Could you connect Lego power supplies in series or pararell!?‽

[AI toothbrush]

So I was thinking about using some parts in ways they weren't meant or in a unique way. But I found something much better than that. THE LEGO 9V SYSTEM. I saw connectors that are stackable on bricklink. Could you connect them in a way so the result is a parallel or series connection? Just think about the possibilities. Like 18 volt to a motor or not having to change the batteries in your set for double the time. You could also take the rechargeable battery boxes and make a fake and at the same time totally Lego buwizz clone. And it would perform even better. If I'm right the buwizz can supply 11.4v while a rechargeable battery box can supply 7.5v so 7.5v*2=15v! Please tell me that this theory is true.

Edit: Ok I found it the names are plate with contacts. I found it on bricklink.

Edited February 14, 2021 by AI toothbrush

[Zerobricks]

Double the voltage, double the current, 4x the power = 1x fried electronics and motors.

[Maaboo the Witch]

Is there seriously an interrobang in the title of this thread?

[dr_spock]

Connecting them in parallel could provide longer running time.  In series you could overheat or blow the voltage regulators in the controling electronics like the IR receiver, etc.

There's always one way to know for sure.  Try it and report your findings. 

 

[AI toothbrush]

9 minutes ago, Zerobricks said:

Double the voltage, double the current, 4x the power = 1x fried electronics and motors.

https://youtu.be/6byrPRQihMQ yeah the overload protection... I hope the bigger motors have more tolerance.

2 minutes ago, dr_spock said:

Connecting them in parallel could provide longer running time.  In series you could overheat or blow the voltage regulators in the controling electronics like the IR receiver, etc.

There's always one way to know for sure.  Try it and report your findings. 

 

Guess I'll have to try it. 

[syclone]

Well, the mere fact of it being possible is not a reason to actually do it. Both methods have huge drawbacks and barely any (if none) benefits.

1. Parrarel connection.

Available by default with both 9V and PF, main drawback is the weak electronics in receivers and batteryboxes, as well as the size and weight of the power supplies. If you really needed so much capacity so as to require 2 (or more) power supplies you wouldn't want to hook that to a single powerline or PF receiver as it would be safer being on separate circuits - the connectors aren't meant to transfer that much current through them.

2. Series connection

My advice is not to do it. Has been done before if you are purely interested in the results (the last topic about this was about a month ago). Lego electronics are meant to be used at 9V and lego motors are 12V ones, hence why even BuWizz doesn't surpass it (Ludicrous mode tops out at 11'2 V according to official specs), as it would cause damage to the motors over long usage, and the electronics would probably end up fried as it has been pointed out by Zerobricks. Damaging the wires, melting the connectors and shorting out the batteries are very real possibilities of this setup.

[2GodBDGlory]

5 hours ago, Maaboo35 said:

Is there seriously an interrobang in the title of this thread?

How do you even type one of those!

 

1 hour ago, syclone said:

My advice is not to do it. Has been done before if you are purely interested in the results (the last topic about this was about a month ago).

Yeah, there was a very informative topic on here I remember reading not too long ago.

[pleegwat]

20 hours ago, 2GodBDGlory said:

How do you even type one of those!

Compose, !, ?. Search for wincompose.

[AI toothbrush]

10 minutes ago, pleegwat said:

Compose, !, ?. Search for wincompose.

If you are on mobile you can just search for a "?" in the extra simbolums menu and hold it down.

[DrJB]

Double the current and double the voltage is 'nonsense'.

Connect in Parallel (feasible, with PF+9V cables) - double the play time, voltage is the same, current is the same, batteries last twice as long

Connect in Series (no feasible with PF) - double the voltage, might fry your components if they have no voltage protection.

Edited February 17, 2021 by DrJB

[AI toothbrush]

2 hours ago, DrJB said:

Double the current and double the voltage is nonsense.

Connect in Parallel (feasible, with PF cables) - double the play time, voltage is the same, current is the same, batteries last twice as long

Connect in Series (no feasible with PF) - double the voltage, might fry your components if they have no voltage protection.

