battery charger idea

Trevor R , sitting here with a good glass of red a thought came to me that susspension be it leaf /coil or any other form would not be a problem ,the alternator itself would have to be "mounted" not to the "body" but to the wheel hub ,the biggest problem is suspending such a weight from the hub as the rubber wheel would have to be in contact full time to be of any benefit.

Even better, leave the belt setup on the alternator, mount it to the chasis and run the belt via a spring loaded tensioner around another pully on the axel. That way the suspension could move up and down and the alternator could stay put.

Love it anyway, what a great idea!

A pulley on the axle would not be much good - it does not rotate. Try the brake drum.

PeterD

Oh yea of little faith ,with doubts such as yours the car you drive would be but a dream !!!!

I reckon for a vehicle that is running a fridge, running lights, charging a flat(ish) second in vehicle battery and running all the whiz bangery in the car, having a seperate alternator charging the trailer battery would take a lot of load off the main alternator and possibly charge the batteries faster. Also there would be no issues of voltage drop for charging the camper battery.

300w on the towing of the trailer?
I don't think you'd miss that cruising on the highway.

Why would an alternator need weather proofing? Mines covered in mud and get's dunked reguarly under the bonnet....

Don't most modern alternators have regulators built into them? If so, surely that would take care of the charge rate.

I reckon it's got potential.

Why would you want to switch it to charge off the vehicle?

Mike ,just for once think outside of the Square , do we realy have to believe that the energy used to drive the alternator is not already "paid "for thru just the fact of towing the trailer ,,get in behind with some of your expertise instead of the you can do this or that negativity usually on the forum ,,

>would take a lot of load off the main alternator

If your main alternator cannot cope with the extra load then you need a bigger alternator.

>300w on the towing of the trailer?
>I don't think you'd miss that cruising on the highway.

That's true, of course - I was just making the point that it isn't free energy.

>Don't most modern alternators have regulators built into them? If so,
>surely that would take care of the charge rate.

I'm not sure how they react to prolonged slow speed - it's not a situation they would expect to see for long periods; that's why I raised it as a query - a definitive answer would be good -anyone?

>Why would you want to switch it to charge off the vehicle?

Perhaps in the rain? When, I suspect, the drive will slip badly and you won't have any idea how much charge is going into the battery.

Mike Harding

3 x Batteries being charged at say 40 amps, headlights say 15 amps, ECU, stereo, laptop, GPS, Radio gear etc etc say 20amps, fridge say 5amps. (ok these are really rough off the top of my head).

40
+40
+40
+15
+20
=160 amps

How big is your alternator? Mines 70amps at high rev's on the specs, but it's 15 years old so would be barley putting anywhere near that I would think.

Alloy:

I have spent 30 years designing electrical/electronic/software products - not stuff you knock up in the back yard but often things, which if they fail, will result in the death of people or _even worse_ in our wealth obsessed world things which will loose people money if they fail! This experience has taught me that, almost, every man and his dog out there has a "brilliant idea" - like the guy who wanted me to design a control system for his hovercraft which was going to be used as a bird scarer (don't ask!) - as a hardened designer my first thought when I get a new "brilliant idea" (which is fairly often :) is take off the rose tinted glasses and _really_ look at what _might_ go wrong - because you can bet whatever might go wrong will go wrong - heard of Mr Murphy?

And don't tell me to "think outside the square" - that comment belongs on the back of a matchbox.

Mike Harding

Geoff:

I'm not sure what you're getting at - I doubt you will be putting 40A into any battery (even an AGM) for more than a few seconds/minutes before it's internal impedance rises enough to reduce the charge rate.

If your load requirements are more than your alternator can supply it will simply limit it's output at maximum, I assume???? You may destroy it - but I suspect the designers assumed people would try and do that and implemented protection circuitry?

If you _really_ want a second alternator why not drive it from the engine - it will be a much more efficient energy transfer than via a rubber wheel to the trailer axel and will behave in a more predictable manner?

Don't get me wrong: the axel thing will work - I just don't think it will work very well.

