Disabling LV alarm

sepsolman411
sepsolman411 Registered Users Posts: 16
Is there a way to disable the low voltage alarm buzzer on the circuit board in a pure sine wave inverter? Some manufacturers set the voltage alarm too high. The one I have starts buzzing at 11 volts. I want to disable the buzzer but not the shut-off function. Any advice is appreciated.

RCinFLA wrote: »
12.2 vdc open circuit is a nearly dead battery to start with.

If you have done the math correct, I assume your comment about a 1.5 kWH battery means a 125 AH, 12v battery. Maybe two Walmart Everstart MAXX-29 series.

Alarms on inverters are usually set for 10.5-11 vdc.

For that sized inverter, depending on total wire length, should be using at least #4 wire, preferred #2 wire.

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: battery voltage drop/inverter alarm
    Is there a way to disable the low voltage alarm buzzer on the circuit board in a pure sine wave inverter? Some manufacturers set the voltage alarm too high. The one I have starts buzzing at 11 volts. I want to disable the buzzer but not the shut-off function. Any advice is appreciated.

    Welcome to the forum.

    How comfortable are you with opening up your inverter and poking around inside it? Got a schematic? They're not all the same by any means. The bigger ones don't have an alarm; just a shut-down. But somewhere inside yours is likely a piezo-electric buzzer that screams like a banshee when battery death is imminent (sorry - bad jokes are my stock-in-trade). It is also likely to be this that sounds when other faults occur such as over-Voltage or over-current or whatever that particular unit is designed to complain about.
  • sepsolman411
    sepsolman411 Registered Users Posts: 16
    Re: battery voltage drop/inverter alarm

    I have already opened up the inverter and probed around looking for the buzzer on the circuit board. There is no schematic that came in the box and I looked online at the OEM. Here is the link to my PSW-500: http://www.12vgridtiepowerinverters.com/ProductProfile/PSW500-12-110. After thinking about the other variable faults that you mentioned, I now do not want to shut off the alarm. My quandary is how do I upgrade from a 35amp hour sealed lead acid battery to accommodate a 60 watt solar panel in a 5.50 hour solar day. In other words, do I basically need a 120 watt solar panel and a 100 amp hour 12 volt sla battery to run a few small appliances at night for a few hours? These appliances include a notebook computer, 3 cfl bulbs on a lamp, cell phone charger, printer, tv, and cable box but running all at one time.
    Welcome to the forum.

    How comfortable are you with opening up your inverter and poking around inside it? Got a schematic? They're not all the same by any means. The bigger ones don't have an alarm; just a shut-down. But somewhere inside yours is likely a piezo-electric buzzer that screams like a banshee when battery death is imminent (sorry - bad jokes are my stock-in-trade). It is also likely to be this that sounds when other faults occur such as over-Voltage or over-current or whatever that particular unit is designed to complain about.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: battery voltage drop/inverter alarm

    Do you have any way of measuring your AC power usage--such as a Kill-a-Watt meter or equivalent?

    Ideally, before you purchase any (more) solar pv/battery hardware, measuring your loads and defining your needs will help a lot.

    Generally, you would want to run a 100 AH 12 volt battery at a maximum of 10 amps * 5 hours for long battery life (50% maximum discharge, C/10 discharge rate):
    • 10 amps * 5 hours * 12 volts = 600 Watt*Hours
    With various losses, that is around 100 watts for 5 hours of AC loads...

    It could be done with that battery--But you probably would want more solar panels... The normal first cut estimate for running 500 WH per night with 5.5 hours of sun:
    • 500 WH * 1/0.52 system eff * 1/5.5 hours of sun = 175 watt minimum solar panel
    And that is assuming you get 5.5 hours of full noontime equivalent sun per day, or better (never plan on using 100% of available solar power every day--probably 50-75% of available average power per day).

    Of course, if you have backup power (grid, generator, etc.) or the loads are optional (don't use the TV+Cable tonight because there were clouds today).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Disabling LV alarm

    In terms of sizing batteries & panels you need to have a target number for your loads. As in 'X' Watt hours per day. That number divided by the system Voltage (in this case 12) gives you an approximate Amp hours needed. The battery needs to be at least twice that size. Then the panel should be sized to provide not only the "replacement" Amp hours during the available charge window (5.5 hours) but also the recommended potential peak charge current (5%-13% of the total Amp hour capacity).

