Charging high capacity D cells

pzb

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I'm new here and trying to make sense of all the information about chargers. I bought 4 of the Maha 11AH NiMH size "D" batteries for a baby swing recently, and tried charging them in my existing Energizer NiMH charger. While they somewhat recharge, I do not seem to be getting a full charge.

After reading about chargers, I was hoping to find a "fast" charger that would work with these batteries, but most seem to be ΔV based. Some of the stuff I read suggested that NiMH ΔV needs at least 0.5C charging current, preferably close to 1.0C. I have yet to see any charger that would charge these batteries at 0.5C, much less close to 1.0C. What kind of charger do people use with these batteries?
 

VidPro

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ha ha good point.
the primo high ticket Mahas like the 808 and 9000 stop at a voltage, so although they are V-drop chargers and would somehow need a 5+ AMP charge to cause the evil v-drop to even occur, they dont rely solely on the v-drop itself, and cool out with a voltage max.
because of this they A: dont fully charge 103% and B: dont usually ever overcharge, so your battery can last a good long time.
the newer mahas are known for being "cool", the older models from way back , people would say they would get the batteries hot, it is likly that the older models didnt have the voltage max, and also couldnt very well detect the v-drop on C-D like your saying, and timed out eventually, that would be the clue you see in the reviews.

then there is hobby chargers where the voltage drop can be set to a very small ammount, and the charge rate can be set very high, which will get you a v-drop. With notes of cheap hobby chargers have a max WATTAGE they will work at. which shouldnt be a big problem with 3-4 ni-?? cell items. AND spotting a v-drop in series charging is art not science.
Hobby chargers that need power supplies too can NOW be purchaced for as low as $35 , ones that work on AC can be got for less than $60. so it is now possible to get a cheezy hobby charger for less than the $300 a primo one costs, and it will pull off the ONE thing you asked for cheaper than a really good maha.
but
a good maha will deal with the cells individually, and be pretty nice to them. i would go for some cheap or good hobby charger more, if you had many different cell items and types. i would have a tendancy to stick with a good maha for convienience ease , single cell care, simplicity, and user friendlyness to spouce.

also you can Sloooowww charge it at 1/10 c , say about ~800-900ma for 16hours, would be fully safe, as long as its not insulated, or covered, perfect rate slow chargers not so easy to find nowdays, but you can potentially make one if you do it exactally right.

you can get one of them crappy timed chargers that dont go fast enough to cause a problem, some of them will time out before 1/3rd of a full charge, some can get a 80% charge, and some will overcharge for a bit. if you got a ~800ma-1A one of them, it would work just like a slow charger, and not cause much problems via the timed only, because the rate would be low enough. just dont try and use the same thing on your AAs :) unless you know the AA rate TOO.

also with the right simple voltage regulation you can get both fast charge and slowdown to below 1/10c , but if that is wrong, it can be very bad. or combos of voltage & current regulation, using cheap or expencive parts and pieces, bench supplies, kit regulators, or parts from the web or local electronic stores.
 
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McAllan

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@ OP
If you tell where You live we can also better guide you to a suitable charger.

You're right many chargers have difficulties charging D cells over 4 Ah. Usually because of a "safety timer".

I have an older Conrad Charge Manager 2010 (from around/slightly before Y2K) which charges my 7 Ah D's absolutely beautifully with 2 A. No safety timer but it terminates when it's supposed to.
Even the cheap Tecxus charger I mostly use as it's silent have no trouble with the 7 Ah cells even though it charges AA and over with 1 A (AAA with 500 mA). If they're empty I however have to run them twice because of the safety timer. Second time and if only needing topping up then it finishes much faster which means safety timer doesn't engage.

You can get a new/bigger model from Conrad, Charge Manager 2020 with 8 cell capacity but if only using 4 of them it can charge with 4 A and so should be future proof for probably even 20 Ah cells without problem.

However I'd rather go for 8.5 Ah low self discharge cells than regular 11 Ah. If I remember correct the LSD cells also tends to be easier to detect the drop when they're full.
 

Navin_R_Johnson

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If you have the same Energizer charger I do, it is strictly a timed charger with low current. The timer is designed for very low capacity batteries (sub 2000mah). If memory is right it does trickle charge at something like 50ma after the timer cuts off. Reseating your D cells after the charger indicates done about 6 times should get them charged. It will still take quite a while though.

