SW-EM Alternator in 6V Vehicles

Alternator in 6V Vehicles (...it's possible!)
Feb 2023 R. Kwas, revisions on-going. Comments added.

The info here is directed to those with 6V automotive electrical systems, who might consider replacing the Bosch Generator with an Alternator such as the Delco 10SI.

A Generator output is very much dependent on Engine RPM...so is an Alt really, but less so. This graph shows the Alt is already putting out 30A, that's half its rated output(!), at 2000RPMs! ...yes graph is for a 12V Alt, but the curve is quite applicable to a 6V sys also!

Alt output vs RPM graph. Note "Generator" Shaft RPMs are plotted, and since the Alt Pulley is smaller (at about 2 1/2" OD compared to the Crankshaft pulley about 6"), there is a further multiplication of engine RPMs factor. [PLACEHOLDER FOR SPECIFICS AFTER PRECISE MEASUREMENT OD OF ALT PULLEY TO OD OF CRANKPULLEY!]

For those owners who like the thought of the simplicity of an Alt...solid state VReg, simple Brush replacement, and increased low RPM output of an Alternator, but want to keep their 6V elec sys, the following info may be of interest:

1. The chemistry and State of Charge, even temperature, of the battery, and also...
2. A Voltage reference in the VoltageRegulator (either electro-magnetic in early Gen based Chg Systems, see: Cut-Out Contact, or electronic in later Alt based Chg Syss).

Here is the magic VReg Module with which a Delco Alt can be made into a 6V Charging System!

By simply installing such a VReg into the 10SI Delco Alt, a 6V Alt can be realized!

Notes of a conversation with Randy Dubois, highly experienced alternator expert and proprietor of Quick Start/Alternatorparts.com:

Note on the frame capture above, that this VReg is for a "One-Wire"/Self-exciting Alt. This means that no external Field excitation needs to be provided. However, fact is that all Alternators will self-excite, connected up as a "One-Wire", with NO external Field excitation. Self-excitation will be provided in that case, instead, by the residual magnetism of the Armature, and this will be used to make ever-increasing output, up to the full output (this is called "Bootstrapping").

However, to function with self-excitation, they require an initial elevated RPMs...they will not get started generating power in low RPM applications like industrial or farm installations, here, if the engine can not be reved for some reason, they need an initial external excitation. What is sometimes added on farm equipment, is a momentary button which applies initial battery power to the Alt (field) to get it started...once started generating power, it will then continue to self-excite (by way of the "Diode Trio", see VReg circuit Analysis below) for the remainder of the time it is turning. In Cars, where low RPM/no output is less of an issue, and the engine and Alt RPMs are much higher, starting the power generation process by providing an external excitation is not necessary, making the "One-Wire" a simplicity selling point, for those installers scared of more than one wire! There is always a downside, and in this case the simplicity of the "One-Wire" brings with it the loss of the charging control or "AMP Indicator". It's better to bring in a second wire for the Field excitation...one can then also keep function of the "AMP Indicator".

How dOEs one recognize a "One-Wire" Alt? In this picture of the back of such a unit, there is a rubber plug covering the the VSense(2, also L or B+) and Field(1) connections on the VReg, such that it is not even possible to provide external excitation for the Field. I bet with removal of this rubber plug, the connectors would again be accessible, and the Alt would be operable as a normally connected three-wire!

...so what is that third wire all about? Answer: It is the VSense connection, by which the VReg senses the Battery/Sys V. In simple car electrical systems where the wiring is not very long, it can simply be connected to the B+ output terminal for Local V Sensing. Local and Remote VSensing is further explained here: https://www.sw-em.com/altkit_additional.htm#Remote_Voltage_Sensing

As an example, this Alt has already been set up with one of those VRegs, so is ready for installation providing the mechanical mounting aspects have been addressed. For a B18/20, this can simply be handled by a SW-EM Kit bracket...for a B16 it will require a suitable mount, as was fabricated here: AC Delco Alternator installed on a B16 UPDATE 2023 - See also below: Alternator Conversion of a 6V 444 Volvo

Where we normally speak of 6 or 12 automotive or even 24V (truck) electrical systems using the nominal Voltage values, but when working with the VReg, we must get more specific and accurate and use the actual lead-acid cell voltages (2.1V per cell, so 6.3, 12.6, and 25.2V respectively).

The observant reader will notice that on this partial page frame capture for the various VRegs, the specific V Set-points are specified to the tenths of a V(!), and it is always some factor above the fully charged Batt V, because this difference in Voltage is what actually drives the charging current! The bigger the Voltage difference, the more accommodating for system VDrops it is. These can occur due to for instance wire lengths in a particular installation.

