Off Grid CS6P-250 x 14 panels

[marrp]

We have inherited an old Canadian PV system with a small holding in East Anglia UK. The present setup comprises 14 panels, each CS6P-250 type. Wired 7S2P to a junction box on panels, then fed to MPPT epever ET6415BND 60 Amp controller. 8 batteries in 4S2P configuration, each 115 AH 12 volt. Inverter Pure Sine Wave power inverter unbranded.
Panels read 110 volts at the junction box and 107.5 volts at the MPPT controller terminal ( Via isolator) This was tested in the morning in bright sunlight but only at 4 degrees C. Previous reading Full midday sun October 22nd sunshine gave 136 volts at the junction box on the rear of panels.

Batteries are 2017 and read 8 volts at best. MPPT is not powering up and is possibly dead due to a lack of ventilation in the shed where housed ( Hot summer in 2022 would have reached over 40 degrees C ) Or could be Voc breaching 150 volts?

Load is only a small shop with a total of 10 LED lights, a till, and a weighing machine. Some power at socket outlets is needed to charge phones and mobile camping lights for the evening—maximum load 500 watts which would be required in low light conditions or evening for six hours.

My questions/queries are:

14 Panesl would appear an overkill at present.
Voc may approach 150-volt maximum .( Given a winter sunny morning at minus 5 Degrees C ), Thus killing MOSFETS?
The battery arrangement seems too light, given amount of panels.
If I charged the dead batteries charged at home, could I at least prove the rest of the system works prior to spending more than 2000 pounds on new batteries? Or is it like inheriting a stately home, which will cost us more and more every year?

The picture shows the shed contents as inherited.

Does anyone have any good advice please
Marrp

[Bala]

I doubt the batteries will be any good but you can put them on a charger and see how they come up.

For controllers always ensure battery is connected if solar input is on. Some controllers will be damaged if they have solar input and no battery connected.

To test the system disconnect the inverter and panels, use any good 12V battery and connect the controller, if it does not automatically select 12V do so.

If your controller seems ok switch on just one or two panels to see if the controller is charging the battery.

You will then know if your controller and panel system is working and can decide from there what to do next.

[Ssas]

8 volts for Pb battery - it seems that they are only good for recycling.

I have the same panels, wired 6S2P. Optimum MPPT voltage is around 180V (at 24°C) and Voc is 250V.
It seems that 150V is max for your controller so I guess it can be burnt if it is wired as you wrote. Or you mean 2S7P?

>The battery arrangement seems too light, given amount of panels.
It seems OK for me.

[marrp]

Hi Ssas Thank you for your mail. Having looked again at the current setup, I am now aware that only 12 panels are wired to the Epever 60 Amp MPPT controller. These appear to be wired as 4 parallel strings of 3 ie 3S4P, with an optimum voltage of around 90 volts and Voc 111 volts. The batteries are presently 4S2P giving 48 vdc 230 AH. The inverter spec states that the 4KW unit battery capacity must be greater or equal to 160 AH at 48VDC. Load being only a small shop with a total of 10 LED lights, a till, and a weighing machine. Some power at socket outlets is needed to charge phones and mobile camping lights for the evening—maximum load 500 watts which would be required in low light conditions or evening for six hours.

Have been looking at some 160AH deep cycle batteries which would be wired 4 in series to give 48 vdc at 160AH. In the UK they are around £300 per battery. Any comment regarding the planned arrangement would be truly appreciated Thank you.

[Ssas]

That means ~11kWh battery, which seems reasonable size.
The inverter recommendations are for full inverter load. If your load is only 500W then 11kWh Pb battery is enough, at least for 11 hours (double the hours if you use LiXX chemistry).

Regarding the batteries I am not of much help. I use Pb batteries only if I get them for free (or near free). Otherwise I go for LiFePO4.

[marrp]

Hi Ssas Thank you for your mail again. I appreciate your input. Not yet purchased the batteries so will look at LiFePO4 type as well. Will keep you posted when we test the system.

[marrp]

The batteries were fitted yesterday. So far, all is looking OK. In mixed cloud and a little February UK sun, we read 88 Volts from the solar panels and maintain the bank of 4 series 12 v 200 Ah batteries around 51.5 volts.
SOC is low at 60%, so hoping for some sun today to top up. We have switched off all but lights, a till and scales in the shop. Will report back in a few days Thanks to all who helped. This is a very good site for building up knowledge