viceroy

When connecting batteries in series, you add up the voltages, so 4x 12V 105Ah batteries gives you a 48V 105Ah string. When connecting batteries (or strings) in parallel, the voltage remains the same, but the Ah increases., so 2x 48V 105Ah gives you 48V 210Ah. Not recommended to go with more than 2 strings in parallel. To get the really big Ah capacity battery banks, the easiest way is big Ah batteries with low voltages, so a single string of 24x 2V 500Ah batteries = 48V 500Ah in a single string.

It's either 12V * 210Ah or 24V * 105Ah, depending on whether the batteries are connected in series or parallel. Regardless though of how they are connected, they still contain the same Wh, ie. 2520. Question 2. You would add another string of 2 batteries that are identical to what you have now. The new batteries would be connected in parallel to your current string (which are connected to each other in series btw). Question 3. With a 5kva inverter, you would be able to supply 5kW of power to devices, ie. 2x 2.5kW kettles, or 5x 1000W microwave ovens. Your batteries determine how long you can power the load for. Having 8x 105Ah batteries would give you a total capacity of 210Ah @ 48V (2 parallel strings of 4 batteries (connected in series)) which is 10080Wh total. You shouldn't really be drawing more than 50% of that if you want the batteries to last, so 5040Wh. With 5040Wh, you can power 5kW of devices (remember the 2x kettles, or 5x microwaves) for 1 hour, or you could power 1x microwave for 5 hours, or you could power something using 350W for nearly 14.5 hours. Not answering the other questions as they have been answered already.

Basically interlocked change-over switch, physically disconnects one source before connecting the other. Safer, with almost no chance of failure in such a way that both sources are connected. Reverse flow blocking relay, doesn't really disconnect either source, but rather blocks flow from one to the other. Less safe, and a much higher chance of both sources being connected in the case of a failure.

It is something to consider, but in my house, aside from the stove and geysers, the only circuits still in the main DB powered only by grid are the kitchen counter, and garage/patio. The loads applied to these circuits all high amp draw and/or inductive, and I don't really want these with a direct connection to the Axpert. Can you imagine, the gardener cutting the grass, while at the same time the maid has the dishwasher going, the washing machine going and needs to heat something up in the microwave. The poor Axpert is going to switch to bypass mode, or just trip (if bypass disabled). Yes, I know it's a bit of an exaggerated situation, but one entirely possible, and despite being more expensive, a hybrid inverter solution would simply add grid power to assist the PV. The Axpert wouldn't know about any excessive loads, and everyone would be happy. If loadshedding happened, a DC transfer switch, would move PV over to the Axpert, and again, everyone happy.

It would be great if you could provide a list of parts you used to achieve this?

About the most comprehensive answer I got was along the lines of: The negative has the same potential as the positive, and even with the positive disconnected, its possible to have current flow through the negative (in a problem situation), so better to fuse both than just the one. While I haven't done it just yet, I am going to install my second fuse onto the negative cable. Rather safe than sorry.

I may actually be over complicating things too. Doing like you suggest, and leaving the panels on the hybrid inverter, I'd still essentially be charging the batteries from solar. Only if the grid goes down, would I then move the panel output to the Axpert if required.

No, as the system stands now, the batteries are fully charged by 11am, from that point on, the essential loads are drawing maybe 200W until the kids get home at 4pm and start using computers, tv, etc...quite a waste I think. By switching the panels over to a hybrid inverter at the point the batteries are charged, their power will be blended with grid power, but giving precedence to the panels, in effect allowing me to maximize their use during the day. Yep, from when I was looking at the various hybrid inverters, their startup volts seem to be around 100/120V while my current string configuration is between 85 and 95V. So you are correct that, I'd need to reconfigure the string to provide higher volts, and get a separate MPPT charger. --edit-- I see the Kodak i2.5 has a startup voltage of 60V, but nominal is still 250V, and I don't see any locally.

At the moment, yes, the panels are only charging the batteries and running the critical loads, and yes, critical loads are off grid, although the Axpert will switch to grid if the batteries get below 40% (setup in ICC). Together with the gas stove, and evacuated tubes for the geyser, it's working well...BUT...once the batteries are charged, the panels are 90% wasted during the day, and I've also started investigating adding a hybrid inverter. My first thought was to split the panels between what I have and the hybrid inverter, but this solution is inflexible, and at times wouldn't fit my needs. Seeing your post and the possibility of switching the panels between inverters really appeals, as I could have 100% of the panels dedicated to the grid tied inverter while the batteries are being charged, and then switch them over to the hybrid to run the house for the house for the remainder of the day. Could also get a bit more complicated as I'd also want to bypass the grid-tied inverter and run all loads through the hybrid inverter during the day, making as much use of the panels as I can. There seem to be a few automatic switches locally, but I'm not sure at the moment if all or any would be totally suitable. http://www.giga.co.za/ocart/index.php?route=product/product&product_id=423 <- drop shipping https://www.epicsolar.co.za/Items/Transfer-switches-and-DC-distribution https://www.atisystems.co.za/electrical-enclosures/normand-automatic-manual-transfer-switches-ats-mts <- actually looks like it could do the trick

Hi, Yes, a DC transfer switch would be what you are looking for, simplest (cheapest too) being a manual switch, and then an automatic being more ideal, albeit at a higher cost. Who told you this? Most residential installations of Axpert inverters have it connected to the DB board. In my setup, I have a main DB which contains breakers for all the non-essential loads, and this feeds through to a sub-main DB, where I have breakers to and from the Axpert, as well as an AC changeover/bypass switch, and then all the essential loads which are normally powered from the Axpert. This is the main DB, please excuse the gaping hole. Pic was taken during installation. This is my second DB which is connected to the Axpert.

