Am I losing amps?

QfwfqQfwfq Posts: 2Registered Users, Users Awaiting Email Confirmation
I'm about to add more power to my solar array and it occurred to me that this might not work as intended.

I am upgrading from [email protected] to [email protected]

My charge controller is a 60a mmpt that can do 12v/24v/48v both in and out and my battery bank is [email protected]

So my question is this - if I am getting [email protected] input, my battery bank/system is wired at 24v, and my charge controller has a max of 60a output.... what is happening to the other amps? SImple ohms law states [email protected] = [email protected]  - but I know the charge controller can't do more than 60a... so whats going to happen and do I need to redo my whole system electrical system?

Thank you



  • EstragonEstragon Posts: 2,857Registered Users ✭✭✭✭✭
    The charge controller limit means it will only draw ~30a at 48v from the array.

    One option would be to add another controller to use more of the array capacity if you can use the extra power. This woukd also give some redundancy for when a controller fails.

    Another might be to rewire the bank for 48v depending on what format the batteries are now (eg if you have 2 parallel strings at 24v now). You would likely have to replace your inverter though.

    A third option would be to stay with the one controller. 60a into a 600ah bank isn't bad. Having extra pv would help get max power during light overcast days.

    It really depends on your reasons for adding panels. If you have loads that can use the extra, but not high amp ones that justify 48v, adding a controller may be best. If you're running high draw loads like pumps, the second may be best. If you're just finding the smaller array isn't charging well on light cloud days, the third may be best.
    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
  • QfwfqQfwfq Posts: 2Registered Users, Users Awaiting Email Confirmation
    edited July 2017 #3

    I do have two parallel strings of batteries at 24v so I could tie them together at 48v - but then my inverter wont work and that was/is one of the more expensive components of my system and I really don't want to replace a perfectly good unit.

    maybe I will look into purchasing a small cheap mmpt controller and split the load.

    The reason for upgrading is that I need the extra watts - for some reason I never considered that [email protected] != [email protected]

  • VicVic Posts: 2,908Solar Expert ✭✭✭✭

    Charge Controllers (CCs) are usually rated for output current to the battery/inverter.

    60 Amps IS 60 Amps.   If you double the system voltage, the amount of POWER  that the CC can deliver is doubled,   if the CC has the capability to charge the higher voltage battery. (24 X 60 = 1440 Watts,  48 X 60 = 2880 W,  as an example).

    Of course,  it is generally not a good idea to try to run power systems at their maximum capability continuously.


    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • mike95490mike95490 Posts: 7,925Solar Expert ✭✭✭✭
    Rewireing to 48V bank will give your controller full access to the larger PV array power.   The amps for the controller is OUTPUT amps. 

    But you would need a new inverter..  There is no "small, cheap, MPPT"   controller
    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: ,

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