Trying to decide which battery for 3 - VFX3648 system

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Trying to decide which battery for 3 - VFX3648 system

Post by Surmamma »

Hi, I feel a little bit stupid asking this, but here goes....been trying to collect info, but I’m having a tough time. I have been on an old DIY offgrid solar system for over 30 years, using a still working Trace 2012 inverter, Tri metric meter, Heliotrope CC60 charge controller and since 2004 a HUP Solar One 1690 AH 12v battery. My Panels were a somewhat mixed array of 14 panels. I’m finally upgrading!
I have been on a construction job where a nice system was installed for the owner, around 2010-2013 and it had 2 outback VFX3648 inverters which were added to, to make a 4 vfx3648 system. The owner had sealed Rolls Surrette batteries which took up a small room space. He has since upgraded to a far more complex system with radian inverters and Simpliphi lithium 3.8 kWh batteries, and I was given his old vfx3648 inverters, and some other components which include a Mate 3S and a Hub10.3. I have purchased 12 new Canadian Solar 320 watt panels, and an FM 100 charge controller. I’m trying to decide on my battery system but am leaning towards Discover 7.4 kWh or some Simpliphi 3.8, with the idea that I could start with 2 or 3, and add batteries as I could afford to, to the system over the next year or 2, using lithium based batteries over FLA batteries.
However, I’m having a difficult time finding info on using them with 3 of the (I’ll keep the 4th one as a spare)
VFX3648 inverters that I want to set up, and or, the correct charging configuration levels. I know I may need other components, some of which I may have that I may not have mentioned and some that I don’t yet have. I’m also wondering if the VFX Inverters were not really designed to work with the lithium ion batteries, and if I might be better off going with an AGM battery set up, and if so, which one might be most cost effective. Could you give me some advise on pursuing the lithium ion batteries or if I might be better off going with an AGM FLA battery, and waiting until a new battery is invented or bugs worked out more for the Lithium ion batteries.
Thank you, John
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Re: Trying to decide which battery for 3 - VFX3648 system

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Hi John! Welcome to the forum! Glad we got you registered and posting.

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My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
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Re: Trying to decide which battery for 3 - VFX3648 system

Post by raysun »

Three VFX3648s can deliver a lot of power, and consume a lot of battery capacity doing so.

How will the three inverters be configured? Parallel stacked - 120V single phase @ 10kW? Three phase?

In any event, the leading Lithium battery vendors are on your short list. Both SimpliPhi and AES Discover are quality batteries. Outback and SimpliPhi have done a good amount of integration testing of their respective products, and there is a wealth of information on proper deployment. Most folks, including myself, using lithium batteries here have opted for SimpliPhi, partly on the strength of that testing. You can check Outback and SimpliPhi sites for application notes, integration guides, and warranty requirements.

Whether or not to invest in lithium today or wait for some future battery development / price drop is tough to answer. No doubt both will occur. When and in what form is purely speculation. Its not easy bringing new battery technologies to market. The industry is littered with very promising failures. Next to lead acid, lithium is the most utilized and successful chemistry. For fixed storage, LiFePO4 is the hands-down choice for a good balance between performance and safety.

Deploying a battery to support a 10kW inverter infrastructure will be costly no matter the chemistry. If opting for sealed lead acid, the Outback offerings are worthy of consideration. If choosing SimpliPhi, following their deployment guidelines for battery sizing will be necessary to maintain their warranty requirements. I don't know about AES Discover in this regard.

I'd highly recommend adding the Outback FLEXnet DC battery monitor to the system. It will be an important addition for a Lead Acid battery, and a critical addition for Lithium. The latter due to the fact the VFX inverters do not have provisions to implement proper Low Battery Cut Out, or High Battery Cut Out, in the voltage ranges needed to protect lithium batteries. The FNDC can be used to do so, and with the potential of high current draw from a minimum capacity (to start, per your plan) battery, its fast response to LBCO conditions may prove critical.
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