Current limit on old 9V battery boxes

[TechnicSummse]

Hello :)

Anyone of you got some imformations about the current limitation of the old 9V battery boxes 4760c01 ?

[img=]

I dont have one yet... but from some pictures i saw, it seem to have the same heat-protection-element then the 2847c01.

How many amps does it supply, without kicking in the protection?

 

Thanks for help :)

 

Summse

 

Edited June 18, 2017 by TechnicSummse

[dr_spock]

It seems like they all use the same 750 mA resetable fuse.

http://www.philohome.com/batteries/bat.htm

 

[TechnicSummse]

The 750mA there are on PF-elements... but im am asking for the OLD 9V battery-box 4760c01

[syclone]

There is no circuit. it is just ON / OFF , nothing else. I've dissasembled one because it was second hand and got some corrosion , and there are simply some metal parts bending when you press the button and nothing regarding protection. 

Nevermind, it looks like it has some , but can't tell what it is , will post a photo, in case someone knows about electronics...

It is a weird circle between the contacts, it seems to be multi-layered. Sorry for picture quality, tomorrow better photos.

look at the left wall , between metal parts:

Edited June 18, 2017 by LXF
added images

[bonox]

based on what the manufacturers suggest, I doubt you'll get much more than 0.75A out of those tiny batteries anyway. 

http://data.energizer.com/pdfs/522.pdf

http://data.energizer.com/pdfs/la522.pdf

the lithium one shows a capacity value using a 1A draw, but if you're pulling that kind of current you won't be playing for very long.

[aeh5040]

Indeed, in my experience these 9V batteries themselves are not suitable for high-current applications.  I once tried running a buggy motor powering a pneumatic compressor from one - I seem to remember the battery was dead in a minute or so!

[mocbuild101]

5 hours ago, LXF said:

a weird circle between the contacts, it seems to be multi-layered.

That is the current limiter, it's the same as the one in 2847c01.

[IstakaCiti]

4 hours ago, aeh5040 said:

Indeed, in my experience these 9V batteries themselves are not suitable for high-current applications.  I once tried running a buggy motor powering a pneumatic compressor from one - I seem to remember the battery was dead in a minute or so!

Yes, driving a motor from 9V battery will drain it quite fast.

Somehow, technology has ignored 9V batteries, they are still the same as they were decades ago. 

[Marxpek]

Hey @TechnicSummse welcome here ;)

this box has one of the worst thermal protectors around (kicks in very fast), this has a older version of the thermal protection, a plate that bends when hot, breaking contact.

Since i already know what you want to do here: i will say it again, buggy motors can ONLY be powered fully by the rc-unit, nothing else can bring out their full potential (unless you cheat with the thermal protectors) not even the battery boxes that came with the buggy motor expansion pack or the yellow batterybox (like on 8421) can handle the current needed.

Besides that: 9 volt batteries that can deliver that kind of current are rare, since they are moslty made for low power consumption.

[TechnicSummse]

Thank you for tthe answers so far. Does anyone have any hard facts?

I would like to see like: "it can support 200mA for 5 min, then it kicks in". If I understand you correctly, this old protection depends on time+current?

 

So, you could take for example unlimited time (until battery is empty) like 100mA, because the protection element cools down faster, then it heats up at this current.

But if you take for example 1000mA it would kick in within less then a second? And if taken 500mA it will last for like 1 minute? 

Do I understand this in the right manner?

 

If so.... are there any values you could deliver to me? ... like time*current=xxx

 

Again thank you for the help.

 

@Marxpek

Well i need fresh ideas... and i like to think outside the box ;)

[Philo]

42 minutes ago, TechnicSummse said:

Thank you for tthe answers so far. Does anyone have any hard facts?

I would like to see like: "it can support 200mA for 5 min, then it kicks in". If I understand you correctly, this old protection depends on time+current?

No, it's very hard to tell... These devices are thermal protections, whose resistance value increases rapidly with temperature. So exact time to trip depends on current, but also initial temperature and on device itself (they have fairly loose tolerances). To get a better idea, look at the trip time curve of the component. For example, this is the datasheet of the resettable fuse in PF devices http://www.bourns.com/docs/Product-Datasheets/mfr.pdf?sfvrsn=24, curve is on page 4. Note that exact model of older battery packs is not known (no marking on the component).

[Marxpek]

41 minutes ago, TechnicSummse said:

But if you take for example 1000mA it would kick in within less then a second? And if taken 500mA it will last for like 1 minute?

this is not how a thermistor works, it has a certain setting, lets say a 1 amp thermistor will pass through any current up to 1 amp, if you go over that it will kick in within a second or so, but if you pass 500mA it will never kick in, a thermistor should always kick in within a few seconds of overload to prevent melting wires and shorting/burning wires. 

The previous best (tested) batterybox can pass 800mA, will trip the thermistor within a few seconds when attaching a buggy motor with some load, there are small differences in the thermistors production making some go to 900 mA and others to 700mA.

The newer AA batterybox with the brighter green led, has a higher setting then 800mA, but this has not been tested for exact data yet (as far as i know), but from my own experience: one new batterybox can still not fully power a buggy motor, there are reasons the buggy motor was discontinued, this is one..

