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54V down to 49V on switch over (Grid to battery)


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Hi, 

 

I inherited an Apex 5KVA system and am running 4 x 95AH 12V batteries on it. The system charges via eskom and goes up to 54V 'float' I assume, I pretty much left everything on default. 

I have tried to search on the forum for a similar issue but with no luck.  

The query I have is when I test the system or load shedding kicks in the voltage drops straight down to 49,5 volts, then stabilises and runs smoothly for a good couple of hours till eskom feels I can have power again. When the power comes back up it charges itself up to 54V rather quickly. I generally pull 350 Watts on it as it is lights, PC and the TV. 

Any advice would be great. 

Thanks

 

 

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1 hour ago, javadog said:

load shedding kicks in the voltage drops straight down to 49,5 volts

That's around 12.4 V per nominally 12 V module, under load. 350 W is over 7 A at the battery, call it 8, which is almost 0.1C for your 95 Ah batteries. I'm guessing that they're not brand new. If so, that's pretty much to be expected. But if they are new, 12.4 V per 12 V module at light load indicates only about 50% charged.

You'll need to charge them to well over 54 V; 54 V is a "float" voltage, which will keep them full if they are already full, but could take a week to charge them to full if they're discharged. You'll want to see them at 56.4 V (the default absorb or "bulk" or CV voltage) for either several hours, or until the charge current reduces to below 10 A, perhaps as low as 5 A. Otherwise, they are not fully charged.

The large change of voltage when charging surprises many newcomers, and of course with 4 12 V modules in series, the changes are quadrupled.

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Thanks Coulomb. No panels just yet, will tackle that one later in the year where I would ideally like to run everything off the panels during the day and then batteries in the evening. First however have to get approval from body corporate and all that and then the final hurdle; the finance manager, aka the wife... 

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1 hour ago, javadog said:

Thanks Coulomb. No panels just yet, will tackle that one later in the year where I would ideally like to run everything off the panels during the day and then batteries in the evening. First however have to get approval from body corporate and all that and then the final hurdle; the finance manager, aka the wife... 

Tell her it will keep the soapies on while everyone enjoys load shedding ;)

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