Best rechargeable "D" cell

[JudasD]

uh, oh: an earlier CPF thread:
http://www.candlepowerforums.com/vb/...=1#post3561799
"Maha MH-C808M Charger Melted! What Now??
When I was researching this charger, I found two reviews about it catching on fire..."
One of them with Tenergy 10,000 NiMH D cells.

Of course there's always going to be one or two problems out of tens of thousands.

Those reports are from over a year ago. Chances are maha has made some changes since then.

JD

[hank]

> Maha MH-C808M
I don't find mention of changes at Maha; I've emailed to ask. It's a switched-mode power supply built in the case, not a wall wart, so overheating could be typical failure -- Wikipedia says what I've read elsewhere, that "switching adapters are more likely to fail than the older type" and mentions a variety of ways it happens.
So it goes; rare anyhow. If I hear anything from Maha I'll mention it, but I'll put it in a charger topic so not to get further off track here.

Meanwhile, on topic -- I just got my eight Tenergy 10,000A D cells (blue with the big lower case "e").

Checked the first four as they came out of the shrinkwrap,
about 0.2, 0.2, 0.4, and 1.0v showing. I've got a CCrane charger that handles D size, I'm using it on the first four. Will follow up.

[CyberCT]

Just got my 16 in the mail today. They are the same blue 10,000 mah with the lowecase "e" as you hank. With my voltmeter the lowest was 0.92 and the highest was 1.08. I also got my Maha MH-C808M in the mail today so I have 8 charging in "soft mode" which is 1 amp rate, which Tenergy recommends.

Are you sure they read that low? I didn't think alkalines could output that low of a voltage. What I found interesting is that there was no batch that was really different that the other. Of the 4 x 4 packaged cells, each pack had 1 or 2 over a volt and 2 or 3 that were under. I was expecting to see one package have all over 1 volt and another package to have all under a volt.

[CyberCT]

I just checked the charging and both batteries and charger are cold to the touch (my basement is probably 65ish degrees year round). All batteries right now have 2 of the 3 bars visible and flashing. When I inserted all the batteries at first, only 1 of the 8 had 0 of 3 bars visible. The other 6 had 1 bar and 1 even started charging with 2 bars.

[hank]

Those first numbers came from the CCrane's battery analyzer mode.
On the other hand, it's already telling me it's up to trickle charge mode
-- way less time than I'd expect if the cells were that low. So, maybe that analyzer voltage was low.

I don't see how I could've messed up measuring it, it's just put in one cell and push the button.
But I've screwed up simpler tasks on occasion.

While that's charging those four, I've now checked the second four right out of the shrinkwrap with one cheap multimeter -- three at about 0.9 and one at 0.7, plus or minus a hundredth.
So that's better. I've double checked with my other cheap multimeter and got consistent numbers; it runs about 0.1 lower but that was consistent across all four.

Once the CCrane is finished with the first four, I'll see what how it reads the second four.
Could well be that measure is running low, I don't think I ever checked its accuracy on that mode.

---- EDIT -- ok, the CCrane showed it finished charging (it has one indicator for all four, and to be fair does say it's best if all the cells are at about the same starting level).
Using the CCrane's Analyze function then, the three cells that had started at 0.2-0.4v originally show as 1.35 or 1.37v, all five bars.
And a cheap multimeter shows them as 1.36, 1.36, 1.35v.

The one cell that had been 1.0 originally now shows as 3 of 5 bars and about 1.2v. So I'm putting it back on charge and will see if it comes up.

[chewy78]

i got 12 of those blue10,000 tenergys off ebay and measured from .88- .91 volts on mine. I have 6 of the ones with the highest voltage reading with my sears dmm charging at one amp on my maha charger to use for a portable radio.

[hank]

Second shrinkwrapped batch of four Ds -- which showed three at about 0.9 and one at about 0.7 on the multimeter -- tested on the CCrane 'Analyze' function at much less, 0.14, 0.17, 0.17, and 0.34. So something's odd there. This time I'll try charging just two at a time on the CCrane, having belatedly found the note at their website saying the charger (500ma 12v power supply) may not handle four at a time for high rated large cells.

