safe battery charging

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hi, i have 4 6volt 220 amp ,i want to charge them with a magnum inverter, the inverter has the capasity to charge at 100 amps,what is the best charge settings for the controler to be set at is 50 amps a starting amperage idont want to overgas the batterys and add any acid fums to the battery area whitch is painted steel. thanks jim

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: safe battery charging

    Welcome to the forum.

    You're right to not want to use too high a rate as it can do damage to the battery. But there's a bit of missing information here: Voltage?

    With four 6 Volts I assume they're all in series on a 24 Volt system? That would make the battery bank 220 Amp hours @ 24 Volts.
    If so, you ought to try about 22 Amps for a peak charging current. 50 Amps is definitely too high for flooded cell batteries. I wouldn't go higher than 33 Amps on those.

    You are always going to get acid fumes around non-sealed batteries. It usually isn't severe enough to cause much trouble. But it is why we coat battery connections to keep them from corroding.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
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    Re: safe battery charging
    With four 6 Volts I assume they're all in series on a 24 Volt system? That would make the battery bank 220 Amp hours @ 24 Volts.
    If so, you ought to try about 22 Amps for a peak charging current. 50 Amps is definitely too high for flooded cell batteries. I wouldn't go higher than 33 Amps on those.

    He's in a RV, so I will take the position that he has a 440 ah 12 volt system and 50 amps is OK.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: safe battery charging
    vtmaps wrote: »
    He's in a RV, so I will take the position that he has a 440 ah 12 volt system and 50 amps is OK.

    --vtMaps

    Yes it would. Not but what you couldn't have a 24 Volt system in an RV. See why Voltage is important? :D
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: safe battery charging

    not sure how you know he's in an rv.

    the magnum is not a controller, it is an inverter with a charger function capability. it will charge the batteries if utility power or a generator's power is applied to the inverter. if he is in an rv then he will limit himself to having ac hookups so what would be the point of the magnum and the batteries then?

    these are controllers,
    http://www.solar-electric.com/chco.html
    and they usually have pvs feeding power to them.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
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    Re: safe battery charging
    niel wrote: »
    not sure how you know he's in an rv.

    Oops... I don't know. I guess I just assumed because Magnums are very popular in the RV world and the batteries are in a painted steel area. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CATraveler
    CATraveler Solar Expert Posts: 98 ✭✭✭✭
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    Re: safe battery charging

    I'm on my second Magnum ME2012 100A charger/inverter. The first RV mfg had the default charge rate set to 80% for 12V 4x6V 464AH flooded. I didn't consider 80A to high - was I wrong? In my case an hour or so was usually the limit for bulk charging.

    OP, The Magnum has IMHO excellent charging algorithms and is a fully automatic 4 stage charger. Equalization is a manual operation. However understand two cost design tradeoffs that Magnum made:
    1. The maximum charge rate is only available when the AC input to the Magnum is 120V - not the power plug or gen voltage. I would typically get an actual max charge rate of 70-80A. The MS series are a little better from their specs.
    2. The DC amp reading is very inaccurate. It's actually based on the AC input and mine typically reads 20-30A high. So use a battery monitor or the Magnum optional battery monitor (shunt based).
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: safe battery charging

    80 Amps on a 464 Amp hour battery bank is pretty darn high. 17% peak charge rate. If used that high on a regular basis (more time spent at higher current) it would shorten the battery life. But if the batteries aren't taken down low the charge rate would not be that high for very long. It's a balancing act.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: safe battery charging

    ok i figured out jim is referring to the remote as a controller. wrong terminology.

    as to the original question of 50a to a 220ah battery bank, 50a is too high of a charge. i would try to keep the rate below 20% on fla types and you could just watch the temperature and keep the cells properly watered, aka high maintenance. the 30% point on the remote i would recommend to you to reflect about 30a for the charge at a rate of 13.6%.

    that was all assuming the battery bank to be 24v at 220a. in doubling the capacity on a lower 12v battery bank this would allow double the currents for charging as it is a % of the ah capacity which would now be at 440ah at 12v. 60a for charging would represent 60% on the remote and would be a 60a/440ah=13.6% charge rate. 50% on the remote in this case would be 50a and divided into the 440ah capacity it has at 12v is 11.36% and is also very acceptable. this smaller rate won't charge as fast, but would confine the gassing a bit leading to a bit less water loss over time.

    hope this helps.

    sorry about chastising you a bit on the terminology, but that does lead to confusion and possibly wrong answers to you as we want to give you the right information you are looking for.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
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    Re: safe battery charging

    Question, If a battery bank is below the gassing voltage how much current can it really take ?? If there is no temperature rise between 50-80% SOC. Does anyone think 25 to 30% is out of the question ??
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: safe battery charging

    From the Rolls Battery Manual, during bulk they recommend 25% rate of charge to 35% maximum rate of charge during bulk (@20 Hour battery capacity).

