boost voltage charging time

Fabian
Fabian Registered Users Posts: 131 ✭✭
in General Solar Power Topics #1
How long should a charge controller remain at the Boost Voltage before switching to float charge mode? I have a charge controller which is set at 2hrs default and then afterwards it goes into float mode.

I have  (2) epever 40ah mppt charge controllers which are charging 2 different battery banks which the default time is set to 2hrs for both of them to remain at the boost voltage mode.

I have (2) SLA deep cycle battery bank. One is 12v at 380ah 14.4v boost and the other is 24v at 380ah 28.8v boost.

Should each controller remain at the 2hrs default for the boost voltage or how much time would be the recommended time to remained at the boost voltage before going into float mode?
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    The "best" time varys according to the depth of the discharge, and remaining sunlight .  So you sort of average it out and use the water consumption to dial it in.   No water usage = need more absorb time.   Gallons of usage = less absorb time
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited May 2019 #3
    The boost voltage is nothing anomaly high, but it would be prudent to follow the battery manufacturers requirements, as there is no  battery  temperature stated, it'is difficult to answer such an open ended question. 

    With more sophisticated controllers there is provision for a remote temperature sensor which automatically corrects the charging voltage in proportion to the battery temperature. Generic settings are like a one size fits all, which may, or may not, be correct your particular battery requiments, so without details its impossible to answer with any accuracy.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    #4
    This is one of the issues that caused me to replace my EP Solar aka EP Ever controllers with fully programmable controllers, a generic one size fits all battery charge algorithm or one tailored to the exact battery manufacturers recommendations.  The 14.4 volt and 28.8 volt settings are typical of large format flooded lead acid batteries and all my AGM batteries have a lower absorb setting. I use the manufacturers recommendations as a starting point, not some one size fits all charge regimen as used by EP Solar. They also wander in voltage offset as seen by the controller vs. the true battery voltage as seen by a good DVM.
    david 
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    #5
    mcgivor said:
    The boost voltage is nothing anomaly high, but it would be prudent to follow the battery manufacturers requirements, as there is no  battery  temperature stated, it'is difficult to answer such an open ended question. 

    With more sophisticated controllers there is provision for a remote temperature sensor which automatically corrects the charging voltage in proportion to the battery temperature. 

    In regards to the statement above if I install the battery temp sensor which comes with the charge controller I could then let the settings remain at 14.4v for the boost voltage for the SLA battery and maintain the 2hrs boost time or push it to 3hrs?

    But if there is no temp sensor install it would be best to reduce it to 14.1v and still maintain the 2hrs boost charging time? or let it stay at 14.4v 2hrs boost?

    I realize that at the 14.4v 2hrs boost for the sla battery the battery bank gets a slight temp at the ending process I don't have the temp sensor install yet so I don't exactly know how high it is but it is slightly above warm. 
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #6
    Again, Check battery specs. Many sealed batteries these days have higher charging voltage requirements than the old standard voltage settings. This particular AGM battery states, for cyclic use 14.4 - 15 volts.


    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    #7
    The battery that i have is a PowerSafe SBS 12v 190Ah SLA. I only found  float charge rating for it on the net which is 13.6V.
    The battery is used on telecommunications site so there is no cyclic voltage rating stated.
    So would it be ok to use a setting for it 14.4v for boost for 2hrs at that voltage reading then go into float at 13.6v?
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited May 2019 #8
    Since there is a remote temperature sensor, use it, the charging voltage will auto adjust, typically 0.030V per °C ( 0.017V per °F) for 12V, as the battery temperature increases above 25°C nominal , the voltage decreases, similarly the temperature  decreases below 25°C, the voltage increases ( double these vaues for 24V ) 

