Need advise on generator to supplement system

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jbad
jbad Registered Users Posts: 7 ✭
in Solar Beginners Corner #1
I have 2 Generac generators APS 6.0 24V DC Air-Cooled Auxiliary Power Custom Units that have been made to Custom Commercial Specifications:
Model: 00847-0
Phase: 6 PHASE UNITS
Volts: 27.2
Watts: 6000
Engine: RPM: 3,600 ONAN PROPANE.
Generator RPM: 3600
Built-In Fuel Tank: 80 GAL. PROPANE
Electronics: TIMERS, WITH EXTENSIVE CONTROLS

I plan on using one of this generators to supplement my system on cloudy days.
My system consists of:
4000 Watt 24VDC 120/240VAC Magnum 4024 system with a Midnite Classic 150 CC
10 230Watt Sharp panels and 8 Trojan L16P-AC 6V 420ah
Battery monitor and surge protectors...

Since this is a 24V generator, I am not quite sure how to hook it up on my system. I would like to be able to power my system and at the same time charge the batteries if possible.
Any information or advise would be greatly appreciated. Thank you in advance...
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    #2
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    Re: Need advise on generator to supplement system

    Unless you can overspeed the alternator (over rev the engine) it doesn't look like you'll get enough power to absorb your batteries. Absorb for 24v batteries is around 29vdc, you're supplying with 27.2. That'll do for bulk charging, with pv finishing off the absorb phase, but what about in the winter when you don't have the required amount of sun available? Then ther's de-rating for altitude if applicable.

    Ralph
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #3
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    Re: Need advise on generator to supplement system

    I assume this thing is putting out 27 volts AC (no rectifier built-in). If so this may be an even bigger problem than what Ralph mentioned above. To get the voltage you need maybe you can find two phases that are opposite and wire them in series to get 54.4. But then you'll need to find a charger than can accept AC and 54.4 volts input, but output for a 24 volt battery.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: Need advise on generator to supplement system

    Actually if it is 27 Volts AC once you put it through a rectifier circuit you would have enough Voltage. About 40 VDC.
    If it already is 27 VDC it will charge the batteries enough to keep them from dying, but it will not reach Absorb as Ralph said.

    Maybe you should just get a cheap 120 VAC gen and run it through the Magnum's PF corrected charging circuit. The Generac unit would probably suck up a lot more fuel than any small unit, and you really don't need more than 2kW for recharging a 4kW system in most cases.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #5
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    Re: Need advise on generator to supplement system

    Alternators are easily able to output upwards of 120 VDC (in the old'en days, you could get a kit to convert your alternator to output 120 VDC for brushed motor power tools and such--as I recall).

    It is the regulator for the alternator that is limiting the charging voltage. There are some vendors that do support programmable alternator regulators. I would wonder if this unit has an adjustable regulator.

    If push came to shove--I would probably "skip" equalization during winter if I did not have a backup AC genset and AC battery charger.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #6
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    Re: Need advise on generator to supplement system
    jbad wrote: »
    Generac generators APS 6.0 24V DC

    Looks like the output IS DC.

    Assume that these were designed to be Telecom BU/Chargers for VRLAs.

    There could be a hack for the regulator.

    AND, the list of future features for the MN Classic is a Boost Mode for the converter. You might kinna to do a Bulk on warm/hot batts as it stands, probably. There may even be s pot or perhaps FW that controls the regulator ... dunno. I DO like the concept of DC charging (external to Inverter/Chargers), altho, DC chargers need to be close to the batts.

    Good Luck, please let us know what you find and of your progress. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #7
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    Re: Need advise on generator to supplement system

    Sure enough, when I searched for that model number I found them all over the place on the net - all listed with DC output. Some went for $325, this link wants several thousand (it has good pics of it which is why I'm posting the link... look in the middle of the left page).

    http://heavyequipment.mylittlesalesman-digital.com/heavyequipment/201110?pg=14#pg14
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • jbad
    jbad Registered Users Posts: 7 ✭
    #8
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    Re: Need advise on generator to supplement system
    techntrek wrote: »
    Sure enough, when I searched for that model number I found them all over the place on the net - all listed with DC output. Some went for $325, this link wants several thousand (it has good pics of it which is why I'm posting the link... look in the middle of the left page).

    http://heavyequipment.mylittlesalesman-digital.com/heavyequipment/201110?pg=14#pg14

    I got these generators at an auction...$225 for the 190hrs and $325 for the 120 hrs.
    I was hoping to use these in the ranch and help out other ranchers in our area that are living off-grid.
    I am about to hook one up but now am a bit confused if I should or not...
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Need advise on generator to supplement system
    jbad wrote: »
    I got these generators at an auction...$225 for the 190hrs and $325 for the 120 hrs.
    I was hoping to use these in the ranch and help out other ranchers in our area that are living off-grid.
    I am about to hook one up but now am a bit confused if I should or not...

    Putting too low a charging Voltage to a system (i.e. 27 VDC instead of 28.8 ) won't hurt it, it just can't fully charge it. It could certainly bring it up from the LVD point of the inverter to an operable Voltage.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #10
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    Re: Need advise on generator to supplement system

    They would work great to get you up to a level where your PV would do the finishing charge. You could also set up 4 PWM Charge Controllers and do a distributive charge @ 12 v + on every two batteries. The issue would be having some kind of a dump load with 230 amps output I would think.

    http://evhelp.com/Distributed_charging_system_generic.htm
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #11
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    Re: Need advise on generator to supplement system
    jbad wrote: »
    I got these generators at an auction...$225 for the 190hrs and $325 for the 120 hrs.

    About the same as this auction: http://www.cyberauctions.com/ViewPastAuction.php?cid=0&bpass=&aid=262&srid=49

    Now that we know they output DC, the "6 phase" part is confusing. Does this thing have 6 separate DC outputs (6 phases rectified)? Or is there one single 27 volt output?
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • jbad
    jbad Registered Users Posts: 7 ✭
    #12
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    Re: Need advise on generator to supplement system
    techntrek wrote: »
    About the same as this auction: http://www.cyberauctions.com/ViewPastAuction.php?cid=0&bpass=&aid=262&srid=49

    Now that we know they output DC, the "6 phase" part is confusing. Does this thing have 6 separate DC outputs (6 phases rectified)? Or is there one single 27 volt output?
    Techntrek,
    Here is a brief description from the pdf manual that I had downloaded...
    The engine runs at a speed of 3600 RPM and drives the alternator at the same speed, producing an AC 6 phase voltage. This voltage is taken directly from the stator windings and into two independent 3-phase bridge rectifiers. The DC output from the rectifier is then fed into an inductive-capacitive filter assembly designed to reduce the AC ripple content of the DC output. The output of the filter is then fed directly to the generator output terminals.
    I can try to upload the file but it is about 18mb.
    Attachment not found. Attachment not found.


    Cariboocoot, Thank you for your clarification!
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #13
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    Re: Need advise on generator to supplement system

    So then there is one output (one + and one - )? Hard to tell from the pics.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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