battery charging

TooltimeTooltime Solar Expert Posts: 41 ✭✭
It has been a while since I dropped in, although it has been a rocky start, my off the grid system is running. 8 golf cart batteries, 1000 watts pv, 3000 watt pure sine inverter that is on only when needed, with a 1500 watt modified that is on 24/7, Zantrax 40 charge controller. And I just added a 7500 watt Onan Diesel generator. Looking to add a 800 watt wind turbine and jump the pv to 2700 watts as soon as the budget will allow.

Now the question of the day is, Can I add a second battery charger to speed up the charge time of the batteries when I am on generator? My aims inverter has a 65 amp charger that I am using right now.

Living in west Michigan does not give me a lot of sun during winter months.

Thanks again,
Tom

Comments

  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: battery charging

    You can add as many charging sources as your generator can handle up to the reasonable charge capacity that your battery bank can handle. Getting more than one to cooperate with each other can sometimes be a pain since one may look to the battery voltage to determine what "stage" it should be in and seeing the additional voltage from the other charger can fool it into thinking the batteries are at a charge level higher than they really are. On the rare occasion I need to run my 2 I simply force them both to stay into bulk mode the whole time and that seems to help.

    Also, I do not know a lot about wind turbines other than those inexpensive 800w wind turbines will need something like 35-40mph winds to produce 800w. Look at the POWER CURVE that they publish and you will likely find that at 10-15mph winds you will only get 40-70watts out of it. So my opinion is unless you are in a very windy area with 30+mph winds all the time, better to just spend the money on more solar since it has become so cheap.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • solar_davesolar_dave Solar Expert Posts: 2,342 ✭✭✭✭
    Re: battery charging

    I lived in Grand Rapids for 25 years and don't remember enough wind to make a turbine actually work. Perhaps if you are right on the lake shore dune that may be different but inland the tower cost to get one up high enough to work would be pretty expensive. Last time I was there I did see some VAWT on the Meijer store and was surprise.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: battery charging

    Whoa.
    You can add charge sources to increase the maximum rate of charge up to a point.
    You have eight GC2's at about 220 Amp hours @ 6 Volts each. What is the system Voltage? If it is 12 (like so many of those horrible AIMS inverters) then you have 880 Amp hours. In theory this could take the full 65 Amps output of the charger (7% peak rate). You could use 88 Amps 'ideally' and as much as 176 maximum (but not sustained).

    If the same batteries are configured on a 24 Volt system the 65 Amps becomes almost 15% charge rate and things get dicey because it would be closer to full current more of the time.

    So when you add charge sources you have to combine their maximum current and see how that compares to the battery capacity. You do not want a sustained current over 15% for most batteries as the heat created will shorten their lifespan. (AGM's can take higher current than flooded cells.)
  • TooltimeTooltime Solar Expert Posts: 41 ✭✭
    Re: battery charging

    Who said this was going to be easy? First of all, I am running 24V. So what Cariboocoot, is saying is that I am already at the max? It takes about 8 hours to fully recharge the batteries the way it is. I was hoping to cut that in half.

    As far as wind. In the winter the I see 15 to 20 mph wind a lot. My tower is 100 foot, 120 if i want. I look at it this way, If on average I get 100 watts and hour on a 800 watt unit. I will have to shop the wind turbine market out when I get serious. With maybe 1 hour a day of sunlight along lake Michigan during and jan. even 2700 watts won't be enough. unless I don't understand the math right.

    If I had to buy a tower, that would be out of the question. My goal is to non dependant on the generator. I have a long way to go.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: battery charging

    Your main problem is low sunlight. Even if you put up a massive array and limit the combined current to not exceed battery maximum the panels won't produce without light. Up here where the total daylight shrinks to 6 hours in Winter solar is a no-go on its own because as you have found trying to jam all the power you need for a day into a set of batteries over the course of one or two hours of good daylight just can not work.

    So you have a 440 Amp hour 24 Volt battery bank. If you were to 'max out' the solar on that you'd have an 80 Amp controller and about 2500 Watts of array. All the while it is sunny about half of that would be doing nothing.