Oddity -- holding these D cells with the multimeter probes, the voltage shown slowly and steadily increases over time. Do the batteries "wake up" when first tested?

[CyberCT]

How long did it take you to charge them? Mine have been charging for almost 5 hours and might be up to the 3rd of 3 bars now on my charger. But I haven't checked it in 40 minutes.

[chewy78]

My first 12 d tenergy d cells i ordered of off ebay for 24.99 are charging nicely in my maha 808. I also ordered another 8 tenergys off ebay. Right now i think they are the best battery for the money/ bang for the buck.

[357mag1]

My 16 cells all showed between just below .8v to just over 1v right out of the shrink wrap.

[hank]

Charging just two in the CCrane took a couple of hours -- up to 1.37 and 1.38v. So I suspect it terminated early when I was trying four at a time. I'll check them again tomorrow.
Good enough to convince me to buy more of these cells while they're available.

Then I'll want a better charger ....

[357mag1]

How long did it take you to charge them? Mine have been charging for almost 5 hours and might be up to the 3rd of 3 bars now on my charger. But I haven't checked it in 40 minutes.

Soft charge mode is 1amp per hour so you are looking at around 8 hours.

[CyberCT]

Soft charge mode is 1amp per hour so you are looking at around 8 hours.

Yes, that's what I figured. I went to bed and the charging was 5.5 hours in. They were all charged when I woke up this morning. I put the second set of 8 on the charger. Hopefully they should be charged when I come home and my TK70 will be at the doorstep! I'll have to rig up my D cell to AA cell setup to use the C9000 to do a "discharge" test of each battery and start getting their mah numbers so I can match my D cells like I have with my AAAs and AAs.

[jayflash]

Charging just two in the CCrane took a couple of hours -- up to 1.37 and 1.38v. So I suspect it terminated early when I was trying four at a time. I'll check them again tomorrow.
Good enough to convince me to buy more of these cells while they're available.

Then I'll want a better charger ....

Hank, if your CCrane is like mine, it share total charging current between all bays. One cell should charge at about 1.5 amps and each additional cell will evenly divide that -- unless our chargers operate differently. The same is true for the discharge or analyze function. To obtain the slowest discharge rate, put in four cells. To get the highest charge rate, do the opposite and install only one cell.

It seems that your cells need several charge/slow discharge cycles, because your charge time is way too fast.

[hank]

Thanks Jayflash -- I've got a quite old CCrane (repaired the springs after they failed a while back); not sure if the newer ones are any different about charging.

The manual for it does mention needing several cycles. I'm on my first cycle for these batteries, so expect them to shape up after a few cycles.

[357mag1]

Yes, that's what I figured. I went to bed and the charging was 5.5 hours in. They were all charged when I woke up this morning. I put the second set of 8 on the charger. Hopefully they should be charged when I come home and my TK70 will be at the doorstep! I'll have to rig up my D cell to AA cell setup to use the C9000 to do a "discharge" test of each battery and start getting their mah numbers so I can match my D cells like I have with my AAAs and AAs.

After doing all of my discharge tests multiple times to make sure my broken MD-3000 wasn't causing any erroneous readings I have four of the Tenergy Blue batteries staying just below 7000mah and one more hovering around 6000mah. These are all in the Maha 808 going through a conditioning cycle to see if they will come up any. All of them have been through at least 4 or 5 charge/discharge cycles so I don't expect to see much if any improvement.

These batteries would be fairly rated at around 7500mah as that seems to be about the median for 16 of them. Guess that is why they came out with the Premium replacement. The good news is they seem to hold their voltage just as well as the Premiums under load. I would take these over the garbage AccuEvolution cells any day.

Just to keep in in perspective the Tenergy Premium batteries I own vary in capacity readings from around 9000mah to about 10,400mah. Chinese batteries always seem to have a larger variance. If we could get a Japanese company or "Quality" American company to develope some D Nimh cells we would have some killer Deeees!!!

[CyberCT]

After doing all of my discharge tests multiple times to make sure my broken MD-3000 wasn't causing any erroneous readings I have four of the Tenergy Blue batteries staying just below 7000mah and one more hovering around 6000mah. These are all in the Maha 808 going through a conditioning cycle to see if they will come up any. All of them have been through at least 4 or 5 charge/discharge cycles so I don't expect to see much if any improvement.

