Hi, I have just acquired part of a 5151 set (hub + 4 motors and the two sensors).  As I suspected (as the hub was photographed with a power lead plugged in), the battery wont hold any charge.  I plug it in and hub led changes from red to green within a minute.  As soon as I unplug it it immediately turns off.   I have a second hub + battery and putting the working battery in the this new hub works fine, so its definately a battery issue.

I have had this issue with eneloop NiMH batteries before where they wont start charging in a charger but will if I connect another fully charged battery to it.  It then starts to charge.   Does anyone know if its possible to do something similar to the hub battery?  If this isnt possible or the battery is just deadcan someone tell me if the Spike Hub and Mindstorms hub batteries are interchangeable.   The reason is that a replacement battery for Mindstorm hub is around £80, whereas I can pick up the Spike one for £30 (Id just have to put up with the colour clash!!!

Thanks

Nigel

Apart from the color, the batteries are identical as far as i know. I have one of each hub, and the batteries both work just fine in either hub :)

37 minutes ago, barberminged said:

Apart from the color, the batteries are identical as far as i know. I have one of each hub, and the batteries both work just fine in either hub :)

Thanks - I assumed that was the case but good to have it confirmed

For anyone who has the same problem, I've managed to get the mindstorm hub battery to take charge again.  I applied 7.4V across the outer two battery terminals and left it there for about 3 minutes.  It was enough to kick start the battery and its now plugged into hub and charging.  Of course I wont know if this is a permanent or temporary fix for a while - but its looking very positive at the moment!!   I might have just saved myself £80 for a new hub battery.

@jazzlover Thank you for that feedback! I got three new SPIKE Essential batteries directly from LEGO.com that had the same problem. Out of the box totally flat and not charging. Production dates on the back of the battery showed that all of them were produced in 2021. I got replacement batteries from 2022 that were 70% charged on arrival and they are charging in the hub. I will try to save the other three batteries with your method.

Can you please give an indication what side was plus or is it visible what is the right one by the illuminating charging LED and applying power to the wrong side is not a problem for the battery?

Edited August 8, 2024Aug 8 by Berthil

So you use the two outer terminals (there are three).  The red is the positive terminal and black the negative.  I used a Maplin bench power supply to do this as you can accurately set the voltage and slowly increase the current.  They don't make it anymore but this one would do the same thing:https://uk.farnell.com/duratool/d03232/power-supply-1ch-15v-2a-adjustable/dp/4161317?gross_price=true&CMP=KNC-GUK-GEN-SHOPPING-PMAX-High_ROAS&gad_source=1&gclid=CjwKCAjw2dG1BhB4EiwA998cqI6CJbfW7mUCw16kGo9AqKvzNMuYh1U4KLI5m2oUnn32WfBeKRlW9RoC_fkQAvD_BwE

 

I can confirm that the battery has now charged to 100% (as reported by the Mindstorms app), and the light has turned green, so all seems to be OK.

I tried today with the smaller SPIKE Essential battery but I did not have such a power source. I used a 9V train power supply with 6,6V and 7,7V on position 4 and 5. That didn't work. I checked voltage on a working battery and that was near 8 Volts but positive and negative on the battery was reversed compared to your connection info. So I reversed poles and upped to maximum of 9 volts on position 6 of the train power supply but nothing worked. I'm wondering of the exact voltage of 7.4 does the trick and if I should buy such a power source.

 

 

Hi, the advantage of using a bench power supply is that you can set the voltage and then separately increase the current.  If the battery wont take any current then I'm not sure it can be fixed, but I found that initially it took zero current and as I increased the current on the power supply it suddenly started showing current flow.  Once that happened then the battery started charging in the hub.  Also you have to press quite hard on the terminals to get a good connection.   Interesting about the polarity though.  I initially connected a voltmeter to a good Hub battery to check the voltage and with the positive lead connected to the one I highlighted in red I got a positive reading of 7.4V, so when I connected the power supply to the faulty battery I again connected the positive supply to same terminal.

@jazzlover How much was the working current please? As I have some resistors and can measure current at the earlier mentioned voltages. If I up resistance current should go up right? I read 600mAh on the back of the battery so is 600mA the current I should be aiming for? I know the 9V train power supply can handle up to 1000mA or shuts down when it goes higher. I have three of these SPIKE Essential batteries and TLG advised to dispose of them in the correct recycle bin but that seems such a waste. I tried to get the voltage down to 7.4 with the resistors but voltage was constant so the 9V power supply must have upped the current but I didn't check. If I know what the current should be I maybe can try with resistors to get there.

Edited August 9, 2024Aug 9 by Berthil

Hi,

I cant remember the working current as it was initially 0 (where the battery was refusing to take a charge) until i suddenly reached a threshold and current started flowing but I didnt take a note of what the current was.  Sorry.   I could repeat it but that wouldnt be of much help as the battery is now charging properly. Battery still showing 100% this morning

13 hours ago, Berthil said:

@jazzlover How much was the working current please? As I have some resistors and can measure current at the earlier mentioned voltages. If I up resistance current should go up right? I read 600mAh on the back of the battery so is 600mA the current I should be aiming for? I know the 9V train power supply can handle up to 1000mA or shuts down when it goes higher. I have three of these SPIKE Essential batteries and TLG advised to dispose of them in the correct recycle bin but that seems such a waste. I tried to get the voltage down to 7.4 with the resistors but voltage was constant so the 9V power supply must have upped the current but I didn't check. If I know what the current should be I maybe can try with resistors to get there.

I don't know if I have much helpful to add, but I would clarify that the 600 mAh on the battery is just referring to its capacity, meaning that if you hypothetically wanted to discharge the entire battery in exactly one hour, you would have to be drawing a constant 600 mA to do it. Because of that, I don't think inferring that 600 mA is a good target current to plug into it--it's just talking about capacity, rather than the current it actually outputs.

One other thought, though: If you have a potentiometer (or rheostat), which is basically a variable resistor, often controlled by a knob, you could potentially manually adjust current similar to the way you would with a bench power supply. That being said, when I have ideas about what a setup like this should do in theory, it often doesn't work as I expect in practice!

Spoiler

Potentiometers