# Same mAh, same volt - different current

I need to replace the 18650 battery of one application. The battery doesn't have any marking about volts, mAh or amperes.

Because it's 18650, the voltage is fixed - done. mAh - will use 2000mAh (let's say or higher.)

Now I got stuck when I was looking for battery 18650 2000mAh. I can see 5A, 10A, 20A or even more. Not getting what current matters here.

Wondering if someone can help me understand it?

What will happen if I use same volt and capacity battery but different in current.

I may sound rubbish, but trust me I have tried multiple articles but no exact scenario and answer.

• the title of your post is not quite correct ... it should be Same mAh, same volt - different maximum current Jun 18, 2020 at 0:34
• You will have to determine what maximum current your device needs. Jun 21, 2020 at 5:33

I can see 5A, 10A, 20A or even more. Not getting what current matters here.

Because it matters? If you build e.g. a power tool (say, a power drill) that draws 15 A to make the motor powerful, what help would a 5A cell be?

I may sound rubbish, but trust me I have tried multiple articles but no exact scenario and answer.

Not rubbish, but you haven't understood that the current is a maximum rating.

• your response make sense. Just to clarify a little bit more if current is maximum what we can draw mean a tool working on 10A, will work with another battery marked 10 or more amp right? Jun 18, 2020 at 11:23

18650 is supposed to be around 2000 mAh. This is because if different manufacturers make up a battery with almost the same chemicals and same size, everyone should end up with almost the same storage capacity. The ampere rating you are seeing may be the maximum current that can be safely delivered from the battery.

That being said, I am sure you would know that the market is a wild place and anything can happen here. There can be counterfeits, copies of originals, and even cells of different technology labeled as Li ion. So, as long as you buy from a source you can trust, I would suggest to buy the one with the smallest current rating that still satisfies the current needed by your battery powered device.

Also on a side note, if your device uses multiple Li ion cells in series, I would suggest to replace all the cells, use all the cells from the same source and preferably from the same batch. Mismatched Li ion cells in series creates a serious fire hazard.

• "because if different manufacturers make up a battery with almost the same chemicals and same size, everyone should end up with almost the same storage capacity.", yes, BUT: 18650 batteries are made for very different purposes! For laptop battery packs, where you need high energy density and long lifetime, for power tools, for which you need high power density and long life is desirable, but not as important, and model planes and cars, where you need even higher power density and battery lifetime doesn't matter that much at all. Therefore, these three different applications of the Jun 17, 2020 at 20:01
• same battery shape don't call for the same battery chemistry and structure, because different things are expected from them. Some things need to work at high temperatures - so you intentially use more metal electrode material, so that it doesn't get hot, but that volume of course is lost to electrolyte and thus, that ultra-reliable battery has lower capacity. So, yes, you get wildly different capacity in high-tech, high-quality cells – and you're right, the market for cheap cells is humongous, and terrible. Jun 17, 2020 at 20:02
• I used the word "almost" in that sentence to avoid all this fuss and keep it simple. The OP was asking about the confusion in apparent current ratings, not CIA factbook style detail on battery manufacturing processes. Jun 17, 2020 at 20:10
• Absolutely! I'm not saying your answer is bad, at all. It doesn't really answer OP's question, however (as far as I can tell), so I didn't upvote it. I just was sorry to see such a nice answer that was a bit off-topic :) so I tried to comment to add the remaining context a future reader could use :) Jun 17, 2020 at 20:12