Ebike battery charging

[dmp]

I'm thinking about a way to charge my ebike to 80% in order to prolong battery health. Charging all the way up to 42v is 100% charge, 80% would be to shutoff the charger at 40v.
They make smart charges to do this, but the cheap charger that came with my bike doesn't. The sealed charger is 42v / 2A until auto shutoff.
I was thinking three diodes might do the trick, in series between the charger and the battery? Anyone tried something like this?

 

[JohnRoberts]

IDK. Is the battery charge linear with terminal voltage or some more subtle metric?

JR

[edit- a quick search reveals some data, but no easy (cheap ) answer... Smart lead-acid chargers have gotten pretty inexpensive. They routinely use switching supplies and micro control. Lots of advice about charging ebike batteries advise against charging them indoors to prevent burning down your house./edit]

 

[sodderboy]

Loooooo-zuh technology. We will completely rape the earth and permanently enslave the already temporarily enslaved peoples of the earth with EV's as compared to burning fossil fuels.
The cars, bikes, scooters, skateboards, prams, etc. are certainly cool, I have used a solar tent ventilator for decades, but to scale-up for societies of millions of people will absolutely mash it all up, all over the place.
Your friggin' bike is petroleum powered anyway when you follow the source powering the magic plug in your wall, unless you have a chinese solar panel stuck out your window charging it or a whaterwheel gyro in the backyard stream. GET REAL. A two-stroke moped is less of a "carbon imprint" that your cool quiet bike.
Sell the bike at a minimal loss, go analog, and use your bloody legs!
If I had expendable income I would drive a Douchla locally with a vanity license plate STLPTROPWRD, just to blow the hypocrisy in people's faces, but I drive a Honda CRV @ 28 mpg. What an absolute load of stupidity going on these days!
[remarks about bloody diodes and and some other stuff removed]
Mike

 

[rob_gould]

Hope someone comes along to post something about rule #4 soon!

 

[JohnRoberts]

Hope someone comes along to post something about rule #4 soon!

4. You will find that the members of this community are courteous and respectful of each other, so please reciprocate those gestures. Leave the flame-war mentality at another forum. Personal attacks and generally hateful comments (regarding race, religion, gender, sex, etc...) will not be tolerated.
====
I did not see an emoticon so if you are serious, not only do I not see a violation, I don't want to debate it.

If you truly believe he violated the rules, report it. But keep in mind crying wolf when there is no wolf is not appreciated.

No, I do not actually want you to report him to me(us).

JR

 

[sodderboy]

[remarks about bloody diodes and and some other stuff removed]

My references were to the products created by the never discussed environmentally rapacious EV industry, not the loooooz. . . , I mean, righteous users of it.
A two stroke oil-burning chinese moped is indeed less of a carbon imprint on the gaya than a cool chinese electric bike. Look at the supply chain of materials needed for each vehicle and it's energy. Again I say, GET REAL. Bloody diodes. . . .
Yeah, I would like to ride down 10th Ave on an electric skateboard, those stockbrokers look like the king, but walking takes a bit longer and I can enjoy the scenery. And I will not have to toss a chinese battery in the earth a year from now when it is rubbish, or the board containing rare earth minerals a year or two after that. Complete consumer rubbish.
I almost bought an analog long board on Sunday at a flea market because I have a week-long gig in NYC and it would help getting around, but the guy would not take $15 for it. Adidas it is! And at my age you don't want to break a hip. . .
Mike

 

[dmp]

My round trip commute is 17 miles. Up until this summer I've driven to work.
Charging the e-bike takes 0.25 kwh, and costs $0.03 at $0.14/kwh. My Rav4 gets about 18 mpg in the city, so uses about 1 gal/commute, or $4, depending on gas prices. So the e-bike reduces cost by 99%
My Electric utility produces power at 1.5 lbs CO2/kwh with a mix of sources. So the bike charge is generating 0.375 lbs CO2. A gallon of gas is 20 lbs CO2/gal. So the lbs CO2 is reduced 98%

And the environmental footprint of producing the batteries? The bike has 20 18650-35e Panasonic Liion batteries for 250 wh.
Looking at estimates for the lbs CO2 to produce batteries, it's estimated to be between 0.1 to 0.4 lbs CO2/wh. This means the battery production generated somewhere between 25-100 lbs CO2. This is saved in 3-5 days of e-biking instead of driving.

Hope this helps remove some misconceptions.

 

[JohnRoberts]

Nice analysis,,, are there too many hills to pedal a conventional bike? Of course few offices have showers.

Rain and winter weather would benefit from more sheltered transportation.

JR

 

[dmp]

Nice analysis,,, are there too many hills to pedal a conventional bike? Of course few offices have showers.

Rain and winter weather would benefit from more sheltered transportation.

