Giottist

Rechargeable batteries for powered up hubs

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Hey Capparezza, Thanks a lot for your info! You're using so called LSD cells (Low Self Discharging, means new technology).

If we collect all available information we can do a lot for the LEGO train community :classic:

 

PS.: Just found technical information about the Technoline BC700 charger. It charges and supervise each cell individually. And the eneloop cells are new generation LSD cells. This explains your sucess! Let everybody know this, if Li-Ion technology seems suspicious ...

Edited by Giottist

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16 minutes ago, Giottist said:

This explains your sucess! Let everybody know this, if Li-Ion technology seems suspicious ...

Hi @Giottist,

Li-Ion - and particular Li Polymer technology is not anywhere close to being suspicious - none what so ever. In contrast. Every single cell phone runs on these. And there are billions of these devices out there. Teslas run on them. The LEGO Li-Po rechargeable battery is a fantastic in-house solution, but really expensive. I have had a go at the LEGO Li-Po. I leave it up to you, but it does not get any better. As of today there is simply no currently broadly available technology out there that is better than Li-Ion or Li-Po; >at an affordable price<. That is the thing, and these are two different worlds (or even three, when we count in TLG):

World 3: "TLG" - is a (German)-pharmacy-type-company: They charge really high prices - >always<. Regardless of what you buy there. Paper towels for example. I know that the manufacturing of ABS bricks with zero tolerance in dimensions is expensive. Ask @coaster - he is doing an incredible work in this regard. But man, TLG charges insane amount for a) the 10V DC story, which is a (bad) joke and b) people willing to pay $ 25 for a <$1 wall wart power supply from China (I bet this is where TLG is getting their "10 V" thingies).

World 2: "What can we afford - and who is selling what - at what price". Eneloops. Sure! But you know, I got my NiMHs from ALDI Nord. €3 for four of them. I trust ALDI because they a) can't afford to f*ck up - because that is simply not their way. And b) they go cheap. My charger is - guess - from that "company" as well. I do also get my vegetable juice, wine, and what not there. And always wonder their shelves to find the "other" things they have. Reading very very very carefully what the wrapping says - decide to buy or not.

World 1: "What is principally possible". Where are the limits of technology. Look at "military type batteries" on the web. There are incredible batteries out there. With enormous charge densities and voltages. Chemistry@work. But: Don't ever screw up on them. They may do very nasty things.

My whole point is: When you take all three worlds into consideration, the NiMHs will do >currently< a >slightly< better job as your small but super performing LiPo/LiIon battery because they have more space available. They will simply last somewhat longer because of their Ah value. And you can get them dead cheap.

Performance wise - "world 1" - you are absolutely right!!!

And I can only encourage you to go and the find a 3D printing vendor!!!

All the best and thank you very much or this discussion! I love it.

Thorsten

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Regarding safety, NiMh cells are safer than LiIon. LiIon cells can explode or overheat when not loaded correctly or when they are defective. When handled with care and charged within the specification, both types are safe.

Regarding capacity, LiIon technology is superior to NiMh, it offer more capacity per volume and more capacity per weight. Cylindric cells are not ideal for the Lego batterie box, lots of volume is wasted. Prismatic LiIon cells are available and used in most devices and battery packs, but solitary cells are rarely sold to end users because of the safety issues when used without protective circuits.

The low weight of LiIon cells is an advantage for most applications. For Lego trains it isn't. The more weight, the better the traction.

I'm using the 9V LiIon block below for many devices, but only for those made for 9V blocks, not for Lego trains:

9-v-block-akku-li-ion-conrad-energy-6lr6

The price is 15 Euros.

A pack of Eneloops costs 17 Euros. 1 and 1/2 pack are required to get six cells, resulting in total costs of 25.5 Euros. Thus, Eneloops are more expensive, but they offer twice the capacity.

It should be noted that other brands of AAA rechargable batteries are available for less than 10 Euros.

Edited by legotownlinz

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5 hours ago, legotownlinz said:

Thus, Eneloops are more expensive, but they offer twice the capacity.

It should be noted that other brands of AAA rechargable batteries are available for less than 10 Euros.

Yeeeeeeeessss...No, not at all. In the past I tried a lot of different NiMH cells and have had reliable lousy results. It seems unavoidable to use chargers with single cell supervision and LSD cells.

Up to now I have my doubts, if the capacity value printed on the cell is realistic. My problem is the additional costs for a technology which I do not want anymore to check it out. Caparezza recommends a suitable combination of theTechnoline BC700 charger together with eneloop (pro) cells, wgich are definitely LSD cells. At ebay I've found several dealers who offers all the stuff for about 70,- € (charger and 12 cells). Uh oh, expensive just to check out a claim. But perhaps that's not neccessary if somebody lets its train motor idle together with the lights from full charge down to orange hub blinking. Any volunteer here?

