replacing batteries

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castilloj
castilloj Solar Expert Posts: 208 ✭
in Off Grid Solar & Battery Systems #1
Hi guys, i currently use a 24 v outback inverter, using 4 rolls s600 batteries that are pretty bad. I use 3 amps ac from 11 pm to 8 am.
I was wondering if i could use 4 trojans t-105 batteries till my new trojan l16h batteries arrive. I also have a 48 v outback inverter that I'm waiting to setup until i get my 8 L16 batteries. I also run a 11 kw diesel generator in the Morning from 8 am till noon then from 5 pm till 11 pm.
would this work temporarily?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: replacing batteries

    Well 3 Amps @ 120 VAC is 360 Watts, and 11:00 P.M. to 8:00 A.M. is 9 hours so that's 3,240 Watt hours AC.
    In terms of Amp hours on a 24 VDC system it's about 150. A T105 is 225 Amp hours. You'd be using around 66% of the batteries' capacity, and kill them in short order. If their longevity isn't an issue, go ahead. But I'd look for something more that could be turned off first. About 1200 Watt hours worth.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #3
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    Re: replacing batteries

    3 amps of AC--I am assuming 230 VAC 50 Hz... So, the "nominal" ( C/8 ) and maximum surge (C/2.5) rated 24 volt bank @ 225 Amp*Hours would estimate to be:
    • 24 volts * 225 AH * 1/8 hour rating * 0.85 inverter efficiency = 574 watts of AC from inverter (max recommended "nominal")
    • 24 volts * 225 AH * 1/2.5 hour rating * 0.85 inverter efficiency = 1,836 watts of AC from inverter (max recommend surge power--starting pump, etc.)

    You are current using an estimated:
    • 3 amps * 230 VAC = 690 watts

    So--it probably would work, but you are cutting it pretty close (in my humble opinion) as an average load (you may have battery cutoff voltage alarm with inverter, discharging so "fast", reduces battery apparent capacity), and it will take a fair amount of recharging time to reach 100% state of charge (generator/solar/etc.).

    For a T105 battery at C/5 rate, you are looking at 185 AH rated capacity. Assuming you discharge to 20% state of charge (any lower, you probably will kill the battery bank):
    • 185 AH * 24 volt * 0.85 inverter efficiency * 0.80 max discharge * 1/(3 amps * 230 VAC) = 4.4 hours of operation at 3 amp / 230 VAC load

    Does not look to meet your requirements as I understand your needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Volvo Farmer
    Volvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    #4
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    Re: replacing batteries

    Not going back to Surrertte huh? ;)

    Seems like it would work, though you'll be cycling the batteries at around 50% capacity overnight.

    P.S. I disagree with BB that you will kill deep cycle batteries cycling them more than 20%, especially temporarily like you are planning.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #5
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    Re: replacing batteries

    Except I typed to 20% State of Charge (i.e., 80% cycling)... The problem is that if you have one "weak" cell, they can be +/-10% between high and low cell AH capacity... So, as you approach 20% state of charge, it is possible for a "weak" cell to actually go to zero and then -2.x volts and begin to "reverse" charge.

    For most rechargeable battery chemistries, "reverse" bias or reverse charging pretty much will kill the cell for future use.

    Voltage wise, you are looking at ~11.5 volts for a "near dead battery" (~23 volts for 24 volt bank), and 10.5 volt (21 volts) is a dead battery with the risk of "killing" a cell.

    Again, this is a "risk"--If the cells are well balanced in capacity, you can go lower than 20% state of charge--But I would not "build a system" around a 100% discharge / 0% state of charge assumption for the battery bank usage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
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    Re: replacing batteries

    Well if it's 230 VAC @ 3 Amps it's about twice the Amp hours I calculated originally:

    230 VAC * 3 Amps = 690 Watts * 9 hours = 6210 Watt hours AC, about 6900 Watt hours DC / 24 Volts = 287.5 Amp hours.
    Or the 225 Amp hour T105's go completely dead before you get through the first night. And that doesn't include the inverter sucking up 20 Watts per hour on its own.
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #7
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    Re: replacing batteries

    Would this work better if i was using my 48 v inverter with 8 batteries , or do i end up in the same problem?
    With my surette batteries i pretty much killed them by undercharging per surrete. So thats why i decided to upgrade my system to a 48 v system with trojan L16h 420Ah (20Hr)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
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    Re: replacing batteries
    castilloj wrote: »
    Would this work better if i was using my 48 v inverter with 8 batteries , or do i end up in the same problem?
    With my surette batteries i pretty much killed them by undercharging per surrete. So thats why i decided to upgrade my system to a 48 v system with trojan L16h 420Ah (20Hr)

    24 Volts @ 225 Amp hours is 5400 Watt hours total. 48 Volts @ 225 Amp hours is 10,800 Watt hours total. More batteries, whether is series or parallel, means more total power.