JR

No - it's a really nice ride. Relatively flat. Other than about 1/2 mile on a road, it's completely separate bike path. The bike has 5 levels of power assist and I use it pretty high on the way in and less on the way home. Nice to not be sweaty when I arrive (there is a shower but I don't want to take the time).
I don't bike on rainy days and probably won't with snow/ice. But I wouldn't mind the cold as long as the path is clear.

I haven't figured out the charger yet, but I threw out the inline diode idea, as that would drop the charging voltage through the whole charge. It still should charge at 42v and shut off at 40v. The chargers have a comparator to 'shut-off' and taper the charge, but the charger that came with the bike is sealed plastic.

 

[JohnRoberts]

A friend of mine living in a suburb of SF did something like a 15 mile commute for years, he may still. He also worked part time in a bike shop so he was kind of a bike guy...

The older I get the less I ride...

JR

PS; I recall getting really irritated when some guys on ebikes passed me climbing up one hill of my old 5 mile out/back loop.

Edit- IIRC microchip has some mcu app notes about battery chargers, but there are too many types of batteries for me to keep track of. /edit

 

[Tubetec]

Micro controled RC li-po chargers generally allow the user specify the final charge voltage per cell , trouble is more than likely what you have is a power supply and the charge controller itself is on board , after all Li-po's can be extremely dangerous if they arent properly balanced charged . My uncle is an RC fanatic since the days of valve/tube Rc , he's had a few close calls with Li-po batteries over the years ,a few of his friends havent been so lucky,
one guy crashed his plane into the ground , put the pile of junk in the boot of his car and drove off , some distance down the highway the cells combusted , he had to bail out and watch his pride an joy become a fireball .

Of course the modern electric bikes and scooters are much more effecient than hauling your ass around in a couple of tons of metal , the real downside is you get these assholes who blaze through stop lights on the cycle path putting pedestrians in serious danger , theres a few areas in my city where footpath/pedestrain crossings ,cycle paths and the road are only divisible by a faded white line . Many cyclists and scooter people blow red lights at full speed routinely . Its happened a couple of times to me where I have the green light as a pedestraian only to spot some douche comming towards me at speed 10 yards up the road intent on blowing through the red light , I look the fuckers right in the eye , and they take that as signal its safe to blow through , Ive forced a few into taking avoiding action , make my day muther fucker , you'll end up in hospital with a burly gay nurse with a hard on picking gravel out of your ass for weeks . Maybe it was similar experiences got Sodderboy all lit up with misplaced rage , im glad DMP didnt take it too personally even through its seems one or two might have assumed offence on his behalf , easier to make friends than enemies .

 

[dmp]

The battery is Li-ion. In my opinion the danger of these batteries is overblown (i.e. a status quo bias). The energy density of gasoline is 50 times higher than a current battery and extremely flammable - there's no free lunch with energy storage - there will be some danger with any stored energy medium.

There are 5000 fires at gas stations in the US a year, and a few hundred battery fires, from what I can tell. And those battery fires include scooters etc... and seem like most of those are no-name / homemade / cheap / or damaged. Or some knucklehead hooks up a dangerously high amps charger to it.

Everybody charges phones, cordless tools, and laptops etc inside, which have the same kind of batteries, just in smaller capacities (~1/5 for a typical laptop, 1/3 for a cordless drill, but just as likely to have a fire from unsafe charging). Unless a battery is charged too fast from a charger defect (high current -> high heat), or the battery is defective, it will not go into thermal runaway (fire). A battery has to get to >200 degC either through too fast charging or a short (internal or external) to get there. There is a ton of R&D being done right now to learn about and eliminate the danger of thermal runaway.

I would suggest using reputable brand batteries, use the right charger, be careful with damaged batteries etc... i.e. use common sense

The car / bike / pedestrian safety issue is important. We had a biker, in the bike lane, killed recently by a drunk driver looking at their phone, at 4AM, the biker on the way to work. I haven't heard of any pedestrian injuries from bikes, but bikers absolutely should obey the rules-of-the-road (and watch out / yield to pedestrians).
On my route there is one place where the bike path crosses at a light, and cars rolling though the red light for a right turn routinely don't see bikes trying to cross on the green. There's a much bigger 'imbalance' between a car and a bike for potential harm than a pedestrian and a bike.

 

[JohnRoberts]

The battery is Li-ion. In my opinion the danger of these batteries is overblown (i.e. a status quo bias). The energy density of gasoline is 50 times higher than a current battery and extremely flammable - there's no free lunch with energy storage -

True but gasoline is a very mature energy source and well managed. I agree that people underestimate the energy content of gasoline (still cheap considering that). I wouldn't want to cut my yard with a hand push mower.

there will be some danger with any stored energy medium.

