Newbie needing help

[Frank S]

Hi Friends,
I have a few questions to help me get started.  I have 6 Trina 295 watt panels, MS 200 classic, 4 Trojan L16RE-B batteries for a 24 volt system feeding a Samlex SA-2000K inverter.  I read through the manual several times and read through numerous pages on this forum.  But I cannot find some answers to some very simple questions.  Like how long should the absorb stage run?  The battery manufacturer tells you what voltage to charge to but nowhere can I find how long to charge.  You have a default but i question if that is the optimal.  Do I run a longer absorb time in the winter than the summer? Why do I need to add a time in?  Doesn't the controller switch to the next stage for you taking care of that? I have watched numerous of your u-tube videos but where does a newbie get the basic information to start the learning process?  The manual tells you how but not why.  I want to learn the whys.
Any help will be appreciated.
Frank S

[dgd]

I'd recommend doing a google search as I seem to remember some extensive discussions on this subject on other Solar forums.

dgd

[Vic]

Hi Frank,

The amount of time required for the Absorption stage is almost completely dependent on the amount of energy removed from the battery during discharge -- the Depth Of Discharge (DOD).

One way to help determine this amount of time for a certain DOD is by monitoring the amount of charge current going into the battery during Absorb.  Most Flooded batteries (your batteries are Flooded -- removable vent caps).  When the current going into the batteries diminishes to between 1% and  2% of the 20-hour Capacity of the battery,  it is generally considered that the battery is fully charged.   Using a high quality Hydrometer,  you can actually measure the State Of Charge (SOC) of the individual cells of the battery,  and confirm just what amount of current is required to finish charging the battery.  In my opinion,   a good Hydrometer has a glass outer tube,  and a glass float,  and is calibrated with exact numbers,  not simply colors,  or judgment words,  like  good,  or full or similar ...

There are only a couple of things that make determining the current that is going into the battery as charge current,  verses other currents that run the inverter,  and any loads on the inverter inaccurate.   Loads on the battery will appear to the Classic as battery charge currents,  as the Classic cannot tell the difference between charge current and loads on the battery.  A Shunt installed in the negative lead of the battery would allow you to measure only the current going into the battery as charge current.

The Classic has a very useful function -- End Amps  -- which can be set to a value of current that is supplied by the Classic.  When this value is reached during Absorb,  the Classic will transition to Float.  But,  again,  the Classic (at this point)  cannot tell the difference twix battery charge current and any other loads on the battery -- inverter loads and anything else connected to the battery as a DC load.

Another factor that can change the charge current required for full charge,  is the temperature of the battery bank.  This factor is usually fairly small,   and is generally ignored.

Enough for now,   Vic

[Frank S]

Thanks, Vic.

[boB]

Also, check out some of our videos on the midnitesolar web site.  There may be some good info there too.

We are adding more informational videos as we can.

boB