Replacing 18500 Li-ion battery with 18650

[sirish]

Hello all,

 Can anyone shed some light on 18650 and 18500 batteries ? I'm upgrading 18500 battery to a 18650 one ? Space isn't a constraint and I need the battery to last longer. From my research I found that 18500 can max go upto 1700mAh. And I saw 18650's go upto 3500mAh. So the voltage ratings being the same, I'm assuming it'll run for double the time. Is that a fair statement ?

The 18500 battery I have is Sanyo UR18500FK. The 18650 I'm considering is Panasonic NCR18650B. Also looks like battery chemistries are different and I don't know if I should focus on that.

Thanks in advance !!
Sirish

[kiran_shrestha]

Hey !! I searched and found out the battery chemistries are same both Li Ion.. si in my case it would be interchangeable, and talking of extra 150mAh, I think wont do no harm if your project is not so critically depended on battery charging.

[james_s]

18650 and 18500 are form factors, not battery types. These are 18mm diameter and 65mm/50mm long respectively. Most are Li-ion although other types have been made in that size. Assuming li-ion you'll be fine to replace one with the other.

[Brumby]

This:

18650 and 18500 are form factors, not battery types. These are 18mm diameter and 65mm/50mm long respectively. Most are Li-ion although other types have been made in that size. Assuming li-ion you'll be fine to replace one with the other.

That type of nomenclature is also used in 'button' cells - eg CR2032 is 20mm diameter and 3.2mm thick.

[Rick Law]

Hello all,

 Can anyone shed some light on 18650 and 18500 batteries ? I'm upgrading 18500 battery to a 18650 one ? Space isn't a constraint and I need the battery to last longer. From my research I found that 18500 can max go upto 1700mAh. And I saw 18650's go upto 3500mAh. So the voltage ratings being the same, I'm assuming it'll run for double the time. Is that a fair statement ?

The 18500 battery I have is Sanyo UR18500FK. The 18650 I'm considering is Panasonic NCR18650B. Also looks like battery chemistries are different and I don't know if I should focus on that.

Thanks in advance !!
Sirish

The capacity rating 1700mAH means it can provide 1mA for 1700 hours or 1700mA for one hour at the state voltage.  In real life, that is never true.  Typically, the capacity will be reduced when the discharge current is increased.  So unless you know at what current is that capacity rated for, you really don't know for sure.  What you do know for sure is, their capacity listing is likely just the best case scenario number.  When drawn at high current, the 1700mAH battery may end up delivering a lot less.

But in general you are right, 3500mAH would indeed be just a bit over twice 1700mAH, approximately.

The chemistry in general doesn't mean much as long as it can provide the level of current and voltage you need.  Li-PO usually provide a lot higher current than LiIon can.  It can also be charged at higher current than LiIon can.  But it looks like you are looking at LiIon since you are talking 18650 vs 18500.  It does affect the voltage however.  Some LiIon chemistry are charged to 4.35Volt and some lower, some LiPO are charged to different voltage also.  So yes, it matters as it will affect how high a voltage you can charge them to.

Just to be complete, I'll add this: you can use the lower charge-to volt.  You can charge the 4.35V battery to just 4.2V and it will work but you loose some capacity.