Off the grid Island camp - 12v vs. 120v

2»

Comments

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Off the grid Island camp - 12v vs. 120v
    Right now I'm using a Vector 109d 3 stage smart charger and it appears to handle everything well.

    Would a Xantrex be a fast charger? Is a faster charger good for a system?


    From the recomended reading,,from NWAS: Pay note to the final paragraph. Also battery chargers should be sized according to the battery bank size. If you have 335 amh of capacity you should be looking for a charger in the 40 amp range. (Somewhere on this site BB has a factor, and I think it is ~20% of battery capacity but don't quote me.)

    Battery Charging

    Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.

    Bulk Charge - The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.

    Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.

    Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called "pulse width" because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.

    Chargers: Most garage and consumer (automotive) type battery chargers are bulk charge only, and have little (if any) voltage regulation. They are fine for a quick boost to low batteries, but not to leave on for long periods. Among the regulated chargers, there are the voltage regulated ones, such as Iota Engineering and Todd, which keep a constant regulated voltage on the batteries. If these are set to the correct voltages for your batteries, they will keep the batteries charged without damage. These are sometimes called "taper charge" - as if that is a selling point. What taper charge really means is that as the battery gets charged up, the voltage goes up, so the amps out of the charger goes down. They charge OK, but a charger rated at 20 amps may only be supplying 5 amps when the batteries are 80% charged. To get around this, Statpower (and maybe others?) have come out with "smart", or multi-stage chargers. These use a variable voltage to keep the charging amps much more constant for faster charging.
  • BB.BB. Super Moderators, Administrators Posts: 32,009 admin
    Re: Off the grid Island camp - 12v vs. 120v
    T...he let me use his automatic 4/10/20/40A charger. Chatted with a local battery person and he recommended charging with 10A as it is slower but more consistent.
    ...
    Get a radio with lowest wattage requirements possible.
    My 95W laptop has chewed up my battery bank power faster than I expected and has given me a new perspective on what I need to do.

    Q's:
    When I add panels could the controller handle battery monitoring or do I need a separate battery monitor?
    When running the generator do I need a transfer switch to put power directly into the camp and bypass the battery bank or can I run the generator to charge batteries with the inverter powering the camp at the same time?

    Assuming you have 670 Amp*Hour bank and your recommended charging rate is 5%-13% (generic recommendations--some battery types support higher/lower numbers)... Pick 10% and that would be ~67 Amps.

    And generally, this is what you would want to use on a generator--assuming your generator can support the battery charger at that setting. You want the generator to run efficiently (higher loads, 25-50% or larger, rather than lower loads; less than 25% wastes fuel) and for shorter times (less noise, smoke, wear and tear, etc.).

    Also, you will want to use an accurate DVM to check the charging voltage... Many chargers are intended for automotive car batteries and do not support the higher voltages needed to properly charge and equalize deep cycle storage batteries. Read through Wind-Sun's battery FAQ for more information.

    When shopping for AC powered equipment--get a Kill-A-Watt meter and bring it to the store with you--name plate ratings are not intended to reflect the AVERAGE POWER consumption of appliances.

    Radios and other electronics... Check out AC/Battery powered type devices... A portable boom box with an AC option will probably use less power than almost anything out there intended for home use.

    Laptop--you should be able to find a 20-30 watt unit pretty easily. And set your AC options to power saving levels--Unless you are doing heavy graphics, video editing, etc... Obviously, leave everything else turned off (with a power strip) like printers, unused cell phone chargers, etc. to also save energy.

    Regarding the charge controller doing the battery monitoring--The answer is almost always no... The solar charge controller only knows about current flow from the solar panels to the battery bus--it is not able to measure the current used by your loads (or even charging the battery).

    A battery monitor measures ALL CURRENT going "through" the battery. It "totalizes" the current flow, both in and out of the battery over time.

    You can put a simple amp meter in the (typically) negative battery bank lead--but that only gives you an instantaneous reading. It is sort of like trying to figure out how far you have driven by only watching the speedometer... It is much better to use the odometer to keep track of mileage driven.

