18.4V coming in but only 12.8V going into battery bank

Discussion about the MX60 Charge Controller

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raysun
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My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
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REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
Honda EU7000is gas fuel generator

Re: 18.4V coming in but only 12.8V going into battery bank

Post by raysun »

pioneerMan wrote: Fri Jan 01, 2021 12:28 pm I appreciate all of this advice. It seems so time consuming, however, that it almost makes more sense to run a propane generator 24/7.

Ugh.

:sad:
Managing a large battery is effort-laden, there is no doubt. It's one of the reasons for "right-sizing" the battery to reflect consumption and reasonable charge cycles.

IMO, installing a very large battery in order to provide several "days of autonomy" is a two-edged sword. Installed cost is high, as is maintenance effort. Bottom line, all energy used from the battery must be replaced, and for lead acid batteries, the sooner, the better, as being left in partial state of charge contributes to shortened service.

Many of we off-grid folks live with our systems full time. Solar PV panels operate on a daily cycle. It makes sense to maintain the battery attuned to that daily cycle. What gets used from the battery gets put back the next day.

Were this my system, I'd take the following steps:

#1 Assess daily consumption.
Get a good picture of the average usage in Kilowatt Hours.

#2 Size the battery to to support the average daily consumption.
The large number of battery blocks, and attendant connections, make for a high-maintenance battery. Imbalance between cells caused by slight charging variations, corrosion on connectors, etc., inevitably leads to accelerated deterioration of some blocks, and shortened battery life overall. I'd go through the exercise of testing each battery block for health. Measuring specific gravity of each cell is the most precise, but a simple open circuit voltage test will suffice. On charged battery blocks, the lowest readings will indicate the lowest health. Select the blocks with the best readings, and reconfigure them into the battery. A useful target would be a battery capacity that would discharge 35-40% daily, with 50% being the maximum discharge.

I'm only guessing here, but think about half or more of the blocks in the current battery are likely nearing end of life or have dead cells.

Use the best, corrosion-free conductors to reconfigure the battery. Conductors that have the same current carrying characteristics. Having mixed conductors is a recipe for shorter battery life.

Its going to be a good deal of work, but in the end the system will be far more stable.
sodamo
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Re: 18.4V coming in but only 12.8V going into battery bank

Post by sodamo »

Not me. Gen uses about 1.7 gal/hr. @$5/g pretty sooon I wouldn’t need electricity. 😁
David
Please visit http://vacation.ninolehawaii.com
pioneerMan
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My RE system: 12 volt system
26 lead acid batteries, 6V, each rated at 210 amp hours
12 solar panels (Mitsubishi 125 Watt)
Outback VFX2812 inverter and two FLEXmax 60 inverters
Trimetric 2030A battery monitor
Mate 3d
Dual fuel 4500 watt AC generator
Location: Northern Utah

Re: 18.4V coming in but only 12.8V going into battery bank

Post by pioneerMan »

fcwlp wrote: Tue Dec 22, 2020 11:56 am @pioneerMan, please post what your float, absorb and EQ settings are on both the charge controller and inverter.
How come there are settings for float, absorb and EQ in both the inverter and charge controller? Doesn't that create conflict or errors if the settings on one device differ from the settings on another device? Which device takes precedence? This doesn't seem like a good way if the goal is to make the hardware easy to use. Or am I missing something here?
raysun
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Posts: 4554
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
Honda EU7000is gas fuel generator

Re: 18.4V coming in but only 12.8V going into battery bank

Post by raysun »

"Easy to use is easy to say."
- anon IT proverb from the '80s

I don't think anyone ever said system software was easy to use, those of us who live with it really want it effective to use.

Whenever I see a Wizard, Auto-config, or EZ Button, I defeat them. If they cannot be defeated, I run away.

On to your actual question.

All of the chargers are designed to opererate autonomously. That means each has a collection of settings that governs its activity.

All of the chargers can be caused to work in sync, because they use a common control metric - battery voltage.

The first step in syncing the functionality of all available chargers is to assure they all read the exact same battery voltage. That means the following:
• The battery voltage measured at the respective devices' Battery +/- terminals must be identical. If there are variances, as measured with an accurate voltmeter, then the wiring between the battery bus and the device Battery +/- terminals is suspect. Check for corrosion, loose connections, undersized wire, failed components like circuit breakers that may be in-line. Address all issues until the voltages at each device reads the same when measured with a voltmeter.

• The battery voltage measured by each devices' internal voltmeter should read identically. If the charge controllers OUT voltage, and the inverters battery voltage, as read internally, are different, the units should be calibrated to bring them into agreement. There are Calibrate functions for this purpose accessible from the Mate for the inverter and charge controllers. The CC's have it on their Misc menu as well, IIRC.

• Each device needs to be programmed, preferably individually, with the proper charging profile parameters. The two FM charge controllers should be programmed identically, and if calibrated correctly, will operate in sync.

The inverter can be programmed with the same profile parameters, but is often programmed with Absorb and Float voltages 0.1 - 0.2V lower than the solar charge controllers. This will permit the CCs to have "priority", using all available solar harvest if both CCs and Inverter charger are used simultaneously. EQ is a toss-up, solar is generally not sufficient consistency or duration for a proper EQ operation, so its usually left to the inverter charger.
pioneerMan
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Posts: 99
Joined: Wed Jan 09, 2019 3:40 pm
My RE system: 12 volt system
26 lead acid batteries, 6V, each rated at 210 amp hours
12 solar panels (Mitsubishi 125 Watt)
Outback VFX2812 inverter and two FLEXmax 60 inverters
Trimetric 2030A battery monitor
Mate 3d
Dual fuel 4500 watt AC generator
Location: Northern Utah

Re: 18.4V coming in but only 12.8V going into battery bank

Post by pioneerMan »

raysun wrote: Fri Jan 01, 2021 1:16 pm Use the best, corrosion-free conductors to reconfigure the battery. Conductors that have the same current carrying characteristics. Having mixed conductors is a recipe for shorter battery life.
Does this mean that it was a bad idea to introduce the copper pieces considering the bolts to tighten things down are made of steel?
raysun
Forum Emperor
Posts: 4554
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
Honda EU7000is gas fuel generator

Re: 18.4V coming in but only 12.8V going into battery bank

Post by raysun »

pioneerMan wrote: Sat Mar 27, 2021 3:23 pm
raysun wrote: Fri Jan 01, 2021 1:16 pm Use the best, corrosion-free conductors to reconfigure the battery. Conductors that have the same current carrying characteristics. Having mixed conductors is a recipe for shorter battery life.
Does this mean that it was a bad idea to introduce the copper pieces considering the bolts to tighten things down are made of steel?
Galvanic corrosion is a pernicious issue in electrical distribution systems.

If mating copper to steel, high quality stainless steel is usually specified, and dielectric grease often used.
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