These batteries would be fairly rated at around 7500mah as that seems to be about the median for 16 of them. Guess that is why they came out with the Premium replacement. The good news is they seem to hold their voltage just as well as the Premiums under load. I would take these over the garbage AccuEvolution cells any day.

Just to keep in in perspective the Tenergy Premium batteries I own vary in capacity readings from around 9000mah to about 10,400mah. Chinese batteries always seem to have a larger variance. If we could get a Japanese company or "Quality" American company to develope some D Nimh cells we would have some killer Deeees!!!

Man, that is disappointing! At first I was expecting 10,000 mah as advertised. Then read on here that realistically they are more like 8,000 which is not toooo bad. But anything below that, well now that's crap. My modded Rayovac lanterns take D cells but I have been using the AA to D cell adapters. At 1.4a on the highest mode for an XML, the higher capacity cells would clearly win here, which is what I initially wanted - runtime.

I bought some stuff to make adapters for my D cells to fit into my Maha MHC9000. SO hopefully I'll have it rigged up tonight. What should I do to test the mah values of mine? Just stick them in and discharge at 1 amp for each cell? it would take about 8 hours I presume.

[357mag1]

I would say you are looking at approximately 8 hours to discharge a cell.

Remember my tests are at 3 and 5amps to more closely simulate how I use these batteries.

At about $3.13 a cell shipped to our door I'm still pretty happy. You have to figure at that price they must have been old stock that had sat around for quite some time.

I paid a whole lot more for my AccuEvolution cells and they made my incadescent light (ROP HI) look sick. The cells were not even usable for the application. These Tenergy Blue cells run it as bright as any cell I've used and do it for over 1hr 35mins.

These Blue cells will run my newer TK70 on Turbo using 3 cells the AccuEvolutions sag so bad it drops to high in about 23 seconds.

[CyberCT]

Two of the cells are still "soft" charging on my Maha. They have been charging for 13 hours now. I went to home depot and bought a wooden dowel that was the closest size to an aa battery to make an adapter for my C9000. THe dowell was a little too thick and I finally got irritated after my 3rd try to make it fit in there with my copper wires that I gave up. I'll have to figure out another way to get an adapter to work so I can start doing battery matching with the Tenergys.

EDIT: The last two cells took about 13.5 hours to charge. I took them off the charger. With my volt meter I quickly checked these 8 that just came off the Maha, and the 8 that came off yesterday. The range of the 8 charged today was 1.39 to 1.42. Yesterdays was 1.35 to 1.4.

Amazon has multiple reviews of these batteries, and I forget where the link is but these were tested with other D batteries and the capactiy came up as a smuge under 8,000 mah. The Amazon reviews seem to be both good and bad, with the worse reviews being most recent. No doubt QA/QC has sunk, but there seem to be good and bad batches of these batteries.

http://www.rechargeable-battery-revi...rformance.html

I ended up buying a pack of those AAA to AA adapters so I will simply wire them up as a dummy cell to my D cell holders that I will have to modify (from series to individual) from Radioshack so I can do discharge tests. I have a feeling that cell matching with these batteries is an absolute must.

I'm not sure the maximum discharge capability of the C9000 but I'll have to check. I could do multiple tests per battery 1 amp, then 2 amp, then 3 amp if it's available. This would probably take a while to do but meh. I bought the TK70 for snorkeling in the late spring so I won't really be using the TK70 much beforehand.

[drmalenko]

I have purchased 36 of the batteries from ebay, all of them came out of the shrink wrap between .899 - 1.08v... I started them all of with a charge cycle to wake em up, then cycled them through a 3a discharge and, some at 5a charge, and some at 2a charge.. I have found they all have over 8000mah.. My triton2 charger has actually "mah'ed" out at 9900mah on a couple of charge cycles (most of these were with 8 cells or more in the charge loop) but with 4 cells discharging/ charging at one time I find that 8500-9500mah is the norm with most of them being over 9000mah...

and its already been said once, at just over 3.00 dollars a cell shipped, you really can not complain even a little bit if they are less than 10,000mah... lol

[357mag1]

Two of the cells are still "soft" charging on my Maha. They have been charging for 13 hours now. I went to home depot and bought a wooden dowel that was the closest size to an aa battery to make an adapter for my C9000. THe dowell was a little too thick and I finally got irritated after my 3rd try to make it fit in there with my copper wires that I gave up. I'll have to figure out another way to get an adapter to work so I can start doing battery matching with the Tenergys.

