Old 07-06-2010, 11:31 AM #1
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Default 18650 vs 3x Ni-Mh (AA - D) Batteries. Whats the Difference?

Hello all,

I'm new to LPF and currently planing/starting my first DIY Green Module build. Just have a quick question in regards with the supply(cell) power source. I'm planning on using module 150mw 532nm 3.5v - 4.2v.
I have searched but couldn't find a direct comparison between the 2.

What is the difference between 18650 vs 3x NiMH batteries.

I know that;

18650 is
Lithium-ion
3.7volt Nom
4.2volt Max
2500~mAh

3x NiMH is (AA, C, D)
nickel-metal hydride
3x 1.2v = 3.6v (Is this Nom or Max?)
2000-10,000 mAh depending on cell size and quality

So which battery setup is best? and why?

Thanks


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Old 07-06-2010, 04:50 PM #2
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Default Re: 18650 vs 3x Ni-Mh (AA - D) Batteries. Whats the Difference?

As far as powering your circuit, it really doesn't matter what you use so long as the batteries can provide enough voltage and current for your needs. The LiIon/LiPol batteries are lighter and smaller than NiMH batteries, and the higher voltage they provide means you can use fewer of them in tighter locations. Size and voltage are really the main reason people prefer them. Current-driving ability is also a reason to choose LiIon/LiPol batteries over alkalines, but I think NiMH batteries are able to source current quite well.
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Old 07-06-2010, 05:36 PM #3
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Default Re: 18650 vs 3x Ni-Mh (AA - D) Batteries. Whats the Difference?

I found out by searching NiMH discharge graphs that a full charge of a NiMH cell will be close to 1.4v but only for a VERY short time before dropping off and sitting at around 1.25v (Depending on current draw).
So 3x 1.25v = 3.75v. Pretty much the same/similiar to a 18650.

Quote:
Originally Posted by Bionic-Badger View Post
Size and voltage are really the main reason people prefer them.
Between the 2 options they both have similiar voltage, and can handle high current discharges. So i would think that it may just be a matter of Size vs mAh.
Do you want a smaller host/recharge more frequently or do you want a big host/longer lasting cells between recharges.

Unless anybody could add other factors that would make 1 option better than the other??
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Old 07-07-2010, 05:39 AM #4
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Default Re: 18650 vs 3x Ni-Mh (AA - D) Batteries. Whats the Difference?

Well the NiMH batters may not last as long as LiPo batteries either. LiPo batteries have the highest charge per unit weight for rechargeables, so a single 18650 will usually have more mAh than three NiMH batteries, despite roughly the same voltage. NiMH batteries should also last longer than LiPo batteries, because LiPos don't like being charged/discharged as much. LiPos self-discharge slower than NiMH batteries though.

For your lasers, I'd just stick with the LiPo batteries as much as possible because you only need few of them, and they don't weight that much. For NiMH you need multiple batteries to get the right voltage, and even with AAA batteries that can get bulky. Imagine the difference using a LM317 for powering a Bluray: six AAA batteries versus two LiPos. 18650s aren't exactly tiny, but two would fit into a host much nicer.
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Old 07-07-2010, 07:58 AM #5
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Default Re: 18650 vs 3x Ni-Mh (AA - D) Batteries. Whats the Difference?

Arn't 18650 a li-ion, not a li-po?

Quote:
Originally Posted by Bionic-Badger View Post
so a single 18650 will usually have more mAh than three NiMH batteries, despite roughly the same voltage..
In my case, my options are 1x 18650 or 3x "C size" NiMH's.
18650 - 2500mAh~ 3.7v
3x C NiMH - 8000mAh~ 3.6v-3.7v

I realise that the size of the host will be much larger to accompany these batteries but this OK. I just want the best performing battery setup.

This measures 230mmx38mm (9in x 1.4in)
eg.
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