How can I modify alternator voltage

[veggie]

Hi All,

I need a bit of help with a solution to change the voltage of an alternator.
This solution has to be as inexpensive as possible so adding a Balmar Regulation system for $300 is not feasible.

Here's the conditions:

Engine --> Alternator --> 36 volt battery --> 34 - 36vdc inverter

PROBLEM:
My two alternators are 12 volt or 24 volt.
I would like the output to be a regulated voltage in the range of 34 to 36 volt.
The battery is just a voltage clamp and I am not interested in charge algorithms. Power will pass through/around the batteries to the inverter.
Is there a simple and inexpensive way to modify the output voltage of an alternator?

Both available alternators are the Leese style with easily removable/accessible regulators mounted on the rear of the body.

Any ideas ?

Thanks,
Veggie

[BruceM]

The 24V alternator might work reasonably well at 36V.  You will need to modify the regulator or replace it.  If you can find a schematic for your existing 24V regulator, I'd be glad to take a look regarding modification.  If it's all potted, that won't fly, of course.  A homebrew circuit for this would consist of a voltage reference and op amp comparator driving a low side MOSFET.  No PCB needed but some experience in electronics is needed.  Parts cost should be under $35 at Digkey.

[mobile_bob]

i don't know what alternator you are using, which would help

there are several ways to do this, it all depends on what you have to work with.

bob g

ps.  do you have a possible source for field current?  if you are using the 12nominal alternator
then you need a 12vdc source that is not tapped off the battery bank, but better a source from the inverter
such as one of those cute little pwm power supplies that are all over ebay and elsewhere.  if using a 24v nominal alternator
then you need a 24vdc power supply, and

we need to know what rectifier your alternator is using?  are they avalanche diodes? if so you may be limited to using the 24volt alternator as the 12volt with avalanche typically start to clamp down at around 30vdc output.

depending on what you have, the diodes can be replaced with some 200piv 50amp press in replacement non avalanche diodes, then you can make the alternator put out anything you want up to 100plus volts without much trouble, albeit a bit dangerous at that high a level... but for up to 48vdc nominal (56vdc charging) no problem.

if you are faced with changing diodes, i would start with the 12 volt alternator, as the stator is likely half the resistance
with less turns having less inductance, both of which really have affect on efficiency.  the units i worked with had no problem getting up to around 80% efficiency using 12volt field and 12volt stators, running at 28.8vdc (24v nominal) at 100amps output, running stable and cool doing so.

fwiw,  i also used the same units, with 200piv diodes running at 56.6vdc (48v nominal charging) at 60amps running a bit warmer but well under limits, at better than 70% efficiency ( i don't recall exactly, but better than 70 and under 80)

the bottom line is you can get a 12 volt or frankly any alternator to produce any output voltage you like, and there are a variety of ways of getting there...

i like Bruce's comment about a purpose built regulator as well, that would be interesting too.

also the balmar is expensive, however there are other alternatives such as those built by "sterling"  that sell for around 100 bucks new, that could be adapted to your needs.

[veggie]

Bob, Bruce,

I will gather some information about my specific alternator models and get back soon.

In the meantime:

Yes: even though I will be making 36 volts I do have 12 volts available from the starting battery if needed for field control.

ALSO: I have a few of these variable voltage regulators if that would be of any help in controlling field voltage.
Let me know if this can be of any use. It can take 12 volts ( or 36 volts) and reduce to whatever I need.
< click picture to enlarge >

[BruceM]

That is a linear regulator- not useful for controlling the field current of the alternator to regulate the ouput voltage of the alternator.

[veggie]

The alternators that I have available are:

A] Leese-Neville BLD-2331-GH   (12 Volt)

B] Delco 26SI   (24 volt)

I am unable to find a wiring diagram for either unit, however they both have regulator modules screwed to the back.
The Leese regulator is a separate external module screwed onto the alternator body.
The two pictures below are the 26SI Delco.

The PDF which shows an exploded view of the unit refers to the Leese.

[mobile_bob]

i generally prefer the leece neville for this purpose

http://www.prestolite.com/pgs_products/specs.php?item_detail_id=29858&item=BLD2331GH

it appears to be an updated and heavier duty 555jho, which was 160amps and yours is 185amps

i have no idea about the diodes, they appear to be press in and therefor  could be replaced with the 200piv units
i mentioned earlier.

the delco you have having the externally accessible regulator makes it also something that could be used for your purposes.

if it were me, i would got with the leece, given its record for use such as you have in mind.

bob g

[BruceM]

Bob's your uncle on this- my only experience with alternators is my DIY linear regulator for a MB300d alternator and my DIY ST regulator (a bang-bang type low side DC switching regulator). If electronics isn't your thing, you are stuck with whatever you can find for a 36V regulator.

The basics are pretty simple: the field coil current is switched on/off to keep output rectified 3 phase DC voltage withing specified range.  The output 36VDC (nominal) could be used for excitation of the field coil, if you keep duty cycle limited so the field coil doesn't burn out.

