About 8878

[itoero]

Why should I use the 8878 and why not?

It's lighter so why isn't it used more often?

[agrof]

In case it is not clear for some (like me), the question is about the battery boxes:

The answer to be find more in the batteries AA vs AAA, and the key is, that AA batteries deliver much more energy - last longer in LEGO models.

Detailed: http://www.allaboutbatteries.com/Energy-tables.html

 

[DrJB]

That's exactly it. The AA batteries are larger, and as such, will last longer. Now, there is a version similar to the 8878 that is rechargeable. It is mostly useful in situations where it's difficult to remove the battery pack.

[itoero]

ah ok, thx for the link.. They basically  store more energy because they are bigger.

How much mA gives the 8788?

[PKW]

3 hours ago, itoero said:

ah ok, thx for the link.. They basically  store more energy because they are bigger.

How much mA gives the 8788?

All lego battery boxes has a protection that limit the output to 750mah (but on bursts it may go higher)

Edited April 11, 2017 by PKW
Typo 250 ->750

[Limga]

Every reply here is totally wrong.

First of all, 8878 - is rechargeable Li-Po Battery box. Nominal voltage - 7.4V. Maximum (after charging) ~8.3V. 
AAA box is 88000. And AA battery box is 8881.

8878 is lighter and gives current without lose while discharging. AA and AAA usual batteries give maximum current only for the first few minute.
The reason that 8878 is not used often is the price.

All LEGO battery boxes have a similar protection (except the newer AA boxes, that don't have protection) that can give guaranteed maximum of 750mA. (mAh is the capacity, mA - current). In fact they can give 1A for a long time period. And up to 3A for only a second. It is the protection. Maximum current depends on used batteries. More information about LEGO Battery Boxes and testing is here: http://philohome.com/batteries/bat.htm

[DrJB]

8 minutes ago, Limga said:

Every reply here is totally wrong.

Really? ... Read again пожалуйста

[Blakbird]

@Limga is entirely correct.  8878 is a rechargeable battery box.  The primary advantage is that it is rechargeable.  It is the best box overall, but also costs the most.  If you go through a lot of batteries, it will save you money in the long run.  Every box is capable of higher current based on the batteries, but is limited so the difference doesn't actually matter.  The AAA box has by far the lowest capacity.

[itoero]

Thanks for the explanation Limga

[Limga]

34 minutes ago, DrJB said:

Really? ... Read again пожалуйста

I know English word "please". So you don't need to refer to Russian translation. And it seems quite offensive.
OK, let's read again.

2 hours ago, DrJB said:

That's exactly it. The AA batteries are larger, and as such, will last longer.

That parts is right, I agree. Seems that I shouldn't have written "totally wrong".

2 hours ago, DrJB said:

Now, there is a version similar to the 8878 that is rechargeable. It is mostly useful in situations where it's difficult to remove the battery pack.

Nope. As I said the 8878 is the rechargeable one. The AAA box similar to 8878 in dimensions is 88000.
I won't buy an expensive Li-Po battery only because sometimes it is difficult to remove battery pack. The main features for me - recharge ability and non-decreasing current. But for someone the possibility to charge it without disassembling may be critical, I agree.
OK, not totally, but still partially incorrect and not full answer that can mislead.  

Edited April 11, 2017 by Limga
spelling

[Jon61]

In addition to the points made above by Limga and Blakbird about the cost of the 8878 rechargeable box (UK£43), there is also the outrageous price that Lego charge for the official transformer required to recharge it (an extra UK£25). It's reasonable enough not to include the transformer with the rechargeable pack itself as some people may want more than one pack but only need one charger, but most people (like me) think the transformer is massively over-priced (even by TLC standards )

[PKW]

1 hour ago, Limga said:

I won't buy an expensive Li-Po battery only because sometimes it is difficult to remove battery pack. The main features for me - recharge ability and non-decreasing current. But for someone the possibility to charge it without disassembling may be critical, I agree.
OK, not totally, but still partially incorrect and not full answer that can mislead.  

For those doesn't understand what is the advantage of not loosing current instead of aiming for more capacity of standard batteries(longer running time) it is pretty simple:

 

Lipo batteries (as 8878) have got a nominal voltage of 7.4V (6 alkaline ones heve got 9 and nimh, so standard rechargeable 7.2) but this voltage, that theld be roughly represented by motor speed and led brightness, doesn' fell of to the "discharged" state linearly (ex when you have 3.7V you have half of the battery "capacity") but instead it remains more or less 7.4V until it suddenly drop to a lower voltage ad you need to recharge the  BB.

