Best battery choices for generator only charging?

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  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Audio.....
    I did not trust the chart you posted. I also seen on the place where I bought my battery, Three conflickting advises. gb website. It said every charge was considerred a cycle, it said if you had a low use facility, better to take the battery down to 80% discharge over a few days, then charge. On the same site, it posted a chart and said not to go below 40% dod. It said opertunity charging during lunch was bad. Go to the naws advce page and it says opertunity charging is probly good. Go figure. The result of the study that I quoted as understood by the person presenting it was at a ten percent discharge your batteries may live 3 times longer then taking them to 50% but even though the batteries did not live as long, you got the most kwhs out by not going to 100% charge but every 10 to 14 days and running your battery in the 80% to 50% range. Myself I try to get to 90% most days cause below 80% is where everyone says if your battery is there to long it hard sulfates. I couldn't tell you the right or wrong of it, only that it is supposed to have been one of the only really long studies. Again, I let smarter people then me read and get that out of it.

    I would not discount the experieances of alaska man and love hearing about things like that so I can add to my confusion on trying to figure out what is best among all the conflicting statements. I believe him also and add it to the rest and then try to put it together for myself. There is more then one way to skin a cat it appears. When I hear something like alaskaman presents I try to listen to everything he says so I can find the reason he is succesfull when others have such destructive results trying to do the same. Things like knowing where his batteries really are and making a reutine of charging there and charging on saterday and keeping in flote all day to counter what he has done the previous week.

    It is all a compermize and when you do one thing bad, then you do something good to counter it and hopefully it adds up to something that works.

    It surly works better then my spelling.

    We all pay the piper for what we do and since we are paying, we get to decide what to do. I also want to do it as easy as possible and have it work and untill then I am going to enjoy these discussions and try to gain more toward that end. I would not have the guts to push my stuff too hard cause it hurts me to bad when replacement comes but I still want to try for best use within my conservative nature.

    Good luck.
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?
    Do a test, when I moved to a fast Charge scheme of bulk charging at 25 - 30% of C below gassing level I saved enough $$$ in fuel savings in the first year and a half to pay for the whole battery bank and 3 years later they are still trucking along. I have to say, it's for batteries that are pulled to 50 % dod and have 300-400 amp hrs to be returned.

    I believe you.

    I am now bulking @ 33%

    On my 48v system, I just moved my generator start trigger from 47.6v to 46.6v so I am discharging my batteries further against wisdom.

    That said, in the 20hrs or so since I've made that change, my generator is running half as often and really for about the same duration. It's just staying at a higher amperage in bulk than before.

    Listening to the thing half as often is bliss. I am awaiting the wrath of the battery gods tho to see if my bank goes south in the next two weeks, or if it will just be an acceptable loss of longevity for the benefits.

    Frankly, if I imagined that this little bank would last a year doing it the right way verses 10 months like this, I'll take the quiet and the fuel savings.

    Only time will tell I guess. This bank is *somewhat* disposable for testing since it's small and FLA when I really want 2x and AGM soon.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Audio
    I understand that there are battery charging strategies that are optimum for the battery, less than optimum for the battery, and catastrophic.
    I would also put forth that what is optimum for the battery is less than optimum for the generator in some cases, and also defeats one major purpose of having batteries (silence).

    I still don't understand why you can't have both the optimum battery charging and optimun generator use. You are going to purchase batteries so you don't have co compermize cause you are using things that where not ment to be used with each other. I don't understand setting up a system to purposely go to 80% dod when you can set up a system that will have the same generator concerns taken care of with the battery concerns also being taken care of. A pure dollars and sense solution. The only thing that would stop you from doing this would be as stated earlier, zero room to do so or a pure hate of having to add water to batteries. You haven't bought yet so why not optimize for your intended use?
    Cheers
    gww
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Blackcherry and audio
    I am now bulking @ 33%

    Does it seem like the heat being generated is out of line or is it doing really well?
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?
    gww1 wrote: »
    Audio


    I still don't understand why you can't have both the optimum battery charging and optimun generator use. You are going to purchase batteries so you don't have co compermize cause you are using things that where not ment to be used with each other. I don't understand setting up a system to purposely go to 80% dod when you can set up a system that will have the same generator concerns taken care of with the battery concerns also being taken care of. A pure dollars and sense solution. The only thing that would stop you from doing this would be as stated earlier, zero room to do so or a pure hate of having to add water to batteries. You haven't bought yet so why not optimize for your intended use?
    Cheers
    gww


    I'm sorry gww. You're right, a bigger bank would really help alleviate this problem. My system is mobile and my budget only allows for 200ah @ 48v although I have room to get to 400ah @ 48v.

