Hi All, I have an Epever Tracer 2206AN MPPT controller, a cheap 160W solar blanket that is not performing anywhere near spec - not my main focus here, but possibly related, and a 12V LiFePO4 200Ah bank and alternately a car battery. The MPPT behaviour is disappointing, I have noticed the panel voltage varying from 14 up to 20V, so the DC-DC converter is working with the panel voltage above the battery voltage. Under clear sky full sun though the panel voltage drops down though, not much above the battery, and therefore providing similar output to a cheapie PWM that came with the solar blanket. The current is similar on either side of the DC-DC converter, i.e. it's not doing much! Could it really be that the max power point for this particular panel is so low, or is this normal for cheap panels or even the MPPT under performing also?
If there is high cloud I have noticed the MPPT running the panel at higher voltage and there is a greater delta over the DC-DC converter, but with only a small drop in light, if the panel output drops below about 1.5A, the MPPT gives up and stops tracking. This is a known issue with the Epever, it behaves like a PWM at low light levels with the panel voltage only just above the battery voltage, same as the PWM controller, and I knew this before purchase, but I wasn't expecting to hit those levels so frequently. It could be that this particular charge controller will work better with a higher power or better performing panel, staying out of that low level give up range! I was intending on connecting a few panels in parallel which is why I got the 20A model, I just wanted to try one first.
I bought the soft folding solar blanket because I need something that is portable and compact when stored for use either with a 4WD or small boat with no space for permanent arrays. The only problem is that I've only gotten 4A out of it, or about 52W at midday with clear sky in full sun. I'm in Sydney, Australia and it's winter which should drop the power a little but surely not that much. It was a fairly cheap model so I wasn't expecting to get all of the advertised power, but I wasn't expecting the performance to be this low.
In full sun the panel isn't that sensitive to orientation, you can have it even up 30 degrees off and not have much drop in power or much change in the MPPT behaviour. This is somewhat of a plus, but may mean that there is some internal limit and I'm not getting all the power from the panels when correctly pointed at the sun.
The panel does seem very sensitive to shading, which I was expecting, but not this much. Shade just a few square cm and the panel output drops from 4A down to 200mA. The MPPT gives up tracking when this happens. I take it that means there are no bypass diodes inside for each cell or group. Is this bad for cell life because the cells are acting as resistors when shaded and heating up with the current from the other cells passing through them?
The readouts on the MPPT (also external screen and PC) match the shunt current readings on the LFP BMS and also a series current measurement with a multimeter, so I have confidence in the measurements.
I have noticed a drop in power output when the batteries reach charge and the controllers throttle back, but with the LFP batteries at mid charge or the car battery with headlights on, I'm sure this isn't the cause of the low power output.
Regarding the panel, I saw similar specs on a number of sites, so I thought it was plausible, but it's quite possible they're all lying! The advertised 23% efficiency sounded a bit high, but at least possible for mono panels. The unfolded length is 140cm made up of 4 panels each about 33x32cm cell area which reveals about 0.42m2 of actual cell area. It's smaller than the advertised dimensions of 1620*355*18mm, so it's possible they sent me the wrong model. From the actual dimensions and 0.0064m2 per watt which is apparently normal for mono panels, that suggests it's actually a 66W panel, which is closer to my measured performance. Using the same formula, even the advertised dimensions reveal about 90W (less for folds) which is still less than the advertised 160W. I'm thinking about returning the solar blanket but I'm concerned about the MPPT.
Can anyone provide an explanation for the above behaviours? Am I missing anything?
Thanks in advance,
Doug
If there is high cloud I have noticed the MPPT running the panel at higher voltage and there is a greater delta over the DC-DC converter, but with only a small drop in light, if the panel output drops below about 1.5A, the MPPT gives up and stops tracking. This is a known issue with the Epever, it behaves like a PWM at low light levels with the panel voltage only just above the battery voltage, same as the PWM controller, and I knew this before purchase, but I wasn't expecting to hit those levels so frequently. It could be that this particular charge controller will work better with a higher power or better performing panel, staying out of that low level give up range! I was intending on connecting a few panels in parallel which is why I got the 20A model, I just wanted to try one first.
I bought the soft folding solar blanket because I need something that is portable and compact when stored for use either with a 4WD or small boat with no space for permanent arrays. The only problem is that I've only gotten 4A out of it, or about 52W at midday with clear sky in full sun. I'm in Sydney, Australia and it's winter which should drop the power a little but surely not that much. It was a fairly cheap model so I wasn't expecting to get all of the advertised power, but I wasn't expecting the performance to be this low.
In full sun the panel isn't that sensitive to orientation, you can have it even up 30 degrees off and not have much drop in power or much change in the MPPT behaviour. This is somewhat of a plus, but may mean that there is some internal limit and I'm not getting all the power from the panels when correctly pointed at the sun.
The panel does seem very sensitive to shading, which I was expecting, but not this much. Shade just a few square cm and the panel output drops from 4A down to 200mA. The MPPT gives up tracking when this happens. I take it that means there are no bypass diodes inside for each cell or group. Is this bad for cell life because the cells are acting as resistors when shaded and heating up with the current from the other cells passing through them?
The readouts on the MPPT (also external screen and PC) match the shunt current readings on the LFP BMS and also a series current measurement with a multimeter, so I have confidence in the measurements.
I have noticed a drop in power output when the batteries reach charge and the controllers throttle back, but with the LFP batteries at mid charge or the car battery with headlights on, I'm sure this isn't the cause of the low power output.
Regarding the panel, I saw similar specs on a number of sites, so I thought it was plausible, but it's quite possible they're all lying! The advertised 23% efficiency sounded a bit high, but at least possible for mono panels. The unfolded length is 140cm made up of 4 panels each about 33x32cm cell area which reveals about 0.42m2 of actual cell area. It's smaller than the advertised dimensions of 1620*355*18mm, so it's possible they sent me the wrong model. From the actual dimensions and 0.0064m2 per watt which is apparently normal for mono panels, that suggests it's actually a 66W panel, which is closer to my measured performance. Using the same formula, even the advertised dimensions reveal about 90W (less for folds) which is still less than the advertised 160W. I'm thinking about returning the solar blanket but I'm concerned about the MPPT.
Can anyone provide an explanation for the above behaviours? Am I missing anything?
Thanks in advance,
Doug