Thank you @Wilfred. This has been a constant learning experience for me, and something I'm enjoying doing.

Watched this video last night pertaining to how long lithium batteries last, and some tips to extend that life.

@desiji, @ChristoSnake What is your daily DOD? I'm trying to keep mine above 40% daily in the hopes that this massively extends the cycle life of the batteries.

This may not work for you, but I've set 16 (Charge Source Priority) to OSO, basically only solar can charge the batteries.

If you want to do it properly, get a BMV702 (BMV 700 is slightly easier on the budget) Wonderful little device to monitor the SOH (state of health) of your batteries, and can be set to trigger a relay or alarm at whatever DOD you set. Otherwise what @Coulomb has suggested will work fine provided you aren't pulling big loads from the batteries which may trigger false positives when the voltage dips below the set threshold.

I hate to say this then, but you may have a faulty battery. If I were you, I'd get it checked out by the supplier. You may have a faulty cell which when put under load drops volts and triggers an alarm.

Sold.

I too have started down this road. Bought a few Sonoff smart switches at the beginning of the year. I want to install them on the fridges and freezers, so they can turn off between 10pm and 6am in order to save power. I may also flash them, and get the ICC power management module so they can also power off devices when batteries get too low etc. Haven't quite gotten to Google home devices throughout the house, or light switches and bulbs, but it will come.

What do the battery volts drop to? As per the manual, the alarm will trigger if :

I think they are a nice to have, and not required by SANS. They are 220V.

So to avoid this happening, you need a CT clamp? This is all new to me, but something I'm investigating right now as I have 3kW of solar panels on the roof being used to charge 4kWh of battery use, and the rest of my generation is practically lost. Been thinking of installing a hybrid inverter so the panels can assist in powering the whole house, not just charging batteries and powering my rather modest essential loads (300W on average), but I do not want anything feeding back into the grid, even if it means lost solar efficiency.

Still a bunch to do/redo, but a slight miscommunication on Friday afternoon kinda forced me to get my ass into gear. Got home from fetching the kids from school and found out we had no power. This was a surprise as there was no load shedding scheduled, but through January there have been numerous substation trips, so I figured it was that. In a frantic panic to get the house, or part of the house powered before the wife got home (she's been on my case about finishing this project), I began feeding wires through the wall, connecting things up to the second DB and inverter, and trying to finish up before it got dark. Needless to say the cause of our outage was a lack of credits in the pre-paid meter.🙈 The end result was an almost working system. In my rush, I'd done something wrong and turning the downstairs lights would trip the EL. Turning on the main geyser would trip the sub-main db board EL. It was dark, I was annoyed, so the lights and the geyser stayed off that night. Saturday morning, I got up early determined to sort out whatever I'd messed up. I was pretty sure it was Neutral related, but wasn't quite sure what yet. I had two suspicions though. Either one of the circuits was bonded to the wrong neutral bus (Each DB has a separate neutral from the other) or how I was connecting neutral in the main db to the inverter was wrong. I chose to concentrate on the latter assumption as if I was right, it required the least work to fix. I was wrong and every alternate way I tried of taking neutral to the sub main db resulted in a worse trip scenario. Turned out I had connected the downstairs lights and geyser to the wrong neutrals...took a while to trace, but all is now working 100% as expected. I also worked out that the strange wire going through the DB without connecting to anything other than neutral (see previous post where I asked about it) is related to the geyser. Apparently, or so I've been told, it's something to with Eskom turning off your geyser when they like. Anyway, still to do: 1 ) blanking plate for main DB. 2 ) trunking between battery and inverter. 3 ) end cap for trunking at inverter. 4 ) warning labels, and proper db board labels coming soon 5 ) finish ICC Pi install, and not just sat on battery box. 6 ) surge arrester for PV. 7 ) replace PV cutoff switch (only large enough for 6mm cable, so for now I've had to limit PV charging to less than 40A) 8 ) install indicator lights in db board. 9 ) anything I've forgotten to mention here And finally some progress pics.

Creation date of the website domain certainly seems very scammy

You say your daily household usage is 10kW. Is that 10kW instantaneous, ie. the peak combined usage by your house at any one time, or 10kWh usage for a 24 hour period? If your peak combined usage is 10kW, it will overload a 3kW inverter, and either trip the inverter, or bypass it feeding from grid. If your total daily usage is 10kWh, then providing you don't peak more than 3kW (possibly double for very very short period) the inverter will handle it.

Now that I'm about ready to wire the new DB to the existing main, I have questions for any indicator lights I need to install. 1) Are there any colours that I should stick to? I've been seeing red for grid, and blue for generator in some change over switches. Are yellow and green also acceptable? 2) I'm assuming I connecting the lights to the source, before any breakers in order to show the source is live, and not just the source selected?