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Author Topic: Victron Multiplus, SMA PV, Honda EU20i generator + On grid. What Batteries?  (Read 16264 times)
al_uk
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« on: October 16, 2014, 11:54:51 AM »

Hi all,

We are on grid with a standard Sunny Boy 4000TL and 3.6kW G83 PV system. We typically have 3 power cuts per year during the winter lasting between 8 and 36 hours. We also have brownouts lasting up to a few seconds at least weekly.

I have a Honda 2kVA generator converted to propane and we have a 100A transfer switch fitted upstream of the main CU. The Solar PV is also fed into an RCBO on the main CU. This means that I can either isolate the PV, or keep it in circuit when the transfer switch is switched to generator. Up to now, I have always isolated it to avoid the risk of backfeeding into the generator.

This all works reasonably well, however I would like a little more peak power available without going to the expense and maintenance of a 2nd paralleled generator.

The extra power would let me comfortably run the washing machine (we have a baby with another anticipated) or the microwave as well as the base load. We also use rainwater for 2/3 of our usage with a pump that doesn't have soft start.

I have a 3kVA APC Smart-UPS which protects the computer equipment in the house. I am considering replacing this with the 48v 3000VA Victron Multiplus downstream of the generator and before it feeds into the transfer switch. The Victron would take its mains grid feed from another CU which is upstream of the transfer switch. This means there is no risk of connecting the unit's input to its own output. My reasoning is as follows.

1.     I can use the dynamic current limiting and power assist to smooth the load from the generator to allow it time to throttle up and down on eco-throttle, while not risking damage to "instant" startup loads such as the microwave and water pump.
2.     The power assist will provide the extra power from batteries to run the washing machine or microwave without overloading the generator.
3.     The batteries will give me some capability to run small loads (eg gas boiler) for a few hours during a power cut when the generator is off at night.
4.     I don't really need 3kVA of boost capability, but I do think I want 48V, and this is the smallest 48V model.
5.     Although the existing line interactive UPS syncs happily with the generator, it cuts in and out of battery power when the generator spins up and down on eco-throttle as the house loads vary.
6.     I don't believe it is worthwhile to try and configure this in a "self consumption" way by using the stored power overnight and recharge from PV. The round trip efficiency losses and battery cost per kW/H don't add up. So just looking for standby use.
7.     There is no risk of trying to power up the grid in a power cut situation as the transfer switch will disconnect the house
6.     I work from home 50% to 75% of the time, so being able to continue working in the event of a power cut goes a long way to justifying the cost. Also with small children, being able to continue as normal does wonders for my standard negative brownie points balance with my Wife!

Looking for help with the following questions.

1.     Any holes in my reasoning above?
2.     I am thinking of 4 x 12V approx 100ah batteries. This is a standby application so the batteries will only be discharged a few times a year, which can be limited to 50% SOC or higher. What would be the most appropriate battery type for this application, and how many years could I expect them to last?
3.     Can I bring the PV in circuit when on Generator power? The PV will be downstream of the Multiplus. If the PV remains in circuit when running from generator, then I think the Sunny Boy will sync, and that the Multiplus will proportionally increase the output mains frequency up to 52Hz when the Generated power = Load power. I think the Sunny Boy will then sense this increase, and throttle back the generated power so that back feeding doesn't occur. Has anyone tried this, and will the Sunny Boy work like this in standard G83 mode?

Here's a pic of the configuration today, with the Victron replacing the APC.



* Electrical2.png (17.84 KB, 1096x728 - viewed 1213 times.)
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« Reply #1 on: October 16, 2014, 02:25:50 PM »

Hi
If you go the Victron or similar  Inverter road with batteries , i would  try an approach to   have  all year round and night ,  electricity from your FiT harvesting  system  not only for  the eventual power-cut

Regards Billi


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al_uk
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« Reply #2 on: October 16, 2014, 09:51:21 PM »

Hi Billi, thank you for responding. I hadn't really looked at using it to reduce grid import at night, because of all the discussions concluding that the total cost per kW/H for battery power is greater than grid import.

However, in my case, I actually only need to consider the incremental cost between a battery pack suitable for standby usage, and a battery pack suitable for cyclic usage, because I'll be buying the rest of the kit regardless!

To do the cost comparison, I am not sure what batteries I should be looking at for either standby or cyclic use - any suggestions? Does Li-Ion stack up yet?

My base load is 300 to 400 watts (yes this is higher than I would like).

I do have spare roof capacity for another 3.5kW Southwest facing panels which I could add at some point.

