Can an alternator overcharge a battery?

Preparation is the key here, if going on a long trip, either buy a new alternator and fit that or get your one reco'ed.
either way you should have many miles of trouble free driving.
" One less thing to worry about"

@ rottodiver this would help eh
Good info ,locking that one in thanks

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Originally Posted by dom14

If I understood the posts by the fellas here correctly, the answer to your last question should be 'yes'. Under the ohms law, voltage and amperage are connected. V= IR, V=Voltage, I=Amperage, R=Resistance.
So, if I understand correctly, even though the alternator constantly produce 60amp out put at around 20V or so, the regulator regulates the charging voltage to around 14.5V and whatever the amps based on battery's charging state, and even reduces the voltage to around float voltage which is around 13.5V, with minimum amps based on the 'feedback' from the battery. In other words I don't need to worry about battery getting overcharged in long non-stop drives, unless the regulator is faulty.
If I'm wrong, please somebody correct me.

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I know you wish to fully understand the operation of an alternator, but please don't get yourself confused. The amount of amps drawn from the alternator varies between, say 5amps to its maximum output, depending on what load is connected. For example: battery charge, ignition lights, air conditioner, windscreen wiper and stereo, etc. The regulator is designed to keep the voltage constant, even with varied engine speeds. So the short answer is, no, a fully functioning regulator should not overcharge a battery.

Hi Cuppa,
Thanks for the very informative and helpful post. Yeah, I understand your point. I gotta draw a line somewhere how many spares I carry.
I may be overdoing certain things for my central Australian trips. I thought of carrying a spare head and a head gasket as well, which I already have it ready. That 'cos I wasn't sure my last head gasket job was done good enough for long trips, 'cos the head was not properly reconditioned by the machine shop. I reckon you can carry all these stuff and the diff or gearbox can fail, making everything even more expensive with carrying all the spare parts that doesn't help with the actual breakdown when it happens. I do carry, spare plugs, hoses, ignition coil, oil, water, battery, etc.
Spare secondhand alternator probably not going to add lot of extra weight, but I'd need to draw the line somewhere of course.
I reckon the best approach probably is to have the alternator reconditioned again and the cylinder head redone for the peace of mind, and etc etc, rather than carrying many heavy spare parts.

I guess there's no such thing as a safe trip. :tongue:

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Originally Posted by Cuppa

Correct.
Depending upon where your long trip takes you, carrying a spare alternator is IMHO overkill. Perhaps not if your intention is to spend long periods of time away from any 'civilisation', but most towns will have some sort of access to an auto electrician/wreckers or whatever. When our bus's alternator died going up WA's north west coast, we found a replacement from a wrecker in Sydney & had it freighted to Broome. A patrol alternator would be much easier to source I think. You could carry a spare regulator, but there are basically two types, internal & external. Replacing an external one would be a fairly straightforward swap over, but an internal one not so easy. Of course it depends on what has caused the regulator to fail. Replacing a dead one may just result in the the replacement being killed too. I am no expert in these things, but seem to recall that the cause of our (internal) regulator's death was the alternator's plastic brush holder collapsing.
Perhaps Yendor might make further knowledgeable comment in case what I've written could be misleading?

Cuppa

Ps. I just noticed the 'big red' description of intended trip(s). Doesn't really change my thoughts though. We all need to carry basic spares, but where to stop? Spare alternator, spare turbo, spare motor, etc etc. The more you carry the greater the weight, increased stress on the vehicle, the higher the chance of some sort of failure. A difficult balancing act ..... But I doubt many folks carry spare alternators, just make sure they are happy that what they have is in good order before leaving.

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Hijacking?!! Noway mate. On the contrary, you may have just saved my life with a vital tip.
Thought just crossed my mind, since I'm carrying a generator, I should be able to charge the battery as well.
So, I don't think I would carry a spare alternator, rather make sure the existing one is in spotless condition before I take off, and make sure
I don't forget the auxiliary battery and the generator(which I won't, 'cos I need it badly for camping) . :beer:

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Originally Posted by rottodiver

Going back a couple of years ago I was on a trip and my alternator died( gu patrol 4.5 petrol)... I needed to get about 900 km to home without one.... After speaking to people on here and auto electricians in Perth overt he phone I found out the ignition needs about 4 amps per hour to run the patrol once started, so we turned off air con radio all electrics in the car, I put the solar panels on the roof and via an anderson plug connected them to my battery, I linked the dual batteries together and off we went( my batteries were fully charged), when I stopped for fuel I kept the patrol running I indicated at a minimum and let the car slow down over distances instead of breaking... I made it all the way home. I did not have enough power to restart the patrol when I got home but it ran all the the way!
I don't think the solar panels did too much as it was cloudy most the way home typically....

