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Old 16-07-2018, 13:39   #1
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Converting Delco 28Si to external regulation

In my other thread (alternator choices) I was convinced to use a bus alternator rather than an other choice. One of the real kickers for me was the cost of a Delco 28Si 200 amp OEM alternator (less than $400 including shipping). And that I have the room in my engine room.

I went ahead and bought one and it has arrived. They are big! and that is good. Even though this is a 200 amp alternator I expect to run it at a "reduced" output of around 120 amps but we will see.

I will be driving it with a K6 (6 ribbed) serpentine belt which the engine is already fitted with (see the thread for that as well). The engine is a Perkins 4.236

The first task is to convert the alternator over to external regulation. This is not a hard task but for those who do not want to do it I would steer you to Mainesail who offers a beefed up version of the 28Si with the conversion already done.

Here are some photos of the alternator and the internal regulator.
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Old 16-07-2018, 13:52   #2
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Re: Converting Delco 28Si to external regulation

My plan is to remove the existing internal regulator and make a G10 epoxy board in the same general shape of the regulator. This board will have the 2 connectors (posts actually) that I need.

Because the field winding is grounded on one side I can just bring the other out to an external regulator. This is good.

The other needed wire is the stator output so that the alternator can drive a tach.

G10 board (green fiberglass) is around for backing plated and other such things. It is very strong and stable. And darn if I can find any locally.

In any case I wanted to trace the internal regulator footprint and then cut out a piece of G10 to match. Not having any G10 I just took some fiberglass cloth and epoxy and made my own. It came out brown because the hardener is old. It does not change anything other than the color I've been told.

I used 8 layers of cloth to get a 1/8" board for the mock-up.

I poked around and trimmed the board to fit and cut out an area near the brushes. After doing so I thought that opening up that area (which the internal regulator would cover) increases the cooling air flow there... and reduces the air flow through the positive diode heatsink. This may not make much difference but then again who knows without measuring.

When I get the G10 board I'll transfer the mockup shape to it and likely make it cover nearly the same area as the internal regulator.

The first photo is rough fitting the mockup board. The hole in the board is from a standoff support on the regulator. It is only needed to get a faithful tracing of the regulators shape.

The second photo shows where I have placed in the connector posts for the field and stator connections.
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Old 16-07-2018, 13:55   #3
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Re: Converting Delco 28Si to external regulation

Here is a photo of how the mockup fits in the alternator with the shield installed.

The plan is to wire the connector posts to the internal connections using some crimped connectors.

The only tricky part is getting the field connector but that is for a later posting.
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Old 17-07-2018, 22:04   #4
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Re: Converting Delco 28Si to external regulation

Well, I stopped by my local Surplus Gizmos store at lunch today. Digging around I found a spool of SF2/SEW-2 wire. This is 200 degree C wire with silicone insulation and a woven fiberglass cover. The wire is tinned annealed copper. 1 foot of 14 gauge wire set me back $0.38.

In another bin was a bunch of PC boards. As I stated I was having a hard time sourcing some G10 epoxy board stock and ended up making my own for the prototype. However, G10 is also known as FR4 which is "flame retardant". And PCB are made of G10.... So anyway I found a PCB that had a large area without a ground plane or any traces on it. That set me back $0.50.

Less than a dollar for the supplies. Everything else I have somewhere.

Moving on....
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Old 17-07-2018, 22:27   #5
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Re: Converting Delco 28Si to external regulation

... to the brush contacts.

The first photo shows the 28Si brush assembly. You will notice that 2 metal straps come out of the brush assembly. The lower is in contact with the frame and thus this brush is grounded (to the frame). The upper comes out and is sitting on top of an insulator. We will be connecting to that contact.

Photo 2 shows that I have a ring terminal that has the center opening (1/4") that matches the brush ring contact. Stock item it is.

Photo 3 shows how a nylon insulating bushing will fit in to the ring terminal and prevent the ring terminal from making contact with the (grounded) mounting screw.

Photo 4 shows the bushing (upside down from how it is int photo3). I just happened to have a few of these sitting around from when I worked at Tektronix. (man that was in the '80s). If I remember right they were used for mounting power transistors.

