Electric pedal bikes

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the1andonly
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Re: Electric pedal bikes

Post by the1andonly » Tue Sep 19, 2017 11:58 pm

Geof
Iv'e searched else where and talked to people I hoped would have a clue to find no sensible answer (that i understood) to this question
How do you charge these batteries off grid.
My simplistic view is to use 12v inverter to std 240v charger for the battery in question. Given your example what is a matched wattage for the inverter and how big a solar panel /additional battery purely for this requirement?
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Re: Electric pedal bikes

Post by g8dhe » Wed Sep 20, 2017 10:08 am

It does seem that is the only commercially available solution at present, I've had a check around myself and not found any 12 volt to 36 volt inverters with around 3-5 Amp capacity, I guess the demand just isn't high enough to warrant a solution. Rather like Laptop supplies there are only a couple of choices. However I suspect that they will start to appear as the demand is only going to go up, there is nothing at all special in the design needed and a 100 Watt panel would be more than adequate to do the charging a portable one that can be sun aligned would be a good choice however that assumes that you have good sunshine before/after riding for a few hours!
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Re: Electric pedal bikes

Post by Bob » Wed Sep 20, 2017 1:10 pm

Serious suggestion...

If you ride to a pub/cafe/other vsitor attraction it could be worth asking if you could plug in while you spend your dosh with them. :wink:

Worst you'll get is a , "No", but worth asking.
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Re: Electric pedal bikes

Post by g8dhe » Wed Sep 20, 2017 4:14 pm

Quite a few people do do this, take there power pack with them and plug in!
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Re: Electric pedal bikes

Post by fatcatlawyer » Thu Sep 21, 2017 4:10 pm

To charge wife's disability scooter batteries (24 volts) I use an inverter off a separate supply straight from the starter battery and plug in the charger to this. 4 hours driving to a destination usually puts enough energy in to fully charge them.
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Re: Electric pedal bikes

Post by mikeonb4c » Thu Sep 21, 2017 6:42 pm

fatcatlawyer wrote:To charge wife's disability scooter batteries (24 volts) I use an inverter off a separate supply straight from the starter battery and plug in the charger to this. 4 hours driving to a destination usually puts enough energy in to fully charge them.
Very interesting fcl. Suggests Bongo and ebike on the back for nipping to local shops etc could make a great combination
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Re: Electric pedal bikes

Post by fatcatlawyer » Thu Mar 21, 2019 12:10 am

Reserecting this 'cos I need some info. Wifey needed more power to have more FUN! So I bought a "wheelchair tractor", which put a big grin on her face. For those not in the know, these are like the front end of an ebike that clamps on to a wheelchair and in effect changes it to a trike with a motor. Makes it go much faster because it has 36 volts instead of the 24. All great in that way except when it comes to charging the thing when away from base.
I fitted a 140 watt solar panel in my naivety thinking that this would allow me to charge the battery on the scooter through my 500 watt inverter when we were parked up. When it is plugged in with the 42 volt charger (lithium ion nominal 36 volts need 42 apparently) the inverter bleeps and this is annoying!

I have seen on ebay a mppt controller for £36 that is able to be programmed to give out 42 volts. Would it be wasting the cash to get one of these and forget the inverter/charger that I have used for the old scooter batteries using the lithium charger supplied with the tractor unit. I have changed the old scooter batteries to in effect use them as leisure batteries and the solar panel charges them with no problems - and no BL°°dy bleepings . if I got a bigger inverter would this cope with the 42volt charger better, or should I be looking for a DC Transformer to up the voltage from 12 to 42 volts. It does seem to be wasteful taking 12 volts upping it up to 240 and then using the charger to bring it down again to 42.

When it comes to lectrickery I would normally get assistance from no1 son but he ain't speaking to me at the moment.