    With these capacities, getting to where your genset only runs once per day is a pretty big goal. Right now it runs many times per day and I'd like to reduce that cycling.

    It was this condition that led me to be looking at charts showing the reduced lifespan of batteries at deeper DOD, but in that hunt found that the way a batteries' life is presented is kind of murky.

    My system in it's final draft will still be what some people face in smaller "home" systems though... about 10kwh/day.
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?
    gww1 wrote: »
    Blackcherry and audio



    Does it seem like the heat being generated is out of line or is it doing really well?
    gww

    I'm not feeling any heat at all, but I have a Battery Temperature Sensor that reduces the charging current if it gets warm. So far when I've looked at the temp reading it's just above ambient (about 55F in my case).
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Best battery choices for generator only charging?
    gww1 wrote: »
    Blackcherry and audio



    Does it seem like the heat being generated is out of line or is it doing really well?
    gww
    The heat in Bulk is very minimal. Once you pass over into the gassing voltage is where heat becomes a issue. I set my charging sources where I can drop one. Of course in the summer it's much more critical than now.
  • softdownsoftdown Solar Expert Posts: 3,609 ✭✭✭✭
    Re: Best battery choices for generator only charging?

    You can read the massive generator threads or you can just buy a slightly used Honda 2000i for about $600. Many reports of them lasting 3000-6000+ hours with oil changes. There are other good manufacturers but everyone raves about the gas mileage of the Honda 2000i.

    Using a $7500 genset several times a day, during the winter, for battery charging makes my head hurt.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Thank you guys for your answers. I kinda thought that would be the case but it is sure nice to have first hand confermation.
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?
    softdown wrote: »
    Using a $7500 genset several times a day, during the winter, for battery charging makes my head hurt.

    Mine too.

    I'm in an RV though which shares a diesel tank, and that's really not large for a diesel (in fact, my generator is considered one of the most compact).

    There are other considerations like that my system is set up for automatic starting (which requires a starter).

    Frankly, I'm proud of Honda. Making a portable that could last even 3000hrs is amazing. It makes for a very good cost to benefit ratio.

    Still, that is a rarity. $5000+ backup generators are not uncommon.
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Best battery choices for generator only charging?

    I like the Honda eu2000i family... However, while its fuel economy is not bad--It is very good compared to running an 8 kWatt genset to power a 1 kWatt load... That is where a smaller genset really shines--Run it at 50% instead of running a large genset at 12.5%. In theory, an 8 kWatt genset running at 1 kWatt is going to use something like 4x or more fuel (rough guess) for the same load.

    The larger generators will tend to be more fuel efficient (kWH/Gallon)--And there are many good genset options out there.

    For many smaller homes/cabins, a 1,000-1,600-2,000 watt genset is more than enough to run the few loads needed.

    Finding/maintaining these small gensets can be hit or miss.

    And add the inverter stage to the genset--Yes, better fuel economy (and quieter operation) at lower power--But probably somewhat less efficient than a standard generator when running near rated load.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?

    One of the big reasons you find larger kw generators in RV's vs what you might need in a home (per square foot??) is because RV's are generally constructed with thin walls and no attics.

    That means that you will roast in the summer unless you rely heavily on A/C, while the house you're parked next to might be just fine.

    The other reason is that most homes are not fully off grid except for backup or supplemental requirements. In an RV, your max output is all you are going to have today, and tomorrow.

    @ 7400w 240 split, I can do construction projects and welding all day long that most homeowners take the ability to do for granted. Some RV gen's run in the 10kw range which means you can have climate control, weld, charge your bank, and microwave a burrito at the same time.

    That ability doesn't make it the best choice for fuel sipping end-of-times survival living. People who have 10kw generators in their RV are generally more concerned about comfort than efficiency.