Note the variations in Voltage Setpoints for even 12V Sys VRegs. I would explain that by the differing VDrops which might occur in various VReg installation/application.

Adjustable Voltage Regulators: The remote V Sensing option of the Delco as mentioned above, addresses the needs of a wiring system where long wire lengths or VDrops make this the preferred configuration. I am aware of an adjustable VRegs not for Delco Alts, but for the Bosch Alternators used in the later Volvo cars...apparently 240 expert Dave Barton has recognized VDrops and system inadequacies which occur in this series, and by tickling the Voltage Setpoint up a bit, these are addressed well and when installed, result in a better elec system function while keeping the Battery well charged. See: https://www.prancingmoose.com/AdjustableVoltage.html

The VW Vanagon community, where a long wire distance, from the rear-engine to the Batteries (dual - House and Starting, we're talking about a camper configuration here!) under the seats, is easy to recognize, these Adjustable Regulators have also been shown to be popular. By raising the Setpoint of the Chg Sys, a higher Voltage results to keep the Battery well charged. See: https://www.thesamba.com/vw/forum/viewtopic.php?t=363115 Of course, I do need to point out, and warn(!), that raising the Chg Sys output V should not be used as a symptom-remedy without proper troubleshooting and engineering to address a VDrop across an inadequately sized cable or poor in-line connection! It is much preferred that V-Drops be located and minimized, be it by correcting electrical joints with high Resistance, or inadequate wire-gauge. A proper engineering investigation and understanding of the root causes is ALWAYS preferred to a shotgun approach, as the shotgun approach can bring with it unintended consequences!

Charging sys including VReg internals published by Delco, and analysis of function and transistor currents:

Note that the important control currents all route through the VReg ground/chassis terminal. This emphasizes the critical importance of a good, low resistance connection here. If for instance, there exists a series Resistance in this current path, any voltage developed across it will certainly influence the electrical action and accuracy of the internal control circuit, probably manifesting itself in raised Sys V as this inadvertent V is added to the intentional internal control V. In the best case, a slightly higher Sys V will result, in the worst-case, a VERY high Sys V, with burned out bulbs, and an over-charged/acid spewing Battery as a result.

My thought has been to replace the voltage reference element within the VReg with another, strategically selected for a 6V Sys, and by this simple action, followed by installing that modified VReg into an Alt, and then installing that "6V Alt" into a car, giving it the benefits of an Alt even with a 6V Sys.

Enter Mike Stricker WA1-SEO, long-time friend and very qualified and highly experienced technical reference, who once again lent a technical helping hand with a Simulation of the VReg circuit:

His comments: "Neither transistor is a pass element. They are operating as switches (cutoff or saturation).
Q1 may be a Darlington for extra gain. I chose random component values that I thought would
be OK for the purpose of analysis. R5 [Correction: R4] just simulates the field winding resistance (guess [of 5Ohms]). "

Analysis for Vz of 6V: It is clear that D1 Vz sets the VReg switching V, and that with a 6V Vz, the VReg would control the Field to be energized any time the System V was below that, and as the sim shows, this is not a linear function, but strictly an ON-or-OFF function.

Analysis for Vz of 15V: With Vz at 15, the Field remains energized all the way up to that V.

...so for the 7.7V Set Point specified for the 6VReg above, the D2 component would have to be a 7.7Vz diode.

The sim confirms my understanding of the VReg function, but since I have also located a source for these 6V VRegs, I don't need to modify any VRegs!

An actual report of an installation to confirm the theoretical is always good. I ran into this a while ago...it might also be of interest to owners of vintage Volvos with 6V systems, who similarly don't want to convert the entire elec sys to 12V, but who still want to take advantage of the simplicity, plus solid state VReg, and high output (particularly at low RPMs) of an Alt. [UPDATE Oct 2023: Read on for Alternator Conversion of a 6V 444 Volvo ]

The following are notes from a 444 6V (B16) Alt Conversion. The conversion was performed by Eric H, under my mechanical and electrical guidance, and he has kindly provided pix and observations. Eric has also consented to being contacted per e-mail: ehamerstrom AT catskill DOT net

Per my suggestion, a 6V Alt was obtained from Randy DuBois, at https://store.alternatorparts.com, this Alt was installed using original Generator bracket PLUS a modified Universal Alternator Mounting Kit to obtain correct Fanbelt alignment.

At first start after the conversion, system V measured at 7.1V so the 6V LED Headlights Eric had previously installed now work fine, and much better than they did with the OE Generator before the conversion, so he is very happy with results. Those "expensive" headlights not working well because they were not being supplied their rated Voltage was in fact, a major contributing factor why he decided to go ahead with the conversion, although he wanted to "keep it otherwise original".