EDIT: The last two cells took about 13.5 hours to charge. I took them off the charger. With my volt meter I quickly checked these 8 that just came off the Maha, and the 8 that came off yesterday. The range of the 8 charged today was 1.39 to 1.42. Yesterdays was 1.35 to 1.4.

Amazon has multiple reviews of these batteries, and I forget where the link is but these were tested with other D batteries and the capactiy came up as a smuge under 8,000 mah. The Amazon reviews seem to be both good and bad, with the worse reviews being most recent. No doubt QA/QC has sunk, but there seem to be good and bad batches of these batteries.

http://www.rechargeable-battery-revi...rformance.html

I ended up buying a pack of those AAA to AA adapters so I will simply wire them up as a dummy cell to my D cell holders that I will have to modify (from series to individual) from Radioshack so I can do discharge tests. I have a feeling that cell matching with these batteries is an absolute must.

I'm not sure the maximum discharge capability of the C9000 but I'll have to check. I could do multiple tests per battery 1 amp, then 2 amp, then 3 amp if it's available. This would probably take a while to do but meh. I bought the TK70 for snorkeling in the late spring so I won't really be using the TK70 much beforehand.

The C9000 is limited to 1amp discharge rate. You can go less in increments of 100ma but not more.

[chewy78]

im gonna have to get some d cell holders and maybe some adapters to test mine. on my c9000

[CyberCT]

The C9000 is limited to 1amp discharge rate. You can go less in increments of 100ma but not more.

357mag1, what battery charger do you have, where you can measure the D cells' mah values from various discharge rates?

[357mag1]

357mag1, what battery charger do you have, where you can measure the D cells' mah values from various discharge rates?

I use hobby chargers to test battery capacity. I have two, one is a Turnigy AccuCell-8 that can discharge at a rate up to 5amps and the other is a Triton2 EQ that is limited to a discharge rate of 3amps. Either unit can charge or discharge Nimh, NiCad, Lithium and Lead Acid single cells or battery packs.

[357mag1]

I have purchased 36 of the batteries from ebay, all of them came out of the shrink wrap between .899 - 1.08v... I started them all of with a charge cycle to wake em up, then cycled them through a 3a discharge and, some at 5a charge, and some at 2a charge.. I have found they all have over 8000mah.. My triton2 charger has actually "mah'ed" out at 9900mah on a couple of charge cycles (most of these were with 8 cells or more in the charge loop) but with 4 cells discharging/ charging at one time I find that 8500-9500mah is the norm with most of them being over 9000mah...

and its already been said once, at just over 3.00 dollars a cell shipped, you really can not complain even a little bit if they are less than 10,000mah... lol

Just because your charger pushed 9900mah to a cell doesn't mean that cell has that capacity. A high quality battery like the Eneloop will have a capacity close to what the charger pushes into it but these cheaper Chinese cells always seem to take more to charge than they deliver in capacity.

As an example I performed some AAA test on the C9000 last night. Eneloop AAAs took around 825mah to fully charge. The Rayovac AAA cells took over 900mah on every cell and some well over that. The Eneloops always show more capacity when discharged than the Rayovacs.

Something to keep in mine.

[CyberCT]

357mag1, I appreciate your feedback and help.

I'm learning, and think I finally have an idea of what's going on here. Confirm I do or correct me where I don't. I'm still learning and have picked up bits & pieces over the last two years but think I got it:

There are different mah values:

1) Charge capacity of a battery is how much charge it can take from the charger in mah, which will usually be the the highest capacity of the battery.

