q(t)= ∫ t 0 t i(τ) dτ MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdi9qqqj=hEeeu0lXdbb a9frFj0xb9Lqpepeea0xd9s8qiYRWxGi6xij=hbba9q8aq0=yq=He9 q8qiLsFr0=vr0=vr0db8meGabaGacmGadiWaaiWabaabaiaafaaake aacaWGXbGaaiikaiaadshacaGGPaGaeyypa0Zaa8qCaeaacaWGPbGa aiikaiabes8a0jaacMcaaSqaaiaadshadaWgaaadbaGaaGimaaqaba aaleaacaWG0baaniabgUIiYdGcciGGKbGaeqiXdqhaaa@49EF@
where t0 is any instant before the first supply of electric energy