Variable voltage controller for ebikes

[bencrvr]

Hi, newb with an idea here. Is it possible to adjust the current on a 12v lifepo4 battery to directly power an ebike? If so, would it be possible to make a controller that can adjust the power to match the needs of any ebike? I want lifepo4 chemistry but most ebikes use lithium ion for the greater energy density. I want the fire safety and lack of cobalt and toxicity of lifepo4, and the long life of the battery. So I figure simplify the ebike thing by putting the weight on a trailer and convert the current to the needs of the bike. Then the bike is a lightweight normal bike and the trailer is a sweet mobile power generator, then out together they become unlimited transportation. I want to get some 12v Waterlily microhydro turbines for an additional 360 watts/day in fast water. Roof the trailer with a sweet panel and it becomes my ideal version of vanlife.

If someone could figure this out I'll buy one. I think it could be a big money maker as it could give new life to old ebikes made by companies that went bankrupt. Seems like it'd be a small product too, just some wires and controller boxes. The hard work would be in the design and programming. We could provide the battery and the rest of it, but that controller is pro level stuff. So, someone please do that or tell me how. Thanks, Ben

 

[tictag]

Loving the idea and I actually embarked on almost this very project for my eBike. Got the schematics, bought the connector adapters, cables etc Then hit a barrier that, whilst definitely traversable, caused me to pause ... and I haven't revisited the project since. That barrier was that the eBike would only except a charge via its external connector once it had successfully digitally 'handshaked' with the charger. The charger:

• Confirms that it is an official charger
• Exchanges information on the charging capabilities of the charger
• Responds to a request for a specific charge from the eBike

If memory serves, this was all done over a serial I²C communication protocol so easily hackable with a simple microcontroller, just haven't got around to actually doing it.

Don't know whether my eBike (Canondale Quick Neo EQ) is typical - maybe others just 'take what they're given', so to speak?

 

[Craig]

Hi, newb with an idea here. Is it possible to adjust the current on a 12v lifepo4 battery to directly power an ebike? If so, would it be possible to make a controller that can adjust the power to match the needs of any ebike? I want lifepo4 chemistry but most ebikes use lithium ion for the greater energy density. I want the fire safety and lack of cobalt and toxicity of lifepo4, and the long life of the battery. So I figure simplify the ebike thing by putting the weight on a trailer and convert the current to the needs of the bike. Then the bike is a lightweight normal bike and the trailer is a sweet mobile power generator, then out together they become unlimited transportation. I want to get some 12v Waterlily microhydro turbines for an additional 360 watts/day in fast water. Roof the trailer with a sweet panel and it becomes my ideal version of vanlife.

If someone could figure this out I'll buy one. I think it could be a big money maker as it could give new life to old ebikes made by companies that went bankrupt. Seems like it'd be a small product too, just some wires and controller boxes. The hard work would be in the design and programming. We could provide the battery and the rest of it, but that controller is pro level stuff. So, someone please do that or tell me how. Thanks, Ben

You could possibly add solar to the trailer and have it self charging to some extent.

I do not know what the curent draw is on the e-bile but it could possibly be too much for lifepo4 in a reasonable size bank.

If you have any specs let me have them this is a project that interests me.

@tictag could the charger be hooked to a small inverter on the trailer? How many watts does it require?

 

[tictag]

But further to your query, yes, it's very to raise a typical LiFePO4 battery voltage to whatever the eBike needs using a commonplace Boost Converter Module (loads on Amazon).

My drone flight battery charger needs >12.4V in order to function so I use a similar module to boost the voltage of a 12V(nominal) LiPo battery pack I have (unfortunately the 12V output is not stabilised so dips below 12.4V when it reaches 50% state of charge). The module itself can be configured to provide anything from the supply voltage up to 60V at around 10A (gets bloody hot at 10A though!)

 

[tictag]

@tictag could the charger be hooked to a small inverter on the trailer? How many watts does it require?

That is a very good point, then you could use the manufacturer's charger.

Wouldn't work for my project, though, because I intended to carry around the LiPo pack in a pannier - basically wanted a range extender without actually hacking the eBike's battery.

p.s. There are loads of YouTube videos and articles out there on t'interweb describing how to hack eBike batteries - I just personally didn't want to do this whilst the Bike was still under warranty.

