# battery question



## mymodeltrain (May 14, 2013)

I am searching for battery for my design, I saw this type of battery online, 7.2 Volt 1500 mAh NiCD Battery. I wonder how long would it last, for my Piko locomotive 0-6-0 with a head lamp ? Usually, Piko locomotives run well at 7-9 volts.


----------



## BigRedOne (Dec 13, 2012)

Do you know the current draw of your locomotive?

That battery is rated at 1.5 amp-hours, which means if the draw is one amp, it will last about 1.5 hours (or less, once performance degrades.)

My LGB Stainz draws a bit less than one amp.

I do think that battery is both lower voltage, and less capacity, than is customary for battery power in G scale.


----------



## mymodeltrain (May 14, 2013)

Do you know the current draw of your locomotive?


I will measure tonight and let you know. Is there any compact rechargeable battery allows me to run 4 hours.


----------



## BigRedOne (Dec 13, 2012)

I think you'd want something in the 4 to 5 amp-hour range, assuming your locomotive's current draw is similar to my Stainz.

Also, I don't think it is safe to assume a battery rated at a specific voltage will provide the same speed as a measured voltage off the power supply. Do you have a way to test the battery? 7.2 volt, 1,500 mAh is common in the R/C car world.

To get more capacity, you'd either get a battery with larger cells, or just use more than one pack wired in parallel. The exact configuration depends on the space available in your locomotive, weight distribution, how removable it will be, etc.


----------



## chuck n (Jan 2, 2008)

As a rule of thumb, I figure on one amp per motor. All of my engines draw one amp or less per motor on the level. Tight curves and heavy long trains, or grades will increase the power needed.

Sound and smoke will add to the power draw.

I'd recommend a minimum of 14 v. Most of my batteries are 18v. 

Chuck


----------



## East Broad Top (Dec 29, 2007)

How much voltage does the control electronics for your loco need? That's going to be the primary determining factor as to how much voltage you "need" to run. If your electronics need 12 volts, then you'll want a 14.4 volt battery at a minimum so you can make sure your control electronics have the power they need to function properly. 

Know also that while NiCad battery technology is certainly proven, it is also largely outdated. Most folks who run battery power today have gravitated towards Lithium-Ion battery technology. The batteries are much smaller, lighter, and pack more voltage and more capacity into that smaller and lighter form. I switched over to them in 2009, and they're by far the best battery technology I've used for model trains in the 30 years I've been using battery power.

*Here's a link* to one that has proven quite popular with battery power folks. I'll get between 2 - 4 hours run time off of one of these packs on most of my locomotives, depending on how I'm running (lots of switching vs. constant round-and-round). In most installations, my battery packs are easily accessed so I can simply remove them and replace them with freshly-charged batteries, so I can run pretty much continuously if schedule permits. (And you can't beat that price!--typically they'll go for twice that. I've stocked up on them this Summer.)

I've got one of these packs installed in my son's Piko 0-6-0, and it runs a good long while on a charge--probably better than 4 hours, though I've not timed it specifically. I know he's run the pants off of that loco this summer, and I've only had to charge it a handful of times so far. That's with lights sound (Crest "Revolution") and motor. I did--on this one--install the battery permanently, so I've got to pull the loco off the tracks to charge the battery.

Later,

K


----------



## mymodeltrain (May 14, 2013)

Thanks all the information, it's really a new set of knowledge for me. I will look into Li-ion battery.


----------



## mymodeltrain (May 14, 2013)

EBT

I call the shop, they have the Li-ion battery but they don't have the charger. May you tell me where to buy the charger the allows me to connect/disconnect to that type of battery.


----------



## chuck n (Jan 2, 2008)

I'm now using Li-ion batteries. They are smaller and can be easily removed for charging so you can quickly put in a freshly recharged one if necessary. My Accucraft K-28 has Ni-mh batteries about the size of Ni-Cd. They fill the tender. I'd guess that they are about four times the size of my Li-ion packs. The lithium batteries are more expensive.

