"timed chargers": Could we all use one ?

[PeAK]

Rainy day discussion​

I was at Walmart perusing their chargers when I came across the attractive Engergizer CHCC charger (aka Energizer Simple Charger). From the packaging I thought:

"Hmmm...Could this be a smart independent channel charger where a famed battery company finally figured out how to reliably terminate at low charge currents below 0.5C ?"

Stocking Stuffer Price: $16
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Some of the larger companies are not exactly forthcoming on details of their chargers as this is a reduced version(to fix forum 800x600 size restrictions) of the instruction sheet prior 2008 will show:​

Some confusion arose within this forum as to whether to recommend this charger based upon the above specs as it appeared to have independent channels and adapt the charging time for different capacity/size cells. Eneloop like 2000mA-H batteries would charge in 6.7 hours while larger 2650 mA-H batteries would take 8.8 hours. Seems smart enough...but how do they figure out if the battery needs 6.7, 7.0, 8.3 or 8.8 hours of charge ?

My take on the LEDs is that they exist merely to show whether the batteries are connected. I highly doubt that separate timers exist for each channel...more likely that they all stop charging after a shared timer clocks out.


This is the updated (2008) instruction sheet for the same charger:

Note that the details have changed and that the "Timer Auto-off" now only applies to the 2450mA-Hr battery. It is much more apparent now that lower capacity 2000mA-Hr batteries need to be manually removed from the charger (to stop the charge) at the recommended 7 hour mark or to be left in for the "timer" to end the charge at 8.5 hours. The result: 1.5 hours of excess charge that is not needed by the battery and will lead to heating and further reducing the number of potential charge cycles. Despite these shortcomings, a thought emerged from the near standardization of LSD cells at the 2000 mA-H capacity

Dec 19 Update: I think I need to be corrected on the point about the 1.5 hours of overcharge as I did not factor in the coulometric charge efficiency.
When this is accounted for the total mAh number becomes 8.5*0.66*360=2020 mAh...or just about perfect for eneloop/LSD capacities of 2000mAh. The only caveat being to charge with depleted batteries.
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"Hey, could a timed charger be a possible path to more optimal charging of NiMH cells for long battery life?"
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I think YES with a few provisos/modifications to make this simple scheme work more optimally with 2000 mA-Hr LSD cells:

1. Initial Discharge:
   The cells should be discharged first. Manufacturers should provide a means for consumers to ensure this so as to not lead to excessive charge using their "simple" timed chargers. How about adding this inexpensive automatic DIY Discharge Circuit
2. 7 hour time out(for 360mA charge current):
   All timed chargers should be optimized for the slightly lower capacity LSD cells or 2000mA-Hr. To correct this, you can use one of those 24 hour programmable timer/switches

With this initial discharge step, I think it would be possible to get the following advantages compare to todays predominantly negative delta-V based smart chargers:

1. Never miss a termination
2. Fuller charging due to lower current
3. Cooler batteries

For users with a stash of 2500mA-hr cells, this Energizer Simple Charger "out of the box" may be an ideal way to charge batteries. The only downside (provided they are nearly fully discharge from use) being the longer charge times ....to cope just plug sleep through the overnight charge: Like the good ol' days of dumb chargers.

I'll spin some vinyl in the morning...:thinking:
PeAK

 

[Elliot]

Re: "timed chargers": Do we all need one ?

Years back I had a simple charger that just worked off dT - didn't care about capacity or time. Never had a problem with it, for some stupid reason I gave it away.

 

[Mr Happy]

Re: "timed chargers": Do we all need one ?

If you combined that charger with an external timer it would work out quite well. Put a set of discharged eneloops in it, set the timer for 6 hours, and you are set.

A charge current of 360 mA (AA)/150 mA (AAA) is low enough to cause few problems from slight overcharging, but high enough to achieve reasonable charge times.

 

[PeAK]

Re: "timed chargers": Do we all need one ?

If you combined that charger with an external timer it would work out quite well. Put a set of discharged eneloops in it, set the timer for 6 hours, and you are set.

A charge current of 360 mA (AA)/150 mA (AAA) is low enough to cause few problems from slight overcharging, but high enough to achieve reasonable charge times.

With only 6 hours needed to charge, an overnight charger could have enough of a time budget to also do the above mentioned discharge step. The conditioning functioning would amount to discharging the cell to 0.9V prior to applying the timed charge. This type of charger was offered by Radio Shack in 2002 going by Model 23-335. It cost $13 back then when two additional switches were added to accomodate 4 common battery capacities(700mA-hr, 900mA-hr, 1200mA-hr and 1400mA-hr) . The only downside was that it charged a pair at a time.

I buy this charger in a heartbeat if it supported independent channels for discharge and charge....much simpler/cheaper than the Maha C-9000 approach with many of the same advantages for taking of your batteries.

 

[TakeTheActive]

Re: "timed chargers": Do we all need one ?

