The remarkable Sanyo MQN05 charger

[Mr Happy]

This charger is rather interesting. Labeled and sold specifically for use with eneloops, it charges 1-4 AA cells at 300 mA with individual channels and smart termination. What makes it interesting is that 300 mA is a very low charge rate for a smart charger.

I have recently been testing it by charging pairs of fully discharged eneloops. It consistently finishes the charge after about 7 hours, which would correspond to 7 x 300 mA = 2100 mAh. This is about what would be expected for a 2000 mAh cell without overcharging it.

Since 300 mA is such a low rate of 0.15C, the question is how does it achieve this clever feat of finishing the charge so accurately, when normally a rate of 0.5C or greater is advised for reliable termination?

One clue is the advice in the user manual that you are supposed to close the cover and plug it into a wall outlet the right way up. It says if you plug it in upside down the charge will finish at the wrong time. I think therefore it must use some kind of temperature detection. When the batteries are fully charged they start to get warm and this is a reliable indication of when to stop charging even at low charge rates.

Whatever magic it contains, this certainly is a neat, tidy and compact charger. It is a shame it is hard to obtain these days.

 

[bcwang]

One clue is the advice in the user manual that you are supposed to close the cover and plug it into a wall outlet the right way up. It says if you plug it in upside down the charge will finish at the wrong time. I think therefore it must use some kind of temperature detection.

Oops, it says that in the manual? I always charge with the cover off and the charger laying flat on top of a surge protector so all the batteries are horizontal.

 

[jchoo]

Neat, it probably has a thermistor on the board. I use a Sanyo MDU-01 USB charger. It is smart, and has two independent channels and can charge a single AA/AAA at up to 850ma or two at up to 450ma. I could not be happier with it, especially since I got it and two AA eneloops for around $12 from Amazon.

 

[Mr Happy]

Oops, it says that in the manual? I always charge with the cover off and the charger laying flat on top of a surge protector so all the batteries are horizontal.

Yes, indeed it does. The description and the pictures in the manual say to close the cover and place it vertically on a wall, and not to put it upside down or it will finish charging too soon.

 

[TakeTheActive]

Re: The remarkable Sanyo MQN05 (*AND* MQN06) charger

...Since 300 mA is such a low rate of 0.15C, the question is how does it achieve this clever feat of finishing the charge so accurately, when normally a rate of 0.5C or greater is advised for reliable termination?

...The initial question that I had with this charger was "How do they reliably terminate the charge at the slow charge rates used?"

The answer is two fold. First they terminate on a maximum voltage. Second they have a back up timer termination...

...One clue is the advice in the user manual that you are supposed to close the cover and plug it into a wall outlet the right way up. It says if you plug it in upside down the charge will finish at the wrong time. I think therefore it must use some kind of temperature detection. When the batteries are fully charged they start to get warm and this is a reliable indication of when to stop charging even at low charge rates...

Does anyone have any photos (or LINKs to) of the insides of the Sanyo MQN05 (and MQN06)?

Handlobraesing originally posted some on PhotoBucket in 2008 when he partially reverse engineered this sucker but they're gone.

I have partially reverse engineered this sucker...

...Thermal

Possible explanation for the claimed "premature termination" with inverted is the heat from the charging circuitry rising by convection and setting off the thermal termination prematurely.

An interesting experiment would be to place a fully charged cell in slot 1 and empty cell in slot 2, leave slot 3 empty then an empty cell in slot 4.

Compare the discharge capacity of the empty cell charged in slot 2 and the one from slot 4. If the cell from slot 2 has much less charge, it would indicate that the heating of charging a already charged cell in slot 1 adversely caused the slot 2 to shut down...

...Component side (click photo to expand)
The orange glass body diode like things are thermistors and blue resistors are ~0.1ohm shunts.
There are two thermistors, each serving two bays. They fit into the slits placed between two cells in the housing shell...


...note the two channels between 1&2 and 3&4 for thermistors

Egsise posted some great photos of the MQH02 in Sanyo MQH02 4AA/2AAA charger :thumbsup: that clearly show three thermistors located near the negative terminals (TH201-203). Thus, the idea of plugging these chargers in "Right-Side Up" to keep the heat away from the thermistors seems to be a common thread.

...I have recently been testing it by charging pairs of fully discharged eneloops. It consistently finishes the charge after about 7 hours, which would correspond to 7 x 300 mA = 2100 mAh. This is about what would be expected for a 2000 mAh cell without overcharging it...

I got curious and charged my first set of cells (4 'Brand-New' Eneloops - purchased 05/09) on my 'Brand-New' MQN06 (also purchased 05/09 - Costco deal). [I discharged them first @ 0.2C in my C9000.] I noted that within the first hour, the entire MQN06 charger top and 4 cells were warm (~100°F by touch). When I remembered to check them ~7.5 hours later, cells 1&2 where done and cool while cells 3&4 were still charging and 'warmer' (~110°F by touch). ~9 hours later, cells 3&4 were also done and now cool. ~24 hours later, *EVERYTHING* was cool confirming, for me, no 'Trickle Charge' and most probably only a 'Maintenance Charge'.

