DeWalt 9360: Charger Says "Bad Battery"

[PeteCress]

I put one of my 9360's on the charger last nite - even though it had very little discharge - and the all the charger's lights started blinking rapidly: "Bad Battery" according to the legend on the charger.

"OK.... maybe it's something with being almost fully-charged"...

So I put it on the bike and ran it to full discharge - which was just about as expected: 2.something amp hours.

But the charger is still saying "Bad Battery".

Other 9360 on same charger is A-OK, so I'm guessing it's not the charger.

First thing that comes to mind is dirty sensor contacts on the battery, but I can't figure out how to get in there and clean them.

Anybody been here?

 

[kfong]

To clean contacts try vinegar. For the battery use a thin metal blade. An exacto with the tip inserted into the handle, blade is then wrapped with very fine sandpaper used for polishing not sanding. These will clean the big contacts. For the finer ones in the slot you can use the same method on a Popsicle stick. I use 3m contact glue to stick the polishing paper on. This gives me a useful tool that I can reuse later.

 

[Doctorbass]

open the pack and check if all cells are above 2.5V.. if not.. just take the cell under 2.5V and charge them to around 3.0V

than the charger should accept the pack and stop blicking 3 leds :wink:

The easy way ( if you dont have any lipo or lifepo4 rc charger or power supply...)
to charge them you can use a 12V high beam bulb in serie with a 12V car charger or battery and connect it to the cell directly and disconnect it when it reach 3V. But watch the process.. dont leave it alone.

best is to bring all 10 cells to the same voltage and above 3.0V and then to charge the pack for 12 hours on the dewalt charger.


Doc

 

[PeteCress]

open the pack and check if all cells are above 2.5V.. if not..

Lowest cell was 2.96.

Cell#	Voltage
-----------------
1	3.00/3.01
2	3.00
3	2.98/2.99
4	2.96
5	2.98
6	2.98/2.99
7	3.00
8	3.02/3.03
9	3.01
10	3.02

Also, in support of no cell being bad, the problem occurred when I put the battery on the charger after only consuming about a quarter amp-hour (actually, a ride where 2 batteries were used, total consumption .5ah).

So the day before, the battery was OK coming off that charger at full charger - yet the next day, at almost full charge, the charger sensed it as bad.

And I'm pretty sure about the "almost full charge" because (foolishly?) I ran it until the BMS kicked in and the CycleAnalyst said the usage was just shy of 2.2 ah. If a cell were bad, wouldn't I see fewer AH total consumption?

Have not yet found the bits and pieces to apply Kin's cleaning technique. That is next.

Suppose that cleaning does not work: would it be reasonable to suspect a fried BMS?

 

[kfong]

Try cleaning first, since the contacts do get pitted and dirty from road use, it would be the data pins that would be suspect. If that doesn't solve it then I would then suspect the BMS or the wiring going to the batteries. The sense wires may have a bad connection, these are the fine wires going to each cell for the BMS to monitor. Batteries look fine. I think I might have a spare bms.

 

[PeteCress]

The sense wires may have a bad connection...

Even though there are 10 cells, there are only a total of nine sense wire pins on the connectors, right?

(five on one connector, four on the other).

 

[Doctorbass]

The sense wires may have a bad connection...

Even though there are 10 cells, there are only a total of nine sense wire pins on the connectors, right?

(five on one connector, four on the other).

You must add the positive and negative that act as sense wire for the cell 1 and 10 and power wire
.

Doc

 

[Doctorbass]

open the pack and check if all cells are above 2.5V.. if not..

Lowest cell was 2.96.

Cell#	Voltage
-----------------
1	3.00/3.01
2	3.00
3	2.98/2.99
4	2.96
5	2.98
6	2.98/2.99
7	3.00
8	3.02/3.03
9	3.01
10	3.02

Also, in support of no cell being bad, the problem occurred when I put the battery on the charger after only consuming about a quarter amp-hour (actually, a ride where 2 batteries were used, total consumption .5ah).

So the day before, the battery was OK coming off that charger at full charger - yet the next day, at almost full charge, the charger sensed it as bad.

And I'm pretty sure about the "almost full charge" because (foolishly?) I ran it until the BMS kicked in and the CycleAnalyst said the usage was just shy of 2.2 ah. If a cell were bad, wouldn't I see fewer AH total consumption?

Have not yet found the bits and pieces to apply Kin's cleaning technique. That is next.

Suppose that cleaning does not work: would it be reasonable to suspect a fried BMS?

Ok so that confirm all cells are good.

now it could also be the internal 15A fuse of the bms on the second negative output?.. it depend on wich neg output you are connected

or do you have regen active on your controller?

Do you think you could have run downhill and generate voltage higher than the battery?.. and blow the internal BMS with fets or diodes...

does the bms become warm when you put it on the charger?

Doc

 

[Doctorbass]

I'm pretty sure it's with the BMS.

-contact could need to be cleaned like kfong said.. The oxide of water and contact material could create some resistance value between some contact pins and confuse the bms. The tool that these battery are made to work with are using resistor value too to set the bms in the right power output.

-or.. the bms is blown...if so.. i have alot of them tested OK so pm me if you need one.

Doc