...The conditioning functioning would amount to discharging the cell to 0.9V prior to applying the timed charge. This type of charger was offered by Radio Shack in 2002 going by Model 23-335...

• Pretty easy to find those OLD RadioShack Charger specs, eh?
  .
• I looked and looked but couldn't find the DISCHARGE CURRENT. Only that the Discharge Function stops @ 0.9VDC.
  .
• Although I only use it for my C and D cells, I think I'll add my RadioShack 23-428 Universal Ni-Cd/Ni-MH Battery Charger to my "Termination Testing" experiment. :wave:

 

[PeAK]

Re: "timed chargers": Do we all need one ?

• Pretty easy to find those OLD RadioShack Charger specs, eh?
  .
• I looked and looked but couldn't find the DISCHARGE CURRENT. Only that the Discharge Function stops @ 0.9VDC.
  .
• Although I only use it for my C and D cells, I think I'll add my RadioShack 23-428 Universal Ni-Cd/Ni-MH Battery Charger to my "Termination Testing" experiment. :wave:

Tandy has always had great support of their products. The termination test is complicated by the use of paired batteries which will have their negative delta-V at different times despite the doubling of the termination signal. I've made shorting plugs on my earlier generation model of your charger that effectively make the unit a independent channel charger...not sure if this will work on your unit. Be interesting to see the results of your termination tests.

PeAK

 

[TakeTheActive]

Re: "timed chargers": Do we all need one ?

Tandy has always had great support of their products...

And the LINK to their Legacy Chargers (RadioShack Legacy Product Support (prior to 2006) / Battery Chargers - Index Page) is in my Sig Line LINKs.

...I've made shorting plugs on my earlier generation model of your charger that effectively make the unit a independent channel charger...not sure if this will work on your unit...

Mine is currently a 4 channel charger - does your 'fix' make it into an 8 channel charger?!? :thinking:

...Be interesting to see the results of your termination tests.

At this point in time, I don't recall if I tried to charge 1 AA cell, or 2, in 1 channel (since I only did it once). But, I DO remember that I was IMPRESSED by the fact that it terminated properly and the cell(s) remained cool. :thumbsup:

 

[PeAK]

Re: "timed chargers": Do we all need one ?

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...I've made shorting plugs on my earlier generation model of your charger that effectively make the unit a independent channel charger...not sure if this will work on your unit...

Mine is currently a 4 channel charger - does your 'fix' make it into an 8 channel charger?!? :thinking:

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Each of the 4 pairs of AA charging channels requires two batteries to complete the circuit. This may not work on your charger, but I replaced one of the batteries with a machine screw (to act as a dummy battery) .

You'll need to do some short duration testing (i.e. watermark) to make sure the batteries terminate with the reduced voltage offered to the charging circuit.
If you have positive results, I may hunt down one of those old chargers for myself.

 

[baterija]

My simple answer is no based on the fact that I don't see a use for one. The cost-benefit ratio isn't there for me. Just right up front the timer is a monetary cost. Since some roles couldn't be effectively fulfilled by this method (like topping up after limited usage) I would still keep a smart charger. Adding the timer and the energizer charger cost we're to $33. Even at 3 dollars a cell the investment would have to save 11 cells simply to break even on the dollars invested.

Along the way this method also introduces:
- risks of cell damage from over discharging
- time and hassle factor managing cells and the extra discharge prep step
- guaranteed overcharge if get the time wrong, whether by accident (ooops I set my Eneloops to the time for the non LSD cells) or because cell aging means you should have reduced the charge time and didn't

If time has no value, or the time spent fiddling with batteries is enjoyable (and thus counts as a benefit) this might break even in a cost-benefit decision. For me it using this charging method would be "pennywise and pound foolish."

 

[PeAK]

My simple answer is no based on the fact that I don't see a use for one. The cost-benefit ratio isn't there for me.
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...Along the way this method also introduces:
- risks of cell damage from over discharging
- time and hassle factor managing cells and the extra discharge prep step
- guaranteed overcharge if get the time wrong, whether by accident (ooops I set my Eneloops to the time for the non LSD cells) or because cell aging means you should have reduced the charge time and didn't
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...For me it using this charging method would be "pennywise and pound foolish."

Good points and this is coming from one with a smart charger that pumps at a 0.5C rate with LSD cells. I have some old cells that never terminate "smartly" and it is usually the backup overtemp circuit that cuts the charge. Your post has clarified one point, though. Many smart chargers do not include the "discharge" or forming options available in the high-end $50+ chargers.

If you add on this low current timed charger to your arsenal, you get essentially the same function. The DIY discharge components provide added functionality but the added time element could be small if they were used to ensure that depleted batteries were further discharged to the 0.9V level.

For me, I already have the timer and the Simple Engergizer Charger still seems an attractive buy. However, for someone buying a well implemented "smart charger" and fresh LSD cells, I would agree with you. As the years go by and the batteries begin to be less well behaved, I think the simple timed charger has its place in extending the life of these batteries.