    My own experience is that my 7kw diesel gets pretty good fuel economy (.16gph @ 1750w, .32gph @ 3500w, .64gph @ 7000w), and should have a 10-15khr lifespan if treated properly.
    The cost per watt at purchase might not be that great, but they do offer advantages over portable when you are using them as your prime electrical source day in and day out.

    Also keep in mind that generators have been stuck in RV's for many decades, but only recently has solar found it's way atop these things. Even today, most RV designers are still using that genset as the singular source of power....so it's gotta be good.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Audio...
    Getting back to the batteries, One other thing to consider is whether your equipment will even let you take your battery down to eighty pecent discharge. I once tried to take my battery down to about 45 volts. I found that my inverter would kick it off line due to voltage drop under load. I do have some heavy loads and also a forktruck battery which are notorious for voltage drop under load. I now have my low voltage disconnect set at 44.8 and when my batteries go off line my cc will have the low voltage for the day at right at 46 volts. I will look at the battery and it will be setting at anywhere from 48.2 volts to 49.2 volts. The only thing I can think is happening is that the inverter whose range is 44 volts to 65 volts is getting to 44 volts faster then the cc is recording it. I have a well pump that runs at about 2000 watts and I am sure the start surge is much higher then that. It kicks on everytime you flush a toilet. I believe I could take my batteries lower with lower loads but I don't mind ending up aroung 60% soc. I had to manualy keep putting my loads on the battery the one time I tried to take it lower and the lower it got the quicker it disconnected. I think alaskaman uses the same inverter as you so maby not a problim but then again you might have heaver start up loads.

    I also heard inverter efficiancy goes down as the battery is highly discharged but don't know if that is true.

    Aint none of this stuff easy in my opinion.

    I don't know if this has bearing or not but tought I would throw it out there.
    good luck
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?

    Anyway, I'll move away from the DOD question and do some more net research. There's probably some graphs out there to stare at.

    Back to the AGM question... so far 1 response.

    Reading on the net, some AGM sellers advertise as little as 1/5th the time to charge vs flooded batteries (and a deeper allowable DOD by the way).

    Is that real world?

    If the charge currents were similar (I know they're not the same), that would suggest that 4/5ths of the energy required to charge a FLA was *wasted* vs an AGM wouldn't it?

    Even if you were to be more conservative and say that an AGM could recharge in 1/2 of the time, that would still suggest that 1/2 of the current required to charge the same ah FLA was again...wasted energy.

    Generators are a costly way to make kw's. Even with AGM's costing more at purchase, it would almost make it criminal to purchase anything else when regular generator use was involved....no?

    Is it just hype, or could one make that assessment?
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?
    gww1 wrote: »
    Audio...
    Getting back to the batteries, One other thing to consider is whether your equipment will even let you take your battery down to eighty pecent discharge. I once tried to take my battery down to about 45 volts. I found that my inverter would kick it off line due to voltage drop under load. I do have some heavy loads and also a forktruck battery which are notorious for voltage drop under load. I now have my low voltage disconnect set at 44.8 and when my batteries go off line my cc will have the low voltage for the day at right at 46 volts. I will look at the battery and it will be setting at anywhere from 48.2 volts to 49.2 volts. The only thing I can think is happening is that the inverter whose range is 44 volts to 65 volts is getting to 44 volts faster then the cc is recording it. I have a well pump that runs at about 2000 watts and I am sure the start surge is much higher then that. It kicks on everytime you flush a toilet. I believe I could take my batteries lower with lower loads but I don't mind ending up aroung 60% soc. I had to manualy keep putting my loads on the battery the one time I tried to take it lower and the lower it got the quicker it disconnected. I think alaskaman uses the same inverter as you so maby not a problim but then again you might have heaver start up loads.

    I also heard inverter efficiancy goes down as the battery is highly discharged but don't know if that is true.

    Aint none of this stuff easy in my opinion.