    Looking at a Morningstar manual 14.4V is considered an equalization voltage for a sealed battery on its highest setting, not something to do on a daily basis and equalization is something only recommend by only a few manufacturers. The Morningstar absorption voltage for sealed LA batteries  is 14, 14.15 and 14.35V respectively, can the settings be customized via a PC?  I'm thinking you may want to set the boost to zero hours, and set the absorption to what the manufacturer recommends, if available. Can the battery make and model be provided ? this would help in determining what the settings should be.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #9
    Here is the battery page from the MFG (I think):

    https://www.osibatteries.com/p-18485-enersys-powersafe-12v190f-battery-12v-190ah-front-terminal.aspx

    And here is the manual:

    https://www.osibatteries.com/images/document/POWERSAFE-V-FRONT-TERMINAL-INSTRUCTIONS.pdf

    They do suggest a 24 hour charge (10% of C8 capacity) at 2.25 to 2.27 volts per cell (13.62 volts @ 12 volt), for a maximum of 96 hours.

    There is an alternative charging at 2.40 volts per cell (14.40 volts @ 12 volt) for 24-48 hours (after discharge).

    These seem to be for UPS/Float/Standby usage... But they are AGM, and 14.40 volts for "Absorb" charging is normal. With other AGM batteries, typically Absorb is somewhere around 2-8 hours (same as FLA)... With shallow discharge closer to 2 hours, and deep cycle (50% or lower state of charge) would be in the 6-8 hour range.

    Of course, with solar, you are not going to get much more than 6-8 hours of charging on a normal day anyway before the sun sets.

    You might want to contact the Mfg/distributor for the battery and suggest your proposed usage/charging cycle and see if they have any opinion. Going to the engineering source is usually a good idea (they may just tell you to read the manual--who knows).

    -Bill


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    #10
    Tecnodave said:
    This is one of the issues that caused me to replace my EP Solar aka EP Ever controllers with fully programmable controllers, a generic one size fits all battery charge algorithm or one tailored to the exact battery manufacturers recommendations.  The 14.4 volt and 28.8 volt settings are typical of large format flooded lead acid batteries and all my AGM batteries have a lower absorb setting. I use the manufacturers recommendations as a starting point, not some one size fits all charge regimen as used by EP Solar. They also wander in voltage offset as seen by the controller vs. the true battery voltage as seen by a good DVM.
    david 
    In regards to the statements above. If I decide to keep my epever charge controller instead of buying the more advance charge controllers would using the temp sensor with it lets my battery bank charge properly even with the wandering voltage offset that do occurs with it sometimes so if the voltage even wander off sometimes and soon after the battery temp starts to rise then the temp sensor would enable the CC to bring back the voltage to acceptable levels and prevent thermal runnaway?
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  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    #11
    Temperature sensors will compensate for temperature of the battery vs temperature of the controller. They will not correct a controller that wanders in the basic setting. I hear that newer EP Solar controllers do now have a user adjustable setting and that is a good step forward, but advanced controllers have a factory calibration offset to correct for voltage wander. My MidNite controllers do have such a procudure to for end user correction and MidNite has a pot on the board that will recalibrate it. I seen posts on MidNite forum as to the procedure, I've not needed to do that. I nearly destroyed a $1000 battery set and spent hundreds on fuel to top off my batteries when I had ample solar available.
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    #12
    With my mt50 box that Is connected to the epever controller It gives me full control to adjust the settings. So in relation to the voltage wandering. If i set my boost voltage to 14.2v would that be sufficient for the sla battery that I have and would that compensate for when the voltage sags sometimes in going up or going down by 1 to 2 digits so in this case it would wander between 14.1 to 14.4v during the boost stage.Would that be ok?
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #13
    You'll want to check recommended max absorb/boost voltage for your specific battery.  In general, setting absorb/boost voltage down a bit may require extending cycle time a bit to get fully charged.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    #14
    All my AGM have a factory recommended absorb (boost) voltage of 14.3.  But different manufacturers will vary a bit. I'm using CD Technologies 105 a.h.  model TEL 105FS Cell phone tower batteries for standby power system.  These are salvaged from cell phone towers..Federal law requires change out at 12 months and I get them from the service company as scrap.
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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