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Something Plonkster learned from Victron, it is better to charge batts using Eskom up to SOC of 85%, rest using solar.

Edit: Eskom only if you do not have oodles of solar power with batt capacity to keep your load powered 24/7 with 2-3 days backup.

 

Inverters and all that are expensive, and software that tells you everything, emailing you, is scarce.

 

So, what about this idea to run off 24/7/365:

Using a Cyberpower, like these: http://eu.cyberpowersystems.com/products/accessories/eps/cps3500pro.htm

Adding all the batts the machine can handle, charged via solar panels and a controller.

And then, here is the key to save on Eskom: Get a BMV and use its relay to trigger an AC relay to switch Eskom to the inverter on / off.

I.e. if SOC = 50%, switch Eskom on.

When SOC = 85%, switch Eskom off.

(The above is keep batts above 50% DOD in case you use a lot of power and there is no sun.)

Daytime will take care of the rest of the charging.

 

These units must be connected direct to the house DB board, to power selected circuits.

 

What do you think?

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Something Plonkster learned from Victron, it is better to charge batts using Eskom up to SOC of 85%, rest using solar.

Just for the record and to avoid confusion, it isn't always necessarily better to do that. If you have oodles of solar power, you'd be silly to use grid power. This guideline has to do with cases where you don't have sufficient solar to fill up your batteries, and you might have to do some charging with the grid. In those cases, when do you bring in the grid? The guideline is simply that it makes more sense to do the first "half" of the charging with the grid, because under 85% SoC the charging process is over 90% efficient, and you get more bang for your Eskom buck that way. Above 85%, your efficiency drops (as you lose more energy to gassing and other parasitic processes), and to it makes sense to use the cheaper power from the sun to do this more wasteful bit.

 

If you have enough solar, or enough batteries (or both) that you can do it all with solar, then obviously you should do that :-)

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Noted Plonkster.

 

I agree 100%. Not many people will power their entire house 24/7/365 off batteries on off grid solar, at least not in cities.

 

Eskom is still cheaper than batts.

 

But, one wants to automate it all, so therein less panels and batts, using Eskom IF you do not want to reduce the load, using a inverter that has it all for +-R14k + card to connect to network i.e. pure sine wave, charger and software, connected to your DB board, powering selected circuits.

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So, what about this idea to run off 24/7/365:

Using a Cyberpower, like these: http://eu.cyberpowersystems.com/products/accessories/eps/cps3500pro.htm

Adding all the batts the machine can handle, charged via solar panels and a controller.

And then, here is the key to save on Eskom: Get a BMV and use its relay to trigger an AC relay to switch Eskom to the inverter on / off.

I.e. if SOC = 50%, switch Eskom on.

When SOC = 85%, switch Eskom off.

(The above is keep batts above 50% DOD in case you use a lot of power and there is no sun.)

Daytime will take care of the rest of the charging.

 

These units must be connected direct to the house DB board, to power selected circuits.

 

What do you think?

 

Am I missing something - to me it looks like a stock standard UPS?  

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Define standard UPS. :D

 

In a sense, yes, it is a UPS SuperDIY, bar three caveats.

These units can run 24/7/365, have exceptional software and can take a lot of 200ah batts.

 

Most UPS'es cannot do that as most are designed to run for an hour or two, some only a few minutes, then batts are flat (small 7-9ah ones), therefor their inverters are designed to a much lower spec than i.e. solar inverters.

Most of the UPS'es that can take 102ah batts, their inverters  cannot run 24/7/365 either, nor have strong enough chargers for 200ah x 10 batts, like the CyberPower.

 

And if you think of online UPS'es, with all their features, the good ones tend to be 96v, small batts and very small chargers with expansion batt packs costing a small fortune.

 

And very few can be connected directly to a DB board. As a matter of fact, the CyberPowers, if run at full capacity, must have its own breaker in the DB board.

 

So for someone who needs a solution for Eskom woes, this is much cheaper than inverter and panels.

You start off with a CyberPower and then expand as I am thinking of in the first post.

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The Cyberpower units look like a good product and value for money but they don't have a great power factor. (power factor = 0.7)

So the 3.5 Kva unit is only rated to 2.45 Kwatt.

The 5 Kva unit is rated to 3.5 Kwatt.

So when comparing inverters i would look at the power rating to determine whether i am getting value for money.

Also can't find the efficiency of the unit while operating off batteries. 

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Re UPSes, some are designed for only a few minutes in more ways than just the batteries. They save money on the heat sinks as well, so if you wire a larger battery to it, it will overheat a few minutes later and die anyway.