Alkaline/normal rechargeable batteries has got a really different vbehaviour while discharging and in fact you have a good voltage only the first few minutes and then the battery "power" start slowly dropoff until the end.

Just to give an example, if we make a race (untill battery dead) with two clone cars that differ only in the BB, the standard battery one will slowly loose speed, the lipo one will have more or less the same speed until it dies (but maybe win the race).

 

But (second example) if we need to run a gbc module  not worrying to much about balls per minute but that need to run for a whole day, then the standard batteries will be better

[Saberwing40k]

If I recall correctly, 8878 puts out somewhat more current than the 88000, which is why it is used. Basically, 8878 is smaller and lighter than the AA box,while still outputting high enough current levels. And it discharges differently. Me, I stick with me Eneloop batteries.

[DrJB]

7 hours ago, Limga said:

Every reply here is totally wrong.

... Seems that I shouldn't have written "totally wrong".

Thank you. That's exactly my point. We should abstain from making 'blanket' statements.

As to me using a Russian word, I was not being 'offensive'. I was being 'playful' ... just to make sure you do not miss it. If that offended you, then ... Я извиняюсь ;)

Now, back to batteries: All batteries of a given nominal voltage deliver that voltage (there are variations depending on the chemistry inside). However, a larger battery (AA) will deliver more 'juice' i.e., last longer than a smaller one (AAA). I thought this was the main point being discussed. If that's not it, then ok I misunderstood, let's move on. I was however not being careful with terminology (8878 vs 88000).

Edited April 12, 2017 by DrJB

[TechnicRCRacer]

I don't wanna take part in this argument, but I have a question too. Is the 8878 powerful enough to run a single buggy motor via V2 receiver?

[Saberwing40k]

Yes, if I recall, Sariel does this with at least a couple of his creations.

[PKW]

4 hours ago, TechnicRCRacer said:

I don't wanna take part in this argument, but I have a question too. Is the 8878 powerful enough to run a single buggy motor via V2 receiver?

Every battery box can run it if it has no load, but also all BB will have their protection limiting the current if you load too much the motor (for example by using the motor to power some high friction mechanism of to move a lot of weight)

[agrof]

In different perspective, raising a question properly (with better description, link, or pictures) will not lead to misunderstandings. I admit, I just googled quickly, and as I saw the rectangular battery box, I associated immadiately to the AAA box. What elso could have it be, as the rechargable (+ the charger) are expensive like hell and thus not comparible with the big BB in terms of sales. 

Still I don't mind how it turned out, at least we got a nice overview about the official energy store systems.

My bad, I was tottally wrong by accident, I pull back myself in a dark corner, and start to reapprisal my life. 

 

Edited April 12, 2017 by agrof

[DrJB]

Don't be too hard on yourself. We all make/made mistakes, especially those of us with lots of experience. This forum, to me, is about learning and sharing and I hope we achieved that, even though some feathers got ruffled.

[1gor]

 

15 hours ago, DrJB said:

That's exactly it. The AA batteries are larger, and as such, will last longer. Now, there is a version similar to the 8878 that is rechargeable. It is mostly useful in situations where it's difficult to remove the battery pack.

...and it is smaller and lighter  (look under weight) so you can make more balanced model with this battery box if battery box can not be centered on your MOC.

When you add rechargeable batteries to other battery boxes you gain weight (a huge amount - which currently is giving me a headache on my currently running project). I know that it is not polite to make advertising job for someone else, but please read Pavel's report about battery boxes, so you can get most answers there. 

[DrJB]

I think this topic is over now. Most of us think of Lego as a hobby, not to become experts on batteries. The main questions have been answered, though I'm sure some audience members will find your post/link useful.

True, the AA batteries are also heavier than the AAA ... but in the end, everything we build is a set of compromises. I understand that some of us True/Seasoned (older/experienced) engineers are after achieving stretched 'optimizations' ... looks vs. function vs. dynamics vs. durability vs. long lasting batteries vs. weight distribution vs. tire rolling resistance vs. cost ... you get my point.