question

Hi!

I have a few questions: Were you measuring the short cuircuit current when you had the 5 amps? What do you measure, when the controller is connected? Do the measurements from the controller and the ones of your multimeter match?

Not reaching the peak voltage is normal, especially in a hot area such as yours. Have you investigated the most suitable setup angle for your panels in your area?

Regarding the charging current, from your screenshot I can see that you already have a battery voltage of 13.3 V and start floating at 13.6 V. My controller starts lowering the charging current at 13.3 V, presumable to protect the battery health and doesn't take the max from what it could. Discharge your batteries further or increase the floating voltage to get more current at this point.

Best regards

Simon

Measurements:

I removed the solar leads from the MPPT to do the measurement, then re-attached and took the screen shots.

I actually took them from 3 points in the solar wire change. Right after the panels and before they go down into the rv, then the cutoff switch, and then right at the connection point of the MPPT. All were the same voltage and amps.

If I measure on the screws that hold the wires in on the MPPT they are matching what the screen shots show. Thus my confusion.

Raw wire voltage and amperage is NOT the same as after they are attached to the posts, and what is shown in various monitoring screens.

SOC on the batteries was down to 61%. These are lithiums, so not a whole lot of change.

Charging state is showing Bulk.

Panels are on an RV, so not much I can do with angling them.

Outside temp was 82F when I did these measurements @ ~11am

I was using a Renogy Tracer 40 before the change to the Victron and Lithium batteries. I was showing 380-400 watts regularly before the swap.

Hi, 61% seems pretty low, but the controller might still limit the current at 13.3 V there. I have no experience with lithium batteries.

If they were not connected to the controller, what where they connected to? You can't measure the amps without a load, you'll only get a short circuit current, which doesn't tell you what it could do with load. Amps are "pulled" by the load. You'd have to measure the current in series to the load, e.g. put your multimeter inbetween the plus cable right before your controller input. With load, the voltage drops, as well.

Thanks!

Things like the difference the load makes is what I was hoping to learn (that it mattered while measuring).

I went out and measured right off of the terminals on where it connects (the screw terminals) while everything was connected.

Voltage readout on the Victron App was identical to the MM - in this test it was 82.59V.

Amps were different. I was reading 4.1 on the MM and only seeing 1.3A on the app.

Even more interesting. After a few minutes the voltage dropped to 60.22V and amperage went to 3.4A, but I was only reading 2.1 amps on the MM.

So the voltage is pretty dead on but the amperage is either high or low by 20-25% swings.

I am still trying to figure out why I have such low wattage - it looks like the amps are the issue. The batteries will not fully charge today. They should with 500 watts of possible power. After most of the day they are still only at 88%. Granted, I have had the MPPT disconnected and reconnected several times for about 1/2 an hour, but they still should have charged from 61%.

No clouds and temps in the low/mid 90's all day. Shadows are starting to cover the panels.

Head scratching and trying to figure out what to do.

I have read/scanned through your post and was hoping to get some further clarification about your concerns and also how any external measurments have been conducted - in order to better understand the behaviour and your comments.

But some feedback in advance;

1- Could you provide a simple wiring diagram sketch or photo showing exactly how you measured PV voltage and current?

I am am confused about your statement that PV current was measured while the PV wiring was disconnected from the MPPT, as there would be no current in this state since the PV is not under load.

The PV voltage can be effectively regulated between the Voc (at the solar & temp conditions at the time) and 0V depending on the load that the MPPT applies to it. Somewhere in that range there will be a 'sweet spot' where the product of V x I = P is maximised - this is called the Maximum Power Point (MPPT or Pmp)

So when you were measuring current, did you actually complete the circuit back to the MPPT and just insert the multimeter in series with one of the PV cables OR did you effectively 'short circuit' the PV by directly measuring current by connecting the multimeter leads to both PV cables? (which would result in PV voltage = 0V)

2- The Pmp can also change quickly depending on solar condition, so the MPPT will always aim to be operating at the optimal point and periodically check to see if a better point exists.

So if you are ever conducting any external measurements / comparisons they would only be valid if they were measured simultaneously (with the PV cables connected to the MPPT and the MPPT controlling the load to optimise the power (not just voltage or current in isolation of each other)

3- It is unrealistic to expect close to max rated PV power, just because the sun is out. During overcast / winter times you might only get ~10 to 20% of max power. With fairly good sunlight and a semi clear day you might get ~40 to 80%. To get ~80 to 100% it really needs to be a near perfect day with very strong sun, clear sky and not excessive temperature.

Another point to note with wiring many panels in series is that if one panel or even one cell is even partly shaded then it can have a significant negative impact to the max power of the total array.

4- The MPPT will only operate at the mppt point when it needs to increase the battery voltage to the setpoint configured. So this would be always during bulk phase and also during absorption or float but ONLY if the voltage has dropped below the setpoint / target voltage for the particular charge stage.

When the battery voltage has reached the setpoint then the MPPT will purposly limit both the PV power and accordingly the charge output power to maintain the voltage setpoint, otherwise the battery voltage would just keep rising.

5- If you are having trouble achieving 100% SOC, it could be due to insufficient PV to BOTH recharge the battery AND power loads &/or MPPT charge settings &/or the BMV configuration.

It may well be that the SOC % as indicated by the BMV has 'drifted' away from the 'true' battery SOC % and that it has not been recently synchronised. There are various parameters in the BMV configuration to enable it to better track the 'true' SOC % and also enable it to synchronise periodically when the correct conditions present.

6- MPPT charge output / power can go fully to the battery or directly / fully to loads and any combination in between. So unless you have absolutely all loads properly disconnected (even the CCGX / monitoring equipment has a current draw), then don't expect the MPPT charge output to perfectly match what the BMV is measuring as flowing into to battery.