Custom power supply - an idea

[zux]

I think its important to note that you should only attempt to modify lipo batteries if you REALLY know what you are doing.

They are dangerous and a friend of a friend of mine DID set his house on fire!! after doing stupid things with them.

After all they recommend you charge them in fire proof bags!

For Lego applications I think they hold good potential, but only in the hands of experienced electronic hobbyist or professionals!

I came with same results after I've investigated local R/C supply web site for available parts. Found funny (or not) thing - description for any "LiPo fireproof storage" items have a link to local forum discussing the reason why these are needed and accident photos. Decission I made is that you can go for custom LiPo if you really-really-really need and just cannot live without them in your MOC. You must be cautious while operating/storing/charfing and alsways keep an eye on the battery.

Well I think I'll stick with LEGO batteries, just don't want to have all that headache.

Edited June 21, 2013 by zux

[Blakbird]

Decission I made is that you can go for custom LiPo if you really-really-really need and just cannot live without them in your MOC. You must be cautious while operating/storing/charfing and alsways keep an eye on the battery.

I both agree and disagree with this. It is certainly true that Li-Po batteries are dangerous and can explode if over charged or shorted. However, as long as you are using a proper Li-Po charger and are not modifying your packs (which is the greatest possibility for shorts arises), there is really no danger. I have many dozens of Li-Po batteries in my garage for various R/C uses. They are all just thrown into a cardboard box with all my spare parts. There is absolutely no cause for concern. In my opinion, their advantages far outweigh their dangers. However, anyone who has absolutely no idea what they are doing or has no interest in taking proper care of their batteries should probably not use them.

[efferman]

interesting topic, sorry if i highjack this with my question.

an standard pf battery box has an security switch which disables the delivering of electicity when it reaches 900ma. when i use an electronic speed controller of an 2,4ghz RC unit. they can deliver multiple times the 900ma when i use an third party battery . is it possible, that a power function motor which stalls at an obstacle, sucks so much amps that it become a smoking signal device?

[Zerobricks]

All motors have their own internal PTK protection.

[efferman]

ptk means overload protection?

[Boxerlego]

Here are some of my thoughts on this custom power supply and my own personal attempts at a custom power supply. This one down below can connect with terminals on a 9v battery, like the one Sariel shows in the opening post. The 9v battery would be very useful for supplying power to a PF V1 IR receiver with a PF servo. The thought on this is for Lego vehicles to use the 9-volt battery to power the PF servo for steering along with lights and use a separate battery pack dedicated at powering the drive motor or motors. This drive battery could potentially be a 12v or 18v Li-Po battery but right now all there is the 8878 7.4v Li-Po battery. For a good quality fast Lego RC car to exist it must be a premeditated structure with several aspect to the overall design. Look at the 32x32 base plate for a Lego house for a moment. The 32x32 base plate is the perfect example for what it takes to make a excellent Lego RC design. First it provides a soild structural platform to build on which brings me to the Second example, Evolution. The Lego space base plates are the best way to show a example of the evolution for the 32x32 base plate. The space base plate brought a whole new vision at what a base plate could possibly be. Finally the Third example and to simply put it "It is LEGO" because of the fact that Lego maintained the square or rectangle design with their base plates that allowed it to be joined together as one layout.

Here is a 8-cell rechargeable battery box (battery voltage should not be more than 10.6-volts) that was used to power the 9398 Crawler with the Power Puller tires and it work out pretty well.

9V batteries have a rather high internal resistance and are not good for high current needs. They work great for stuff like monorail, but I'm not sure I'd use them for Technic motors

Here's a good site/list regarding internal battery resistance :

http://www.learninga...rnal-resistance

That is a very great web site for this stuff. It has help alot.

anyone who has absolutely no idea what they are doing or has no interest in taking proper care of their batteries should probably not use them.

I use a Hardware Monitoring program on my Laptop computer to observe its battery current and charging voltages.

All motors have their own internal PTK protection.

I'm sure you meant PTC resistor.