    The 420 Amp hours @ 48 Volts would be 20,160 Watt hours total. As always, at a 50% DOD limit only half of these totals is available for use.

    If you want to try the T105's on the 24 Volt system for the nightly load, program the Low Voltage Disconnect on the Outback to 24 Volts; it will shut down before dragging the batteries below 50%. Another hint is to run it in Search mode, if the loads are not constant. Set the cycles up to 120 and it will look for a load every two seconds.
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  • SolaRevolution
    SolaRevolution Solar Expert Posts: 410 ✭✭
    #9
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    Re: replacing batteries
    castilloj wrote: »
    With my surette batteries i pretty much killed them by undercharging per surrete...

    ...I also run a 11 kw diesel generator in the Morning from 8 am till noon then from 5 pm till 11 pm.

    ???A little forensic inquiry;

    The S600s have only been available for about 2 years.
    How did you manage to undercharge them? Was your absorbtion time too short? Was your charging voltage too low? Did you get specific gravity readings on all cells?

    Thanks,

    -Alex
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #10
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    Re: replacing batteries
    SolaRevolution wrote: »
    ???A little forensic inquiry;

    The S600s have only been available for about 2 years.
    How did you manage to undercharge them? Was your absorbtion time too short? Was your charging voltage too low? Did you get specific gravity readings on all cells?

    Thanks,

    -Alex
    I'm also interested in this question. Haven't been hearing much negative, or otherwise lately on Surrette.
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #11
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    Re: replacing batteries

    This is what i first asked Surette*********Hello Serge , my name is Jose Castillo . I am a missionary In Haiti.
    I have 8 rolls s600 batteries on a 24v system and i was wondering what the voltage should be for them to be fully charged? Also the Low battery Cutout Setpoint is 21v. Is that too low or could i go lower? My system shuts down every morning about 6 am and i turn off the generator at 11 pm.
    Thank you very much,

    ****Response-I have attached a copy of our battery user manual. in it you will find all our recommend charger settings for your batteries.

    21 volts for your low voltage cutout is very low; this is 100% discharged. You should be closer to 23-24 volts.

    *****What i asked: Sorry I finally realized what sg means . Anyways I'm not sure what the sg is , but I was wondering what my charge rate should be. Right now my charger limit on my outback inverter is 14 amps, absorb setpoint is at 29.0 vdc
    Absorb time limit 4.5 hrs
    Float setpoint 26.4 vdc
    Float time period 1.1 hrs
    Refloat setpoint 25.0 vdc
    Equalize setpoint 31 vdc
    Equalize time period 3.2 hrs
    Low battery cut- in setpoint 25 vdc
    Low battery cut out is now 23 vdc

    Response: You would need to have around 25-28 amps AC to properly charge 2 strings of your batteries.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #12
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    Re: replacing batteries
    castilloj wrote: »
    Response: You would need to have around 25-28 amps AC to properly charge 2 strings of your batteries.

    They are probably assuming that your AC power is at 115 volts. At 230 volts you would need half of their recommended 25-28 amps. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • SolaRevolution
    SolaRevolution Solar Expert Posts: 410 ✭✭
    #13
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    Re: replacing batteries
    castilloj wrote: »
    Right now my charger limit on my outback inverter is 14 amps, ...

    ...Response: You would need to have around 25-28 amps AC to properly charge 2 strings of your batteries.

    Wait, Is your Outback 230 vac output?

    If so 14 amps would be 3220 watts. That's 15% of rated battery capacity. (2 strings of 450ah @ 24v= 21600 watt/hrs)
    If your load is 3 amps at 230 vac for 9 hrs that's 6210 watt/hrs. (29% of battery capacity)

    This should not be a problem for the S600s. Did Serge know you have a 230 vac system? If your system is 120vac you're only drawing down 15% of battery capacity overnight and you are not wildly low on your charging current (7.7%) Of course you should figure some loss from charger inefficiency, but still for "premium" batteries to die in two years with these specs...?:confused: Are they so dead that you would be better off with (4) T-105s while you wait for the Trojans?

