5 or 10W panel to keep generator battery charged

porch13porch13 Registered Users Posts: 62 ✭✭✭
I'm purchasing a home that has a Generac generator that runs the well pump.  The previous owner had issues with the generator battery losing charge between uses of the well.  I'd like to as a small panel to the roof of the building to keep the battery topped off.  The battery is a 12V with 675 cranking amps / 540 cold cranking amps.  NAWS carries both a 5 and a 10 watt Solartech panel.  Would the 5W be sufficient if I get plenty of sun? 
Northern Arizona...4050 Watt off-grid system - Outback FP1 - Rolls 605 in a 48V bank

Comments

  • just startingjust starting Registered Users Posts: 228 ✭✭✭
    I have a 80 watt panel with a morning star sunguard 4.5 cost a little more but use it for all 12 volt and you could put it on a south facing wall so you don't have to worry about snow if that's a problem
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • Desert RatDesert Rat Solar Expert Posts: 122 ✭✭✭
    I have small (<2 watt) battery maintainer panels on several vehicles that sit for months without being started, and they work fine.
    I think you would be OK with the 5 watt panel.
  • JohannJohann Solar Expert Posts: 240 ✭✭✭
    porch13 said:
    I'm purchasing a home that has a Generac generator that runs the well pump.  The previous owner had issues with the generator battery losing charge between uses of the well.  I'd like to as a small panel to the roof of the building to keep the battery topped off.  The battery is a 12V with 675 cranking amps / 540 cold cranking amps.  NAWS carries both a 5 and a 10 watt Solartech panel.  Would the 5W be sufficient if I get plenty of sun? 
    I would get a bigger panel, maybe a 100 watt panel and a charge controller.
    A 100 watt panel will give about 5 amps.
    I would hook wires and a switch to the battery and run a 12 volt LED light of the same battery also. This way you would have a light in the well house/ generator house if needed.

  • jonrjonr Solar Expert Posts: 1,298 ✭✭✭✭
    edited September 2016 #5
    I'd buy a low cost PWM solar charge controller.  5W panel should be enough, more if there are frequent starts with short runs.  10W with no controller is too much.

    https://www.solar-electric.com/outback-power-smartharvest-sccp05-050-solar-charge-controller.html

    I am available for custom hardware/firmware development

  • Marc KurthMarc Kurth Solar Expert Posts: 478 ✭✭✭✭
    edited September 2016 #6
    If the genset doesn't run often enough to keep the battery healthy (like your car) I would suggest:

    1) Use a battery that has a low self-discharge rate like 1% or 2% per month instead of 7.5%-15% or more per month. That is not a large battery so the additional investment over a cheap battery won't break the bank.

    2) Add a low current float charger via solar that will hold something like 13.5v. That will hold the battery steady indefinitely. It is important to realize that you will destroy the battery prematurely if the voltage isn't properly controlled. Some cheap solar kits are uncontrolled.

    Marc
    I always have more questions than answers. That's the nature of life.
  • porch13porch13 Registered Users Posts: 62 ✭✭✭
    Thanks for the feedback, guys!  I ordered and just received a little Genasun GV-4 mppt controller and will pick up a 10 or 20 watt planet to go with it.  I read some really great stuff about the controller and I'm looking forward to getting it set up.  I really like the idea of adding a 12 light in the well house and I'll definitely do that as well!
    Northern Arizona...4050 Watt off-grid system - Outback FP1 - Rolls 605 in a 48V bank
  • AnawaAnawa Solar Expert Posts: 211 ✭✭✭
    Porch, you may want to check the wiring connections for the battery in the generator. I had the same problem, battery was losing charge. I discovered that my electrician overlooked connecting the generator's built-in charger designed to charge the battery from house wiring. 

    If you do not have the generator operators and/or the installation instructions, then I would go online to see if your model Generac has such a feature. If so, maybe another option for you.

    Paul
    in Georgia
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
  • porch13porch13 Registered Users Posts: 62 ✭✭✭
    Thank you for the tip, Paul.  I will definitely look into it.  I have a lot to learn about this Generac....
    Northern Arizona...4050 Watt off-grid system - Outback FP1 - Rolls 605 in a 48V bank
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