Thanks.
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« Reply #3 on: October 16, 2014, 10:24:05 PM »

I agree with Billi, think big !  tumble

More PV, big forklift batteries and run your house off it every night, you won’t regret it.  extrahappy

Also think about power diversion to water / storage heaters with an Immersun type device too, cos with more PV you’ll find you too much power in summer.  fume
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« Reply #4 on: October 17, 2014, 01:12:14 AM »


3.     Can I bring the PV in circuit when on Generator power? The PV will be downstream of the Multiplus. If the PV remains in circuit when running from generator, then I think the Sunny Boy will sync, and that the Multiplus will proportionally increase the output mains frequency up to 52Hz when the Generated power = Load power. I think the Sunny Boy will then sense this increase, and throttle back the generated power so that back feeding doesn't occur. Has anyone tried this, and will the Sunny Boy work like this in standard G83 mode?


Do you have a link to where it is detailed that the Multiplus operates in this way (changing the output frequency). I'm no expert of the device, but its the first time I've seen someone comment that it can do this.

I also have a question for everyone else, will the Sunnyboy keep operating in this configuration, or will it shut down because the 'SMA grid guard' will not like the power it sees from the Multiplus?
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al_uk
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« Reply #5 on: October 17, 2014, 04:31:15 AM »

General config information around self consumption here
http://www.victronenergy.com/upload/documents/Whitepaper-Self-Consumption-and-Grid-independence-with-the-Victron-Energy-Storage-Hub-EN.pdf

Victron Wiki page here
http://www.victronenergy.com/live/ac_coupling:start

Old Manual here-I think this has been withdrawn though, but has some details.
http://www.flinkenberg.fi/batteries/material/victron/Manual%20-%20Assistants%20-%20Self-consumption%20Hub-2%20-%20rev%2002%20-%20EN.pdf

On the Sunny Boy there are settings for power control by frequency shifting but I am not sure if these have any effect in G83 mode.

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« Reply #6 on: October 17, 2014, 08:14:58 AM »

On the Sunny Boy there are settings for power control by frequency shifting but I am not sure if these have any effect in G83 mode.
You have to set it off grid mode. Then it no longer complies with G83 so has to be controlled by a G83 approved device that is compatible.
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« Reply #7 on: October 17, 2014, 10:22:20 AM »

I just don,t know guys,
                     All these expensive machines are like a trap,once you get sucked into them you have to keep buying them compatible toys,,for that year,,for that model.
  The whole idea of renewable energy is that life can be more simple,more compatible ,more renewable.
  I have been as you all know,Off-grid for years. I use multiple 2kw chinese wind turbine controllers to handle the excess energy from the PV, Once they see 138volts they automatically divert it to our immersions.They support one another without any fancy Island and they do not cost a fortune. I believe that you can actually buy them with laptop connections. They honestly seem to be a bullet proof way of doing business.
 One of the big advantages of having multiple controllers is that if one goes down (it has not happened yet) the others can carry on,the only difference is the voltage creeps up but you can see that at a glance and there is no reason to panic because they are still working happily and give you time to get things in order.
  Some of the fancy stuff that I am seeing here on Navitron cost an arm and a leg to repair or replace and non of them provide any form of backup.When they are dead,they are really dead.
  We should be the ones who dictate the route to travel,We should not allow ourselves to be ripped off and forced to pay loadsa money for complicated boxs of tricks.
 The more complicated these companies make their product the more money you will pay and goodness,!! they are far from foolproof.
 But again, Is like I said at the start, I just don,t know.
                                                           Biff
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« Reply #8 on: October 17, 2014, 10:34:18 AM »

All these expensive machines are like a trap,once you get sucked into them you have to keep buying them compatible toys,,for that year,,for that model.
  The whole idea of renewable energy is that life can be more simple,more compatible ,more renewable.

Absolutely.

The simplest, cheapest and most sensible option for the OP is a bigger generator. It's only to cover a couple of power outages a year, which could probably be coped with without standby power at all.

Trying to fully integrate the original PV system is silly. If you don't lose FIT entitlement altogether, the system output will be lower with so the FITs will be lower - and the cost will be totally disproportionate.

