a fairly special controller for a caboose

Wolf Harper · October 2012

I have been asked to install a small solar panel on a caboose. It already has a 12v electrical system, which runs four "40w" cabin lights (switched to 6w LED) and a "15w" tail blinker (switched to a 1w narrow focus LED.) This is a working caboose at a railroad museum. The caboose's original 1970 battery still works, it is an Edison battery with 10 cells. It has enough juice to get through an operating day. We generally run once a week so there is plenty of time to recharge it. But I am sick of running extension cords.

Due to the numerous overhanging branches along our railroad, there are only 2 possible protected locations to mount the panel, these are 18x24 and horizontal. That means I won't get as much performance out of the panel as I would like. I am probably going to need an MPPT charge controller. But I need it to do two special tricks that I don't see in every MPPT controller.

Trick #1. Going down the railroad, it will rapidly change between sun and shadow. it enters shadow fairly suddenly. The MPPT needs to respond quickly, and not waste a lot of time re-adjusting.

Trick #2. It needs to know how to charge Edison type nickel batteries. (NiFe or NiCd). They require different charge curves than a lead acid. I don't want to change to lead acid.

Any suggestions on a good choice for charge controller?

Shadowcatcher · October 2012

Re: a fairly special controller for a caboose

Some one may contradict me but it would seem to me that a Morningstar Sunsaver MPPT and consider the use of flexible panels such as a Unisolar. These could become the roof and they would be more resistant to damage by branches and would be less obtrusive in the install and appearance.
The Sunsaver is programmable using a computer interface, and Morningstar might be able to set it up for you.

niel · October 2012

Re: a fairly special controller for a caboose

the unisolar would not fair well as they are large and output half as much power as standard crystalline types.

couldn't you hang a pv out the back end? it may need to be able to swing down though for times when the back end gets coupled to another car or engine.

CATraveler · October 2012

Re: a fairly special controller for a caboose

You should be able to install 2 20W panels in series which would recharge the battery. While traveling the battery supplies the lights so I don't see the need for trick #1. It will also recharge on either end and if not 100% SOC at the end of the day it will be in a day or so.

Is this a 10 cell 20V battery? I'd contact controller mfgs to see if they can help. Since they typically support 12V and 24V see if you can get their attention for a special need. Use the non profit card and they might be interested for a variety of reasons including tax deductions and advertising.

CATraveler · October 2012

Re: a fairly special controller for a caboose

BTW Which museum?

Wolf Harper · October 2012

Re: a fairly special controller for a caboose

The Southern Michigan Railroad Society, Clinton-Tecumseh MI. Here is the caboose
http://www.railroadmichigan.com/smichcabe01.jpg
Look above the tail light, you can see a heavy steel channel on the roof, and there's another about 20" over from it. These held the roof walks. There's another just like it on the opposite corner (also visible). My notion is to bolt a piece of plexiglass to them and the solar panels underneath. Have to replace it often, but beats a broken panel.

I'm willing to take my chances with charging while enroute. The only thing that worries me is that some of its parking locations can have intermittent solar coverage, as the shadow of trees, buildings, telephone poles etc. tracks across the roof. There could be fair amounts of time with one panel in the shade. What happens then? Do I need both panels in clear sun to charge or can it work 50% well with one panel good?

CATraveler · October 2012

Re: a fairly special controller for a caboose

I understand your concern about trees. But how often does the smoke stack get moved? Would a simple wooden frame around the panels provide protection? How often and to what extent does the observation roof get whacked?

It would appear to me that you could mount even larger panels but I can't walk in your shoes.

With parallel panels one in full shade with have no output and one if full sun will have full output. Serial panels and ones with bypass diodes might even be better for you.

My opinion having seen the picture: Panels and mounting can be solved - The potentially bigger issue is a controller that will properly charge your battery - No one wants to be responsible for the demise of a 1970 era Edison battery!

You may shoot me for this suggestion: What if you added a deep cycle 12V battery for the lights (with solar) and charged the Edison every few months? OK I'm getting into my bullet proof suit!

Wolf Harper · October 2012

Re: a fairly special controller for a caboose

The fancy stack you see in the photo has since been torn off by tree strikes. The railroad is only 12 miles long but there are woodsy areas most of its length, and the brush crews don't have the equipment to work that high safely. So, a LOT of tree hits. I put a new plexiglass side window on that caboose and after 2 days the plex was covered in scratches.

A wooden frame could protect the edges from the worst of the hits, but that branch will get dragged across or bounce on the panel proper, then what? I don't actually know how tough panels are.

Edisons charge at a slightly higher voltage range. A lead charge controller won't destroy the battery, just won't charge it fully. There are very few things that will damage an edison battery... undercharging, overcharging, leaving them discharged, boiling water away, repeatedly flattening them... are not five of them

That makes them fairly volunteer-proof, and that's a thing I like a lot.

Wolf Harper · October 2012

Re: a fairly special controller for a caboose

niel wrote: »

the unisolar would not fair well as they are large and output half as much power as standard crystalline types.

