pilotfish

The Victron Gel Long Life 2v 600Ah looks like an option for you, seems to have charge requirements suited to Axpert SCC and brilliant life expectancy (1500cyc at 80% and 2500cyc at 50%) - no idea what they cost! From the attached pic's it seems remarkably similar to the FNB OPzV - which may be a viable alternative subject to more research. Victron -GEL_AGM.pdf OPzVPowerGel-2015-.pdf

I know that the forumites recommend against parallel strings, but I think that 2 strings that are well terminated with battery balancing and a cheap 3-30v DC voltmeter on each battery will be a very low risk installation. The above meter is about R40 on Bid-or-Buy. The issue with parallel strings is when one battery goes belly-up resulting in the rest of your string being toasted, with permanent monitoring you could immediately see if this is happening and react before permanently damaging the rest of the bank (in the case of sealed batteries by replacing the faulty unit). What size bank are you considering?

If it is 20w then solder on a 24v (min 1 amp) DC power supply and I am sure it will do the trick - if not it wont be any more broke than it is right now.

Two single MPPT Axperts in parallel, each with separate array but sharing a single battery bank.

Hi @gabriel, I am not sure that the BMV702 is intended to communicate with the PC - others will know more. The BMV has 2 components - the shunt which is mounted next to your battery bank and the monitor where you read the information which can be mounted remotely (so it could be installed next to your PC). Communication between shunt and monitor is via a 6wire UTP cable with with RJ11 (6 pin) plug on each end. The RJ11 is the same size as a telephone jack, and comes in 2/4/6 pin versions, very similar to the RJ45 which is the 8pin version used for LAN cables. The system comes with a 10m UTP cable in the box, you will need to find an extension cable or make a new cable to suit your installation.

I dont know of a commercially available product but it seems to me it would easy enough to design and build. It would require an LDR (light dependent resistor) in series with a trim-pot for fine adjustment on one input of an op-amp, with a set voltage on the other input - with the output driving a contactor that controls the pump (in conjunction with the pool timer). That's the basics - you would need to persuade a propeller-head like Plonkster or someone with electronics background to flesh it out a bit and bang it together.

I see the video but my mother told me to never trust a redhead I would be happy to parallel to simple SCC that are just charging batteries, but when you are working with sophisticated equipment where you are setting voltages for cut-off, back to grid, absorption, equalize, float etc and there is another SCC screwing with the voltages at the same time then my head starts to spin - not saying it cant be done but I wouldn't know where to start discussing it and not sure that the result would be acceptable (also not sure it wouldn't!)

Hi Zeeshan, The best way forward for you by far would be to replace the 4 cracked panels with matching equipment, or if not possible then to remove the 4 damaged panels and re-arrange your array to 6 strings - to try and add poly-christaline panels into your existing thin film array will be like picking your way through a mine-field wearing snow shoes.

Note that it is important that the string used on the weekend is left on charge through the week, don't leave your batteries in a discharged state.

That would be a viable solution for now. What I would do is start by leaving all 4 on charge for the week while you are away so that they are fully charged when you arrive on the weekend. Then when you arrive disconnect one string and leave the other string connected through the weekend and the whole following week to fully recharge (leaving the disconnected string also fully charged). On arrival the next weekend swap over for a week etc. That way your batteries will be used equally until you are able to install the MKS-5K.

The problem is that to get 30amp per string you will require a 60amp charger, the MKS 2k24v has a 20amp AC charger, 30amp max including PV - so the most you will get into each string is 10 to 15 amps, even with the generator. Given the low usage you may get away with it to a certain degree, but I still think that it would be advisable to upgrade to the MKS 5k which has an 60 amp AC charger and a 60 amp PV charger - that way you can comfortably use your generator to give an initial charge of 30 amps (into a single string at 48v), and you can add PV panels in future up to 3kw instead of being limited to the 600w of the current inverter.

Give us more detail on your full setup before we can provide a useful answer - is the system off-grid or grid-assisted. If you have 2x 24v strings of OPR240's you will require minimum 24v/60amp charger (30amps per string), preferably an 80amp charger (40amps per string). This will probably cost more than the Axpert 5kA, but have a look around and see what you come up with. Also where is the charger power source coming from? If solar then you will need about 3kW of panel (2kW for charging and 1kW overhead to supply the load).

Unfortunately the OPR240's are better suited to the Axpert 5K (or 3K-48v plus) which can both deliver the recommended 40amps charge (with enough panels or grid assisted charge if too few panels). You would have been OK with 1 battery string getting 30amps, but I think 15amps per string will not be a good match for the OPR240's. If your budget can do it I would recommend getting the one of the systems suggested above and trade/sell your Axpert 3k 24v. Your batteries are always going to be the major expense component and it will be worth the change to protect them in the long run.

Yes that will do the job if you decide to go the AGM route, just make sure that you are getting the RA-12-200D which is optimized for cyclic life rather than standby - the more common RA12-200Ah is a standby battery better for UPS etc "RA12-200D is an AGM deep cycle battery with 10 years floating design life,specially designed for frequent cyclic discharge use. By using thick grid & specific paste plates the battery has 30% more cyclic life time than standby batteries. Applications include solar & wind energy systems, golf carts, electric wheelchairs, etc."

