# Can I get battery capacity by knowing my need for powering load?

Let's assume we have some load with current I to run for time t. Can we get needed battery capacity C? For this let's use Peukert's law t=H*(C/(I*H)^k where H is battery rating of discharge time and k=1.2 for most lead acids batteries. Normally H value is around 20 for an average sealed lead acid battery. For those who doesn't know where to get it, please put 1 in the last Hrate field. Very often manufacturer claim H=20. I disagree as I haven't seen true 20C rate battery. Here s the capacity C(Ah), solver for lead acid battery, where I-load current, t-time to run the load, H -is battery discharge rating.

Capacitance 0: Ah

example: Boat has 10KW , 24V electric engine. Time to use it 20min. How big is my battery should be? I=10000/24=41.66A, t=20min=1/3hour==.33hr, H=20,then calculator should give 27.6Ah

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