Very interesting reading this thread. The ideas here are amazing.

I like the idea of the 600V to 120/240 VAC converter and an automatic battery charger. Safety from overcharging, producing dangerous gas, etc. is important IMO, when you have visitors on the cars. You can even buy an automatic battery charger circuit board 120/240VAC to DC (adjustable) on eBay for a few bucks. Not overly recommending it, but it is possible.

[EDIT] Here is a link for an adjustable 12-36VDC battery lo/hi voltage cutoff circuit:
https://www.ebay.com/itm/XH-M609-DC-12V ... 3741330175

At $4.99 It should be within anyone's budget :).


One important consideration for the Edison batteries - they have a negative temperature coefficient. That is as they charge up their internal resistance decreases. Thus a simple constant voltage charger circuit will "run away" and overload/overcharge them. On the old Waukesha Enginators, they had a separate panel specifically for when Edison batteries were used.

----
I have 4 8V lead acid golf cart batteries that are charged by a Waukesha Enginator (running) or a transformer/rectifier (station power). The car is the old Milwaukee Road Dynamometer car at the Illinois Railway Museum.

This is waaaaay out of my league but I'll throw something similar out there that may be workable or get you thinking....

Start with a 600 to 36 volt converter something like: https://absopulse.com/750vdc-high-input-voltage-railway-dc-dc-converters-transit-mining-vehicles/. Much smaller package. This one may/may not have the needed current available, don't know your requirements. No clue on the cost, though. Could be way out of line with your budget.

Automatic charging circuits are relatively simple affairs once you get past the initial power supply portion. If you have an electronics guru or technical school that'll take that portion on, you might be cooking with gas.

Just a thought...

OK, my two cents, again.

If you are a *museum* then part of the mission is to preserve, to the extent possible, the original
historic fabric. To me, that also includes preserving the obsolete and inefficient technology of the
day.

Solutions that involve solid-state converters and other modern electrical components might be the
best answer for a transit agency, tourist railway, or "heritage" trolley operation where the primary
mission is not historic authenticity.

If the original charging system for these cars was M-G, the best practice from a museum standpoint
is to either rewind the M-G, or as one poster suggested, get an M-G from a PCC car (there are many
of these out there). Then you'll have something which sounds and operates almost like the original.


Regarding the resistive charging scheme: if that's not something the cars ever had, I don't advocate
for it. But as for the safety aspect if the battery goes open, there is a simple, inexpensive and
admittedly anachronistic prophylactic circuit: place a power-rated zener diode in parallel with the
battery having a breakdown voltage of say 50V. If you can't easily find zener diodes that can handle
the power, then use a "crowbar" circuit with an SCR and a zener diode to bias the gate. In the
event of an over-voltage because of an open battery, the crowbar shorts B+ to ground and blows the
battery fuse and charger fuse.

Hard to restore the origninal South Shore MGs when in East Troy case, im sure a couple of the MGs have disappeared over the last 3 decades.

I disagree about authenticity. you gotta do what you need to do to keep the cars running. If you run the car once a year, then i suppose being original is ok. but if you run it all the time, id go for the best maintence solution. and a solid state inverte/converter is probaly the best bet for East troy.

The riding public is not going to care if the car has an MG or a solid state converter. all they care about is does the car run, and can i ride it.

Tony, you've got that right! I personally believe
that the equipment should be preserved as best
as possible. That means adhering as much as possible
to the original parts and methods.

You are correct also, in that 99.99999% of the riding public
does not know nor care anything about the details of how it
runs, and why it runs, and what it represents historically.

Especially with the CSS&SB cars, there is always a balance
of these factors to be considered.

Given the fact that these cars are rather complex, keeping
(6) of them on the active roster is a significant challenge.

This situation also provides the opportunity to test
a few different concepts for charging the 32 volt
batteries.

