# A Question on NiMH for Our Battery Experts?



## RailCat (Apr 10, 2009)

Hello again,

I have finally finished designing an indoor railroad for my house 'though it will be some time before I can build it. The plan is halfway between a switching layout and a point-to-point shortline. Wiring and dirty track could be a potential annoyance so I would like to look at the option of battery power. Motive power will be a USAT GP7 using either AirWire or Pocket RailBoss Plus. The idea of a lithium fire indoors does not appeal to me so I would prefer to avoid lithium batteries until they are further refined. NiMH batteries seem to be the easily accessible alternative and I have not heard of them catching fire. I assume they could if severely overcharged but not like lithium.

The problem is that the loco will be run on an irregular schedule and I understand that NiMH packs self discharge quickly and will fail if not cycled regularly. This is probably what happened to an RC rock crawler that I had a year or two ago. The battery was always dead or nearly so when I wanted to run it. It stopped accepting any charge after I had it around six months or so. I never had that problem when I raced RC cars with NiCD batteries 25-30 years ago. I used the same two 7.2 volt Kyosho packs and a Novak peak charger until the local club died.

I wonder if this would be a solution to the problem; If I am reading the description correctly, the Tenergy TB6B charger (http://www.all-battery.com/tenergytb6b-charger-combo-90263.aspx is the one I am looking at) can be set to fully discharge a NiMH pack and then fully recharge it. My thought was that I could run this on the pack once a week to keep it charged and in shape. I am thinking every Thursday since I would probably operate the locomotive for five minutes to a half-hour on the occasional evening of a workday. Longer sessions would be more likely to occur on the weekends. I assume that it would also be a good idea to run the charger's discharge/recharge cycle after any run longer a half-hour. I only plan on converting one or two GP7s so the weekly cycle would not be inconvenient. Especially if each loco has its own charger. The idea is to have the loco available at the flip of a switch when the mood strikes. Do you think I am on the right track?

Thanks in advance!

-Scott


----------



## TonyWalsham (Jan 2, 2008)

I still prefer NiCd batteries for high draw locos. 
They last longer than NiMh batteries in terms of the number of cycles they can achieve. According to Sanyo 1,000 to 500. 
NiMh self discharge and each time that happens it is one cycle out of the total life. 
Still, if you will always be using the packs at least weekly, self discharge should not be too troublesome. 
You can actually leave NiCd cells on permanent trickle charge if you wish. Something that is a no no with NiMh.


----------



## eheading (Jan 5, 2008)

Your idea of charging the nimh batteries every week will definitely work. You probably wouldn't even have to charge them that often. The nimh batteries definitely self discharge faster than li-ion batteries do. I wouldn't worry about fire with the li-ion batteries if you get battery packs with the "safety circuit board" installed in them, and you use a charger designed for li-ion batteries. Most all cell phones and laptop computers now use li-ion batteries and we don't worry about them. The li-ion batteries are more expensive than the nimh batteries, but you'll get roughly twice the runtime from a li-ion battery the same size as the nimh battery.

Ed


----------



## Pete Thornton (Jan 2, 2008)

My thought was that I could run this on the pack once a week to keep it charged and in shape 
Scott, 
I have NiMH batteries in my steam engines for r/c and in my electrics for power. I try to recharge them every couple of months, but it is a chore. 

I left one pack on a charger and a timer in FL for this last summer - it was a smart charger and was supposed to keep the battery from discharging and failing. It didn't - I had to buy a new pack. 

My NiMH AA cells that I use in cameras and similar equipment exhibit the same erratic behaviour. Some die randomly, others soldier on, despite all being treated the same. 

Li-ion batteries hold their charge - I recently bought a power screwdriver and it seems to work whenever I want it to. As mentioned above, Li-ion batteries usually come with a 'smart' chip in them, so the chances of a fire are remote. I will be using them in the future.


----------



## TonyWalsham (Jan 2, 2008)

It was precisely because AA size NiMh cells in a digital camera, for example, were always flat when one wanted to use them, that Sanyo developed the Low Self Discharge (LSD) hybrid batteries now commonly available. 
These come fully charged and are guaranteed to hold 85% charge for at least a year. 
However, I counsel against using AA size cells for any loco that draws more than 1/2 amp or so. That is because if you draw from or charge them at a higher rate, you will shorten their life span in terms of the number of re-charges you can achieve. They are designed to last for a long time with a low current drain. Not a high drain for a short time. 

I use and recommend AA size LSD cells for low current draw locos such as stock Bachmann Annies, Thomas and Friends and the Li'l Big Hauler series.


----------



## RailCat (Apr 10, 2009)

Thank you for your replies, 

The railroad will be completely level with 48" radius curves. Experiments so far show that the geep can easily move a car with truck mounted couplers around a 36" radius curve but I only have one industrial spur where I might use a curve that tight. Space limitations in the house will limit the maximum load to a cut of six 50' cars pulled off the interchange. I will be using metal wheelsets on the cars which should help reduce rolling resistance. I don't don't feel that ball bearings would be a significant improvement however, due to the short train lengths. 