...Well, today I tested it using an ammeter. I put one AAA Eneloop in the charger. During charge, the charger pulsed the battery with 610 mA for about a 1/4 second, then rested for 3/4 seconds, then pulsed again, rested, etc. Averaged out, this correlates with the 150 mA charge rated listed on the back of the charger for AAA's.

When the charger light extinguished, the charger pulsed the battery with anywhere from 10 to 40 mA for about a 1/4 second, then rested for 8 seconds, then repeated. It continued this cycle for one minute, then rested for a full minute. It then pulsed again as before for another minute, then rested a minute. This cycle repeated for as long as I had the battery in place. I took it out after about 20 minutes. I'm not sure one would call this a trickle charge, maybe more of a "maintenance" charge. Pretty cool, nonetheless.

All 4 'Brand-New' Eneloops are currently discharging @ 0.2C in the C9000.

While I personally wouldn't want the MQN06 as my *ONLY* charger, my first impression of it is that it's not as bad as I originally thought from reading various reviews. I'm charging some High Resistance *CRAP* cells in it right now to see how well the thermistors (*IF* the MQN06 has them!) work.

 

[Bones]

Yes, indeed it does. The description and the pictures in the manual say to close the cover and place it vertically on a wall, and not to put it upside down or it will finish charging too soon.

Ergo:

http://rapidshare.com ... sanyo.eneloop.nc-mqn05.manual.pdf.html
-

 

[flasherByNight]

How about posting where these can still be found?
:huh:

 

[Mr Happy]

How about posting where these can still be found?

I don't know, to be honest. I got mine a long, long time ago in a close-out sale at Wal-Mart. They don't have them any more.

You could take a gander at this thread: it seems that davidt1 managed to locate an on-line vendor who still has some. You have to check with the seller before buying though because it is easy to get the different MQN06 instead.

 

[Radiophile]

Whatever magic it contains, this certainly is a neat, tidy and compact charger.

Handlobraesing posted the magic here:

http://www.candlepowerforums.com/vb/showpost.php?p=2511280&postcount=65

I have partially reverse engineered this sucker.

The AC power is stepped down to 2.2v DC by a switch-mode power supply. The battery side and AC side is galvanically isolated and power transfer is magnetic and feedback is through an optocopupler, just like most other SMPSs.

It employs a single current source sequential charging topology.
The current source is 0.6A for AA and 1.2A for AAA and each operates at 25% duty cycle and each slot receives a time weighed average of 0.15A or 0.3A.

It takes two seconds to progress through all 4 cells, so the frequency is 0.5 Hz and each cell receive 0.5s on/1.5s rest.


There are two benefits with this design. The electrochemical efficiency of battery is higher at 1.2A than 0.3A. Given a 2,000mAh cell, you need to charge at true 300mA(0.15*It) for 16 hours to fully charge, however when you charge at 1.2A(0.6*It ) the charge efficiency during the 25% charging duration is more efficient, so even though the time weighed average current is the same, you will actually achieve a full charger sooner.

In other words, the energy pushed into the battery during the two second period is the same, but the total energy stored by the battery at 1.2A for 0.5second is more than that of 0.3A x 2 seconds.

Another benefit is that you only need one constant current circuit.
quadrant 1 =cell 1, quadrant 2 is cell2, etc. The constant current source provides current the entire time when all quadrants are loaded, but when there is no cell in one of the bays, it simply pauses for half a second and move onto the next one.

This is topology is quite common with Sanyo chargers and with some of their chargers, you can actually charge 2 cells at faster rate. This is made possible by allocating two quadrants to each cell.

So what I get from this is that the charge rate is actually 1.2A per AA cell or .6A per AAA cell, but it's pulsed at a 25% duration per cell. Sweet.

 

[davidt1]

I don't know, to be honest. I got mine a long, long time ago in a close-out sale at Wal-Mart. They don't have them any more.

You could take a gander at this thread: it seems that davidt1 managed to locate an on-line vendor who still has some. You have to check with the seller before buying though because it is easy to get the different MQN06 instead.

I bought one from that vendor on Monday and received it today. Mr. Bones deserves credit for locating this vendor. He even posted the link for the English manual.

 

[viorel00]

it is an EXCELLENT charger, it will detect bad cells (light flashes). I put Alkaline in it, very old NiMH cells, it always detects something is wrong and it will not charge bad cells.

higher resolution photos here

http://www.flickr.com/photos/11974821@N00/

 

[elwood]

I have had my eneloops with this charger for over a year. I probably have over 20 AA's and 6 AAA's. First thing I did was remove the cover and threw it in a drawer somewhere. I've never charged with the door on. Oops! Guess I should find it and start using it!

 

[Bones]

I have had my eneloops with this charger for over a year. I probably have over 20 AA's and 6 AAA's. First thing I did was remove the cover and threw it in a drawer somewhere. I've never charged with the door on. Oops! Guess I should find it and start using it!

Interesting, I wonder if you'll notice improved run-times since your cells should now absorb a more complete charge?

 

[elwood]

Interesting, I wonder if you'll notice improved run-times since your cells should now absorb a more complete charge?

I don't know but I'll soon be getting a maha or La crosse charger as my AA flashlight collection grows.

