Large Scale Central

Phoenix 2K2 Back-up Battery

Electronics Power and Sound
#1

Just because I need to juggle one-more project; I’ve started the conversion of my Cheesy Sound Car to include on-board battery and an ESC to become a power & sound trail-car. I will maintain the ability to use it as a track powered sound-only trail car, although it probably won’t get used that way often. I’m trying to decide if I should keep the Phoenix back-up battery connected. If I do, I realize that the on-board batteries will be charging this un-needed battery when running in battery mode. If I simply remove it, then I will loose idle sounds when on track power. Would it make sense to yank out the Phoenix battery and allow my on-board battery to be plugged in to the Phoenix back-up battery connector when running on track power? I think the Phoenix battery is 4.5V and my on board pack will be 11.1V. Is this a problem? Does the Phoenix have regulation on the battery input? If not, a 5V regulator in my connection circuit would be possible. Just for reference, all the connections on the Phoenix are easily accessible via the removable roof on the car…

One speaker is going away to make room for batteries and an ESC.

#2

Jon if you want to replace the battery you can. If you are going to use track and battery power you can have the board powered by both. Are you going to use a DPDT switch to change from one source to the other? If so you can connect to the board from this switch but will have to use a bridge rectifier because of the track power source . If you are just going to use the battery as a source no need for rectifier. Card is polarity sensitive make sure you hook it up reight or you will blow the board.
Mike

#3

Yes. There will be a 10A DPDT switch that selects the power source. This switch will be located between the track pick-up and the output of the ESC. My initial plan was to keep the Phoenix on the output side of this switch. I realize now, looking at my drawing, with that design the Phoenix would have no power when idling even when in battery mode :frowning:

Looks like I need to think some more about where the sound gets connected.

#4

OK, a quick trip to the Phoenix website to review the Battery R/C wiring diagram yielded enough information to draw up this design for the DC side of the trail car…

(http://lsc.cvsry.com/Post2/TrailCar-Phoenix2K2.jpg)

Making the batteries removable for charging greatly simplifies the wiring and gives me options. The LiIon batteries will supply the back-up power to the 2K2 in both situations. In Track Power mode, the track pickups will supply primary power to the 2K2 and can also function as additional power pick-ups for the locomotive via the plug. This is my “keep busy during the snowstorm” project for this weekend.

#5

I’m a bit confused here.

The phoenix 2k2 backup battery is rated at 3.6 volts… it goes to a special connector.

So, seeing it in parallel with an 11.1 volt battery should cause it to overheat and become damaged.

So in the circuit above, I see the “phoenix battery” not connected to the proper location, and also references to improper voltage.

If you want to have it run on track power and have idling sounds when the power on the rails is zero, you need that battery. There is a recharging circuit built in, and I can tell you for sure, that you do not want to feed an overly high voltage to that input (the little 2 pin connector I believe), a friend of mine just tried replacing the 3.6v backup battery with 2 9v “transistor” batteries, i.e. 18 volts… the board is now damaged.

I hope I’m not misunderstanding your intentions on wiring.

Regards, Greg

#6

Hey Greg -

Thanks for the comments.

I guess my labeling is not clear. I should have labeled it Phoenix Battery Connector. This hookup is taken directly from the Phoenix documentation. The 3.6V battery is not used. The 2K2 handles up to 12V at the back-up battery connection. This allows for idle sounds when the ESC has no output. Tying the ESC Motor output to pins 1 and 2 allows for voltage based triggering for diesel sounds. What I didn’t show is the 100 Ohm resistor at both pins 1 and 2 between the 2K2 and the motor output of the ESC.

According to the Phoenix documentation, feeding more than 12V to the battery connector will damage the board, so your friend’s experience agrees with the info that I have.

Before I hook it up this way I will give Phoenix a call and confirm that the battery input jack will handle the 11.1V I plan to feed it and the charging circuit will no wreck havoc with my LiIon pack.

#7

Thanks Jon, nice to know the max voltage at the backup battery connection. Seems a bit strange though, I wonder what range of batteries it will “charge”? Sounds a little strange, must be a constant current output, not voltage.

So, the battery input will take up to 12 volts, but it must also be charging the battery on track power. It would be really nice to know just what the battery charging circuit does… I’ll guess it’s a “trickle charge”, constant, but low current. That is usually dangerous to lithium ion packs, overcharging them will cause catastrophic results.

The charging current may be low enough that it would take some time to get to this situation, but theoretically, it would eventually happen left on the tracks long enough.

What I would try to extract from Phoenix is exactly what voltage and what current is presented to the battery when charging.

Will be very interested in their response.

Regards, Greg

#8

I rarely plan to use this car on track power. For now I think I will just make sure that the LiIon batteries are removed if using track power. Correction on the voltage. I checked the manual again and it is 20V. I’ve heard polarity must be observed, so that could have been your friends problem. Here is their RC Hook-Up diagram…

(http://freightsheds.largescalecentral.com/users/jrad/_forumfiles/2k2_RC.jpg)

A quick thought - Wouldn’t a pair of diodes keep any charging current from reaching the battery? I have plenty in-stock so they will be added for protection.

#9

Yep, only need one diode on one leg of the battery… sounds like a safe idea…

Greg

#10

When using the P2k2 with traction battery only power into the terminal shown in Jon’s drawing there is no need to connect terminals 1 & 2 on the P1 strip if it is steam sound.
Unless of course you do want to have the correct direction and stop toots and/or you are using the diesel version. In these cases you MUST use the shown 100R resistors on the motor reference voltage detectors to limit the charge current feeding into the traction battery pack.

#11

It works! I ended up using two diodes on the back-up battery lead and did use the 100 ohm resistors on the motor lead. This board will be diesel sound most of the time.

Edit to add an operational note: An on-off switch in the battery lead to the 2K2 is a requirement for this set-up. Without it, once the board shuts down, it will not re-start again. I need to work in a second switch if I want to use the Li Ion pack as back-up battery when running track power as I don’t want my R/C Rx and ESC powered when running on track power.