Power Function Rechargeable Battery 84599/8878 woes

[zephyr1934]

I have a PF Rechargeable Battery 84599/8878 that was charged at least 5 hrs but the charging indicator light still flashes red, instead of going to solid red indicating fully charged. I used two different chargers (both are Lego PF chargers). In the meantime I charged several other batteries in the same setup, all of which went to solid red after about 2 hrs. So it is almost certainly the specific battery. I'm starting to prepare for a small public train display next week, so that means pulling out all of my locomotives with built in 8878 batteries for the trains I plan to run and topping off the batteries.

After at least 4 hrs of charging I took the engine off the charger and attached it to a train to see if it had any charge and to eliminate the possibility that it was simply stuck in an "almost full" or "just barely over full" state. It pulled fine for at least 30 min. Then I put it back on the charger for maybe 2 hrs and the red charging light continued to flash, never going to solid red.

I probably last charged and then ran this engine at brickworld 2022, with the charge indicator light going to "full," I did not fully discharge the battery at that time, and I don't think I've used or charged it since. Several of the other batteries have had a similar or longer idle time. But this locomotive is probably the most heavily used of my collection, so it makes sense that it would be the first to wear out.

 

My current thoughts are:

1) if the battery is not behaving as expected it probably meas that it is at or near the end of its useful life (at least without a major overhaul to replace the cells)

2) it is a Lego battery that has not been abused so it will probably fail safe, i.e., the train might stop running but it probably will not burst in to flames (in a literal sense) while in storage, charging or running

3) so my strategy is to run the train until the battery turns itself off (either depletion or timing out after 2 hrs) while keeping track of how long it lasts (typically this train would time out at 2hr but be mostly depleted at that point) and I'll recharge from there to see what happens.

 

Anyone with more knowledge about these things have any reason to question these thoughts?

 

 

Meanwhile, there are some nice threads about these batteries never going to full charge (blinking red without going to full charge) but it seems those batteries did not hold any power. And in one case doing a major overhaul to replace the cells (I'm not prepared to go there right now)

 

 

[JopieK]

I would indeed go for replacement. First you could already check if the cells are swollen or not and/or use a multimeter to measure the cell voltage.

Look also here:

https://www.planetdiecast.com/index.php?option=com_zoo&task=category&category_id=470&page=18

[zephyr1934]

3 hours ago, JopieK said:

I would indeed go for replacement. First you could already check if the cells are swollen or not and/or use a multimeter to measure the cell voltage.

The battery is built into a MOC so to spot any minor swelling would require disassembly. Major swelling would probably pop the MOC apart and there's no sign of that.

I just tried a volt meter and got just above 8v (consistent with no load here). So that tells me that neither cell is completely dead.

I don't mind if the train only runs for 30 min and then stops, at this point that's easier than taking the MOC apart. I will have 6 other locomotives with me so I'd just box it up.

[Toastie]

On 10/8/2023 at 5:08 PM, zephyr1934 said:

It pulled fine for at least 30 min. Then I put it back on the charger for maybe 2 hrs and the red charging light continued to flash, never going to solid red.

Sorry, late to the game.

I have seen a similar behavior on some of my 8878's. Sometimes that is. They always perform though. The charger you use is the 10V type from TLG, isn't it? If so, did you try a more capable charger? You can charge 8878 with any DC power supply up-to (very safely) 15V, unlimited amps, as the circuit built into 8878 takes care of "everything".

Is pulling for more than 30 min OK? If so, there is nothing wrong to the extent of being worried. Swelling of the LiPo pouches will not show on the outside; there is plenty of room inside 8878 for expansion (TLG did do the math, I believe).

I'd just go and let it run.

Best,
Thorsten

 

[zephyr1934]

6 hours ago, Toastie said:

I have seen a similar behavior on some of my 8878's.

Excellent and that was the biggest thing I was looking for. I'd really hate to be the only one on the planet to get a particular warning message (grin).

6 hours ago, Toastie said:

They always perform though.

Okay, maybe that's even better to hear. I guess I was unclear, the train ran for 30 min and I shut it off, it appeared to still have plenty of juice in it. Yes, I'm using the lego 10v charger. I don't really care if the battery never tops off, but it is good to hear that it probably has plenty of life left in it since the batteries have been discontinued for so long. I'll know for sure about the run time on Sat when I plan to run it until it is exhausted.

[dr_spock]

The cells could be worn and don't have the same mAh as when new. Or they could be out of balance. Fully charged 2S battery should be at 8.4 volts.