help needed-new battery? new charger? something else?

Batteries and Chargers Rechargeable Batteries
1

Hi,
I have a SAD LED light panel that is used for seasonal depression, that I bought ten or fifteen years ago. My daughter would like to try it, so I found it and it works, but it won’t hold a charge.

I opened it up and found the batteries. They are 2/3AA size and there are seven in series, each one is 1.2 V and 750 mAH. Each one reads over 1.2 volts except for one, which has no voltage.

I was going to replace just that one, but I don’t know what type of battery it is and when
I took off the plastic wrap that held all 7 of them together, there was no information at all on the individual batteries.

The label on the plastic wrapping said:

NIKKO
7NK-2/3AA750mAh
8.4V 8G07

If I knew what type of batteries they are, I could buy one to replace the bad cell.

The charger plugs into the wall, and it says “input: 100-240V 50/60Hz 0.4A Output:9.0V 1.1A”

So I have many questions. Is there a way to tell what type of batteries these are so I can replace the one bad battery?
Or, could I buy a new NiMH battery pack like this:

Is the charger meant to work with a specific type of rechargeable battery? I’ve read that you can’t use a NiCd charger on NiMH batteries. Do I need to stick with the original type of battery to drive the LED light panel?
I would be grateful for any advice on how to proceed. Thank you very much.

2

It’s a standard 2/3AA cell size (standard, though not common in the aftermarket…more of a manufacturer size). Just google 2/3AA with or without the 750mAh addendum and there are several places to buy them from. Amazon has several listings and you could probably also find them at Digikey, etc. I don’t know if there are any particularly good/bad brands for who offers this size cell but generally Panasonic and Fujitsuj/FDK and GP are good quality.

You can find battery heat shrink wrap cheaply, too, although you’ll need to measure and determine what size will work with that pack (usually wrap is measured laying flat, so some basic math needed).

I would stick with the charger that came with it but keep in mind that the rated output for the charger isn’t necessarily what is being fed to the cells, just depends what sort of battery management/charging circuit is in the device.

If you’re handy with a soldering iron you could probably carefully replace just one cell in the pack although it’s usually best to use all fresh cells that are matched (e.g. your one new cell may not be the same in terms of internal resistance or other qualities, so being mismatched against the other six may lead to issues again down the line). Soldering to NiMH or NiCd cells is fine, less risk than doing so with Li-ion, but you still want to get the work done quickly to limit high heat on the terminals/battery juice in the can.

I didn’t look at the pack you linked to, but if it’s all seven cells wired in series and the connections and such are workable for your device, then it should be fine. 1.2V per cell x 7 in series = 8.4V nominal.

3

Agree with Correllux. I doubt a pack that old and neglected is worth even trying to recover unless you are skilled with a solding iron and like a challenge. One cell dead, probably the rest are lame.

NiXX batteries have the same ‘general’ characteristics. If you have the room in the device you could consider going up to full AA pack for more capacity. Finding reliable quality in that size could be a challenge. Home cordless phones are often a similar problem. Lots of glowing claims that often don’t work out.

This site also deals with NiXX packs of various sizes.

4

Thank you both. I’ll go with the full replacement set. The one remaining question is charging. If my original cells were NiCd, is that charger safe to use with NiMH, or even Lithium (I see a lot of “Lipo” packs with specs that work).
I’ve read that the rate of charging used on NiCd can damage other types of rechargeable batteries. Is that something I need to worry about? If I switch to NiMH or Lithium, dob you recommend that I also get a new charger?

5

How do you use it? Plugged in all the time, or charge when needed? Does it charge “all the time” or is there a red/green light signal for a finished charge?

6

As said, it’s not just the charger, it’s the circuitry that is (presumably) in the device that is actually controlling what the cells get. Switching power source (batteries) mostly requires charger/charging circuit to match, so you’d kind of need to know what all is going on inside the device itself to see if changing source is feasible. I think you could swap NiCd and NiMH just fine…might notice a slight difference in run time depending on what the charging circuit does and how it terminates, but it shouldn’t hurt the cells. NiCd are more robust but NiMH usually have more capacity and flatter output curves at low to moderate current loads. It’s possible the charger is actually doing all of the deciding, as I think flydiver was alluding to, but it could be/usually is in the device instead.

All that aside, if you were to use a lithium chemistry, yes, you would definitely need a different type of charger/charging circuit. They way they charge and terminate is different and a charge output intended for 1.5v cells would never fully charge lithium with higher nominal voltage. But you can’t just swap them to something different on a whim without knowing the circuitry and design of the device.

7

On a side note, this is a very informative thread.

8

It remains plugged in all the time. I tried to use it without the batteries since I pretty much never use it without being plugged in, but it doesn’t work without them. It powers off after about half an hour or so.
The charger is just your run of the mill plug in transformer with no lights at all. I was going to post a picture but I don’t see how that can be done on this site.

