Generator battery charging

lc0338lc0338 Posts: 56Registered Users ✭✭
Sorry if this is not in the correct category but I upgraded my living quarter horse trailer. The trailer I upgraded to is used and the previous owner had installed an Onan 3600 lp generator in one of the storage areas below a manger and placed the battery in another manager. I was not connecting the dots (thought the battery was being charged via the controller) and discovered the battery had gone bad after several hard freezes. Since the generator requires a battery be connected to both start and run, I was looking for an alternate plan so I don't have to manually recharge the battery. I was thinking of the options below:

1) Eliminate the generator battery and wires from the house batteries (2ea 12 volt). The house batteries are located about 25 - 30 feet from the generator so any help on wire size would be appreciated if there is no concern about the distance.

2) Keep the generator battery and run wires to the onboard converter. About half the distance of option 1 in distance from the converter to the generator.

I was thinking option 1 mainly because it would reduce one battery in the system. The battery compartment currently has room enough for 2ea batteries.

If there is a better option please let me know. Which option is best? and what size wire would be best?

Thanks


Comments

  • mike95490mike95490 Posts: 7,713Solar Expert ✭✭✭✭
    2 batteries -  you wan to use a pair of 6V golf cart batteries wired in series, to give you 12V @ 200Ah.  Don't use two 12V batteries

    Be very wary of a generator near living areas, Carbon Monoxide poisoning has killed many folks running generators. Trailer mangers and storage areas are never airtight, I'd put the generator in a doghouse 20 feet away and run 120VAC to the converter.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • lc0338lc0338 Posts: 56Registered Users ✭✭
    mike95490 said:
    2 batteries -  you wan to use a pair of 6V golf cart batteries wired in series, to give you 12V @ 200Ah.  Don't use two 12V batteries

    Be very wary of a generator near living areas, Carbon Monoxide poisoning has killed many folks running generators. Trailer mangers and storage areas are never airtight, I'd put the generator in a doghouse 20 feet away and run 120VAC to the converter.
    Generators are pretty much main steam equipment in RV and toy haulers and it is installed correctly with an air intake vent and exhaust pipe that vents out from under the trailer plus the generator is at the back of the trailer and living quarters are at the front of the trailer. The generator is not ran that often due to my solar generator keeps the main house batteries in good shape when boondocking and one of the reason for my question/thought of eliminating the generator battery.
    6 volt golf cart batteries have venting issues as well. I like AGM 6 volt batteries and is what I use for my solar generator, however this trailer, as I mentioned, I upgraded to already had 12 volt batteries installed so not going to throw away good batteries. They supply adequate power for me at this time when backed up with my solar generator. When I need to upgrade i may install 6 volt agms. Also appreciate your concern for my safety and also your pro 6 volt golf cart batteries. Hope I can get some discussion of my questions of option 1 or 2. Thanks
  • EstragonEstragon Posts: 2,456Registered Users ✭✭✭✭
    Another option might be to use a small lithium booster pack battery to start the generator. They hold their charge for a long time without needing to be trickle charged, and can be recharged easily by plugging into a regular AC wall plug. As a bonus, it could be used to boost dead vehicles etc if need be.

    https://www.amazon.com/gp/aw/d/B073FD3NKW/ref=mp_s_a_1_6?ie=UTF8&qid=1516897478&sr=8-6&pi=AC_SX236_SY340_FMwebp_QL65&keywords=lithium+booster+pack&dpPl=1&dpID=41h22g1WhOL&ref=plSrch

    Option 1 would need fairly heavy cable to carry the high current for starting, and deep-cycle house batteries aren't particularly good at cranking applications. Presumably, the house bank would also be at a low state of charge (which is why you're starting the genny in the first place), which makes them even worse at starting. If the house bank wasn't able to start the genny, you're left with a dead house bank and nothing else (maybe jumper cables from a tow vehicle?).