    As such it is sensible to want to utilize wind. Here you can go the other way, if you can count on a steady breeze sufficient to produce any real power. Take into account average load current draw and add that to a 5% minimum charge rate. Say it comes to 2 Amps for the loads plus 22 Amps for charging @ 5% or 24 Amps @ 24 Volts: 576 Watts minimum. As such your 800 Watt turbine idea is good, providing the wind can power it at about 75% of its maximum capacity. That will require some careful wind measuring before you buy the turbine, otherwise you're just tossing money away.

    Another thing that should be examined is why does it take your generator and 65 Amps charger 8 hours to replenish the batteries? At that high of a rate they should be brought back up very quickly indeed, unless: A). they are being discharged too deeply; B). there are loads eating up a significant portion of the charge current; C). there is something drastically wrong in the wiring.

    I would start by rechecking the daily load demand and see how it compares to battery capacity (which would be up to 4.8 kW hours AC). Then check all the batteries to see if they are getting fully charged or if there may be a problem with wiring/individual cell.

    My system can recharge 232 Amp hours that have been depleted 50% in about two hours at 25 Amps peak current. Something is amiss if a 65 Amp charger can't raise 440 Amps hours in the same time. Perhaps the inverter-charger is not set right or is defective. Being an AIMS that would not surprise me.
  • NorthGuyNorthGuy Solar Expert Posts: 1,925 ✭✭
    Re: battery charging
    Tooltime wrote: »
    Who said this was going to be easy? First of all, I am running 24V. So what Cariboocoot, is saying is that I am already at the max? It takes about 8 hours to fully recharge the batteries the way it is.

    It is something wrong with this picture. 65A*8H = 520AH, while your battery capacity is 2*220AH = 440AH.
  • solar_davesolar_dave Solar Expert Posts: 2,342 ✭✭✭✭
    Re: battery charging
    NorthGuy wrote: »
    It is something wrong with this picture. 65A*8H = 520AH, while your battery capacity is 2*220AH = 440AH.

    Only thing I could think of is the loads while charging are pretty high, other than that the charge controller is lying.
  • TooltimeTooltime Solar Expert Posts: 41 ✭✭
    Re: battery charging

    OK, I go home tonight and make sure I am getting my 65 amps, I will update as I get check out what you all have asked.

    Tom
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: battery charging
    NorthGuy wrote: »
    It is something wrong with this picture. 65A*8H = 520AH, while your battery capacity is 2*220AH = 440AH.

    I don't see what's wrong... 65 amps is bulk, and I don't think he is pumping 65 amps for 8 hours... some of that 8 hours in absorb. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: battery charging
    vtmaps wrote: »
    I don't see what's wrong... 65 amps is bulk, and I don't think he is pumping 65 amps for 8 hours... some of that 8 hours in absorb. --vtMaps

    With 65 Amps available for Bulk it should not take 8 hours to fully charge 440 Amp hours of battery.
  • NorthGuyNorthGuy Solar Expert Posts: 1,925 ✭✭
    Re: battery charging
    vtmaps wrote: »
    I don't see what's wrong... 65 amps is bulk, and I don't think he is pumping 65 amps for 8 hours... some of that 8 hours in absorb. --vtMaps

    Absorb cannot begin until battery is 20% DoD, which is 88AH. Assuming even tapering and 44AH (10%) wasted for bubbling, absorb will last at most ((88+44)/65)*2 = 4 hours, which leave us with 4 hours of bulk at 65A, which will charge in 260AH, for a total charge of 260+88=348AH, which is 80% DoD discharge for golf batteries.

    This is very optimistic. Most people indicate 2 hour absorb for golf batteries, which, using the same calculation, would require 94% DoD.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: battery charging
    NorthGuy wrote: »
    Absorb cannot begin until battery is 20% DoD, which is 88AH. Assuming even tapering and 44AH (10%) wasted for bubbling, absorb will last at most ((88+44)/65)*2 = 4 hours, which leave us with 4 hours of bulk at 65A, which will charge in 260AH, for a total charge of 260+88=348AH, which is 80% DoD discharge for golf batteries.