Chuck


----------



## mymodeltrain (May 14, 2013)

Chuck,
Are the chargers the same for Li- and Ni-Cd batteries?


----------



## chuck n (Jan 2, 2008)

Not necessarily. It all depends on the charger. I have some that are designed for different chemistries and some that don't. If you go with Li-ion get a charger that can handle the the common battery voltages you might need. 14, 18, and maybe 22volts. Unless you know for sure your charger can handle Li-ion batteries, don't use it.

Chuck


----------



## Treeman (Jan 6, 2008)

mymodeltrain said:


> Chuck,
> Are the chargers the same for Li- and Ni-Cd batteries?


You need to match the chemistry and voltage.


----------



## chuck n (Jan 2, 2008)

Mike and I are in total agreement. The charger MUST be able to match the battery chemistry and voltage. My charger for Li-ion batteries can be set for several common voltages.

Chuck


----------



## East Broad Top (Dec 29, 2007)

*Here's a link* to the charger I use for my batteries. There are other chargers out there which allow you to select the battery chemistry, voltage, etc., but I've found these rather inexpensive chargers to do a great job with my packs. I've also got one like Chuck's that is dedicated to Li-Ion packs, but allows me to select the voltage. (Again, pretty inexpensive - around $20). I typically use 7.4 volt batteries to power the lights in my cabooses and passenger cars. With LED lights, I've gone two years on a single charge!

Later,

K


----------



## IPTRAIN (Jun 1, 2012)

mymodeltrain said:


> EBT
> 
> I call the shop, they have the Li-ion battery but they don't have the charger. May you tell me where to buy the charger the allows me to connect/disconnect to that type of battery.


Hi mymodeltrain,

Charging LiIon batteries is not that easy as it sounds:

They need special load treatment when connected serially. One single cell (4.2 absolute peak voltage) is not an affair, but two cells in series can result in loading one cell with 4.0 volts and the other with 4.4.!

Critical: Cells loaded with > 4.2 volts can explode (many examples at youtube.com)! 

You will need cell load balancers when loading more than one cell in series - which will make your hobby a bit more expensive.

Nevertheless I am using LiIon because of efficiency reasons (best ratio of capacity to volume).

Trustfire (directly imported from China) is a good recommendation as they have built in overload protection. They are well recognized and recommended in the community.

But Overload Protection is not Load Balancing - does not guarentee a fully loaded battery - it is just a fail save option not to explode.

The trick I am doing - not to load beyond 8 volts two cells in series! Means, the cells are never fully loaded (100%). But this doesn't bother me as I have power on the tracks in addition. 

I am reloading permanently - but mainly at trainstations where tracks are polished and the electric connection between wheel and track is guarenteed.

If you will need more voltage, this type DC-DC Step Up Board ("DC-Transformer") from China is a valuable help. 
Price to Germany (Shipment included) is 10 US$ - but takes two weeks to ship. 
This example can transform 8 volts to 20 volts with high efficiency (90%). Current supported is 6 Amps. Others even can do more.

Regards


Karl


----------



## mymodeltrain (May 14, 2013)

Thanks all for the information. This is my project during the holidays. There will be a train show in Nashville on Dec. 13, I am looking forward to getting some other stuffs for the railway; this is for the SouthEast train show only, it is not very big but fun enough for the locals.


----------



## mymodeltrain (May 14, 2013)

The trick I am doing - not to load beyond 8 volts two cells in series! Means, the cells are never fully loaded (100%). But this doesn't bother me as I have power on the tracks in addition. 

Can we run a battery-powered locomotive on powered tracks? I guess we have to align the locomotive for appropriate polarity?


----------



## Greg Elmassian (Jan 3, 2008)

It can be done, use a full wave bridge rectifier to get the proper polarity, but you really need some circuitry so as not to overcharge the battery... this has been tried a number of times.

My best advice is don't bother and concentrate on a really good battery solution to get the run time you want. With modern batteries you can do wonders.

