jazzlover

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

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.

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.

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

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.

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

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