Did I kill my batteries

tedktedk Posts: 2Registered Users
Bear with me. I'm somewhat of a beginner at this and my technical knowledge is minimal at best. My application knowledge is a bit higher. I know somethings, but not everything and as some might say, knowledgeable enough to be dangerous. Please keep your answers short and please, don't be preachy.

In 2015, against my better judgement and on the advice of the salesman who didn't know any better, I was sold 8 - Rolls 486 aH lead acid batteries for my 48V system on my off-grid house in upstate NY.  I had originally asked for AGM instead because I was worried about freezing (the batteries were going to be stored in an outdoor shed with no heat). He assured me there would be no problem. System installed and running wonderfully in September. Come December I started seeing problems. February 2016 came along and so did 5 consecutive days of sub zero temperatures which left me with 8 very expensive ice cubes. No restitution and I'm out 8 batteries and a useless solar array. Bear in mind, I was given zero instruction, either verbally or by way of manual, on the proper use of the batteries or the solar array itself. The included installation instructions ONLY guided me through installation and basic operation, i.e: To turn on and off the system, do this. That's it.

I still don't have any batteries, but, I did have two 12V 75aH AGM's from a smaller solar array I had bought many years ago and it worked great. So this past weekend, I figured what the hell, let's give it a try. So, I hooked up these two batteries to my large array (I know the voltages are different, bear with me). Oddly enough the Magna charge controller fired up and began reading voltage and all that, but it obviously wasn't enough to send power to the house. I let the system stay on for a few minutes so I could check a few things. Then I noticed a rotten egg smell. CRAP! I ran to the panel combiner box and realized I forgot to shut off half of the panels to equal the voltage of the batteries. So I quickly shut half the panel breakers off but back at the batteries I still had that rotten egg smell.  Fearing a mushroom cloud, I shut the whole system down and the smell dissipated.

So, did I kill these batteries by sending 48V to them? 

Keep it simple kids and thank you in advance for your thoughts.



  • EstragonEstragon Posts: 2,848Registered Users ✭✭✭✭✭
    You may well have toasted the batteries.  AGMs are quite sensitive to overcharging, and  the smell  is a bad sign.  I would check the resting voltage on each of the batteries.  If it's about normal (12.6ish volts).  I would try a load test by connecting a known load of about 5-6a @12vdc (eg. auto light bulb).

    BTW, shutting off half the combiner box likely wouldn't reduce the voltage.  Panels are typically wired in series strings, then combined in parallel in the box.  In parallel, current adds but voltage stays the same, so shutting off half the breakers would give you half the amps but about the same voltage.  Some (but not all) charge controllers will auto-detect battery voltage providing they are powered up by battery first, and only connected to solar panels after booting up.

    As for batteries freezing, a fully charged battery won't freeze until much lower temps than you'd get.  In order to freeze, they'd have to be sitting in a partly charged state for some time.  That, in itself, would lead to early death for the bank.
    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
  • tedktedk Posts: 2Registered Users
    Thank you Estragon. That's what I had figured. Bummer. And thanks for the tip on the panels. I should have known that since I installed them. To soon old, too late smart.

    And yes, the batteries were in a discharged state (down to 60%) when they froze. 
  • PhotowhitPhotowhit Posts: 4,708Solar Expert ✭✭✭✭
    tedk said:
    Thank you Estragon. That's what I had figured. Bummer. And thanks for the tip on the panels. I should have known that since I installed them. To soon old, too late smart.

    And yes, the batteries were in a discharged state (down to 60%) when they froze. 

    I doubt the batteries had that much charge in them. With activity it would likely need to be 20% state of charge to freeze. Rolls do have a different charging profile wanting a higher voltage during charging.

    Between that and not understanding how charge controllers work, I would suggest you need to learn more about your system.

    We could likely give you a hand if you would like to describe your system, type and number of modules, charge controller and other equipment on hand. There are some people who will sell a system with a lot of interaction, but it's still normal to understand your system the maintenance and upkeep.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • mcgivormcgivor Posts: 2,219Solar Expert ✭✭✭✭✭
    @tedk said  So, did I kill these batteries by sending 48V to them?  
    Most probably some harm was done, the extent of which is probably in direct proportion to the amount of smoke/ gas which was released, not a good situation, sorry to hear about your experience.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

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