Having said that, I like expensive toys myself so when I have bought the batteries and built the room to house them I'll be going mainly off-grid with a non FITted 12kW SunnyBoy/Sunny Island system to replace the UPS. The original 3.8kW FIT system will be unmodified and export 100%.
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« Reply #9 on: October 17, 2014, 10:41:37 AM »

I agree - things can just get so complicated, expensive, and completely out of the realm of "saving the planet" - as we've often seen (and it's a scenario I've oft quoted) - someone comes along full of good intentions to use solar power to give light to their remote lambing shed in winter - once you do the sums, the answer is "don't, use a generator or Tilley Lamps", as counter-intuitively, they're actually cheaper, and will do less overall damage to the environment (the moment "battery storage" is mentioned, the warning bells go off) - in the right circumstance, where there is no other pragmatic solution, perhaps, and think very hard about it and do some sensible sums (none of this "regularly discharge to 50% DOD" nonsense), THEN see if it's worth it - and as always, start at the other end first, minimise consumption, then look to provide for your needs............ Smiley

In this thread, another vote for a bigger (or 2nd) gennie, or just cut down on the power you're using!
« Last Edit: October 17, 2014, 10:55:48 AM by martin » Logged

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« Reply #10 on: October 17, 2014, 12:56:12 PM »

Martin ,  i disagree 

because of the following  reasons

-In the UK  one is limited to  16 A   or under 4 kw PV , a battery based  idea  would provide  a much bigger PV solution  for many households ( depends on space )
- allowing people to invest in immersion  burning ideas  and get paid for it  per burnt kWh  is bad politics , instead of  providing a structure  balanced feed ing the grid
- with a battery based  idea the  Threadstarter can make  use of all his  PV   electricity , that he would otherwise have to import  from the coal and Nuclear Grid at night and get paid for it for his PV power at night  ( that  i  certainly support )
-buying another generator  ontop of the 1000 GBP  one he has  allready makse no sense to me .... cause seen with  a DIY  eye 2000 GBP  is 4000 watt of PV  and no fuel needed

Sorry for opening a  general court case here  garden

Billi
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« Reply #11 on: October 17, 2014, 01:34:18 PM »

Hi Billi,
      I think, Martin means a second small geni that one could take out to the far flung sheds for lambing and then when the season is finished take it home again. One you can carry in one hand) Some of the little 2 stroke 750watt can be run very economically and then there are small inverter type geni,s that are very economical. The only the use the fuel that the load demands off them. So if you are only using it for lights they just putter along on fresh air almost, (so they tell us)
                                                         Biff
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« Reply #12 on: October 17, 2014, 02:11:13 PM »

As the op is "on grid", I'd think twice about a modicum of batteries just to fill the odd gap in supply (especially to run a microwave) - as I said, for that use I can't see batteries being particularly cost-effective. Just as a point of information, small modern 4-stroke inverter generators with eco-throttles run incredibly frugally  - they usually quote something like .45 litre per kilowatt hour, so certainly for the lambing house they've got to be a winner.
Having said that, if you're looking to go completely off grid, that's a different kettle of battery banks, and you'll be looking at serious money.........                               
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« Reply #13 on: October 17, 2014, 04:31:13 PM »

Thank you for all the replies. I agree that the simplest and cheapest option would be to get a 2nd EU20i, but as I like the toys I'd like to explore the options a bit more!

I think all I am looking for now is a "better UPS" which is more suited to running from a small generator than the APC. Which is where the multiplus comes in.

I would then need some UPS type batteries. For primarily standby use, my thought was 4 of something like these Victron Gel batteries which seem safer and lower maintenance than the forklift batteries mentioned earlier. Any better value suggestions?

http://www.criticalpowersupplies.co.uk/12v-90ah-80ah-gel-deep-cycle-battery

(Hope the link is ok)

I'll not bother trying to integrate the existing PV as it looks like it will break the G83 rules.



« Last Edit: October 17, 2014, 04:34:41 PM by al_uk » Logged

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« Reply #14 on: October 17, 2014, 05:16:42 PM »


I'll not bother trying to integrate the existing PV as it looks like it will break the G83 rules.


You may want to move your PV to the grid side of the wiring. This way none of the work you do will effect its operation. It will be on when there is a grid service, and you can then do what you want on the generator/UPS side of the design.

Depending on when you plan to do all this you may want to watch the SMA Sunny Island product as it may at some point become UK G83 approved, so allowing everything to be intergrated, by the use of their power monitor and an indepedent control box.

As for the batteries, you may want to give Navitron a call and see if they can provide the duty cycle information for the Rolls batteries they supply. This will give you sometime to compair the Victron units against. From little info I have seen on the Rolls units, the duty cycle of the Victron unit seems rather low, as does its capacity.

On another site I have found the following publishes Rolls duty cycles

            Rolls 4000 Series     1280 cycles to 50% DOD      800 cycles to 80% DOD
            Rolls 5000 Series     3200 cycles to 50% DOD      2100 cycles to 80% DOD

The victon unit is quoted at  600 Cycles @ 50%

Navitron's battery page can be found at  http://www.navitron.org.uk/product.php?proID=157
« Last Edit: October 17, 2014, 05:34:23 PM by RIT » Logged

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