Yes, first DC volts and then flick over to AC volts. Both values are informative. Sent from my SM-N910C using Tapatalk

The tests required are simply DC voltage and then AC voltage at the output terminals of the SCC (and then if you have a DC clamp tester the DC current at the time of testing), the Fluke 177 meter will read RMS values there is nothing special required. We are interested in comparing ACv values between the two SCC's under similar conditions with the lowest AC component being the winner. So the tests are dead simple, it is setting it up and getting it done which is going to be a PITA, so thanks in advance for your effort! Each SCC should be tested entirely on its own with no external influence - so no load on batteries while measurements are being taken and only the SCC being tested should be connected to the bank at time of testing, Carry out 3 times during the day if possible (early, mid morning, just before float) with the last test being the most important, This is the biggie If possible test at various charge currents (min/normal/max). If there is going to be a significant AC ripple component it would normally worsen as power output increases. If AC ripple is low at 20amps, manageable at 40amps but sky-high at 60amps then that is important information for Axpert owners. To carry out all the above tests will take time and be a significant disruption to the household, so it would be perfectly understandable if you cut it down to just one test on each SCC, at your charge current, preferably just before float.

I have about 12x Axpert 5k units out in the field operating as grid backup systems (so no PV input) and can report that the the inverter section has surpassed my expectations and are quite hardy units. I have had no failures at all and no problems reported regarding quality of the output. The output is hard wired into the DB supplying selected loads only so they are quite well looked after - supplying all lights, fridge, security equipment, computer/internet, entertainment systems and then a couple of plugs in the kitchen for small appliances and charging etc. I think that Voltronic have been in the UPS/Inverter business for quite a while and have that side of things pretty sorted. If you look at the Mybroadband test report pointed to by @viper_za above, it shows a waveform clean enough for anything other than the most sensitive scientific equipment, and certainly much cleaner than your regular Eskom supply. I still have some questions regarding the quality of the SCC section which these tests above have not yet entirely allayed.

I dont think there is any reason to be grumpy with Victron because it seemed to do a good job, it is just that the Axpert was equally good! I still think that carrying out the same test in less ideal conditions might swing things in the blue direction.

Correct. I have 2x Fluke RMS multi-meter but may be a bit far from the test lab (Randburg), I am sure that there will be someone in the vicinity with the correct equipment for a loaner.

Could the DC ripple not be tested to a reasonable degree with an RMS multi-meter set to AC, which would give a figure for the amount of AC ripple on top of the DC voltage. Obviously an oscilloscope is preferable, but the multi-meter should give an answer enough for comparison purposes.

Note that I made a c***-up in my original response regarding your panels, the above is incorrect and should read as follows; 2 panels - 320x2x8/1000 = 3.1kWh per day 4 panel = 6.2kWh/day Your consumption with both units occupied will be something like the following; fridge = 90W x 12h = 1080Wh x2 = 2.16kWh might be more because guests will probably stock up with warm beer and hot meat, and then open the fridge every 5minutes for another dop! lights = 40W x 6h = 240Wh x2 = 0.48kWh Total about 2.5kWh per day. This means that after a cloudy day the 2 panel system will have very little overhead available to charge 4 strings of batteries. I therefore suggest a minimum of 4 panels (1.2kW which is within Axpert capabilities but exceeds WRND30 750W panel capability). If you are uncomfortable with the Axpert charge capability then you should go for an external SCC, but not the WRND-30 which will limit you to 2 panels forever. If you go for the WRND-80 (12/24v) it has a 2kW panel capability and is cheaper than the WRND-60 which is is 1500Wp but at 12/24/36/48v. To be perfectly honest if I was in your shoes I would change the entire system design Axpert MKS 5k or MKS 3K-48+ Both the above give you 3000Wp and 48v system Minimum of 4 x 310W panels Gives enough power to supply load and charge batteries, Single string of 4 x 200Ah AGM battery Allows for single battery string matching the energy of the 4 strings on previous system, this will do MUCH more for battery longevity than fancy chargers, Axpert charging algorithm suits most AGM requirements very well. Battery balancer to prevent individual battery voltages going out of whack does the similar job for AGM battery life as equalizing does for flooded cells. If all you have bought at the moment is 2x panels then the above will probably cost about the same as your previous design.

It would be great if @PaulF007 is able to hang onto the borrowed kit for a while longer until he has an opportunity to put this to the test - I have read some comments about the slow response of the Axpert SCC, I would just like to see the comparative effect of this on a cloudy day.

Your pool motor is the perfect type of load to run off your 10kVA true sine system. Run it from 9am to 3pm and let the sun pay the bill.

I used the name when I played a bit of online poker a few years back - it refers to feeding off the sharks and nothing to do with flying.

Hi Vaaljapie, Make sure that you have a chin strap on your hard hat!!! The Axpert 3kVA Plus has a 1500w MPPT charge controller whereas the WRND 30A is only 750w at 24v - so you would be wasting your money on the WRND in my opinion, just use the Axpert charger. Your battery bank is 8kWh at 100% DoD, but your PV array will only provide 310x2x5/1000 = 6.3kWh per day ( on a GOOD day, using the customary 5 sun hours per day which accounts for all sorts of loses). Save the R3k that you where planning to spend on the WRND30 and rather buy 2 additional Enersol 310 panels, that will give you a much better balance.