I have seen a picture of a USAT GP38-2 that had been modified into a GP39-2 with a removable long hood for battery access. There was also a Western Pacific geep on eBay last month that had a removable long hood. This would make battery access very convenient. The GP39-2 had the motor removed from the front truck to reduce power consumption. The caption with the picture did not say whether or not the traction tires had been eliminated from the rear truck. It did appear that half of a second weight had been added over the rear truck. The geep had been equipped with twelve Eveready AA NiMH batteries in holders which were supposedly good for three hour run times. With a six car max train length, I expect that I would only need one motor. I'm not sure about whether to leave the traction tires in place. The advantage of having them would be additional traction. The advantage to removing them would be the prevention of high-amperage stalls since the wheels could slip. I will probably have to experiment on that since I have extra non-traction wheelsets. 

I will be removing the smoke units and the factory lighting. I will use LEDs from Evan Designs to replace the headlights. The cab and classification lights should not be illuminated and I can do without illuminated number boards to save juice. I won't bother with sound if I use the Pocket RailBoss Plus control. I might add a Soundtraxx AT1000 that I have on hand if I wind up with AirWire. I want to try the Pocket RailBoss Plus first because I like the concept of the little three button remote. I wondered about using Sanyo Eneloop AA batteries but I assume even one geep motor would be too much load on them. 

Tony, Your comments on NiCd batteries have me thinking on them again. I had good luck with them many years ago with an RC Tamiya Blackfoot. If I remember correctly, I used to run them until the vehicle stopped, recharged them, and they would be ready to go for the next time. I thought NiCds were no longer available and I don't see them on your site. I do see a cable (Y-CABLE) to join two RC car packs and I found 7.2V 1800mAh NiCd packs on another site from Duratrax. I assume this should give me 14.4V which will be plenty for my purpose.  The price is only $11.99 each so I wonder if they are getting rid of them or do you suppose they are China cheapies that won't perform like the old packs did? I haven't disassembled the geep yet but I assume that if I remove the body support posts which would no longer be used, I will have room to stack the two packs where the prime mover would be on a real geep and put the motor control unit over the rear truck. 

-Scott


----------



## RailCat (Apr 10, 2009)

Oh, I just found Tony's how-to with two RC car packs in a USAT geep. (*sheepish grin*)


----------



## TonyWalsham (Jan 2, 2008)

You are quite correct about me not having SubC NiCd batteries on my site. 
I have been selling the SubC NiMh 7.2 volt packs here in Australia I bring in from China. They are supposed to be NiCd but come marked NiMh, so NiMh they are. I don't sell them overseas and I do warn my customers about them. So far they have been quite reliable. 
I can supply Sanyo 7.2 volt Sub C NiCd packs at about 2.5 times the price if anyone one in Australia wants them. 
I deal direct with the Sanyo importer in Australia who informs me that when it comes to batteries for ambulance and paramedic use here in Australia, they still opt for NiCd. 

Just this last week a customer sent me an NW2 that I had installed RCS R/C and Sanyo Cadnica NiCd batteries in about 17 years ago. The pack had finally died about 2 years ago after almost weekly use for all that time. The capacity was 1800 mah and the replacement pack will be 2500 mah.


----------



## Del Tapparo (Jan 4, 2008)

Scot - The Pocket RailBoss Plus supports 4 sound triggers. You can still get a lot of functionality out of a 3-button transmitter. 

I would also recommend Lithium-Ion batteries, although Ni-Mh or Ni-Cad will work fine, if you choose to use them.


----------



## Curmudgeon (Jan 11, 2008)

Yes, I wouldn't worry about fires with Lithiums. 
Reason is, I won't have them in the shop. 

Two 787's that we know of, a Honeywell ELT, 3 or 4 (depending on how much reporting has been quashed) Teslas, at least one garage with all the club locos, and one house, several engines I know of....... 

They're just wonderful. 

Charging NiCad or NiMH is not an issue here. Do it before each ops session...and over the next 4 weeks I can fire up any of them and run them out on the line without recharging. 

I put the charge jack in the end beam, easy to access, doubles as an auxiliary jack.... 

Even most NiCads I take out of service, they work fine as backup batteries when charged the day before.


----------



## RailCat (Apr 10, 2009)

I'm with Curmudgeon in regards to lithium rechargeables. I realize that technology improves all the time but changes are made as the technology is proven. I'm still pessimistic at this point. I don't have a laptop computer and my current phone has been doing great for over 15 years so far and doesn't use batteries at all. I realize the RailBoss I just ordered uses a lithium button cell in the transmitter but those have been around for a long time now and I feel quite safe with them. 