    Is that confusing enough? :p
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Disabling LV alarm

    Just to be clear,

    All battery/charging calculations begin and end with the loads. Any other method merel results in chasing ones tail.

    Tony
  • sepsolman411
    sepsolman411 Registered Users Posts: 16
    Re: Disabling LV alarm

    Very good, I appreciate the prompt moderator feedback for answering my questions as well as how to calculate ac loads. Thanks to each of you. :D
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: battery voltage drop/inverter alarm
    ... to run a few small appliances at night for a few hours? These appliances include a notebook computer, 3 cfl bulbs on a lamp, cell phone charger, printer, tv, and cable box but running all at one time.

    WOW, speaking of loads, unless your shutting down in under 1 1/2 hours, that's more loads than I ran when I had a 220 watt array and 220ah 12 volt bank!

    I think you should look at how much your using, and the needs to use TV and Laptop at the same time, 3 cfl's at the same time, etc.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Disabling LV alarm

    that alarm is there for a reason and that is to protect the battery from being depleted too far. if the loads are too heavy for the battery capacity it will draw down the voltage quite a bit. it could also be that the battery has lost its capacity due to age and/or heavy cycling. as was suggested, you should pin down the loads more precisely over time with a meter like the killawatt. batteries should not be taken below 50% dod as a general rule. 50% of a 220ah 12v battery is 110ah and that translates into 1320wh plus there will be an extra draw for the operation of the inverter in the area of 10-30%. rounding this off to say 1500wh and over 2 hrs would represent 750wh of use per hour. it could be that the battery has been taxed too much too often an if you fail to reach a full charge with your solar then this compounds the problem by allowing the battery to not only go below 50% dod, but it can sulfate as well if it persists.

    i recommend checking the electrolyte levels with bringing it to a full and proper charge and the checking of the specific gravity of each of the cells.
  • april
    april Registered Users, Users Awaiting Email Confirmation Posts: 2
    niel said:
    Re: Disabling LV alarm

    that alarm is there for a reason and that is to protect the battery from being depleted too far. if the loads are too heavy for the battery capacity it will draw down the voltage quite a bit. it could also be that the battery has lost its capacity due to age and/or heavy cycling. as was suggested, you should pin down the loads more precisely over time with a meter like the killawatt. batteries should not be taken below 50% dod as a general rule. 50% of a 220ah 12v battery is 110ah and that translates into 1320wh plus there will be an extra draw for the operation of the inverter in the area of 10-30%. rounding this off to say 1500wh and over 2 hrs would represent 750wh of use per hour. it could be that the battery has been taxed too much too often an if you fail to reach a full charge with your solar then this compounds the problem by allowing the battery to not only go below 50% dod, but it can sulfate as well if it persists.

    i recommend checking the electrolyte levels with bringing it to a full and proper charge and the checking of the specific gravity of each of the cells.

    Thanks for this info - - my inverter is attached to a deep cycle battery and my understanding is that there is no harm in fully depleting this battery. The solar system it's attached too is just going to fill 'er back up the next day in my particular case. So then I don't understand why the inverter doesn't at least have an option for turning off the...BANSHEE-like alarm. I understand the high voltage alarm, and thus I am very reluctant to disable the squeal, however, are there inverters that are better/worse for deep cycle that have an option to disable?
  • april
    april Registered Users, Users Awaiting Email Confirmation Posts: 2
    BTW I am now aware that this thread is about 10 years old. The more things change...huh? :-)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Welcome to the forum April.

    Lead acid batteries--Their voltage is highly variable (state of charge, temperature, current flow and direction, age of battery, exact type of lead acid battery, etc.)... The (for a 12 volt inverter) is usually set to 10.5 volts battery cutoff... That is (roughly) the battery pretty much dead and very little energy left if you went below 10.5 volts.

    The 10.5 volts is there (more or less) to protect the AC inverter, not really the battery bank (to better protect the battery, 11.5 volts as the low voltage cutout is used by some vendors--More expensive inverters can have programmable LVD settings).

