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Author Topic: Growatt Battery System  (Read 1591 times)
Pile-o-Stone
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« on: September 21, 2017, 09:59:57 AM »

We currently have 4kw of solar installed, which supplies most of our daylight energy requirements. Any excess is diverted into a thermal store via an iBoost device. We're adding an additional 2kw of panels onto an outbuilding roof and rather than have this extra energy just go into the thermal store, I'm considering adding a battery to store it for night time use.

The outbuilding is too distant from the house to communicate with a sender unit at the consumer unit, so the battery controller wouldn't be able to monitor our usage to feed in when the load exceeds the solar supply. I'd therefore want the panels and battery to be configured so that all of the energy from the new 2kw panels goes into the battery until it's full and for that stored energy to only be used in the evening.

The battery system I am interested in is the Growatt SP1000. I first came across this system on here, so I'm hoping the resident Growatt experts will be able to tell me if the battery can be configured this way, to only release energy at night time (i.e. once the panels are generating zero watts)?
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RIT
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« Reply #1 on: September 21, 2017, 12:05:00 PM »

That is unlikely to be a configuration that makes any financial sense - if it only discharges once the sun goes down you will get a maximum of 2.7kWh of usage from it - so maybe 40p of 'savings'. The result would be a payback well over 10+ years depending on your tariff even if it was able to discharge fully every day. The value 'add' of products like the Growatt is that they can provide energy during the day when your demand is greater than the PV output due to things like cloud cover. Not having this feature greatly reduces the likely return.

If you wish to go the Growatt route it would be far better for you to add on to your current 4kw PV system. The new 2kw system's output will be available to the iBoost device, so the Growatt will be able to store excess energy from the 4kw system, while operating at its best.

Another issue that we have discussed on these forums is the current issue with the possible returns seen by these devices. You have to make the call on if you think you will get a return that is greater than the speed at which the purchase cost of things like the Growatt is currently falling - Do you purchase one today and make a saving in terms of your energy usage or do you wait a year and purchase it after it has dropped in price yet again.
« Last Edit: September 21, 2017, 12:21:18 PM by RIT » Logged

2.4kW PV system, output can be seen at  - https://pvoutput.org/list.jsp?userid=49083

Why bother? - well, there is no planet B
knighty
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« Reply #2 on: September 21, 2017, 12:28:48 PM »

would a battery system which is charged by the mains not be better ? (instead of taking DC from the panels... which is what I think the growatt does?)

(like a tesla system)

that way you can put it anywhere you like... and it'll be able to charge from any excess power (so all 6kw of panels)
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Westie
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« Reply #3 on: September 21, 2017, 07:13:43 PM »

would a battery system which is charged by the mains not be better ? (instead of taking DC from the panels... which is what I think the growatt does?)

(like a tesla system)

that way you can put it anywhere you like... and it'll be able to charge from any excess power (so all 6kw of panels)

The Growatt SP systems are DC coupled so the panels are directly connected to the charge controller . 

The SP2000 is capable of AC charging (eg. charged overnight then from E7 time shifted for day time consumption), however this feature is disabled by default as it obviously contravenes FiTs guidelines.  Growatt say they will re-enable it if your install isn't Fits registered.

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4kwp south facing array  SMA 4000TL grid connected.  2x30tube Navitron solar thermal panels (east/west). Arada 5kw S/C WBS. 25000Ltr underground rain water tank. KTM E-Bike  Cool
knighty
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« Reply #4 on: September 22, 2017, 09:24:12 AM »

that's weird... people advertising tesla powerwalls advertise the fact that it's AC coupled and you get your fill fits payments for power used to charge the batteries?
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skyewright
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« Reply #5 on: September 22, 2017, 09:43:05 AM »

that's weird... people advertising tesla powerwalls advertise the fact that it's AC coupled and you get your fill fits payments for power used to charge the batteries?
Surely it all depends on which side of the Total Generation Meter the battery system is.

If the battery system is on the generation side of (i.e. 'before') the TGM (as per the Growatt?), then it cannot allow mains charging since that could result in 'non-PV' electricity passing out through the TGM, thus affecting FITs,

If the battery system is on the mains side of (i.e. 'after') the TGM, then mains charging would have no effect on the TGM.

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Regards
David
3.91kWp PV  (17 x Moser Baer 230 and Aurora PVI-3.6-OUTD-S-UK), slope 40, WSW, Lat 57 9' (Isle of Skye)
Mike123
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« Reply #6 on: September 23, 2017, 11:51:57 AM »

Are you sure the SP2000 can charge off AC? I thought only the SP3000 could charge off AC (Economy 7)

Also I presume the SP1000 could be set to Forced Discharge Mode, just like the SP2000 can be
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Westie
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« Reply #7 on: September 23, 2017, 09:29:51 PM »

Are you sure the SP2000 can charge off AC? I thought only the SP3000 could charge off AC (Economy 7)

Also I presume the SP1000 could be set to Forced Discharge Mode, just like the SP2000 can be

Sorry mike, your right, I meant the SP3000.
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4kwp south facing array  SMA 4000TL grid connected.  2x30tube Navitron solar thermal panels (east/west). Arada 5kw S/C WBS. 25000Ltr underground rain water tank. KTM E-Bike  Cool
Mike123
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« Reply #8 on: September 25, 2017, 04:51:44 PM »

Thinking about the current clamp, your idea doesn't seem to work

If the clamp was placed in the shed, then you could set it so that it saw power being exported from the shed into the house. So then the batteries would charge

But when it gets dark, it would still see the power as being exported so wouldn't release energy from the batteries

An idea might be to use the RF current clamp, but if the distance is too great, then remove the antenna from the sender, and run coax to somewhere close to the shed, and then fit the transmitting antenna there
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Pile-o-Stone
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« Reply #9 on: September 26, 2017, 11:18:36 AM »

I was wondering if the battery would work without the clamp at all, rather than have it connected to the shed's electrical supply.

I've decided to look at installing an AC linked battery system as it would take input from the full array and allow me to also store E7 electricity for peak use. I was originally looking at the Growatt offering because is was relatively inexpensive compared to a larger AC coupled system and looks quite straightforward for a DIY installation. However, on reflection I can see the scense in waiting and installing a more integrated solution.

Thanks for all the feedback.
« Last Edit: September 26, 2017, 11:20:40 AM by Pile-o-Stone » Logged
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