DIY controller advice

Ruen Registered Users Posts: 7
Hi all,
Newby here - from Eastern Europe (Bulgaria).
I'm building a solar panel off-grid system wich has 4 X 63 W, 20 V, 3.6 A panels and 30 X 2 V, 200 Ah accu cells, connected in 5 X 12 V, 200 Ah batteries.Here is the question - I can't deside what kind of solar controller to use.I read a lot and now I'm confused - everything in my mind is a mish-mash.
I'll be happy to hear you opinion. Type, power, manufacturer ?
Thanks in advance.


  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: DIY controller advice

    If your solar panels are less than 200 watts--usually a PWM controller would be the best choice.

    If you have more than 400 watts, many times, a MPPT type controller is a better (but more expensive choice).

    If you are very price sensitive, you can get larger PWM (60 amp) charge controllers, but you have to pay close attention to the Vmp/Imp of the panels and keep wiring runs short/use heavier gauge wire (from array to charge controller).

    Start reading here:

    All About Charge Controllers
    Read this page about power tracking controllers

    And all of this is done to keep your battery bank healthy--read the Battery FAQ's too to understand what you need to do for them:

    Deep Cycle Battery FAQ

    Since your are in Europe, there may to some better options (less costly, but still nice units) vs what we can buy in the US. Perhaps some folks here can give you some "local to you" options.

    In the end, you may end up doing a paper design of two or more solar system options and see what the end price vs options/issues that each type of system will be best for you.

    For the US, the MorningStar, Xantrex, and Rogue PWM/MPPT controllers are very reliable units and some of the more modern designs (lots of data logging, one one of the MorningStar 60 amp MPPT units can be plugged directly into your router as a webserver). Outback also has European distributors too.

    In the end, define your loads first (watts*hours, peak watts, voltage, current, where will the panels be mounted--close or far from battery bank--etc.). Remember that off-grid solar costs upwards of 5-10x the cost of utility power--so conservation is a very important first step (use as little power as possible) before spending money on the solar power system itself.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: DIY controller advice

    "5 X 12 V, 200 Ah batteries"

    if i read this right you have 5 parallel strings at 12v and 200ah each. if that's correct then you a 12v battery bank rated for 1000ah. to properly charge the bank you need at least a 5% charge rate and that would mean at least 50a which i don't foresee 4 3.6a 12v pvs doing much for. 3.6x4=14.4a. 14.4a/1000ah=1.44%.
  • Ruen
    Ruen Registered Users Posts: 7
    Re: DIY controller advice

    Hi guys,
    First thank you for the replies.

    NIEL - you are rigth - 1.44% is not enough, but I think to start with this and to double the panels till the end of the summer. Exept this I will use the power for one refrigerator in the begining, and next year I'll continue with the panels. This power I'll need for a house in the moutain, which I use during the weekends only.

    BB - The goods in Eastern Europe are mostly bad quality China stuff, thats why I bought solar cells from USA. I found a controler EPIP30 30A (China) about $100, but
    maybe it'll be better to buy something more expencive to keep the batery life long. The bateries are 4 OPvS 200 Ah 2 V .