battery charger

alexis.marcilalexis.marcil Registered Users Posts: 11
Hello,

I have a question: I am building my house far from the grid ( 1 miles) so will be going off grid. My garage will be close to the road so it will have power by the utility. Is there a convenient way for me to use the garage like a generator? I mean that when my battery bank was running low and there is no sun, I could put half my batteries in the truck and bring them to the garage to charge them on 240V ( I guess it's faster than 120V right?).

I don't know if it's possible or if I am missing something, I would still have a small generator in case of emergencies but this would allow me to run it only exceptionnaly.

thanks

Alexis

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: battery charger

    i'm confused. is your garage going to be 1 mile from your house?

    technically you could take the batteries to the garage to be charged with a proper ac charger there connected to the grid or even to the generator. lugging is a pain and i think something at the house as you will drain them too far too often and kill the batteries.
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    Assuming you don't mind truck them it would work. I suppose you could build some sort of pallet so you could lift the whole bunch into the back of the truck.

    The reality is it sound like a royal pain with the potential to blow off charging too often because it is too much trouble, and/or accidents from handling batteries so often.

    Consider what it would cost to bring grid power the final mile. Probably not cheap, but in the grand scheme of things, over the time you may live there/resale value it might be more beneficial.

    Tony
  • alexis.marcilalexis.marcil Registered Users Posts: 11
    Re: battery charger

    hello all,

    thanks for your answer. I don't know if I was clear but hauling the batteries would only be exceptionnally. I will be having a 2,5kw pv off grid system for my house and charging the batteries would only be done in november and december from my calculation with pvwatts.

    Yes the garage is a mile from the house. It's because I want a place to use my tools and charge my batteries. Possibly in the next few year, they will also develop a router that can go the distance so I would be able to have a regular internet provider and not work with cellular...I will have another one close to my house also.

    To bring the power to my house would be 42 000$ so that's why I'm going off grid.

    The pallet system you are talkin is exactly what I had in mind. I know it's not ideal but since it would be done only a couple of time per year...

    how long would it be to charge batteries? I know charger are written in amp, but is it amp per hour. I can get 100 amp charger at my local hardware store...

    thanks

    Alexis
  • mike95490mike95490 Solar Expert Posts: 8,463 ✭✭✭✭✭
    Re: battery charger

    For all that hassle, of moving batteries (ever figure out how many tons that is?)
    I'd just get a 5KW genset, and charge them in place. Either the same fuel as your everyday vehicle - so you can siphon as needed, or propane, and just tap your propane tank.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    Just for the sake of argument, the $42K amortized over the life of a 30 year mortgage would be ~ $1400/yr, not counting the cost of capital. 2.5 KW off grid system, might cost what, between $7-10 watt net/net or $17,500-25,000. Couple in at least 2 battery replacements over the same 25 year period and the grid might sound pretty attractive. Additionally, I think the $42k spend on power (which might also bring telephone, cable etc for essentially the same price) not only make the property more valuable, it might actually make it sellable in the future. Selling off grid homesteads not always easy, and many mortgage lenders won't lend on them. (Don't get me wrong, I am not trying to discourage PV and RE, I am just suggesting that having the grid available makes all kinds of things easier, and cheaper).

    Additionally, the 2.5 kw system will yield ~ 5kwh/day on average out the inverter. Most folks would have a hard time living 365 on 2.5 kwhs of power. If you have to increase your Pv/batteries, or you have to run the genny more, the numbers come closer all the time. Jumping to a 5kw system, which wouldn't be out of line would logically come close to doubling the cost, make the grid even more attractive.

    If it were me, I would consider finding out if there was anyway of reducing the utility charge, like doing my own ditching etc.

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 29,697 admin
    Re: battery charger

    The other thing to consider with hauling batteries is how often you really need to do it...

    Basically, the batteries should do most of their operation between ~75-90% of capacity. Going for many days below 75% capacity can cause sulfates to harden on the plates and reduce capacity of the battery bank years earlier...

    And charging that final 10-20% of charging takes time and extra energy (at least it is cheap utility power)--so you may not want to "leave the bank" at the barn for that extended time (2-8 hours or so).

    Sizing a genset (appropriate battery charger and genset to around 50% of capacity) would probably be a better deal. Gensets typically run most efficiently at 50% of rated load or higher. Running at 25% and below for rated load (say 10kW genset and 1kW charger) costs a lot in fuel flow (typically, gensets run at 50% of rated flow when operated at 50% or less of energy output).

