Strange battery behavior.....

[fritter63]

So, this week I was using my CXS-18, which I bought as a bare tool. I got two 18V batteries with the vecturo purchase in November (2023) so I figured I don't need any batteries.

Total charge cycle times on both batteries probably < 10x (maybe 5x). After I finished, I put the battery in the charger with 1 bar showing.

Later I noticed it was flashing RED. I figured it had been too hot to charge. So I put it in again, same results. It starts flashing green, then goes to RED (or maybe it was amber?).

So I start to collect info make a warranty claim and decided to try it one more time (several days later). THIS time it charged just fine to full, showed solid green at the end.

Very odd, any ideas what could be going on here?

 

[kevinculle]

I have seen a similar issue with a lithium battery when the battery gets to a very low state of charge.  Below a threshold voltage the charger will conclude the battery is defective and not charge it.  In my case I used a second charged battery (with an 8 ohm power resistor in series to limit the charge rate) to bring the voltage up enough that the charger would charge it.

 

[six-point socket II]

The ‘too hot’ would have been a non-issue at the second try. So I doubt that was/is an issue.

What [member=60975]kevinculle[/member] points out is way more likely. It shouldn’t happen, but it can. Maybe just a hick-up, especially with one bar still showing. Maybe the BMS got a bit confused …

Keep your eyes on it, see if it happens again when the battery was used in the CXS-18. Put a piece of masking tape on the battery so you can positively identify it.

I have re-started/ run tools after they had stopped/indicated a flat battery - but never ever did one quit on me or wouldn’t charge after that. Should not be regular/ common practice but I did maybe 2 or 3 times …

What I want to say is, today’s batteries, of quality manufacturers, are pretty well protected. So I’m in the camp of hick-up, glitch, BMS/software “fault” or communication error.

If it happens again, especially after using the CXS-18, contact Festool and have both items checked.

Kind regards,
Oliver

 

[Cheese]

I have seen a similar issue with a lithium battery when the battery gets to a very low state of charge.  Below a threshold voltage the charger will conclude the battery is defective and not charge it.  In my case I used a second charged battery (with an 8 ohm power resistor in series to limit the charge rate) to bring the voltage up enough that the charger would charge it.

This... [smile]...especially if you put a battery away on a low charge and then come back a month later to use it. I haven't experienced it with Festool batteries yet but then again, I've been very careful with Festool because I've experienced it so many times with Milwaukee batteries.  [mad]

 

[fritter63]

I have seen a similar issue with a lithium battery when the battery gets to a very low state of charge.  Below a threshold voltage the charger will conclude the battery is defective and not charge it.  In my case I used a second charged battery (with an 8 ohm power resistor in series to limit the charge rate) to bring the voltage up enough that the charger would charge it.

This... [smile]...especially if you put a battery away on a low charge and then come back a month later to use it. I haven't experienced it with Festool batteries yet but then again, I've been very careful with Festool because I've experienced it so many times with Milwaukee batteries.  [mad]

Understood. But in this case I had just been using it (from full charge) and then checked and saw that it was at one bar, so decided to charge it.

Very odd. Yes, have a piece of tape on it so I can identify it, watching it closely!