Question for Electrical Gurus

[S D]

Is it possible to charge a bike from an invertor via a car battery?
Specifically the focus Jam .
We have no 240v in the garage.

 

[Zimmerframe]

Yes, but you'll go a long way to flattening your car battery in the process.. presumably you can't remove the battery or you'd already do that ..

 

[Maxb]

Is it possible to charge a bike from an invertor via a car battery?
Specifically the focus Jam .
We have no 240v in the garage.

Yes it's possible with a sine wave inveter you will need a large lesuire type battery if your battery is big enough you may get a couple of charges out of the battery..

 

[Dax]

Take battery out and charge in house?

 

[S D]

Take battery out and charge in house?

Not possible on the Jam without motor removal unfortunately.

 

[Swissrob]

Is it possible to charge a bike from an invertor via a car battery?
Specifically the focus Jam .
We have no 240v in the garage.

WTF, you keep your bike in the garage, that's what lounge rooms are for! ?

 

[Dax]

Run power out to your garage?

You will monster through a leisure battery charging a bike, and carrying it into the house to charge will be hassle. For a few hundred quid you could buy a few leisure batteries, wire them in parallel, and fit a couple of solar panels on the roof with a mppt controller. Has the advantage you could fit some 12v led lights for your garage too.

 

[Swissrob]

Is it possible to charge a bike from an invertor via a car battery?
Specifically the focus Jam .
We have no 240v in the garage.

Worth looking at a portable solar panel and inverter so you can charge it if you're camping.

 

[S D]

Run power out to your garage?

You will monster through a leisure battery charging a bike, and carrying it into the house to charge will be hassle. For a few hundred quid you could buy a few leisure batteries, wire them in parallel, and fit a couple of solar panels on the roof with a mppt controller. Has the advantage you could fit some 12v led lights for your garage too.

Neither option is feasible unfortunately as the garage in question is a communal one underground an apartment block .
We do keep a car in there hence the thought of an invertor from the battery.
I didn’t realise charging a 378w ebike Battery would be so demanding power wise.

 

[aarfeldt]

I use a small Honda generator, when I don't have 230v access.
Very usefull and can be moved, when you're travelling.

 

[Mikerb]

There must be power in the garage for lighting etc. May be feasible to ask the landlord for a metered spur?

 

[aarfeldt]

bikes should generate their own power when braking and using suspension travel...just saying.

 

[Mikerb]

bikes should generate their own power when braking and using suspension travel...just saying.

Braking regen at best delivers 5% extra range on an e bike and it means the motor needs to be gearless direct drive.....so no freewheel! Thats why it is not a feature of mid drive e bikes.

 

[aarfeldt]

Braking regen at best delivers 5% extra range on an e bike and it means the motor needs to be gearless direct drive.....so no freewheel! Thats why it is not a feature of mid drive e bikes.

Braking (discs) has nothing to do with the engine.

I think you mean engine-braking.

 

[jerry]

bikes should generate their own power when braking and using suspension travel...just saying.

Yes, I agree! And power is free anyway, just wire a lamp to a solar panel, and presto... infinite free light and power!

 

[Zimmerframe]

Braking (discs) has nothing to do with the engine.

I think you mean engine-braking.

What Mikerb is saying, is that in order for the bike to also recuperate the energy stored in the moving bike, is that the bike would have to have a motor which is also configured so it can also act as a generator.

So the motor would always need to be turning, if it was a mid motor, then the chain would also always need to be moving to turn the motor, otherwise you can't extract the energy. So you would always have all the extra drag of the motor and its internal gearing turning even when you stop pedalling. If you didn't do it like that, you'd also need some form of clutch mechanism to override the freewheel and spin the chain/motor up when you want to brake - which adds more complexity.

The Brake lever would then need to be more complicated and act as a switch for the regen and a lever for the disks. When you first press it, it would engage the "generator", charging the battery and slowing the bike. As you press more, it would need to engage the brakes so you stop or slow down as required.

This sounds like a fantastic idea, but in reality because a bike and rider don't weigh that much compared to a car and aren't really going that fast, plus the energy losses due to inefficiency of conversion, you don't actually get much energy back.

Most bikes which offer re-gen, have hub motors, these are spinning all the time anyway with the wheel, so are much more efficient and simple to configure for regeneration.

