Alternator help please

[tineca]

Hi folks. Not about my car but still one I hope you can help with. My mum and dad have a caravan they use at weekends and it's permantly sited in a farmers field .dad is 82 now and lugging batteries is getting a bit much. (There is no electric hook up). I am making them a 12v generator to give the battery a bit of a boost. I have connected a mower engine to an alternator but not getting a reading. Have a look below






in my mind I though the large spade connector would be the live output and the smaller spade would be the negative. With the engine spinning the alternator fast, I am not getting a reading. Can someone help me? Cheers Jed

[v8ian]

I think there needs to be an exciter attached. not always obvious, Google the type of alternator and just ask "wiring for XYZ alternator"

[Dez]

it has to be wired through a no-charge waring light for it to work. depending on the type of alternator, this can be live or earthed.

[bortaf]

Usually the large terminals are live, the body of the alt is the earth and you need a 12V feed to the small terminal to get the thing to charge but as ian says goole that alt as some J stuff is wiered differantly.

[tineca]

Cheers guys. So if I put a battery on it and take a live to the small spade next to the two larger spade and run the earth from the battery to the housing will I get a charge? It's off an escort 1.4 apparently.

[tineca]

Looks like it's this one. czyinghua.en.alibaba.com/product/396879197-209448542/Lucas_Alternator_1_3118_01LU_CA305IR_Used_On_Ford_Escort.html

[composimmonite]

You need a battery to excite the field coils to then get any output. That means either adding a small (motorbike size ?) battery or the one you want to charge.

A lot easier is look for a Honda ED400 generator. I bought one a few weeks ago for £50 and brilliant. It's a battery charging unit so only supplies 12v & 24v and not 240v. Starts first pull every time and is quiet.

Paul H

[tineca]

Cheers. Can you just give me a little bit of advice on the wiring?

[chairchild]

fit the two large terminals to the 12v+ on a battery, and the smaller terminal through a small bulb (1-2w) and a feed from the battery

Should also be able to use the stud on the right, which has the flanged nut on, as the positive too Still need the wire up the indicator light though


Nice job on the little generator btw

[Good Scrap]

The two big terminals are an output pair and joined together in the casing, the small one is the warning lamp and excitation.

Put a loop of wire via a 12v bulb from the big two terminals to the little terminal, I suggest only start the engine after connecting the battery.

It will initially illuminate the light before starting then go out once running and charging.

[MrSpeedy]

That looks like a bog standard Lucas A127 style alternator.

The two large spade terminals are common and should be connected to the +ve of a battery

The larger of the two studs sticking out the back should also be common to the large spades, but check. There will be something cast into the body to identify it usually, a 'D+'
The smaller stud should be marked 'W'
The frame is -ve

The alternator is not 'self exciting' though, and will need a 12v feed through a warning light of 2.2watts, connected to the small spade terminal, to excite the alternator for it to charge.

Incidently, I can get hold of similar alternators that have the exact same mountings, but are self exciting (no warning light wire)







*Edit - beaten by GoodScrap*

[1eighteen]

Just a thought here. But I assume your parents drive to their caravan in a car ? So they already have a charging system.

Why not fit a split charging system to their car with a battery manager to monitor the car battery voltage so when it goes below 12v it cuts out the auxiliary battery. Fit an Anderson connector so it's got an easy hook up for your dad.

Or get them 3 or 4 12v batteries and wire them together in parallel, so they still get 12v, but 4 x the amp/hr.

[chairchild]

Jul 4, 2014 17:21:58 GMT 1eighteen said:

Or get them 3 or 4 12v batteries and wire them together in parallel, so they still get 12v, but 4 x the amp/hr.

But, they'd also be trying to charge each other - to the tune of a good few amps each. So the Ah rating would be diminished by quite a large chunk.

[MrSpeedy]

Jul 4, 2014 17:21:58 GMT 1eighteen said:

Just a thought here. But I assume your parents drive to their caravan in a car ? So they already have a charging system.

Why not fit a split charging system to their car with a battery manager to monitor the car battery voltage so when it goes below 12v it cuts out the auxiliary battery. Fit an Anderson connector so it's got an easy hook up for your dad.

Or get them 3 or 4 12v batteries and wire them together in parallel, so they still get 12v, but 4 x the amp/hr.

Doesn't quite work like that. Trust me, I come across this daily on narrowboats where we typically have 400 amp/hr + leisure capacity and 75 - 90 amp/hr engine battery.

Not to mention that 4 times capacity means 4 times the charging time, and if the alternator isn't of a suitable size the batteries won't be charged properly and will not last as long as they should.

The most simple solution for what you're proposing is either an ignition controlled split charge relay (not great) or a split charge blocking diode.

Both will charge auxiliary batteries without compromising the engine battery.
You would obviously have to swap the batteries from the car to the caravan and you still have no way of recharging them without running the car. Leaving an engine idling for extended periods of time does not do them any good. Especially modern Diesels

[tineca]

Thanks folks. Really useful. Will do exactly what you said with the wires. I did consider mounting a battery in the boot of dads S60 and doing the split charge relay. It's would be okay as the start battery is already in the boot. I was worried it would not boost much on tick over and also it's a 2.4 petrol so a little thirsty. Hopefully I can get this sorted now. I have enjoyed making the trolley and picking up the old easy start mower engine. Will let you know how I go on. Thanks again Jef

[omega]

while I admire you skill I think it would be much easier to buy a genny and a lot less messing about for your dad.

[tineca]

I' ve got a honda genny but it's low amps on the 12v charge. It would take a long time to charge the batteries, I am hoping 1/2 hour at full chat will see it charged. Not sure about skill mate, it's just a bit of tinkering. Ha ha

[taurus]

I admire the ingenuity, but personally I'd look at either solar or wind generators. Not as much fun of course but they work very well for this kind of thing.

[dodgerover]

Jul 4, 2014 22:41:01 GMT tineca said:

I' ve got a honda genny but it's low amps on the 12v charge. It would take a long time to charge the batteries, I am hoping 1/2 hour at full chat will see it charged. Not sure about skill mate, it's just a bit of tinkering. Ha ha

I could be wrong here but if you are using leisure batteries i seem to remember they don't like being charged at a lot of amps? Might be worth building in a volt/ amp meter to monitor the state of charge of the batteries so you don't have to run the engine for longer than you have to.

Probably a good idea to disconnect from the caravan electrics whilst its charging too.

[composimmonite]

What is the battery used for in the caravan ? Changing bulbs and fluorescent tubes to LED items reduces the power consumption and LCD instead of traditional tube type saves power there as well.