Question about series battery connections

[saming]

hello i was wondering could i hook up a 4s 5000mah 20c with a 5s 5000mah 20c to make a 9s 5000mah battery. i assume maybe but nothing tells me i cant. but it also strongly point at dont do this.

 

[beto_pty]

No problem ...it will work perfectly

 

[voodoojar]

As long as the C rating and mah are the same you're good. If not you're going to damage the weaker batteries.