How to calculate Charger AC Limit for VFXR3648A

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lrperez99
Forum Member
Posts: 16
Joined: Thu Jan 11, 2018 6:09 am
My RE system: SYSTEM : BDL-BF23
Dual INV VFXR3648A 3.6 each
24 PV panels @ 305w ea
Two CC FM80-150VDC
FN-DC FLEXNet DC
Gateway device MATE3S
Battery 48v, (24 batteries @ 2v ea) 730 amps Flooded lead-acid
Location: Trujillo Alto, Puerto Rico

How to calculate Charger AC Limit for VFXR3648A

Post by lrperez99 » Fri Feb 14, 2020 10:10 am

Hi,
I need help to calculate Charger AC Limit (at AC input tab) for dual VFXR3648A. I read the fxr operator manual but still have doubts about the calculation. Current setting is 18AAC. I wonder if this setting is ok. System is working fine, just looking for improvements.
I have:
Dual INV VFXR3648A 3.6 each
Battery 48v, (24 batteries @ 2v ea) 730 amps Flooded lead-acid
24 PV panels @ 305w ea
CC FM80-150VDC
FN-DC FLEXNet DC
Gateway device MATE3S

Thanks,
Luis

JRHill
Forum Czar
Posts: 745
Joined: Thu Feb 17, 2011 11:12 am
My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Honda EU7000is w/2 wire auto start via VFX aux, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Tristar 45 Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with various upgrades and workarounds.
Location: South central WA
Contact:

Re: How to calculate Charger AC Limit for VFXR3648A

Post by JRHill » Fri Feb 14, 2020 10:36 am

lrperez99 wrote:
Fri Feb 14, 2020 10:10 am
Battery 48v, (24 batteries @ 2v ea) 730 amps Flooded lead-acid; 24 PV panels @ 305w ea
More info needed:
- What's your AC source? If a generator, what's the kWh rating?
- What are the daily current demands of your connected AC devices? And really important what are the possible surge loads of one or maybe several high loads cycling in very close time periods while charging batteries at the same time?
- Nice battery bank. What brand and model are the batteries? The best recharging current is dependent on the specifics of their output which would be a guess at this point.

Best,
Jim

raysun
Forum Emperor
Posts: 1687
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: How to calculate Charger AC Limit for VFXR3648A

Post by raysun » Fri Feb 14, 2020 10:48 am

lrperez99 wrote:
Fri Feb 14, 2020 10:10 am
Hi,
I need help to calculate Charger AC Limit (at AC input tab) for dual VFXR3648A. I read the fxr operator manual but still have doubts about the calculation. Current setting is 18AAC. I wonder if this setting is ok. System is working fine, just looking for improvements.
I have:
Dual INV VFXR3648A 3.6 each
Battery 48v, (24 batteries @ 2v ea) 730 amps Flooded lead-acid
24 PV panels @ 305w ea
CC FM80-150VDC
FN-DC FLEXNet DC
Gateway device MATE3S

Thanks,
Luis
Inverter charger question aside for the moment.

Do you truly have 7.2kW of solar panels on a single FM80 charge controller? That's nearly double the FM80 's rated capacity @ 48V. I urge you reconsider this configuration as, it voids the FM80 warranty, and it sets up the likelihood of overload with potential to damage both the FM80 and the battery bank. That many panels would easily be controlled by splitting them between two FM80 charge controllers.

Back to what you asked.

The charger at 18 AC Amps input would produce roughly 18A x 120V / 48V x .8 ~ 36 DC amps charging current. If two inverters are charging, then 72 DC A. About right for the capacity of the battery.

lrperez99
Forum Member
Posts: 16
Joined: Thu Jan 11, 2018 6:09 am
My RE system: SYSTEM : BDL-BF23
Dual INV VFXR3648A 3.6 each
24 PV panels @ 305w ea
Two CC FM80-150VDC
FN-DC FLEXNet DC
Gateway device MATE3S
Battery 48v, (24 batteries @ 2v ea) 730 amps Flooded lead-acid
Location: Trujillo Alto, Puerto Rico

Re: How to calculate Charger AC Limit for VFXR3648A

Post by lrperez99 » Fri Feb 14, 2020 10:59 am

Thanks for your response. My AC source comes from electric company, I am using "Grid Tie".
Daily current demands of your connected AC devices - around 20kWh.
Possible surge loads of one or maybe several high loads cycling in very close time periods while charging batteries at the same time - 3kWh
What brand and model are the batteries? - Power-Hawk, file attahed.
Power-Hawk-Solar Product Specifications Crown 2018-04A.pdf
Power Hawk batteries
(1.83 MiB) Downloaded 66 times
I have two FM80 charge controller.

raysun
Forum Emperor
Posts: 1687
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: How to calculate Charger AC Limit for VFXR3648A

Post by raysun » Fri Feb 14, 2020 11:03 am

lrperez99 wrote:
Fri Feb 14, 2020 10:59 am
I have two FM80 charge controller.
Whew! ;)

JRHill
Forum Czar
Posts: 745
Joined: Thu Feb 17, 2011 11:12 am
My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Honda EU7000is w/2 wire auto start via VFX aux, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Tristar 45 Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with various upgrades and workarounds.
Location: South central WA
Contact:

Re: How to calculate Charger AC Limit for VFXR3648A

Post by JRHill » Fri Feb 14, 2020 12:04 pm

lrperez99 wrote:
Fri Feb 14, 2020 10:59 am
Possible surge loads of one or maybe several high loads cycling in very close time periods while charging batteries at the same time - 3kWh
Let me rephrase the question: "Possible surge loads of one or maybe several high loads cycling" is not asking the daily draw but the instantaneous draw of the device(s). For example, a well pump may draw, for example only, 7aAC running. But when it starts up, whoa $hitsky, it draws many times that and ramps down quickly as it does its work. If you have other stuff that may cycle or consistent high loads running in the same time period then the only thing the inverter can do is kick out the charging. If the loads ramp up or down *kindly* and within reason, the inverter will adjust to that. THIS ONLY HAPPENS ON AC POWER INPUT TO THE INVERTER. When AC comes in it feeds all connected circuits and charges your batteries at the same time. If the incoming is insufficient the AC is "kicked off" and you go to inverter power until things come into acceptable ranges.

I have always avoided inverter fail over like the plague. It is a safety thing for both you and the equipment. It really works well. But you don't want to have a system that has to use that safety feature regularly. So there are bunches of calculations and engineering but I'd ask this: Monitor your system. If you detect the inverter dropping the AC in then you need to make changes.

lrperez99
Forum Member
Posts: 16
Joined: Thu Jan 11, 2018 6:09 am
My RE system: SYSTEM : BDL-BF23
Dual INV VFXR3648A 3.6 each
24 PV panels @ 305w ea
Two CC FM80-150VDC
FN-DC FLEXNet DC
Gateway device MATE3S
Battery 48v, (24 batteries @ 2v ea) 730 amps Flooded lead-acid
Location: Trujillo Alto, Puerto Rico

Re: How to calculate Charger AC Limit for VFXR3648A

Post by lrperez99 » Fri Feb 14, 2020 12:17 pm

Thanks for the advise. My system is working fine, I will follow your recommendation to monitor the system for any dropping in the AC.

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