Got a pair of the 7.2V 1800mAh NiCd packs ordered. The site says in stock so hopefully they'll make it. I've dealt with this vendor before so my only worry is if it turns out that they only had one. Have now exhausted my discretionary income for now so other items such as the Y-Cables and chargers will have to be later. I'll use track power from an Aristo-Craft CRE-55465 DC supply to fill in for the batteries while I rebuild the trucks and experiment with them. Oh dear, I'm afraid the prospect of NiCd batteries has turned me to the dark side already (said in the voice of the emperor in Return of the Jedi). 

One thing I won't be able to test for a while is run time under operating conditions. I am guessing that most installations leave both motors in the locomotive. Leaving sound out of the equation for now and the only lights being the paired LED headlights and no smoke, Do you guys think I'll be able to get at least three hour run times using both motors given the light loads and zero grades I mentioned earlier? I'm not sure if a loco running intermittently in a switching scenario will use as much energy as one racing around a loop or not. Two hours will probably be plenty for me but it's nice to have a safety margin. 

What is the current practice on NiCds? If I grab some extra packs for spares down the road, Is it safe to leave them in their packages or would it be better to charge them before storing them? For that matter, Does anyone know where I could buy NiCd packs in the US that use Sanyo batteries? Either RC car packs or custom built? 

Thanks again, 
-Scott


----------



## SD90WLMT (Feb 16, 2010)

Ok Rail.Cat... 
Sorry but your over thinking here... 
Removing a motor does not lower power consumption. 
Cars create the load... 
If your pulling 6 cars..then 6 cars is the load.. a constant here.. 
Using a single motor, it now has do to the work to move those 6 cars. 
Using both motors only means they both share the work - pulling the constant load.. 
The 6 cars will make one or two motors work. One motor will work harder by itself to pull however 
What ever the actual amp draw may be for this will be the same regardless of the amount of motors. 

You have a level layout.. How many cars will it take to stall the loco if using traction tires? 
It does not sound like your layout is large enough to pull so many cars that this may happen. 
Why worry about it? 

I personaly have used traction tires..they have spun before under a technically stalled loco. Called a train wreck! The loco was drug backwards some distance while the tires dug in trying to move forward again.. nothing happened.. 
I'm not saying I reccomend this practice. But my loco weighs far more than most locos people play trains with, coming in at nearly 20 pounds. 

Good luck - do some re-thinking here and have fun! 

Dirk


----------



## RailCat (Apr 10, 2009)

Thanks Dirk, 

I am not an electrical expert by any means so this is very useful information and it does make sense to me. With both motors, I am sure it will have all the traction I need without the traction tires. I already have replacement wheelsets without traction tires so I will use them. Also thinking about getting some of the larger wheelsets and Delrin gears from NWSL. 

-Scott


----------



## TonyWalsham (Jan 2, 2008)

Check the axles in the motor blocks for cracking either side of the plastic worm gear. 
They do it all on their own. 
Really easy fix. No need to replace unless the gear it self is cracked. 
Pull the wheels out either side of the gear. They will come out easily if the plastic is cracked. 
Cut some rings, no longer than the plastic axle holders out of 3/8" ID K & S brass tubing. 
Chamfer the edges of the plastic and push the rings onto the plastic. 
Trim out the inside edge of the plastic and insert the old axles. Do both at the same time and use a drill press to carefully squeeze the wheels together so they go in evenly either side. Don't do it quickly as you will damage the tine plastic spacers halfway down the tube. 
Make sure the brass axle bearings are seated correctly in the trucks before replacing the bottom cover.


----------



## RailCat (Apr 10, 2009)

I think I have a local dealer for K & S brass shapes. it would be a simple matter to clip off a batch at work. The locomotive and replacement axles are new so they should all be good but I will check them when I change out the traction wheelsets for solid ones. As I understand it, the problem is much less common now. I bought four 44-Ton switchers off eBay and rebuilt one of them to run. All of them are in like new condition but all of them had split axles when I got them. I have a stockpile of replacement wheelsets for them as well without a split in the bunch. 

I bought the 44-Tonners before I realized that I could build a railroad suitable for a GP7 and had planned to power it with an NCE DCC system that I had been using for HO scale. Now it looks like I will have look into converting the 44-Ton over to battery as well or leave it parked. I think I remember reading how someone had used a group of AAs in battery holders behind the skirts in place of the battery box and air tanks. Do you think Eneloops would work for this application? 

-Scott


----------



## TonyWalsham (Jan 2, 2008)

I used AA's in my 7/8n2" loco I converted from a USAT 44 tonner. 
They lasted just fine for the roughly 10 years I owned the loco. The new owner has had it for a couple of years and they are still running strongly. Secret is don't try and pull too much with them and don't fast charge them. Absolute max is 1 amp charge. 
Save the AA's for light load locos and they will last for years.


----------

