[RE-wrenches] FX Inverter as a dumb charger

[John Blittersdorf]

William,
I have a customer with the Flexware 500 and 2 GVFX3648's  He put in a 120V
generator later and wanted to use it automatically for a grid backup.  We
we installed a
VFX3648 as a separate battery charger to charge the 2 Fortress LFP10
batteries during an outage when there was insufficient sun.  It has its own
basic MATE to set up the AGS.
Works great.  We talked about also adding an outlet on the AC output side
for a last ditch emergency power source but could also have a dedicated
generator outlet.  We left that for later.

On Sat, Nov 29, 2025 at 12:05 AM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Bill:
>
> I have too many generator amps but not enough battery charge amps. A
> transformer will balance the generator but won’t increase charge amps.
>
>
> William Miller
> Miller Solar.com
> 805-438-5600
> www.millersolar.com
>
>
> On Fri, Nov 28, 2025 at 3:46 PM Bill P. Battagin via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> William,
>>
>>               Assuming the 12KW generator has 240 volt output, run the
>> 240V through a transformer and double your 120 volt amps.  I guess if you
>> have a spare OB 3648 in the boneyard then you would be saving the cost of a
>> transformer.
>>
>> Bill
>>
>> Feather River Solar Electric
>> Bill Battagin, owner
>> 4291 Nelson St. (Freight)
>> 5575 Genesee Rd <https://www.google.com/maps/search/5575+Genesee+Rd?entry=gmail&source=g>. (USPS, UPS)
>> Taylorsville, CA  95983
>> 530-284-7849, 258-1641(cell)
>> CA. C10 Lic # 874049
>> Solar Powered since 1982
>>
>>
>> ------------------------------
>> *From: *"Jay via RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>> *To: *william at millersolar.com, "RE-wrenches" <
>> re-wrenches at lists.re-wrenches.org>
>> *Cc: *"Jay" <jay.peltz at gmail.com>
>> *Sent: *Friday, November 28, 2025 11:31:50 AM
>> *Subject: *Re: [RE-wrenches] FX Inverter as a dumb charger
>>
>> Hi william
>>
>> Yes I’ve done it many times without issues
>>
>> On Nov 28, 2025, at 11:41 AM, William Miller via RE-wrenches <
>> re-wrenches at lists.re-wrenches.org> wrote:
>>
>> Friends:
>>
>> One of my clients has one VFXR3648A inverter connected to 8 L16
>> batteries. We upgraded their generator to 12 kW.
>>
>> One leg of the generator is unloaded and the batteries can accept twice
>> the charge current one FX can provide. It seems another inverter is called
>> for.
>>
>> I have several functional VFXR3648 inverters on the shelf. I know I can
>> not mix versions of the inverter in the hub. Could I connect a VFX3648 to
>> the unused generator leg and battery bank but not the hub as a ‘dumb’
>> charger?  I would plug in a Mate just long enough to verify settings.
>>
>> Has anyone tried this?  Thanks in advance for any advice.
>>
>> William Miller
>> Miller Solar.com
>> 805-438-5600
>> www.millersolar.com
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