Battery and charger recommendations?

Hey Everyone,

I am working on the DC side of the electrical in my skoolie. I have been going round & round looking at battery options.

I had about decided just to go with 8 of the Duracell GC2's then I saw the Renogy 12v 200AH AGM's and I can get 4 of them and be carrying less weight & using less space. Anyone have any experience with these?

I am also open to other suggestions for batteries. I am looking for 24v 400AH combined. I understand that I will have more usable capacity with AGM versus FLA. 

When it comes to chargers I am really lost. I had started out looking at the RV converter/chargers and found some "intelligent" 3/4 stage units but upon researching them I found that they are very limited in setting up charge parameters.

What would you all recommend for a reasonably priced charger for the AGM battery bank?




  • EstragonEstragon Registered Users Posts: 1,706 ✭✭✭✭
    AGM doesn't give you more usable capacity (AH), but may be better for high current (eg engine starting) applications. Pound for pound, any lead acid battery will be about the same in terms of storage capacity.

    As well as (sometimes, often?) tending to withstand higher charge/discharge rates, AGMs tend to have lower self-discharge rates, which can be a factor if the batteries will sit for months with no charge source, especially if warm/hot. In marine applications, they also work in odd orientations that would otherwise spill with flooded.

    The downside is they tend to be more expensive than flooded (apples to apples), and tend to not last as long in deep cycle applications because of the inability to monitor SG and maintain accordingly.

    If you decide on AGM for a house bank, be sure the battery manufactures recommended charging spec has a reasonably close match to the charger options, and make sure the charger has temperature compensated charging, ideally with a remote battery temp sensor. AGMs can be quite sensitive to high voltage charging, and can be ruined quickly if they vent gas, or ruined slowly by sulfating with a too low temp compensated absorb voltage.
    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
  • BB.BB. Super Moderators Posts: 26,973 admin
    I did a quick look, but did not find his post. Marc Kurth, who sells AGMs (and other) batteries had some suggestions... Hopefully, he can reply.

    Or you can try sending him a private message. Kurth


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PNW_StevePNW_Steve Registered Users Posts: 21 ✭✭
    Thanks for the replies.

    Please help me understand: "AGM doesn't give you more usable capacity (AH)"

    If I have a 400 A/H FLA bank that I can safely take to 50% DOD I will have 200A/H of usable capacity.

    If I have a 400 A/H AGM bank that I can take safely to 80% DOD I will have 320 A/H of usable capacity.

    It's been 30+ years since my last math class. As best I can figure 320 is more than 200. What am I missing?

     Also, can anyone make recommendations regarding chargers? I have not had much luck, so far, finding anything other than the RV converter chargers and forklift chargers. Neither look like the best solution for my application?

    Lastly, has anyone here had any experience with Renogy batteries?

    Thanks again.
  • mike95490mike95490 Solar Expert Posts: 7,360 ✭✭✭✭
    You can take any of them to 50% or 80%.  Deeper discharges give you fewer total cycles.  FLA or AGM

    Renogy batteries

    i don't think they actually MAKE batteries, I suspect they are re-branded somethings. That may make warranty claims fun,

    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

    gen: ,

  • mcgivormcgivor Registered Users Posts: 1,356 ✭✭✭✭
    edited January 2 #6
    The depth of discharge will have an effect on life expectancy, flooded or AGM, the deeper the discharge the fewer the cycles, both types are still essentially the same chemistry. Manufacturers claims are based on accelerated testing in laboratory conditions which are very different from real life, the ability to recharge fully immediately after discharge, controlled temperature and so forth. There are flooded battery manufacturers which claim discharge to 80% as well as AGM, but the rule of thumb is, it's best to limit it to 50% maximum for better life expectancy. Not all LA batteries are created equal regardless of type, more robust types, tubular for example, are better suited to deep discharge applications, albeit at a higher initial cost.Therefore it's best to assume they're equal, same manufacturer, in terms of capacity, the application of which to choose should be dependent primarily on what is better suited, lower maintenance, orientation etcetera. Attached are pdf files for offerings from the same manufacturer which demonstrate the life expectancy versus depth of discharge for both flooded and AGM. One advantage of flooded is the ability to more closely monitor what is happening inside the cells and the ability to correct weak cells through equalization, something not possible with AGM. Just a collection of thoughts.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • 2manytoyz2manytoyz Solar Expert Posts: 364 ✭✭✭
    I had 8 of the Duracell GC2's in my solar power setup at home.  They lasted 4 years.  I had gotten a year longer with the previous set of Energizer GC2s.  Very hot in FL, and heat limits the life of batteries.

    I replaced them with Trojan T105 batteries for $112 from the local golf cart shop.  I then added the Trojan Hydrolink system to water them - much easier than manually filling them.

    When solar isn't cooperating, I use an Iota 75A charger to get the job done.  I added an IQ Controller to make it a 4 stage charger.  While I can't change the settings, it does an excellent job right out of the box.  I can unplug the IQ module, put in a supplied jumper, and force it to charge at 14.2V (fast charge).  Details of the IQ Module here:

    Pics and details of my battery bank here:

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