This is the panel made from damaged 3600ma tabbed cells.
The sun was nice and bright for a winter morning so I gave the panel another test run at 8am.
The first issue was condensation in the panel. A bit of remedial drying and re-sealing should fix it.
The voltage when the cells were cold read 19.23 but when the cells warmed up it dropped. Something for me to research.
The pictures tell the story.
3.56 amps x 16.88 volts = 60 watts! At 8am in winter.
At 12 o'clock I tested again. The results were 3.69 amps x 16.65 volts = 61.4 watts.
Once again a voltage drop but amperage increase.
Keeping in mind that I used only 35 ( at this rate 36 would give more than 63 watts) of the damaged cells from the batch for this panel I have no problems seeing 36 of the perfect cells making a true 70 watt panel.
I'm hoping the blocking diodes etc. in the panel lead box might help keep the voltage up. 19.8 volts at 3.69 amps would give 73 watts! Nice.
I worked out the cost of the panel based on full retail prices for all bits.
Ply x 2 = $12.00
Perspex x 1 = $38.00
18mm square wood x 6 metres = $10.20
Extra Tab wire x 1 = $5.00
Solder, flux, paint etc = $5.00
Selleys All Clear x 1 = $6.00
Alligator clips and wire = $2.00
Solar cells x 35 @ $8.00ea. = $280.00.
All of the hardware items were off the shelf at Bunnings in Wagga Wagga.
Electronic components were not.
Total $358.20 for a 70 watt panel.
The cheapest 70 watter I could find online was nearly $700 and was an amorphous panel.
I own a 20 watt ( I wish ) commercial ebay type panel (on the right just in case you couldn't tell the difference between my DIY and a commercial panel :~) ) .
It produces a whopping and nearly half wasted 29 volts but at only 0.6 of an amp. On paper that gives 17 watts but my controller can only use 18 volts so, in reality, the panel only gives about 10 watts.
Much the same as this one made from scrap cells and a Styrofoam box lid. This one cost $100 less.
I'll post again when the panel lead boxes arrive and let you know if it makes a difference.
Some people say you need the blocking diode to prevent leakage from battery to panel at night but others say there is a significant voltage drop with older diodes so the losses without the diode can be less than with one!
We'll see eh.
They never arrived.