    Is it realistic to assume even tapering? I've never actually graphed it out, but it seems that my batteries approach their end amps asymptotically. If I understand your formula correctly, you are assuming that the average charge rate during absorb is 65÷2=32.5 amps for 4 hours.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • NorthGuyNorthGuy Solar Expert Posts: 1,925 ✭✭
    Re: battery charging
    vtmaps wrote: »
    Is it realistic to assume even tapering? I've never actually graphed it out, but it seems that my batteries approach their end amps asymptotically. If I understand your formula correctly, you are assuming that the average charge rate during absorb is 65÷2=32.5 amps for 4 hours.

    This is just a rough estimate. You start from 65A and you end with 9A (or whatever). The line is somewhat concave, but we don't know the exact shape. If you draw a straight line from 65A at the beginning to 0A at the end, it'll be somewhat above the real curve in the beginning and somewhat below it at the end. Overall area under the curve is going to be roughly the same as under the real curve. The straight line is very easy to deal with. The area under the straight line is a right-angled triangle. To calculate the area, you multiply catheta and divide by 2. (65A * 4H)/2 = 130AH.
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: battery charging
    NorthGuy wrote: »
    This is very optimistic. Most people indicate 2 hour absorb for golf batteries, which, using the same calculation, would require 94% DoD.

    Is there any negative to a longer absorb time on GC2 batteries other than perhaps the extra water consumption?
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: battery charging
    jcheil wrote: »
    Is there any negative to a longer absorb time on GC2 batteries other than perhaps the extra water consumption?

    Long absorb times and high absorb voltages cause oxygen to form on the positive plates which causes corrosion. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • TooltimeTooltime Solar Expert Posts: 41 ✭✭
    Re: battery charging

    OK, With all that I know of one thing. I bought and installed an amp meter and now know that I am charging at 30 amps. I also know that I am using 3000 watts a day + or -.
  • TooltimeTooltime Solar Expert Posts: 41 ✭✭
    Re: battery charging

    On that note, I am looking for input on a good battery charger for my 24v system.
  • westbranchwestbranch Solar Expert Posts: 5,140 ✭✭✭✭
    Re: battery charging

    please add a detailed description of your system in the signature line.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • TooltimeTooltime Solar Expert Posts: 41 ✭✭
    Re: battery charging

    Took me a little bit to figure out how to add the signature line
  • TooltimeTooltime Solar Expert Posts: 41 ✭✭
    Re: battery charging
    With 65 Amps available for Bulk it should not take 8 hours to fully charge 440 Amp hours of battery.

    OK, I installed the amp meter and found that I am only charging at 30 amps, The charger is rated at 45 amps, my bad. less the fact that I am using 5 to 10 amps when I am home. Lights, tv, internet.

    Aims is looking into sending me a new controller board for my inverter/charger
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: battery charging
    westbranch wrote: »
    please add a detailed description of your system in the signature line.
    You ought to be able to bulk up with more charger than you need for absorb, that said 24 -48 V chargers are expensive. Your generator is big enough to power it. The Best in my opinion is the IOTA our sponsor sells. In your case the DLS27-40 would be fine. I'd buy the plain one and add the IQ-4 module, it'll give you more options to plug it in if you want 3 stage charging.

    http://www.solar-electric.com/ioen40amp24v.html
  • TooltimeTooltime Solar Expert Posts: 41 ✭✭
    Re: battery charging

    Done, DLS27-40 is ordered and on the way.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: battery charging
    Tooltime wrote: »
    Done, DLS27-40 is ordered and on the way.
    Cool, you should be happy with it, they are bullet proof and will put out their rated output hour after hour, thats whats important on a Generator. What good does it do to have a 70 AMP charger that put's out 50 amps all the time because it over heats.
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: battery charging
    Tooltime wrote: »
    Done, DLS27-40 is ordered and on the way.

    You'll love it. I have the same one. Bulletproof.

    Just remember it requires a dedicated "20-amp" plug (the kind with one of the blades turned sideways).
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
Sign In or Register to comment.