On my bike I've attached a second hand formula 1 Kers flywheel system. It only weighs 24kg's and fits nicely in the frame. At the start of a downhill run I attach a hook to a tree which is connected to a 200m titanium cable which is wound round the kers flywheel. As I descend, the rope unwinds and spins up the flywheel. After about 200 meters the flywheel is normally upto it's maximum 64,000 rpm. When I reach the bottom I engage a mechanism which uses this energy through a small gearbox to drive the chain and take me almost back upto the top rather than using the battery. Once the flywheel is upto speed it acts like a massive gyroscope. I'm not sure if you ever played with a gyroscope, but once they're spinning they don't like to move. So this has the positive effect that it's completely impossible to knock the bike over (you can actually get off and it just stays upright, which is great for photos, no need for a stick), but it also has the negative effect that it's impossible to change direction so I can only take the straight "Strava" lines down a run.

 

[Zimmerframe]

At the start of a downhill run I attach a hook to a tree which is connected to a 200m titanium cable which is wound round the kers flywheel.

I know what you're thinking, that whole thing is preposterous ! Who's going to make all that when you have to go back to collect and wind up your cable each time. Well yes, that wasn't the plan. Unfortunately, Batman bought up the whole 2019 production run of carbon cellulose nano filament with a 5 minute decomposition time - for his stupid powered grappling hooks. You try getting some of that back off him ..

Zimmer : Knocks on bat cave door ..
Batman : "Alright Zim"
Zimmer : "Hi Batty, can you thank Alfred again for that pickup in the woods last week when I ran my battery flat, cool .. So hows the new Decoy ?"
Batman : "I'm pissed Zim, it's still not here, they said I could have it in titan silver and fallout yellow, but that's no good is it"
Zimmer : "Victims of their own success I think. Custom Matt Carbon mate, that's the only colour for you. Don't they know who you are ?"
Batman : "Should do, put my name in as D.Knight"
Zimmer : "Ah crap Batty, they probably think you're called Darren or Dennis or something, you had the same problem last year with Amazon didn't you ?"
Batman : "Na, that was fedex, couldn't find the cave because it's not signed"
Zimmer : "Superhero problems Batty, Superhero problems. Anyway, don't suppose you can spare some of that 200m carbon cellulose nano fillament can you"
Batman : "Soz Zim. Need it"
Zimmer : "But you've got like 1000km's of the stuff ?"
Batman : "Hate stairs mate, the fellas downstairs get really sweaty with all the gear on and doc says I need to keep em cool"
Zimmer : "ok dude, well gimme a call when the YT comes."

 

[Mikerb]

Braking (discs) has nothing to do with the engine.

I think you mean engine-braking.

How would it work just with discs?

 

[aarfeldt]

How would it work just with discs?

It would work great

I'm sure that breaking power can generate electrical power also (with different components ofcourse)
The suspension travel can also generate electrical power.

It's the future...just like eMTB is
Just like a hybrid car....but very lighter/smaller/better.

 

[Zimmerframe]

I'm sure that breaking power can generate electrical power also (with different components ofcourse)
The suspension travel can also generate electrical power.

Unfortunately, as has been proven many times, global scientific advancement has been pretty much stagnant ever since the invention of the Mountain Bike and Internet Pornography. Both of which incidentally were created in the same week by the same man with the sole aim of creating a global scientific slow down !! Now the brighter minds amongst us would rather go out on their own and have fun or stay in on their own and have fun ....

This is clear to see when you compare where we are now to what was shown on the famous 1985 documentary "Back to the Future" by Robert Zemeckis . Even then a car was shown to be powered by a simple, small and compact "Mr Fusion" which created power just from waste - yet it never came to market !

So yes, whilst power can be created from heat with a thermo electric generator, unfortunately they're still not small enough and efficient enough to glue to your caliper and re-charge your battery.

 

[Mikerb]

Energy has many forms....heat being the lowest order. Kinetic is more efficient but relies on mass and a bike plus rider does not have much mass. Assuming ylu want a braking system that ca stop you in a few metres there is also precious little braking time other than when you are riding your brakes all the way down a steep trail. The normal way to generate power from braking is to turn the traction motor into a generator but if you want to just use a disc brake it would have to be mounted on a generator.....in which case it is the wheel that is actually driving the generator. Meanwhile the only braking you are getting is via that generator....eek!! So now you need another brake.....buy if you use that brake you reduce the power produced by the disc with generator on it. So you see...a lot of faff for marginal gains.