Greg


----------



## mymodeltrain (May 14, 2013)

Greg,
I agree, we already planned to convert for a battery-powered locomotive why bother track-powered anymore.


----------



## Greg Elmassian (Jan 3, 2008)

The tricky thing to do is to put an intelligent charger on board the loco, and have it "remember" what it was doing during brief power interruptions.

Smart chargers are run by microprocessors, and cutting power makes them "start all over" in their analysis of the battery. Also having a load on the battery during this analysis makes it difficult... there's more related reasons, but it would be tough to solve.

Bottom line, the extra engineering, cost, and physical size of the unit could just be utilized by a few more battery cells and longer run time.

Greg


----------



## Bill Swindell (Jan 2, 2008)

The Li-Ion packs that seem to be fairly commonly used had internal circuit boards that control cell balancing, maximum discharg and charge rates. That might help somewhat. Possibly a better way to do hook the track power in parallel with the onboard batteries through diodes from each, This way, the track power will provide power to the engine but will not get into the battery. That way, if the track voltage is higher than the battery voltage, the engine will run from the track voltage. If the track voltage goes away, the engine will run on the batteries. Doing this will give you the extended run time without taking any chances with destroying the batteries.


----------



## TonyWalsham (Jan 2, 2008)

Bill is correct.
However, it does require clean track to work properly.
I used to do it 25 years ago. It has been my experience that ultimately the track becomes so grotty the loco ends up running solely on the batteries anyway.


----------



## Michael Glavin (Jan 2, 2009)

Bill, 

OEM and battery pack assemblers/reseller offerings have yet to be equipped with cell balance features in my experience. Pretty much across the board the PCB-PCM's included with assembled battery packs; monitor voltage and current draw offering short circuit disconnect features/protection collectively as a battery. Individual cell performance is unadulterated by these basic PCB-PCM's...


----------



## Greg Elmassian (Jan 3, 2008)

That's a pretty cool, and simple/elegant idea Bill.

Yes, clean track will help, but the diodes will "switch" immediately.

The issue you will have is when the unit switches from track to battery, it is likely to make a real difference in speed.

Greg


----------



## placitassteam (Jan 2, 2008)

I am curious why 2 batteries in series would not charge to the same voltage. Is it due to differences in the internal resistance of the individual cells? When I bought my RV it came with two 12 volt batteries in parallel and one would always charge better than the other and the bad one would then discharge the good one. I replaced them with two 6 volt batteries in series and never had any more problems. However these are lead-acid batteries so maybe they act differently.


----------



## Greg Elmassian (Jan 3, 2008)

No, your experience is not strange.

Slight differences in batteries will make a difference in the splitting of the charging current in parallel.

In series, you do indeed force the charging current to be identical, but that does not guarantee that the batteries are charging fully either.

Neither way is optimal.

Greg


----------



## Michael Glavin (Jan 2, 2009)

Winn,

Yes, internal resistance is a key factor of the conundrum you describe. The path of least resistance will generally soak up more potential than the latter. SOC or state of charge plays a role too. 

Are you having an issue with your lead acid batteries utilized in multiples?

Michael


----------



## Bill Swindell (Jan 2, 2008)

Michael,

The Tenergy PC boards are connected to each cell in the pack. I believe they are monitoring the charge state in each cell.


----------



## placitassteam (Jan 2, 2008)

> Are you having an issue with your lead acid batteries utilized in multiples?


 Michael, Not since I went to two 6 volt batteries in series.


----------



## Michael Glavin (Jan 2, 2009)

Bill,

I'm familiar with Tenergies and others PCM/PCB's. Things may have changed, my recollection is that there are a few switches wired in series in play; high/low voltage cut-outs and current/short circuit protection/disconnect. When I tested batteries destined for giant scale R/C onboard aircraft power supplies back in 2006 the cumulative voltage/current was the interceding factor, not cell by cell reporting even though each cell is able to report its voltage condition. Seemed silly then and now. That said there are PCM/PCB's that do more, they cost about four or five bucks more than the atypical protection circuits. 

Michael


----------

