14.5V Voltage Regulator Needed
 

My car uses a Bosch 0-123-510-040 115Amp alternator, and the regulator being used now is a 14.1V unit, Bosch part number 1-197-311-242. Since 14.1V is not nearly enough to fully charge the battery (14.4~14.5V is more like it), it is my intention to raise the output voltage of the alternator to 14.5V with the installation of a WAI IB387-1 voltage regulator, or equivalent. Will 0.3~0.4 volts more make a difference? You bet! and will cure a chronic undercharged battery condition.

I have not been able to locate a dealer that sells this regulator in single quantities or even over the internet. Anyone have any tips of where to order it? It doesn't have to be that exact same model, which I located on a WAI distributor website some time ago and is supposed to be the correct one for my application. Any other brand of regulator would also be fine, as long as it properly fits my alternator, and has a set output voltage between 14.4 and 14.5V.

BTW. already tried the diode trick mentioned elsewhere, but it didn't work. Besides its not the best solution anyway, in my opinion.

Thanks.
-Alex

perhaps you should also check the main grounds.take a good voltmeter and set to 200ohm scale then put one probe at centre terminal on batt ground and the other on a cleaned surface on the intake any more than 0.3 ohms is too much.this may involve the main strap under the car from trans bellhousing to body[usually mounted to a starter bolt for obvious reasons].

Hi, thanks for the input, but as I stated before, the main reason I want to replace the voltage regulator is because it is factory set for 14.1V which is as far as the system voltage will go. Problem is that this voltage is not hight enough to fully charge a Lead-Acid battery which requires a voltage of 14.4~14.5V to reach a full charge.

Older voltage regulators used to conservatively be set to a lower then optimum voltage (not sure why), and there are even some older Benzes that have regulators with a set point as low as 13.8V. Not good for the battery life as a chronic undercharged condition will promote sulfate formation on the cell plates and reduce battery life.

I dont know what diode trick you tried but i have always been able to get regulator voltage up .5 volt by putting a diode in the wire to D+,perhaps there is something different about your alternator but it has always worked for me.you are aware that the diode has to be placed in the correct polarity? Connect the diode to the wire that goes to D+ and use a test light to be sure the voltage is getting thru the diode before you connect to the D+ terminal. My $.02 Don

Do you have 14.1 volts at the battery? If so or if not, you have other problems.

14.1 volts is completely sufficient to charge your battery. If you have 13.5 at the battery, that's enough.

You're chasing ghosts. Find the real problem.

Well Matt, I suppose this is your personal opinion, which I certainly respect. But if you take a minute and check any of thousands of battery charging guides for Lead-Acid batteries available online you will find that, yes, a battery can store a charge while being applied the voltage you mention (13.5V), BUT it will never reach 100% charge state this way. A Lead-Acid battery in fact can only be charged to 80% of its capacity (at best) when the terminal voltage reaches 14.4V (or 2.4V per cell), and only THEN if this voltage is held constant for some time it will charge up the remaining 20% of the battery capacity. So if your alternator output is below 14.4V, you will have a chronically discharged battery that can never reach full capacity. This condition will cause Lead-Sulphate (a normal byproduct of battery chemistry during a discharge cycle) to accumulate on the plates, a process better known as "Sulfation", which slowly but surely robs the battery cells of useful plate area exposed to the electrolyte, until the battery is literally choked and is no longer able to crank the starter.

To fully charge a Lead-Acid battery involves a two step process. The first step (called the "bulk charging") will charge the battery all the way to 14.4V, from there on it will go to an "absorption charge" mode. A battery can only be charged up to a point in bulk charge mode, and it is impossible to reach a 100% charge state without going through the absorption charge step. If your electrical system only reaches 13.5V (or 14.1V in my case), it becomes more then obvious the battery will never even get close to the absorption charge step.

