Thread: Electric winch on a series II

Most winches draw more current than any generator or alternator can provide and will rely on the battery to provide the extra power required.

Here's something I found on REMLR:

Generators are less efficient at charging / restoring your battery's cranking power. Alternators are much better and if you are having starting / ignition troubles, you can count on having more engine cranking time. The power used by a startermotor on generator or alternator fitted engine is the same. What differs is the number of times you can crank the engine before the battery is flat, which is a result of higher capacity battery type and battery recharge time. After the engine begins to run, an alternator fitted engine will then recharge its battery and be ready to go do it all again in a shorter period of time than a generator.

Taken from Australian Military Land-Rover Series 2A Parts -REMLR under the "Electrical System" heading.

So basically, your winch will run off your battery, but it would be a lot more efficient recharging your battery with an alternator. You would find the winch would run for longer if you had an alternator.

If you're not too worried about originality, I've read it's not hard to swap over to a negative earth configuration and run an alternator. I personally haven't done it, but it apparently takes about an hour. There's guides available online, such as this: Land Rover FAQ - Repair & Maintenance - Series - Electrical - Reference - Negative Earth Conversion

An alternator will not give you more cranking time, the battery will flatten in exactly the same time! However once the engine has started the alternator will recharge it quicker...

The old Lucas generators were spec'd at about 20amps, whilst a replacement alternator could (depending on the model) produce 40,50,60amps or more. So whilst the generator may only trickle charge the battery if all the lights are on, the alternator will have power to spare.

Simplistically:

In the case of a winch, a 9500lb winch under full load might draw close to 400amps. If the generator produces 20amps and the winch draws 400amps, the battery is supplying 380amps. With a 60amp alternator the battery is supplying 340amps. Either load will drain the battery fairly quickly, but the alternator will recharge it three times faster. So you have slightly more winching time before the battery is flat, and a far quicker recharge time.

But also note that because the battery is supplying most of the power, a small battery will be flattened very quickly!

Overall, if you intend to winch for 2 minutes and then drive for two hours, both systems will perform much the same as long as the battery is big enough to supply 400amps for those 2 minutes of winching time. But if you intend to winch for 4 minutes, drive for 10 minutes, winch for 4 minutes etc., then the battery needs to be big enough to drive the winch for 4 minutes, and the alternator needs to be big enough to replace that power in the 10 minutes of driving! If you also have a pair of 100W spotties in addition to the standard lights, the generator will be in trouble, as it can't produce enough power to run the lights, nevermind charging the battery!

400amps at 12V = 4800watts
60amps at 12V = 720watts
20amps at 12V = 240watts

Ignoring losses and efficiencies, and any other power usage (lights etc.) winching will, from the battery, use:

4800 - 720 = 4080Watts for the 60amp alternator
4800 - 240 = 4560watts for the 20amp generator

The usage to recharge ratio will therefore be:

4080:720 = 1min winching to 5.7min recharge for the alternator
4560:240 = 1min winching to 19min recharge for the generator

As long as the battery is big enough to support the winch for the time it is in use, it is just a matter of how long it will be before the next winching session. But remember to allow the battery to recharge before you switch the engine off!

Originally Posted by Warb

An alternator will not give you more cranking time, the battery will flatten in exactly the same time! However once the engine has started the alternator will recharge it quicker...

The old Lucas generators were spec'd at about 20amps, whilst a replacement alternator could (depending on the model) produce 40,50,60amps or more. So whilst the generator may only trickle charge the battery if all the lights are on, the alternator will have power to spare.

Simplistically:

In the case of a winch, a 9500lb winch under full load might draw close to 400amps. If the generator produces 20amps and the winch draws 400amps, the battery is supplying 380amps. With a 60amp alternator the battery is supplying 340amps. Either load will drain the battery fairly quickly, but the alternator will recharge it three times faster. So you have slightly more winching time before the battery is flat, and a far quicker recharge time.

But also note that because the battery is supplying most of the power, a small battery will be flattened very quickly!

