Connecting multiple batteries in series


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karnage

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Hi guys (and gals too, yeah), just want to find out:

I'm connecting 8x 1.2V NiMH AA batteries in series to get 9.6V (it's abit over the top but it works on my camera, which only requires 7.2V). Each cell is 2500mAh. So this whole circuit can be regarded as a single 9.6V NiMH cell right? The question is, what is the mAh rating then? Is it still 2500mAh or is it 8 x 2500mAh = 20Ah (20,000mAh)? :think: :dunno: :bsmilie:


Miscellanous info: I'm constructing a DIY battery pack (aka hand grip) for my Panasonic FZ20. This will probably be mounted underneath, like all battery grips, by the tripod thread. Wondering how to make another tripod thread so I can still mounted the whole thing on a tripod... :sweat:
 

fuzzy

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#3
Nope, connecting batteries in series will only give u added voltage. mAh stays the same.
 

user12343

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#4
i beg to differ.

when u series-connect 8 similar batteries together, what u gain is just battery voltage and not capacity (in terms of mAh) 9.6V with 2500mAh.

when u parallel-connect batteries together, u gain longer running time (more mAh) but voltage remains as a single-battery voltage. 1.2V with 20Ah.

having said that, if u series-connect batteries of different capacity, the max operating time is determined by the lowest capacity of the battery connected.

karnage said:
Hi guys (and gals too, yeah), just want to find out:

I'm connecting 8x 1.2V NiMH AA batteries in series to get 9.6V (it's abit over the top but it works on my camera, which only requires 7.2V). Each cell is 2500mAh. So this whole circuit can be regarded as a single 9.6V NiMH cell right? The question is, what is the mAh rating then? Is it still 2500mAh or is it 8 x 2500mAh = 20Ah (20,000mAh)? :think: :dunno: :bsmilie:


Miscellanous info: I'm constructing a DIY battery pack (aka hand grip) for my Panasonic FZ20. This will probably be mounted underneath, like all battery grips, by the tripod thread. Wondering how to make another tripod thread so I can still mounted the whole thing on a tripod... :sweat:
 

thomas_lkt

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Apr 26, 2004
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#5
nope. it's still 2500mah.
batteries connected in series result in voltage increase but capacity remains.
do note that when fully charged, the voltage will be more than 11 volts.
 

karnage

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#6
What do u mean by "its MAX, not constant for NiMH"?

Hmm... so if it's really 20Ah, does it mean it'll last DA-A-AMN long? Comparatively, the original 680mAH can last me about half a day's shoot or around 200+ shots.

So

20,000/680=29.412

Almost 30x longer?! Sure anot... doubtful leh... that's like half a month of continuous shooting leh. :eek: :bigeyes: :lovegrin: COOL!
 

karnage

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#7
fuzzy said:
Nope, connecting batteries in series will only give u added voltage. mAh stays the same.
Ya... that's what I thought initially too. But having no background in electronics except secondary Physics, I'm very doubtful as to what I think. Haha!

Oh wells...

Are you sure when fully charged it'll be more than 11V? That's quite scary... might deep-fry my cam. I tried this circuit just now for a few seconds... it was fine. Maybe it wasn't long enough to deep fry it... yet.
 

hongsien

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#9
karnage said:
Ya... that's what I thought initially too. But having no background in electronics except secondary Physics, I'm very doubtful as to what I think. Haha!
I thought you would have gotten this at sec Physics?.......

HS
 

zcf

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Apr 10, 2005
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#10
karnage said:
What do u mean by "its MAX, not constant for NiMH"?

Hmm... so if it's really 20Ah, does it mean it'll last DA-A-AMN long? Comparatively, the original 680mAH can last me about half a day's shoot or around 200+ shots.

So

20,000/680=29.412

Almost 30x longer?! Sure anot... doubtful leh... that's like half a month of continuous shooting leh. :eek: :bigeyes: :lovegrin: COOL!
It should be as user12343 stated: 9.6V with 2500mAh

so 2500/680 = 3.67x longer time only.

If you afraid of more than 9.6V may fry the camera circuit, why not just try 7 x 1.2V=8.4V only?
 

karnage

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#11
To AReality: 6 will result in exactly 7.2V, as required by the camera. But I do know/ heard of people who tried it but after some use the voltage drops so that it isn't enough to power up the camera. So thought of using a higher voltage.

To zcf: As above, but 7 is an odd number to be used, I think. Don't like that number. Haha! And since the reason for not using 6 batts has been explained, the next up is 8...

To hongsien: Ermm... is it? Well, that just goes to show why I have reason to doubt what I think. :) Hee hee!
 

huggable

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Nov 2, 2004
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#12
The guys already explained the results and limitations of connecting batteries in series. Over-voltage? Use it at your own risk.

