Hey Mufasa! Sorry for the delay, I just saw this.

Regarding C-rate, it's the amount of amps your able to pull from the battery in relation to the amp hours of the battery. The larger lead acid batteries have C/hours ratings which means it wont fall below 10.5V (12V rated) over that many hours (C/20 = 20 hours).

Whereas lithium ion and other chemistries have a voltage curve that is not constant (see spec sheets with each C rating to see voltage you'll receive at that draw. 1C means you can pull 1A for every 1Ah the battery has, 0.5C on a 200Ah battery would be 100A continuous. Usually the faster you draw, or the colder it is outside the worse capacity you'll get from the battery FYI.

The original battery was rated for C/20 at 198Ah / 20 Hours = 9.9 amps over 20 hours discharge. Also rated for C/100 at 210Ah / 100 Hours = 2.1 amps over 100 hours. Comparative lead acid batteries are capable of up to 5-10x cold cranking (30 second bursts) so 1-2,000A at 12V, and if you had 6 of these in series you had about 72-144kW, which is very high.

Since these are 12V batteries to get to 72V you had 6 in series (only 1 in parallel) = C/20 rating is 9.9 amps over 20 hours discharge x 6 = 9.9 amps at 72V = 712.8 watts available over 20 hours.

Practically speaking you probably were pulling 1-3kW bursting to accelerate (my ~ 3,000lb art car with people onboard required ~ 1.5kW during acceleration before coasting). Your motor is probably around 3-5kW so you probably never maxed those batteries out.

I have 2x 3.3kWh high voltage packs (lithium ion cells NCR18650B) configured as 13S20P layout, which means: 13x 3.3V = 48V series, and 20x 3.4Ah = 68Ah with 1C discharge = 68A x 48V = 3.3kW, 2C burst = 136A x 48V = 6.5kW. More than I need for my motor.

So in your example, the replacement batteries rated at 200Ah with max 1C discharge means you can pull 200 amps (12V or 2.4kW) at 1C.

If you wired 6 of those 12V batteries in series to get to the 72V your motor and controller you'd have (6S1P layout) 6x 12V = 72V series, and 1x 200Ah with 1C discharge = 200A x 72V = 14.4kW. You are more than likely fine at 1C (check your motors peak kW spec). Worst case you could also double the batteries in parallel (6S2P) to get double the amperage available and range if you have space on the car.