    Option 2. Would be better, as long as the controller can be set up to properly charge both the house and starting batteries. Current from the controller would be much lower, allowing for smaller wire to the starting battery.
    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
  • lc0338lc0338 Posts: 56Registered Users ✭✭
    Estragon said:
    Another option might be to use a small lithium booster pack battery to start the generator. They hold their charge for a long time without needing to be trickle charged, and can be recharged easily by plugging into a regular AC wall plug. As a bonus, it could be used to boost dead vehicles etc if need be.

    Option 1 would need fairly heavy cable to carry the high current for starting, and deep-cycle house batteries aren't particularly good at cranking applications. Presumably, the house bank would also be at a low state of charge (which is why you're starting the genny in the first place), which makes them even worse at starting. If the house bank wasn't able to start the genny, you're left with a dead house bank and nothing else (maybe jumper cables from a tow vehicle?).

    That's a good point about the house batteries being low and not being able to start the genny. I carry an inflatable boat when I'm near water and want a break from horse back riding. I carry an agm battery to power the trolling motor and that is what I used the other day to start the genny to give it some exercise. Also learned at that time I need to keep the jumper cables hooked up while it ran. I may just continue doing that but when the genny has a remote start capability it seems nice to be able to sit in the living quarters when a rain storm is happening and being able to start the genny from my couch :)


    Option 2. Would be better, as long as the controller can be set up to properly charge both the house and starting batteries. Current from the controller would be much lower, allowing for smaller wire to the starting battery.

    I haven't investigated if my controller has the capability or not. Even though it is closer (distance wise) from the controller to the generator, wiring becomes more difficult since the controller is in the living area (inside trailer). Thanks for the feedback.
  • BB.BB. Posts: 27,578Super Moderators admin
    Another common solution for genset batteries (many emergency backup gensets use AC mains for charging--No charging when off grid) is to put a small (5-10-20 watt depending on size of genset battery) solar panel + small charge controller to float the genset battery on its own.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lc0338lc0338 Posts: 56Registered Users ✭✭
    BB. said:
    Another common solution for genset batteries (many emergency backup gensets use AC mains for charging--No charging when off grid) is to put a small (5-10-20 watt depending on size of genset battery) solar panel + small charge controller to float the genset battery on its own.

    -Bill
    What is your opinion of one like this:

    Sunforce 50022 5-Watt Solar Battery Trickle Charger

    https://www.amazon.com/Sunforce-50022-Battery-Trickle-Charger/dp/B0006JO0TC

    Is there another better one out there?
     
  • BB.BB. Posts: 27,578Super Moderators admin
    edited January 26 #8
    How many ah is your (presumably) 12 volt genset battery?

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lc0338lc0338 Posts: 56Registered Users ✭✭
    BB. said:
    How many ah is your (presumably) 12 volt genset battery?

    Bill
    I have this Optima battery I use for the inflatable boat trolling motor. I used it to start the generator the other day. I could install it as the genny battery with quick disconnets and use it for the tolling motor when needed.
    https://www.amazon.com/gp/product/B00075OSCO/ref=oh_aui_detailpage_o07_s02?ie=UTF8&psc=1
  • BB.BB. Posts: 27,578Super Moderators admin
    More or less:
    • 1% rate of charge--Maximum "no charge controller" rate of charge (will float a fully charge battery for many months)
    • 2%+ rate of charge--Need charge controller to prevent over charging (should float a battery indefinitely, no other loads)
    • 5% rate of charge--Cycling battery on weekends during summer (will recharge battery in light usage)
    • 10% rate of charge--Daily cycling of battery bank (full time off grid)
    • 13% rate of charge--Typical "maximum cost effective" solar array
    • 20-25% rate of charge--Typical maximum recommended rate of charge--highly suggest charge controller with Remote Battery Temperature Sensor
    For AGM batteries (like yours), I would always suggest that you use a battery charger with your solar panels. Flooded cell batteries can be overcharged a bit, and you add water every month or two. AGM cannot have water added (sealed cells).

