Hi guys, I am new to the forum and would be grateful for some advice. I have recently had to upgrade one of my solar systems. I have had a gas fridge installed at this particular lodge for a number of years but as there are no local repair agents for absorption type fridges (Rustenburg, South Africa), I have purchased an electric one. AEG - S53620CTX2 A++ rating with the label indicating consumption at 117 watts. There is also one alarm system installed, one electric fence energizer and 9 x 6w LED lights. Guests will make use of daytime charging of cellphones but are requested not to use this at night. My installation consists of the following 2 x 235 w Jinko panels and 2 x 265 w Amerisolar panels. I have connected 1 x 235 w and 1 x 265 in series and then coupled the 2 in parallel to feed the invertor, Mecer SOL-I-AX-3MPLUS24. For storage I have 2 x Omnipower OPS260-12 connected in series, approximately 2 years old. There is no Eskom supply  and I have no other hardware connected. I completed the installation on Thursday and it appeared to run okay when I checked on Friday, I adjusted the thermostat on the fridge to the suggested Eco setting, the guests phoned this morning to say the invertor had tripped but they were able to reset it and normal power resumed. I am assuming that the invertor switched of due the battery supply reaching it's 50% threshold. Can anyone out there let me know if I should increase my storage capacity or would it be better to put an appliance timer on the fridge to switch off at say 21h00 and on again at 06h00. The fridge has a claimed rising time of 18 hours so I assume food quality will not be compromised over a 9 hour period.  Any help or comments would be greatly appreciated. Thanks and Regards, Giles

HI Giles

Welcome to the forum.

I am guessing but I think the alarm and fence energizer could be drawing more than you anticipate. Looking at the budget for overnight use.

5 hours of LED lights = 270Wh

12 hours of fridge = 702Wh

Alarm (guessing 40W) = 480Wh

Energiser (again guessing) 25W = 300Wh

Total = ± 1800Wh

50% of a 24V 260Ah battery bank  = 3120Wh so you are not exceeding 50% capacity. Are you batteries still 260Ah? After 2 years you may have more reduced capacity than you think.

Hi Chris,  Thanks for your response. The batteries are my worry, I understand that they should sometimes receive a boost but was led to believe that this was not necessary with AGM Gel batteries, have I got that wrong, if so how would I do that?. At nearly 5k a pop I am reluctant to replace and I am guessing that by adding more to the bank, the older batteries would drag the newer ones down? The quick fix is to put a R300 appliance timer on but that is not really fixing the problem. Even in overcast weather the batteries appear to become fully charged by 10h00 and there seems to be sufficient panel power to run the fridge until sundown when the batteries take over. Is the 50% I have set a realistic figure or should I be higher or lower than that? It could be that the guests plugged in some additional appliance but very unlikely as I specifically asked them not to. In terms of the installation am I missing any hardware that would better protect it?

 

2 hours ago, Giles said:

I understand that they should sometimes receive a boost but was led to believe that this was not necessary with AGM Gel batteries

You definitely DO NOT equalize (boost charge) an Omnipower battery as this will causing gassing and loss of electrolyte, AGM batteries are sealed and the electrolyte is not replaceable.

The problem that you may have is that the OPS 260-12 requires an initial charge current of 30amps (recommended 40amps, max 50amps), if the initial charge current is lower than 30amps it results in sulphation according to the Omnipower battery supplier (Sinetech).

Your off-grid Axpert system will start start off each morning by using PV to supply the load with any excess required being supplied by the battery, as PV input increases through the morning then the system will gradually take over the battery input and start to charge the battery with any energy available over the load requirement. This could start at 1 amp and increase with PV power input - but definitely not an initial current of 30amps.

It is for this reason that I don't believe that OPS (now OPR) batteries are a good solution for PV systems (others may differ).

Thanks Chris and PF, I changed the temperature setting on the fridge to 6 degrees which is slightly higher than the eco setting, this seems to have made a difference and the guests reported no problems after that was done. I bought a R125 plug in timer and I think I will set the fridge to run from 06h00 through to 21h00. I am sure that the guests are unlikely to open and close much during the "off" period. As a matter of interest is there any hardware I should add to my system to improve it?