Practical maximum charge current vs PV array Isc

kevinhjones

I have an array that produces 90 amps short circuit (Isc) during maximum light conditions.  As a rule of thumb, what would be the most current I could expect to be able to be delivered to the battery bank that is discharged to 50% charge?  I am assuming that it would be somewhat less when actually delivering current through the bank.

The array is made up of varied panels and are old, and I don't have access to PV curves, but I would just like to just get some ballpark idea of roughly what percentage of Isc can actually be forced through an average bank.

mike95490

The amps delivered varys according to the battery internal resistance.  AGM will, under same conditions, will recharge much faster than FLA because they have 1/10 of the internal resistance.  That last 10% of charge still takes a long time.
 The forcing part depends on the voltage you set, 14V will be much slower than 18V

BB.

Use Imp as the maximum charging current... You may get a little more, but not much. Isc is driving into a dead short. Imp is driving into a optimum load voltage (like ~18 volts Vmp for a "12 volt" panel).

It does also depend on the type of solar charge controller. PWM charge controllers pass (pretty much) Imp-array current.

For an MPPT type charge controller, it is a bit more complicated, but it is the power of the array (actual wattage), then Ibatt=Parray/Vbatt.

-Bill