openmind

Yes, the Deye HV batteries are designed to be serialised with a BMU controller - like this: https://sp-energy.co.za/product/deye-battery-61-44kwh-hv-bos-g-set/

Ah, yes, thanks, looks like I'll need 6 batteries with a 30kW inverter (they seem to be 1C). Eish. Yes, the HV batteries are designed to operate in series with a BMU which I have in my calcs. The 20kW HV unit is looking more doable, smaller, cheaper, fewer batteries...

Haha, not spending more than I need to - I'm on a smallholding with two dwellings and a three-phase borehole pump (and other pumps) so I need more kW (and kWh) than average. I just did some rough calcs and based on online prices, I can do a single inverter 30kW 3ph high-voltage setup with 20kWh of battery (4x5kWh @ 50V in series to give 200V to the inverter that needs 160V min) for about only 10% more cost than my original 2 x 12kW 3ph low-voltage solution (all Deye products). So HV is very much an option. Still learning though so may have missed something. My installer is looking at the details and I will report back.

Thanks for your insights, food for thought. I did not realise the HV inverters have more than 2 MPPT inputs.

Hi all, I'm planning on upgrading my solar setup to 2 x 12kW 3-phase inverters connected in parallel. I live on a smallholding with 3-phase Eskom power and run a borehole and other pumps that are 3-phase. We have two dwellings so the 24kW total capacity will be great. The reason for two 12kW inverters instead of one big one is that I get 4 MPPTs rather than two which is good as I have a complex roof layout and will need more than 2 strings to make the most of my roof space. Also redundancy. I aim to be able to go effectively off-grid in summer and on sunny winter days to save costs. I'm in the Western Cape. I'm looking at the Deye and the Sunsynk units. They seem pretty similar but my installer prefers Deye as he has good experience with their service centre. Does anyone have any experience, insights, war stories of either of these two options to share? Which would you prefer? I see that Deye have a new version of their inverters and the international websites show that the 12kW 3ph is also updated, but that's not available here yet. Is it worth waiting for or should I take advantage of the deals on the current version? The specs look very similar except for the total PV input power which is quite a bit more on the new version, but with my roof space I won't really be able to take advantage of that. Much appreciated.

Hi Coulomb, thanks so much for that detailed reply. I've learned a thing or two. Specifically, I now understand that the inverter will not go to bulk/absorb charge every time the batteries are used a bit, but only when there has been significant discharge. I tested this today by switching off the supply to the inverter and letting it run for about five hours until the battery voltage was about 25.2V under a small load (±250W). Towards the end, I put a big load on it (hairdryer!) to nudge it under 24V under load for a few secs just to be sure that bulk charge would be triggered. Sure enough, when I put the mains supply back on, the inverter quickly ramped up to 60A charging current and the voltage slowly crept up past float and up to the bulk voltage setting. Relief. An hour later the fans were still running like a jet engine and the current was is still at 60A so I assume a good charge was in progress. A short while later I noticed the current start to drop and, as you predicted, when it hit 11A the charge process stopped (CHG LED stopped flashing) and the voltage slowly dropped down from bulk to float. Thanks again, it's good to know what's actually going on! I feel properly ready for load shedding now Bring it on, Eskom.

Hi Everyone, Great forum, thanks for all the brilliant content! I think I have an issue with my KODAK Inverter VMIII 3kW 24V (OG 3.24) - it does not seem to charge to the bulk/absorb voltage (28.8V) - it stops at the float voltage (27.6V). I don't have solar panels, just the inverter with input from Eskom (when it's there) and using the batteries during load shedding for lights, fridge and a few other occasional items. I have four CSB HRL12390W 12V batteries connected in two parallel strings of 24V. Pics attached. The batteries are brand new. My understanding is that when Eskom power returns after load shedding the inverter should charge the batteries at the bulk/absorb voltage and then once the current demand from the batteries drops off, (i.e. when they are full) the inverter should drop the voltage down to the float voltage. I have now monitored my system during three load shedding cycles and the same happens each time it charges - it only goes as high as float. I assume that the battery voltage reading on the display is the actual voltage being sent to the batteries (it seems that way - every time I check the batteries with a multimeter that reading is correct). So when the power comes on and the inverter begins the charge cycle, the battery voltage climbs slowly to the float voltage setting (at the max Amp setting, 60A during charging) and stays there, even once charging is "done" and the charge current is 0A. I'm worried that I'm undercharging my batteries. I suppose I could manually set the float to the bulk level and set it back down to the actual float once the batteries are changed, but I doubt that should be necessary. Anyone know what's going on? Thanks