Before I got my C808, I used to reseat my 5000mah C-Cells 3 times. The 808 is much faster and more convenient. I do not have any NiMH D cells so can't say for sure how it would work with those, but expect it would be great. I think it can charge at 2A.
 

Russel

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I have has good result with a Maha MH-C808M charger and AccuEvolution 10Ah LSD D cells. It charges the cells at 2A seems to give them a good charge. Although using a C/10 rate for 16 hours does result in more of a full charge.

https://www.candlepowerforums.com/posts/3295296&postcount=32

I wondered about charging at 2A which is C/10 and the posibility of charging at 5A (C/2 for AccuEvolution LSD D cells). So, I took a look at the specifications for the AccuEvolution LSD D cells, and found that the Accupower recommends a 2A fast charge.

http://www.accupower-usa.com/UpLoads/Spec D.pdf

That satisfied my curiosity about charging my D cells at 2A. And, knowing that one hour of trickle charge after the main charge with the MH-C808M doesn't risk overcharging the cells, I usually charge my D cells overnight and am not concerned about leaving them to trickle for several hours after the main charge.

I couldn't find any detailed information regarding charging recommendations for Maha 11Ah NiMH D batteries. But you might consider the MH-C808M charger.

Here is a very good review that SilverFox was kind enough to post for us:

https://www.candlepowerforums.com/threads/102682
 

Fulgeo

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I have has good result with a Maha MH-C808M charger and AccuEvolution 10Ah LSD D cells.


I have purchased 4 of these chargers so far and they are the best for D cells. Going to +1 Russel's post. Buy this charger and do not look back!:thumbsup:
 

pzb

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@ OP
If you tell where You live we can also better guide you to a suitable charger.

I'm located in Canada. Based on the other posters, I'm looking at the Maha C808M. The Conrad chargers seem like very nice options, but that are very pricey and I don't want to have to ask a colleague in Germany to buy it and ship it to me.

I see NewEgg is selling that C808M for $80. That looks to be about the best deal around, unless someone has a better suggestion. I would love to find a Canadian shop that sells near that cost, but do not hold out much hope.
 

Black Rose

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I see NewEgg is selling that C808M for $80. That looks to be about the best deal around, unless someone has a better suggestion. I would love to find a Canadian shop that sells near that cost, but do not hold out much hope.
Pauls Finest (Montreal) sells the Maha C808M for $114 CDN plus taxes and shipping.

That's where I got my C9000 and C800S.

I use my C9000 for C & D cells.
 

VidPro

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There are two clearly negative reports on Amazon concerning this charger; two caught on fire and another severely malfunctioned.

Has any one here had issues like that...?

http://tinyurl.com/yer4ala

holy Cow, i never saw that before, amason is a good place (often) to see reviews of people who have long since used something.
(vrses E-bay with little info, and even epinions and review sites that dont have as many people chiming in)
Now i guess i got another charger that i have to watch out what i put on it, and hope it doesnt have a computer crash :mecry:again.
thanks for the pointer.
 

VidPro

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I wondered about charging at 2A which is C/10 and the posibility of charging at 5A (C/2 for AccuEvolution LSD D cells). So, I took a look at the specifications for the AccuEvolution LSD D cells, and found that the Accupower recommends a 2A fast charge.

http://www.accupower-usa.com/UpLoads/Spec D.pdf

specs ohhh :)
side note, did you see thier charging graphs which seems to show a v-drop on the .5c rate, but not as strong on the low rate.
 

SilverFox

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Hello Pzb,

Welcome to CPF.

Many data sheets on C and D cells specify a charge rate of 2 amps. The larger size seems to hold heat inside the cell and higher rates can sometimes cause these cells to get quite hot.

While I am a very strong advocate for 0.5C - 1.0C charging for AAA, AA and SubC cells, the consumer C and D cells will most likely do well at 2 amps.

Tom
 

Russel

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specs ohhh :)
side note, did you see thier charging graphs which seems to show a v-drop on the .5c rate, but not as strong on the low rate.

Yes I did, it makes a good example of why charging NiMH with only negative delta peak termination should be charged at a minimum of C/2. It seemed kind of funny with a recommended fast charge rate of 2A and a nice negative delta peak at C/2 or 5A.

A good reason for the MH-C808M charger to have voltage termination.
 

Russel

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...The larger size seems to hold heat inside the cell and higher rates can sometimes cause these cells to get quite hot...

I haven't calculated it, but there has to be quite a difference in surface area to volume between AA cells and D cell.
 
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