 

[aarfeldt]

I think you think too narrow

You know what you know...but not what will be invented tomorrow out of the blue.
Just like the tablet....suddently it was there with absolutely no need.

eMTB is a great platform for developments...just lets see how smart our bikes will be in a few years.

 

[Zimmerframe]

I think you think too narrow

You know what you know...but not what will be invented tomorrow out of the blue.
Just like the tablet....suddently it was there with absolutely no need.

eMTB is a great platform for developments...just lets see how smart our bikes will be in a few years.

No one disagrees with you. It would be great if these things existed now .. in the future maybe. For now, if you look at a dynamo for your bike to run a light, it's big, heavy, inefficient and just runs a little light. That's nothing compared to the power needed to re-charge the battery to power the motor.

 

[Zimmerframe]

Is it possible to charge a bike from an invertor via a car battery?
Specifically the focus Jam .
We have no 240v in the garage.

I was hoping with all the "bumps" the thread would have attracted the brighter minds to come up with a cool solution for you ... unfortunately they must all be out on their bikes or have their hands full .... So I'll have to stop being a knob for 5 minutes and try ...

So, ok, yes, you could charge it from your car using an inverter. You just run the risk of flattening the car battery, which does the battery no good and means you can't start the car. You probably have more chance if it's a diesel as the battery is normally bigger to provide the extra ooomp to turn a higher compression diesel engine. You'd need to check what the capacity of the car battery is before you start and compare that to your bike. Your focus battery is 10.5 ah and you'll use more than that to charge it due to energy loss with the inverter and the transformer for the charger.

So you could try it, but buy a jump start unit as backup incase you need to jump the car . like :


If you were doing it long term, you could setup a second leisure battery in the boot and have that added to your charging circuit as you would on a motorhome or similar - then you could use that battery without fear of flattening and damaging your main battery.

 

[Zimmerframe]

I know it's not what the OP asked, but the "self charging" suggested by @aarfeldt was also discussed with more detail and less sillyness (guilty) on new years day by wise men with hangovers and sleep deprivation.

Self charging technology - EMTB Forums

 

[S D]

L

Worth looking at a portable solar panel and inverter so you can charge it if you're camping.

charging from the van when camping is

I was hoping with all the "bumps" the thread would have attracted the brighter minds to come up with a cool solution for you ... unfortunately they must all be out on their bikes or have their hands full .... So I'll have to stop being a knob for 5 minutes and try ...

So, ok, yes, you could charge it from your car using an inverter. You just run the risk of flattening the car battery, which does the battery no good and means you can't start the car. You probably have more chance if it's a diesel as the battery is normally bigger to provide the extra ooomp to turn a higher compression diesel engine. You'd need to check what the capacity of the car battery is before you start and compare that to your bike. Your focus battery is 10.5 ah and you'll use more than that to charge it due to energy loss with the inverter and the transformer for the charger.

So you could try it, but buy a jump start unit as backup incase you need to jump the car . like :


If you were doing it long term, you could setup a second leisure battery in the boot and have that added to your charging circuit as you would on a motorhome or similar - then you could use that battery without fear of flattening and damaging your main battery.

ive wired a few splitchargers in the past and have more than a few spare batteries lying around so this is s good suggestion .
All I really needed to know is how many amp hours the battery will need to be to charge a 378w battery on the focus.

 

[Zimmerframe]

Your focus battery is 10.5 ah

So give yourself a margin over that for energy loss in conversion , say 20%,through the inverter and transformer and you should have a rough idea of which of your batteries is suitable for a couple of charges.

It's a shame focus don't sell a 12v charger as you're converting 12v DC to 220v AC back to low voltage DC ? so lots of wasted energy to heat.

 

[S D]

So give yourself a margin over that for energy loss in conversion , say 20%,through the inverter and transformer and you should have a rough idea of which of your batteries is suitable for a couple of charges.

It's a shame focus don't sell a 12v charger as you're converting 12v DC to 220v AC back to low voltage DC ? so lots of wasted energy to heat.

That’s what I thought, it would make things easier for sure.
Thanks for the advice

 

[Mikerb]

Seems to me the easiest and fastest way to charge the battery off grid is with a suitcase generator.

 

[Zimmerframe]

Seems to me the easiest and fastest way to charge the battery off grid is with a suitcase generator.

It is .... But ... in this instance I'm guessing the OP doesn't want to leave a noisy generator running in a closed and unventilated garage for 5 hours ... not unless he's running a pay by the hour alcohol free hangover service on the side.