Excellent. I’ve been thinking of using cells that are not good enough for a powerwall and allowing them to dump into a bank of resistors like you did. The objective would be putting a fan on them to use as a small heater in a tent or small camper situation. Charge with Solar and use randomly. Any input would be helpful. Any idea what resistor value you might start with?
The value of the resistor depends on the voltage of the battery. Because this is a sub 4 volt system, I used .2 ohm 100 watt resistors. You need a very low ohm resistor for current to flow with a low voltage. About the battery- Let's assume the cells are old and that the failure rate is high. When parked in a large parallel group a dead cell can ruin the rest of the cells in it's group by dragging them down and killing them. So, making small parallel groups but a high voltage battery would limit the damage. But, the management issues- keeping all those unruly cats balanced- would be difficult. So suppose you just made one 100P battery. A 4 volt AC charger or power supply would be all that was needed, no balancing required. A dead cell would have a lot of healthy cells and would be unlikely to bring down the whole pack. But you will be charging with solar. So I would suggest a compromise. Build a battery that can be bulk charged with your solar panels voltage- to 4 volts per cell- maybe a 12 volt? Then use a cheap hobby charger every week or so to balance charge it.... You got me thinking here!
Yes I see where you are going. Luckily this idea has no sensitive loads just resistance. A Solar Pwm Charger would take a 4S pack to 13.8v of charge way below the 4.2v change which would charge to 16.8v . Yes I think a higher Parallel cell pack would be good as you suggested. Cells with a Higher C rating such as 1500-2000 mAh might work best. I was also thinking that when building the 4S pack that leaving an open cell row between cells would allow more ventilation of heat. Regardless of the heat being from the batteries or resistors it’s still BTU’s either way.
Been busy with BatteryBlocs! Got a new girlfriend! Remodeled House! Been developing a new product which I hope to introduce soon. Thanks for the comment.
