# alternator voltage regulation for 60v battery

#### jerephil60v

Joined Nov 26, 2015
8
Greetings all,

I am looking for some guidance in modifying a standard car alternator to charge up and/or maintain a 60v battery. Due to my limited knowledge regarding this, presently i can only provide the followinig info. Let me know if you need more data in order to come to an answer.

1. battery type: 5 12v led acid batteries, creating a 60v battery pack.
2. system: battery to be charged is the backup battery for my application.
3. note: the battery being charged will have no load on it while the alternator is in motion.
4. alternator: see picture. or any standard (cheap) car/truck alt. picture is via $65 ebay alt. I am hoping someone can enlighten me as to how to build/add/mod the/an alternators voltage regulator from 14.7v up to 60v (or what is necessary for a 60v battery pack). Thanks a TON in advance, jerephil #### Dodgydave Joined Jun 22, 2012 9,953 Only way to make the alternator give out more voltage, is to tap into the slip ring terminals from inside, and bring them outside to your own regulator, the slip rings feed the exciter field, you may find the alternator will be limited in producing a high voltage, say upto 30V. Thread Starter #### jerephil60v Joined Nov 26, 2015 8 thanks for your timely response. I didn't expect one so soon. so it seems i need an external regulator. how best to i find one..and with what particular specs? is there a specific alternator that you would suggest instead? or could you suggest a specific combination of both? I'd rather not have to drop$100+ on an alt. but all said and done and operational, it would be worth it.

by looking at other posts, it looks like i may need more than 60v output to supply my (unused) battery with a full and ready to "rock and roll" charge.

#### Dodgydave

Joined Jun 22, 2012
9,953
Your probably better with something like that buck booster, but don't forget they waste power also,

so if your feeding out 60 V at 2amps thats 120W, so 120W at 12V input that 10amps input at least.

#### jerephil60v

Joined Nov 26, 2015
8
i see (not so much comprehend...lol), so you say that ebay linked product would work?

sry, but your second line is quite abit "way over my head"...

Joined Jul 18, 2013
23,111
I have built one for a 250v generator using a LM311 comparator IC and a mosfet, it should be adaptable for this application.
IIRC the current for the average auto alternator field is around 2amps @ 12v in.
I don't recall what the rpm is needed for 60v though, I have seen 48v.
Have you built any electronics before?
Max.

#### Dodgydave

Joined Jun 22, 2012
9,953
The alternator will give out 30amps possible at 14V, best to get a working alternator from a scrap/breakers yard, and modify it like i said in post2, by bringing the field winding out from the slip rings, then you can put a variable supply across the slip rings, spin the alternator and see what voltage it will go upto.

#### jerephil60v

Joined Nov 26, 2015
8
I have built one for a 250v generator using a LM311 comparator IC and a mosfet, it should be adaptable for this application.
IIRC the current for the average auto alternator field is around 2amps @ 12v in.
I don't recall what the rpm is needed for 60v though, I have seen 48v.
Have you built any electronics before?
Max.
no friend, i haven't built electronics before. I purchased me a very nice electric scooter. 2000w motor with a 60v battery.

i figured if i got myself a spare battery, use an alternator (10-speed bicycle gears to get the 2000-3000 alt. RPM's up big sprocked on the 12in tall rear tire and the smallest sprocket on the alternator) using all this forward motion to charge up the secondary battery while using the primary battery to power the bike into motion. I knew right off, it would be nearly impossible to try and charge up/keep charged the battery being used to power the bike with an car alternator because the draw from the 2000w electric motor would create too much frictional resistance in the alt. so i thought, take away the factor of the draw and charge only a battery that is not being used.

BY THE WAY.... HAPPY THANKSGIVING!!!!!

Last edited:

#### jerephil60v

Joined Nov 26, 2015
8
The alternator will give out 30amps possible at 14V, best to get a working alternator from a scrap/breakers yard, and modify it like i said in post2, by bringing the field winding out from the slip rings, then you can put a variable supply across the slip rings, spin the alternator and see what voltage it will go upto.
I dono if this information is helpful to you or not, but maybe i should have said this from the start.
I purchased me a very nice electric scooter. 2000w motor with a 60v battery.
i figured if i got myself a spare battery, use an alternator (10-speed bicycle gears to get the 2000-3000 alt. RPM's up big sprocked on the 12in tall rear tire and the smallest sprocket on the alternator) using all this forward motion to charge up the secondary battery while using the primary battery to power the bike into motion. I knew right off, it would be nearly impossible to try and charge up/keep charged the battery being used to power the bike with an car alternator because the draw from the 2000w electric motor would create too much frictional resistance in the alt. so i thought, take away the factor of the draw and charge only a battery that is not being used.

BY THE WAY.... HAPPY THANKSGIVING!!!!!

#### jerephil60v

Joined Nov 26, 2015
8
no friend, i haven't built electronics before. I purchased me a very nice electric scooter. 2000w motor with a 60v battery.

i figured if i got myself a spare battery, use an alternator (10-speed bicycle gears to get the 2000-3000 alt. RPM's up big sprocked on the 12in tall rear tire and the smallest sprocket on the alternator) using all this forward motion to charge up the secondary battery while using the primary battery to power the bike into motion. I knew right off, it would be nearly impossible to try and charge up/keep charged the battery being used to power the bike with an car alternator because the draw from the 2000w electric motor would create too much frictional resistance in the alt. so i thought, take away the factor of the draw and charge only a battery that is not being used.

BY THE WAY.... HAPPY THANKSGIVING!!!!!
havings said all that, can you build something for what i'm looking for or is it a matter of buying x, y, and z and do a, b, and c?