How do you connect them in parallel with only PF?

[Toastie]

4 hours ago, DrJB said:

current is the same

This depends. In principle, you are absolutely right. Things may change though when it comes to increasing load. A stalled XL PF motor draws serious amperage when the source allows that. So without a PF receiver in between, current may reach unhealthy numbers. With receiver that one will max out, as they are overload protected.

So in the end, with two batteries in parallel, one receiver controlling power (and this limiting current), it is as you said: Doubling the run time.

Best
Thorsten 

[dr_spock]

3 hours ago, AI toothbrush said:

How do you connect them in parallel with only PF?

You might have to make a custom cable or take apart and wire the battery boxes together. The PF extension cables and other components don't seem to permit connecting more than one power source.

[DrJB]

1 hour ago, Toastie said:

This depends. In principle, you are absolutely right. Things may change though when it comes to increasing load. A stalled XL PF motor draws serious amperage when the source allows that. So without a PF receiver in between, current may reach unhealthy numbers. With receiver that one will max out, as they are overload protected.

So in the end, with two batteries in parallel, one receiver controlling power (and this limiting current), it is as you said: Doubling the run time.

Best
Thorsten 

Of course I'm right ;) ...

The current is NOT decided by the power supply. The power supply provides the voltage, and the load decides how much current it needs, based on its own internal impedance (Current = Voltage / Impedance).

So, assuming the two batteries are 'equally' charged, my explanation above holds. If the two batteries are NOT equally charged, then there could be current flow between the two batteries. I say 'could' because it all depends on the electronics in the battery pack.

19 minutes ago, dr_spock said:

You might have to make a custom cable or take apart and wire the battery boxes together. The PF extension cables and other components don't seem to permit connecting more than one power source.

I haven't played with PF cables in a while, but if I recall, you connect one cable to the first battery, the other to the motor, and the second cable to the second battery, and again to the motor. If I recall, the PF connectors can be stacked at will ... just like lego bricks

There might be other options depending on which cables you have. There is an adapter cable that has a PF connector at one end and a 9V at the other. Though here, I would be careful with polarity, or you could potentially destroy the batteries (they'll overheat first)

Edited February 16, 2021 by DrJB

[AI toothbrush]

7 hours ago, DrJB said:

Of course I'm right ;) ...

The current is NOT decided by the power supply. The power supply provides the voltage, and the load decides how much current it needs, based on its own internal impedance (Current = Voltage / Impedance).

So, assuming the two batteries are 'equally' charged, my explanation above holds. If the two batteries are NOT equally charged, then there could be current flow between the two batteries. I say 'could' because it all depends on the electronics in the battery pack.

I haven't played with PF cables in a while, but if I recall, you connect one cable to the first battery, the other to the motor, and the second cable to the second battery, and again to the motor. If I recall, the PF connectors can be stacked at will ... just like lego bricks

There might be other options depending on which cables you have. There is an adapter cable that has a PF connector at one end and a 9V at the other. Though here, I would be careful with polarity, or you could potentially destroy the batteries (they'll overheat first)

No you cant connect them like that. The PF extension cables have the underside of a 9v system connector.

[Toastie]

9 hours ago, DrJB said:

based on its own internal impedance

Which changes quite a bit with load on a motor of course. A stalled PF XL motor draws 1.8A (https://www.philohome.com/motors/motorcomp.htm) whereas with no load it draws 80mA at 220 rpm. No surprise here, this is what happens to E and B fields when you don't let them do what they want.

And yes, when there is over-current protection in the battery box, nothing much will happen, as this one will kick in as soon as TLGs decision, what over-current means, is reached.

Now, as we are reading here about 9V - PF conversion cables, custom wiring, etc., all of which I have done extensively (30 PF/Technic motor driven switch points wired up with LEGO wires = dramatically negative budget, which the higher authorities in this household never pass! So: Go cheap = DIY). The old battery boxes don't have any electronics in them. And then lets say we start out with fresh alkaline batteries. When you put these in parallel, V = const = 9 V (ideally of course), but A(max) = 2x. At least this is what I have learned back in the days, and here it is from a vendor (which does not mean at all it is correct, of course!): https://www.digikey.de/en/blog/series-and-parallel-battery-circuits.