That is the reason why most if not all of the so called "Intellingent" or "smart" battery chargers feature a two (or even three) step charge process. First they bulk charge the battery in constant current mode (senses voltage increase), then when it reaches about 2.39~2.4V/cell the charger will switch to constant voltage mode (senses charging current) until the battery reaches 100% capacity. The charger will know when this point has reached because charging current will taper off. The third step most of the better chargers also incorporate is a float charge that will keep the battery at a nominal 13.4V (@ 25 deg C) since the cell voltage varies .022V (or 22mV) per degree C. This happens because the cell's internal resistance decreases with temperature, and the charger should ideally adjust the float voltage according to ambient temperature. If you ignore this, you will apply too much voltage to hot batteries and fry them, or insufficient voltage to cold batteries and so not fully charge them. BTW, most BOSCH voltage regulators have this temperature compensation build in, but still have the lower then optimum voltage setting shortcoming.

Since the only charger available to a Lead-Acid car battery is the alternator, this is a far from a perfect situation. It works well if the battery is not deeply discharged. But the alternator being essentially a "dumb charger" tends to overcharge batteries that are very low and the overcharge can damage the battery. Hence this is another reason why it is important to keep your battery at an optimal charge level which can only be attained if your electrical system is capable of reaching about 14.4V.

Hi Don,

Thanks for sharing your experiences with the diode mod. In any case it makes perfect sense and it should work, because the regulator would see between 0.5~0.6V LESS due to the diode's voltage drop.

When I first did my own test, I followed the instructions found in an article that involved in this case lifting the GROUND terminal of a Bosch regulator through a diode, which technically should attain similar results. But for some reason as I mentioned earlier, it did not work for me, and I did double check that the regulator body (ground connection) was completely isolated. I'm guessing the regulator circuit itself didn't like this, and stopped working altogether, there was no voltage output from the alternator at all. The article is here:

http://www.detomaso.nu/~thomast/alternator/

At the time I though about connecting the diode in series with the D+ terminal as you suggested, a much more elegant way to trick the regulator. But in my particular case it would be very tricky to do. There is already very limited space in the area where the regulator is mounted inside the alternator, and the regulator D+ makes contact with a hidden terminal inside the alternator. Furthermore to complicate matters, the D+ on the regulator is kind of a springy tongue that compresses over the hidden terminal inside the alternator, so no way to install the diode anywhere in between.

Someone suggested using an old gutted regulator just to get at the terminals inside the alternator, attach two cables to it, and use an external 14.4~14.5V regulator. This might have worked for me, but I neither have a bad regulator on hand (don't even want to consider gutting a good one), and I'm not too fond of the idea of using an external regulator.

Anyway, thanks again, appreciate your two cents.
-Alex

I tried one of the after-market 14.5V VRs a few yrs. ago - don't recall the name. It was not Bosch. The brand has been discussed here numerous times. I was after the same thing you are.

The darn thing didn't fit right.

Decided to simply replaced the alternator which comes with a new VR - Bosch alt. My origianl was 80 amp. Bought a 100 amp Bosch unit.

Lo & behold. I started seeing 14.30 at start-up on a cold motor vs. the original 13.90 - 14.05.

Just my 2 cents.

Hi Mike,

Nice to hear about others that share the same goal. Interesting to find out that newer alternators apparently now do include a regulator with the required higher setpoint voltage . Seems manufacturers are finally cleaning up their act, and less batteries will end up prematurely in the landfills.

My alternator is a S-Class 115-Amp model, I believe made specifically for the 93-94 model car. Maybe I'll give the parts guy a call and ask him what the set voltage of the replacement regulators are. Mine clearly has written "14.1V" on it, so hopefully it will be easy to determine the spec of any other Bosch regulator currently available over the counter.

It seems most of the aftermarket 14.5V voltage regulators out there are junk made in china, so I'm not too surprised that yours had a fitting problem. Nowadays one can't even trust the familiar yellow Bosch box, even if it states "Made in Germany". It seems the chinese are counterfeiting everything. Just the other day I purchased a couple of common Bosch horn relays (the black cube ones with the mounting flange), and they turned out to be all cheap stuff inside, even tough they where individually packed in nice original looking Made in Germany" boxes. I compared the insides to a known original relay, and there was a BIG difference in quality and workmanship.

BTW, there is a parts catalog of Bosch alternator parts in PDF format that is pretty good for visual references:

http://site.amscovf.com/boschalternatorparts.pdf

Actually the VR that came with my Bosch reman alternator was the same VR I had replaced before. The alt. I bought was 100 amp vs. the 80 amp it replaced.