    I think you will be happy when you get your ( 8 ) L16-REBs.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #14
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    Re: replacing batteries

    One more thought... You are in Haiti. Its warm down there. What is the ambient temperature of your batteries? Warm/hot batteries cannot be expected to have a normal lifespan. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • SandyP
    SandyP Solar Expert Posts: 65 ✭✭
    #15
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    Re: replacing batteries

    Voltage and Frequency
    Electricity in Haiti is 110 Volts, alternating at 60 cycles per second.
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #16
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    Re: replacing batteries

    The t105 here are 250ah at 100
    Or 225 ah at 20hr
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
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    Re: replacing batteries

    S600's are 450 Amp hours. If you have two parallel strings that is 900 Amp hours. That's a lot of battery (21 kW hours worth).
    They should have 90 Amps DC charging current, which the Outback is not capable of (its charger limit is 80 Amps DC).
    On AC, that's 2160+ Watts, or 19 to 20 Amps on 110 VAC 9 to 10 Amps on 230 VAC. Where they came up with 28-30 AAC I don't know.

    And vtMaps is absolutely right about the higher temperature environment: the batteries will not have the same power capacity there and will charge at a lower Voltage. Temperature compensation is a must (RTS attached to the inverter/charger). Often battery companies put higher SG electrolyte in "tropical" batteries to improve their power - at the further expense of lifespan.
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #18
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    Re: replacing batteries

    Would it work if I got the Trojan j185p-ac
    12v 205 ah?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #19
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    Re: replacing batteries
    castilloj wrote: »
    Would it work if I got the Trojan j185p-ac
    12v 205 ah?

    If you got four of them and put them together as a 410 Amp hour 24 Volt bank? You'd have up to 4800 Watt hours DC to work with then (50% DOD). That should handle your 3240 Watt hour load, at least for a while.

    I take it you're trying to stay running with batteries available locally while waiting for the L16's to come in? Having to buy batteries twice is a whole lot of "no fun".
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #20
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    Re: replacing batteries
    Cariboocoot wrote: »
    If you want to try the T105's on the 24 Volt system for the nightly load, program the Low Voltage Disconnect on the Outback to 24 Volts; it will shut down before dragging the batteries below 50%. Another hint is to run it in Search mode, if the loads are not constant. Set the cycles up to 120 and it will look for a load every two seconds.

    I ended purchasing the T105 batteries. what settings should i change other than setting up the low voltage disconnect to 24v? also how much time do you think they would give me?
    if i run 3 amps AAC?
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #21
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    Re: replacing batteries

    The problem with the 24v LBCO is that depending on you loads you'll get a big dip and recovery on the voltage and the T105's won't have as much reserve power and your inverter may keep cutting out.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #22
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    Re: replacing batteries

    Think of it this way: you have up to 50% of the battery bank's capacity. T105's are 225 Amp hours, so for all practical purposes you have 100 Amp hours @ 24 VDC or 2400 Watt hours. Your intended load at 3240 Watt hours means the batteries won't make it through the night. The 360 Watts of load will be able to run around six, maybe seven hours before shutdown occurs.

    For what it's worth, program the inverter to turn off at 24 VDC (it will go slightly lower than this). Set it to "Search" mode if the loads are not constant. Put the cycles up to 120 as I mentioned so it only looks for a load every 2 seconds. The other two Search settings are for load (usually 6) that will turn the inverter on and the number of cycles it looks for the load (usually 8 ).

    The charge settings for the T105's should be:
    Absorb Voltage 28.8
    Absorb time 2 to 3 hours (Outback's inverter/charger does not handle this well; you may need to extend the Absorb time due to the extra time it will take to Bulk charge from drawing the batteries so low).
    Float Voltage 27.6
    The peak charge current should be about 20 to 25 Amps, which is 4 to 5 Amps AC on the inverter's charge menu.
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #23
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    Re: replacing batteries
    Cariboocoot wrote: »
    I take it you're trying to stay running with batteries available locally while waiting for the L16's to come in? Having to buy batteries twice is a whole lot of "no fun".
    Yeah Thats what I'm trying to do , i just don't want to kill the T105 before the L16 Clear customs. Do you think the outback mate is very accurate when it says what the inverter current is? I have 4 Box fans that i use at night aswell a internet modem and router. i try not to use ceiling fan because i think they really suck up power.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #24
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    Re: replacing batteries
    castilloj wrote: »
    I have 4 Box fans that i use at night aswell a internet modem and router. i try not to use ceiling fan because i think they really suck up power.
    A well made ceiling fan will move more air for far less power than a comparable box fan. The faster the blades move the worse the frictional losses. Without a watt meter, it is hard to say for sure though.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #25
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    Re: replacing batteries
    Blackcherry04 wrote: »
    The problem with the 24v LBCO is that depending on you loads you'll get a big dip and recovery on the voltage and the T105's won't have as much reserve power and your inverter may keep cutting out.