Going back to the alkaline batteries: They can easily provide 1A (not for a long time :-) and with only 1V https://rightbattery.com/118-1-5v-aa-duracell-alkaline-battery-tests/ ) so a stalled PF XL motor hooked up to unprotected 2x9V battery boxes in parallel may well produce 2x6Vx2A = >20W in heat. That of course will not happen, as at every electrical connection, which has only a slightly elevated resistance, the plastic material around it may have hot times.

And yes, when the charge state of the batteries is different, the first deal which each other quite a bit and when peace has been announced, the leftover is available for fun.

As least this is what I make of it - but you know what? I just work here

Best
Thorsten 

 

[DrJB]

8 hours ago, AI toothbrush said:

No you cant connect them like that. The PF extension cables have the underside of a 9v system connector.

When a person answers to my comments with a 'No' ... that says there are two possibilities: either they have no clue about what I'm talking about ... or, I've lost touch and am not aware of the latest. If I recall, the original question was what happens when battery boxes are connected in either series of parallel. I do not recall the question mentioning WHICH specific battery boxes. Yes you can stack PF cables, and yes you can stack 9V cables. Now, based on the cables YOU have, can you connect batteries in parallel? I do not know. I have many different cables (I've been collecting Lego since 2003) and also many different boxes (such as shown below). Incidentally the small 9V box is my favorite. For sure, you can connect the boxes below in parallel with a 9V cable, then use the PF extension cable to go from either battery to the PF motor of your choice. If you're thinking ONLY PF cables, then you're correct. You also might be a newcomer to Lego (less than 17 years) and the pictures below would look like ancient artifacts to you :)

  

 

Since we're on the topic, I also have the following boxes, and some of them interface to a computer (with an old DB9 Serial connector). I love those boxes and the old 9V cables. To change polarity, all you need is rotate the connector by 90 degrees. Back then, one needed to understand a bit about electricity ... and now TLG has made everything 'idiot-proof' ... whether it is the PF connectors, or the reversible gear clutch.

 

 

6 hours ago, Toastie said:

Which changes quite a bit with load on a motor of course. A stalled PF XL motor draws 1.8A (https://www.philohome.com/motors/motorcomp.htm) whereas with no load it draws 80mA at 220 rpm. No surprise here, this is what happens to E and B fields when you don't let them do what they want.

And yes, when there is over-current protection in the battery box, nothing much will happen, as this one will kick in as soon as TLGs decision, what over-current means, is reached.

Now, as we are reading here about 9V - PF conversion cables, custom wiring, etc., all of which I have done extensively (30 PF/Technic motor driven switch points wired up with LEGO wires = dramatically negative budget, which the higher authorities in this household never pass! So: Go cheap = DIY). The old battery boxes don't have any electronics in them. And then lets say we start out with fresh alkaline batteries. When you put these in parallel, V = const = 9 V (ideally of course), but A(max) = 2x. At least this is what I have learned back in the days, and here it is from a vendor (which does not mean at all it is correct, of course!): https://www.digikey.de/en/blog/series-and-parallel-battery-circuits.

Going back to the alkaline batteries: They can easily provide 1A (not for a long time :-) and with only 1V https://rightbattery.com/118-1-5v-aa-duracell-alkaline-battery-tests/ ) so a stalled PF XL motor hooked up to unprotected 2x9V battery boxes in parallel may well produce 2x6Vx2A = >20W in heat. That of course will not happen, as at every electrical connection, which has only a slightly elevated resistance, the plastic material around it may have hot times.

And yes, when the charge state of the batteries is different, the first deal which each other quite a bit and when peace has been announced, the leftover is available for fun.