2) Discharge capacity, which is how much mah a battery can produce for a load. That value will be lower than the charge capacity. Now, for the discharge capacity, the discharge capacity mah values can vary depending on the load or rate of discharge. Let's use an eneloop. The charge capacity might be 2,000 mah. Under a .2 amp load, the battery might produce 1,950 mah. Under .5 amp load, the battery might produce 1,850 mah. Under a 1 amp load, the battery might produce 1,700 mah.

3) The amount of voltage a battery can supply under load. A NIMH battery such as an eneloop is rated at 1.2v. now let's say there is a .5 amp load on the battery. If it produces about 1.15v and 1,850 mah that is better than another AA battery that produces, at .5 amps load, 1.05v but say 1,950 mah? I'm still a little confused about this a little.

Would it be safe to say that a battery with a stated capacity that matches closely its discharge capacity is a good quality battery? Like if a D battery can take 10,000 mah from a charger, but as soon as a load of say 1 amp hits the battery it drops to 8,000 mah capacity, that cell isn't as high quality as a cell that is stated at 9,000 mah capacity but produces 9,000 capacity under load?

When you mentioned that your blue Tenergy cells were around 7,000 mah capacity, you were doing a discharge test of each at what, 4 amps? If you did a 1 amp discharge test should you expect a capacity of more like 9,000 mah?

Just curious, what capacity did the Eneloops show on your C9000 vs the Rayovacs, when you did the discharge?
And which of those two chargers you mentioned do you like better?

[hank]

357mag1, can you describe exactly how you're testing D cells with the Turnigy?
I've got an Accucel-6 now and can probably set it up the same way you're doing and compare.
I've only used it with single cells, never with more than one at a time.

I was wondering if the Accucel-6 can handle multiple batteries if set up properly to do effectively the same charge and discharge as the Maha D-cell charger others are using.

[jayflash]

Cyber, maybe a bit more info will be useful. It seems there are trade offs and compromises for most things. Ideally, high capacity, good voltage maintenance under high drain, low self discharge, long cell life, and low price, could all be found in one cell. You might find most of those features, but at a higher or premium price.

Maintaining voltage around 1.25v at loads of ~5 or more amps might be one indication of good quality cells. My AccuEvolution D & C cells are holding their LSD properties after one year and voltage is good, but I only load them to <2 amps. Some 7Ah cells could perform better than other 10Ah cells.

I depend on discharge capacity to more accurately reflect my actual use. Charging capacities may be up to ~30% higher than actual due to, say, only a 70% charging efficiency.

It would be nice if large rechargeable cells had warranties. There's potential to spend hundreds on cells that only last a couple years or drop off in performance in less time.

BTW, my RayOVac Hybrids of four years are all deteriorating. My four year old "Duraloops" have lost only 100mAh or so, and are maintaining good voltage under loads of an amp or less.

[CyberCT]

Hmm. So in 10 years from now, would it be safe to say my rechargeables are pretty much worthless? I understand that over time they degrade, but thought that in at least 6 years from now, they would still perform similarly (by doing a break-in cycle once a year) I don't use the cells as much as I originally intended.

[chewy78]

Cyber, maybe a bit more info will be useful. It seems there are trade offs and compromises for most things. Ideally, high capacity, good voltage maintenance under high drain, low self discharge, long cell life, and low price, could all be found in one cell. You might find most of those features, but at a higher or premium price.

Maintaining voltage around 1.25v at loads of ~5 or more amps might be one indication of good quality cells. My AccuEvolution D & C cells are holding their LSD properties after one year and voltage is good, but I only load them to <2 amps. Some 7Ah cells could perform better than other 10Ah cells.

I depend on discharge capacity to more accurately reflect my actual use. Charging capacities may be up to ~30% higher than actual due to, say, only a 70% charging efficiency.

It would be nice if large rechargeable cells had warranties. There's potential to spend hundreds on cells that only last a couple years or drop off in performance in less time.

BTW, my RayOVac Hybrids of four years are all deteriorating. My four year old "Duraloops" have lost only 100mAh or so, and are maintaining good voltage under loads of an amp or less.

my older duraloops are performing pretty much new like the day i bought them too. It would be interesting how long these blue label d cell tenergys would last with proper maintenance.