Author Topic: Alkaline battery charger  (Read 322 times)

0 Members and 1 Guest are viewing this topic.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2268
Alkaline battery charger
« on: November 07, 2012, 09:58:41 AM »
I bought an "AlkaCharger" new off eBay this week. I've been using NIMH/NiCad chargers to boost used carbon-zinc and alkaline batteries for reuse and decided to try one of the few battery chargers on the market that is actually designed to recharge single-use batteries.

http://www.ebay.com/itm/Alkacharger-Battery-Charger-charges-regular-batteries-/170660939709 This seller.

The AlkaCharger http://www.inventist.com/alkacharger/ uses a "12vac" wall wart for a power supply. Since I'm trying to stay off grid, I figured it might run on off 12vdc. Before trying that I opened up the bottom and saw it used a 78M05 rectifier behind the plug port. I was expecting to see a full-wave bridge, not a triac.

I had a 12v car adapter to male mini cable that fit the Alkacharger's port, but when I plugged it into 12vdc center pin positive, nothing happened. Cut and splice the wires around so center pin is negative worked, though. I don't know why they use an a/c power supply and only take half-wave from it, but they do. The wall adapter even has their name printed on it.

The board inside has lots of surface mount resistors. The trick to recharging alkalines is to avoid raising the voltage high enough to generate gas and burst the cell. I have a USB powered charger that blows open AA's if left in too long.

The Alkacharger has a test lead inside and a triplet of red-yellow-green LEDs that are supposed to test to see if a battery is charged. That flat out DOES NOT WORK. Dead D cells showed green. You will need a proper volt meter to check your cells before reuse.

The body is cast plastic and it's hard to close with 9v batteries inside. The shell should have been made better. The electronics inside are impressive, but it looks cheap because the maker cut corners on the case.

Bruce S

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 4587
  • Country: us
  • USA
Re: Alkaline battery charger
« Reply #1 on: November 07, 2012, 11:59:04 AM »
interesting;
Have you had it long enough to really test it out?
How long before it's paid for itself?
Bruce S
A kind word often goes unsaid BUT never goes unheard

dnix71

  • SuperHero Member
  • ******
  • Posts: 2268
Re: Alkaline battery charger
« Reply #2 on: November 07, 2012, 12:50:54 PM »
I get Chinese D cells "Wincell" from work for free when they won't run the air fresheners in the restrooms. Just in the last 4 hours or so since I loaded it, those have all come up the the same voltage, about 1.28 from less than 1.25 and the bottom of the charger is warm.

It's supposed to take a week to fully recharge, which sounds right.

The reason alkaline batteries don't recharge well is the reaction products diffuse through the cell during discharge. It takes at least as long to diffuse back under a charge. I got a bunch of 9v for free from church before I bought them 9.6v NiMH batteries for the cordless microphones. D cells and 9v batteries are $2 for the cheap ones in quantity.

The used 9v go in my Harbor Freight $3 multimeters, the D cells go in my geiger counters and the AA's go in my camera, which eats batteries. The Canon SX120 IS is flaky about batteries. It will refuse new ones and then accept them for no apparent reason. Radio Shacks house brand AA's suck. Their Enercells work much better. Both recharge and reuse fine.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2268
Re: Alkaline battery charger
« Reply #3 on: December 02, 2012, 02:26:14 PM »
Here are pix of 3 battery chargers I bought that run directly from 12vdc.





The Viatek on the right and the Alkacharger on the left are advertised as being able to recharge alkaline batteries. The Radio Shack Enercell charger in the middle is not and will flash an error code if your try, but it does seem to charge anyway if you ignore the warning.

The Viatek is junk manufacturing. The 9-volt port broke almost the first time it was used and the lid hinges didn't last much longer. But the Viatek actually recharges alkalines and does so quickly. I do not intend to return the Viatek for a replacement because the construction is so poor a replacement won't last any longer. The 9-volt port is riveted to 1/16" cheap plastic. To repair the crack I used 2 part epoxy and then back-stopped the port underneath with 2 layers of double-sided foam tape. That properly secures the top half of the shell to the bottom and eliminates the space between the two which contributed to the break.

