Iota battery charger

I was looking at the Iota DLS 27-40 battery charger to use a generator for charging a battery bank. How would the 120 volt charger compare to say the 240 volt charger? Both are rated at the same amps for charging. If using a generator, I was just wondering which would be more efficient. I considered an inverter/charger with generator support but I prefer to keep each one separate in case one fails.


  • mike95490mike95490 Solar Expert Posts: 9,359 ✭✭✭✭✭
    Re: Iota battery charger

    120V or 240V, only difference is that the 120V version will only load 1 leg of a 240V generator, leading to a little bit of imbalance.
    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

    gen: ,

  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Iota battery charger

    In theory, the higher input voltage is a bit more efficient/cheaper to manufacture (less current, smaller wires, etc.).

    In practice--It actually depends on your genset. You have the 120 vs 120/240 VAC genset choice.

    Next, you can get gensets 120/240 VAC that can output 4,000 watts on the 240 VAC connections and only 2,000 watts per 120 VAC connection. And there are a few gensets that can output the full 4,000 watts on a single 120 VAC connection.

    So--If you already have a 120/240 VAC rated genset and have 120/240 VAC main panel on your home (if you have utility power), then I would probably pick the 240 VAC input charger.

    If you have a 120/240 VAC genset that can output its full rating on 120 VAC--Your choice (best price, backup to the backup genset, etc.).

    If you have only 120 VAC genset (or available grid/utility power), then pick the 120 VAC unit.

    If all of your other AC loads are 120 VAC--Then staying with 120 AC for the charger may make more sense (you can use 120 VAC genset if needed). If you have 240 VAC loads (such as a well pump), then a 240 VAC charger is not a problem.

    The Iota chargers are not all that "efficient" (we can get into Power Factor/VA, etc.)--But they are built like a tank and output their rated values... Not all charge controllers do that.

    If you want efficiency, many of the Inverter/Chargers are more efficient and have a better Power factor ("good" power factor is >=0.95; Iota's PF is around 0.67). Poor power factor does not really use more fuel (first order effects), but does use more AC current (poor PF means more current), which means a larger genset to carry the "extra" current through the windings/wiring (larger genset uses more fuel when operated at less than ~50% efficiency).

    In many cases, for an off grid home, folks will have two generators--One sized for minimum/nominal loads (a Honda eu2000i or similar Yamaha inverter+generators) are great for limited power needs (just bulking up a battery in bad weather, running some AC loads while the Main Inverter is being repaired, etc.)--And a second larger genset to run the well pump a few times a week/shop/etc. when more power is needed (or the first genset fails to start).

    So--All of this is shades of gray--And either would work fine for your needs. Just look at your overall needs (120 vs 240) and available power sources (grid, generator) and see what makes the most sense to you.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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