[msx80]

I too feel like the battery pack is too big. Not only that, but ALL lego electronic components are very big, for example motors or controllers, not to speak of Mindstrom motors and programmable bricks, they're HUGE. I know that they're designed with all kind of protection circuitry, and with children in mind, but sometime i'd like to have smaller, more "standard" parts. As a robotic hobbist, i've used "naked" motors, drivers, sensor, etc and everything was small. something like an arduino mini https://www.sparkfun.com/products/11114 has most of the functionality needed to program a robot. Motors like this one https://www.sparkfun.com/products/8912 are powerful enought to move any technic set.

Actually, the huge size and difficult to interoperate with non-lego electronics has always held me from purchasing a Mindstorm set. I'd like a more adult- and electronic-savy oriented system..

[750ACE]

I have seen this video before and interested in the battery setup. I wonder why the scene with 8t gear reduction then next scene stock gear setup?

[Boxerlego]

I have seen this video before and interested in the battery setup.

The battery pack I used can hold up to 8 AA batteries and is roughly the same size as the 8881 battery box in all dimensions so it was a snug fit where the original battery box was. Because this battery pack was able to hold 8 batteries. This allowed rechargeable AA batteries to provided 9 volts or more to the L motors.

I wonder why the scene with 8t gear reduction then next scene stock gear setup?

For comparison reasons. Just look at how hard the wheels struggle to get up the hill in the end.

[Hopey]

So this got me thinking, and I think I might have come up with the smallest possible PF IR setup without modifying parts:

Although nothing's modified, I have used the "hack" of putting the two pieces of aluminium foil on the top of the light grey end of the adapter cable in order to power all 4 pins. Also note that I've only used one end of this cable, the other end is just sort of dangling off uselessly.

I even whipped up a quick little car:

It seems to go well enough, although I'm not sure how well it would do under a more significant load.

It's not significantly smaller than the 8878, but given that I already had all of the parts (the battery pack was from one of my pre-dark ages sets), it's a better option for me than spending $100 or so on an 8878.

[Doc_Brown]

WOW I tried this before I continued reading what you wrote, and it didn't work for me, lol.

How do you do the Aluminum hack?

[Hopey]

WOW I tried this before I continued reading what you wrote, and it didn't work for me, lol.

How do you do the Aluminum hack?

Like this:

Not my idea, someone posted it earlier in the thread. I too noticed that it didn't work and was about to cut up some cables to make an adapter when I spotted the above picture.

For some reason, I could only get it to work on the light grey end, although by all rights it should work on the other end too. Which would mean the end wasn't just dangling off.

[The Ghost Racer]

Some time ago I did this.

One important thing to consider is the amperage, if it is too low, the engine will not develop enough power .. I used a rechargeable battery 8.4V 220mAh and if I'm not mistaken, while usually us 6 batteries 1.2V 2100-3800mAh, the difference in power output is remarkable, I recommend you take this into consideration before changing an electrical connector ..

Edited July 14, 2013 by The Ghost Racer

[Boxerlego]

So this got me thinking, and I think I might have come up with the smallest possible PF IR setup without modifying parts:

Although nothing's modified, I have used the "hack" of putting the two pieces of aluminium foil on the top of the light grey end of the adapter cable in order to power all 4 pins. Also note that I've only used one end of this cable, the other end is just sort of dangling off uselessly.

I even whipped up a quick little car:

It seems to go well enough, although I'm not sure how well it would do under a more significant load.

It's not significantly smaller than the 8878, but given that I already had all of the parts (the battery pack was from one of my pre-dark ages sets), it's a better option for me than spending $100 or so on an 8878.

Call it whatever you want but your truly modifying that LEGO electrical connection.

[Someonenamedjon]

I have actually hooked up a 9volt battery to a lego nxt, and i worked fine, but be sure to find the right two ports to plug it in. the configuration of the batteries is like this:

fig 1

__ __ __ __

- + - + - + - +

+ - + - + - + -

_ __ __ __ _

_ = the metal connectors

+= positive

- = negative

IF you were to "pull" this into a string it would be like this

fig 2

_-_+_-_+_-_+_-_+_-_+_-_+_

IF you connect it wrong, it will short and start to smoke, so you need to connect it on the two single underscores on the fig 1.

To hold this in place you will need to soder the ends.

[Hopey]

Call it whatever you want but your truly modifying that LEGO electrical connection.

It's really a matter of opinion I guess, but I'd say that the distinction is whether or not it's reversible. I can simply pull it apart and the parts are all in exactly the condition they started with.