12 volt charge settings...

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bobdog
bobdog Solar Expert Posts: 192 ✭✭
Just a quick question. Did a search and didn't find any specifics.

Added 2 KD135s this week so I bought a TriStar 45 PWM CC and need to set the absorption voltage settings. I have a choice of 14.4, 14.6, 14.8 and 15.0. all into 12 volt FLA battery bank. My Prostar 30 had a default of 14.4 but for what ever reason I'm thinking to charge the batteries faster I should bump the Tristar up to 14.6 or 14.8. Thoughts?

Also, the Prostar had a default value of 15.1 for EQ voltage where as the Tristar sets it at 15.3.

Finally, the Prostar had the default float voltage at 13.7 where as the Tristar has it at 13.4.

So, any suggestions on 1) what to set the absorption voltage at, and 2) why the different defaults on the EQ and Float values?

Thanks.

Tim

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: 12 volt charge settings...

    The question here is; what does the battery manufacturer recommend?
    If they're not specific (Trojan like 14.8V Absorb) start with the default settings: Absorb @ 14.4 Volts, Float @ 13.4 and see how that works. It gets to be a bit of an art watching to see if they're "bubbling right" and yet not using too much water.

    Since battery chemistry varies from one make to another, so do recommended charge set points. Less expensive charge controllers can't have every possible permutation, so they pick ones that will keep most batteries going. Fine-tuning is up to the end user, based on system performance.

    Yet another reason why inexpensive "golf cart" batteries are repeatedly recommended for the first-time user. :roll:
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
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    Re: 12 volt charge settings...
    The question here is; what does the battery manufacturer recommend?
    If they're not specific (Trojan like 14.8V Absorb) start with the default settings: Absorb @ 14.4 Volts, Float @ 13.4 and see how that works. It gets to be a bit of an art watching to see if they're "bubbling right" and yet not using too much water.

    Since battery chemistry varies from one make to another, so do recommended charge set points. Less expensive charge controllers can't have every possible permutation, so they pick ones that will keep most batteries going. Fine-tuning is up to the end user, based on system performance.

    Yet another reason why inexpensive "golf cart" batteries are repeatedly recommended for the first-time user. :roll:

    I was thinking I saw in a recent post by you that you used golf cart batteries and wondered if you knew what they should be set at. I too have a the same Sam's Club batteries (about 3 years old) and wondered what you have yours set at?

    I noticed with the Prostar that 14.4 did cause some bubbling but not much which is why I thought with the new TriStar I'd try it at 14.6 since there is no default.

    Tim
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: 12 volt charge settings...

    There are arguments for setting the charging voltage (absorb) higher. Windsun (our admin from NAWS) points to this guy:
    • For 12 Volt & RV Systems - HandyBob's long discussion and rant is about 99% right on how to make RV and similar 12 volt systems work correctly. One of the few "non NAWS" articles that we recommend.
    Spending too much time at 14.85+ volts is not a good thing... But getting there quickly is OK and then ending the high voltage charge to go to float voltage.

    Somebody else here posted that there where reasons that 13.2 to 13.7 volts or so for float are recommended... There are actually different aging/failures that occur at differing voltages (sulfates crystallizing, positive plate corrosion, etc.). The voltage chosen by the battery mfg. is usually based on a trade-off of various issues.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: 12 volt charge settings...

    Tim;

    I don't use the golf cart batteries personally, but lots of folk around here do. For my system I've found that slightly elevated Float Voltage helps, but that is on some rather disappointing Interstates that will be going to scrap as soon as I can get back to work on fun things. I have not been happy with their performance.
    Previously I used Trojans (and will be returning to them) with 14.8 V Absorb a 13.8 V Float. Upping the system Voltage is the only reason I switched brands; all new batteries, the Interstates were cheaper, now I know why. Plate failure on one in the first year. :grr
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
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    Re: 12 volt charge settings...
    BB. wrote: »
    There are arguments for setting the charging voltage (absorb) higher. Windsun (our admin from NAWS) points to this guy:
    • For 12 Volt & RV Systems - HandyBob's long discussion and rant is about 99% right on how to make RV and similar 12 volt systems work correctly. One of the few "non NAWS" articles that we recommend.
    Spending too much time at 14.85+ volts is not a good thing... But getting there quickly is OK and then ending the high voltage charge to go to float voltage.

    Somebody else here posted that there where reasons that 13.2 to 13.7 volts or so for float are recommended... There are actually different aging/failures that occur at differing voltages (sulfates crystallizing, positive plate corrosion, etc.). The voltage chosen by the battery mfg. is usually based on a trade-off of various issues.

    -Bill


    Well, that was an interesting read. He makes what seems to be some very sensible points.

    I am inclined to go with a higher absorb voltage to try and get the batteries to the float stage faster. I think I've been undercharging my batteries and after reading "Bob's" rant, I'm pretty sure I have been. I've checked my wire sizes against the voltage drop chart and I am very good there, though I think I'll up the wire size from the CC to the batteries. I'm not getting the usage I'd like out of them and I should be getting a bit more, so it's worth a shot. I can always back it down to 14.6 if it seems I'm using too much water, too fast.

    Tim