    Regarding charging a battery with the inverter load vs charging the battery and supplying AC load directly to the cabin wiring (bypassing inverter)--Yes, either will work--but I would probably recommend bypassing the inverter and charging the battery without load.... You have better control of charging current and fewer losses (AC to DC to AC vs AC out of generator)... Also, this is a good time to run heavy loads (coffee maker, vacuum cleaner, washer/drier, well pump, etc.).

    The one disadvantage to switching from inverter to generator AC is if you have a desktop computer or other electronic devices that may "crash" on switching power--so may be an issue for "sensitive" loads

    The "normal" generator process (assuming you need a generator boost because of loads or weather) is to start it up in the morning and bulk charge your battery to 80-95% capacity (~1 hour for every 10% capacity recharge if using C/10 as charge current)--and run any heavy loads--then shut down the generator and use the solar panels to finish up charging the battery and equalization (if needed) because it takes longer to finish charge at lower current the last 5-10% of the battery capacity.

    Eventually, you will want to get a "real" Outback (or equivalent) pure sine inverter that includes a battery charger and automatic internal AC transfer switch. Behaves like a giant UPS (Uninterruptable Power Supply).
    OOPS! Forgot the *2 for /335. So would this double my per hour amps?

    Assuming you have 4x 6 volt batteries, each rated at 335 A*H (20 hour rate) wired series/parallel for 12 volt battery bank. Series connections add voltage and parallel connections add Amps (or Amp*Hours in this case).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,009 admin
    Re: Off the grid Island camp - 12v vs. 120v

    And to add to what Icarus/Tony has said about battery chargers...

    Get a good one--do not rely on a automotive charger. Wind-Sun's battery charger page is here.

    Also, because you are on a generator set--there is something that is really handy to have in a battery charger (assuming you have a smallish gasoline powered generator vs a large diesel set) is "Power Factor Correction"...

    Basically, the typical (old fashion) battery chargers are not very nice loads... They have very high peak currents (just at the AC voltage Peak)--this can overload a generator cause problems with transformers/generator windings.

    Typically, you would see this as 700 watt "charger load" seeming to overload a 2kW generator.

    A PFC charger (also applies to computer power supplies and other electronics) instead looks like a "pure resistive" load to the generator (no high peak currents only at the crest of the AC voltage wave form).

    So--if you are using a small generator (which I recommend, because lightly loaded large generators really waste fuel), then you will have to look closely for a PFC battery charger... Some vendors (like Xantrex) list this for some of their products, and other vendors appear that they should have PFC--but it is not in their specifications.
    • 12 volt models available in 30A & 50A (XC3012 & XC5012)
    • 24 volt models available in 15A & 25A (XC1524 & XC2524)*
    • Microprocessor-controlled, multi-stage charging algorithms
    • Three independently controlled output banks accommodate different battery chemistries and states of charge simultaneously
    • Settings for flooded, gel, AGM, lead-calcium or custom battery types
    • Auto-ranging universal input voltage (100-260 VAC, 47-63Hz) is also compatible with generator or other low quality power sources
    • Independent temperature compensated charging on each of the three output banks
    • Power Factor Corrected for efficient charging
    • Battery equalization feature
    • Invertible and detachable digital display
    • Ability to charge ‘dead’ batteries (< 6V)
    • Includes one battery temperature sensor; additional battery temperature sensors available (part #808-0232-01)
    • Optional intelligent shunt available (part #808-8020-00) to measure amp-hours consumed

    Notice that equipment with "Auto-ranging universal input voltage (100-260 VAC, 47-63Hz)" in their specifications most of the time will also have power factor correction.

    And make sure you get a charger with a remote battery temperature sensor too...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • shortfatguyshortfatguy Solar Expert Posts: 42
    Re: Off the grid Island camp - 12v vs. 120v

    YIKES! You guys type faster then my brain can handle. I need some time to digest.

    Cheers
  • mike95490mike95490 Solar Expert Posts: 9,361 ✭✭✭✭✭
    Re: Off the grid Island camp - 12v vs. 120v
    Right now I'm using a Vector 109d 3 stage smart charger and it appears to handle everything well.

    Would a Xantrex be a fast charger? Is a faster charger good for a system?

