re-commissioning a system, new batteries

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re-commissioning a system, new batteries

Postby ralphday224 on Mon Dec 14, 2015 4:35 pm

Hi all
A friend of mine has had bad luck (experiences) with his off grid system. The original installer made a mess of things leaving the owner with a badly executed system. Undercharged batteries for the first year, no way to find out why (no generator either at first). The first set of L16's experienced a runaway charge event and many of the 16 batteries were toast. He ran a little longer on some scavenged/salvaged L16's.

He then installed a 10kw system like mine, straight feed to the grid, no net metering possible (or use of any of the power). At the same time an electrical service was installed for the house and the off grid system was de-commissioned. Batteries sold for scrap value.

My system (with batteries still) allows me to use the grid when I want, charge or just have the utility carry the loads and let renewables charge and or charge and charry all the loads. I think I've convinced my friend to get some batteries so he can still use the valuable MX60 and double Outback inverters etc, and use the solar power available to him.

Here's the question: How much battery capacity is required to really just have the system act like a big UPS? Cost is a factor. Enough battery to be off grid for 3 days...not needed, the propane generator is always available still. 1.8kw of pv, 2x 3600watt OB inverters and one MX60. I'm thinking a minimum of 400amp hours (48 volt system). AGM would be better than FLA's, time and inclination to work with FLA's is lacking on his part.

Contributions and suggestions are appreciated.

Ralph

Also posted on WindSun forum
ralphday224
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Re: re-commissioning a system, new batteries

Postby SandyP on Mon Dec 14, 2015 4:58 pm

ralphday224 wrote:.....1.8kw of pv, 2x 3600watt OB inverters and one MX60. I'm thinking a minimum of 400amp hours (48 volt system). .....



Given the 1.8kw of pv, 400ah of batteries would be the maximum suitable while ensuring a reasonable charge rate should the batteries be discharged.
SandyP
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Posts: 226
Joined: Tue Jun 21, 2011 4:44 am
Location: Victoria, Australia
My RE system: 8 x 190W 24V Suntech panels (4 strings of 2)
Mate2
Outback FM60 MPPT
12 x 2V Hoppecke GEL 660 Ah C100 - 24V System
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset

Re: re-commissioning a system, new batteries

Postby ralphday224 on Mon Dec 14, 2015 5:12 pm

For re-charge there's solar, generator and utility. So the batteries are really just to enable the use of the inverters/solar power available.

Ralph
ralphday224
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Posts: 38
Joined: Sat Mar 07, 2015 4:25 pm

Re: re-commissioning a system, new batteries

Postby SandyP on Tue Dec 15, 2015 12:36 am

ralphday224 wrote:For re-charge there's solar, generator and utility. So the batteries are really just to enable the use of the inverters/solar power available.

Ralph


OK, so as referred to on WindSun, what is the expected maximum constant power usage (drawing on the batteries as a UPS) and for what time period? In other words how long do you want the batteries to provide power before you start the generator and what will the total power load be during this time?
SandyP
OutBack Guru
 
Posts: 226
Joined: Tue Jun 21, 2011 4:44 am
Location: Victoria, Australia
My RE system: 8 x 190W 24V Suntech panels (4 strings of 2)
Mate2
Outback FM60 MPPT
12 x 2V Hoppecke GEL 660 Ah C100 - 24V System
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset

Re: re-commissioning a system, new batteries

Postby ralphday224 on Tue Dec 15, 2015 6:04 am

Ok, more investigation needed.

Ralph
ralphday224
OutBack Whiz
 
Posts: 38
Joined: Sat Mar 07, 2015 4:25 pm


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