There are 5000 fires at gas stations in the US a year, and a few hundred battery fires, from what I can tell. And those battery fires include scooters etc... and seem like most of those are no-name / homemade / cheap / or damaged. Or some knucklehead hooks up a dangerously high amps charger to it.

Everybody charges phones, cordless tools, and laptops etc inside, which have the same kind of batteries, just in smaller capacities (~1/5 for a typical laptop, 1/3 for a cordless drill, but just as likely to have a fire from unsafe charging). Unless a battery is charged too fast from a charger defect (high current -> high heat), or the battery is defective, it will not go into thermal runaway (fire). A battery has to get to >200 degC either through too fast charging or a short (internal or external) to get there. There is a ton of R&D being done right now to learn about and eliminate the danger of thermal runaway.

Back a few decades ago my brother (the smart one) worked on advanced battery design in England for GE.. He has mentioned before that the battery design density, space between cells, affects their ability to manage/dissipate excess heat (a constant design tradeoff). Over the decades we've seen huge technology advancements in high temperature materials for loudspeaker voice coils. I am sure the battery guys are not asleep at the wheel.

I would suggest using reputable brand batteries, use the right charger, be careful with damaged batteries etc... i.e. use common sense

We could always use more common sense.

The car / bike / pedestrian safety issue is important. We had a biker, in the bike lane, killed recently by a drunk driver looking at their phone, at 4AM, the biker on the way to work. I haven't heard of any pedestrian injuries from bikes, but bikers absolutely should obey the rules-of-the-road (and watch out / yield to pedestrians).
On my route there is one place where the bike path crosses at a light, and cars rolling though the red light for a right turn routinely don't see bikes trying to cross on the green. There's a much bigger 'imbalance' between a car and a bike for potential harm than a pedestrian and a bike.

I experienced that routinely back when I was still riding my motorcycle, car drivers had the bad habit of not seeing you. It is made worse because motorcycles often drive much faster than the speed limit (at least I did) so even if they see you they underestimate the closing rate of speed. If I was riding my pedal bike at 4AM anywhere near traffic I'd have huge, bright, flashing lights front and back, but I don't so don't.

I get irritated when riding my bike and people in cars wave for me to cross in front of them.... NO THANK YOU... you go ahead, I can wait.

JR

JR

 

[dmp]

I wouldn't want to cut my yard with a hand push mower.

A few years ago I got a rechargable lawn mower and it is great. Never a problem starting it like a gas mower. You don't have old gas in the spring. No oil to change. Came with two 60v batteries - quiet - no fumes. Highly recommend them.
Gone a few years with no problems. My only worry is how many years the batteries will last. I wish these things would come with a 80% charge option too, to extend battery life, since I have a small yard.
My bosch power tool set needed new batteries a year ago and I did buy them, since I like the tool set, but they aren't cheap. I took them apart and they were 18650 li-ion cells, but buying the cells wasn't easy.

Still have the gas outboard boat motors though - probably not going to be replaced anytime soon by electric. Weight too important.

 

[JohnRoberts]

A few years ago I got a rechargable lawn mower and it is great. Never a problem starting it like a gas mower. You don't have old gas in the spring. No oil to change. Came with two 60v batteries - quiet - no fumes. Highly recommend them.
Gone a few years with no problems. My only worry is how many years the batteries will last. I wish these things would come with a 80% charge option too, to extend battery life, since I have a small yard.

I just gave away my old 22" 6.5HP mower to a friend with a small yard so he could cut it himself. I don't use it any more since I got a gas powered string trimmer (DoneRight). The doneright can cut down small saplings. I have a good battery powered string trimmer for small work. I bought a spare second battery because one doesn't have enough capacity for all my trim work. And the battery charger will not even recharge a hot battery.

My bosch power tool set needed new batteries a year ago and I did buy them, since I like the tool set, but they aren't cheap. I took them apart and they were 18650 li-ion cells, but buying the cells wasn't easy.

Still have the gas outboard boat motors though - probably not going to be replaced anytime soon by electric. Weight too important.

My 44" zero turn has 25HP and uses them. Battery is not ready to replace gas for that.

I am watching a move to promote battery power for huge farm machinery. I am not sure this is a good fit for how farm equipment is used.

Maybe somebody can perfect Nicolas Teslas wireless power distribution..

JR

 

[dmp]

My 44" zero turn has 25HP and uses them. Battery is not ready to replace gas for that.

Not sure why. Those riding mowers are already heavy (~800 lbs?). Would it be a problem if it were 10-20% heavier?
Electric cars have motors in that range HP and up.
My bike has 350w motor (0.5 HP). Mower would need a motor 50 times bigger to be 25 HP. Say you scale up the battery by the same factor of 50 (12.5kwh), battery would weigh 110 lbs, and would be able to power the motor at rated power for about 40 minutes (quick estimate, battery capacity divided by motor power).
Major advantage of gas engines now is power-to-weight, and that isn't going to change soon, with the high energy density of gasoline. Unless weight is critical, it can probably be replaced by battery electric.
Chainsaw? No way

 

[Matador]

A lot of lithium battery chargers are just dumb 42V / several amp constant voltage power supplies. I bet you could open it up and tweak a resistive voltage-divider ratio to move the float level down to 40V.