A South Shore M-G set is a fairly beefish piece of metal, and oriented parallel to the carbody near the outside. It would do a fine job of concealing a digital converter installed behind it or above it.

bump

bump

Since it does not seem to be mentioned in this thread, you might approach a motor shop and ask what it would cost to rewind a motor for 600v operation rather than 1200? I think the result would be less windings on the same motor. I had heard of someone doing this on a much smaller motor in different voltages with good results. I have not heard of volunteers rewinding motors, but perhaps it is possible to do that and save on cost that way.

If you do ask about convershion there is a motor shop the Shore Line Trolley museume deals with a lot with good results. Unfortunately I can't remember the name of the shop right now.

An update on this:

Thanks to all of the very helpful suggestions posted here,
we have made contact with the design engineer at Absopulse Co.
and he has already quoted some prices.

With some more time and effort with this company, these solid state
units should serve our needs quite well on the CSS&SB cars.

Thanks again for all the great suggestions!

Updated Update from 11/14/19:

Insufficient funds are available at this time for purchasing
an Absolulse product. Experimentation is ongoing with the
home-made zener diode based charging regulator. This past
summer of 2019, the experimental unit was temporarily
installed on one of the CSS&SB cars for live testing.

So far, these tests have shown the prototype unit
proof of concept works rather well. Approximate
set points are: Start charging when battery terminal
voltage falls below 36 volts. Charge at 26 amps until
battery terminal voltage reaches 40 volts. This is
a simple regulator which just turns on, or turns off
the charging. The car being tested loads the system
to about 19 amps max load. With 26 amps charging
current that leaves about 7 amps charging when under
full load. This setup was tested extensively this
past summer. Track tested it 2 round trips so far.
Batteries remain cool to the touch throughout these tests.
The next testing phase shall be temperature oriented.
Must determine how the accuracy of it holds up
in low temperatures of late fall and winter, as compared
to summertime. So far it seems to be working ok.

One additional note of explanation: This is no longer
a 32 volt system. It is now nominally a 36 volt system
because the original Edison cells got swapped out
long ago with 2 strings of 3 each 12 volt lead-acid
batteries. These are rated at 150 amp-hour capacity.
The resulting string has 300 amp-hour capacity.

Chuck

bump. See updated update above.

Bump. It has been a few years since there has been any more info on this.
My highly experimental battery charging control system is still in place on CSS&SB car 33.

Basically what it does is it senses when battery voltage drops below a certain threshold.
Then it charges at a rate of around 26 amps until the battery voltage reaches the upper threshold then it shuts off charging and allows the system to run on battery only until again reaching the lower threshold. The two thresholds (high and low) are adjustable via (2) small potentiometers. The lower threshold is around 36 volts and the upper threshold is around 40 volts. During normal running the typical cycle time is around 2 to 3 minutes. The small control circuit runs on filtered, regulated 5 volts and is basically
two comparators that drive 2 small PCB style relays. Those relays in turn operate a
larger 32 volt relay that has heavy contacts capable of operating the charging contactor
under the car.

Since making, installing, and testing this unit, I have come up with an even better one.
The better one has been extensively bench tested but as yet has not been installed on
a South Shore car. This improved version uses an ICL 7107 digital voltmeter IC along with some additional parts to "read" this voltmeter. The high and low limits can be set in
on thumb-wheel switches and there is a nice big red 7-segment LED readout of the voltage. This allows more precise control and also allows "on the fly" adjustments
to be made to the (2) threshold voltages.

The museum crews have used the simpler version which has been in place since fall of 2019 with good service.

added a couple of photos

I was also thinking about this recently although I always wanted to go from 300 volts and eventually 600 volts to 12 volts. My thought was to basically base It off a 12VDC to 120VAC inverter like to type you would hook up in an automobile. Basically you just use beefier components on the input side to handle the higher voltage and amperage. Instead of having more turns on the secondary side to increase the voltage you would use less turns to bring the voltage down and then put it through a full wave bridge rectifier capacitor inductor system to give you a smooth DC output.