Mike Harding

Mike ,just for once ,its called "fun" ,,just for fun , bit like "rocket man " that just finished on the ABC , would it not be a worthwhile EO project whether it fails or makes a $m ,, for FUN.

Of course it’s fun and if you or the OP wish to pursue it then good on you and if you ask questions here I’ll offer all the help I’m able.

Mike Harding

The typical running current of a modern EFi engine is around the 25-30 amps mark. Add to that headlights 8 amps/100 watt, + another 10 amps for sundries (stop/tail/clearance lights), and you are looking at ~50 amps around town, and ~70 amps driving out of town (high beam + spotties).

Why not buy a Christies 55 amp battery charger and use it to charge the C/T battery while you are on the move (mounted in a box on the A frame). There is no known legislation that I know of that prevents you from running an engine in a trailer whiile it is on the move (semi's do this with their A/C units), especially as it is only a low voltage generator. An added bonus is it can be used when you stop, and can be used in an emergency to keep your main battery charged. Saves loooong cable runs and dealing with the voltage drop on them.

Not so faithful on the solar panels yet, they are pretty pricy for what they do so far. The charge cable you mention as does Nick R is the better way as long as the alternator is big enough to cope with the additional power demands we keep building in. The extra wiring and hardware like reguators could cause the costs to rise too.

The braking systems could be the innovation, but switching them to higher rates and back could be capital absorbing.

Good comments John - especially about regenerative braking.

However watch solar - there are new developments which may well produce _much_ more efficient panels over the next few years - unless essential I would hold off buying for at least a year or two.

Mike Harding

Mike, thanks.

I can see pretty strong braking force remembering what the magneto was like on the bike wheel Derek is talking about. Am so glad now to see LED take over and the power requirements shrink. What happens though when the battery is full? No braking?

Think some above are finding the interest without any practicality of the effort and result. The stones on camper trailers have a huge capability to cut out wires and pipes.

Solar panels are currently expensive for what they deliver, they are getting lighter and less fragile. I think they will form part of the skin of some campers in the future. Not yet though.

Not enough room on my camper for solar panels......the boat has gotta take precedence...

Marty my man, you are a genius.
This would really be the most feasible. I've been sitting here for quite a while using this as a mental excercise trying to work out a way of doing it.
You've given me a great thought.
I'd use Landcruiser hubs and stubs because the stubs are hollow and they have a full floating axle flange on the outside.
A shaft up the centre, it'd need some form of bearing on the end to a support a step up drive to the alternator.
As someone said above, the wheel rotates at a shade under 700rpm at I forget what road speed. At a wild eyed guess the alternator probably needs say 3,000rpm, The alternator speed would need confirmation.
I think it could be done!!
Heck, with Landcruiser hubs and stubs you could put an alternator in each wheel!!

Now, how do we make it into reality?

Geoff.

Or replacing the whole lot with an electrical braking device like in a towing dynamometer and then you can use electrical dynamic braking and charge when it's not braking.

We used to have towing dynamometers at holden for simulating loads that worked like this.

Unfortunately the added weight (lots of it) would definatel put the kybosh on this method.

Dave

Alternators are typically geared ~2:1 of the main engine pully so a more acceptable figure would be 6-7000 rpm. You would need a 10 x gear set off the wheel (at 600-700 rpm) to step up to the speed of the alternator, but this would create a lot of mechanical drag within the gears.

Use an IFS hub and use the CV half shaft as a flexible drive to the chassis for the alternator.

Hi Gary,
That would work too.
My thought with the above is the alernator could be hidden in behind the trailing arm of independent suspension on a camper offering it a measure of protection.

I've got no idea what I'd use for drive though. A belt does appeal as it's relatively more tolerant to dirt than gear or chain.

I've no idea if I'd attempt to build one! It's been reasonable excercise thinking about it!

Geoff.

That's OK for getting drive down to the ground, but trying to get the energy up from the ground without stopping the wheel or losing traction (pulling the trailer off track whilst driving) is the tricky bit.