Overall, if you intend to winch for 2 minutes and then drive for two hours, both systems will perform much the same as long as the battery is big enough to supply 400amps for those 2 minutes of winching time. But if you intend to winch for 4 minutes, drive for 10 minutes, winch for 4 minutes etc., then the battery needs to be big enough to drive the winch for 4 minutes, and the alternator needs to be big enough to replace that power in the 10 minutes of driving! If you also have a pair of 100W spotties in addition to the standard lights, the generator will be in trouble, as it can't produce enough power to run the lights, nevermind charging the battery!

400amps at 12V = 4800watts
60amps at 12V = 720watts
20amps at 12V = 240watts

Ignoring losses and efficiencies, and any other power usage (lights etc.) winching will, from the battery, use:

4800 - 720 = 4080Watts for the 60amp alternator
4800 - 240 = 4560watts for the 20amp generator

The usage to recharge ratio will therefore be:

4080:720 = 1min winching to 5.7min recharge for the alternator
4560:240 = 1min winching to 19min recharge for the generator

As long as the battery is big enough to support the winch for the time it is in use, it is just a matter of how long it will be before the next winching session. But remember to allow the battery to recharge before you switch the engine off!

Thank you very much for taking the time to explain all of that I now have a very good idea of what's going on. I think the best option is to wait until finances allow and get a PTO or Capstan winch . It will also sit better on the Land Rover .

Thanks

PTO winches and electric winches both have pro's and cons.

A PTO winch will pull all day as long as the engine is running. But if you drive in to a river and kill the engine (water in the HT leads etc.) the electric winch will pull you out (given battery capacity!) but the PTO won't. The electric winch, on the other hand, probably requires more maintenance.

If you're using the LR in anger, the alternator will also provide power for extra spotlights, fridge, GPS etc. A 20amp generator produces enough power (if it's working to factory spec.) for the standard vehicle...just. Add a few extra power draws (like spotlights) and it struggles. With a less than perfect generator, plus "normal" touring extras like spotlights, two-way and a fridge, it would be entirely possible to drive half the night and arrive with a flat battery!

But yes, the PTO winches do look good!

You also need to consider whether you need a powered winch at all....

Being at the front of the vehicle it pulls you forward (maybe a bit sideways), it may be that you need to pull it backwards out of whatever you're stuck in.
Are you intending to do some serious offroading and therefore need a winch or is it a 'just in case you get stuck' piece of equipment. If it's the latter you could consider a hand winch.
A hand winch makes you think hard before tackling difficult terrain because you will have to work bloody hard to hand winch out of trouble but you can winch forwards, backwards, sideways and you can use it to stand the vehicle back on all fours if you tip it over.
In fact if you fit a powered winch to the vehicle a hand winch can still be a useful item to carry.


Colin

Originally Posted by Warb

The old Lucas generators were spec'd at about 20amps, whilst a replacement alternator could (depending on the model) produce 40,50,60amps or more. So whilst the generator may only trickle charge the battery if all the lights are on, the alternator will have power to spare.

I remember driving around with my dad in his old Morris van File:Morris Commercial JB 1957.jpg - Wikipedia, the free encyclopedia, and at night he would creep up behind the car in front (as far as is possible in a Morris JB ) and turn his headlights off so that he could use the other car's headlights, because the generator could only just keep up with the headlights, never mind charging the battery.

Memories . . .

Peter

My very first car was a Morris 1100 "SuperDeluxe" (which seemed to mean it had quilted material on the back of the seats). It had been abandoned in a garage years earlier when the engine failed to start - the owner removed his golf clubs, shut the garage door in disgust and never went back. It was offered to a school friend of mine, the owner was a friend of his father's, but he had just acquired a Riley Elf (Mini with fins!), so I ended up with it.

My father towed it home for me after I had fixed the brakes. The motor was seized and the bores ruined, but my father had a friend with an A Series motor out of a crashed grass track racer in Bristol, so he drove me halfway across England to collect it. Free car, free motor! I swapped motors, patched up the few spots of rust on the body and got it through its MOT..... All I needed then was a driving licence! All those years ago and I still remember the registration number!

But the same generator issues were there - positive earth and lights that dimmed when you took your foot of the throttle!! I converted it to negative earth (flicking sparks off the field coils, if I remember correctly) so I could fit a radio, but was stuck with the under powered generator system.....