That being said, I don't see why a few diodes wouldn't work as well.

 

[JohnRoberts]

Not sure why. Those riding mowers are already heavy (~800 lbs?). Would it be a problem if it were 10-20% heavier?
Electric cars have motors in that range HP and up.

Certainly possible for my circa 1+ acre yard, but commercial grass cutters probably wouldn't care for charging time breaks mid day. For my yard, I wouldn't want any more weight. As it is, because I live on low ground this mower likes to get stuck in soft ground (mud) near my rain ditches. Over the years I purchased a come along hand winch and long ropes, to winch myself out of mud, every time I get stuck. I generally give my rain ditches a wide berth while cutting to avoid the soft dirt. The fat rear tires spin in the mud, and the relatively narrow self steering front tires, dig holes in the soft ground. Rocking forward and back just digs them in deeper.

Despite my years of experience avoiding mowing to close to the rain ditches, earlier this spring I got stuck in a new place where I never had trouble before... I had enough ropes to grab a tree in my side yard, even though I was stuck in the back yard.

Adding a few hundred pounds pf batteries, would just make it easier to get stuck, so no bueno. [edit- I forgot to mention, speaking about extra weight. I have never once filled up my gas tank higher than half full. The weight of an extra half tank of gas was avoided. [/edit]

My bike has 350w motor (0.5 HP). Mower would need a motor 50 times bigger to be 25 HP. Say you scale up the battery by the same factor of 50 (12.5kwh), battery would weigh 110 lbs, and would be able to power the motor at rated power for about 40 minutes (quick estimate, battery capacity divided by motor power).
Major advantage of gas engines now is power-to-weight, and that isn't going to change soon, with the high energy density of gasoline. Unless weight is critical, it can probably be replaced by battery electric.

power to weight matters

Chainsaw? No way

Actually I've seen some small battery powered chain saws that look interesting. I am not going to ditch my Stihl any time soon, but for trimming small branches a battery powered electric pole saw wouldn't suck. When I borrow my neighbors electric pole saw I have to string together multiple extension cords to reach even my front yard trees.

The phone line/utility power line guys use electric chainsaws (powered by the bucket truck electric system) for cutting tree limbs away from lines.

JR

 

[dmp]

A lot of lithium battery chargers are just dumb 42V / several amp constant voltage power supplies. I bet you could open it up and tweak a resistive voltage-divider ratio to move the float level down to 40V.

That being said, I don't see why a few diodes wouldn't work as well.

The problem is it is sealed plastic and I don't want to break it open.
I've seen in forums many of the chargers have a trim pot inside to set the shut off voltage. Might be simple if it were opened up. The trimmer could even be brought out to a dial.

The charger is current limited to provide 2A, and the voltage increases during the charge. Typically they taper the charge current when close to the voltage shutoff. When the voltage reaches the shutoff setpoint, it shuts off the current. So there is a comparator type circuit that needs to be modded.

Still not sure about the diode idea.

 

[Tubetec]

As I said previously , the power pack is just that ,the actual cell balance is done by charge management IC's inside the battery itself .
In RC its always a balanced charge not only is + and - connected but each cell junction is brought out in a jst mini plug with a corresponding number of pins depending on how many cells , the typical RC charger will allow so called dumb charge without the JST connected but take from me this is never ever a good idea .

I tell you what Mat , just to see the ferocity of the burn ,take a small single li-on cell ,charge it up and put it outside on a sheet of aluminum , rupture the the plastic or 'crow bar' the + and - terminals .ie a dead short, if you want put it on a long cable and intentionally over charge until it self destructs , either or which way your looking at a chemical fire that you basically cant put out . There are specific recomendations to charging li-po type cells , its very well worth getting aquainted with , take a cavalier attitude to this and you can end up doing serious damage . A couple of years ago in my town a person had an fault in their electric vehicle , instead of just abandoning the car where it was at the side of they road they parked up in a multistory car park and went shopping , the vehicle combusted , other vehicles caught fire along side it , the car itself burned right through steel re-inforced concrete a foot thick and cause further destruction on the floor below , the damage in the end was estimated at 8 million , who knows what it actually cost to fix the place , the entire shopping mall was shut down for six months and many businesses closed permantently .

My guess is adding diodes or dropping the input voltage wont make any difference , It might be possible with some cell charge controlers to program the in final cell voltage , check the battery itself for a USB diagnostics port .