As least this is what I make of it - but you know what? I just work here

Best
Thorsten 

 

Thank you Thorsen, very useful information that you have provided. In the past, it was relatively 'easy' to discuss these topics but now, with 'smart' battery boxes and custom electronics/protection circuits ... the simple physics are often not sufficient... unless one has spent a great deal studying them (like you have). Cheers. 

Edited February 16, 2021 by DrJB

[Toastie]

4 hours ago, DrJB said:

PF cables are STACKABLE.

You are right (of course ) - they are stackable. But in a "restricted"/limited way:

You can stack the dark gray terminals as you wish (PF connectivity on the top and the bottom side of the terminal), so one power source can feed as many power consumers as you see fit. That is true for the PF receivers as well as for dumb PF motors, lights etc; these PF power consumers have a dark gray terminal as well. Also here you can stack them to heaven as well, i.e. stack x PF motors to one power feed, either a PF battery box or PF extension cable, light gray terminal, top side.

The extension cables have one dark gray and one light gray terminal. The latter has full PF connectivity on the top but "only" 9V connectivity at the bottom. And the 9V terminals connect to the C1 C2 lines of the PF circuitry and not the 9V GND PF lines. So without a little DIY there is no chance - as far as I know - to get battery boxes in parallel (nor in series). 

I can't remember whether the short (20 cm) PF extension cables (8886) had two dark gray terminals - I cut all my short PF cables for custom purposes - but again, one terminal PF/PF the other PF (upper) 9V lower, for sure. It is a secure way of preventing kids or purists of building a 1kV power supply or 9V one which can be used for welding - provided funds are available. But hey, there are enough 9V block battery (the PP3 size types) videos on YouTube, where they stack them in series - up to hundreds of them ... worthwhile to watch

The really cool thing though is: These PF extension cables are preventing power source stacking - and at the same time provide PF <-> 9V conversion. TLG could have ditched the latter (simply no electrical contacts at the bottom) but they haven't. 

Again: I believe all that. I just work here.

Just saw your post above has changed quite a bit - all has been said there, so sorry for all the long text up there. But maybe others are interested, maybe not ...

BTW: I collect LEGO since 1965 - well it was less than "collecting" more "getting". But lived through 4.5V, 9V, 12V, PF, PuP. Oh yes 9V - the best time of my LEGO life ... which explains maybe why my PF motors all have either pin headers or sockets or 9V terminals 

 

Best,
Thorsten 

Edited February 16, 2021 by Toastie
time travel

[DrJB]

Sorry about changing/editing my post ... I sometimes post a reply, get distracted (by work) and then come back ... If I may, I think you should 'uncross' the text in your. It is very useful information that you are providing and would make it easier to read. My collecting since 2003 comment was about my 'second' awakening. I first experienced Lego Technic with 851, when it first came out in the 80's ... I think.

Glad we reached consensus. Cheers.

Edited February 16, 2021 by DrJB

[Jesete]

Las fuentes de alimentación de bajo voltaje son de CC (Corriente continua).

Se pueden conectar en serie y paralelo con resultados diferentes.

Si están en serie, el voltaje total será el resultado de la suma de voltajes de baterías conectadas.

La intensidad final será la misma de cada pila.

Ejemplo:

Tres baterías de 3V  y  2000 mA en serie darán un potencial de 9 V y una intensidad de 2000 mA.

 

Si están en paralelo, darán un potencial de 3 V, pero la intensidad será de 6000mA. 

[Toastie]

22 minutes ago, DrJB said:

Glad we reached consensus. Cheers.

That is the best part of it! Cheers!!!

(Oh - then my second brick career started 1997. It was a DUPLO ambulance for my daughter - but when browsing the shelves I was simply taken away ... far far away. And then came Mindstorms RIS. It hit me hard 1998 at Target in the US (me and my family lived there for some years) - and that was it: No life without LEGO anymore. It was a very good experience and decision. My first set was 323 ...

Did remove the funny lines.

All the best!
Thorsten 

@Jesete

Sorry I can't reply in Spanish - but my goodness, Google translator has pretty much improved.

So yes: What you are saying is what I am saying. I believe

Best
Thorsten