Caravan battery charging from wheels

[canis]

I recently read that caravan batteries generally only reach about 80% charge from the car. Giving this more consideration, a thought occured to me today. With self-propelled caravans being so common (i.e. a motor), why don't caravans charge their battery from their wheels (i.e. dynamo)?

I realise the motive power for caravan parking aren't designed to do this, and I realise attempting to utilse them in this way would be insanity.

Okay - forget the motors. But why don't they charge from an alternator or something coupled to a wheel? Either by belt of directly?

It's just an idea. But why not?

[ksmi]

Morning Canis, ref.charging caravan batteries,does any body use Solar panels? also any boat/barge owners 'on board'? what are the wind driven charging units all about?? could they be utilised for van use?

Sorry,more questions than answers, regards,Keith.

[nu11eaf]

Originally Posted by ksmi

Morning Canis, ref.charging caravan batteries,does any body use Solar panels? also any boat/barge owners 'on board'? what are the wind driven charging units all about?? could they be utilised for van use?

Sorry,more questions than answers, regards,Keith.

I have a 100 watt solar panel on my caravan roof that keeps my battery charged up all year round, When on sites and using my van we only use site electric, the battery is used for the motor mover for putting it in and out of storage or on my drive to pack things up and to postion on site.
While in storage the solar panel maintains the leisure battery charge, even through winter, and ensures it is charged for next time I need to hitch up with motor mover, the van is too big and heavy to pull by hand and not enough space to get car to the front to hitch up, and the leisure battery keeps the alarm/tracker battery topped up. Many new caravans now come with solar panel charging as standard.

[TonyB65]

It's a solution looking for a problem. My leisure battery holds a charge all winter and will still drive a motor-mover no problem. The only charging it gets is when it's hooked up to my car, or via electric hookup, or occasionally from a solar panel when there is no hookup. It simply doesn't need to be charged via the caravan itself. If you have a decent leisure battery charging from the van itself simply isn't required in my experience.

[green van man]

Originally Posted by TonyB65

It's a solution looking for a problem. My leisure battery holds a charge all winter and will still drive a motor-mover no problem. The only charging it gets is when it's hooked up to my car, or via electric hookup, or occasionally from a solar panel when there is no hookup. It simply doesn't need to be charged via the caravan itself. If you have a decent leisure battery charging from the van itself simply isn't required in my experience.

While I agree with most of what you say, last winter in the very cold weather my caravan battery was far less efficient and the load of the movers was evidently making it struggle.
I like to move the van during storage to help prevent pitting of the wheel bearings, just half a revolution makes a difference. Without a reffresher charge my van battery would not of lasted the winter. I have no solar panel and it's a case of self discharge over time, cold weather inefficiency combining to result in a van that will not move on the movers at the end of the winter.

Paul.

[TonyB65]

Originally Posted by green van man

While I agree with most of what you say, last winter in the very cold weather my caravan battery was far less efficient and the load of the movers was evidently making it struggle.
I like to move the van during storage to help prevent pitting of the wheel bearings, just half a revolution makes a difference. Without a reffresher charge my van battery would not of lasted the winter. I have no solar panel and it's a case of self discharge over time, cold weather inefficiency combining to result in a van that will not move on the movers at the end of the winter.

Paul.

Sure, your battery may be less than it was, but charging from the caravan wheels won't change that. I'm fortunate, we now have power points in the storage yard so if I really needed to I could charge from them, though I haven't had to yet.

[eternal optimist]

Originally Posted by canis

I recently read that caravan batteries generally only reach about 80% charge from the car.

I wonder if that's true or not. There ought to be enough 'headroom' in the car's charging system to top up a caravan's battery whilst the car's on the move. It's no different in reality to a split charge system used in a mobile home,

Originally Posted by canis

Giving this more consideration, a thought occured to me today. With self-propelled caravans being so common (i.e. a motor), why don't caravans charge their battery from their wheels (i.e. dynamo)?

I realise the motive power for caravan parking aren't designed to do this, and I realise attempting to utilse them in this way would be insanity.

Okay - forget the motors. But why don't they charge from an alternator or something coupled to a wheel? Either by belt of directly?

It's just an idea. But why not?

The energy wouldn't come for 'free'; the additional drag created by the alternator in charging the battery would have to be paid for in diesel/petrol by the car dragging the caravan in the first place; in addition to the cost of the alternator and control gear on the caravan.

[37 RUBY]

Hey Canis

That's not as crazy as you think.

Picture the old hub dynamo's on old pedal cycles.

If the caravan wheel hubs/brake back plates were to incorporate similar.

....but then think about the fact there has to be a electrical link between car and caravan for lighting anyway making separate charging unnecessary.

Unless we make the vehicle to caravan lighting link wireless ...look what you've started

As for the 80% charge theory, my caravan battery always shows full after being towed. Maybe that's down to the quality of my car charging system

Hello Ksmi,

Yes solar panels are already fitted to many a current caravan model but as a rule they only maintain the battery at its last charged level.

...as for your wind turbine thought. What about harnessing energy from the free spinning vents you see on RSPCA van roofs...

So many ideas but then when I think about how the uk caravan industry is hell bent on building leaky lightweight vans then the less electrics inside the better.

[canis]

Originally Posted by eternal optimist

I wonder if that's true or not. There ought to be enough 'headroom' in the car's charging system to top up a caravan's battery whilst the car's on the move. It's no different in reality to a split charge system used in a mobile home

I think it's down to the length of wire, the wire has impedance, so the available voltage at the caravan end is lower. Too low to reach a full charge, although I'll accept that with a large enough battery 80% would be quite useable.

Having said that, the source was an online webpage whose description of ohms law and wire impedance was true but their javascript calculator was wildly inaccurate, and made me look a complete @rse when I quoted it. Their maths might be rubbish, but the idea is sound; Longer wire means more impedance overall, more impedance means less volts. I think. :-/

Originally Posted by eternal optimist

The energy wouldn't come for 'free'; the additional drag created by the alternator in charging the battery would have to be paid for in diesel/petrol by the car dragging the caravan in the first place; in addition to the cost of the alternator and control gear on the caravan.

Haha! You're quite right, energy is not free. But the energy has to be paid for in fuel no matter how it gets there, and you'd be suprised how much drag an alternator working hard puts on an engine. I've no figures on the subject, but you've probably noticed the tick-over speed drop when you couple a flat battery by jump leads.

Originally Posted by ksmi

does any body use Solar panels?

A lot of people use solar these days. It's still rather expensive to cover a van roof, and out of my lowly budget, but it's certainly cheaper than it used to be. I would imagine on a sunny summer holiday solar would give a significant boost to a battery.

Originally Posted by 37 RUBY

So many ideas but then when I think about how the uk caravan industry is hell bent on building leaky lightweight vans then the less electrics inside the better.

Yes, they do seem to emply a strange construction method, which leads me to my next question; Why don't them make them out of ABS?

Erm, anyone want to go into business with me? I've suddenly become the next Dyson, sort of, HAHA!

[HDAV]

KERS for caravans.......

12v systems do suffer volt drop, but is the battery capable of being charged past 80%?

Solar is great and getting cheaper £50 now buys a decent solar panel that will top up a battery and a £200 array would keep a camper happy.

Wind again is great but would need to be set up each time. More safety concerns than solar too. Parking up for a long time would keep a battery topped up if the conditions were right.