Battery charging

Discussion about the MX60 Charge Controller

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Pgreco44
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Posts: 2
Joined: Sat Sep 03, 2022 6:43 am
My RE system: Flexmax 60, 2 , 250w 24v panels, 6, 12v 110amp deep cycle lead acid batteries

Battery charging

Post by Pgreco44 »

I'm a little new to this but here is my question. I'm not sure if I a problem or not. I have a small off grid camp running 2-250w 24v panels, using a flexmax 60 controller, 6-12v 120amp deep cyc batteries. Everything works perfectly with no problems except I noticed when sunset comes and the panels shutdown my battery voltage drops significantly. It is 14.3v all day then drops to 12.4 at sunset. Is this normal or do have a wire crossed or a back feed. It holds there but I'm concerned if my well pump kicks on over night it will trip out. Thanks much Paul
raysun
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My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Battery charging

Post by raysun »

Can you tell us a bit more about the system?
Brand/model of solar panels.
Brand/model of battery.

Is this strictly DC, or is there an inverter producing AC?
Last edited by raysun on Wed Sep 07, 2022 5:26 pm, edited 1 time in total.
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bluespur
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My RE system: VFX3024x2
Flexmax60x2
3000W total solar, 135w panel array and 220w panel array
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12xHawker Perfect Plus 8PZS120 FLA batteries
Own built generator Kubota D600 engine, 7.5Kw gen head

Re: Battery charging

Post by bluespur »

sounds normal to me, sounds like the battery is coming to a resting voltage from float
raysun
Forum Emperor
Posts: 8601
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Battery charging

Post by raysun »

bluespur wrote: Wed Sep 07, 2022 4:55 pm sounds normal to me, sounds like the battery is coming to a resting voltage from float
Good observation. Depending on the load when the voltage is measured, 12.4V could be in the high 90's% state of charge.
Pgreco44
Forum Junior Member
Posts: 2
Joined: Sat Sep 03, 2022 6:43 am
My RE system: Flexmax 60, 2 , 250w 24v panels, 6, 12v 110amp deep cycle lead acid batteries

Re: Battery charging

Post by Pgreco44 »

The system I'm using is
2- ss250P-60 24v panels
5- 12volt 110amp deep cycle lead acid batteries
Flomax 60 mppt controller
Sunforce 3500 watt pure sine wave inverter
All lighting is 12v, fridge, hot water, stove are propane.
110v is mainly for well pump and internet. During the day we use it for many reasons waether permitting.. grinding coffee, running vacuum, power tools ect:.
My concerns are after sunset when my battery voltage drops off to 12.4 from 14.4 if my pump kicks in it usually drops off to 12.2. I guess I could just leave it on all night and see what happens. I'm just worried about dragging it to low and damaging something. Any input would be greatly appreciated. I hope I didn't confuse anyone to much. Thank you Paul
706jim
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Posts: 56
Joined: Tue Apr 28, 2020 10:52 am
My RE system: 7x330 watt Canadian solar panels 8x370 ah Trojan L16's Flexmax 80 Trace DR1524 Msw inverter installed 1994 and still working great
Location: Thunder Bay Canada

Re: Battery charging

Post by 706jim »

Those high voltages during daytime charging always drop down with the setting sun. 12.4 actually sounds about right. And if you apply loads during the non sun period, the voltage will drop further.
raysun
Forum Emperor
Posts: 8601
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Battery charging

Post by raysun »

Its helpful to have a quality battery monitor on the system.
Simply tracking voltage is tricky because it's load-dependent. Also, as has been pointed out, during charging, battery voltage is held artificially high.
The most useful monitors track current into (charging) and out of (discharging) the battery. With this information, they can derive battery state of charge (SoC).
If you have a smartphone with Bluetooth, a good monitor is the Victron SmartShunt.
https://www.amazon.com/Victron-SmartShu ... 1260&psc=1
One shunt terminal connects to the battery negative terminal with a short, heavy battery cable (not included) and the existing cable between the battery and the loads connects to the other terminal. The Victron SmartConnect software runs on your phone and gives real-time battery status.
In the cheap Chinese clone category, a monitor that is a clone of the Victron BMV700 series would be better than nothing: https://a.co/d/d51dwdw
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