The bushing was a bit thick so I sanded it down till the hub matched the ring terminal in thickness.
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Old 17-07-2018, 22:38   #6
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Re: Converting Delco 28Si to external regulation

Time for assembly.

The first photo shows the G10 epoxy board cut to size and shaped with the field and stator posts mounted. Note the 2 nylon washers.

Interestingly the ground (unused in this mod) mounting hole is higher than the positive diode frame. I inserted 2 nylon washers that I got at ACE hardware to make the board mount without stress.

In photo 2 I've mounted the board including the nylon washers and connected the field jumper wire to the field connector. (as noted in the last posting)

Photo 3 shown the stator and field jumpers installed. The stator connection is soldered. For this I took a female spade connector and bent it 90 degrees. I also adjusted its shape so that it made a good mechanical connection to the stator pin and then soldered it.

I used some 2% silver solder (high temp too) that I also had laying around from my Tek days.
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Old 17-07-2018, 22:44   #7
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Re: Converting Delco 28Si to external regulation

Lastly the alternator is all assembled and some checks have been done to be sure that there are no shorts in the field connection.

The first photo shows the end results....


Next on the agenda is working on mounting the alternator and testing it. I'll have to wait for the weekend. (Damn that day job)

I have an existing Balmar alternator with a 1" mount on a 2" mounting onthe engine. It kinda looks like I can adapt the mounting to the J180 of the 28Si without too much of a problem.

Famous last words.
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Old 17-07-2018, 23:41   #8
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Re: Converting Delco 28Si to external regulation

Very cool, good job!
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Old 18-07-2018, 14:18   #9
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Re: Converting Delco 28Si to external regulation

If I understand it correctly, you chose to remove (rather than bypass) the internal regulator simply in order to increase internal airflow?

I see the new ones are made by DelcoRemy (one of the "sons of Delco") and they are offered in 160A with 180A/200A optional models. The nice thing is, we have toll-free real technical assistance from DelcoRemy in the US, they should readily answer any questions about sustained load output, etc. for the unit.

If you have an IR thermometer, one thing to check out if the actual operating temperature of the diode pack. Every 10 degree rise in temperature cuts the operating life of components in half, so you can make your own decisions about how hot to run them.
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Old 18-07-2018, 14:26   #10
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Re: Converting Delco 28Si to external regulation

Air flow was not the most significant thought.

I did not want the internal regulator and the external reg to interact. Plus there was no easy way to bypass the internal regulator.

Thus I removed it to be sure that nothing unexpected happened.

It is easy enough to put back in should need arise. The hard part is storing the internal regulator somewhere that you never find it again.
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Old 23-07-2018, 13:33   #11
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Re: Converting Delco 28Si to external regulation

Well with a little fitting I was able to get the 28Si fitted to the existing 2" mounting. A few washers and spacers got the alignment right. It still needs work to be sure that the bolt stays tight but I'll get to that.

The existing adjusting arm is not the right shape so I picked up a cheap 10" aluminum turnbuckle at the local hardware store. I bent the eyes to hold the bolts on the engine and alternator so as to fit. It needs a down angle to match the alternator and still make it under the expansion tank.

I'll get a better bolt and weld some eyes on at the correct place. Sooner or later.

As it is it adjusts well but does not have space for the lock nut.

As you can see from the photo I kept the plug for the Balmar alternator and made 2 small jumpers from the alternator (field and stator) posts to spade blades to insert into the connector. I'll likely do 2 more things here - 1) make new jumper wires with blue and white insulation to match the cable to the regulator. 2) come up with a set of tie wraps to "lock" the connector and jumpers together.

OK, moment of truth (keep the orange smoke in the wires) time.

Firing the engine up the Balmar MC-612 does its 45 second wait then soft start ramp up. The tach is reading low but that is to be expected (number of poles etc). the amp meter starts climbing and peaks at about 165 amps with the regulator set for 13.9 volts.

My house bank is 700 AH of LiFePO4 at about 90% SOC.

A quick check with the IR temp meter shows the alternator pulley is running hot (130 degrees). This indicates that the belt is slipping a bit. Adjust the tension and the alt pulley temp drops. It eventually stabilizes around 90 to 95 degrees F.

