Can an alternator overcharge a battery?

[dom14]

I'm just wondering, can an alternator overcharge a battery on non-stop long trips?
By that I didn't mean a faulty voltage regulator.
So, the regulator controls the voltage at around 14V regardless of the speed the alternator spins.
Then I'm not sure whether it stops charging the battery or trickle charge the battery once it's fully charged. How does the alternator regulate the current once the battery fully charged or does it do that at all?
Is there a mechanism in the alternator to reduce the current it supply to the battery when it's fully charged?
Thanks.

[threedogs]

Yes an alternator can over charge a battery to the point it boils, very dangerous situation,
Its caused by brushes only contacting on their edges, well that's one cause

This was years ago on the way back from Bathurst in a HQ panelvan

[Yendor]

The regulator stops the alternator from overcharging by reducing the amount of field to the alternator's rotor.

[AB]

And the battery can look like this....My regulator died on a trip a couple of years ago and was left unnoticed for a few hours.

I think I read 15 volts when I found out.

33934
http://www.nissanpatrol.com.au/forums/images/misc/pencil.png

[threedogs]

One give away was the HQ headlights were very bright, but most modern sealed batteries have explosion caps built into the casing

[Rustyboner81]

Yes.
I had a different problem where the fusable link thars inline between the alternator and battery hsd deteriorated due to age or a previous overcharge condition. As a result minimal cahrge was getting back to the battery. All lights and acc. Would work fine while the car was running but bsttery would die...... volt gauge would read 15-16v

Put a new inline 60amp fuse in all has been good since.

Im just saying if you do get an overcharge dont condem your battery or alternator straight away

[NP99]

Yes an alternator can over charge a battery to the point it boils, very dangerous situation,
Its caused by brushes only contacting on their edges, well that's one cause

This was years ago on the way back from Bathurst in a HQ panelvan

HQ panel van......weren't they the ducks guts in their day :)

[Robo]

HQ panel van......weren't they the ducks guts in their day :)

The old sin bin !!

[Squalo]

I am not entirely sure about cars as they have slightly different set-ups in the charging circuit to bikes, but on a bike all excess current is dissipated by the regulator/rectifier as heat (which is why bikes experience reg/rec failure, especially Hondas).

Is this how a car charging system works?

[alfonso]

An alternator will not overcharge your battery on a long trip unless it is faulty . charge is usually 13.8 to 14.1 volts after battery is charged voltage will drop to around 13.5 to 13.7 which is float.Also you use power from battery such as radio and lights. If your vehicle is well maintained there shouldn't be a problem

[dom14]

Thanks for the clear answer. And sorry for the long wait to reply. :)

An alternator will not overcharge your battery on a long trip unless it is faulty . charge is usually 13.8 to 14.1 volts after battery is charged voltage will drop to around 13.5 to 13.7 which is float.Also you use power from battery such as radio and lights. If your vehicle is well maintained there shouldn't be a problem

[dom14]

Is it a good to have a backup alternator on long big red trips? Or is it an overkill?!
Or is it possible to purchase a regulator bit and keep it just in case.
Mine is GQ Patrol with RB30 motor(Carby). I had the alternator reconditioned around 2 and half years ago.

[dom14]

Is it a good to have a backup alternator on long big red trips? Or is it an overkill?!
Or is it possible to purchase a regulator bit and keep it just in case.
Mine is GQ Patrol with RB30 motor(Carby). I had the alternator reconditioned around 2 and half years ago.


And the battery can look like this....My regulator died on a trip a couple of years ago and was left unnoticed for a few hours.

I think I read 15 volts when I found out.

33934
http://www.nissanpatrol.com.au/forums/images/misc/pencil.png

[rottodiver]

ok here is what could be perceived as a dumb question but i will fire it away anyway..... is it not amps that charge a battery? so if so why would the voltage change.... would the regulator "regulate" the amperage...???

Scotty

[mudnut]

The battery will except high amps from the alternator immediately from start up, which also causes the alternator voltage to drop. The voltage regulator supplies more amperage to the rotor, which in turn makes the output rise to the required voltage. As the battery charges, the amperage it accepts drops which in turn causes the alternator output to rise. The voltage regulator reduces the flow to the rotor which in turn lowers the voltage output of the alternator. The regulator works constantly to keep the output at the required level.

[threedogs]

@NP99 top of the range Belmont speedo/heater only very Spartan indeed

Get your battery checked to see if it holds a charge,
and check your alternator at the same time
Edit not sure what alternators Patrols run but my last 4x4 was always doing alternators [bog holes/water crossings]
I turfed the OE in favour of a Bosch, reg was only $20 compared to $80 for the OE one, plus if need be you could
repair out in the field

[dom14]

ok here is what could be perceived as a dumb question but i will fire it away anyway..... is it not amps that charge a battery? so if so why would the voltage change.... would the regulator "regulate" the amperage...???

