Question About State Of Charge

[AL1952]

While I am not familiar with the Renogy Rover it looks like an MPPT type CC. Maybe someone else can comment on its' quality.

I've decided on the 40a MPPT Renogy based on a lot of great comments and reviews, and on the size of my upgraded system. Should I fuse my new system the same as the old? With 600 watts of panels, 280 amp hour 12 volt battery bank, and a 900 watt inverter how large should my fuses be from the panels to the SCC. (currently using 30a) From the SCC to the batteries (currently using 30a), and from the batteries to the inverter (currently using 100a). Am I on target or do I need to change any of these?

[inetdog]

Some PV panels in the past, required positive ground. Some systems that provide electrolysis protection for remote underground pipelines, require positive ground.

But generally, negative ground is much more common.

The problem with some earlier design panels (otherwise reliable and high quality) was charge migration between the PV junction in the cells and the supporting substrate. A slow buildup of charge eventually cut the cell output nearly to zero. A few days connected with positive ground would restore the panels to normal operation. I am not aware of any current panels that have this interaction.

[Sunking]

Should I fuse my new system the same as the old?

Maybe, maybe not. Most likely you can throw them away as you likely had no use for them on your old system, nor likely needed for the new system. your old or new system. Over Current Protection Devices are only required if you have 3 or more parallel panel strings. Otherwise not needed or required. So if you only have 1 or 2 strings of panels, no fuse required or needed.

If needed, DO NOT ask anyone here what size to use as that is foolish. The manufacture provides you with that information as part of their specifications. If the manufactures gets it wrong, they pay for damages and have deep pockets. Take someone else's advice like a DIY, you get laughed at if the guess goes wrong and you end up paying.

[PNjunction]

Thing is, we *still* don't know what AL1952's actual load is!

So AL1952, how much current does all your gear pull, and for how much time?

What it sounds like to me based on post #1, you either have waaay too much load current from your devices and the batts, even if healthy are simply dropping like they do when Peukert effects raises it's head with the massive voltage drop.

Either that, or your old batts are just worn out / sulfated, and have much less capacity than you originally had.

Before buying any more stuff, can you install a current-meter, or even invest in a dc-clamp-meter, turn on your gear after a full charge, and take a reading of how many amps are being drawn at one of the battery terminal connections?

This will let us know if you are simply hammering your batteries right from the start with too much demand, even if they were in perfect health. You may also have a dangerous infrastructure problem developing from loose / poor wiring and interconnects.

THIS is where one starts - measuring your need, ie a "power budget". Then you can make educated purchases - otherwise, you are just throwing darts and wallets against the wall.

[Mike90250]

Speaking of power budget, on days with close to the same temps (refrigerator loads) and if the watering schedule was the same, my load and harvest almost are the same. A couple days ago, my main water pump only ran a few minutes longer than the adjacent day, and my daily harvest and recharge was almost identical. This seldom happens and when putting stuff in the spreasdsheet, I saw the data was nearly the same. Close enough I had to double check. So it can be very repeatable.