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I’ve searched and searched and am still very confused. I’m running an RC10B. Currently super stock brushed motor. Once it’s pretty much worn out I’ll be going to an equivalent brushless motor and controller. I’m about to buy my first LiPo batteries. I was thinking of 5000mah 30C batteries.

Questions,
Would this battery be the right discharge rate for these motors?
My chargers max LiPo charge rate is 2.5a. Will this charge rate be OK for these batteries, any long term issues? I understand I can charge them at 1C (5amps) so it will take longer at 2.5a. Any idea how long it will take to fully charge at 2.5a?

5000mah at 30c means you have 150a burst capacity. Should be fine for any reasonable motor you can think of.

charging at 1/2c will take twice as long to charge, so if 1c would be theoretically 1 hour, 1/2c would be 2 hrs. you will have absolutely no issues with the battery provided you don't:

charge more than 2c or so(the 'rule' is 1c, but the lipo chemistry is pretty good now and can handle more)

try to charge without a lipo specific charger

pierce the pack in any way, or

over-discharge.

I've heard that charging them at a lower rate will take them to a higher voltage and provide more power. I guess the gentler charge keeps it from shutting down early. Again, this is what I "heard", so I can't swear by it, nor have I tried it. The classes I race don't rely on raw power so it's not worth the extra time for me.

Like was said, 2.5 amp rate will charge it just fine, it will just take longer.

I have heard some of the on-road (sponsored pro type drivers) charge at 3c to get heat into the packs and get higher voltage. Of course when you have a battery sponsor who will keep feeding you cells, I guess it doesn't matter if one decides to puke when doing it this way....

You can always charge at the 1c capacity of the battery...5A for 5000, 3.2A for 3200, etc. That being said, most newer, better quality packs you can charge at 2c no problem. A friend of mine has been charging at 4c because he is impatient but the high end cells will actually take that now (like the ones you see rated at 60c for example). Higher charge rates are supposed to shorten cell life, but I have a Thunder Power 5000 40c that I charge at 10A all the time that is a year and a half old, and is still fast. That is after everything from mod sprint car to carpet sedan.

You actually will not heat a cell up charging at a high rate as easily as just discharging the battery for let's say 2 minutes @ 30A and recharging it. You really need to blast the cells to get them as hot as a quick discharge. Or if you want to make it easy, just heat them with a reptile warmer or a heating pad. That will get them hot and not harm the cell. This is all moot as most racing rules now enforce a battery temp allowable above ambient.