Can an alternator overcharge a battery?

[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.

Attachment 33934

[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