# Does mixing and matching battery capacities result in a bottleneck when wired in series?

I want to make a 12V battery pack to run an Nvidia Jetson TK1 for an afternoon. I am new to using batteries and was wondering - will mixing smaller capacity lithium ion batteries with larger capacity lithium ion batteries result in a bottle-neck &/or accelerated wear on the system?

I want to combine the voltages of these batteries to get over the 12V required to power the Jetson TK1, and thought it might be convenient to combine batteries. The prices per amp-hour are comparable, but I don't want to go way over the 12V (to 29.6V) by combining 9 of the smaller batteries.

2 x LITHIUM 3.7V 6AH (Model: ICR18650 6600mAh 3.7V 1S3P)    [1528-1835-ND]  $4.47 per Ah 2 X LITHIUM 3.7V 2.2AH (Model: ICR18650 2200mAh 3.7V ) [1528-1836-ND]$4.52 per Ah


From what I can tell by the model numbers, [digikey # in brackets], the candidates below are comprised of Samsung ICR18650 cells, although both the large capacity and small capacity batteries both output the same 3.7 volts.

• Recepie for disaster! Once the smallest battery is depleted the bigger one will continue to push current and reverse the voltage of the small battery unless you have built in protection. – winny Mar 25 '18 at 18:54
• But if you had 3 of the 2.2Ah ones, you could parallel them (balancing them first) to make another 6.6Ah one (that's all it is anyway) – Brian Drummond Mar 25 '18 at 18:59
• Ok. Sounds like a bad potentially dangerous idea. I will look into using same capacity smaller cells in parallel. – user391339 Mar 25 '18 at 19:01
• No, you don't look to connect smaller sells "in parallel", you would need a factory of batteries to find close match in charge-discharge curves. The first triple-battery (from China) already should have matched cells. Why would you want to replicate it? If you can afford a $500 development kit, find something more professional to power it. – Ale..chenski Mar 25 '18 at 20:12 • It's a TK1 not a TX1/2 so this battery pack will be more expensive than the current ~$80 TK1 ebay price, but you can't undervalue the utility of a nice battery. Now that I understand how serious an issue battery balancing is, I will look into getting a single pack of the right capacity or maybe going with a lead acid battery in my backpack. – user391339 Mar 25 '18 at 20:38