6 x 50 = 300watts of PV. 300w/24v = 12.5a. 6s = 36v = OK for 24v battery.
For the MPT 7210a the18v (3s2p) panel config should work. If you already own the MPT 7210a, then definitely try it. The output is limited to 10a (not the input) so you would potentially be leaving 20% of charging capability on the floor - but on the other hand, static panels are rarely more than 80% efficient for any significant portion of the day - so 6 x 50w panels would match up very well.
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Next - you could move up to a dedicated PWMcharge controller....
The really cheap charge controllers ($15) don't do lithium / are not settable - so unless you find a specific one for lithium (which might be out there somewhere) - its not going to work for you.
Next would be lithium friendly PWM such as these:
I would look for a lithium compatible charge controller such as this:
https://www.amazon.com/Renogy-Charg...1PL1B9/ref=psdc_2236627011_t2_B073STGTHT?th=1 ... but you probably need the $39.11 Bluetooth module as well - so $60 range.
This one has a screen - maybe enough and more like $52
https://www.amazon.com/Renogy-Adven...AE9DCMGK73X&psc=1&refRID=E5MKGDNQWAE9DCMGK73X
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Next - you could move up to a true MPPT charge controller.... such as this:
https://www.amazon.com/dp/B07DK5B63...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
I started with one of these - and withe the external unit, they fully settable for your lithium-ion battery bank.
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Next would be large power charge controllers - but that's beyond this discussion.
The ones I link to above are just suggestions that are representative of the price range for the power range. This also depends on $ you're willing to spend, long term goals, etc. As you clarify your longer term goals and can say how large you want your PV input to be - I'm sure you can get several specific recommendations.