New to Solar, Some Questons?

I think the way it works (somebody who knows for sure can help here)

The 24v panel needs the MPPT controller in order to convert back to 12v for a 12v battery being charged. Amps to that battery will be about twice the Isc of that panel.

The 12v/24v controller is first supposed to be connected to the battery. This lets it little brain figure out what kind of battery it is, 12 or 24. If it is 12v, the controller will operate in 12v mode. If it senses 24v battery (voltage is above 17) it will operate in 24v mode.

Then you connect the array side.

So you have a 24v battery, a 24v panel, and the controller is in 24v mode. I think ??? you will get Isc more or less, but that will be ok to charge the battery which runs the motor because it is at 24v; it only needs "half the amps" get a recharge that a 12v battery would need for a recharge.

----actually I don't know that at all!! What does go on for recharging a 24v battery? (I know if it is two 12s in series, you can put a 12v charger on each battery, or one 24v charger across both--but what are the amps?)

Old & Slow wrote:
I don't know a darn thing. My new 24v/120w panel says: 120Wp/1kw squared AM 1.5/ OOV 3.43.v /OOC 3.78a

As I see it I'm dissapointed.

No reason to be dissapointed. You are charging a 24v battery right?

24v volt system will always be half the amps for the same power (wattage).
Actually makes things more efficient.

BFL13 wrote:

Old & Slow wrote:
I don't know a darn thing. My new 24v/120w panel says: 120Wp/1kw squared AM 1.5/ OOV 3.43.v /OOC 3.78a

As I see it I'm dissapointed.

No need to be. With 24v panels the Isc is half a 12s. (roughly)
The MPPT puts it back to 12v on battery from 24v panel--amps double--now you are good again :).

Sort of like that.

So my MPPT is good for my 24v motor on the scooter and can also work with an 12v batt? ~ my panel is 24v

Old & Slow wrote:
I don't know a darn thing. My new 24v/120w panel says: 120Wp/1kw squared AM 1.5/ OOV 3.43.v /OOC 3.78a

As I see it I'm dissapointed.

No need to be. With 24v panels the Isc is half a 12s. (roughly)
The MPPT puts it back to 12v on battery from 24v panel--amps double--now you are good again :).

Sort of like that.

If your MPPT controller works, it will do well for you and Isc does not matter in your case. Do you have any ratings listed for Voc, Vmpp, and Isc?

Jim

I don't know a darn thing. My new 24v/120w panel says: 120Wp/1kw squared AM 1.5/ OOV 3.43.v /OOC 3.78a

As I see it I'm dissapointed.

BFL if that really matters to you look at Unisolars. My 68w panel is rated at Voc 23.1v yet Isc is 5.1. A lot more Isc per watt than you generally see.

It's not really a low Voc that gets you good PWM current, it is a low Vmpp - one that is close to but above the battery voltage you want. Vmpp on these units at standard test conditions is 16.5v. Vmpp is pretty much the last voltage where you make decent amps. Go much higher in voltage and amps collapse very quickly on the IV curve.

As actual (under real conditions of temperature, light intensity, light angle, and atmosphere passed through - not the STC ratings) Vmpp approaches the battery voltage under charge, PWM approaches or even passes MPPT yield. The further real Vmpp is from the current battery charging voltage, the farther the PWM voltage is from the current panel max energy output, and the more benefit MPPT gives.

Jim

1. Another curiosity where the Voc is high and the Isc is low. In this case (and ISTR others) the diff is with Mono vs Poly.

100w (OP's mono) 22.5v Voc, 5.75a Isc
100w (my poly) 21v Voc, 6.3a Isc

Since it is Isc that you have as expected max amps, which panel would you prefer for PWM operation?

(other sizes of poly panels have similar proportions of Isc per watt with 21v. eg, 130w and 8.2a Isc)

2. 10a controller is right size IMO allowing for margin above Isc as usually recommended for choosing controller and fuse size. (There is a 7a 105w limit rated controller often seen, but that would have little margin)

I ordered a little different one from: EBay/ lu_cytime208 Led digital 20a PWM $16.98 air mail from HK. We'll see how ordering from HK works out.

O&S

Hmm BFL is right mine does not have numbers either. Not the same unit.

It looks like the kit actually came with This unit.

Now to find a manual.

Manual for EPRC-ST street light controller

Jim