Solar Batteries not charging all the way

karenyamilkarenyamil Registered Users Posts: 2
Hello guys, I am new to the solar system, I currently live in a van and I have two solar panels and two AGM batteries from Renogy. I use their new 1000W 12 volt pure sine wave inverter with power saving mode and a 20 AMP MPPT charge controller.

When I first got them, obviously working fine, I notice I was getting more voltage than W so I bought something called “Branch Connector Y in pair MMF + FFM” for parallel connection for my 2 solar panels. I look more information into it and they said I need this to get my solar in parallel and get more energy to charge my batteries. Is that right?

I used the batteries from time to time (at that moment I wasn’t living in the van yet) and they charged normally, but after a couple of weeks I notice that my batteries were not staying charged, it was so bad that it drain almost completely. I decided to turn off my inverter and not use the batteries. I did that, it took around 2 months to get to 50% charged. I also want to say that I live in Mass and this was happening between October and November so it was most of the time cloudy during the time I turn off my inverter.

I notice that turning off my inverter helps the battery charge. Now for the past 3 weeks I been getting not so bad weather, I have more sunny days then I though and somedays it says is 100% charged but as soon as I connect my ipad, my iphone or switch it goes from 100 to 90 to 70 to 66 or 61 and it stays like that for a while. I have charged my ipad or switch in 61 for an hour or more and it stays the same but my batteries are never actually charged 70 to 100%. I even had time where my batteries were 51% or 56%.

So I explain what I could here, honestly I know nothing about solar, batteries, wiring. I did my best looking up videos, watching them more than 10 times, going back to my system and checking if I did everything right but still I just can’t figure out if I am doing something wrong or bought something that doesn’t go together.. PLEASE help me understand this, I don’t know the terms or names of a lot of this things so explain it to me as if I was a child because seems like that’s the only way for me to get it.

Oh and I forgot to say that I end up just using one battery to see if the solar/sun was not enough to charge two batteries. I did this a week ago and still is not charging all the way, it stays in the 60’s.

I apologize for my bad English, I am trying to get better at it.

Comments

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    That is a very large inverter and it consumes power just by being turned on.   Leaving it on 24/7 eventually drained your batteries and with cloudy weather, they never recharged and have eventually become ruined.
     When batteries charge up from dead to full in a short period of time, confirms they are sulfated and if it was a one day event, they might be recoverable, but after months, they are just dead.
      Sorry, but you have learned an expensive lesson - that you cant take more out of a battery than you charge into it.
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 32,642 admin
    edited January 2021 #3
    Hi Karenyamil, welcome to the forum.

    The direct answer is what Mike said above--You have a small solar power (charging) system and a relatively large battery bank+load.

    Lead Acid (and AGM) batteries need to be recharged pretty quickly after they have been discharged. If you let them sit at less than ~75% state of charge for days/weeks/etc... The batteries will tend to "sulfate" and lose most of their capacity--Permanently.

    We have several ways we can proceed here... One is to measure/understand your daily loads--Which defines the size of the battery bank. And then with the daily loads, size of battery bank, and where you are located/etc., we can design a system that will meet those loads.

    In areas with poor sun (like the North East), you don't really harvest much energy in the winter. For example, a 200 Watt array mounted flat to a van roof, in Boston Mass:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Boston
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a horizontal surface:

    JanFebMarAprMayJun
    1.80
     
    2.62
     
    3.61
     
    4.46
     
    5.13
     
    5.50
     
    JulAugSepOctNovDec
    5.60
     
    4.99
     
    4.04
     
    2.93
     
    1.89
     
    1.54
     
    For example, in January, 200 Watts of panels (flat) will harvest an average daily energy of:

    200 Watt array * 1.80 hours of sun (January) * 0.52 off grid AC system eff = 187 WH per day
    200 Watt array * 1.80 hours of sun (January) * 0.61 off grid DC system eff * 1/12 volt DC battery = 18 AH @ 12 volts per day (if you were running DC loads)

    Your 12 volt 1,000 Watt sine wave inverter draws about 1 amp @ 12 volts just being turned on:
    • 1 amps * 12 volts = 12 Watt "tare" losses
    • 187 Watt*Hour harvest / 12 Watts average inverter tare loss = 15.6 Hours per day of power just to run the inverter
    So--For your setup (making lots of guess), just running your inverter with no loads for 16 hours per day, uses more energy than you harvest (in January) on an average day...

    When running solar in a van--You need to 1) have very efficient/low power loads; 2) a battery bank to support those daily loads; 3) a solar array sized to recharge your bank daily; 4) if you don't have enough solar--Then a backup means of charging (shore power, Van alternator, backup AC genst + AC charger, etc...

    We are very happy to walk you through the design process... So, if you can help us with understanding your loads (amps * hours per day, Watts * Hours per day, rough location, any backup charging sources, etc.).

    Doing it step by step will help you to better understand your system and its capabilities, and hopefully save you money in the future (your batteries should last around 3-5+ years in a van).

    The reality is that you need to have as few loads as possible and an "over sized" solar charging system (to allow for a day or two of bad weather, and the occasional heavier loads). And for a van--You do not have much room for solar panels or battery bank... Off grid solar power is a limited commodity.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • karenyamilkarenyamil Registered Users Posts: 2
    mike95490 said:
    That is a very large inverter and it consumes power just by being turned on.   Leaving it on 24/7 eventually drained your batteries and with cloudy weather, they never recharged and have eventually become ruined.
     When batteries charge up from dead to full in a short period of time, confirms they are sulfated and if it was a one day event, they might be recoverable, but after months, they are just dead.
      Sorry, but you have learned an expensive lesson - that you cant take more out of a battery than you charge into it.
    Wow, I didn’t know that 😐.
    i mean after a month I turn if off because of that problem although during the process of the batteries dying I never thought the inverter was the problem. I should have done more research on which inverter to buy and I guess one battery is enough for the solar panels I got and the amount of sun I receive. Thank you so much, I appreciate your help. 
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Sadly, solar power is not all the effortless joy the hucksters make it to be.  And then when you discover it, you are out some serious money..
    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 ,

  • PhotowhitPhotowhit Solar Expert Posts: 5,830 ✭✭✭✭✭
    mike95490 said:
    Sadly, solar power is not all the effortless joy the hucksters make it to be.  And then when you discover it, you are out some serious money..
    So long as there is reasonable expectations, to me, it is exactly the effortless joy I expect!

    No sun, no joy!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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