 

[bob_ninja]

I have MQN06. I assume the differences between 5 and 6 are minor/cosmetic (such as additional indicator light) and 6 has only 2 channels. However the hardware inside (I am guessing) is generally the same. According to the Handlobraesing'sdescription from bellow, MQN06 would be using 50% cycle for each channel (x2) as opposed to 25% (x4) for MQN05. Any thoughts?

BTW I actually inserted old NiCd AAs and they seem to charge and terminate fine. For them being in the 600-800 mAh range, 300 mA is actually around 0.5C rate I'll charge them on BC900 next time to see how out of balance they are.

For NiMH I only use it for Eneloops and haven't tried other types yet. I would charge them using MQN06 for a few times (quick and convenient, often in garage) then bring them inside to charge on BC or Maha smart charger. That way they don't become too unbalanced.

 

[elwood]

I have MQN06. I assume the differences between 5 and 6 are minor/cosmetic (such as additional indicator light) and 6 has only 2 channels. However the hardware inside (I am guessing) is generally the same. According to the Handlobraesing'sdescription from bellow, MQN06 would be using 50% cycle for each channel (x2) as opposed to 25% (x4) for MQN05. Any thoughts?

BTW I actually inserted old NiCd AAs and they seem to charge and terminate fine. For them being in the 600-800 mAh range, 300 mA is actually around 0.5C rate I'll charge them on BC900 next time to see how out of balance they are.

For NiMH I only use it for Eneloops and haven't tried other types yet. I would charge them using MQN06 for a few times (quick and convenient, often in garage) then bring them inside to charge on BC or Maha smart charger. That way they don't become too unbalanced.

5 has four independent channels (can charge 1-4 batteries). 6 i think you have to charge batteries in pairs.

I'm not completely sure but i am completely sure that someone will correct me if i'm wrong.

 

[bob_ninja]

5 has four independent channels (can charge 1-4 batteries). 6 i think you have to charge batteries in pairs.

I'm not completely sure but i am completely sure that someone will correct me if i'm wrong.

Yes, you are right about 2 channels. I meant that the rest of the hardware would be more or less the same; just guessing.

 

[davidt1]

I always charge 2 freshly charged batteries in a new charger to test its smartness. A smart charger would be able to detect the amount of charge in the batteries and charge them accordingly -- usually in a very short time. A timer-based charger, I imagine, would charge until the timer goes off.

About the MQN05, is temperature sensing the best way to charge? Wouldn't sensing the amount of voltage/current in the battery be a better way? According to the manual, high room temperature can cause problem with charging. That just doesn't make sense to me. What does room temperature have anything to do with the internal of the battery?

 

[Mr Happy]

About the MQN05, is temperature sensing the best way to charge? Wouldn't sensing the amount of voltage/current in the battery be a better way? According to the manual, high room temperature can cause problem with charging. That just doesn't make sense to me. What does room temperature have anything to do with the internal of the battery?

Temperature sensing is absolutely the best way to charge NiMH cells, assuming you can accurately and consistently measure the temperature. The reason is the energy balance around a charging cell:

Input − Output = Accumulation

While the cell is not full and still charging the energy being fed into the cell (Input) is mostly stored inside the cell as Accumulation, so wasted energy (Output) is low and the cell does not heat up very fast. But once the cell is fully charged it can't accumulate any more energy and so Accumulation becomes zero. As a result all the Input becomes Output, and the only way out is heat. Once this happens the cell starts warming up really fast. Chargers can detect this transition to rapid warming and stop the charge as soon as it happens.

Because the above equation is based on fundamental thermodynamics and is always true, for all cells, all the time, it is the most reliable way of detecting when to stop charging. It still can be fooled, as someone may be quick to point out, but even so it is better in theory than other ways. (It may not be better in practice, but it is still good when combined with other measurements.)

 

[wapkil]

Temperature sensing is absolutely the best way to charge NiMH cells, assuming you can accurately and consistently measure the temperature. The reason is the energy balance around a charging cell:

Input − Output = Accumulation

While the cell is not full and still charging the energy being fed into the cell (Input) is mostly stored inside the cell as Accumulation, so wasted energy (Output) is low and the cell does not heat up very fast. But once the cell is fully charged it can't accumulate any more energy and so Accumulation becomes zero. As a result all the Input becomes Output, and the only way out is heat. Once this happens the cell starts warming up really fast. Chargers can detect this transition to rapid warming and stop the charge as soon as it happens.

Because the above equation is based on fundamental thermodynamics and is always true, for all cells, all the time, it is the most reliable way of detecting when to stop charging.

I don't want to be nitpicking but I think it is more complicated. What you write is true for NiMHs and many other chemistries but I believe it is not based on thermodynamics and it is not true in general.

Charging causes (electro)chemical reactions that can be exothermic but can also be endothermic. It is not true that the only way to waste the energy is to produce heat, it may be also wasted in some endothermic reactions during overcharging. I don't know a chemistry in which overcharging would be endothermic but it may exist. No general laws of physics prevent it - it would only mean than during overcharge more heat is consumed in endothermic reactions than is otherwise produced.