Connecting 4 XL motors to 1 SBrick

[andrey_belen]

Hello! I've got a question: I am building a model and want to put 4 xl motors there, but I have only got 1 SBrick and can only connect 1 battery to it. Of course, one battery is not enough for such amount of motors. How do I solve this problem? Connect 2 batteries together? 3s LiPo? Help plz

 

[Aleh]

It depends whether all motors is going to rotate simultaneously or not. If yes - put fresh batteries.

[Marxpek]

Here is an idea maybe: connect 2 extension wires from 2 battery packs (newer brighter leds style) to a 2x8 9V lead plate, and connect a 3rd from the 9V lead plate to the s-brick. just make sure not to switch the polarities on you BB's, that will kick in the protection for sure.. maybe there is a more forward solution that i forgot..

1 hour ago, andrey_belen said:

3s LiPo

DO NOT DO THIS, unless you have a voltage regulator on it, the 12,6 volts  output on a charged 3s LiPo WILL fry your s-brick.

[Marxpek]

come to think of it, there are non Lego approved solutions of course, like making your own extension wire with 2 regular connectors, or shunt the batterybox (remove the current protection) that way you only need 1 battery box if you have decent batteries, but then again, that could potentially melt something in the battery box or wires if you short it out. 

Edited December 22, 2018 by Marxpek

[andrey_belen]

22 minutes ago, Aleh said:

It depends whether all motors is going to rotate simultaneously or not. If yes - put fresh batteries.

Yes, they will, but I want the batteries to be rechargeable, so putting "fresh" batteries doesn't really work. If I put full-charged batteries there, it stars squeezing or something, and the motors stop rotating.

 

7 minutes ago, andrey_belen said:

Yes, they will, but I want the batteries to be rechargeable, so putting "fresh" batteries doesn't really work. If I put full-charged batteries there, under stress it stars squeezing or something, and the motors stop rotating.

  

 

[The Duke of Wirdum]

Most rechargeable batteries are 1,2V= in stead of 1,5V=. With 6 batteries that adds up to 1,8V= less. That might not seem a lot but it's still 20% loss.

7.2V= volt in stead of the required 9V=

1,5V= recargable batteries do exsist but you'l have too look for them and you'l need the right charger. Plus the fact that most rechargeable batteries preforme less under load than a non-rechargeable battery.

If you realy want to go rechargeable, go for the lego rechargeable battery pack.

[mocbuild101]

On 12/23/2018 at 1:02 AM, andrey_belen said:

Of course, one battery is not enough for such amount of motors.

I think it will be actually, I haven't got enough XL-motors to test it, but the MOC in this video only uses one (presumably unmodified) battery box with 4 XL-motors: https://youtu.be/zpJAtAettJs?t=48

As for using rechargeable (Ni-Mh, not Ni-Cd) batteries, provided you've got fairly good quality ones (Duracell Recharge Ultra or Panasonic Eneloops for example), they can actually perform really well in comparison to alkaline batteries.

 

On 12/23/2018 at 5:40 AM, The Duke of Wirdum said:

If you realy want to go rechargeable, go for the lego rechargeable battery pack.

It's not really that simple, it all depends on what you'll be using it for.

The Lego rechargeable Li-Po battery is better for most low-load applications, as it does have a bit more voltage than rechargeable Ni-MH batteries.

However, the Lego Li-Po battery still has current protection in it, so for higher-load applications, it won't do much better than Ni-MH batteries.

Also, if you use the Ni-MH batteries with a shunted (current protection removed) battery box, they can actually out perform the Lego Li-Po battery, especially when it comes to powering buggy-motors.

 

On 12/23/2018 at 5:40 AM, The Duke of Wirdum said:

the required 9V

9V is just the voltage PF was designed for, it can actually go down to as little as 4V before it becomes unusable. 

Edited December 24, 2018 by mocbuild101

[MattL600]

15 hours ago, The Duke of Wirdum said:

Most rechargeable batteries are 1,2V= in stead of 1,5V=. With 6 batteries that adds up to 1,8V= less. That might not seem a lot but it's still 20% loss.

7.2V= volt in stead of the required 9V=

1,5V= recargable batteries do exsist but you'l have too look for them and you'l need the right charger. Plus the fact that most rechargeable batteries preforme less under load than a non-rechargeable battery.

If you realy want to go rechargeable, go for the lego rechargeable battery pack.

Therefore OP can use 2s LiPo Batteries, which provide a 7.4v output.

You might want to use one of these;

https://hobbyking.com/en_us/turnigy-battery-4000mah-2s-30c-lipo-pack-xt-60.html?countrycode=AU&gclid=Cj0KCQiAgf3gBRDtARIsABgdL3mpvgMCI1beNugnx-QitkqpvQXEcDM6vxkBna9k8KJcv2Ab1pPQupgaAj5HEALw_wcB&gclsrc=aw.ds&___store=en_us

It uses x60 connectors which are easy to solder pins onto (from a sacrificial connector of couse), has 4000 MaH of energy to use and also is rated at 30c meaning that it can output more power on demand than the usual 20c batteries.

Also, don't use NiCad or NiMH batteries, they are inefficient and are not energy dense

 

Good luck!

[mocbuild101]

41 minutes ago, MattL600 said:

Also, don't use NiCad or NiMH batteries, they are inefficient and are not energy dense

They're not that bad, they just aren't as energy dense as LiPos. They are certainly a lot more resilient than LiPos - they can be discharged to almost empty without damaging the cells, and also don't require a specialized charger. 

[MattL600]

11 hours ago, mocbuild101 said:

They're not that bad, they just aren't as energy dense as LiPos. They are certainly a lot more resilient than LiPos - they can be discharged to almost empty without damaging the cells, and also don't require a specialized charger. 

NiMH or NiCad batteries in the rechargeable AA form are inefficient and are more expensive since you still have to buy the charger, if you buy a lipo charger you can use it with your other rcs since it charges using a jst plug.

 

[mocbuild101]

3 hours ago, MattL600 said:

NiMH ... batteries in the rechargeable AA form ... are more expensive

I'll give you that one... Good quality Ni-MH AA batteries (i.e. the ones that give comparable performance) are on average more expensive per volt than Li-Pos...

Anyway, I think we're going a bit of topic here... 

Edited December 24, 2018 by mocbuild101

[dr_spock]

If you want to use 3S LiPo, you'll need DC-DC regulation to a Sbrick safe voltage to avoid toasting its motor driver ICs. 

XL motor specs

No load current: 80mA
Stalled current: 1.2A

Sbrick specs:

Recommended operating voltage range:	4V - 10.8V
Recommended maximum continuous current per channel:	1A
Absolute maximum voltage:	11.8V (Above this voltage, the motor driver ICs will be damaged)
Absolute maximum continuous current per channel:	2A, thermal shutdown is expected at this level.
Absolute maximum peak current per channel:	3A
Absolute maximum continuous current intake from "0" and "9V" pins:	3A
Maximum continuous current intake from C1-C2 (using old, or 9V power supplies):	2A