BTW: Li-Ion battery fires are possible but extremly rare. In most case such is reported just to encourage us a little. A leaking NiHM cell pouring auround its potassium hydroxide contents is not a matter interesting enough to be reported. Since there are billions (american notation 1 billion = 10^9) Li-Ion batteries out there, I see no safety issue.

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Saturday afternoon, its raining nonstop outside and I'm a little bit bored. Perhaps the best situation to compare NiMH with Li-Ion technology.

46661849772_5b4e5b9b15_z.jpg

1) Let me introduce my charger. It is designed for model operation at open sites and needs just a 12V power supply, i.e. a car battery. I connect it to a well dimensioned power supply. The charger can charge Pb, NiCd, NiMh ald Lithium cells. The cells can be also discharged with constant current. A microcontroller controls the charging and discharging process. Actual state, current, voltage and capacity is shown at any time on the display. I'm using the charger for several years and can verify absolut reliable function and measurement precision.

2) Let's have a look at the energy density of NiMH and Li-Ion cells. The Wikipedia gives an energy density of 180 Wh/kg for typical Li-Ion cells and about 60 Wh/kg for NiMH cells. Now lets have a look to our suitable cells / battery for the PU hub:

39749532333_5978f9dcf2_b.jpg

The six AAA NiMH cells seems a little bit larger than the Li-Ion block. The six NiMH cells weight together 72.4g, the Li-Ion block only 25.6g. Please keep in mind that the weight contains the housing and the contacts, internal electrodes and so on. Since the NiMH battery comes as six individual cells the weight factor for them is inferior to the compact Li-Ion block.

And now let's measure the capacity. To do this I programmed five cycles of discharging with 200 mA down to 6.6V and recharging with 100 mA. The result is for the Li-Ion block as mentioned above 470 mAh with 7.4V = 3,5 Wh. and for the six cell NiMH battery 350 mAh with 7.2V = 2.5 Wh.

Let's check the charger results with the energy density values from literature.

If all the mass of the Li-Ion block would be available for energy storage the capacity would be 4.6 Wh. with the real measured 3.5 Wh we get a mass factor of 76%, a realistic value since the block is really compact.

The six NiMH cells should store 4.3 Wh if all the mass would be available but six times container, electrodes and contacts claim their tribute. 2.5 measured Wh means a weight ratio of 58%, a realistic value too.

The used NiMH cells are rather new spare parts for my cordless phone. At the last three cycles there were no significant change in capacity of roundabout 350 mAh. The print claims a capacity of a whopping 1000 mAh which is completly impossible if the energy density of 60 Wh/kg for NiMH tecnology is realistic. To realize theese values the energy density must go up to Li-Ion levels -> impossible for the NiMH chemistry. There might be some improvements but not of a factor of three. I am sorry, but I have no reason to alter my claim that capacity values printed on the cells belong into the cloud-cuckoo-land.

And now let's enjoy our running LEGO trains for some relaxed hours!

 

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Wow!

Man, I like this kind of research so much.

1) I totally underestimated the small size of the AAA's as compared to the PP3 ("9V block"). All my trains run on AA's - the printed value is 2500 mAh, which is of course nonsense, but even at half the real power density its fine.

2) I like your weight ratio approach very much. This is rock solid research. I never did that before. It makes all sense!

Very nice. It also explains, why the LEGO LiPo performs like crazy!

Thank you very much for this work. I should continue to rain ...

All the best,
Thorsten

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I use a LiittoKala Lii-PD4 to recharge my NiMH.  It can recharge individual cells instead of needing pairs.  It can also recharge Li-Ion like cells in the 18650 format. So I tried to salvage some Li-Ion 18650s from an old laptop's battery pack to test my new charger.  Unfortunately, all the cells were below 1.75V.  I was hoping to get at least one or two that were still safe to recharge. 

18650.jpg

For a children's toy battery box that allows swapping out of individual cells, NiMH is the safer way to go. NiMH is more forgiving to lack of due care than Li-Ion and Li-Po. Li-Ion and Li-Po need protection circuits to prevent over-charging, over-current, over-discharging, etc. Also need good hazard risk management and mitigation in design and in operation procedures.  Wasn't it the previous Christmas when the hoverboards were popular and a number of them had fires?  Wasn't there a Samsung phones battery recall after some burning butts?   With great power comes great fires.     :pir-classic:

 

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On 1/12/2019 at 11:33 AM, Giottist said:

And now let's measure the capacity. To do this I programmed five cycles of discharging with 200 mA down to 6.6V and recharging with 100 mA. The result is for the Li-Ion block as mentioned above 470 mAh with 7.4V = 3,5 Wh. and for the six cell NiMH battery 350 mAh with 7.2V = 2.5 Wh.

This is solid science!   Thank you so much for running this experiment.  So, at least for the AAA batteries that you have, the 6F22 style battery has significantly more energy storage.  Interesting.  I wonder how that compares with the Eneloops that others are using.