 

See for example this video where knurlgnar modifies an APC to be a standalone (MSW) inverter, with some success before he ends up killing it.

 

 

I understand the basic point though, and I think this is a kind of holy grail for renewable energy. How do you lower the initial investment in a way that is also expandable, but immediately useful. In 2013 when I put in my inverter, I thought the Victron Multiplus is the key because:

 

1. You can put inverters in parallel (this was the only one that could do it at the time, Axpert wasn't available yet).

2. You could start with just the inverter and batteries, and add the solar later, because the Multiplus has a charger and can act as a UPS.

3. Solar can be added piece-wise, especially given that Victron now makes rather affordable MPPT charge controllers on the low end. Not exactly cost-effective in the overall sense, but you can add a couple hundred Wp at a time.

4. Where Victron seems to be going with their hub-systems is precisely what this is for: Use a smaller inverter that can carry baseline, drop to the grid if you must. Read their self-consumption whitepaper.

 

The problems however:

 

1. The multiplus is expensive, and Stortkop didn't help in that matter, it is now 80% more expensive than it was when I bought it.

2. You cannot mix old and new batteries, so there isn't a decent upgrade path for batteries, and this is a rather expensive component in the equation.

3. Despite the positive tone of the Victron self-consumption whitepaper, the inverter actually cannot do a proper hub system without a lot of additional (expensive) hardware. The point of using a smaller inverter is precisely to make it more affordable, and so far we are not there yet. In their defense, one of the big issues at the moment -- anti-islanding -- is currently being addressed in their new hardware, and with hub-4 maturing a lot of new possibilities for embedded control systems are opening up.

 

So I think it is a good idea... but I'm not sure I want to use THAT inverter :-)

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Me too Carl. Inefficiencies are very important.

 

Plonster, I tried my best to get UPS inverters instead of the Victron ... every single UPS supplier told me that will happen.  :D

 

And as you said, Victron has the UPS feature, but ...

 

The UPS industry is quite mature. So over time I realised that solar inverters do not have half the protection online UPS'es have as standard nowadays, and 10ms changeover, that is awesome!

 

When you bring Eskom in as part of your power generation, Eksom has a lot of issues over and above no power. For example:

Friend measured Eskom volts exceeding 300v in Gordonsbay. 

Dealer reported that in the area he lives, when Eskom is off, there is still +-100v AC coming into his house, speculatively from a nearby wind farm. The damage this has caused him and his insurer, was substantial.

 

And closer to home, the previous online UPS I had was damaged by an electricians who accidentally connected the neutral and earth together in the DB board. Blew the online UPS charger, yet inverter was still perfect, so was all the equipment. Only realised the problem when the UPS stopped working due to flat batts.

 

If it was not for the online UPS, a lot of stuff would have been damaged. Ja, insurance and all that, but lets be real, it is a huge mess when it happens.

 

Even a Multiplus cannot sort the above problems.

 

All power going to my devices are actually powered by a online APC fed by the solar inverter, for I do swap between solar and Eskom twice a day. Stuff that inverter powers 24/7, are not going via the APC as there is no Eskom near them.

 

So me, myself and I, we will always have a online UPS powering critical devices, if Eskom is part of the equation. The cost of a few rands due to inefficiency, is ok.

 

Plonkster, you said you would not use THAT inverter  :D , which one will you use? Considering:

Pure sine wave

Changeover times in the region of 10ms, for the norm of 20ms do switch off some devices with small PSU.
45amp charger

Connected to your DB board on its own circuit, powering selected circuits from unit.
 

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Plonkster, the video you posted, he said that he can charge the batts using utilities. That depends on the batts you add. I learned that you cannot use the smaller UPS'es to charge i.e. 102ah. Their chargers are not designed to put enough amps into them batts. So not only do they overheat, they also do not have enough power to charge larger batts if you want to. So double whammy.

 

Same with the R30k online UPS'es, although their inverters work 24/7/365, they also have to small a charger for large batts.

 

Man, I tried this UPS thing from all angles, until it dawned upon me re. the CyberPower range.  :D  :D  :D

If you add all the batts it can take, I think 12 x 200ah (24v), running a 25% load, it can run for +-2 days, if your REALLY want to get all those batts.

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Plonkster, you said you would not use THAT inverter  :D , which one will you use? Considering:

Pure sine wave

Changeover times in the region of 10ms, for the norm of 20ms do switch off some devices with small PSU.

45amp charger

Connected to your DB board on its own circuit, powering selected circuits from unit.

 

Well, I said I'm not SURE I want to use that inverter, that is to say, I would much rather use a Multiplus... but this exchange rate man... it hurts.

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