Where would I put the battery monitor?

SparkySparky Registered Users Posts: 23
I found this drawing on the net. It's pretty close to what I'm going to start out with.

Some questions though.

1--Why not use the load out on the charge controller to power the 12 volt items?

2--where would I put a battery monitor in this setup? I will be using the Trimetric 2020 for this.

3--Is the charge controllers amp ratings based on the amount of amps being pulled through it or the amount of amps that the pv panels are putting out?

any help would be super, thanks.

1hasnb.jpg

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,514 admin
    Re: Where would I put the battery monitor?
    Sparky wrote: »
    1--Why not use the load out on the charge controller to power the 12 volt items?
    There is an LVD (Low Voltage Disconnect) terminal on many charge controllers... They are typically current limited (8amp or so for many) and can turn off loads if the battery is near dead (not accurate, does not "save" a battery from damage)--but if you attach large loads and/or loads with surges--it can blow the LVD output electronics. So, not normally recommended to connect too.

    If you are talking about eleminating the battery and just you panels and a charge controller... Not usually a good idea... Many charge controllers need a not-dead battery to "wake up" and charge. Also, the battery does most of the voltage regulation (and supplying heavy currents for surges). A solar charage controller is not usually designed to regulate without a battery attached.

    If you are asking about connecting your load to the charge controller's battery output connections... For several reasons that is generally to be avoided...

    1. The charge controller needs accurate measurement of the battery voltage. Placing loads that vary in current requirements (especially AC Inverter) can confuse the controller and actually cause the controller to drop MPPT current regulation.

    2. Safety--the load current available is the sum of the battery + charge controller--or almost double the availabe current -- so there needs to be fusing/wire awg sizing to make it safe.

    3. Connecting all loads/charge sources to the battery provides the most stable, lowest voltage drop (in general) and clearest wiring / safety of system. Usually, the battery is the center of the "star" and each + lead that leaves the battery goes through an appropriately sized fused.
    2--where would I put a battery monitor in this setup? I will be using the Trimetric 2020 for this.
    Usually the shunt is connected to the negative terminal of the battery (battery on one side, Common - bus connections on the other).

    The battery monitor shunt needs to measure all current into and out of the battery.

    Other shunts may be installed to measure other currents as needed.
    3--Is the charge controllers amp ratings based on the amount of amps being pulled through it or the amount of amps that the pv panels are putting out?
    The controller is generally rated on output current.
    • For a PWM controller (pictured in your post)--the input equals the output current.
    • For a MPPT controller--the output current is either equal too or greater than the input current (depends on your Arrays Vmp voltage configuration--one or more panels in series, etc.).
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,377 ✭✭✭✭✭
    Re: Where would I put the battery monitor?
    Sparky wrote: »
    I found this drawing on the net. It's pretty close to what I'm going to start out with.

    Some questions though.

    1--Why not use the load out on the charge controller to power the 12 volt items?

    2--where would I put a battery monitor in this setup? I will be using the Trimetric 2020 for this.

    3--Is the charge controllers amp ratings based on the amount of amps being pulled through it or the amount of amps that the pv panels are putting out?

    any help would be super, thanks.

    1hasnb.jpg

    Drawing ? No drawing attached.

    Charge Controller LOAD terminals are limited current, and will usually disconnect only when battery is -90% , way too late.

    CC have separate ratings for LOAD and BATT (usually)
    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 ,

  • SparkySparky Registered Users Posts: 23
    Re: Where would I put the battery monitor?
    BB. wrote: »
    There is an LVD (Low Voltage Disconnect) terminal on many charge controllers... They are typically current limited (8amp or so for many) and can turn off loads if the battery is near dead (not accurate, does not "save" a battery from damage)--but if you attach large loads and/or loads with surges--it can blow the LVD output electronics. So, not normally recommended to connect too.

    If you are talking about eleminating the battery and just you panels and a charge controller... Not usually a good idea... Many charge controllers need a not-dead battery to "wake up" and charge. Also, the battery does most of the voltage regulation (and supplying heavy currents for surges). A solar charage controller is not usually designed to regulate without a battery attached.

    If you are asking about connecting your load to the charge controller's battery output connections... For several reasons that is generally to be avoided...

    1. The charge controller needs accurate measurement of the battery voltage. Placing loads that vary in current requirements (especially AC Inverter) can confuse the controller and actually cause the controller to drop MPPT current regulation.

    2. Safety--the load current available is the sum of the battery + charge controller--or almost double the availabe current -- so there needs to be fusing/wire awg sizing to make it safe.

    3. Connecting all loads/charge sources to the battery provides the most stable, lowest voltage drop (in general) and clearest wiring / safety of system. Usually, the battery is the center of the "star" and each + lead that leaves the battery goes through an appropriately sized fused.

    Usually the shunt is connected to the negative terminal of the battery (battery on one side, Common - bus connections on the other).

    The battery monitor shunt needs to measure all current into and out of the battery.

    Other shunts may be installed to measure other currents as needed.
    The controller is generally rated on output current.
    • For a PWM controller (pictured in your post)--the input equals the output current.
    • For a MPPT controller--the output current is either equal too or greater than the input current (depends on your Arrays Vmp voltage configuration--one or more panels in series, etc.).
    -Bill

    OK, I see what your saying. I'll be using batteries for sure on this system. just wasn't sure where to put the monitor.....thanks for the help.;)
  • SparkySparky Registered Users Posts: 23
    Re: Where would I put the battery monitor?
    mike90045 wrote: »
    Drawing ? No drawing attached.

    Charge Controller LOAD terminals are limited current, and will usually disconnect only when battery is -90% , way too late.

    CC have separate ratings for LOAD and BATT (usually)


    Thanks Mike, I just noticed the some Controllers don't even have a load feature. I'll tag off the battery feed for mine..
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