4 Train Motors on SBrick

[pe668]

I'm running train motors off a sbrick and powering using a 8878.

It runs fantastic for a time and then shuts off. Not sure if this is current load or heat, by the Sbrick or 8878?

I turn everything off and wait a short time and I can turn it all back on and it works again (for a time).

So it's not the motors sucking the battery flat.

Any help would be appreciated.

[Dutchiedoughnut]

Sounds like an overheating protection in the battery. It might be the S-brick overheating as well. Can you use the AA battery box as a test?

[Bruce]

I have found that the AAA battery box and the rechargeable battery run for two hours then turn off. Turn back on and will run another two hours if the batteries do not run down.

[dr_spock]

I think that is normal behavior of the 8878 rechargeable battery. It turns itself off after about 2 hours.

[legoman666]

It is not overheating, it could be the overcurrent protection kicking in. It is a resetable fuse. I bypass it in my AA battery packs since it limits the current to a mere 800mA (IIRC).

Edited March 22, 2016 by legoman666

[pe668]

It is not overheating, it is the overcurrent protection kicking in. It is a resetable fuse. I bypass it in my AA battery packs since it limits the current to a mere 800mA (IIRC).

Do you have any knowledge regarding the protection in the 8878?

If I bypass the limiter will that damage the sBrick?

PS. I'd be more than happy with a 2 hour cut off. I'm lucky if they are still on the table for an hour. lol

[legoman666]

Do you have any knowledge regarding the protection in the 8878?

If I bypass the limiter will that damage the sBrick?

PS. I'd be more than happy with a 2 hour cut off. I'm lucky if they are still on the table for an hour. lol

The lipo pack has a 750mA resettable fuse. Bypassing it will not damage the sbrick, but its possible you could damage the lipo pack. If you're worried, replace the 750mA fuse with something like 1.5A or 2A. That way you're still protected but have some more headroom for the sbrick.

http://www.philohome.com/batteries/84599-6.jpg red arrow points to fuse.

Edited March 22, 2016 by legoman666

[pe668]

Thank you legoman666 and the others, much appreciated

[Dutchiedoughnut]

D_spocks answer seems much more likely. If you dont have an overcurrent protection for two hours, then thats not your problem.

I would expect an overcurrent error to show itself after a minute. Two hours is a time limit.

[legoman666]

If you long press the power button to turn on the pack, the power LED will blink at you to indicate that you have bypassed the 2 hour limit.

[Brickthus]

I'm running train motors off a sbrick and powering using a 8878.

It runs fantastic for a time and then shuts off. Not sure if this is current load or heat, by the Sbrick or 8878?

I turn everything off and wait a short time and I can turn it all back on and it works again (for a time).

So it's not the motors sucking the battery flat.

Any help would be appreciated.

Sounds like the 4 motors are exceeding the current capability of the S-Brick.

I would get a second S-Brick and run 2 motors from each one on the same communication channel.

It is also possible you are going over 800mA LiPo battery current trip, so a second LiPo for the second S-Brick would be best.

I have found that the LiPo attempts to restart a load of 1300mA (4 train motors + gearmotors + lights). If it is shutting off without restart then maybe it is the S-Brick tripping.

4 train motors would definitely exceed the design intent of an IR Receiver and LiPo battery; I don't remember the S-Brick's current limit.

Mark

[dr_spock]

From the Sbrick specs, it can handle:

Continuous current per channel: 3A, if thermal limits are honoured

Peak current per channel: 3.5A

[MajorAlvega]

Unless you modified your LEGO battery, you can't get much more than 800 mA from it so the internal overcurrent protection is triping.

The SBrick can handle short peaks of 3.5A per channel and VERY SHORT peaks of 6A total but you need a custom battery like those used in RC hobby models.

Sorry, there's another possibility... is the battery really shutting off or is just the SBrick shutting off or even just loosing connection?

My Android (Sony Xperia Z1) had some bluetooth connection problems with the SBrick. Things got much better with firmware upgrade (4.2b to 4.8) and even better with last App upgrade.