Alternative for a 18650 2200mAh 3.7V Li-on battery

Question

I'm building my first robotic car (Elegoo Smartbot Car Kit) but I'm struggling with which batteries to buy. The kit itself doesn't seem to say too much other than they're 18650 LiPo batteries which I've now learned 18650 refers to the dimensions of the battery and LiPo is Lithium Polymer.

I watched an assembly video and managed to pause right on the spot where the guy shows the batteries: ICR 18650 10/17 2200mAh 3.7V and the last part is difficult to read but it looks like 8.14Wh.

I've looked online in South Africa and can't find an exact match for these batteries.

I don't know much about batteries/electrics so I'm not sure what alternatives I can use and when I'll be looking at damaging the electronics.

I seem to be able to get anywhere from 2000mAh to 4200mAh all 18650 and 3.7V. Some of these are Li-Po and some are Li-On. Some research lead me to believe that Li-Po and Li-On are compatible, the difference being that Li-On is perhaps better?

My understanding is that mAh (milliamp hours) refers to the ability of the battery to hold a charge... Not exactly sure what that means though.

• Is it safe to buy an 18650 battery with a higher mAh rating? I.e. it won't damage the car?
• Is my understanding about Li-On and Li-Po correct?

Answer 1

Welcome to Robotics, Jacques. Robot cars are a fun way to start down the slippery slope attractive activity of robotics. You won't run out of things to aspire to.

• Is higher capacity safe? Yes.

The term "mAh" (milliAmp-hours) measures how much charge the battery can hold. (Literally charge -- mAh could be converted to Coulombs.) The general idea is that a 2200 mAh battery could provide 2200 mA for 1 hour, or 220 mA for 10 hours, etc. Whether you could actually get that much current for that long depends on charging profile, discharge profile, "memory" effects, temperature, lifetime, even (unfortunately) how comfortable the manufacturer's marketing people are with lying to us.

At the same voltage rating (3.7 V in your case) a larger capacity is not a problem. It'll just let your device run longer between charges.

The phrase "hold a charge" is somewhat ambiguous. There's capacity, how much charge you could put in and take out, as above. Then there's the ability to retain a charge. Batteries discharge themselves over time, different types at different rates.

• Are Li-Po and Li-Ion compatible? Yes.

They are largely equivalent for your purposes. Each has its pluses and minuses. You could do a web search for "difference between lithium ion and polymer" and weigh which is best for your use. Cost and availability can be important considerations. Only you can judge those tradeoffs, and this Q&A site doesn't do "shopping" questions anyway.