Dual PF Battery Box Power Tutorial

[Boxerlego]

Hello fellow LEGO enthusiasts, I am Boxerlego. I want to Introduce myself along with this technical tutorial on a dual PF battery box setup. This no hack, this is science and knowledge along with real experience with each of the devices and their respective function. I will explain thoroughly why this works and why it is absolutely safe for the IR receivers and motors.

First thing is some battery safety. It is very Important that you are using the same type of batteries for both the battery boxes. Never connect up two dissimilar types of batteries together. Connecting two 9 volt battery boxes together is very safe to do, nothing is going to "burn up" on you when connected together as mentioned. Each of the electrical connections are made entirely out of Lego and combines both style of electrical connections to get working. There will be a simple alternative method to hook up the dual battery setup only requiring the PF extension wires.

Moving to motors. I suggest on using the PF L or XL motor or a 5292 buggy motor with this battery setup. This is not for powering servo motors or micro motors old the old 9V motors. It is important to know that there is a resettable fuse protecting each of the suggested motors along with the battery boxes and IR receivers. I do not recommend putting the voltage over 16 volts on the Lego motors. Most motors typically can handle 12 volts.

There are many things to understand about the electrical function that is at work here. I have created Two simple pictures detailing the two electrical functions and how they both end up at 18 volts. I will start with the #2 picture. The #2 picture represents when the battery boxes are connected together in series providing you with a +18 volt power. Understand that all the electrical wires are connected together to establish a electrical path, directly connecting both the battery boxes together to function as one combined battery box for the motor. The #1 picture represents using the dual IR receiver connection and how you can safely create a voltage gap between a positive(+) and a negative(-). Neither of the IR receivers is ever exposed to the same load the motor is receiving. Instead, each of the IR receivers is carrying the load of their perspective battery box. This voltage gap creates the theoretical 18 volt supply for the motor.

You will need

2x 9V PF battery box

2x IR receiver

3x PF extension wire

2x 9V Motor Wire

1x IR switch remote

1x of the suggested motors

I will start with the two 9V motor wires...

Connect the two 9V motor wires on a 2x6 plate like so...

Look carefully at the short wire and how the electrical contacts are Aline...

Connect two of the PF extension wires together with a 2x2 plate...

Put a red and blue 1x2 plate on to the PF extension wires...

Connect the PF extension wire setup to the 9V motor wire setup...

This is what is should look like...

Hook up your battery boxes with the IR receivers...

(Important Note: If you are doing this with NO IR receivers, the switches on the battery boxes should be turned on opposite directions of each other when connected with the motor.)

Make sure both IR receivers are set on the same channel...

Connect the blue PF cable to the blue terminal on one of the IR receiver And then On the other IR receiver connect the red PF cable to the red terminal...

(Note: If your doing this with out the IR receivers. Connect each of the cable to a separate battery box. Remember to switch the battery boxes on in opposite directions)

Connect both the switches on the IR remote together as one and set on the same channel as the two IR receivers...

It is very Important that the two polarity switches on the IR remote are switched opposite of each other...

The 9V motor wire is where you will connect your motor to...

When connecting up a PF motor simply connect the PF extension wire on top of the 9V motor wire and the PF motor on top of that and you ready to go.

Here is a test to see if this increased voltage will cause any kind of damage to the motor when pulling up this 7.5 lb weight.

The first test shows the safety fuse in action. Next I put the M motor to the 16 volt power pull test. The final video is a demonstration that no matter how big or small the battery is, a motor will behave the same as long the volts are the same.

Edit: The information in this tutorial will be improved upon periodically.

Edited January 1, 2013 by Boxerlego

[Kierna]

That's bad to the bone. Clever setup! 400rpm or so from an XL motor! I am the lone soul trying to make a Lego RC bike, and I love the possibility of more POWER

I have a few questions:

Would this be safer for the motors using rechargable batteries, making 14V-15V? Have you noticed any damage or burning at 18V?

Can any more motors be added to the un-used ports on the IR reciever, say, a PF servo motor?

[DLuders]

@ Boxerlego: Welcome to Eurobricks! In regards to your apparatus, could you confirm that:

1) You used a total of 12 ea., new 1.5-Volt AA ALKALINE battteries (to get 18V), and not 12 ea., 1.2V RECHARGEABLE AA batteries (14.4V)?

2) The motor(s) don't get too hot (and burn up) with an EXTENDED test, lasting far longer than the 6-second demonstration you have in your video?

3) The Power Functions IR Receivers are the old (version 1) type, and not the newer v2 type? See Philo's

below:

[D3K]

That's bad to the bone. Clever setup! 400rpm or so from an XL motor! I am the lone soul trying to make a Lego RC bike, and I love the possibility of more POWER

With great power comes twice the weight!

[Kierna]

With great power comes twice the weight!

Not if two rechargable battery boxes are used! Combined, they would weigh less than one AA battery box full of AA's. Not quite twice the power, but 14.4V is still plenty

I'll be spending a bit of money on lego in 2013...

EDIT:

Welcome Boxerlego, and thank you for bringing useful knowledge to the forums

Edited December 29, 2012 by Kierna

[Zerobricks]

Just what i was thinking few days ago, but in a way of overvolting an RC motor to make a heli... Now all i need are some Lego education turbine propellers!

[Boxerlego]

That's bad to the bone. Clever setup! 400rpm or so from an XL motor! I am the lone soul trying to make a Lego RC bike, and I love the possibility of more POWER

I have a few questions:

Would this be safer for the motors using rechargable batteries, making 14V-15V? Have you noticed any damage or burning at 18V?

Can any more motors be added to the un-used ports on the IR reciever, say, a PF servo motor?

