voltage or current sensing alternator regulators

Submitted: Saturday, Feb 05, 2005 at 01:30
ThreadID: 20126 Views:2829 Replies:4 FollowUps:4
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running your engine while using electric winch . can it burn out your alternator & if so how to get around the problem?
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Reply By: Rosco - Bris. - Saturday, Feb 05, 2005 at 07:38

Saturday, Feb 05, 2005 at 07:38
Can't see why. For example let's say you have a 100A alternator and the winch is drawing 300A.

Then 100A from the alternator and 200A from the battery.

AnswerID: 96745

Reply By: Member - DOZER- Saturday, Feb 05, 2005 at 08:40

Saturday, Feb 05, 2005 at 08:40
This is the best way to winch.....the alt actually allows for more volts (14 vs 12.7)
Now more volts means less amps to the winch, which inturn means faster spool and less heat buildup in winch.
HOWEVER nothing comes for nothing here, the extra amps (flow of power) that the alt has to produce causes it to heat up...really hot!
So the best way to do it is run motor, winch for a minute at a time and give it a rest for a minute...lets everything stay cool and stablise again.
(If the tidewas coming in, id keep winching though :-) )

AnswerID: 96752

Reply By: Redeye - Saturday, Feb 05, 2005 at 09:40

Saturday, Feb 05, 2005 at 09:40
Yes the alternator will take some of the load off the battery.

Also :- More volts means more current as the winch will have the same resistance.
current = volts / resistance.
The winch MAY get hotter as it has more power available. ;)
AnswerID: 96757

Reply By: Mike Harding - Saturday, Feb 05, 2005 at 10:35

Saturday, Feb 05, 2005 at 10:35
Good question Skinnydog.

Unless the alternator and it's associated rectifying diodes etc. has some form of over current protection (does anyone know if they usually do?) built in then the answer must be; yes, it can damage the alternator/charging system.

Let's say the winch draws 300A under load. When the winch draws power that load will be shared between the battery and the alternator (the only sources of power available). The proportion of the 300A each supplies will be according to it's internal impedance. If you commence winching with a good battery then chances are the battery will have a lower internal impedance than the charging system and thus will supply the majority of the current. As you continue to winch a fairly complex situation will develop where the battery charge drops (hence it's internal impedance rises) and it is able to supply less current. To make up the difference the alternator now needs to supply more current. If you continue winching for long enough the battery will be able to supply very little of the 300A and the alternator will be working flat out trying to supply as much as it can of the balance. It's at this point when there is a danger of damage to the charging system by overloading the alternator.

The only solution (as someone mentioned) is to winch for a minute and rest for a minute - how effective that will be depends upon a number of unpredictable variables but it probably gives you the best chance of succeeding. Also ensure your battery is in excellent condition before setting out on a trip where you may need to winch.

Mike Harding

AnswerID: 96768

Follow Up By: Wisey (NSW) - Saturday, Feb 05, 2005 at 16:34

Saturday, Feb 05, 2005 at 16:34
Hi Mike

as mentioned above re winching stop/ start at 1 min entervals to allow for cooling of alternator and whinching gear.
When stopping winching, do we also stop the motor to allow cooling of alternator "or" keep motor running to continue the charging of batterie/s. Will this motor running allow sufficient cooling of the alternator? I don't have any winch experience at all.

FollowupID: 355469

Follow Up By: Skinnydog - Saturday, Feb 05, 2005 at 16:53

Saturday, Feb 05, 2005 at 16:53
just to clarify things, i believe that 100series alt is current sensing as opposed to the volt sensing alt of my old 75series therefore, if my winch is pulling 300A would'nt my alt sense that & push out all of its 105A to try & keep the batt charged. also if the winch only takes a minute or so to get hot would;nt it take say 15 to 30 minutes to cool down depending on ambient temp
FollowupID: 355470

Follow Up By: Skinnydog - Saturday, Feb 05, 2005 at 17:08

Saturday, Feb 05, 2005 at 17:08
ps i think if i isolate my aux batt from the charge circuit and winch till it gets hot then while i'm resting the winch switch charge back onto batt to charge it while winch is cooling would remove risk of alt burn out.
its just that i heard of this happening which promted my question.
cheers for the thought provoking replies
FollowupID: 355471

Follow Up By: Mike Harding - Saturday, Feb 05, 2005 at 18:51

Saturday, Feb 05, 2005 at 18:51
Hi Wisey
Keep the engine running in order to put a little charge back into the battery. During that rest period the alternator will only be outputting (say?) 20A so it won't be working too hard and the intent of the rest period is mainly to allow the battery to recover. I would be less concerned about alternator temperature than overloading - but I may be wrong on that point? Even if I am, keeping the engine running will ensure air moves over the alternator which will cool it much more effectively that still air.

Hi Skinnydog
If it makes it clearer consider the alternator to be putting all it's output into the battery and none to the winch. Nevertheless the winch wants 300A and the alternator can only provide 100A. So sooner or later the battery will have given all the charge it's got to the winch and is now "empty". So now the alternator is the only thing providing power to the winch - the alternator can provide 100A but the winch wants three times as much! Unless the alternator has overload protection it won't be too long before something in the charging circuit fails.

Cooling time of the winch? Very hard to say how long it will take to get "too" hot - depends on many factors. But you are correct in that it will take longer to cool than it did to get hot.

Your "PS" is correct. That would be a pretty safe way to do things - just be sure you don't discharge your aux. battery too much and damage it.

Mike Harding
FollowupID: 355481

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