    His total loads are 360 Watts and there don't appear to be any high-surge items on the list.
    BTW the Outback requires the Voltage to drop below LVD for a certain period of time before it shuts down. This to handle just those instances you mention. :D
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #26
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    Re: replacing batteries
    castilloj wrote: »
    Yeah Thats what I'm trying to do , i just don't want to kill the T105 before the L16 Clear customs. Do you think the outback mate is very accurate when it says what the inverter current is? I have 4 Box fans that i use at night aswell a internet modem and router. i try not to use ceiling fan because i think they really suck up power.

    What inetdog says is true: sometimes the ceiling fan will use less. But it's hard to measure a ceiling fan with a Kill-A-Watt as they are (usually) hardwired. It's a really good idea to get accurate power readings on everything you use and not rely on the manufacturer's data.

    The Outback's current reading is slightly inaccurate in that it rounds things up/down to the nearest 1 Amp. Otherwise it is accurate enough in respect to the rest of the system's operation to be relevant. I'm thinking about wiring mine's output through a box so I can check all the power going out with the meter and compare that to the Outback's readings. It could be interesting.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #27
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    Re: replacing batteries
    castilloj wrote: »
    Yeah Thats what I'm trying to do , i just don't want to kill the T105 before the L16 Clear customs. Do you think the outback mate is very accurate when it says what the inverter current is? I have 4 Box fans that i use at night aswell a internet modem and router. i try not to use ceiling fan because i think they really suck up power.
    Hard to know how accurate any of them are. Right now my Xantrex SCP is reading 26.8 and the actual battery bank voltage is 26.4. I feel the bank voltage is correct ( tested with 4-5 different digital meters ). The question is, if the inverter is off .4 it makes a huge difference in how it handles everything and how I program the settings. If you say 24 Volts, is it 24.4 volts or 23.6 volts in real terms. Knowing your system is important in terms of any setting you make. Your wiring has a big effect and so do the size of your loads.

    I have a Magnum and it's about the same as the Xantrex as far as the voltage it reads.

    Your loads seem consistent, that helps. If you were running a A/C or a Microwave Oven and dropped a huge AMP draw, you'd have a harder time.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #28
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    Re: replacing batteries
    Cariboocoot wrote: »
    His total loads are 360 Watts and there don't appear to be any high-surge items on the list.
    BTW the Outback requires the Voltage to drop below LVD for a certain period of time before it shuts down. This to handle just those instances you mention. :D
    I saw that he had posted the loads after I had made the post. Would a refrigerator going into defrost cycle cause it to drop out ?? Mine does, maybe I have the wrong Inverter or the wrong setting.

    Outback Low Battery Cut-Out (LBCO): This feature prevents the inverter from draining the batteries completely. It
    will stop functioning and give a Low Battery Voltage error when the DC voltage drops below a specified
    level for 5 minutes. This is one of the Error messages described on page 36. This function is intended to
    protect both the batteries and the inverter’s output. (Continuing
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #29
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    Re: replacing batteries

    My 'frige hits 500 Watts in defrost and doesn't phase the inverter even when it's at 24 Volts. The water pump on the other hand ... You don't want that starting when you're on your last Amp hours. :D

    When the Voltage comes back up, btw, it restarts. Outback inverters are great. Complicated, but great.

    The OP is running 360 Watts over 9 hours. Lots of Watt hours there.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #30
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    Re: replacing batteries
    Cariboocoot wrote: »
    My 'frige hits 500 Watts in defrost and doesn't phase the inverter even when it's at 24 Volts. The water pump on the other hand ... You don't want that starting when you're on your last Amp hours. :D

    When the Voltage comes back up, btw, it restarts. Outback inverters are great. Complicated, but great.

    The OP is running 360 Watts over 9 hours. Lots of Watt hours there.
    Outback Sounds like a winner. 500 watts doesn't sound like much unless your already pulling a 1000 + . I found my Refrigerator had a 8 hour defrost timer and swapped it out for a 12 hour timer, that cut out a bunch of necessary waste. I really think it could go 24 hrs, I thought about getting rid of the stock timer and add one.
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  • castilloj
    castilloj Solar Expert Posts: 208 ✭
    #31
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    Re: replacing batteries
    Cariboocoot wrote: »

    The charge settings for the T105's should be:
    Absorb Voltage 28.8
    Absorb time 2 to 3 hours (Outback's inverter/charger does not handle this well; you may need to extend the Absorb time due to the extra time it will take to Bulk charge from drawing the batteries so low).
    Float Voltage 27.6
    The peak charge current should be about 20 to 25 Amps, which is 4 to 5 Amps AC on the inverter's charge menu.
    What should refloat set point be?
    Also equalize set point and float time period?
    Also is there anything I need to change with m mppt60?
    Or use their normal setting using the dip switches?

    Thanks
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