Cycling UK Forum

My friend has a motorhome with a 9 volt output if he buys an electric bike is it possible to charge his bike battery from this source?

9 volt, are you sure?

Most motorhomes have 12 volt leisure batteries and 240 volt if on mains hook up.

Ebike chargers are 240v supply, so no.

Hi,
12 Volt to mains inverter.

Could you use something like this https://www.mdsbattery.co.uk/optimate-d ... arger.html
What voltage is an Ebike?

Yes but it may not be easy.

1:- Motorhome battery -> Inverter for 240v -> standard mains charger -> E-bike battery.
The chain of devices will be probably be horribly inefficient.
Even if each step is 80% efficient, only 50% of the power drawn out of one battery ends up in the other.
In the very worst case where there's already a fairly high draw on the motorhome battery, it may be do you get a full e-bike battery before the motorhome battery goes flat.

2:- Motorhome battery -> dc/dc converter for the correct voltage to charge -> e-bike battery.
Much better efficiency but you'll be dumb charging the battery with all the risks.
You may well kill the battery life without a smart charger.
So you really need to find/make a smart charger that will run off the motorhome battery for maximum efficiency and battery life.

The other question is how will your friend keep the motorhome's battery charged ??

No longer have a motorhome but just acquired an e-bike. I would only consider charging from the motorhome when connected to a mains hookup at a campsite as even ordinary domestic use runs the battery down fairly quickly (Unless there is better technology now).

The OP hasn't come back. Nonetheless, I suspect the owner of the M'home will know what's what.

He will know the limitations of his leisure battery(ies) and like most m'homers he will guard it against too much discharging. He will also know that once on mains power, he has pretty much a free hand within the limits of the hook up.

Of course he could be an off the grid sort of person and have a massive bank of batteries, but again he will know his limitations.

Currently charging my batteries for a weekend away. I run a fridge off it so in hot weather every amp is valuable. I will be pedalling my non electric bike.

Thanks for all your help . Very useful

Just arrived at my campsite. I always prearrange with manager/proprietor in advance and never a problem plugging in at office. This time just the same. 40 miles and just over half my power used. Couple of hours and will be fully charged again.

hemo wrote:Ebike chargers are 240v supply, so no.

Yes, of course. His motorhome probaby has mains electrics, which will include internal 13amp sockets, so as long as he's on a pitch with electric hookups he can charge the e-bike battery - obviolsy as ong as he doesn't exeed the current available from the hookup (which he might if he has mains telly, cooking, heating etc. all on at the same time!)

Hi,
I normally carry four batteries on the motor home, one main and three auxiliary batts.
One for the TV, one for the camper lights fan boiler heater etc etc, the flushing loo, one for the dog fan to keep the boys cool.
That way you can always start the engine.

As said tap into the DC side of the ebike charger gubbins if you want to charge off a dc supply, minimal loss.

I only ever charge our ebike from an inverter. Its a 3KW Outback, and it is run from a 24V battery bank that is charged from solar panels on the roof.

I cant see why any motorhome with panels, a leisure battery and good modern pure sinewave (i think they all are nowadays) 240V inverter would be a bad power source for charging an ebike.

Unless youve got to start the engine to charge the leisure battery. That would just be stupid.

Lithium ebike batteries come in 24V, 36V and 48V flavours. Mine is 36V and the mains charger that came with it is marked as giving an output of rectified 42V 2.0A DC. It also has an LED which shows red when charging and green when charged. If you plug the battery (part or fully charged) into the charger when the charger is not plugged into the wall, or plug the charger into the wall with no battery connected, the LED shows green.
Hope that helps...