This is more current than I want from the alternator anyway so shutdown and get out my magic (magnetic) wand.

I reset the bulk voltage to 13.8 (from 13.9) and the absorb voltage from 13.8 to 13.7 (not sure why I did that... Just in the moment.).

Float remains at 13.2 volts.

Amp manager was off and to reduce the max current set it to 150. My manual says that 185 is 75% field current, 125 is 50% thus 150 is about 60% or around 120 amps.

Starting the engine up again I get 130 amps which quickly drops down to a comfy 80 to 90 amps. The batteries are near (what I'm calling) 100% SOC and with the Bulk voltage at 13.8 I do expect the charge to be dropping.

out of time....

I'll have to go over all of the regulators parameters and verify that we end up in float. In the last test we went from CC to CV mode in that the battery voltage reached 13.8 and the regulator kept it there with the current (slowly) dropping.

3.4 volts per cell (13.6 volts) is kind of a magic number. Charge below this and you get very much reduced capacity. Once you hit 3.4 VPC you end up with near 100% capacity and very little difference from 3.5 or 3.6 VPC. At least it appears so from some LiFePO4 discharge curved I've seen.

Anyway - Success! in installing a Delco 28Si with external regulation on a Perkins 4.236.
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Old 23-07-2018, 13:38   #12
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Re: Converting Delco 28Si to external regulation

Last thoughts:

I'll need to move this into "production" mode and take care of the noted loose ends.

I might install an automatic belt tension spring - I do worry about over doing the belt tension.

Now I have the rebuilt 100 amp Balmar and Hehr alternators (both rebuilt this year) to sell or keep as spares. At least until I have full faith in the 28SI installation.

Oh, I should add that the 28Si running 85 amps at 1000 engine rpm was reading a cool 125 degrees F. for the 30 minutes I ran it.

And that the Tach was adjusted to read correctly.
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Old 26-07-2018, 16:27   #13
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Re: Converting Delco 28Si to external regulation

Beautifully done and documented.

My engine has a single 1/2" vee belt, and between that limitation and a lack of room, I am restricted to a small case alternator.

I first replaced the original (as the boat came to me) Delco 10DN based Ample alternator with a Chinese knockoff of a Delco CS-130. Disassembling that alternator to bring out the field wire was more of a problem than your 28SI as the brushes and regulator were inside the alternator case (not outside as is your 28SI) requiring me to de-solder and then re-solder the three field connections to the diode pack to get to the brush assembly. I left the internal regulator in place thinking that with no power connection the regulator would do nothing.

A few years later, I replaced the CS130 with a Delco Remey rebuilt CS130D for better cooling. That alternator, like yours, has two internal fans and has the regulator, diode pack, and brush assembly outside the alternator case itself. That made bringing out the field wire much much easier. Again, I left the internal regulator in place.

I think one of the advantages of both your 28SI alternator and my smaller CS130D is that the diode pack is outside the alternator case. While it is not the same thing as a remote rectifier, it is not inside the alternator case. It is easier to get to for modification to external regulation, but perhaps more importantly it is in a cooler environment.

Thinking that if the major heat generation and heat failure point is the diode pack, I wonder if the temperature sensor from the regulator should be mounted on the diode pack rather than on the alternator frame as Balmar recommends.

Bill
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Old 26-07-2018, 16:37   #14
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Re: Converting Delco 28Si to external regulation

Thanks!

Where possible placing the alt temp probe on (one of) the diode heatsinks is the way to go. Better reflection of the temp as well as lower thermal mass to quicker to respond to changes in temp.

On the 28Si there is that large B+ terminal which is attached to teh positive diode heatsink. It is steel (magnetic) and I have thought of replacing it with a copper one instead.

In any case attaching the alt temp probe on the B+ is a better way to go than to the case. The sensor of course should be internally isolated so being at B+ would not present a problem. Stacking order should favor power out.
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Old 05-10-2018, 16:52   #15
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Re: Converting Delco 28Si to external regulation

Nice job!

So basically, is this how you hooked it up?
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