[veggie]

Hmmm...
Ok, before I go any further down this path of hand building a custom regulator, does anyone know of a better way to get a regulated 36 volts DC to supply into my Grid Tied inverter ?
Prime mover is a 4HP diesel.
My power requirements are 36 volts and 30 amps ( or 1080 watts )

Veggie

[mike90045]

for crude, you can use the centertap off a power rheostat and get your drive current from that, but it would always be wandering around.  Have to find the current/amps value of the winding, and have the rheostat consume about 2x that to keep the current stable.

or google " adjustable automotive voltage regulator " and there are all sorts of ideas.

Could be as simple as isolating the existing regulator with a 24V zener.  May need some caps and swamping resistors to keep it stable

[veggie]

for crude, you can use the centertap off a power rheostat and get your drive current from that, but it would always be wandering around.

Mike,

Hypothetically, with a center-tapped rheostat would the alternator output voltage always be wandering if the alternator RPM was kept constant and the load on the inverter was also constant?

Veggie

[mobile_bob]

there are various things that will cause it to wander, heating is one of them
as the alternator warms up the voltage will change,  myself i would never support any scheme that
required babysitting other than the most basic machine used in an emergency installation using minimal parts
in a shtf scenario babysitting the regulator to keep somewhat stable control is probably the only place that i could
see as being viable.

one last question

are you concerned with efficiency?

if efficiency is of paramount importance, or very close to the top consider this

the leece likely has a lower stator resistance than delco, every 24volt automotive alternator has a higher stator resistance
than ones used with 12volt systems.

stator resistance plays a very significant role in efficiency when it comes to getting higher voltage output,

also 24volt stators have more turns per pole on the stator, in order to get a low rpm cut in for charging.
more turns increase the inductance of the stator,

higher inductance, makes for higher reactance the result being another signficant decrease in efficiency.

in my testing i reconnected 12volt stators from delta to wye in order to get more voltage, this increased the effective
turn count per pole, and the inductance/reactance,  the result was a much hotter running stator and dramatically lower
efficiency (down from around 80% to around 55%).  the only benefit was lower cut in for charging at the higher voltage.

so i opted for higher rpm, delta connected 12volt 555jho type alternators, made for 12volt operation, and yes i had to turn
the rpm up to ~4800rpm to get 100-130amps at 28.8vdc and was still able to get ~50-60amps at 57.6vdc.

yes higher rpm results in higher losses due to windage and friction, along with higher frequency increasing reactance, so there are also losses associated, but apparently less so than going the former route.   apparently higher turn count and higher resistance are the prevailing killer of efficiency for these machines.

also of note the 555jho and its variant (which i believe your leece to be) have a higher pole count than the delco units, this enables a lower rpm to get the higher voltage from.  the 555jho also has a short stator relative to most all of the more common leece neville offering such as those of the JB family.  the JB family has a very deep or long stator, resulting in a lot more wire and then more resistance.. this is the only reason i have not embraced the JB family of leece neville alternators for this intended use.

having said all this

i would recommend using your leece, i would remove the regulator and gain access to the brush holder, which is right under the regulator, there will be two male spade terminals to direct connect to the rotor/field.

if you have a 12volt source of dc power, such as your starting battery, you are well on your way.

the only thing you need then (if you are buffering with batteries for 36volts?  i assume so)  take a sample line off the first 12 volt battery in the 36volt string.  this is your sense line.

look for a sterling regulator, they are about the most reasonable regulator on the market, there used to be a couple vendors on ebay selling them.... you want a 12volt unit.

you derive the power for the regulator from the starting battery,  you sense the 36volt string at the first 12volt, connect the regulator sense to that battery positive post, connect the regulator to the field of the alternator, then spin the alternator up to about 5000rpm and you will be charging at 36vdc nominal, and have the ability to program the regulator for soft start, whatever battery technology you want, whatever voltage setpoint you want, and also depending on regulator model have a temp sensor to monitor the battery temperature and the alternator stator temperature so that both are protected.

if you are feeding a grid tie,  i would still use a battery bank to buffer, and the battery bank need not be some large deep cycle set, 3 matched small batteries used for small cars would be more than good enough to get the job done.

done this way the alternator will run just fine for a very long time, provided (which i almost forgot) that you change out the press in diodes for 200piv non avalanche style diodes,  don't fret the changeover, any alternator/starter repair shop can change them out, and likely already can provide an aftermarket rectifier bridge to replace yours with... you just need to tell them that the alternator will not be used in a truck and not be used for 12volts anymore, tell them it will be doing 36volt duty and they will understand...  the diodes cost about $7,50 each in 2011 dollars US. (retail),  you only need 3pos diodes and 3 negative, for a total of 6 diodes to do the job.

i hope this helps
bob g

[mobile_bob]

apparently this is the latest offering from sterling, it uses a sense wire so it will work for the intended purpose.