As for the screw thread you'd like to make, find out the thread size (probably M6 or M8) and get a nut of the correct size. Mount the nut and secure it, make sure it doesn't turn, into your DIY battery pack. From there, the screw of the tripot can mate with the nut to mount the camera on the tripot.

karnage said:
Hi guys (and gals too, yeah), just want to find out:

I'm connecting 8x 1.2V NiMH AA batteries in series to get 9.6V (it's abit over the top but it works on my camera, which only requires 7.2V). Each cell is 2500mAh. So this whole circuit can be regarded as a single 9.6V NiMH cell right? The question is, what is the mAh rating then? Is it still 2500mAh or is it 8 x 2500mAh = 20Ah (20,000mAh)? :think: :dunno: :bsmilie:


Miscellanous info: I'm constructing a DIY battery pack (aka hand grip) for my Panasonic FZ20. This will probably be mounted underneath, like all battery grips, by the tripod thread. Wondering how to make another tripod thread so I can still mounted the whole thing on a tripod... :sweat:
 

rahul

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Jun 30, 2005
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#13
Try a 12 cell, [6X1.2] X 2 battery pack.
With the two rows of 6cells each in parallel. That would keep the potential difference same (7.2V) and give you extra extra long battery life.

The battery pack might weigh more than your camera though.
Dont mess with extra cells in series. More than specified voltage can be very harmful for your camera.
 

Firefox

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Feb 15, 2004
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#14
karnage said:
To AReality: 6 will result in exactly 7.2V, as required by the camera. But I do know/ heard of people who tried it but after some use the voltage drops so that it isn't enough to power up the camera. So thought of using a higher voltage.

A fully charged Nickel based cell has it's voltage at 1.4v, which means your 8-cell pack gives 11.2v at full charge. It drops to 9.6v after a while..

I'd suggest sticking to 6 cells in a pack... Or 12 cells (2 * 6-cells in parallel) for extra capacity..
 

karnage

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#15
Hmm... after how long does the voltage drop? Well, I never thought of the series-parallel method... Sounds good! Haha! Really never thought about it. Will think things through & then decide if I need more batteries. Thanks, rahul & Firefox, for the great suggestions!

And thanks too, huggable (are you really? Haha!), for suggesting the bolt & nut method. Actually it kinda dawned on me just now on the bus... haha! But do hardware shops know what you're talking about if u went in & told them u want an M6 bolt & nut? There's also the thread per inch thing right? Does M6 specify for 20 threads/inch, 1/4" diameter? Coz I think that's my tripod screw thread. The standard smaller one la... y'know?
 

thomas_lkt

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Apr 26, 2004
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#16
when battery is being used, the voltage drop is not linear with time. the voltage will gradually drop from about 1.4v to around 1.2v by the time you have used up 10%-20% of the battery capacity. the voltage will stay around 1.2v until about 10% capacity left and will drop rapidly after that (like falling off a sharp slope).
 

karnage

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#17
Hmm... not linear with time? So there's no formula to calculate is it? Not that I want to calculate... :sweat:

I think dropping to 1.2V after 10-20% shouldn't take too long? Anyways, I think I should heed rahul's advice on not messing around with increased voltage. Maybe I could try out a 6-pack 2500mAh first since it'll only drop voltage when the battery is left with 10%... Think it should still last about 3.67x longer? Then if I feel it's not long enough, I'll do the 12 cell pack. What say you guys?
 

huggable

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#18
Basically the M- prefix is for Matric standard, 1/4" is for the imperial standard. Matric screws are available in standard or fine pitch, not sure about imperial tho'. You can bring your tripod to a hardware or DIY shop to match a correct nut size, the uncles at Alexandra Village are often helpful, even if you're only buying a nut. And yes, the hardware shops knows all these jagang, some could spot the thread size by just looking at it! To find out the dimension of the thread, use a pair of venier calipers to measure the outher diameter of the screw thread. Hope this helps.

Really Huggable? Ask my wife! :bsmilie:

karnage said:
And thanks too, huggable (are you really? Haha!), for suggesting the bolt & nut method. Actually it kinda dawned on me just now on the bus... haha! But do hardware shops know what you're talking about if u went in & told them u want an M6 bolt & nut? There's also the thread per inch thing right? Does M6 specify for 20 threads/inch, 1/4" diameter? Coz I think that's my tripod screw thread. The standard smaller one la... y'know?
 

thomas_lkt

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Apr 26, 2004
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#19
karnage said:
Hmm... not linear with time? So there's no formula to calculate is it? Not that I want to calculate... :sweat:
....
not aware of any formula to calculate the voltage drop with time. the discharge curve not a simple as it has 3 slopes; initial, nominal and final. each of these slopes have different gradients which are non-llinear.
 

V

vince123123

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#20
Where exactly is Alexandra Village? I've been boggling over this tripod screw question for a while myself (also posted about this some time back).

huggable said:
Basically the M- prefix is for Matric standard, 1/4" is for the imperial standard. Matric screws are available in standard or fine pitch, not sure about imperial tho'. You can bring your tripod to a hardware or DIY shop to match a correct nut size, the uncles at Alexandra Village are often helpful, even if you're only buying a nut. And yes, the hardware shops knows all these jagang, some could spot the thread size by just looking at it! To find out the dimension of the thread, use a pair of venier calipers to measure the outher diameter of the screw thread. Hope this helps.

Really Huggable? Ask my wife! :bsmilie:
 

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