Quick question on battery boxes

[Paknaloid]

Sorry if this has been answered elsewhere (I couldn't see that it had) - does the rechargeable battery box (84599) have exactly the same size dimensions as the non-rechargeable version (88000)?  I don't care at all about performance, I'm looking to follow someone else's MOC instructions which call for 84599, but as 88000 is so much cheaper I'd like to use it instead if the sizes are identical and so swapping wouldn't affect the build.

Thanks for your help.

[Maaboo the Witch]

2 minutes ago, Paknaloid said:

Sorry if this has been answered elsewhere (I couldn't see that it had) - does the rechargeable battery box (84599) have exactly the same size dimensions as the non-rechargeable version (88000)?  I don't care at all about performance, I'm looking to follow someone else's MOC instructions which call for 84599, but as 88000 is so much cheaper I'd like to use it instead if the sizes are identical and so swapping wouldn't affect the build.

Thanks for your help.

Depth wise they're different, but I wouldn't know about width or length.

[mahjqa]

Size is identical. I recommend you get the rechargeable one anyway.

[Maaboo the Witch]

Oh! Sorry, thought we were talking about the AA box and the rechargeable one. I'll just plug my brain in and go away. 

[Paknaloid]

Thanks, both - I can't justify the £70-£80 for a rechargeable one on BL (or even £50-£60 on eBay), so will take the hit on performance and go for the bog-standard version for a tenner.  I don't envision using it a huge amount anyway - a play now and again, but the MOC is going to be for display 80% of the time.

[Jon61]

More information on PF elements is available at the following link. It confirms that 8878 (the 'set' number for the rechargeable box) and 88000 the AAA box, are the same size. You may want to bear in mind though that the AAA battery box does not have the variable power control, and you will need to be able to access it sufficiently to remove the batteries for recharging, whereas as long as you can get a plug into the socket on 8878 you can recharge it in situ.

https://www.lego.com/en-gb/powerfunctions/articles

[Aleh]

52 minutes ago, Paknaloid said:

Sorry if this has been answered elsewhere (I couldn't see that it had) - does the rechargeable battery box (84599) have exactly the same size dimensions as the non-rechargeable version (88000)?  I don't care at all about performance, I'm looking to follow someone else's MOC instructions which call for 84599, but as 88000 is so much cheaper I'd like to use it instead if the sizes are identical and so swapping wouldn't affect the build.

Thanks for your help.

I always use non-rechargeable instead of rechargeable, because I do not own the last one.

23 minutes ago, Paknaloid said:

Thanks, both - I can't justify the £70-£80 for a rechargeable one on BL (or even £50-£60 on eBay), so will take the hit on performance and go for the bog-standard version for a tenner.  I don't envision using it a huge amount anyway - a play now and again, but the MOC is going to be for display 80% of the time.

Better to buy BuWizz v.2.0 as I understand.

[Alex Ilea]

Why do I feel you are building the Aston Martin by Jeroen Ottens ?? 

[Paknaloid]

Nope - although I'd love to someday!  I'm actually looking at Jurgen Krooshoop's Ultimate 8043.  Of course, I need to pick up a second-hand 8043 first....

After operating some real-life excavators at Diggerland UK, I caught the excavator bug and really want to build a remote control one that's capable of actually excavating.

Edited July 19, 2018 by Paknaloid

[Leif]

The rechargeable has an end of life after a certain amount of recharges. After that it’s not even a paper weight..

Take that into account before your purchase!

[mahjqa]

50 minutes ago, Leif said:

The rechargeable has an end of life after a certain amount of recharges. After that it’s not even a paper weight..

Take that into account before your purchase!

Been using mine ever since they came out. No signs of degrading yet. And I use them plenty.

[Johnny1360]

I realize you don't get as much power with rechargeable batteries, in the regular battery box as with normal ones but that is what I use. Does the LEGO rechargeable battery box make up for this difference? 

[Toastie]

2 hours ago, mahjqa said:

Been using mine ever since they came out. No signs of degrading yet. And I use them plenty.

Fully agreed … these are Lipos and no bad ones either.

