Large Scale Central

Batteries for the bigger Accucraft locos

Electronics Power and Sound
#1

Hello all,

A good friend of mine had originally set up my Accucraft C-21 with the airwire board (first generation) and a series of two battery packs. Each pack is 4-18650 3.4v batteries. It worked great for a couple of years and I never had an issue with it. After pulling it out of storage the airwire board pretty much ended up catching fire and when attempting to set up an extra board I had to match the first, i had the same resultant. So that was the end of that.

What I’ve got now is a second generation board with just a single battery pack. My problem is that although I still get the necessary voltage, the engine runs at extremely low speeds even with all of the cv voltage settings maxed out.

Would it be best to get a “bigger” pack, not knowing if i need more amps or what-not? Or would be best to figure out a series of packs again?

Please help- these electronics are not exactly my forte… I’m used to burning my fingers with live steam! Lol

Thanks in advance

Matt

#2

What’s the voltage going to the motor? If the loco ran adequately fast with the original Airwire board and a 14.8v Li-Ion pack, it should (in theory) run the same with the G2 board and the same battery voltage.

Do you know what caused the failure of the original boards? Could something have shorted out in the motor, perhaps causing it to not run the same as before?

Try running the motor directly from the battery pack and see how it runs. If it’s lethargic with the motor connected directly to the battery, try a different power source of roughly the same voltage. If it springs to life, it’s the battery pack. If it’s still lethargic, it may be the motor.

Later,

K

#3

I have an Accucraft C-21 and even at full voltage (~21v.) from my Bridgewerks supply it still runs at a snails pace.

Doc Watson

#4

Matt

Sounds like something shorted out, did the fuses blow on the A/W boards? How were the batteries wired, did you have to uncouple them or something to charge and reconnect, the fire part of your comments concern me? Was a proper Lithium charger utilized configured for the specific batteries under charge? Sounds like something is amiss and should be sorted out or at least understood to prevent same IMO.

Please clarify what size battery you have in play, how many volts and what mAh capacity.

Michael

#5

In addition, please put it on rollers, run it up to full speed, and measure the voltage at the motor terminals.

Greg

#6

The batteries could have been shorted (copper shunted from extended low voltage) but if a fuse were in play it should have protected the board(s).

Michael

#7

I believe that you may have exceeded the maximum input voltage for the AirWire receivers. If you have a G-2 decoder, I believe the maximum battery pack would be 6 cells in series. That would be 22.2V nominal but right up to the maximum when the battery is freshly charged. Prior versions of the AirWire handled this input voltage but the split supply option must be used with this high input voltage. I did one with the high voltage but put in a voltage regulator to limit the input for the part of the receiver that does not run the motors.

This is probably confusing but you need to look at the maximum voltage rating on any elextronics that you use. BTW, a 14.8V is actually 16.8V when freshly charged.

#8

Matt what you did if you only are using 1 batt. pack now is cut the voltage in half and the max.speed is going to be half of what it was.

both of the decoders will take a max. of 28 volts. What i read you were running the org. around 26 or more volts. To me it sounds like you need to up the voltage.

#9

Ah, I think Richard has hit it. I read “series of” batteries in your post, but didn’t register that it was two 14.8 volt packs wired in series. At full charge, that will be north of 30 volts (maybe as much as 32), which is more than the Airwire can handle. With only 14.8 volts, it’s going to run slower. An 18 or 21 volt pack should give you the speed you need without overloading the Airwire.

Later,

K

#10

The caveat with elevated voltage being suspect is;

“It worked great for a couple of years and I never had an issue with it.”

“After pulling it out of storage the airwire board pretty much ended up catching fire”

“when attempting to set up an extra board I had to match the first, i had the same resultant. So that was the end of that.”

18650’s Li-Ion cells are rated at 3.6V per cell nominal, immediately hot off charge they’d read 4.2V per cell. Two four cell batteries in series would provide 28.8V off charge but voltage would fall off slightly thereafter. It’s plausible high voltage is the culprit, but I’d like to here more about the sequence of events and if a new battery was added to the mix or not.

Matt, we need more information, were the batteries wired in series or parallel, were the batteries charged prior to letting smoke, were the original batteries in play, and what kind of charger was utilized?

Michael

#11

Michael the way I read it he says the two packs are in series. But he did not ask what caused the two boards to go up, for all we know he could have pulled the batteries to charge and then hooked them up backwards that would cause a fire like he said. What he is asking is how to make his loc. go faster and that is why i said increase voltage because he is only using half the voltage now.

Cheers

#12

Richard,

I concur with your thoughts on the possibility of connecting the batteries up incorrectly (see my previous comments). That said, IMO Matt doesn’t state the batteries were wired in series, but that maybe exactly what he was suggesting.

“the airwire board (first generation) and a series of two battery packs. Each pack is 4-18650 3.4v batteries.”

FWIW: I’d suggest an Accucraft C21 with two 18650 2200mAh or so batteries wired in series would provide great voltage 28.8v, yet it would be rather anemic from a run time and or duration perspective I believe. And it makes sense as you suggest; the engine would run slower IF two batteries were previously wired in series with 14.4V batteries @ 28.8V verse operating with a single 14.4V battery at halve the voltage.

14.4V 4S2P (5200-5600mAh) Li-Ions batteries are VERY common in todays battery powered G scale train-world. Albeit IMO a better less expensive solution garnering like performance is two separate 4S1P batteries (2200-2600mAh). 14.4V 5200-5600mAh batteries are nothing more than two four cell series wired batteries, wired in parallel wrapped in one package, generally offered to the public at a premium price for the convenience thereof.

