Battery Voltages Diagram Help

I tried to redraw this figure:

I was able to get this far:

My Code

                \documentclass[]{article}
\usepackage{tikz}
\usepackage{circuitikz}
\begin{document}
\begin{tikzpicture}
\draw[line width=5pt] (0,0) -- (0,3.5);
\draw[line width=5pt] (8,0) -- (8,3.5);
\draw[line width=.75pt] (1,4.35) (0,3.5) -- (0,4) -- (3.4,4);
\draw[line width=.75pt] (1,4.35) (4.6,4) -- (8,4) -- (8,3.5);
\draw (0,3.5) -- (0,4) to[R={Load}] (8,4) -- (8,3.5);
\draw[->,line width=.95pt] (1,4.3) -- (2.5, 4.3) node[midway, above] {$i(t)$};
\draw (3,0) -- (3,3.5);
\draw (5,0) -- (5,3.5);
\draw[dashed] (3,1.03) -- (5,1.03);
\draw[<->] (5.1,1.03) -- (5.1,1.25) node[below right] {$V_{e}$};
\draw (-0.089,0) -- (8.089,0);
\draw (-0.089,3.5) -- (8.089,3.5);
\draw[style=dashed] (0,2.8) -- (8,2.8);
\draw[style=dashed] (0,2.3) -- (8,2.3);
\draw[<->] (3.2,2.8) -- (3.2,3.5) node[ midway, right] {$V_{sp}$};
\draw (0,2.8) .. controls (1.8,3.4) .. (3, 3.5);
\draw (0,0) .. controls (1.3,.5) .. (3, .6);
\draw[dashed](0,.45) .. controls (1,.9)  .. (5,1.21);
\draw[dashed](5,1.21) .. controls (6.5,1.35)  .. (8,1.6);
\draw(5,1.65) .. controls (6.5,1.75)  .. (8,1.95);
\draw(5,2.05) .. controls (6.5,2.15)  .. (8,2.3);
\draw[<->] (2.2,.55) -- (2.2,3.445) node[midway, left] {$V_{Up}$};
\end{tikzpicture}
\end{document}

• What's the step you are trying to accomplish now and having trouble with? Is there some reason you can't add further labels as you have the ones you've already got? – cfr Mar 31 '17 at 1:40
• You already got very far, good work! Which element are you now struggling with? – Henri Menke Mar 31 '17 at 3:44
• Since you have already loaded circuitikz you can simply use \draw (0,3.5) -- (0,4) to[R={Load}] (8,4) -- (8,3.5); – John Kormylo Mar 31 '17 at 4:24
• I did updated the code to reflect the above comments. The two small curvy lines above Ve don't match the actual. The two current have arrows line to the left of them (Vs,n, Vn,n and VU,n). Also the text and two curved arrows under the whole graphs. – OOzy Pal Mar 31 '17 at 8:22
• If you know the mathematical expression for the curves, you can use that (see page 328 in PGF manual). – John Kormylo Mar 31 '17 at 16:34