Trailer charging?

[stevew]

What are the problems with a UK legal electric bike towing a trailer with one of these in it?
Key features | EU10I | Generators | Energy | Honda (UK)
Then you could plug it in to the charger whilst riding, or not, as the law demands ?!?!?!
Should increase the range somewhat.

 

[Synthman]

What would happen if the battery was being charged while powering the bike? Well I know that the discharge rate is much higher and it would eventually go flat, but would it cause harm or would it even work at all?

 

[flecc]

This question often crops up. Not legal if it's charging the battery that's in use, since it would effectively be a petrol electric hybrid and subject to motor vehicle regulations. It's impossible to determine that the generator power only supplied the battery anyway, though that's academic in this instance.

You could avoid motor vehicle regulations by charging a second battery in the trailer, though technically you would be breaching a little enforced law concerning manufacturing and commercial activities on the public highway.

 

[stevew]

Mmm, but just suppose the genny in the trailer was powering the bike's lights and there just happened to be some "spare" electricity!!
Now where could one put the "spare" electricity??

 

[flecc]

Either way Steve, it's impossible to prove that current from the generator is not reaching the motor directly, since the charging input to the battery is common to the current output. Indeed, the motor is preferred by the charge current, since it's input resistance is frequently lower than that of the battery. The two battery solution is the only one, swapping them over as each discharges, but still technically illegal.

 

[stevew]

Oh well, it was just a thought.
Seemed like a good idea at the time!
Looked like a great project to get my teeth into, but alas not to be.

 

[flecc]

Oh well, it was just a thought.
Seemed like a good idea at the time!
Looked like a great project to get my teeth into, but alas not to be.

Of course, given the weight of trailer and generator, plus the drag of the trailer tyres, the energy required for those could instead be used to carry substantial SLA batteries on the bike to get more range cheaply that way.

 

[mike killay]

I have often wondered about a trailer to carry lead acid batteries. The ones on my boat are 88ah and each weighs 19 kilos. Three of them in a trailer would give 36 volt 88ah. But, unlike Lipo etc, Peukerts law starts to interfere with expected power draw.

 

[flecc]

In fact all batteries suffer capacity loss with increased discharge rates. To demonstrate this, A to B magazine ran a series of test on a 36 volt 10 Ah lithium battery at various discharge rates, resulting in 10 Ah capacity at a very low rate down to 7 Ah at a high discharge rate, so 30% loss.

 

[Geebee]

flecc, that would be greatly affected by the chemistry and C rating of the Lithium battery, some of the newer LiPo¨s are getting rated capacity at discharge rates legal bikes will never see.

 

[flecc]

flecc, that would be greatly affected by the chemistry and C rating of the Lithium battery, some of the newer LiPo¨s are getting rated capacity at discharge rates legal bikes will never see.

That's true, but the principal remains, any battery has a discharge rate point at which it's nominal capacity starts to reduce. So far e-bike batteries don't perform to these very high capability levels, possibly in the interests of long life at prolonged discharge rates.