#### Alec_t

Joined Sep 17, 2013
12,070
so i thought, take away the factor of the draw and charge only a battery that is not being used.
That will give a nett loss of energy, because of inefficiency in the system (friction etc). The power to drive the alternator and hence charge up the unused battery would be coming from the battery in use!

Joined Jul 18, 2013
23,111
.

BY THE WAY.... HAPPY THANKSGIVING!!!!!
Thanks but it was Oct 12th for us!.
Max.

#### Dodgydave

Joined Jun 22, 2012
9,953
I dono if this information is helpful to you or not, but maybe i should have said this from the start.
I purchased me a very nice electric scooter. 2000w motor with a 60v battery.
i figured if i got myself a spare battery, use an alternator (10-speed bicycle gears to get the 2000-3000 alt. RPM's up big sprocked on the 12in tall rear tire and the smallest sprocket on the alternator) using all this forward motion to charge up the secondary battery while using the primary battery to power the bike into motion. I knew right off, it would be nearly impossible to try and charge up/keep charged the battery being used to power the bike with an car alternator because the draw from the 2000w electric motor would create too much frictional resistance in the alt. so i thought, take away the factor of the draw and charge only a battery that is not being used.

BY THE WAY.... HAPPY THANKSGIVING!!!!!

we don't have thanksgiving in UK, enjoy your dinner

#### tcmtech

Joined Nov 4, 2013
2,867
First off to charge a 60 volt battery you will need around 72 volts which is a pretty far reach for a standard cehapo automotive alternator to get to. Now almost bigger 24 volt 100+ amp truck alternators easily put out 72+ volts with a pretty decent amp capacity behind it.
The first problem you will have with running a alternator at higher than stock voltage output is the rotor field coils are designed to work at the stock voltage rating so you have to limit the input voltage or they will burn up pretty fast at 5X their normal input limits.

Second as I am reading your intended design you want to use a 60volt 2000 watt motor to drive the scooter that will then drive the alternator to recharge a second battery on the the scooter? If so why being you will gain nothing from it but a shorter run time between both batteries?

#### shortbus

Joined Sep 30, 2009
8,585
You guy's are forgetting, over unity is possible, I saw it on the internet!

#### ian field

Joined Oct 27, 2012
6,539
First off to charge a 60 volt battery you will need around 72 volts which is a pretty far reach for a standard cehapo automotive alternator to get to. Now almost bigger 24 volt 100+ amp truck alternators easily put out 72+ volts with a pretty decent amp capacity behind it.
The first problem you will have with running a alternator at higher than stock voltage output is the rotor field coils are designed to work at the stock voltage rating so you have to limit the input voltage or they will burn up pretty fast at 5X their normal input limits.

Second as I am reading your intended design you want to use a 60volt 2000 watt motor to drive the scooter that will then drive the alternator to recharge a second battery on the the scooter? If so why being you will gain nothing from it but a shorter run time between both batteries?
A while ago I found a magazine archive that included hillbilly electrics - unfortunately, I've had a total crash since then (W10) and lost my favourites.

There were articles on rewinding the old dynamo style generators for farm electrics.

Last time I looked, car alternators had the field winding in the rotor, fed by brushes/slip rings. That means the winding that produces the output is on the stator poles and should be easier to rewind.

Modern car alternators probably have coaxial pole pieces so the field winding is also stationary, as first appeared on motorcycles - but that shouldn't cause any new difficulties rewinding the stator.

#### tcmtech

Joined Nov 4, 2013
2,867
Last time I looked, car alternators had the field winding in the rotor, fed by brushes/slip rings. That means the winding that produces the output is on the stator poles and should be easier to rewind.

Modern car alternators probably have coaxial pole pieces so the field winding is also stationary, as first appeared on motorcycles - but that shouldn't cause any new difficulties rewinding the stator.
Every automotive/large truck/tractor/industrial application alternator I have ever taken apart still used the standard field windings the rotor design. About the only variation in that is on some of the bigger high end units they use a brushless rotor system but that is still uses the same basic working design as the brush type but with the addition of a smaller second stator field winding set and a rotor fieldpower pickup winding set.

What I have found that are far easier to modify for higher output voltages is that most of the larger 150+ amp 12 and 24 volt alternators use several smaller gauge windings in parallel for each of the stator phases which with a bit of work are pretty easy to separate and reconfigure in series to get much higher output voltages.

I have one 130 amp 24 volt Leece Neville alternator that was built with a triple Delta stator winding configuration that when rewired as a single Wye configuration will now easily put out 160 - 180 VDC at 20+ amps without issue.

As for the stock diodes they passed a 500 volt hi pot test so they apparently have a pretty high breakdown voltage.

#### ian field

Joined Oct 27, 2012
6,539
Every automotive/large truck/tractor/industrial application alternator I have ever taken apart still used the standard field windings the rotor design. About the only variation in that is on some of the bigger high end units they use a brushless rotor system but that is still uses the same basic working design as the brush type but with the addition of a smaller second stator field winding set and a rotor fieldpower pickup winding set.

What I have found that are far easier to modify for higher output voltages is that most of the larger 150+ amp 12 and 24 volt alternators use several smaller gauge windings in parallel for each of the stator phases which with a bit of work are pretty easy to separate and reconfigure in series to get much higher output voltages.

I have one 130 amp 24 volt Leece Neville alternator that was built with a triple Delta stator winding configuration that when rewired as a single Wye configuration will now easily put out 160 - 180 VDC at 20+ amps without issue.

As for the stock diodes they passed a 500 volt hi pot test so they apparently have a pretty high breakdown voltage.
Motorcycle alternators can produce potentially lethal voltages if run off load.

Once I used a motorcycle rectifier for 230V mains - but thought better of it and found as soon as possible a part that I could verify its ratings.