Edit: Added postscript

 

[Ped]

Adjust current or voltage? I assume you want higher voltage?

 

[tictag]

Adjust current or voltage? I assume you want higher voltage?

From my personal experience with my eBike, the charger kicked out around 40-odd volts, so in the case of my eBike, definitly needed to increase the voltage. Other eBikes may well be different - only ever had one. Appreciate that you posed your question to OP, just thought I'd contribute.

 

[Craig]

Yes I wonder how many volts these things need to run and the amp draw. I have many ideas in my head.

Im picturing an e-bike expedition that can haul a trailer and gear for miles on end.

 

[tictag]

The power consumption very much depends on the motor fitted, and these vary wildly. Cheap eBikes likely have a 150W motor, mine is about middle-of-the-road at 250W but you get some mountain bike eBikes that pull more than my water boiler! My battery capacity is 500Wh.

Also, do be aware that eBike legislation is different between the states and the EU - we are only allowed to have 'peddle assist' eBikes, whereas, I believe, you can have the 'peddle assist' and 'throttle' types over in the states - don't know whether the specs are different.

Here's mine:



Specs are here: https://www.cannondale.com/en/bikes...uick-neo-eq/quick-neo-eq/2019?sku=c63179m10sm

 

[bencrvr]

Thanks for all the info tictag. I know nothing about hacking ebikes, so I guess it's time to learn. I'm fine with ruining a warranty on say, a Ride1Up 500. That's what I've been eyeing and that guy responded to every email, even if he didn't know the answer, like with this device idea.

Tony at Luna Cycles said lifepo4 is less safe than other lithium ion chemistries but didn't say why. That confused me because of so many other sources saying lifepo4 is the safest chemistry.

I've seen boost converters in use on lifepo4 batteries so I still don't understand. To me, the difficulty looked to be in communicating with the bike. Maybe there's a way to bypass everything and go right from the battery/booster to the motor. Wondering if it could merge with phones so software exchange would be easier to download new drivers for different motors. If nothing else, turn off all the cadence/torque stuff and just throttle would be fine.

Man, how cool to be able to cut the cords on any old ebike motor, attach some connectors for this device, hook up the trailer, thread the new throttle controller up to handlebars, attach the brake lever magnets, and go, and keep going, then make camp, and keep going. So sweet. If you make some please let me know, set one aside for me to buy and test out.

 

[bencrvr]

Just had the thought the connector for the device could be put on the wire headed to the existing battery mount so that it could be reconnected. Use the bike like normal until the battery gets low, then connect the trailer wires and use that throttle. You'd have all the potential uses. No battery/trailer=normal bike, ebike with or without trailer, ebike directly powered by trailer, or use an inverter to charge the ebike battery normally at camp.

That was my first notion, get 2 bike batteries and use an inverter to charge one while using the other. But I'd really like to avoid those other chemistries if lifepo4 really is safest and this whole idea came from that. But that'd still be a pretty cool way.

 

[45North]

Yes I wonder how many volts these things need to run and the amp draw. I have many ideas in my head.

Im picturing an e-bike expedition that can haul a trailer and gear for miles on end.

Most ebike these days are 48v nominal, and actually charge to nearly 54v.

 

[45North]

Batteries range from about 16.5Ah for a fairly big one (see Luna cycle in Colorado)

Luna Cycle Fast Electric Bikes

Distributors and builders of life changing electric bikes.

lunacycle.com

down to around 10Ah for a medium size consumer model. Range on a fully-charged battery is typically around 80KM (50 miles) assuming you contribute around 50% by pedalling.

Commercial ebikes have a built-in BMS that takes care of everything. For a DIY conversion a very popular after-market BMS is called a "Cycle Analyst"
Both come with their own AC to 48V charger.

 

[tictag]

Tony at Luna Cycles said lifepo4 is less safe than other lithium ion chemistries but didn't say why. That confused me because of so many other sources saying lifepo4 is the safest chemistry.

I would agree, LiFePO4 is considered the safest lithium ion battery chemistry. Perhaps he was misinformed?


I still have this project on a backburner, I'll make a point of updating this post if I manage to crack the communication thing.