    I don't know if this has bearing or not but tought I would throw it out there.
    good luck
    gww

    gww,

    I don't know how low the Xantrex (xw6048 ) will let me drop, but the LBCO (low battery cut out) is defaulted at 46v. I've never tried to set that lower (it might only go up for all I know).
    I need to go back and do my math on the [email protected] for 48v. I originally had my generator starting at 48v (which is around 50% DOD), then I stepped down just a tad to 47.6 which I'm just guessing is about 60% DOD, and now the generator is set to kick in at 46.6v (around 80% DOD). That's still higher than the 46.0 where the inverter would cut out.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Audio...
    I could be wrong and don't mind hearing it. What is in my head when they say "charges faster" means they accept a higher rate of amps while charging. I looked up an agm three days ago and it said a 20% charge rate max, When I talked to my battery maker, they said a 12.5 percent rate would be about the most. I think in the sweet spot during bulk and before gassing voltage that the batteries efficiancys are about the same and close to 1 amp supplied and 1 amp accepted. Where there might be differances but I bet not many, would be the part from 85 to 90% to a full charge. Then you lose a whole bunch. I believe this is explained pretty good in the trimetric battery meter pamplet which has a good reputation as a good meter.

    I don't know if there is much differance at the end or not. I do think overall the ideal is to only do the end enough to protect your batteries and the lower efficiancy there make this prudent as well as a full charge is helpfull and hurtfull at the same time.

    The speed you mention does not in my opinion justifie your conclution of what it means. It doesn't mean that 10 kwh is not 10 kwh. It just means it is ok to make the ten kwh faster. This may or may not add up to more fuel efficiancy, with you equiptment being able to dump large amounts of amps at one time it would probly be helpful. Although myself, I would probly buy more of the cheaper batteries for more capasity and push them a bit with higher charging amps then recomended before buying a lower amp, more expencive battery and pushing it on both ends of a lower discharge and a still high rate of charge. My numbers migtht be off a bit but 30% more cost for battery charged at 20% charge rate or 30% more capasity charged at a 12.5% rate. If we pretend the 20 % is 20 amps and the 12.5% is 12.5 amps and you take the 12.5 amps and add 30% to it you are but 4 amps away from the 20 amp agm. I would push up on the 4 amps to 20 amps cause that ain't that far and the end would probly be better then pushing max and discharging further.

    I think I have the battery charging part correct and I give my use of that imformation opinion for free and I say ha ha while doing so cause I have never used a smily face yet to show I am not to be taken too seriously.
    Good luck
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?

    Well I'll tell ya gww, that advertising I've looked at must be near fraud.

    I read pretty often "AGMs can recharge much faster".

    I'll try to pull the page where it states 5x faster.

    20% of C is nowhere near 5x faster than FLA's.

    Standby...
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Audio...
    I will throw you a bone against flooded batteries. I pay .88 cents a gal for distilled water cause I haven't made a distiller yet.
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?

    Here's one...

    What do they mean "faster"?

    http://batteryuniversity.com/learn/article/absorbent_glass_mat_agm
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Audio
    It is only by accident that this post coinside with me looking up the agm. I didn't have an answer for someone on the outback forum that had her equiptment charging at factory default. I told her to contact her battery maker and get the proper charging for her batteries and she posted the link to "her" batteries. I really don't know what is out there. I do know she only had a 100 ah battery bank and I was afraid if she used the inverter on default that she would fry them cause part of her problim was her previous bank got smoking hot. I looked up the max charge rate on "her" agms.

    I can link the post if you want but it is off subject except for that part.
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?

    This has some more detail, but still not "5x" faster like the first link:

    http://www.powerstream.com/SLA-fast-charge.htm
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    A
    Did you read the comments after the artical of your first posted link? The battery university one.
    gww
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    Re: Best battery choices for generator only charging?
    gww1 wrote: »
    A
    Did you read the comments after the artical of your first posted link? The battery university one.
    gww

    No. Let me guess, they call bs?
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    I didn't see many positive on the artical but most of the bitc... was not totaly about the battery but some was. Have you looked a naws totorial? The marine guys are crazy for them, the solar sites not so much, on site I say said you can charge them at the high rate even though the manufactuer says no. Lots of stuff, what to believe.

    Some say same life but twice the price.
    If I find anything interesting I will post. About 4 years ago a guy on outback forum was going to buy new agms and there is a really long post on that If you want me to post the link. I seen him answer the other day and I think he still has them. The girl I was helping had agms and was replacing them and she got 6 and 1/2 years out of them and mostly sold power to the grid, she used them a total of ten days durring a hurricane.

