kesh posted:

Matt. We have a remote work camp, often nearly 2 weeks between use of the vehicle. On board is a 60l. Trailblaza which is used purely as a freezer.
About 12 yrs. ago (when we bought the Trailblaza) I made up a battery charger using a 4.5hp. Honda engine v belt driving a Denso 12v. alternator. This is the old external regulator type and I use a Bosch re 55 electronic regulator for control.
Have both voltmeter and ammeter wired in and as the battery charge comes up I can regulate the engine speed down for economy. The unit puts out about 45a @ 14.8v. (depending on residual charge in battery) until the regulator starts to bring the current down. About 4-5l.petrol/wk. keeps all batteries fully charged. Runs about 1 - 1.5hrs./day.

There is no way this would double as a welder. I have a Lincoln welder/generator (5kva @240v./180a.) and even running a 12g. rod makes the 11hp. engine work. I think if you need to run a welder a 240v./3.5kva generator would be min. to power it or failing that there are good diesel units available on eBay.
kesh

disco driver posted:

Hi Rus,
Not that many years ago, but yes I can remember them too,
They were known as "Auto-Arc" and were a modified Bosch Alternator with some extra electronics added. Never owned one but used one belonging to mechanic mate to weld up broken spring mount on my old 1962 Series 2 L/Rover SWB.
He had it fitted to his Series 2A service van.
Try googling and who knows what you may turn up.

Probably not compatible with all the computers etc on the modern 4WD.

Disco

Mike Harding posted:

>the best electric motor for the job is the Fisher and Paykel washing
>machine motor, there are plans for using it on the web. Eric.

Sounds fascinating, I love re-using stuff like that - any links Eric?

Eric Experience. posted:

Mike.
WWW.ecoinn.co.nz
Eric

Gu_Patrol posted:

How about using a 24volt alt and have it independently working from your vehicle.

I know guys that have welded from a 12 volt battery, 2 x 12 volt (24volt is better) you know the welding kit you buy that clamps onto your battery the battery won't last long, but enough for some welding to get you out of trouble

Eric Experience. posted:

Gu.
The voltage is not the problem with welding it is the current, a 12volt alternator has thicker winding than a 24 volt so can handle the current better. If you run a 12volt unit at high revs without a regulator you can get about 400volts obviosly the diodes wont take the voltage so you end up with a lot of smoke but if you build a special reg that is set to about 30volts and you use suitable doides you can weld ok but you have to have a very good belt drive, a normal v belt will not last long. Eric.

Gu_Patrol posted:

OK :-)

mjf191 posted:

Thanks to all who offered advice much appreciated,
I think the welder option has hit the scrap heap, I'll still be building the charger though. For the moment I'm gauging my plans off the larger 3hp 80amp christie charger, since my engine is 3.5hp should be enough for 80-90 amp alternator.
I have some more questions
1. I have read on another forum that alternators can't fully charge a battery without a 3 stage regulator, is this true do I need to replace the normal internal regulator to get a full charge.
2. What would be the best voltage protection. Would a circuit breaker be suffice?
3. I already have a 0-20 volts gauge would it be best to have an Amp gauge also & how much would a gauge suitable for high amps cost? (I'm working to a budget)
4. How would be the best way to make charge output adjustable, a switch or revs?
Any info appreciated
cheers
Matt

MartyB posted:

Matt,
A friend of mine has a similar setup. One problem he said with his is the analogue gauges for volts & amps. The motor vibrations cause the needles to vibrate making the gauges inaccurate. You would be a lot off fitting digital meters. Oatley electronics have a kit for a digital meter.
www.oatleyelectronics.com/kits/k212.html

from Marty.

Mike Harding posted:

>I have read on another forum that alternators can't fully charge
>a battery without a 3 stage regulator, is this true

No. Providing the alternator can supply current at a loaded voltage of about 14.4V then the battery will, in time, reach full charge. Three (or more) stage chargers just use some electronics to charge the battery in the minimum possible time and they also may extend battery life by minimising overcharge and performing an equalisation process on the cells.

>do I need to replace the normal internal regulator to get a full
>charge.

I very much doubt it.

>What would be the best voltage protection. Would a circuit breaker
>be suffice?

Why do you want “voltage protection” and what do you mean by that? A circuit breaker will open if the current through it exceed a given threshold for a given time – I doubt one would be a lot of use in your case – an appropriate size fuse would be simpler and cheaper.

>I already have a 0-20 volts gauge would it be best to have an
>Amp gauge also

Always a useful tool in battery charging – I would put one in.

>& how much would a gauge suitable for high amps cost?

Jaycar do a 100A current shunt for $20 – part number QP5414 and you’ll need a moving coil meter for about $18 to go with it. If you don’t know how to make an ammeter from those two parts drop me an e-mail and I’ll help.

>How would be the best way to make charge output adjustable,
>a switch or revs?

Why do you want to do this? Won’t the regulator on the alternator take care of charge rate?

Someone else suggested digital meters – ho hum… a digital meter is good if you are looking for very accurate readings but it won’t show a trend or peaks because it integrates it’s input data. For your application I would prefer analogue meters (ie. moving needle type) but they do need to be kept away from vibration.

Mike Harding

mike_harding@fastmail.fm

Eric Experience. posted:

Matt.
As mentioned above, the automotive alternator will only give you 500 watts from a 3.5 hp motor, so the amps will be 500/15 a bit over 30 amps. the company that sells a unit with a 55 amp alternator on a 3hp motor implies it can produce 55 amps but it can not, it will produce about 20 amps at max revs, you dont want to run a max revs or you will annoy everbody and wear out you motor. If you use an alternator that is to big for the motor the motor will simply stall under load. it is better to use a small alternator so the motor is not overloaded, a 40 amp unit is best and lighter. Eric.

Member - Ed. C. posted:

Ditto....
I've had to do the odd bit of track-side welding, and IMO (and in my experience), 36v will give a smoother arc than 24v... This will no doubt depend on the electrodes used, but it appears that most of the commonly available ones are meant to be used at a MIN. of 45volts (open circuit), though they will work ok on 36v....
I definitely prefer to use 3 batteries (36v) if they are available...
And yes, as mentioned, one can do quite a bit of welding with surprisingly little effect on battery capacity...