And should the cells degrade in a couple of decades: Open the box, get new cells (they are dead cheap, solder them on an off you go. It is the loading and safety electronics, that I find most powerful in this device.

Best
Thorsten

 

Edited July 19, 2018 by Toastie

[bonox]

@johnny1360 no - the chemistry of the batteries is pretty much the same.

 

They're approximately 7.4 volts and not 9v nominal. It comes from 6 times 1.2volts for NiMH chemistry (most rechargables) and two times 3.7volts for the lego 84599 lithium pack. The current limit is the same because it's limited by the battery box and lower than the theoretical output of the cells, and power is the product of voltage and current. Brushed DC motors output power is based proportionally on input voltage, so a 9V non rechargable set of batteries will have a higher 'power' potential than rechargables.

Keep in mind that power is quite different from energy and it's energy that leads to running time.

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

Edited July 19, 2018 by bonox

[Toastie]

5 minutes ago, bonox said:

no - the chemistry of the batteries is pretty much the same (or is if you're using

They're 7.4 volts and not 9v nominal. The current limit is the same and power is the product of voltage and current. Brushed DC motors output power is based proportionally on input voltage, so a 9V non rechargable set of batteries will have a higher 'power' potential than rechargables.

Keep in mind that power is quite different from energy and it's energy that leads to running time. 

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

Well.

I guess we need to study Philo's page very carefully. There are ample of differences: Low vs high current drawing, sudden vs continuous cell stress and so on. And yes, power is voltage times current. And then we need to follow the curves and measurement scenarios very carefully and use the integrals below these curves.

The chemistry involved however could not be more different than between a LiPo and any kind of one-way battery.

Ane lastly: There is maybe another balance we should take into consideration: Having more power for a short time for fun and then dispose a small chemical reactor - or having slightly less power for some short time - and then recharge again. The trash can may be - hopefully - a green chemistry bin; but the amount of energy and resources to make a new one-way battery even from carefully recycled material is - at best - discouraging.   

Another thought: You can run the LiPo's off from a power supply powering your model during testing - endlessly - use any kind of wall wart you can find, supplying decent DC in the 9 … 20 V range, and then unplug and let the dogs out

All the best,
Thorsten

  

[bonox]

I noted it in my post that you didn't quote, but the chemistry isn't the same as far as molecular level, however electrically, the chemistry is pretty much identical. - both rechargable battery types produce 7.2-7.4 volts (even though one uses six cells and the other two). Significantly below the 9.0+volts you get from a non rechargable set.

The integral under the discharge curve is an energy summation, not a power output, which is not what was asked in the question I responded to. In these simple DV motors, power output is just voltage times current. From the 250mA and 750mA discharge curves, the Lego rechargable pack is a long way behind the multiple AA NiMH batteries he samples so my first word is quite simply the answer to the question. "No", the lego LiPo pack does not "make up for the difference", which it could potentially do with a buck converter or similar to keep the output at 9.0 volts regardless of the battery voltage.

The longer question you've alluded to is the power advantage of the non rechargable cell type Philo tested doesn't last for very long; once you get over the initial load time and the alkaline voltage sags (the first 250mAh energy drop) the effective power output of the rechargables is higher than the non rechargables assuming both can maintain the same current output.

[Johnny1360]

1 hour ago, bonox said:

 the Lego rechargable pack is a long way behind the multiple AA NiMH batteries he samples so my first word is quite simply the answer to the question. "No", the lego LiPo pack does not "make up for the difference", which it could potentially do with a buck converter or similar to keep the output at 9.0 volts regardless of the battery voltage.

 

Thanks that's the answer I was looking for, so for now I will just stick with the regular box with rechargeable batteries, since I already have a boat load for my bicycle lights, if I need a little more power I usually stick in some fresh alkaline batteries. No need for me to shell out the bucks for the LEGO rechargeable box, at this time, to many sets I want instead. 

Also thinking about Power Up and new options that it might include, I would rather invest in the future. Basically still in my infancy, set wise, since coming out of my dark age less than 3 years ago. 

Sorry for the Thread Jack, just seemed like a good time to find out about something I always wondered about, without starting a new topic. Glad my thinking was correct for a change.

Edited July 20, 2018 by Johnny1360
Added some stuff