http://www.ebay.com/itm/Sterling-ProReg-BW-Advanced-Alternator-Regulator-100-Amp-/171771756153?hash=item27fe64fe79:g:K74AAOSwzrxUyWLR&vxp=mtr

here is the installation manual, with more details about the unit.
https://cdn.shopify.com/s/files/1/0658/7343/files/eng_fre_ger_a5.pdf?483

this unit is more expensive than what their earlier offering were, maybe they are better, maybe they are just better packaged
i don't know.

i will look further for other options
bob g

[mobile_bob]

here is another possible solution, and it will bolt right onto your leece alternator in place of your oem regulator

http://www.ebay.com/itm/Voltage-Regulator-Motorola-Marine-Mercruiser-Alternator-/231997059754?hash=item36041a32aa:m:m_p3XU3nyRnqvmgYJpsrheQ&vxp=mtr

now it doesn't have a sensor for battery temperature, it does have adjustable voltage that is useful
and it has the remote sense wire, which is mandatory for what i have outlined so far.

the price is certainly attractive! at $39.99 with free shipping?  hard to beat that and in my opinion
something that is worth a shot with this sort of project/prototype.

actually this is the regulator i looked for high and low 10 years ago to use in testing,  and i am convinced
that even though it isn't programmable, and doesn't have all the other bells and whistles, it does have the basic
requisites to use in this application.   even if it didn't fit the back of the alternator you have, it could surely be remote mounted to a panel and wired from there?  i think i am going to order one, and maybe work with it this winter in testing.

the only wire used off this regulator that would be connected to the alternator would be the two field wires, the red and black with eyelet connectors would be connected to a 12volt source that is isolated from this unit, and its 36volt battery bank such as the starting battery.

so connect the black and red with eyelets to the 12volt starter battery,
connect the sense wire to the first battery in the 36volt string
connect the field wires to the brush holder,
mount the regulator to the rear of your alternator

start her up, raise the rpm up to where you get charging, at 36vdc nominal, and adjust the regulator voltage to whatever you like, such as 43.3vdc? or so. and you should be golden
most of these regulators taper back the output as the alternator gets hot, so there is some overheat protection.

remember that by adjusting the regulator you are adjusting what the regulator see's at the sense wire, and because the field is 12v nominal and is powered by a 12v regulator which is fed by a 12v isolated source,  the system really doesn't know about what is happening at the output side of the alternator, but has control over that because the battery being charged (36vdc nom) is made up of 3 batteries the first of which is being monitored....

if over time there is an imbalance between batteries, which really should not be a problem, all you need to do is move the weak sister into the number one battery position and let the system sense from that battery and it will them be pulled up to where it needs to be to equalize.

bob g

[mobile_bob]

before you buy the 40 buck unit, let me look into it further

it has the needed sense wire, which i had wrong, it is the "red" wire with an eyelet connector

apparently the ignition wire "purple" is the wire that powers the regulator,  which seems right to me

i think i will order one, to check fit and how it works,  and will let you know as soon as i get it and have a bit of time to do some testing.

looking further it looks like walmart even sells it for 35 bucks! hmmm
https://www.walmart.com/ip/NEW-REGULATOR-FITS-MERCRUISER-INBOARD-ENGINE-198-228-255-330-340-5-7L-7-4L-898-5-240/165067336

i am not sure if the unit will bolt on in place of the oem regulator,
the unit i am looking at here will fit the motorola unit,  the motorola 8mr series was the grand daddy of the 110-555jho and your alternator marketed by prestolite and now leece neville..  these units are very very close sharing the dna of the motorola however the regulator might, and i mean might have a slightly different bolt/screw pattern.  however this does not preclude its use as a panel mount regulator for the proposed purpose.  you would simply remove your oem regulator, disconnect its wires internal and external and tape them off, connect new field wires to bring out through the grommet and reattach the oem regulator as a dust cover... or remove it and go get a blown oem regulator and dig out the potting compound and remove its innards and clean up the housing to use as a dust cover... i have done this a lot.

by the way,  it appears like alibaba has chinese suppliers of this regulator for between 1.5 and 3.5 bucks in quantities of 200 units.    i guess if the time comes we get enough bodies back on the forum needing to develop engine driven high efficiency chargers for 24, 36, 48 or whatever... maybe we could do a group buy, or maybe there is a chinese company that would sell in quantities of less then 200 units...  crap at 1.5 bucks and 200 units it would still be less than a balmar even if not as advanced and not having all the bells and whistles.

the bells and whistles to a large extent could be added with a micro controller and a i/o relay board, maybe a couple temp sensors or even temp switches like the temp snap switches... we really only need over temp cut out or limit switches for two states, ok run and oh hot don't run.  i think there is much that might be done in this area that would be quite useful
and would not be tied to just one type of alternator,  this system would work with many other types so long as you can get access to the field connections internally and the rectifier bridge can handle the higher voltages or be able to swap out the diodes as previously stated for higher output.

fwiw


thanks
bob g