How do you charge 8000mha 6s

That's a common misconception. '8000 maH' refers to the amount of energy stored in the battery (it can supply 8 Amps for an hour, or 4 Amps for 2 hours and so on)

You can charge it at any rate lower than that - the lower the charge rate, the lonfer it will take is all.

Think of the battery like a 5 gallon jerry can - you can fill that fast or slow until it reaches capacity

Pse, don't mix terms. The charger can supply max 5A (5000mA) current. In two hours it will charge 10Ah (10000mAh), 5A * 2h.

Fred

If he wants to charge in 30 minutes he needs above 400W (25.2V * 16A).

If your charger can handle max 5000mAh packs, it may have a safety feature that cuts off after having put 5000mAh into the pack (or some percentage above that), or it may cut off after some time interval based on the rate you set it to. Most likely you will have to charge your battery in two turns, first the initial 5000mAh and then the remaining 3000mAh. There is no limit to the size of pack (mAh-wize) that you can charge on your charger, but it can probably not do it continuously in one go from start to finish, if it is much larger than 5000mAh.