Hi Kierna, Good question. The Un-used ports are technically the same ports you are connecting together. You can have a motor on one of the IR receivers un-used ports, though you would power every motor at once. This power setup is not for Servo motors... Now this does not mean you can have another IR receiver connected on one of the dual battery boxes controlling a Servo motor.

I have used Alkaline and Rechargeable battery types there both safe to use. I have never gone above 16 volts on any of the motors yet.

@ Boxerlego: Welcome to Eurobricks! In regards to your apparatus, could you confirm that:

1) You used a total of 12 ea., new 1.5-Volt AA ALKALINE battteries (to get 18V), and not 12 ea., 1.2V RECHARGEABLE AA batteries (14.4V)?

2) The motor(s) don't get too hot (and burn up) with an EXTENDED test, lasting far longer than the 6-second demonstration you have in your video?

3) The Power Functions IR Receivers are the old (version 1) type, and not the newer v2 type?

Hi DLuders, I can confirm these inquiries. I used rechargeable AA batteries in the video. They were fully charged and combined together creating a 16 volt gap to power the XL motor. Understand that the motor wont burn up, there is a resettable fuse to prevent this kind damage occurring. The video is short and not exactly flat out convincing. I will make the video better in display how safe this is for the motors. And Yes the IR receivers are old (version 1) types and not the newer types.

Edited December 29, 2012 by Boxerlego

[BachAddict]

Since you're using 9V wires, wouldn't it be possible to reverse the polarity in there instead of using both outputs of the receivers?

[Boxerlego]

Since you're using 9V wires, wouldn't it be possible to reverse the polarity in there instead of using both outputs of the receivers?

Hello BachAddict. In order to get the additional power output you will need two battery boxes along with two IR receivers. Doing this with a single battery box and IR receiver you will gain nothing in power for the motor and a fuse will most likely stop this.

[Boxerlego]

I have recorded some more test with the Dual Battery box. I even tested out the M motor with the extra volts. I got 660 rpm out the M motor and surprising its quite powerful too.

@ DLuders, Thanks for the welcoming, I think the video is very good addition to the page. I guess you got to shunt both the battery boxes and have two V2 IR receivers to run a RC motor at higher voltages as well. I don't have a 5292 RC motor to test, but I can assure you it will love the extra power. Just keep it safe around 12 volts.

Edited January 1, 2013 by Boxerlego

[DLuders]

@ Boxerlego: When you say you had to "shunt" your Lego Power Functions Battery Box, did you do the same thing that Ximbary did on this Eurobricks post? He wrote:

"i dont have a working camera right now, this is all i can provide at this point:

all you have to do is to connect the 2 metal ends of this HL5L thingy as in this picture.

i have never done solding before but i got it done with an extremely cheap solding gun (or whatever its called) on 4 battery boxes without fails within half an hour. its really a piece of cake.. but you have to take care that the solding is done rather thin or you will not be able to push the button of the battery box towards the right position anymore.." :D

[Boxerlego]

@DLuders: I have not shunted any of the fuses on my battery boxes. The only thing I have done to my battery box is fix it. When I first took apart my battery box I rip the red and black wires apart when I separated the two half's. I had to remove the broken wires and replace them. There is no room for error when replacing the large red wire and the small black wire. I got the battery box back to working order.

Edited January 1, 2013 by Boxerlego

[Boxerlego]

http://youtu.be/lba1u_IQIK0

[Zerobricks]

No credit for your idea or anything... I also found he used some of my ideas for his and also no credit..

Edit i see double the current, not voltage..

Edited January 8, 2013 by Zblj

[Boxerlego]

No credit for your idea or anything... I also found he used some of my ideas for his and also no credit..

Edit i see double the current, not voltage..

I am not trying to get credit for anything but rather show you how to properly connect two battery boxes together and understand why it is safe for the IR receiver and motors. It not like I specifically said build a helicopter with this. I want everyone to be able to know about this and use it with out fear.

Edited January 8, 2013 by Boxerlego

[Boxerlego]

I found this tread it is over 2 years old And it shows how to connect Two Ir receivers together in parallel. http://www.eurobricks.com/forum/index.php?showtopic=45953

[1974]

And the last poster in that thread is quite a prophet

[MaxSupercars]

Is someone using this Idea from Boxerlego from the first post?

Max...

[zver]

Is someone using this Idea from Boxerlego from the first post?

I've started using the same scheme a few years ago. I've plugged two AAA-PF battery boxes via two IR-receivers to one buggy motor. The result was awesome.

I've won two lego rally races with it!

Edited July 17, 2015 by zver

[MaxSupercars]

So your motors run on double voltage? No damage? No problem?

Max...

[Graydingo]

Moar power! Great info here. Thanks

[Blakbird]

So your motors run on double voltage? No damage? No problem?

No, two battery boxes in parallel would not change the voltage. It would just change the available current.

[zver]

No, two battery boxes in parallel would not change the voltage. It would just change the available current.

Yes, the battery boxes were plugged in parallel. They let motor provide more acceleration. With one AAA battary box buggy motor works bad.

[JamesJT]

Will adding 9V battery to standard battery box just increase the current available and NOT fry all my PF parts with 18V?

lego 040 by James Tillson, on Flickr

Edited October 8, 2015 by JamesJT

[1974]

There's not much point in wiring those in parallel as that 9V battery hasn't got much juice (amps) at all and they have quite different dischargerates which means they voltage might not equalize and you will be feeding voltage into the 9V battery. Not good!

It's a good idea only to put batteries in parallel that is of the same make/size and perhaps use balancing resistors as well

If you just want to increase running time with two battery boxes there's no need to put them in parallel, just swap the cable when one is flat