    I respect crewzers opinion on outback as his post always show common sense if you wanted to pm him for another opinion. I don't remember if he is off grid or not.
    Good luck
    gww
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    Couple of charts here if you are smart enough to read them. My eyes must be blury cause the only thing I caught was that 35 amp charge would charge one in 3.5 hours and an 8d flooded would take 11 hours. which goes to your being more correct then me on what the efficiancy is. So far.

    http://www.dekabatteries.com/assets/base/0139.pdf

    gww
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Best battery choices for generator only charging?

    I don't know if this has bearing on charge rate being more efficiant but is what I quoted from the trimetric manual leading me to think in the 50 to 80% pecent range flooded batteries are pretty efficiant.
    Purpose of data: "charge efficiency factor" See section 6.22, part 4 for an explanation of “charge efficiency factor”.
    Choosing values of "charge efficiency factor": In the “L1” mode this value is fixed at 94%. If you wish to adjust it to
    a different value you will need to switch to “L3” mode. The actual "charge efficiency" factor for lead acid batteries
    while they are not at the top of charge is generally higher than 94%, so this will usually give a conservative value for
    "amp-hours from full"-- that is the meter will generally slightly under-estimate the “% Full” value for the batteries
    which will give a useful practical result for knowing state of charge.
    Optional technical note: Some people familiar with batteries will be surprised that the suggested "efficiency factor" is as high as 94%. Without going
    into all the details here, there are two reasons for this: (1) The number entered in the TriMetric is not true battery efficiency, or energy efficiency,
    (which is often quoted at 70-80% for lead acid batteries) but charge efficiency. Charge efficiency (the ratio of total amp-hours you get out divided
    by total amp-hours to charge the battery) is always greater than energy efficiency. (2) What is entered in the TriMetric is not even the overall charge
    efficiency of the battery, but the charge efficiency while the battery is not at the top of charge, and not gassing. A battery is not charge efficient
    while at the top of charge, so if this part is excluded the battery is very charge efficient. (We have measured this to be 95-98% with Trojan wet cell
    batteries.)
    For the perfectionist only: Practical utility doesn't demand perfection--and the reality of changing battery temperature makes this difficult. But if you
    wish to try and your batteries are fairly constant in temperature: the ideal is that the TriMetric “% full” should show 100% at the time that the
    charging system has fully charged the batteries and the "charged" lamp flashes on the TriMetric, as explained in section 6.-2.-2.) If you find that the
    % reading is somewhat below 100% after the charging system has fully charged your batteries, then you could increase the efficiency factor. If
    you find that the numbers are going above 100% when your charging system has finished charging, then decrease the efficiency factor. But note
    that if the battery temperature went up since the last "full charge" was reached, the "amp-hours" will be somewhat negative the next time reaching
    "charged." And if temperature went down, they'll be somewhat positive.
    gww
  • Alaska ManAlaska Man Solar Expert Posts: 252 ✭✭
    Re: Best battery choices for generator only charging?

    As Far as AGMs charging goes..............

    I charge before work so the Toyo heater can run all day and I don't have to worry about LVD and coming home to a frozen house. When I woke up the Tri-Metric read 88% I started the genny plugged in the chord and put 120Amp into my bank to start. (the Xentrex has a 150Amp charger built in) It quickly went down and 30 minutes later when it was time for me to leave, the charger was pushing about 24Amps into the batteries (amperage fluctuates ) and they were at 94%. I'm not sure how that would all work out if I was using FLA's. Perhaps someone that does use them could tell us how they would do in a similar situation.

    Like you, I also want the biggest bang for my buck. If the FLAs performance was close, I would think hard about the money next time I buy.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Alaska....
    I don't know about my bank taking high charging amps. I have 48 volt, 800 ah bank but the most current I ever put in while watching was about 130 amps. I only have about 90 amp peak charging capability with my solar and when the wind is blowing hard It may add another 10 to 20 amps but it is usually at that high of rate for ten min top and will drop back to 5 amps and then go back up. I do know that I can get to replacing all but about 60 amps at my full charge rate before any cutback and this is above 90 percent charge per the trimetric battery meter (whatever that is worth). Blackcherry charging at 33% charge rate may be able to put this in better perspective then me.
    gww
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