But flexible panels have their use, most of the roofs at the museum are curved. Roof space is not a scarce commodity, tree hits notwithstanding.

couldn't you hang a pv out the back end? it may need to be able to swing down though for times when the back end gets coupled to another car or engine.

Possibly. I'll look to see if it could hinge down and "stow" below the vestibule ceiling. Of course, could not use it during operations. Another possibility is the end of the car, as it always faces south. However a lot of shadows of beams and grab irons will be raked across the panel. I'm not sure how a panel performs if a shadow of a pipe is laying across it.

BB. · October 2012

Re: a fairly special controller for a caboose

Shadows on solar panels pretty much kill the output of that panel. They really only work well when not shaded or partially shaded.

Regarding tree strikes and such--Solar panels are 1/8" thick tempered glass (single weight window glass). They are not going to take hits very well. And if they get hit hard enough, the glass will shatter and the panel will fail.

-Bill

CATraveler · October 2012

Re: a fairly special controller for a caboose

It sounds like you could make a larger frame for the panel and cover it with plexiglas. Also some time back I saw a panel that was destruction proof - perhaps these would be strong enough for your application.

Have you considered a plywood cover that would be closed on the travel day and open the rest of the week?

BB. · October 2012

Re: a fairly special controller for a caboose

I would guess that covering with Plexiglas will also cut down on the amount of sun hitting the panel (especially over time as the plexi scratches/ages).

-Bill

niel · October 2012

Re: a fairly special controller for a caboose

if you can find the unisolar us64 pvs you could use those as they are fairly durable and i know because somebody has still been trying to break them at my place by throwing rocks at them, but they are thin film and take up a large area for the power produced. they had smaller versions too, but weren't as popular as the us64 and of course they are no longer manufactured. shading is still going to be a problem for you and yours is a difficult situation no matter how you were to look at it. the mppt controllers may not be good to use when being flashed the light through random shadings.

CATraveler · October 2012

Re: a fairly special controller for a caboose

How about using tempered glass as a cover? Also I'd think that any covering has the potential for excessive heat for the panel.

CATraveler · October 2012

Re: a fairly special controller for a caboose

Different approach: Mount the panels on a post near the parking area and plug in when done for the day.

CDN_VT · October 2012

Re: a fairly special controller for a caboose

OR another is to have solar as a secondary , top up and use the wheels with an alternator drive. Just use a no field / battery Volt reg as we use on PTO tractors.
When the train moor's , it should be-able to pick up enough topping up / eq/float after a good bulk from the axle's.
Caboose is the last in line , put up a sacrificial spar a bunch of cars ahead. I would say a Sail boat is the hardest on PV panels .

VT

niel · October 2012

Re: a fairly special controller for a caboose

worst case, get an inverter/generator to charge up some batteries through a 3 stage charger when needed. not sure if they have propane conversions for them or not as having a tank of propane would be better than gasoline sloshing around while the train is moving. you can still fiddle with pv too if you like as it might reduce the needed time on the genny some.

Shadowcatcher · October 2012

Re: a fairly special controller for a caboose

I have one of the Unisolar panels as a 'stake it out in the sun for additional when needed' with our teardrop trailer. It is 18' long but is 144W. Having stepped on it a number of times I have to say it is durable. It is also high voltage and seems shade tolerant.
I am also mindful of keeping in character with something in a railroad museum that is minimally anachronistic. A plexiglass panel that is changeable once it gets terminally scratched. I will still say the computer interface and program-ability of the Morningstar would seem to make it a good candidate for controller.

RandomJoe · October 2012

Re: a fairly special controller for a caboose

My first thought, since you said you have a few days between runs, is to make a (couple) portable A-frame stand for the solar panel(s). Stow them inside the caboose when doing a show, then after it's parked just pull them out behind / to one side so they're in the sun and plug them in. They'll get sun during the off days and charge the battery.

This does depend on your yard being secure, so the panels don't walk off...

You still have to "plug in" the caboose, but you don't have to drag cords all over the place, just a few feet to one side in a sunny spot. It also means you don't have non-original (and I'm sure some would say "ugly") panels mounted to your museum piece. Also no risk of damage during runs.

westbranch · October 2012

Re: a fairly special controller for a caboose

Another thought: what is the space on the side of the "top hat" on the caboose? It looks like it is blacked out? Is it boarded up?

Is the caboose oriented oriented in the same direction at each end of the line?

If it can get sunlight maybe a PV that will fit that space could be used...? or one on each side?

Shadowcatcher · October 2012

Re: a fairly special controller for a caboose

You have the platform for trimming branches, the caboose. A temporary platform constructed on the top of the caboose with proper safety restraints/harness and a chain saw would do wonders.

Wolf Harper · November 2012

Re: a fairly special controller for a caboose

Sadly our yard is not secured yet... we have bought 90 acres for a large museum site like Illinois Railway Museum or Orange Empire Railway Museum. But that will be years in the making. As far as getting crews to beat back the brush, we already put tons of volunteer hours into that job, but it is a miserable thankless job and volunteers tend to call it "done" when it doesn't hit the passengers. It is just not practical to rally volunteers to the extra effort needed to prevent roof hits.

westbranch wrote: »

Another thought: what is the space on the side of the "top hat" on the caboose? It looks like it is blacked out? Is it boarded up?