9

Given the age I suspect it’s a low output, possibly constant charge unit. 2 questions:

  1. What is the output? Should be inscribed on the plug-in.
  2. You said you have a dead cell in the pack. Does the unit not work that way, even plugged in?
10

In case anyone is still willing to offer help, here is more info.
The charger transformer says output: 9.0 v 1.1 A

I reinstalled the battery pack, with the dead battery. The light did turn on even in that state without plugging it in.

When I plugged it in, there was a flashing battery icon, which I assume is because the battery is faulty.

There are two main buttons: “Power” turns on the display and allows me to set the alarm, and “light” turns the lights on.

What is happening is that I turn it on with the Power button, the display comes on as expected. I set the alarm, and after about half an hour the display turns off and the alarm never goes off unless it was set to go off before the display turned off in that half hour window.

The “alarm” in this case is the lights turning on. It used to have an audible alarm as well but I disconnected the wires to the speaker when I opened it up, because my goal was to be woken up by the light without the audible alarm.

So, to summarize, with the faulty battery pack installed, and the unit plugged in, the display turns on when I press the power button but there is a flashing battery icon. I can set an alarm, but the display turns off after about half an hour and any alarms set beyond that time will not turn on. When functioning properly, the display would remain on so that any alarm I set would go off at the proper time.

Maybe it requires a functioning battery pack to keep the display on., and maybe that would also stop the flashing battery icon, and then the display might remain on so that my alarm functions. That’s my hope. I don’t know if it makes sense that all of that would hinge on having a functional battery pack that takes a charge properly.

The cost to find out would be either a single 1.2 volt battery (I’m assuming they are nicad although I have no way to know), or a full set of new batteries in 2/3AA size. All I can find are NiMH, so that is probably what I’ll try unless someone can make sense of what’s happening.
Thank you all. I hope I was clear.

11

Sounds like the transformer is charging the pack, and the pack is running the device. Having a faulty cell probably has shorted the pack, making full charge impossible.
You might try a ‘trick’. Sometimes old/dead cells can be ‘jumped’ back to (partial) life. I have done this with a similar tool pack. It might work, but it won’t fix it as that cell is lame and will simply go dead again.

Get a lithium cell (4.0v) or 2-3 NiMh cells. You want a little ‘over’ voltage, not a lot.
Using that for power connect + to +, and - to - on ONLY the dead cell. You might get some minor sparking or the wire heating up. Not unusual. You only have to do that for a few seconds, and maybe repeat it a few times. Then see if the ‘dead’ cell, now exhibits voltage. It may exhibit 0v, or a voltage that seems improbable for an essentially dead cell. If 0v, you either need to replace that cell, or replace the pack.
If you have (some) voltage, plug it in and let it charge for a good while. Then test for normal function.
IF….it works, you will still have to do some kind of replacement as that cell will not carry any load in a reliable fashion. I’d replace the pack as the rest are also quite old.

12

I would assume, without seeing the device in photos or anything, that the dead cell is causing the pack to deliver lower than expected voltage, just as it would if all cells were healthy but drained to the point of needing to recharge. Clearly the device has some smarts onboard, so it’s likely it’s just sensing that low voltage and telling you to fix it. If the charging circuit (wherever it is) allows a “full charge” but only 6 of 7 cells are getting that, then you’ll never get real full voltage from the pack…or if you do because the others were overcharged a bit, it’ll only last for a moment before surface charge is drained and you’re back at too-low voltage.

Electronics revolve around voltage first, current second. If the power supply isn’t delivering enough then the rest can’t work well or at all. Just change the cell or the whole pack and you should be good. Personally I would not try to revive that cell…even if it works it likely has permanent internal damage from being so drained and as a member of a series configuration and it’s possible/probable that the other six cells have received more than their fair share of wear as they tried to pull the sled with one less dog (there’s only so much they can do, but still). Better to just get new ones of good quality and start fresh. It’s fun to experiment, though, and if you just do one cell and things go south for whatever reason, you’re not likely to damage the device or have safety risks, so your choice.

13

Thank you all for the helpful suggestions. I’m going to look for a battery pack to replace the one I have. I can solder the connector on if the new one comes with the wrong connector.
I’ll shoot for 1.2V with 7 batteries for a total of 8.4 volts, just like the original was, and I’ll try to find NiCd or NiMH since it sounds like they would work best with the charger.

It may take me some time to get this done, but I will definitely report back.

I’m very appreciative of all the help and guidance.

14

I have the Apollo goLITE P2
The battery pack has 7 cells 2/3 AA
on the battery pack is:
NIKKO
7NK-2/3AA750mAh
Ni-MH 8.4V 7A09

The AC adaptor
Input: 100-240V 50/60 Hz 0.4A
Output: 9.0V (symbol for DC) 1.1A
right angle barrel connector, positive is in the center.

Anyone have the schematic for this? I found a capacitor off the board, it may be C4, but cannot read the size or type.

goLITE battery
goLITE battery1440×2560 273 KB

15

It’s a pleasure to have you onboard, BarcBarc!