Scotty

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.

[Cuppa]

Is it a good to have a backup alternator on long big red trips? Or is it an overkill?!
Or is it possible to purchase a regulator bit and keep it just in case.



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.

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.

[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

[Cuppa]

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

Very relevant I reckon. As long as you have some means of keeping some charge in the battery you can keep going. We have a little Honda Gennie we bought in Perth. Have never needed it except for when the alternator died at Monkey Mia. Recharging the battery each night with the gennie (& battery charger) got us up to Broome no problem. Could have continued like that indefinitely I suppose. Don't carry the gennie any more, but like you the solar would get us out of trouble.

Cuppa

[threedogs]

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

[mudnut]

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.

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.

[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 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:


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.

[dom14]

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:


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

[Cuppa]

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


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

[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

[happygu]

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:


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

[dom14]

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.


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

[dom14]

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.

[dom14]

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?!!!


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

[brynk]

+1 on carrying a charger - don't forget the extension lead!

(hope your trip went well and the alternator didn't shyte itself, since this thread is a couple of months older now ... !)

once you get sick of roughing it and start using powered sites, they come in bloody handy to keep the freezer frozen and the cranking battery up to scratch :)

i picked up a 2 amp charger from the auto-shop in derby - it was a simple thing without any fancy-pants charge control: we'd plug that sucker into the aux battery to keep the freezer happy, and when the volts got back up to a certain level the isolator allowed current into the cranking battery as well.

9-12 hours of 'slumming it' worked out to be just enough to get the freezer to -20 and the volts in the 2ndary to 13.x

this is the isolator we installed, ~$120 jaycar:
http://www.nissanpatrol.com.au/forums/
jaycar 12v 100amp isolator MB3680 (http://www.jaycar.com.au/productView.asp?ID=MB3680&form=CAT2&SUBCATID=1004#12)

we used heavy-guage speaker wire to join the aux battery to the isolator & the isolator to the primary battery - i ran the wire in the cable guttering and installed the 2ndary in the back of our wagon - one of these days i might even change it to some sort of sealed battery; but for now, we're just using a wet-cell deep cycle which has served us well 2yrs and counting

getting back to the original topic, my understanding was the regulator also converted (3phase?) ac to dc by 'clipping the wave' - ie, only allowing current to flow out into the 12+ vdc line at a certain voltage range

as to 'how much' is output, three separate considerations affect this:

a. as the charge stored in the battery increases, the overall system voltage downstream of the regulator increases

b. alternator-regulator magnetically affects slip-rings that shift the rotor-shaft relative to the stator, which increases the distance between the magnets and windings - how it does this is (1) black magic to me, (2) based on the voltage downstream of the regulator and (3) something to do with electro-magnets

c. this change in distance leaves the windings in a weaker part of the magnetic field, which in turn reduces the current induced in the windings: a drop in amps for the same resistance results in a decreased voltage (edit: got my wires crossed a couple of times... seems i left my maths brain behind at 30 deg c), because our mate ohm said so

... so if any part of that closed loop is fucked, then the voltage could be out of whack causing the alternator to overcharge the battery

long story short, if you have a fridge-freezer and you have an shonky alternator punching out too many volts, you could fill your fridge-freezer with bottled water and turn it down fully (coldest setting), thereby presenting a big fat juicy load for all those lovely little slaves to work on :)

as to what you do with the frozen bottles of water, well, i'll leave that to your imagination - but i find it does wonders keeping the beer cold

if you can stomach it, here is a riveting read : http://alternatorparts.com/understanding-alternators.htm

ps - talking about carrying spares, i wound up with 2 multimeters in our rig - at 10 bucks a piece you can't go wrong!

[dom14]

+1 on carrying a charger - don't forget the extension lead!

(hope your trip went well and the alternator didn't shyte itself, since this thread is a couple of months older now ... !)

<snip>
as to what you do with the frozen bottles of water, well, i'll leave that to your imagination - but i find it does wonders keeping the beer cold

if you can stomach it, here is a riveting read : http://alternatorparts.com/understanding-alternators.htm

ps - talking about carrying spares, i wound up with 2 multimeters in our rig - at 10 bucks a piece you can't go wrong!

Brilliant post mate! Thanks for taking time to write it. I learnt a lot from it.
My trip went well, just nowhere as far as I wanted, 'cos I started to worry about the 'old girl's' ability to handle the tough terrain. It's and RB30, carby driven after all.
I'm doing the few more repair/upgrade on the fourby now, so I can be more at peace when next trip comes along.