Using an AA battery charger to charge D cells

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I have a battery charger which only fits AA and AAA batteries. I
recently bought a Maglight flashlight, which uses three D cells. I want
to put rechargable batteries in it, but I have no way of charging them,
unless I buy another (expensive) charger. It seems that almost all
battery chargers these days are only for the AA and AAA batteries. There
are only a few that charge the C and D cells, and they are 4 or 5 times
the price of the AA/AAA ones.

I'm wondering if I can charge the D cells using my AA charger. I have
several D sized battery holders on hand. I'm thinking of attaching some
wires to the battery holders and just using some alligator clips to clip
to the AA charger contacts. (Making sure the polarity is correct).  

Physically this is easy. But I wonder if the battery charger will work
properly on the D cells. Both the D and AA batteries are 1.5 volts, but
the D cells have a higher current capability.

The higher current makes me think that the charging time will be longer,
which is no problem. But I am posting this to inquire whether there are
other reasons to NOT do this? For example, will it damage the charger?

Comments, anyone????


Re: Using an AA battery charger to charge D cells
On 4/7/2018 11:42 AM, snipped-for-privacy@tubes.com wrote:
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This question has many dimensions.

Firstly, most of the rechargeable D cells you buy are just AA cells  
inside a bigger shell.  A 'real' NiMH D cell will be expensive and heavy.
You can buy the shells and recharge the AA's.
How much current does your flashlight need?
Easily available D-size may not have the run-time capacity you desire.

How does  your charger work?
If it's a slow charger, rated something like 16 hours, it just keeps
stuffing current into the cell forever.  NiMH don't like that.

If it's a fast charger the much higher capacity cell will not
reliably terminate the charge and the battery will get hot and degrade  
quickly.

You probably won't hurt the charger either way.  But you can damage
the cells.

The solution is NOT to buy flashlights using D cells if you want
rechargeable.
Get a light that uses rechargeable lithium cells and use a compatible
charger.

That ship has sailed.
So, the answer to your question is, "it depends."

If you buy a charger, make sure it can charge odd numbers of cells.
Many of the cheaper ones charge two cells in series.
That's a problem when your light has three cells.



Re: Using an AA battery charger to charge D cells
On Saturday, April 7, 2018 at 2:43:16 PM UTC-4, snipped-for-privacy@tubes.com wrote:
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Without knowing which battery charger you have, it is a little hard to say.  And if you did provide the battery changer model, I would still in the dark.

But I think you could make your kludge to connect to the D sized batteries with a resister to reduce the charging current.  Look on your charger and see if it has any verbiage which tells what the current is.

                                          Dan


Re: Using an AA battery charger to charge D cells
On Sat, 07 Apr 2018 13:42:20 -0500, snipped-for-privacy@tubes.com wrote:

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Amazon has universal aaa...d chargers under $15.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Using an AA battery charger to charge D cells
On Sat, 07 Apr 2018 12:34:15 -0700, John Larkin

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Ah, yes, Amazon, from which all good things come ;-)

Just had to order a new shower back brush... mine started shedding
bristles like crazy... the info tab said this was my 72nd order in the
past six months >:-}
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: Using an AA battery charger to charge D cells
On Saturday, 7 April 2018 22:26:31 UTC+1, Jim Thompson  wrote:
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not all for back brushes I hope!

I do get good things from Amazon/Ebay, but also ungoodly things. It's hard to tell which will be which.


NT

Re: Using an AA battery charger to charge D cells
On Sat, 07 Apr 2018 13:42:20 -0500, snipped-for-privacy@tubes.com wrote:

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D cells are too expensive to waste in a flashlight.  Get an adapter
that allows you to cram AA cells into your flashlight:
<https://www.ebay.com/sch/i.html?_nkw=aa+to+D+battery+adapter
I mostly use the adapters that come with Eneloop (Panasonic) NiMH
cells sold by Costco:
<https://www.ebay.com/itm/2-AA-to-D-D-Adaptor-Sanyo-Eneloop-Battery-Converter/392013317267

You might also consider switching your Maglite to Lithium Ion
batteries.
"Battery Alternatives for Maglite"
<
https://www.youtube.com/watch?v=fsyo_GUQMm4




--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Using an AA battery charger to charge D cells
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It's unlikely to damage the charger.

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NiMh charging is tricky. Many chargers look for the dip in  
terminal voltage that happens when the cell is full and starts
heating up

A D cell has like 3 times the surface area and 6 times the volume of
an AA *, so the slopes will be shallower. And if the charger uses an actual
temperature sensor it's not going to work at all.

(both numbers rough guesses)

--  
This email has not been checked by half-arsed antivirus software  

Re: Using an AA battery charger to charge D cells
On Saturday, 7 April 2018 19:43:16 UTC+1, snipped-for-privacy@tubes.com  wrote:
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The short version is it'll be fine. But if the cpacity is high it'll take l
onger. Don't recommend leaving them charging indefinitely.

Yes one could get a lot more into it, but no need. If it is a fast charger  
with small capacity Ds it'll work as usual, and a fast charger with large D
s will work as a slow charger. A slow charger with large cells could take a
 long long time to charge, but it will.


NT

Re: Using an AA battery charger to charge D cells
buy  a new LED flashlight that runs in 18650 cells.

they usually come with a charger.

mark


Re: Using an AA battery charger to charge D cells
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The reason Maglight uses such heavy cells is that you can use
the flashlight to hit someone on the head, while it is not
supposedly a weapon. This is a trade secret, of course.
If you don't care for that usage you can saw off three pieces of wood
with the diameter of a D cell, then bore a hole in it the size of an
AA cell. This saves you a lot of money, as rechargeable D-cells
are expensive.
In order to keep the original purpose, use steel instead of
wood.  (Then you probably need a lathe.)

<SNIP>

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Clearly now you can charge with an AA charger. Capacity need not be
much lower.

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Groetjes Albert
--  
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
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Re: Using an AA battery charger to charge D cells
On 8/30/2018 10:30 AM, Albert van der Horst wrote:
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Rechargeable D-cells are not alike.
While you can  buy real high-capacity D-cells, the ones
you get at the local department store are very likely smaller cells
inside a bigger shell.  You can get a good idea from the weight.

Charging a NiMH cell is easy.
The problem is deciding when to STOP charging.

Assuming you have a "smart charger".
If your charge current is too low for the cell capacity,
the charge may never terminate and you can damage the cell.
If your charge current is too high for the cell capacity,
there are multiple charge termination/heat issues.
For a mismatched charger, charging from different initial
states of discharge can present contradictory symptoms.

The web is full of very good and very bad tutorials.
The problem is deciding which is which.


Get good AA-cells and a matched smart charger.
Get conversion shells to make them fit the D-cell light.




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