Magnum MS4024PAE vs. MS4448PAE

WxboyWxboy Solar Expert Posts: 70 ✭✭✭✭
My father currently uses on old Trace modified sine wave inverter/charger as night time battery backup during power outages and run the generator during the day. He is looking to buy a new PSW inverter/charger that can run 120 and 240 so he's looking at the 2 Magnums in the subject line. He knows the advantages of the 48 volt unit(lower amp draw based on the higher voltage and a little more rated power) but he asked if there were any disadvantages. They are the same price so I was pushing him toward the 48 volt. Please let me know what you think.

Currently he has 6 12 volt batteries set up on 2 battery switches so he can charge in banks of 2 and then when he draws power at night he can switch to all 6 if he needs to. He bought the batteries 2 at a time so they are slightly different ages and he grouped them together by age. They are deep cycle agm batteries, 100 amp hour. I told him one small disadvantage to the 48v is that he would only be able to hook up 4 of his batteries or buy 2 more and have 2 banks of 4. He realizes using batteries of different ages is not ideal but this is just for backup power so none of the batteries have been cycled more than a few times.

Thanks in advance for your feedback.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,230 admin
    Re: Magnum MS4024PAE vs. MS4448PAE

    Does he need 24 VDC for anything (there are more 24 volt small water pumps, lights, and appliances--such as for long haul trucks/boating--Than for 48 volt systems).

    I don't like parallel battery banks--So keeping the paralleled battery strings to 2-3 maximum is my personal choice. There should be a fuse/breaker per string for safety.

    Look at generator to battery bank charging capacity (5% to 13% typical range, ~25% recommended maximum charging current--Although AGM will take more current than flooded cell). I like to have the minimum size generator needed to keep fuel efficiency high (and fuel costs low, and minimum storage/having to hunt for fuel in a power emergency)--I believe the Magnum inverters are programmable for maximum AC power rating of AC power source (generator, feed from grid). Make sure you get the "right" remote meter (there is a basic and advanced type meter--Not sure if the basic can program all the needed software settings or not, need to adjust charging voltage/float/no equalization voltage for AGM).

    Some other options to think about--The remote battery temperatures sensor option (not sure if RBTS comes with inverter or extra cost option). And a Battery Monitor (especially helpful for AGM which you cannot measure specific gravity because they are sealed). Magnum does have its own battery monitoring system (and other products)--Not sure if it is same better/worse than a stand alone Monitor.

    Otherwise--4kW inverter is pretty good sized--Does he need that much power? And what AH is/will be the battery bank?

    If he ever plans on adding solar, there are various pre-wired "E-Panels" to make things a bit easier/cleaner.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • WxboyWxboy Solar Expert Posts: 70 ✭✭✭✭
    Re: Magnum MS4024PAE vs. MS4448PAE

    The generator is a Honda EU6500is which is a big brother to your EU2000i. He won't be running any 24 volt loads, just 120/240v. Battery bank will be either 400 amp hours or 800 if he buys 2 more batteries and goes with 2 parallel strings but I think he'll start with the 4 100 amp hour batteries since he has the generator to fall back on. I don't anticipate that he will go solar because his house has too many tall trees around it.

    Thanks for the tips on the meters and monitors and sensors, good to know.
  • BB.BB. Super Moderators, Administrators Posts: 32,230 admin
    Re: Magnum MS4024PAE vs. MS4448PAE

    Sounds pretty well balanced... A 400 AH @ 48 volts is good for about a 4kW inverter/charger... 800 AH @ 48 volts would be good for up to an 8kW inverter/charger (and good for 8kW/16kW surge ratings).

    The 48 volt version has a 60 amp battery charger--Which would pull from the genset (maximum rating):
    • 60 amps * 59 volts charging * 1/0.95 power factor * 1/0.85 charger eff = 4,384 VA (good match for a 6.5kW genset)

    And a 60 Amp charger would be good for a rated battery bank of:
    • 60 amps * 1/0.05 rate of charge= 1,200 AH maximum battery bank
    • 60 amps * 1/0.10 rate of charge= 600 AH nominal battery bank
    • 60 amps * 1/0.13 rate of charge= 462 AH maximum "good practices" charging rate
    • 60 amps * 1/0.25 rate of charge= 240 AH maximum "don't exceed unless you have a very good reason" rate of charge

    The above numbers are recommended rules of thumb for Flooded Cell battery banks--AGM batteries have much higher current limits and much lower self discharge--But there is not really much reason for designing a "balanced" Off Grid / Backup up system for AGM only unless it has special needs (UPS systems are designed to drain an AGM battery bank in 15-30 minutes until the computers can be shutdown and/or backup fuel power generators are brought on-line).

    If he ever decides to go with solar--Having a "smaller" battery bank and a (by ratios) "larger" solar array (i.e., 10% to 13% rate of charge) can help keep costs down (smaller battery bank to replace every 3-6 years for AGM) and a smaller array (even a 400 AH 48 volt can take a pretty good sized array):
    • 400 AH * 59 volts charging * 1/0.77 panel+controller derating * 1/0.10 rate of charge = 3,065 Watt array "nominal"

    Tall trees can be a "temporary" situation... Our neighborhood lost many of its trees over the last 50 years--Roads are hard on tree roots and having 200 foot trees around homes on 50-100 foot lots means that cars and homes were being "bisected" every few years when a heavy wind/rain storm rolled through.

    If he has more land--Can he put the array within a several hundred foot radius of the home and get some good sun?

    Also, if he has grid and this is purely for emergency/backup power--He could drop to 5% rate of charge, be a bit conservative about power used during the day, and still have a reliable/solid system.

    Anyway--My 2 cents worth of advice.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Magnum MS4024PAE vs. MS4448PAE
    Wxboy wrote: »
    Battery bank will be either 400 amp hours or 800 if he buys 2 more batteries and goes with 2 parallel strings but I think he'll start with the 4 100 amp hour batteries since he has the generator to fall back on.

    Just a heads up: 4 100 AH 12 volt batteries will give you a 100 AH 48 V battery bank, not a 400 AH 48 V bank.
  • BB.BB. Super Moderators, Administrators Posts: 32,230 admin
    Re: Magnum MS4024PAE vs. MS4448PAE

    Good Catch Mtdoc!

    Note to Wxboy--4 batteries in series for 48 volts, vs 2 in series/2 in parallel, vs 4 in parallel (assuming all 12 volt batteries)--Will all store the same amount of total energy... It is just moving from 24 volts to 48 volts with the same batteries--The voltage rating doubles, the AH rating 1/2's... And the total energy storage is still the same (and the current will be 1/2, allowing smaller wire/longer wire runs because of the higher battery bus voltage).

    Thank you,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Magnum MS4024PAE vs. MS4448PAE

    You might want to read through this about different system Voltages: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power
  • WxboyWxboy Solar Expert Posts: 70 ✭✭✭✭
    Re: Magnum MS4024PAE vs. MS4448PAE

    Actually I was just about to correct the amp hour rating after I read Bill's charge rate section of his post but I see everyone already figured it out. I know how it works but I just wasn't thinking when I typed it since I'm more used to my 12volt system.
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