I am going to get a couple of similar batteries to try out.  The ones I've ordered claim to be 9V 6F22 LiPo, 800mAh.  Not certain if it's really LiPo as it claims or actually LiIon as yours is.  Also curious if it's really 9V, or also 7.4V as yours is.  The voltage, at least, should be very easy to check -- but I don't have a way to measure the capacity, or determine the real battery chemistry.

I am hopeful that it's a true 9V instead of 7.4V, simply because I think that should make the motor run about 20% more powerfully.

 

Also, I really like your copper tape solution to interface the battery to the box!  I plan to copy that idea, too.

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17 hours ago, TrainDragon said:

I am hopeful that it's a true 9V instead of 7.4V, simply because I think that should make the motor run about 20% more powerfully.

Hi @TrainDragon

no - a Lipo will never have 9V. Per cell there is an average of 3.6 V. Two of them gives 7.2 V (And three about 10.8 V). That is all there is. What they try to sell is "the size equivalent of a 9V Alkaline" (6 x 1.5 V miniature cells inside). I think it is close to cheating - but oh well.

On another note: Even at 7.2 V, the amount of current that this particular battery can deliver is all what counts. When an alkaline (9V) battery shows a voltage of 7.2 V without load, it is dead. A LiPo at 7.2 V is ready to fry whatever you connect to it :tongue:

All the best,
Thorsten   

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21 hours ago, Toastie said:

no - a Lipo will never have 9V. Per cell there is an average of 3.6 V. Two of them gives 7.2 V (And three about 10.8 V). That is all there is. What they try to sell is "the size equivalent of a 9V Alkaline" (6 x 1.5 V miniature cells inside). I think it is close to cheating - but oh well.

For the actual cell chemistry, you are absolutely correct.

I ended up ordering two different models to try.  I am moderately certain that both will be near a "true" 9V output though.  Someone did a nice teardown of one on another forum that shows two 3.7V cells connected in parallel, feeding a 9V boost converter.  Interestingly, you can actually see the pouches are marked 1776 mWh.  Times 2 cells, divided by 9V, comes out to 394.67 mAh, very close to the 400 mAh claim made on the case.  (I would be surprised if the other brand marked 800 mAh is anywhere near accurate)

The up-side of this: you should get a nearly constant 9V out of the battery until it suddenly drops to zero when the battery is depleted.

The down-side: the boost converter introduces a small constant load on your battery, so sitting there unused it will eventually self-discharge.  Also, the boost converter will be "wasting" some of the energy in the cells doing the voltage conversion, robbing you of some percentage of that raw 3.5 Wh.

 

 

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1 hour ago, TrainDragon said:

The down-side: the boost converter introduces a small constant load on your battery, so sitting there unused it will eventually self-discharge.  Also, the boost converter will be "wasting" some of the energy in the cells doing the voltage conversion, robbing you of some percentage of that raw 3.5 Wh.

And it also decreases the amount of current that can be provided. I once learnt it when I tried to boost 2.6V to 5V (which was enough to power the IR receiver). It was able to power up the receiver, but as soon as motor started to draw the current (and it draws a lot when starting), the voltage dropped to a level that was not enough and receiver shut down :(

So, to make your claim more specific - it's nearly constant 9V as long as you don't draw more than it can handle (most likely it should be able to handle quite a lot, as going from 7.2 to 9 is not as drastic as going from 2.6 to 5 :S )

Edited by Bartosz

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On 1/17/2019 at 5:43 AM, TrainDragon said:

I am hopeful that it's a true 9V instead of 7.4V, simply because I think that should make the motor run about 20% more powerfully.

Also, I really like your copper tape solution to interface the battery to the box!  I plan to copy that idea, too.

Please note my "solution" is only a crude study if we can use Li-Ion 6F22 blocks for PU hubs. Yes, we can. But please also notice it's your own risk! I am not responsible if you short or exchange a circuit and destroy anything!

I've talked with the people from TrixBrix about my idea, but they have no plans to introduce electrical devices. I can understand that becaus it means to mount contact clips and metal stripes by hand or maschine and that's not their business. Unfortunately I have no experience in 3D printing for the contact carrier.

23 hours ago, Toastie said:

no - a Lipo will never have 9V. Per cell there is an average of 3.6 V. Two of them gives 7.2 V (And three about 10.8 V). That is all there is. What they try to sell is "the size equivalent of a 9V Alkaline" (6 x 1.5 V miniature cells inside). I think it is close to cheating - but oh well.

This is not a cheat at all. Li-Ion cells deliver 3.7V, two cells 7.4V. Toastie talks about LiFePo cells which deliver 3.2 V. The big advantage of Li-Ion technology is the very low internal resistance. If you wirk with high currents, ordinary alkali cells will show a significant voltage drop, Li-Ion cells nearly not. My trains are really so fast at full speed that the locomotive jumps out of the rails running over normal R40 curves. Maximum is 70% with Cosmik42s train software.

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