Ideal charging voltage setting

TEV said:

uxcell 2Pcs Aluminum Case Resistor 100W 1.5 Ohm Wirewound Yellow for LED Replacement Converter 100W 1.5RJ: Amazon.com: Industrial & Scientific

uxcell 2Pcs Aluminum Case Resistor 100W 1.5 Ohm Wirewound Yellow for LED Replacement Converter 100W 1.5RJ: Amazon.com: Industrial & Scientific

www.amazon.com

you could try two of those in parallel, instead of the light bulb, it will make a 0.75Ohm/200W resistor, that will gave you 0.75x14=10.5V drop on a 2P2S configuration of your panels, but also will use up to 150W that will be transformed in heat, so you may need to put them on a heatsink.

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sunshine_eggo said:

Resistors only drop voltage proportionally when there's a current flow. The 2S array will still report 2X Voc even with the resistor in place.

V = I * R

If I is 0 or very small, I * R = very small number.

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sunshine_eggo said:

Resistors only drop voltage proportionally when there's a current flow. The 2S array will still report 2X Voc even with the resistor in place.

V = I * R

If I is 0 or very small, I * R = very small number.

Click to expand...

dsdc said:

Alright, decided to not go with the bulb route.

This morning, it was snowing here, still 2 Celsius, and sunny shortly after the snow stopped. (WA weather)

The Voc I tested on the array became 63.7. While I wait to get that panel you mentioned earlier, I decided to see what will happen if I remove 1 panel from 1 of the strings. I had a 2S4P (see attach) setup of 8 panels. and now its 2S3P + 1 more string with just 1 panel

The result was that the voltage dropped to 35.7 when I tested after making the change. Now... is this kinda what adding the amazon panel to each string is trying to achieve? Is the way I got now safe?

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TEV said:

I hope that you didn't left that one panel in parallel with a string of two in series for too long.

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dsdc said:

Alright, decided to not go with the bulb route.

This morning, it was snowing here, still 2 Celsius, and sunny shortly after the snow stopped. (WA weather)

The Voc I tested on the array became 63.7. While I wait to get that panel you mentioned earlier, I decided to see what will happen if I remove 1 panel from 1 of the strings. I had a 2S4P (see attach) setup of 8 panels. and now its 2S3P + 1 more string with just 1 panel

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dsdc said:

The result was that the voltage dropped to 35.7 when I tested after making the change. Now... is this kinda what adding the amazon panel to each string is trying to achieve?

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dsdc said:

Is the way I got now safe?

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dsdc said:

Tested a bit, why?

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TEV said:

And how many watts did you got in that configuration?

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sunshine_eggo said:

You can't do this. all strings in an array must be similar Voc/Vmp. Rewire to 1SXP immediately.



No.



No.

The goal was to achieve MPPT voltage. One of your panel + a 20Voc 120W panel would put you in the mid 50s at cold temps. You will need one 20Voc/120W panel per string to pair with one 180W panel.

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dsdc said:

Yeah they were wired like that for about 5 minutes, I now have just 4P. It is charging at around 60-120W depending on the sun right now.

I'm thinking to just get new panels in the attachment, can you take a look at it and double check if I am making any mistake again

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sunshine_eggo said:

Is the battery LFP?

If so, 3.55-3.65V/cell will charge the fastest (generator)
3.45V/cell will take notably longer, but it will be a little less stressful to the cells and possibly result in longer cycle life (solar or grid charging).
3.40V/cell float

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bralee886 said:

Suggestions on charging this battery? https://www.amazon.com/gp/product/B08N56CYS5
I have a NOCO Genius 5 that charges @ 14.6V on Lithium mode. Is it worth buying a victron smart charger?

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