MOD: PF battery box with 2x 9V Block

[MarkusOSX]

Hi there,

today i want present you my last MOD.

I wanted to use rechargeable batteries for my LEGO Technics.

The standard rechargeable AAs don´t have enough power (6 x 1,2V = 7,2V), so i modificated the standart PF battery box for 2 x 9V blocks.

The other thing is the weight.

With 6x AA = 208,4g and with 2x 9V = 132g)

The 2x 9V are connected parallel so the voltage stays 9V.

Here are the pics for my little mod.

First removed all battery connectors

Then need to cutout.

First test for fitting.

Placed the new clips vor the 9V blocks and clued in.

Solder the new cables to the board (parallel)

Yes, it´s just as easy to remove the blocks like the standard AAs.

Weight with 2x 9V blocks = 132g

Weight with 6x AA = 208,4g

So I´m able now to use rechargeable batteries and get full voltage of 9V with less of weight.

Greetz

Markus

Edited January 2, 2013 by MarkusOSX

[hrontos]

Nice MOD.

I have some worries that the capacity and also maximum current provided by 9V rechargeables is smaller that the one provided by AA.

Did you made also some test to check if you can get enough current from those 9V batteries? I have never seen a device (toy) with a motor powered by this type of 9V battery. They are usually used in remote controlers or other types of devices which are not so "hungry". Motor needs higher current rate and therefore use packs of AA, C or D size batteries.

[MarkusOSX]

I can´t tell you atm. I need to test it.

[clarkdef]

Nice MOD.

I have some worries that the capacity and also maximum current provided by 9V rechargeables is smaller that the one provided by AA.

Did you made also some test to check if you can get enough current from those 9V batteries? I have never seen a device (toy) with a motor powered by this type of 9V battery. They are usually used in remote controlers or other types of devices which are not so "hungry". Motor needs higher current rate and therefore use packs of AA, C or D size batteries.

.1 to .2 amps which usually can be drawn from them, so with parellel wiring you could achieve maybe .4 amps depending on the battery I think. They could be able to deliver more amps they never state it on the darn batteries.

This is a bit low for high output motors, can you fit two more in there?

[Boxerlego]

A regular akaline 9volt battery 500 mah is nothing in power what you need is lithiuim 9 volt 1200mah power Check out this Nine volt data sheet here http://en.wikipedia...._specifications

Edited January 2, 2013 by Boxerlego

[hrontos]

A regular akaline 9volt battery 500 mah is nothing in power what you need is lithiuim 9 volt 1200mah power Check out this Nine volt data sheet here http://en.wikipedia...._specifications

In the same table it can be seen that rechargeable version is far beyond that and is again only 7.2V since it consists of 6 1.25 V cells just like AA box.

[clarkdef]

A regular akaline 9volt battery 500 mah is nothing in power what you need is lithiuim 9 volt 1200mah power Check out this Nine volt data sheet here http://en.wikipedia...._specifications

Yeah but he wants rechargable batteries and according to this chart they don't quite meassure upto 9v, around 7.2v and at 0.120 amps over the hour they sit at 1.8watts far to low an output

[Hopey]

I put 8 rechargeable AAAs in mine, to get 9.6V. I haven't done any empirical testing but it works pretty well for me. How would this compare in terms of capacity?

[1974]

Be carefull about putting batteries _in parallel_! Especially with LIPOs (and when charging!). Most types requires balancing resistors and / or more advanced circuitry. Serial is fine, parallel is another bag of (not)fun

So, who's gonna be the first to blow up an XL with this new fad?

Yes, there is pretection circutry build into TLG's electrical parts, but what good is it if you trip it all the time?

I'd like to see some proper load

LEGO is not high perfomance RC, don't treat it like that .. imho that is

[hrontos]

I put 8 rechargeable AAAs in mine, to get 9.6V. I haven't done any empirical testing but it works pretty well for me. How would this compare in terms of capacity?

AAA have something like 650-1200mAh, AA can have easily 2700mAh. This means not only that they last twice as long but it also means, that peak current is higher. From this point of view, even best non-rechargeable 9V is not better than AAAs. But two non-rechargeable 9V can be interesting (because the have lower weight), if they really have 1200mAh each.

[1974]

Yes, 9V batteries are quite poor when it comes to mAh.They also have high internal resistance, which means that they are poor at heavy peak loads. AA are better than AAA .. and C are better than both .. and D are the best. Then you need to step up to LIPO

Regular 12V lead/acid types can also give _really_ high amps and are quite forgiving when it comes to charging

I doubt you can find 9V batteries that really have a 1200mAh capacity. That's like a factor three to five higher than normal

Edit: (m)AH is a function of volume, keep that in mind when you're comparing various types

Edited January 2, 2013 by 1974

[hrontos]

This insufficient power can be a problem for all purpose applications, but for situations when you need a lighter battery box it can be quite usefull.

[Boxerlego]

This insufficient power can be a problem for all purpose applications, but for situations when you need a lighter battery box it can be quite usefull.

Lego could have the possibility to fit 4 9v batteries inside the battery box.That is a whopping total of 4800mah with the lithium. I usually try to power my servo motor separate from my drive motors. I do this with a nine volt battery and a moc PF wire.