[syclone]

Hop[efully these will be useful. As far as I can see the protection can be removed without soldering. (click to enlarge photos)

IMG_8715 by Alaxaf, on Flickr

IMG_8717 by Alaxaf, on Flickr

IMG_8714 by Alaxaf, on Flickr

Do I have NASA's 9v batteries or something?

Edited June 19, 2017 by LXF

[Marxpek]

18 minutes ago, LXF said:

Do I have NASA's 9v batteries or something?

What is the discharge rate on these? they say "high drain" but how high is that? Compared to a normal 9V battery anything over 200mA discharge I consider highh, but a 1000mA is not nearly high enough for a buggy motor.

But when i look at the "normal charging time" on the battery that is pretty slow, and this normally correlates to the discharge rates. does it give a fast charging time for it and a C-rating? can it trip a thermal resistor when stalling a motor?

Of course you are still only getting 8.4 volts from them, lowering the speed on the motor and also lowering the current being drawn.

@LXF and somewhere you are being scammed with the info they provide, there is no way in hell this battery can contain 2000Mah @ 8.4v, most (trusted) battery brands have a value of 150mah up to a maximum of 500mah, my guess is they did some fancy numberwork here and you actually have a 285mAh battery at 8.4v. They went creative with numbers and most likely did something like this: 7 cells @ 1.2v each with 285mah = (7x285mah) 2000mah..

Did you ever do some measurements on these? it is highly unlikely that they will contain the same energy as a battery box filled with rechargeable AA batteries of the same quality..it is just a size thing..

[Marxpek]

@TechnicSummse and of course removing thermistors is cheating, but i still do not believe 9v batteries can power a buggy motor..

[syclone]

12 minutes ago, Marxpek said:

@TechnicSummse and of course removing thermistors is cheating, but i still do not believe 9v batteries can power a buggy motor..

I have no idea about discharge rate of these, but I'll build a MOC with them for test. For now, I tried stalling the fast output of a buggy motor withoput success, it just kept slowly rotating  The only thing I accomplished is to burn myself ...

Edited June 19, 2017 by LXF

[LegoTT]

Removing the thermistor is cheating, however blocking it with a bush is still 100% LEGO...

According Philo the 5292 motor can handle 3.2 A so if a 9V battery can discharge 0.2 A we can sum up 16 9V battery with various cables to prevent heating and go for a 60 secondes round of incredible mechanical power.

Which is nice, for a lightweight TT in a small race.

 

Despite the running time, the subjet is interresting for me !

 

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English is not my native language

[Marxpek]

4 minutes ago, LXF said:

I tried stalling the fast output of a buggy motor withoput success, it just kept slowly rotating  

It doesn't not need a lot of current to burn your fingers ;) can you attach a wheel or something to the output? when you can trip the thermistor inside the buggy motor that would mean the battery delivers enough power. (but you will need a shunted box, but since you suggested it, you probably have one)

Just now, LegoTT said:

16 9V battery with various cables

 

Just now, LegoTT said:

lightweight TT

These 2 do not really combine ;D 

[LegoTT]

I have in mind this category of builds (from Paave), with the maximum of work on the mechanical power/weight ratio, regardless the autonomy.

I can imagine quick stop like in F1 races to switch battery and beat the chrono.

 

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English is not my native language

Edited June 19, 2017 by LegoTT
wrong link

[Marxpek]

10 minutes ago, LegoTT said:

 

Removing the thermistor is cheating, however blocking it with a bush is still 100% LEGO...

 

This is creative, but but I do not agree, you are placing a part somewhere that was never intended to have any parts, even worse, you are blocking a safety measure, especially designed for that purpose, so i do not consider that 100% Lego (solutions), since TLG will never approve this.

[syclone]

@Marxpek Just did it, put some lights on the battery box for proof , uploading video. Yes , I cheated the protection already 

Sorry for sound, but my phone's microphone doesn't work

Edited June 19, 2017 by LXF

[LegoTT]

I think I can understand your point of view, people use cheap pneumatic hoses, Sbrick, Buwizz or RC tires with fantastic results but we can't really argue if it's still LEGO because the limit is different for each person.

I cant tell for other but mine is there : you can replace or repair a lego part to the same, you can misuse a lego piece if it is not destroyed.

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English is not my native language

[Marxpek]

@LXF I oversaw something here... your battery is protected itself... it has probably the same protection built it... and that might kick in here and still provide enough power for the lights, still not prooving anything, all those damn safety-precautions ;D

maybe attach a other motor which you do not stall in stead of the lights? that should draw alot more power then the lights (as far as i know the thermistor never really full breaks the circuit just raises the resistance a lot, but correct me if im wrong)

Edited June 19, 2017 by Marxpek

[LegoTT]

Just now, LXF said:

I cheated the protection already

I'm very interested by these tests.

How soft are the wires now ? If they are, maybe it is a good idea to add some another wire.

Does the 9V battery is very hot ?

Do you smell a scent when you open the BB ?

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English is not my native language

[Marxpek]

@LegoTT Don't forget the motors are protected for overheating as well, in theory this should not be able to melt any wires or do any damage (until you connect something wrong) the RC unit delivers this (and more) power over the same wire without problem.

But by these rules of using a bush to block the old thermal resistors, you could also bypass the thermistor in a new battery box by twisting up the legs and put a Lego rubber band on it (or something similar) and then say: it is 100% Lego. to me it is all cheating, fine to do it for a private moc or something. but not in contests or in my case: speed records.