Slimline Battery Advice

[Griffo]

Hi,
I was wondering whether anyone could give me advice on whether all 3 of my battery packs are likely dead.
I have 2x DR slimline lights, 3 battery packs, and 2 chargers. All are the older trailer plug NiMh style.
The batteries are of various age, and the two chargers are also different. I've just pulled them out of storage after leaving them for 12 months unused (they were charged before being put away). I know, i know, I shouldn't have done that.

Anyway, on initial charging and testing, all 3 were hopeless. On the same LED light they gave me initially

B1: 5 seconds (oldest, green batteries)
B2: 10 minutes (second oldest, green batteries)
B3: 30 minutes (newest, orange Panasonic batteries)

After a few days of a discharge / recharge cycle with the light in a bucket, i have got them to

B1: 1hr 30
B2: 4.5 hrs
B3: 8 Hours

OK great.. to some extent. B3 gives me the full 8 hours, and B2 is good enough for my upcoming tropical holiday where I only need 2 hours a day. B1 is obviously stuffed.

However.. they all keep giving me false peaks when charging- i.e the chargers are shutting down. C1 is an older DR branded black charger, and it's just hopeless. Nothing charges more than 30 minutes before it shuts down. Testing the pack will generally show around 12 - 12.5v after removal.

C2 is a DiveGearExpress green thing that does do better, however I still generally need to re-start it 2 or 3 times to get them to what i'm guessing is full charge. Initially the packs seem to be at 13-13.5v on first "stop". After giving it a couple of restarts, the voltage of the pack will come up to about 14.6v.

So.. do people think i've stuffed all 3 packs? B3 seems to get decent run time but false peaks, which means I can't just throw it on a charger at night.

Three new battery packs is a fair chunk of change.

 

[guruboy]

Do your packs have the screw on white covers at the top and bottom? If so, unscrew and check the voltages across the "stacks" of batteries to see if they all match. See if you have any dead cells in B1 and maybe B2.


As far as the charger goes, they're pretty cheap generic made in China crap. I had a similar issue where the charger stopped at 13.5V or so. If yours has the red and green light, try leaving it plugged in for a long time and see if the red light ever goes out leaving just a solid green. I'm not sure if it's supposed to trickle charge to full over a LONG time or what.


I switched to a much nicer charger and my pack gets full charge OK and doesn't "stop" at 13.5V anymore.

 

[guruboy]

I've also considered making my own 4S 18650 packs for the light to replace the aging NiMH pack. Would be 14.8V nominal, 16.8V fully charged. Not sure if the LED head will handle that much voltage though.

 

[tbone1004]

get a better charger if you want to try to refresh those packs. Doesn't have to be a scuba branded charger or whatever, just a nimh charger of the right voltage, preferably with a refresh option.

something like this
Intelligent Digital Balance Charger/Discharger for (NiMH/NiCD 1.2V-18V, Li-Ion 7.4V-22.2V, LFE 6.4V-19.2V, SLA 2V-20V) Battery pack

alternatively go to batteryspace and find something with the same ish dimensions and same ish voltage and buy that and a charger. They likely already have one made up for you that will drop right in that can under their diving light section. I would NOT recommend building your own, unless you have the right equipment it's a recipe for fire

 

[guruboy]

If canister space allows, it's very easy to build a small pack using battery holders and some simple soldering of wires. No battery soldering or spot welding required.

 

[Griffo]

If Only I could just go to batteryspace. They won't ship to Australia which is a shame. They have direct replacement packs for $65. The DR ones are $170 online ($210 locally). I did look at building my own pack as a replacement, however I can't even seem to locate the cells for a reasonable price - they are like $13ea for some reason on eBay (for Panasonic), and when I need 30 of them..... I'm not sure how BatterySpace makes them so cheap.

I want to stay NiMh as we do most of our diving as travel diving, so I don't want to run into any Li-Ion / LiPo issues.

Good point too about opening the battery pack to test individual cells, I thought from memory that they were fairly glued together but I'll have another look tonight.

 

[rboyer]

I have the same set up (led) Id like to try to make my own battery also....with the battery holders but not really sure how many 18650's Id have to have.....

 

[fmerkel]

That's a 12v/nominal > 14.5v fully charged pack. If you are hitting near that with 1 pack it is 'maybe' OK. The others likely have 1-2 dead cells. What happens over time abuse (over discharge), and neglect, is the internal resistance goes way up and/or individual cells die (very high resistance). The charger can't handle that and terminates. If you charge up, let them sit a couple days and the voltage isn't 13.5v or higher you can be pretty sure you have at least 1 dead cell. IMO, since they ALL have a 'checkered past', it may not be worth cell replacement unless you are broke or desperate. You'll just be having other cells die pretty soon. If you are careful you should be able to open them up and check individual cells. With the dead one to practice on you have nothing to lose.

So, replace the pack as is, or make new packs. Li-ion 3-cell (3s) is 12.6v fully charged, will hold the voltage pretty well, but is far more likely be be ruined by over discharge. A 4S pack is 16.8v and may or may not fry the light. I'd bet on 'fry'. You would need a new charger.

You could build a pack out of LiFe packs. These are 3.6v fully charged so a 4S pack would be great......except, capacity is much lower (like 1100mA), and you definitely need a special charger, NOT a stock Li-on charger OR NiMh. But the chemistry is MUCH safer and more robust than Li-on.

Making a lithium pack is NOT a simple soldering job. You need to add a balancing tap or a special protection board to keep them safe.

 

[guruboy]

I would go with battery holders and try a few 3S in parallel.

 

[fmerkel]

For a slimline you'd need 3S in a triangle configuration, then parallel those together. I've never seen that kind of holder.