[1974]

LEGO is not real RC. Even if you could get that kinda of battery power, the rest; axles, lack of ballbearings, weak ABS, poor tyres not to mention motors/servos etc is gonna be a shopstopper. Honestly, if you wanna do this, look at Tamiya etc

LEGO is cool for intricate mechanical works like the 8043 Excavator/pneumatics like the 8110

I feel a lot of posters here are barking up the wrong tree

[hrontos]

LEGO is not real RC. Even if you could get that kinda of battery power, the rest; axles, lack of ballbearings, weak ABS, poor tyres not to mention motors/servos etc is gonna be a shopstopper. Honestly, if you wanna do this, look at Tamiya etc

LEGO is cool for intricate mechanical works like the 8043 Excavator/pneumatics like the 8110

I feel a lot of posters here are barking up the wrong tree

For me it does not make sense to create something that can go fast from LEGO, but compact high capacity BB can be interesting for creations that require more motors to be operated in parallel.

[Boxerlego]

LEGO is not real RC. Even if you could get that kinda of battery power, the rest; axles, lack of ballbearings, weak ABS, poor tyres not to mention motors/servos etc is gonna be a shopstopper. Honestly, if you wanna do this, look at Tamiya etc

LEGO is cool for intricate mechanical works like the 8043 Excavator/pneumatics like the 8110

I feel a lot of posters here are barking up the wrong tree

LEGO is not RC. RC wishes it was LEGO. You break a RC things will get complicated real quick. All the RC parts out there are RC parts nothing more or less. With LEGO it is not that simple. It is all about how you want to build. some go easy some take it to far. Some people want to build as high as they can others want to reach new speeds.

A 4800mah 9 volt battery box would be as good as using two 8881 battery boxes. In my opinion, destroying the battery box for a better battery supply is the not the path to go down.

Edited January 3, 2013 by Boxerlego

[Mechbuilds]

If i go trough and make this mod on my battery box, how will it differ from using the 6 AA batteries? 
Will run time increase?
Will power increase?


And sorry for the threadnomancy. 

[coinoperator]

On 1/2/2013 at 9:42 PM, hrontos said:

enough current

If you use Li-Ion batteries you will get an almost zero internal resistance = Ludracous current.
Adding a fuse would be a good idea if Li-Ion is used.

Don't believe me?
Try to short a Li-Ion battery... WEAR SAFETY GLASSES.

[sirslayer]

Lets use buckets of water as analogy for 9 volts battery.    the 9 volt battery equals to 9 gallons of water in a bucket in analogy mode.  but the hole in the bottom of the bucket is small so only a few drips of water comes out..  well a 9 volt battery does that .. only small amount of current can be gain like the drip from a small hole in a bucket.. the drip can maybe push a watermill but it doesn't  ok say you have 9 volts but in 1.5 gallons so you have 6 buckets  but these buckets can pour the whole amount of water quick and it can turn a watermill but the problem is that the buckets run empty to quick but that is needed to turn the watermill (lego motors) so therefore 6 x 1.5 volts  batteries can drive 2 Large motors for an hour where the one 9 volt battery is only design to run 1 lego M motor for a bit.. so current (amps) is how much of the voltage is leaking(discharge) till it runs dry 0 volts. Lipo  batteries s like having AA batteries that can dump alot of current and does it for an hour (mah) and can be recharged!!!   Its that easy and you can even use ohm's law!!!   

Edited February 26, 2019 by sirslayer

[Mechbuilds]

So you're saying that using two 9 volt batteries is a bad idea and to use a lipo instead? 
Cause i was ready to do the same mod that OP made. 
So basically using two 9 volt batteries wont last as long as 6 AA batteries and the 6 AA batteries can give more power too? 


All i want is just a longer lasting battery life with the standard 9 volt power. 
But i want that longer lasting battery life in this specific battery box because it fits my moc aesthetically and being rechargeable would be a plus. 

Edited February 26, 2019 by Mechbuilds

[sirslayer]

yes the 6 AA disposable batteries have more amps .therefore better performance then lego lipo. thats why I use AA duracells...power is know as watts and that how much heat it generates . because the 9 volts batteries are design to last for years due to its low current.. so there is a trade off 

Edited February 26, 2019 by sirslayer

[Mechbuilds]

Just now, sirslayer said:

yes the 6 AA disposable batteries have more amps .therefore better performance then lego lipo....power is know as watts and that how much heat it generates . because the 9 volts batteries are design to last for years due to its low current.. so there is a trade off 

What lipo should i go for that fits inside the battery box? 

[sirslayer]

if you seen my thread , 12 volts lipo is king but 11.1v is safe for lego PF devices 

Edited February 26, 2019 by sirslayer

[Mechbuilds]

Just now, sirslayer said:

if you seen my thread , 12 volts lipo is king but 11.1v is safe for lego PF devices 

How about modifying it for these?
ZNTER S19 9V 400mAh USB Rechargeable 9V Lipo Battery

[sirslayer]

400 mah is poor....  at least 1000!! for 2 Large lego motors  to run in a hour 

Edited February 26, 2019 by sirslayer