Does it make sense to switch bank to 12v (par) fr 24v (ser) for dim light charging??

[stoneskipper]

Never thought about this until I was staring at it ...
Example: System has 2 x 12v AGMs in series: Batts(1 + 2) = 26V & PV is still making 25V (late in the day, say).
1. Am I wrong to think charging will stop in this situation? Or can that voltage still make useful current?
2. If charging HAS stopped, can I still charge the batts if I switch them @ this time to parallel from series (and reset the controller to 12V)?
So do I sound like one of those guys who doesn't know what he's talking about lol? Help! there's a hole in my understanding!

 

[rmaddy]

Is this an MPPT SCC?

When you are seeing 25V at the end of a day, how many amps or watts are you seeing. 25V at 0A won’t do you any good.

 

[sunshine]

Or can that voltage still make useful current?

You are looking at Voc: Voltage@ open circuit under those light conditions.
Where there is voltage some current will result if load is applied. However as soon as this is done, the V will drop significantly depending on amount of load and wattage will be insignificant.

I have a row of 12v 6w led lights directly connected to a panel over my fish tanks. The first few start flickering on at 6v at about 4.30am when there is just a very faint glow. The V drops leaving only one light on @ about 3v. All the lights come on progressively as the sun appears.

There is another user that makes CCs specifically suited to use very low current in low light situations to run instruments...

 

[stoneskipper]

You are looking at Voc: Voltage@ open circuit under those light conditions.
Where there is voltage some current will result if load is applied. However as soon as this is done, the V will drop significantly depending on amount of load and wattage will be insignificant.

I have a row of 12v 6w led lights directly connected to a panel over my fish tanks. The first few start flickering on at 6v at about 4.30am when there is just a very faint glow. The V drops leaving only one light on @ about 3v. All the lights come on progressively as the sun appears.

There is another user that makes CCs specifically suited to use very low current in low light situations to run instruments...

Thanks .. Sorry for the delay, October is a busy month prepping for winter lol I'll get back after my last out-of-town job next week. In the meantime It'll allow the system to charge w/o load a few days and I'll have a better idea of what 'max' is for the batteries, which are a little old.

 

[stoneskipper]

Is this an MPPT SCC?

When you are seeing 25V at the end of a day, how many amps or watts are you seeing. 25V at 0A won’t do you any good.

Yeah, MPPT (Epever TracerAN 30A) Thanks .. Sorry for the delay, October is a busy month prepping for winter lol I'll get back after my last out-of-town job next week. In the meantime It'll allow the system to charge w/o load a few days and I'll have a better idea of what 'max' is for the batteries, which are a little old. It does seem than low loads do come off the sunlight @ these times, rather that storage. I'm just being persnickety bec where I live, winter sun is weak -- Central PA mtn ridge w/ some shade & the opposite ridge cuts my days a little short, but I still get 1-2 hrs of predictable 'twilight' most evenings I'd like to get the most out of.

You are looking at Voc: Voltage@ open circuit under those light conditions.
Where there is voltage some current will result if load is applied. However as soon as this is done, the V will drop significantly depending on amount of load and wattage will be insignificant.

I have a row of 12v 6w led lights directly connected to a panel over my fish tanks. The first few start flickering on at 6v at about 4.30am when there is just a very faint glow. The V drops leaving only one light on @ about 3v. All the lights come on progressively as the sun appears.

There is another user that makes CCs specifically suited to use very low current in low light situations to run instruments...

That's interesting about the lights, how are they wired? & have you ever over-loaded an LED btw?

 

[sunshine]

That's interesting about the lights, how are they wired? & have you ever over-loaded an LED btw?

The lights are OSRAM MR16 VAL 6w Daylight, Available at Bunnings (Oz Home Depot) within the usual bulb section.
#1 was just in series with a panel (converted house panel giving 20Voc)
#2 Switched on by a VHM-009 Low/ high battery protection device on the battery side of the pwm that turns on a 12v automotive relay that completes the circuit from the led back to the panel (needed for isolation). The VHM-009 comes on at 14.4v and turns off at 12.6v..this was when I only had a couple of panels. Even though battery voltage is read the led lights still only run direct from panels.
#3, #4,,,various other ways

There are a few 12v halogen bulbs switched. However these are on the battery side of the pwms -the higher direct voltage burns them out.
The life of these leds seem unaffected by the voltage range 0-20v. Interestingly they come on reasonably bright at 6v and stay on after the little voltmeter has gone out at 2v

For 'clarity' see the photos