Either the worst or most mundain situation.

[snows.world]

TLDR. I have what seems to be a 13s10p battery. is it going to blow up now if it's been alive for 4 years with a 500w controller ? now that I'm pushing around 1000w through it.. will it kill the battery or the controller first ?
Wire coming out of the battery is 12 gauge, goes down to 14 as far as I know within the motor cabling.

 

[snows.world]

theres corrosion in one pack within a string of negative cells. 3 cells. ITs because of friction and water. I remedied that I think. Stopped it from spreading.

 

[addertooth]

Knowing the AH rating of the battery, and the upper limit of the battery management system (BMS) would allow us to give a better answer.
But, 4 years is fairly old for a battery, depending on how many FULL charge cycles (equivalent) it has been through, whether it has been exposed to extreme temperatures, and whether it has been left on float charge a lot.

 

[Smaug]

If it's questionable, (and it is, with the corrosion) you should not try to save money here, but scrap the battery pack before your burn something down. This is how lithium fires get started; some tinkerer who doesn't know what he's doing.