In addition to saving some bucks with 4S1P batteries, the flexibility to wire them in series if need be is nice and there is this; inevitably a single cell failure will take your prized 5200mAh 4S2P battery and delegate it to the recycle bin sooner than later… Why go there, I’d rather pitch and replace the one dead inexpensive battery than the expensive 5200-5600mAh battery.

Michael

#13

Gentlemen,

Sorry for the absence- I was just off on vacation for a spell. After reading through, it looks like I need to clarify a few things.

The batteries were in parallel- spliced to a single connection.

I did connect the motor directly to batteries and it produced the same speed as running the power through the airwire.

Here are the batteries most recently recommended to me- http://www.batteryjunction.com/tenergy-11v-4400.html

Thoughts? They look good to me, just a little pricey.

Do the Mah’s signify a longer run time overall with a battery?

Thanks

Matt

#14

Matt,

That battery will suffice for the C16 Accucraft engine. As I recall this engine is equipped with a 12V Pittman motor, is that correct?

Yes, higher mAh numbers suggest longer run times as compared to lower numbers. The 4400 mAh battery you noted, is basically two 3 cell 2200 mAh batteries wired in parallel.

Do you have a battery charger designed for Lithium-Ion batteries and if so will it support 3S2P 10.8V batteries?

Michael

#15

Hey Michael I would imagine so but with all things considered i don’t have the owners manual and on the Accucraft website they only offer the manual for the live steam version- go figure… ha ha.

This is the charger that I currently use for the Li batteries- Going by the voltages printed on the charger, it looks like it would support those batteries?

Matt

#16

Matt,

Ok you’ve got a basic charger rated for Li-Ions… I’m not familiar with this specific charger I believe its rated at 500 mAh? This charger and or similar ilk require the battery to have a protection circuit, verify that your battery is equipped with same. It would be prudent to calculate an anticipated charge interval for your battery. As a rule a MAX of three hours is atypical for this cell technology. Problem is this charger is not capable of adjusting the charging current to match the battery mAh capacity. More likely than not this charger was intended to be used with 2200-2600mAh batteries.

I’d suggest a more sophisticated truly SMART charger. Something like Tenergies TB6AC or one of the many others utilizing the same IC, typical cost is around $60.00 USD

Michael

#17

Matt, that’s nearly identical to one of the chargers I have. You should have no trouble charging a 4400 mAh pack with that. Expect it to take 6 - 8 hours if the battery is flat. I like it because it charges various voltages. I typically use 7.4 volt packs for the lights in my cabooses and passenger cars, and while most of my locos run on 14.8 volts, I’m working on one now that will use 11.1 volts. I’ve heard really good things about the charger Michael mentions, though I’ve never had issues with the cheaper chargers to where I’ve felt it necessary to spend even that (reasonable) amount of money on one.

Later,

K

#18

Michael, I will consider a new charger. I haven’t had the issues while charging the batteries, its been with them connected or what not so it may not be my first course of action, and while what Kevin said, it seems as if the charger does handle the greater MaH well, which I would back up since I haven’t burnt up any charging. But what I have definitely taken is that instead of throwing the batteries on a basic charger like that and leaving them charging for an extended period of time, it would be better to keep them on, only for a certain amount of time, correct?

My first course of action will be to purchase some new 11.1v with the higher Mah’s to ensure longer run time. And this way I will be sure that I won’t go over the max voltage for the airwire boards and see how that works with the C-21’s speed out put.

And I thank you all for the great feedback. This topic is now like broken spanish for me instead of that complete smack your head against the wall language barrier. ha ha…

Matt

#19

Matt,

Yes, a pre-determined charge interval is desirable. The Li-ion cell OEM manufacturers suggest that these 18650 cells/batteries be charged at rate greater than the charger you have can provide if anything but a 2200-2600mAh battery is utilized… While I am aware many modelers are using these under-powered chargers its simply NOT recommended practice. As I alluded to previously, worst case these cells should be charged in approximately 3 hours. Lithium cell technology does not support TRICKLE or slow charging, in fact its detrimental to cell life at the least.

A 4400mAh pack charged with a 1.5A charger falls within the allotted time frame, but falls well short of the recommended charge current for this capacity battery. Average charge current for a “standard charge” depending on which OEM cut sheet you refer to suggest 0.5 - 0.8A of capacity. The 1.5A charger you have provides a charge rate of 0.34C for a 4400mAh battery.

2200x.5=1.1A (2200/1000=2.2A) 2.2x.5=1.1A

Stacking the assembled batteries in parallel; which is atypical requires addressing the need for more charge current by a factor of the batteries in parallel.

4400mAh battery is comprised of two 2200mAh batteries in parallel, 4400x.5=2.2A

6600mAh battery is comprised of three 2200mAh batteries in parallel, 6600x.5=3.3A

SEARCHing for OEM specifications will garner charge rates; type in 18650 cell specifications, include one of the following; Panasonic, LG Chem, Sanyo, Samsung and there are others OEM’s too.

Charge recommendations run from fast charge at 1C (battery capacity multiplied by 1.0) and standard charge rates of 0.5-0.8C (battery capacity multiplied by .05-0.8)

C = battery capacity in mAh or Ah. 2200mAh battery divided by 1000, becomes 2.2Ah battery.

1 ampere is equal to 1000 milliAmps, or 1 Amp.

Michael

#20

Michael, I want to bring something to the fore.

One thing you are saying, (or at least I am hearing) is that charging a lithium chemistry battery significantly under the manufacturers recommendations is not necessarily a good thing.

I do know that in other chemistries, doing so promotes growth of undesirable compounds in the battery which hastens its demise.

So this is also true for lithiums in your experience?

Greg