    The LVD is there to protect the AC inverter from excessive current on the DC side of the inverter, and to limit "brownouts" on the AC side (low AC voltage causing motors to overheat, etc.).

    For example, 1,200 Watts on a 12 volt inverter (inverters are "constant" power devices--The inverter "pulls" 1,200 Watts, and the lower the battery voltage, the more current the inverter draws):
    • 1,200 Watts AC * 1/0.85 inverter eff * 1/14.75 volts charging = 95.7 Amps DC input current @ 1,200 Watt AC load
    • 1,200 Watts AC * 1/0.85 inverter eff * 1/10.50 volts from "near dead" battery = 134.5 Amps DC input current @ 1,200 Watt AC load
    As you can see--The current draw varies a lot between running from the battery bank charging to battery bank nearly depleted.

    Also, with lead acid batteries--Ideally, you really do not want to discharge them below ~20% state of charge. As you get near zero (and possibly a weaker cell goes "reverse polarity"), the life of the battery bank can drop dramatically... Yes, forklift/traction batteries are routinely deap discharged--But they are immediately put on an AC battery charger at the end of the shift and fully recharged over the next 8-16 hours for the next shift. Not getting the bank on a charger for that 12+ hours right away can cause the bank to sulfate pretty quickly (a permanent loss of "free lead/sulfur" and reduction in battery capacity in days/weeks/months).

    With solar, we do have 10+ hours of "full sun" during the day (lots of Watts in middle of day, not much in morning and evening times). For most people in average conditions, it would take 2-3+ days of "sun" to recharge a 20% to 100% state of charge lead acid battery bank.

    For a full time off grid system--A pretty optimum lead acid battery bank would be size for 25% per day discharge--2x days of use (bad weather) to 50% state of charge. Then when the sun returns, the next several days to catch up to 100% SoC (and/or using a backup genset--especially during winter).

    More or less--A well maintained Lead Acid battery bank with good charging will last 2x longer if discharged to 75% state of charge vs discharging to 50% state of charge (deeper cycling, less cycle life). However--That 25% discharge requires a 2x larger battery bank--So over the life of the battery bank--You spend 2x more money for a bank that lasts ~2x longer--Not a big difference.

    An issue with lead acid battery banks is that they take time in "absorb" to fully recharge. And given the length of time the sun is in the sky--You can pretty much recharge a battery bank from 75% to 100% in 1 day--Whereas 50% to 100% SoC takes 2 days or more. Very roughly:
    • 10% rate of charge flooded cell lead acid battery bank:
    • 25% depth of discharge / 10% rate of charge = 2.5 hours of "bulk" charging
    • Absorb for a 25% discharge is ~2 hours
    • 2.5 hours of "bulk" plus 2 hours of "absorb" = 4.5 hours of charging
    • Going to 50% depth of discharge:
    • 50% depth of discharge / 10% rate of charge = 5 hours of "bulk" charging
    • Absorb for 50% discharge is ~6 hours
    • 5 hours Bulk + 6 hours absorb = ~11 hours of charging--Hard to get that many "Hours of Sun" charging in a single day (especially when winter rolls in)
    There are some ways to better address the charging time... Using tracking arrays--They get better AM and PM harvest energy and time.

    Or use other battery chemistry... LiFePO4 (lithium iron phosphate) batteries do not have the "absorb" time requirement--So you can hit them with "full" charging current until they are fully charged.

    Anyway--Yes, the above are suggestions on designing an off grid power system that will supply the loads with the energy you need reliably for many years. And you can "cut the corners" (smaller battery bank, larger array, backup genset, etc.)... Each solution has its own pluses and minuses. What works for one person may not be the best for somebody else.

    Generally--Highly suggest that you measure your loads and review them for efficiency (replace energy hogs with more efficient appliances--Use propane/etc. for heating & cooking, etc.)... It is almost always cheaper to conserve energy than to generate it.

    Once you know your loads--Then we can do a paper design of your system battery bank (AH and voltage, type of batteries), solar array, charge controllers, AC inverter, etc. Then you can start looking at actual hardware for cost and options that you may want.

    Feel free to start another thread about your energy needs and system design... And we can walk through the steps in a logical order. And it will make more sense than just "jumping" into the middle.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset