charging with manual charger

wellbuiltwellbuilt ✭✭✭Solar Expert Posts: 400 ✭✭✭
Hi all, could someone tell me how hi a voltage I can charge 2 gc 230ah battery at 12v with manual 30amp charger 
model 3010 farm and ranch . 
This time of year I read full charg in the pm and 12.2/3 or so most mornings .
I have been running 30 amps for 1hr in the am to get thing going and my 210 watts of solar takes me to full most days
i would like to know how hi a voltage I can go up to with out over heating ,I need mor power because my panels are covered with snow . 
 The system is in a travel trailer and is 2 seasons old 18 months and is used weekends apr to October and has been running on only solar , cells run almost the same state of charge and I take them to 15 volt 10 amps every 2/3 months 
I add about 12 oz per battery at this time 
The heat in the trailer is drawing down the battery's when it is in the low20s
Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .

Comments

  • BB.BB. admin Super Moderators, Administrators Posts: 29,629 admin
    In general, about 14.75 volts is a good set point for day to day "bulk/absorb" charging. After the charging is complete, then dropping to 13.6 volts or so for float.

    For flooded cell batteries, monitoring specific gravity will tell you if your day to day charging is optimum for your usage (i.e., you want to reach > 90% state of charge at least once or twice per week for a "cycling" lead acid battery bank).

    Water usage is another good indicator. If you have to add water more often than once per month (or cell plates are exposed to air)--You are probably over charging (too high of charging voltage, too long of absorb charging time, etc.). If you are not adding water every 3-6 months at least, then you are probably under charging.

    However, there are always exceptions. Many industrial type batteries have smaller reservoir  capacity (need watering quite often). Where many cells designed for solar power systems have more water capacity above the plates. Also, there are types of lead acid cells where they simply use less water (for example the Trojan RE type batteries).

    And, watch the battery bank temperature. High charging voltages/long equalization charging times can increase the temperature of the battery bank and exceed the battery's ratings.

    High temperatures, and sustained elevated temperatures of battery banks will reduce their lifetime (engineering rule of thumb, for every 10C or 18F increase in temperature (over 25C/75F) will decrease its aging life by 1/2).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • wellbuiltwellbuilt ✭✭✭ Solar Expert Posts: 400 ✭✭✭
    The charger has no set points just 6v 30 amp 12v 10 amp 12v 30 amp and boost .
    Set on 30 amps we start charging at around 22 amps on the meter and volts read maybe 13.4 volts
     after an hour I'm getting up to 14 volts and the amps are around 11/12 amps in
    At14.8 I'm at about 9/10 amps input at 15volts I'm at 8 amps input and I stop.
     From 14.8 to 15 volts only takes 15 min or so .
     Should I stop charging at 14.8 volts ? 
    If I drop down to 10 amps 12 volt the voltage gos to 13.9 about  should I keep charging ?
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • BB.BB. admin Super Moderators, Administrators Posts: 29,629 admin
    From 14.8 to 15 volts only takes 15 min or so .
    That is not going to make much difference in the grand scheme of things (flooded cell batteries are pretty forgiving).

    You should be somewhere about 10% rate of charge or ~23 amps as your "nominal rate of charge".

    The absorb is supposed to be a lower set point voltage (14.75 volts maximum or so)--And you should see the battery draw less and less current (down to below 2% or ~4.6 amps for an older flooded cell battery--maximum "tail current"--Newer batteries will be much less than 1% or even 0.1% for AGM type batteries).

    If you have too high of charging voltage, you will not see that normal absorb tail and can damage the battery (equalization/bubbling/gassing the battery erodes plates, generates heats, drives oxygen into the positive plates/causes corrosion).

    Is 2-6 hours at 14.5 to 14.75 volts (75F) equivalent to 15.x volts at 10 amps--I could not tell you, but I would suggest that is not an optimum charging regime.

    A continuous charging current of 2% or higher (for many hours/days/weeks/etc.) is dangerous and can cause a battery fire (excessive gassing, driving water out of cell, expose plates, cause meltdown/material failures).

    I would suggest that you look for a better battery charger. I am not a fan of manual intervention for ongoing operations. At some point, real life will distract you (family emergency, etc.) and the battery left on the charger at elevated voltages is not safe.

    All of the above is my humble opinion--I try to default to conservative configurations/operations. Others with more experience than I can and will have different suggestions/opinions.

    -Bill "my 2 cents worth" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • wellbuiltwellbuilt ✭✭✭ Solar Expert Posts: 400 ✭✭✭
    Thanks bill I only have a few more weeks on these battery
    Next year I will have new system in the house
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
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