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I just moved my 75/15 controller from the portable solar panels (2) closer to the battery as I was getting incorrect info through the app due to losses through the cable.
Now I am getting accurate info through the app but the voltage is not getting to the controller to go from bulk to Absorption phase, again due to losses through the cable.
If I rewire the panels in series this should fix the voltage issue but I'm concerned the lower amps will reduce the charging.
Here is my $.02. The higher voltage will exceed the battery voltage sonner and trigger the charger earlier in the morning and charge latter into the evening. Just what lengths and gauges are we talking? Battery chemistry?
The wiring is standard on folding panels, about 6m long, not sure of actual gauge but was causing issues when the charger was mounted on the solar panel.
The charger was cycling fine but the actual power to the battery was less than indicated so only ever got 80% charged.
The Battery is 300AH LifeP04 so looking for 14.2 to 14.6v to trigger the Absorption phase.
Standard procedure would be to put your 2x panels in series, and even replace the wire with something adequate.
But I don't think this will help anyway. Your 75/15 can only output 15A (~200W at charge V). And the chart shows 1.19kWh, not a bad solar day overall for 15A.
300Ah of Li's with 15A in (& no loads) won't reach Abs V until they're almost 100% charged, and won't show much charge once that is reached. Your "80%" is wrong.
You really don't have enough charge power. Fine if you don't draw down the batts much, but if you do, you'll be counting the charge time in multiples of days, not hours.
Pardon my critical review, but it is as it is.
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My understanding was that as soon as the voltage reached 14.2v this would trigger the Absorption phase.
With the losses I'm not seeing anything above 13.6v.
I will change to series configuration tomorrow & see how it performs.
Worst case I will find some bigger cable to aliviate the losses over the distance.
If your mppt is producing 15A (& not too far from the batts) then you effectively have no losses. And chasing them a waste of time/effort/expense. It can't produce more than that.
I thought the 14.2v during Absorption phase was important for quick charging.
Still learning how this form of electickery works :-)
You haven't said how much solar you have, but given the 75/15 would be a good choice for 200W of panel, let's roll with that.
A common max you might see could well be 12A, then it gets worse off the peak of the solar bellcurve. There was a 206W peak in your chart, and that would be typical too.
A "quick charge" is only important when you run out of daylight in a solar situation. And if you have a lot of batt discharge to replenish then it gets more critical. Li's don't need to be forced to Abs V for a quick charge, and in your case you'll only reach Abs because the batts are full. Li's like a little Abs V just to balance cells.
A handy (simplistic) ballpark figure for solar design is to size the charge A at 10-20% of Batt Ah. You're at like 5% or less. Reaching Abs then becomes the result of attaining full charge rather than the cause of it.
John, I thought it was important that the charger runs through all 3 phases as it was doing prior to moving the controller.
The portable panel is supposed to be 250w but only. puts out around 200.
I have another 120w fixed on the roof through another controller & another 320w on the car available through yet another controller if required.
Generally we should get by with just the 200w as we don't use a lot of power daily but like to have capacity for the days where there's no sun.
