Charging ebike on the go with a portable power bank?

Alex M

Active Member
23 extra pounds for a DD motor & long range battery is bad enough. Besides lead acid batteries, in the "maintenance free" variety, sulfate up and become useless if not exercised some large percentage of capacity several times a month. I'm hoping lithium ion batteries don't have the same syndrome.
Exercising is what generators need - running it once in a while, so that stale and dried fuel wouldn't cr-ap the carburetor and fuel lines.

Led acid batteries, whether it's wet or AGM, don't need this kind of exercising. But they need to be 100% charged most of the days. Failing that, they need what is called "equalizing" - bring it to 100% and then keeping it for an hour at 15.0-15.5V, once every couple of weeks. This roughly can be compared to balancing in Li-ion cells.

AGM batteries need equalizing too, but for this group the procedure is not written, I think only the manufacturer of high-end boat batteries Lifeline have this procedure in the manual.

Li-ion batteries don't need to be charged 100% - they last longer if charged to 90%. Similarly to led acid, they need 100% charge once in a while - I think this is not a result of some inherent chemistry laws, but rather flawed BMS in many batteries that don't do balancing until cells are 90-95% charged.

Yes, car starter battery is a poor choice for battery bank. Better consider RV deep cycle or "marine" battery.
 
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indianajo

Well-Known Member
Led acid batteries, whether it's wet or AGM, don't need this kind of exercising. But they need to be 100% charged most of the days. Failing that, they need what is called "equalizing" - bring it to 100% and then keeping it for an hour at 15.0-15.5V, once every couple of weeks. This roughly can be compared to balancing in Li-ion cells.
Total myth. I have about a dozen lead acid car/tractor/mower batteries that were charged daily all fall/winter/spring for 4 hours to 14.8v Deader than doorknobs every spring. Open circuit voltage is great, current capacity about 50 ma before voltage drops below 12. Two years ago I tried discharging with a separate timer 6 hours at a 2 amp load, then recharging 4 hours 6 amp capability. No improvement.
I used to be able to de-sulphate the pre-maintenance free batteries by washing the plates in water then adding acid back, but that hasn't worked for 25 years. Not since the "Penney's maintenance free" battery.
I have to buy new tractor/mower batteries every spring. Vendors are very happy about that. I need air motor starters for my equipment since lead/acid is so useless now. Same with cars since I don't drive very much. Basically, I don't drive cars at all anymore, I ride the e-bike or rent a U-haul.
 
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Alex M

Active Member
Proper charging and equalizing is not a myth when you are dealing with RV/marine deep cycle batteries.

4 hours charging is probably not enough. This is a 3-stage process - bulk, absorb, float. The last 80% of charge are the slowest because the acceptance rate drops, you can't just shove a lot of amps in a short time. 14.8V would be the absorption stage, it must stay there for an hour or two, and then float at 13.6-13.7V. These numbers are subject to temperature compensation, it should be adjusted by as much as 0.3V when it's too cold or too hot, but you won't find too many off the shelf chargers with temp comp. Or - with a proper absorption stage and adjustable voltage set-points (different batteries have different voltage for absorption and float).

At the end of the absorption stage the state of charge is typically 85-95%, depends on the battery type. Turning the charger off at this point would leave battery undercharged and will lead to sulfation and cells getting out of balance. If you run it down to 30% charge, you shorten the cycle life even more.
 

DDBB

Well-Known Member
i have a honda EU-2000 inverter generator. it weighs less than a 100 AH deep cycle battery, it's very quiet and sips gas. If needed, I'll bring it in the back of the truck for charging e-bike batteries when we want to ride all day at a destination bike path location
 

opimax

Well-Known Member
the link goes to units which are to small , my batteries have more juice when charged then these devices, also need 4 amps per charger
 

6zfshdb

Well-Known Member
i have a honda EU-2000 inverter generator. it weighs less than a 100 AH deep cycle battery, it's very quiet and sips gas. If needed, I'll bring it in the back of the truck for charging e-bike batteries when we want to ride all day at a destination bike path location
For off grid multi day rides from a central location such as a campsite, I also carry a small gas generator in my vehicle. In my case, it's a Honda EU-1000i. It weighs just 29# and runs all day on a gallon of gas. I use it with 2 battery chargers in the evening or overnight if necessary. It doesn't bother anyone since It's so quiet.

For multi day, multi location off grid trips, such as campsite to campsite, I charge 2 batteries while driving using an in vehicle 2500W inverter.

I have a couple of extended bike only trips planned which I hope to do in the next couple of seasons. One is the Blue Ridge Parkway and the other is sections of "The Great American Rail Trail" which is more than half complete. For these, I'm considering a trailer for the bike to carry the generator & camping gear. That way, I could charge one battery while using another on the bike. In theory, you could ride continuously, stopping only to swap batteries.

I can easily get 100+ miles using 2 batteries and that in reality exceeds my endurance limit. Considering this, an "on grid" approach would be to just carry batteries & chargers and plan the trip to include campsites with power hookups or bike friendly hotels.

There are lots of options out there for powering our bikes. It all depends on how and where you want to go
 

Quedecree

Member
I wanted a portable way to recharge my ebike's battery when I'm camping - I have a single cab ute with a large enclosed back and flat roof and also had 6 spare 25yo 75watt solar panels that were recently replaced by 250w 24v panels for the house. So I rigged 3 panels in parallel on the roof of the ute and wired them into a 120ah AGM battery via a 20amp solar charge controller and also installed a 400w sine wave inverter. Ended up costing me a little over $800AU and is working well beyond my expectations. Charges up the ebike battery no problems as well as all my lithium battery packs I use for work (chainsaw/hedgeshears etc) and I was also able to install a fridge/freezer. Despite being 25yo panels and lying flat, they still manage to put around 10-12 amps into the battery for the main part of the day. The panels were originally close to $800 each for 12v 75w when we bought them which is crazy when you look at the prices now.

Personally, I can't see any way to carry a power bank that would be more efficient than simply carrying a spare ebike battery but another alternative might be something like this.....

Although the price seems very steep for what you get - I think you could put something together for much less.
 

Timpo

Well-Known Member
i have a honda EU-2000 inverter generator. it weighs less than a 100 AH deep cycle battery, it's very quiet and sips gas. If needed, I'll bring it in the back of the truck for charging e-bike batteries when we want to ride all day at a destination bike path location
Using gasoline to power electric motor???

GM has done it..

Chevy volt is not a hybrid, because gasoline engine is there as a generator, not to move the car.