-speed IGH but the newer 5-speed IGHs are dropping in price and are marketed by Shimano for ebike. Acutally 90% if the time, I'm use 3rd gear and PAS 3, anything faster than that on flats can put you in road kill category.

This is great info…I have a Ryobi mower from HD and managed to get an extra battery when the first mower died within warranty. They are both 40V 5ah and only weigh a couple pounds. I need to research the claimed voltage on these…40v seems to be a bit odd. A note on lithium batteries…running them down beyond 50% capacity on a regular basis really lowers your charging cycles. By having two batteries I cut the lawn with both and switch out after ten minutes or so. One battery used to do the whole lawn but it would get run down just about all the way. The other bit I was told is that these batteries do not like to be stored fully charged for long periods when you don’t plan to use them. Not sure why this is but I always run them down about 25% and store them inside in a controlled temp over the winter.

This was my first project e-bike. The Nexus 3-speed laced into a 24 in. wheel is functionally a single speed sprocket and single speed chains are recommended. The IGH shifts internally from the position of its push rod and the design doesn't need to shift through derailleurs.

The 2021 debut of Nexus 5-speed automatic transmission, aka the Inter-5E dynamic IGH, is a game-changer for the e-bike market. Now you can toss the shifter cables, the new IGH is designed for the Shimano Steps e-bikes to sense torque internally and shifts on its own. Haven't seen it sold separately like the other Nexus IGHs so I don't know when that will be on the market.

I'm riding my bike on flat roads in heavy traffic areas of Central Florida so between the 3 speed IGH and the 9 PAS settings from the Bafang, you're producing faster speeds than you need to be safely travelling.

I've increased the support on the bike's rack to handle the weight of battery a little better. I'm planning to add a front rack for a 2nd lawnmower battery so the weight from two separate batteries will be dispersed between the front and back.

I'm using a 5.0 amp-hour EGO 56 battery on my electric bike, a converted 24in dual suspension MTB with Bafang BBS02 and Nexus 3-speed IGH.

In theory you may think it is a mismatched battery but from my personal experience, it runs quite well on my bike when I'm not using the battery to mow with my EGO lawnmower. The battery doesn't care if it's being used to turn a 24 in. rear bike wheel or a 21 in. lawnmower blade.

In practice, I get about 5-6 miles on a 5 amp-hour battery fully charged with minimal pedal assist. I'm geared with stock Bafang 46T chainring and Nexus sprocket. I've used a Luna Mighty Mini 30T front sprocket to increase torque but had to put the stock chainring back on until I can shim out the 30T granny gear for a straight chainline, otherwise it bites into the plastic Bafang secondary reduction gear housing (fortunately most all Bafang BBS02 parts are easily replaceable).

I'm planning on adding a 4 amp-hour Echo 58v battery to extend my range of travel to have 9 amp hours of available power on the bike.

no, you cannot and do NOT want to use batteries not for their intended application especially not on a high end ebike motor, ie slapping random lawn mower batteries with a bafang. Could cause major issues. furthermore the range on something that low would be weak - just take the amps multiplied by the volts to get the watt hours ie for that battery 420 watt-hours which is very low range but they designed those mower batteries that way.

check out this link to see what batteries you would want to pair with an ebike motor: https://www.johnnynerdout.com/batteries-1

i got the 52v 20Ah triangle battery (1040 watt hours!) off amazon for only $374, which is pretty dang cheap if you ask me for a high performance LONG range battery, this could get you 40-80 miles on a single charge depending on how you ride and other factors. ie its kind of huge and overkill for most people. but just an example for you. Those shark batteries fit nicer on most bike frame bottle mounting points.