    Your battery is a 55 AH rated battery:
    • 55 amps * 0.01 rate of charge = 0.55 amp solar panel minimum (0.55 amps Imp * 17.5 volt panel Vmp = 9.6 Watt panel)
    • 55a * 0.02 charge = 1.1 amps (1.1 amps * 17.5 volts = 19 watt panel)
    • etc.

    The solar panel you linked to does not list Imp and Vmp--Comments say Vmp/Voc~14.0 volts. This type of panel has been used for floating 12 volt panels and probably would be OK for floating your AGM battery (assuming battery is fully charged before being installed on genset).

    I personally do not like Amorphous solar panels--I am not sure that they will last more than 2-5 years in sun. And the voltage (for that panel) appears to be too low to use a battery charger (need ~17.5 volts minimum for use with battery charger).

    Crystalline panels (mono and poly crystalline) with glass cover do last longer in most applications (glass is easy to shatter--It is usually tempered glass--but a golf ball sized rock/etc. can shatter and ruin the panel).

    If you want to try the 5 watt panel, and check every 1-4 weeks the battery voltage (should be ~13.4+ volts under sun, >~12.6 volts at night)--If the battery stays up--then why not use it (simple, cheap). If resting battery falls below ~12.4 volts, that panel is not enough charging to keep battery floating (panel needs to be in full sun, no shading for most of day). AGM batteries have little self discharge and a "small" wattage panel should keep up with self discharge (all thing being equal).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lc0338lc0338 Posts: 56Registered Users ✭✭
    Thanks very much for taking the time to provide such a detailed answer. Yes, I have found the optima agm battery to be excellent in holding charge in storage. I have a Schumacher SC-10030A SpeedCharge 2/12-30/100 Amp Automatic Charger and Maintainer that I check the battery health from time to time. Also agree about amorphous solar panels. I used 2ea 270 watt monocrystaline solar world brand panels for my solar generator. On the genset battery charge, I was mainly looking for something very portable and cheap to start. :) 
  • mcgivormcgivor Posts: 1,903Solar Expert ✭✭✭✭
    What I use to maintain a charge on my escavator and tractor , which for the most part sit around waiting for a job to do on the farm, is use a 20W panel and a cheap 10A PWM charge controller, something like this  https://www.amazon.com/ECO-WORTHY-Volt-Solar-Charging-Polycrystalline/dp/B015CALI9E/ref=sr_1_4?ie=UTF8&qid=1516961763&sr=8-4&keywords=20W+12v+solar+panel+++charge+controller
    not exactly what I have, just an example, bought separately the cost was around  $35. Given time it can actually charge a discharged battery, naturally if recharging is a priority, for use on a trolling motor as described, a larger panel would reduce charging time, having a controller is cheap insurance.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • lc0338lc0338 Posts: 56Registered Users ✭✭
    Thanks for your input. With that size (20a) controller you could add a few more panels to the mix. :)
  • BB.BB. Posts: 27,578Super Moderators admin
    Depends on the controller (see the manual), but roughly:
    • 20 amp controller * 17.5 volt Vmp-array nominal = 350 Watt array (for a 12 volt battery bank)

    Note--The details do matter... If you have 17.5 volt panel you can add them in parallel to a PWM (lower cost) charge controller.

    If you have larger format panels, they are typically Vmp~30-50 volts, and should have a MPPT (maximum power point tracking) type charge controller (more expensive) that can efficiently down convert from "high voltage" array to low(er) voltage battery bank for charging/running your DC bus loads.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Posts: 1,903Solar Expert ✭✭✭✭
    You could, depending on the current the controller is able to process, bare in mind that was only a random example  if additional power is required the capacity of the controller must increase correspondingly, it's always best to calculate what's required and allow for a safety margin, it's generally not good practice to run equipment to its maximum threshold, so if 40A is required, use a controller capable of 50A or greater, for instance.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

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