Additional Info and Comments by Eric:

" The [6V LED] headlights came from "Vintage Car LEDs" but their website says the 6V model (VC6V) is discontinued. I suspect it didn�t sell well. A quick internet search shows a similar but slightly dimmer version from Octane Lighting:

https://www.calcarcover.com/product/octane-25417-6v-headlight-pair/6220? [I nor Eric have a relationship with this outfit. Their info is presented here strictly as a reference.]

These are 4000 lumens vs. 6000 from Vintage Car. There seem to be other options but I didn�t take a lot of time to research it. My new bulbs didn�t work well with the original generator, but the 6V alternator does the trick.

I want to keep the car original and not convert to 12V, and now nighttime driving is better! "

Conversion Highlights:

The following is not a procedure, but are highlights of work which was performed, in conjunction with standard cautious shop practice. Neither Eric nor I can be responsible for all your actions, particularly those which result in damage or injury! Work safely on your vintage Volvo!

After removal of OE Generator...OE Bracket is left in place on its soft-mounts (which are not absolutely necessary with the Alt, but can be left in-place).

The Universal Alternator Mounting Kit was obtained for evaluation. It includes info for Ford, Chrysler, and Delco/GM installation variations. the bracket is a generally beefy construction, but supplied only with bolts, split lock-washers and normal hexnuts. [On closer examination, included are Grade 2 china-trash bolts with normal nuts, all of which I recommend exchanging for Grade 5 bolts and Nylock Nuts if the installer wants to add a level of confidence in the installation! Given the hi-vibration environment an Alt will live its service life in, and knowing that "lockwashers" don't lock (see following!), at the very least, a chemical threadlocker on the supplied hardware is recommended!]

�The typical helical spring washer � serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking.�

Unmodified UAMK is temporarily secured to the OE Bracket as seen here, for a fit check.

It was found by Eric, that two Modifications were necessary for a proper fit onto the B16.

UAMK in place on OE Gen Bracket. [I really recommend the low quality, nonself-locking front and rear pivot bolts included with the UAMK be replaced with Grade 5 hardware and Nylock self-locking Nuts at time of installation!]

UAMK Mod 2: A clearance arc must be ground into front bracket tab as shown, to eliminate interference with Alt impeller, and provide running clearance.

Removal of some bracket material is necessary at the front bracket tab for a clearance arc. Visible is also the unmarked (Grade 2!) junk mounting hardware.

UAMK secured on OE Bracket, and Alt is installed on modified UAMK.
Evident are the Alt mounting boss, and Spacer Sleeve supplied with the kit. The UAMK should be adjusted such that their combined length is able to be tightly clamped between the bracket tabs, after tightening Fanbelt. Self-locking nuts are strongly recommended here! [Note that the two bolts securing UAMK to OE bracket would allow pivoting affecting Fanbelt tension, so these bolts being tight and not allowing ANY movement is as crucially important as the Alt pivot bolt itself! I also recommend protecting the bracket from rusting with paint before final installation]!

The Fanbelt Tensioning Bar must be modified with a slight "S" Bend to achieve good alignment with Threaded Adjustment Lug of Alt.

Alt in place and Fanbelt tightened. Good alignment of Fanbelt is evident, as is the "S" bend necessary in Fanbelt Tensioning Bar. Eric reports he used a Fanbelt sized 3/8 x 35". [...that works out to a Gates PN of 7350.]

Adjust UAMK such that by tightening the Pivot Bolt AFTER tightening Fanbelt and securing Fanbelt Tightening Arm Bolt into top of Alt, Alt pivot is tightly held and secured from ANY AND ALL movement or vibration. The nut securing long Alt pivot bolt should also definitely be a self-locking type.

Just as in the SW-EM B18/20 Alt Kit Installation, Alt MUST be solid with Bracket(!), and Brackets (in this case BOTH!) MUST be solid with engine! Anything less or a situation allowing movement is preprogrammed to fail! You have been warned!

I have gone to great lengths and some expense to compile this information, so the file will be forwarded only upon receipt of an "Engineering Charge". Thank you for your understanding in this!

External material sources are attributed. Otherwise, this article is Copyright � 2024. Ronald Kwas. The terms Volvo, Bosch, Delco and Quick Start/Alternatorparts.com and Steinertractor are used for reference only. I have no affiliation with any of these companies other than to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here. The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, or worshipped, at the readers discretion. As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles, and future!

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source. If you don�t, you�re just a lazy, scum sucking plagiarist, and the Boston Globe wants you! As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the unique metaphor and probably (likely) wise-a** comment.