    Once in Absorb, a linearly declining rate of charge (under fixed absorb voltage of 2.45 volts per cell @25C/77F) down to ~0.7% rate of charge when in float (~2.3 volts per cell).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: safe battery charging

    bc04,
    there isn't a set voltage that batteries gas at even though much of it is in the final stages of charge. barring high temps i would think in most cases 25% and sometimes 30% can be fed to a battery, but this varies for differing batteries. i would not do this on an everyday normal basis though unless the manufacturer specifically says to do so. trojan i believe does not recommend such a high charge on one of their batteries and i forgot just which it was, but i believe they held it to no more than about 13%. and just because one can site one that is made for high charge rates does not make it the norm as most should be as i stated, of course with some higher and some lower in their charge ability. i, for one, would not sit here and say to anyone to charge any battery with that high opf a charge rate without knowing for sure it can take it and is why the 13% on the top end we often recommend. i should also state that even if a battery can take higher charge rates does not mean it should be the norm for it. bill cited an exception i guess and my agm batteries are also an exception, but we are talking most run of the mill fla types.

    there's much that occurs inside that would not be readily apparent and damages could occur before you can detect the damaging rise in temp. and even plates can buckle and short faster than you can see there's a problem. i was going to make an analogy to a runner, but it could get muddled and difficult for me to make all of the references to the analogy i had in mind.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
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    Re: safe battery charging

    I have a test set of 10 GC2's @ 12 V ( 1100 amp-hr ) that are on their 2nd year using a 250 amp recharge regimen with 3 chargers. They are being pulled to 50% of SOC and brought up to 14.0 V in bulk and absorbed back at the dock on the Inverter Charger (120 amp ) when on shore power for 2 hrs and floated @ 13.4. they are on a Boat with gas driven generator. I have yet to see any difference in them . The reason I am doing this is that gas on the water is $4.49 a gallon and I had a owner willing to cooperate. I like to know if using the higher charge rate is cost effective, if the battery life is shortened, how much will it be. One thing I can't control are the number of re-charges that are done in the 50-80% SOC. I have asked each customer to write them down. I'd like to know the cycle life and time.

    The motivation to try this came from a EV forum.


    "" The most basic rule is that you can charge at any current you like until the battery reaches 2.4 volts per cell at 25 deg. C (77 deg. F). That's the familiar 7.2v per 6v battery, or 14.4v for a 12v battery. Below this voltage, essentially 100% of the current goes into charging the battery, so there is negligible heating or gassing. The batteries won't reach 2.4v per cell until they are about 70-80% charged. Therefore, to charge the quickest, charge with as much current as your charger or AC line allows.""
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: safe battery charging

    nice that you are doing all of this and you bring up aspects of lifecycle that i hadn't even thought of. i would think it to be along the same lines for heavy charging as it would be for heavy discharging and would be a stress that would reduce the lifespan of the battery some. to what degree is questionable as i don't have the answers there.

    i contend that most batteries will take the high charges for a short time period and 2 hours is a short time period. i do question the 14v to reach the absorb stage though, unless once reached you had set a higher voltage for absorb? be cautious as internal battery temps can rise faster than you would be able to discern externally.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
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    Re: safe battery charging

    The way these batteries are used they leave the dock in float, then dropped to 50 % SOC . Then they are recharged back up to about 80%, this is the where cycle life comes into play, out of 1100 amp hrs you only have 330 amp hrs between 50 and 80%. Over a week they could be cycled 10 times or more. Most Generators are using 1.5 to 2 + gallons of gas per hour. It use to take 2-2 1/2 hours to make the charge back to around 80%, I am now doing it in a hour +. There are other reasons to run a generator and you'd always have opportunity charging going on. The goal for me is to see if I cut the gas consumption in half and find out what % did I removed from the cycle life of the batteries. If I can get 500-800 cycles , it's a big time winner, if I shave off a hour per charge cycle and pay for the chargers, the batteries become expendable @ $900 a set. At the end of the 2nd year we are $200 to the good and the chargers are paid for. I'll start back next spring, by the end of next year if we do 150-175 cycles the batteries will be paid for and everything after that is gravy.

    Water consumption has stayed the same, there is no positive post protrusion or case expansion or bulging yet, that's about the only things I know to look for.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: safe battery charging

    I think you are making a very well researched test here... And I think you are getting good results.

    I agree that if the batteries are not getting hot, not bubbling excessively, and not using a lot of extra water--You are probably not damaging them excessively (if at all).

    Given that batteries don't really gas much or generate much heat (and lose charging efficiency/stress plates/etc.) until you get over (roughly) 85-90% SOC, I would believe you are in a good zone for high current charging.

    My only question would be how long the batteries operate well below ~75% SOC where sulphation becomes an issue. If you are quickly recharging them same day/next morning--what more can you ask for.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • highgear
    highgear Registered Users Posts: 2
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    battery charging

    i want to charge 4 6 volt 220 ah batterys, i m using a magnun 2200 inverter, the charger settings go up to 100amp charge my question is what is the best charge rate for these 4 batterys
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
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    Re: battery charging
    highgear wrote: »
    i want to charge 4 6 volt 220 ah batterys, i m using a magnun 2200 inverter, the charger settings go up to 100amp charge my question is what is the best charge rate for these 4 batterys

    Each battery (assuming they are FLA) can comfortably take up to 220 / 8 amps (27.5A) , and should get at least 220 / 10 amps (22A) if possible.

    Will the four batteries be in series to produce a 24 volt bank? If so go for a 25 amp setting.

    If they are in series/parallel to produce 12 volts and 440 AH, then go for 50 amps.
    SMA SB 3000, old BP panels.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: safe battery charging

    highgear,
    do not ask the same question in another thread again. as it is i merged it with your original question and you will find that i answered your question in post #9. i believe that inverter is a 12v modsine making your battery bank 12v at 440ah. i highlighted that portion of my answer there.