Solar panel today was giving a measured 22volts at the controller. This was within the parameters of the panel blurb!
Am I seeking rocking horse doo dar or is there a solution?
Ian Gl
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Re: Electric pedal bikes

Post by g8dhe » Thu Mar 21, 2019 9:56 am

Ian, as ever in these situations the system is a bit more complicated than it appears.
e-bike battery packs require a Battery Management System (BMS) these can either be built into the battery itself or maybe in the charger, these systems ensure that each individual cell gets the correct amount of charge rather than a common amount of charge to all cells. There is also some protection circuity built into the system again this may be in the charger or may be in the battery, things like a timer to prevent charging going on for ever etc. this is all to handle the rather more critical aspects of li-ion cells compared to lead acid batteries. Its therefore usually essential to use the provided charger to charge the battery. Its never going to be a case of applying an uncontrolled charger as you would use on a lead acid battery and allow the battery to control its own charging. This means its always going to be necessary to convert to mains voltages and use the supplied charger than use some combination of devices that comes to hand.
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Re: Electric pedal bikes

Post by fatcatlawyer » Thu Mar 21, 2019 7:50 pm

So..... It looks like that "answer" to my issue is a non starter. Back to the drawing board. My 500 watt inverter does not seem to have the power to force the charger into putting enough electricity into the e bike batteries but will a bigger inverter do this without the bleeps, which occur when the working light goes from green to red, signifying a non power situation.
If I get a more powerful inverter is that likely to behave the same way? If necessary we will have to stay at campsites and take up the use of EHU, but that was something I was hoping to avoid.
How much bigger would an inverter need to be. As we quite happily drive between 100 and 150 miles when touring a charger could used for
Several hours on a "driving" day. But of course I have my ebike as well as the scooter so two days driving to get one day riding may ultimately be the way.
Any ideas?
Yours Ian G
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Re: Electric pedal bikes

Post by g8dhe » Thu Mar 21, 2019 10:43 pm

My guess would be that the inverter is trying to pull too much current, the voltage drops too much from the battery/wiring and it shuts down. Most wiring inside a vehicle for the sockets will only be rated for 10 Amps - the limit for the sockets! That equates to 12v x 10Amps = 120 Watts trying to run inverters greater than that will require the inverter to be wired directly to the battery with an appropriate fuse and normally located close to the battery to minimise the distance, then run the mains output to where you need it.
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Re: Electric pedal bikes

Post by fatcatlawyer » Fri Mar 22, 2019 11:26 am

Success! The inverter does not now bleep if plugged into the cigar plug and the engine is running. Difference - I reduced the length of the input wires to the inverter to 10 inches. It made all the difference. I will now make up some short wires to see if that resolves the issue with the solar side of things.
I must say I was surprised that just shortening the wires would have such an effect. Thanks.
Ian G
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Re: Electric pedal bikes

Post by g8dhe » Fri Mar 22, 2019 11:35 am

You would do a lot better to bypass the socket altogether to be honest and wire direct to the battery, those connectors are awful for any significant current as the rear connector has no wiping action and any oxide /dust/dirt just gets pressed harder on to the metal plate at the rear :-(
There is an unused rubber grommet directly behind the glove box leading out to where the leisure battery is so quite a short route to the battery itself from inside.
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Re: Electric pedal bikes

Post by fatcatlawyer » Fri Mar 22, 2019 12:25 pm

Thanks again - now I have sorted the issue will consider the options. My diesel tank sits where the leisure battery goes (ideal for starting and finishing journeys) and my 70p per litre cooking oil goes into main tank. Thank you Mr. Tesco. And I get the points too.
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Re: Electric pedal bikes

Post by fatcatlawyer » Mon Mar 25, 2019 9:51 am

Final update!!!(I Hope) after more faffing got the inverter to work with my solar panel. Once I shortened the wires from the solar panel controller box all worked as I had originally intended and expected. I suspect I might be hoping for too much to get a second charger to work at the same time - But like they say hope springs eternal.
Ian G.
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