Is the caboose oriented oriented in the same direction at each end of the line?

Yes, the caboose end (the one shown) is oriented within 20 degrees of south at all times except traversing one curve. It is a north south railroad.

That is the cupola, where crews would sit to sight down the side of freight trains looking for smoke coming out of the old babbit bearings (used until the 1980s). The outer areas on each side are windows. On the ends, the inner areas are unused.

That center of cupola area would be a great place for a panel if it didn't disrupt historical appearance too much. The Penn Central RR was all about solar panels, just not on cabooses. RR's have tons of remote signal cabinets which consume six watts, but are miles from commercial grid power. Needless to say, when solar panels first came out, they were racing NASA to the front of the line.

niel · November 2012

Re: a fairly special controller for a caboose

some of those remote signal cabinets may contain some of my handiwork if they are from the union switch and signal. i put in 6.5 years there before they decided to shut things down and move to break the union. they are now back in the area, but i believe it's only the el engineers and other paper pushers.

Wolf Harper · December 2012

Re: a fairly special controller for a caboose

I'm happy to report the caboose installation was a success. Pic and description here.
http://www.rypn.org/forums/viewtopic.php?f=1&t=34261&p=187013#p187013

I wound up going with the cheapest Morningstar controller because I was worried that an MPPT controller's algorithm might be confused by the constant and sudden changes of sunlight as we roll through the woods. The simple PWM controller will deal with that on the fly. I have not installed gages, but the controller caps takes input voltage around 17V and the battery side is exactly 13.8V, which suggests to me it's working fine. Won't fully charge an Edison, but charges it enough for our uses. We tested this on a night run using a locomotive-bright LED headlight the whole way, this after a month of using it normally and not ever plugging it in. It is in November/December in Michigan so we are dealing with worst case.

BB. · December 2012

Re: a fairly special controller for a caboose

The wires you are using are probably not UV resistant--If you can put something over the wires to protect them--The insulation will probably last a lot longer.

-Bill

inetdog · December 2012

Re: a fairly special controller for a caboose

Wolf Harper wrote: »

I'm happy to report the caboose installation was a success. Pic and description here.
http://www.rypn.org/forums/viewtopic.php?f=1&t=34261&p=187013#p187013

I wound up going with the cheapest Morningstar controller because I was worried that an MPPT controller's algorithm might be confused by the constant and sudden changes of sunlight as we roll through the woods. The simple PWM controller will deal with that on the fly.

That sounds like the right choice for you, as long as you are satisfied with less than full charge on the Edison battery.
But I would like to see you correct part of the posted description:

It also uses PWM to turn overvoltage into more useful current.

That is what an MPPT controller does. PWM lets you use higher input voltage without overcharging the battery, but current-in is identical to current-out. No use is made of any extra voltage. That is why with PWM controllers a "battery" panel with the minimum required output voltage (Vmp) is used.

niel · December 2012

Re: a fairly special controller for a caboose

thanks for the update.

that pv may be too small to even overcome the shelf losses so it may have a slow progression of being drained without being brought back up even after a week. at some point every so often i would still throw a proper charge at it, be it from a generator and charger or pulling the battery to take somewhere to charge it up. i'm not sure what the specific gravity should be in that battery, but that is one way to check on the battery's condition. another rough way may be with its 'at rest voltage' after no loads or charges are put to the battery for maybe 3-4hrs or longer if you can. i can generalize in saying if you start seeing at rest voltages below 12.4v that you will want to hit it with a charge from another source soon. letting too much of your battery capacity to deplete will mean there is more water in the battery and less acid and the freezing point of the battery progressively goes up as capacity goes down.

also, allowing a battery to stay lower than 100% soc (full charge) for long periods of time could allow sulfation to set in and start to kill the battery.

inetdog · December 2012

Re: a fairly special controller for a caboose

niel wrote: »

i'm not sure what the specific gravity should be in that battery, but that is one way to check on the battery's condition. another rough way may be with its 'at rest voltage' after no loads or charges are put to the battery for maybe 3-4hrs or longer if you can. i can generalize in saying if you start seeing at rest voltages below 12.4v that you will want to hit it with a charge from another source soon. letting too much of your battery capacity to deplete will mean there is more water in the battery and less acid and the freezing point of the battery progressively goes up as capacity goes down.

also, allowing a battery to stay lower than 100% soc (full charge) for long periods of time could allow sulfation to set in and start to kill the battery.

Good advice for Lead/Acid, but I believe that the OP said that this was the original Edison NiFe battery bank. In that case SG does not change at all with state of charge, and it is less critical that the cells be brought up to full charge soon after discharge.
AFAIK, the only ways to tell what your SOC is on an Edison cell is to measure the voltage, do a full discharge load test, or use a battery monitor. Even the latter will not work well because of the relatively low charging efficiency of NiFe, which I believe also varies with SOC.

niel · December 2012

Re: a fairly special controller for a caboose

good catch and my oversight. been talking lead acid too much.

a fairly special controller for a caboose

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