The Viatek isn't consistent about what it considers a full battery if you measure voltage. It may be checking internal resistance.
The batteries I wanted recharged are the Chinese made D-cells in the picture. Those came with touch-less paper towel dispensers and were used up to 6 months until the voltage was about 1.25. That those recharge at all and do not leak amazes me. The Viatek needs a cold boot to restart after a full cycle. Power disconnect, remove batteries, repeat. Simply using the on-off button doesn't do it.

Another major weakness of the Viatek is it requires two strong fingers or a flat tool to insert D-cells. The return springs are too stiff and there is no spare room to push back the negative contact to get a D-cell in.

There is a wall wart version of the Viatek that charges AA, AAA and 9-volt cells, but I gave that to my father because I want only direct 12v appliances.

The Radio Shack Enercell is the only one of the three with a USB charging port.

The Alkacharger trickle charges and will not raise the voltage as high as the Viatek. The D-cells that were 1.24v never went about 1.37 when left in the Alkacharger, but it took more than one recharge cycle in the Viatek to make the higher voltages stick. The Alkacharger is also powered with a negative pin/positive shell plug unlike most appliances that use external adapters. That meant I had to make a dedicated adapter cord for it. The diode behind the power port got hot enough to discolor the wafer board, and now doesn't even get warm, so it's probably burned out, but the charger still seems to work.

The open voltage of the Alkacharger is 1.61 and 9.09. Both of those are safe for AA-AAA and "9v" batteries, respectively. The real resting voltage on a AA, AAA, C or D is somewhere between 1.55 and 1.65 depending on the maker and freshness.

The Alkacharger does a lot of cell at once, but it takes days to recharge even NiMH or NiCads. The Alakcharger has battery management chips that allow you recharged batteries to float indefinitely. If it takes a week, you can leave it plugged in that long. The Viatek has an on-off buttom, but the Alkacharger's switch is built into the lid.

The major design flaw of the Alkacharger is that leaking batteries drip right down on the electronics. There is a hole with a spring contact under each cell. I had a AA cell leak the first week I used it and had to disassemble the charger and clean it up to prevent permanent damage. The only safe way to use the Alkacharger is sideways. That way leaks are contained in the cell tube.
« Last Edit: December 02, 2012, 02:31:09 PM by dnix71 »

hydrosun

  • Sr. Member
  • ****
  • Posts: 398
Re: Alkaline battery charger
« Reply #4 on: December 02, 2012, 07:15:28 PM »
Ive had something similar for 20 years. It charges an alkaline battery  from about 50 % to 75% the first time and less each time. So it extends battery life but probably less than double total.
Chris

taylorp035

  • Hero Member
  • *****
  • Posts: 1009
  • Country: us
  • Stressed spelled backwards is Desserts
Re: Alkaline battery charger
« Reply #5 on: December 02, 2012, 08:15:08 PM »
I own a Rayovac Renewal Power Station like this:

http://www.americasprice.com/Rayovac-Renewal-Power-Station-PS2.htm

I've had it now for ~17 years now and it works really well with the Renewal brand rechargeable Alkaline batteries.  It pumps out 500 mA at each of the 8 slots, which can hold AAA through D cells.  At one point, I had about 8 C cells and ~30 AA's, which worked well in all my toys for about 10 years.  Eventually they just won't accept a charge.  For the longest time, I would charge my nicd's in it too and they would always get hot.... 500 mA into a 300 mAh AA nicd was definitely too much.  You could double stack the cells too if you wanted to fit 16 batteries.  The charger would only shut off after it hit ~1.6-1.7v, so the Nicd obviously never finished  :P

I've charged regular non-rechargeable Alkaline batteries in it too with mixed results.  Some energizer cells seem to have worked for a few cycles.  I almost prefer the charger at times to my cheap 4 cell Nicd/Nimh charger since it stops charging after a minute half the time and sometimes it doesn't pick up on the gentle voltage peak of the 2500 mah Nimh, so it will continue charging at 500 mah.  It does seem to have an over temp cutoff, but it's set higher than I would like.  The 500 mah is also too much in my opinion for the 700 mah AAA's.