Abe53

Hi Bobster, I also have a Victron - Pylontech system and the Venus GX seems to manage it well. However, my powerwall consist of 1802 x 18650 lithium-ion cells, (factor that, how many strings of how many cells 😉 On this system I use a manual battery management system. Each string can me quickly isolated and tested in situ under 1C load. A string under performing is isolated and cells individually tested 10 at a time on my bench tester. Cells under performing are then replaced, they only cost R1 apiece. To avoid the dreaded overcharge, solar charges to max 4V per cell. (Specs say max 4.25V or such) The powerwall feeds a UPS which switches off when batteries are at about 50% soc. Since batteries are so cheap I need never use full capacity. So far so good!

HI Hoohloc, there is an even simpler and cheaper way to hot water. Just feed your standard geyser element straight 200V DC from 5 or so PV panels in series. (Put 6uF capacitor over thermostat to stop arcing.) Once the geyser is hot, thermostat switches off, voltage rises and charges batteries through charge controller. (First a Diode to isolate) I changed geyser element to 2kW to match string output, but you have enough panels to use 3 or even 4kW element.

Could someone point me to an authorative (sp?) test to show the value of BMS? I run several battery systems and have yet to see negative consequences of cell imbalance. The constant drawing down of high Voltage cells and pumping up of low voltage ones must waste energy? My cells each seem to find their happy place until they give up the ghost, at which time I just replace the dead cell. What possibly can go wrong, go wrong, go wrong....

Hi Robbo, as ThatGuy said, your time is worth actual money, and I want to add, it can work for you. Plug into your calculation: Inverter R34k? How about R3k? Repurposed obsolete UPS from a company basement. Match panel DCV to do without electrickery. 2 x 5.5kWh Hubble R50k? Built 14kWh storage battery from 1800 recycled 18650 lithium-ion cells, maybe R5k. Manual BMS means indefinite life by easy testing of strings and replacing individual cells. 20 x 435W CS panels? = R50k? Make do with 10 such for R20k by swinging E-W on high pole mount and get max from sunrise to sunset. OK, DIY engineering. R40 installation? As said, DIY. Solar geyser R plenty? Use excess PV 200VDC straight into standard 220V AC element. (OK, needs capacitor and diode, R200) Sorry to mess your figures, just want to point out that Solar makes for a great DIY project that pays for itself real quick and provides free electricity from then on.

Hi Dani, where are those inverters?

Hi Beserker, Yes, I need more 18650 cells, will buy laptop batteries untested. Abe53 ohaihtooninertoosixohfiveraightfiver

Hi Jason, Has the solar panels been collected? If not, I will collect if in Gauteng. Both 180W panels on my Golf cart each lost a string and OCV now too low to charge. cannot warrant replacing with new.

Hi geyser guys, sorry, but all of this thread just do not compute. Storing energy in hot water is a losing investment. It will pay off in only certain, rare occurrences, like on a cold cloudy morning after a sunny day. Heat is leaking away all the time and can easily be replaced when the sun shines again. I just stringed 5 x 40V, 360W panels to supply 200VDC to a standard 230VAC 2kW element in my existing geyser. Wired a 6uF capacitor over thermostat to keep it from arcing and welding shut. By about 11:00 AM thermostat opens, voltage rises, when more than battery voltage, 210V battery bank charges through a diode. (Which keeps batteries from feeding geyser.) We have hot showers and by sunset full batteries for the admittedly inefficient but cheap Eaton 5KVA UPS to see us through to bedtime. No charge controller, manual battery management when bored. I just do not see complications improving my utility. (I also have a VIctron-Pylontech system with less capacity, at three times the capital cost.) What am I missing?

Hi Stanley, and thank you very much for your considered replies. ACDC did not have a suitable diode in stock, but got me a 16F120 the next day. (16A 1200V DIODE - CATHODE to STUD) I simply screwed it in the PV breaker output on the way to the batteries. It causes at most a 1 V drop. I installed a 6mF capacitor over the geyser thermostat to keep it from arcing. All working well, when thermostat opens, volts go up and batteries charge.

I searched the forum but could not find a discussion of diodes in DC circuits. If this is not the place to ask for help, please point me to where I could find info on this? In short, I have a PV array supplying 200VDC which heats a geyser. When the thermostat switches off the current should charge up a power wall battery supplying an inverter. A diode is thus needed to keep the batteries from heating the geyser after dark. Any help with specification and sourcing such will be much appreciated.

Hi Erastus, When next will you have PV panels available? I live on a farm near Harties and am looking to buy 16 x 400W PV panels. ohaighttwoninertwosixohfiveaightfive.

Hi Martin, did the buyer pan out? If not, what did he offer? (I am scrounging components to take 6 houses off-grid cheaply, none critical, can thus take risks)

Hi Seant, yes, may I buy your UPS? It is exactly what I need to replace my Titan 3000VA UPS that cannot be repaired. Contact detail by PM.

Hi CCC, before the mods get wind of this, we can quickly auction off these inverters, I would like to start the bidding at R21000 for the 3?

Anything still available?

IMHO, Get more solar panels before adding more battery.

Ah, see my reply has finally registered, was about to redo...

May I join the bidding when Tersius has his ticket in hand? By the way, fare well young feller, many oldies like me are stuck in this hell-hole with not enough wherewithal to buy our way out.... Abe53.

Hi Jonahex, no specs, no price? Looks like 3kw per phase, selling new R60k? Will need such in a year or two for a workshop once within reach of off-grid for our five houses on a farm. If it is going for a very good price I can juggle the plan and buy now. Abe53.

Batteries only good for recycling by now... Will take the inverter if priced reasonably. See PM for telephone number.

Hi again Terrible, Yes, I have applications for just such inverters. Decent price? Is there a PM facility here to exchange telephone numbers?

Hi Terrible Triplett, Thank you for your encouragement and advice. Powerforum has been good to this newbie, I picked up Langman's system! Now, due to the confining trees around our residence and wishing to keep the PV panels out of reach of avaricious re-allocators (previously named thieves, but this is no longer PC) I want to put the panels up on tall poles and swing them with the sun to eventually recover the added construction expense through higher efficiency. I thus next need two sun-tracking frames for 6 panels each, or one with 12 panels. Single-axis will suffice. (The Canadiansolar 255W panels measure 2000 x 990 x 40mm and weighs 22 kg apiece.) Also need another 6 panels. Then I need a charge controller for an Eaton 5KVA UPS (+EBM) I picked up cheap from the Broadband forum. (It was used in a no-longer viable Bitcoin mine) Cartage from East London cost almost as much as the purchase price, but I am not complaining. The problem is it runs on 180VDC nominal. (Floats at 208VDC) Steep learning curve, but learning fast! Abe53. P.S: Phil, our water is thankfully sorted, pumped from our boreholes at www.hoogland.co.za and backed up by a 125KVA generator I had installed before I retired.

Hi all, Last week Eksdom took five days before they found time to push back 2 tripped fuses on the transformer at our houses not far from town, after a lightning strike. Such a trip is common in summer and usually were fixed the same day. Fault reports were several times canceled as supposedly fixed! This lackadaisal attitude towards paying customers has now made us decide to move towards going off-grid on this account. Gas stoves in use, solar geyser kits on site, some inverters and batteries in use. Scrounging what we can on a limited budget. Need more inverters (in the 5kVA range), lithium batteries, solar panel arrays (sun tracking) Learning fast! Best regards, Abe53. (Yes, that is my year of birth.)