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Author Topic: Rolls batteries rock  (Read 6221 times)
skyewright
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« Reply #15 on: July 05, 2013, 10:54:47 AM »

Energy is Ah x Volts.
In this case theoretical total capacity is 400 x 24 = 9600 Whr.
Divide by 1000 to get 9.6 kWhr.
Divide by 2 to get capacity to 50% DOD = 4.8kWhr.
they're 6v 400ah each and there's eight, two parallel banks of four, 19.2 and 9.6kWh.
Right, so each bank of 4 is effectively a 24v 400Ah, which paired up gives 24v 800Ah in total, then Bills maths applied to that.
Thanks.

PS. No I'm not thinking of going off-grid, we have a fine overhead down here, just recently refurbished.  Grin

But I do keep being drawn to the idea of a substantial backup (as per the "PV storage set to take off in UK from 2014" topic).

Around 5kWh usable capacity kept topped up in daylight hours from the mains (for most of the year effectively topped up from our grid tie array, which currently exports well over 50%) could (I think) supply an inverter feeding a separate ring on which I could put our 70W ish background load, allowing for between 1 & 2 kWh per night (depending on the time of year) from the batteries replaced next day, and enough capacity to keep the background load going for at least a whole day in the event of a major powercut (or for one of those days, typically at least once a year, when SSE have a 9am to 4pm planned outage for maintenance).

Probably a silly idea...  Grin
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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)
billt
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« Reply #16 on: July 05, 2013, 11:39:20 AM »

For backup a decent, big, UPS is the simplest option, probably the cheapest as well.

The drawback is that any battery system is inefficient; you'll lose at least 20% of your energy and inverters squander a certain amount even when they're not supplying power.

At the moment I use a second hand Powerware 9120 2000va UPS with 3 battery strings giving a theoretical 2.8kWhr capacity. It hasn't got a separate ring main, but feeds everything that I think is important - CH and solar controllers, computer routers and switches, PCs which monitor weather and various other things, phones etc. That gives about 14 hours of back up, but it wastes 80W when in line-interactive mode.

Unfortunately I got tempted by some cheap PV panels and inverters, and a couple of threads on here have (mis)lead me to the conclusion that replacing the UPS with a Sunny Island system for the whole house is almost a reasonable thing to do!

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camillitech
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« Reply #17 on: July 05, 2013, 12:53:49 PM »



Unfortunately I got tempted by some cheap PV panels and inverters, and a couple of threads on here have (mis)lead me to the conclusion that replacing the UPS with a Sunny Island system for the whole house is almost a reasonable thing to do!



 Cool Hmmmm, sounds like like you've 'caught the bug'  hysteria
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
skyewright
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« Reply #18 on: July 05, 2013, 01:54:50 PM »

a couple of threads on here have (mis)lead me to the conclusion that replacing the UPS with a Sunny Island system for the whole house is almost a reasonable thing to do!
Me too. I'm trying to be strong, but...

One way I look at it is that this sort of project is a good thing to be "investing" FIT income in. The first couple of years FIT went to a substantial set of ET's. This direction looks like a good next thing, but so many options & choices.

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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)
skyewright
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« Reply #19 on: July 07, 2013, 04:01:52 PM »

A late reply, but...

At the moment I use a second hand Powerware 9120 2000va UPS with 3 battery strings giving a theoretical 2.8kWhr capacity. It hasn't got a separate ring main, but feeds everything that I think is important - CH and solar controllers, computer routers and switches, PCs which monitor weather and various other things, phones etc.
Our background load is the same sort of things.
That gives about 14 hours of back up, but it wastes 80W when in line-interactive mode.
80W wow! That would double our background load!

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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)
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