    The Vector is a decent charger. Use it as long as you have it on loan. It IS a true 3 stage charger, just be sure you select the correct battery type at startup

    The faster you charge, the more lead you ""shake"" off the plates. But you have to charge fast enough to prevent it from Sulphating. when batteries are low, they can take a faster charge.
    Lots of opinions in this field.
    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 ,

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Off the grid Island camp - 12v vs. 120v

    The Xantrex Tc series are great chargers. The nice thing about them is that they will put out full output on small floating neutral generators. I run a TC 20 on a Honda EU1000. It puts out the full 20 amps almost at idle. Burns 1 litre every 5 hours. Pretty cheap! It won't quite run a TC 40 however.

    Many chargers, because of the aforementioned power factor, will not put out full out put until the genny approaches 3500 watts. Not very efficient use of gasoline
  • BB.BB. Super Moderators, Administrators Posts: 32,009 admin
    Re: Off the grid Island camp - 12v vs. 120v

    Icarus,

    Glad to hear that the TC Xantrex chargers also have PFC... Their specifications don't mention it.

    See following posts--the TC does not appear to be a power factor corrected charge controller.


    Pretty much why you have to check with the manufacturers themselves to confirm. (current UL/FCC rules should require PFC on any of these chargers--from what I recall--but it has been too many years since I have worked with these specifications to know for sure--plus it seems that there is always one industry that gets its "own set" of requirements grandfathered).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Off the grid Island camp - 12v vs. 120v

    Bill,

    I don't know if The TC series is Power factor corrected or not. What I do know is that they run very well on small eu generators. As I said, I run the TC 20 on an eu1000. My TC 40 needs the 1600 watt honda I have. (At present I have two battery banks, in two buildings). I almost never run the 40 and very seldom run the 20.

    T
  • BB.BB. Super Moderators, Administrators Posts: 32,009 admin
    Re: Off the grid Island camp - 12v vs. 120v

    I suspect that the TC also has some form of PFC...

    The TC is apparently not PFC--see following posts...

    20amp * 15 volts * 1/80% eff = 375 watts on a eu1000i (900 watt continuous)
    40amp * 15 volts * 1/80% eff = 750 watts doe not work on eu1000i?

    So--sounds like still need some headroom regarding a generator with the TC series (and probably any PFC rated charger).

    I know that some other folks here have some experiences with small generators and inverters/chargers--searching a brand/model of charger in Wind-Sun may help identify others that have been successfully operated with smaller gensets.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Off the grid Island camp - 12v vs. 120v

    Bill,

    I knew I'd seen this somewhere: ou have an 850 W generator which can surge to 1000 W and try to power Truecharge 40, but the charger never reaches the 40 A charge current level despite the batteries being heavily discharged. What's happening?

    The Truecharge 40 is being starved of AC power during bulk mode.

    Calculate:

    (43 Amps x 13.5 Volts)
    = 1150 VA
    (0.80 efficiency x 0.63 power factor)

    1150 VA is the power required by Truecharge during bulk charge.

    Although Truecharge will still operate down to 90 VAC input, the drawbacks to an undersized generator are:

    - The TRUECHARGE cannot provide the full bulk current of 43A, therefore it will take longer to charge deeply discharged batteries.
    - If the generator operates at it's maximum output for a prolonged period it may overheat the generator before the TRUECHARGE goes into the lower power absorption charge.
    - We recommend you use at least an 1200W continuous duty generator, and we recommend a 12A AC source in the manual. An alternate solution would be to use the lower power TRUECHARGE 20.


    From Xantrex website. The 40 will run on the eu 1000, but it can stall it when it cycles. If you leave the eco throttle on full bore it helps.

    T
  • BB.BB. Super Moderators, Administrators Posts: 32,009 admin
    Re: Off the grid Island camp - 12v vs. 120v

    Tony/Icarus,

    That is good to know... A power factor of 0.63 is not Power Factor corrected... And that is the problem, the "power required" does not go up (i.e., work), it is just the out of phase current (or current pulses) that overload the windings/wiring of the smaller generator sets.

    1/0.63 = 1.59 or ~59% more current than would be required for a PFC charger... That extra current is not work (so does not need a larger motor) but is just "wasted current" which requires a larger generator/alternator to handle the extra current.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.