Sorry to hi jack the thread with that little story but thought it was relevant if your alternator dies and this story may help someone else who has a similar situation and gets worried about having to get home...

Scotty

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Originally Posted by dom14

Thought just crossed my mind, since I'm carrying a generator, I should be able to charge the battery as well.

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Be aware that simply carrying the gennie will not be sufficient for recharging a battery. Although many gennies have a nominal 12v output, the voltage from these outputs, whilst sufficient to run an appliance, is generally too low to be any good for charging a 12v battery, which requires 14+ volts. The gennie will do the job without problem if you also carry a 240v mains charger.

Cuppa

A mob called Outback Engineering make a Gen set with an Alternator bolted to it.
I think they make 2 types, one is 100 amp, price wise they are around $800 and would suspect charging rate
would be similar to your Patrol

Could be Christie engineering I'll need to check
both make gear for 4x4s

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Originally Posted by dom14

Hi Cuppa,
Thanks for the very informative and helpful post. Yeah, I understand your point. I gotta draw a line somewhere how many spares I carry.
I may be overdoing certain things for my central Australian trips. I thought of carrying a spare head and a head gasket as well, which I already have it ready. That 'cos I wasn't sure my last head gasket job was done good enough for long trips, 'cos the head was not properly reconditioned by the machine shop. I reckon you can carry all these stuff and the diff or gearbox can fail, making everything even more expensive with carrying all the spare parts that doesn't help with the actual breakdown when it happens. I do carry, spare plugs, hoses, ignition coil, oil, water, battery, etc.
Spare secondhand alternator probably not going to add lot of extra weight, but I'd need to draw the line somewhere of course.
I reckon the best approach probably is to have the alternator reconditioned again and the cylinder head redone for the piece of mind, and etc etc, rather than carrying many heavy spare parts.

I guess there's no such as a safe trip. :tongue:

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It is amazing how everything adds up when you go on a big trip, and you end up not being able to physically fit it all in .....

We just completed a double Simpson Desert crossing this year, with mine being the newest vehicle to a GQ being the oldest. None of us carried major component spare parts, but we were all prepared, and we are all mechanically minded. We had some issues with each of the vehicles, but with a bit of lateral thinking and a combination of tools and bits from each vehicle we managed to solve every issue. ( I must add that none of the issues would have stopped us in our tracks - we were always mobile, but we had things like leaking injectors, fuel pickup problem in the fuel line, broken roof rack, bolts fallen out, broken disc backing plate, etc ).

A pre-trip inspection is a must as this can let you solve any issues before you get out there, but that sometimes won't pick up things like an alternator about to fail in 1000klms.

Another point to consider is that these days you wont be on your own, and there are cars travelling each day in both directions. People are generally fairly helpful as they are relaxed and on holidays and no-one likes to see another traveller stuck, especially if they can see that you haven't tried to do anything stupid but have had a genuine breakdown. You will find more helpful people out there than you would in the city ...... everyone will stop to see if you are OK.

With modern communications or even the passing traffic, you could get 'news', to either Birdsville or Mt Dare, and they could get a fellow traveller to bring a part out to you on their way if the part was small enough, or arrange a more costly tow ...:(

We have done that before for others and brought out bits to get them on their way - you may have to just wait a day or two ......

Mic

Hi, Cuppa,
Yes I do carry a regulated power supply with the voltage range between 0-25V, which I built back in 1996 when I was a young kid for a TAFE project. I still use it to charge the batteries, and even to stage charge the old batteries. I do it by manually changing the voltage and amps as the battery progress through the charging stages. I've been getting tired of doing it though, so I'm about by a battery charger that does it, at least on one of those three stage chargers. Only thing I do need is a better inverter now, preferably a true sine wave one, but they are pretty dear though.
The square wave ones are cheaper, but tend to generate heat with some appliances.

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Originally Posted by Cuppa

Be aware that simply carrying the gennie will not be sufficient for recharging a battery. Although many gennies have a nominal 12v output, the voltage from these outputs, whilst sufficient to run an appliance, is generally too low to be any good for charging a 12v battery, which requires 14+ volts. The gennie will do the job without problem if you also carry a 240v mains charger.

Cuppa

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Another idea just came to my mind after Threedog's post is that simply attach the gennie to the roof rack and connect it from there's to the battery and keep driving, while keeping an eye not to overuse the gennie.

That would be hard to fit in under the bonnet, wouldn't it?
Keeping it on the roofrack and connecting to the battery via the anderson plug connector as you picture showed, should solve the problem?!!!

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Originally Posted by threedogs

A mob called Outback Engineering make a Gen set with an Alternator bolted to it.
I think they make 2 types, one is 100 amp, price wise they are around $800 and would suspect charging rate
would be similar to your Patrol

Could be Christie engineering I'll need to check
both make gear for 4x4s

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