    The Honda euX000i line of smaller gensets can be fuel efficient down to 25% load (400 watts on the eu2000i is 15 hours on ~1.1 gallons of fuel)--so perhaps even a small genset for battery charging may be the ticket.

    But--as Tony suggests, see what you can do to run the power up to your home. It may give you more options (Hybrid GT/Off-Grid power, etc.).

    Perhaps, rather than run 200 amp service up to the home, a smaller service for charging the batteries would be "good enough" on your own dime (costs of trenching vs wire and transformers etc. may suggest the optimum solution of time/labor vs material).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    If you've got 240 split phase service to the garage, is there any technical reason one couldn't transform that 240 back to some higher voltage, send it up your own private ditch the mile, restore it back to 240 at the house. I have no idea if this is possible or even legal. I assume that the utility won't allow HV service, with CT metering at the transformer, allowing you to send your own private HV to a private transformer. I've seen it on industrial sites, but never a residential site. Even then knowing who owned what wire was complicated to say the least.

    T
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: battery charger

    as i tried to say, it is too much of a hassle to lug those batteries to the garage, even though you can, and could lead to skipping some charges needed and taking a toll on the battery life as a consequence. a generator charging supplementally is an answer, as i also stated, and i'd prefer this to lugging batteries although it will be noisier than one may like. never use a genny for just routine top offs, but allow it to bulk charge and let solar top it off. this allows lower run times on the genny.

    as to a choice between pv and utility power if i had $42,000 to spend either way, i'd chose pv as i won't get further bills for every kwh once pv is installed. i'd only need maintenance and allow for some possible battery and equipment failures some time down the line.
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    I understand factoring in any increase in the future cost of energy and building a hedge against it.

    That said, limited output and limited life span of batteries add an element of headache and cost that is difficult to quantify. If one can truly live within the limitations of a ~2.5 kw system than by all means it might make sense. I endeavor to at least have people go into situations (that are in and of themselves expensive) with their eyes open.

    Tony

    PS I wouldn't count on trucking the batteries back and forth as that is a recipe for trouble if you ask me.
  • alexis.marcilalexis.marcil Registered Users Posts: 11
    Re: battery charger

    thanks for the response, I can forget the idea of hauling the battery.

    for the rest, my pvwatt calculation tells me I will have 7.5kw average per day with my 2.5kw system and from my calculation, I will use 6kw per day with wood heating and propane cooking and solar/propane water heating.

    I just can't agree to pay 42K for the utility. They want to cut 40feet large road to bring the utility and the post are ugly. I plan on dying in this house so resale value is not important. In 50 years, if I want to sell, I will just bring the utility then, if the RE technology is not advanced enough to make it more simple and affordable...

    thanks

    Alexis
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    Make sure you are running the PV watts calculation INTO a battery. Battery based systems run 53% efficient compared to +90%for a grid tie.

    Without running the numbers, I would be surprised if you were to get ~7.5 kwh out of a 2.5 kw system in to a battery bank, and then out of an inverter.

    2.5X.53X4hours=5.3 kwh
    2.5X.53X6hours=7.95 kwh

    Tony
  • alexis.marcilalexis.marcil Registered Users Posts: 11
    Re: battery charger

    thank you icarus,

    it's the first time I read that so it's good to know that battery based system aren't as efficient as grid tied systems, I will have to do my calcs again!

    Is there a way to better the efficiency of the battery based system?
  • BB.BB. Super Moderators, Administrators Posts: 29,697 admin
    Re: battery charger

    Efficiency in a battery based system is just an improvements of a few percent here and there...

    For example, a good quality MPPT charge controller can be upwards of 96% efficient, and in cool weather can collect some 15% more power vs a PWM charge controller.

    To get cool arrays, mount them 5-6"+ off the roof to allow for air circulation or mount them on mounts in an open field to get more air circulation which cools the panels and gives you another few percent more power.

    Mounting the array on a solar tracker (1 or 2 axis) can gather more power.

    Mount on an adjustable rack and tilting near vertical can shed snow better. Mount with some tilt so that panels are self cleaning (don't mount flat).

    Use AGM batteries--They tend to be 90% efficient vs flooded cell batteries which tend to be 80% efficient.

    Use your solar/generator power during the day... If you use the power directly (running a washing machine, tools, etc.), the power does not go through the battery--so less losses. If you are using a genset to recharge, using the AC power directly instead of charging battery bank to inverter to AC device saves losses there too.

    Use your AC generator in the morning to bring the battery to 80-90% state of charge--and let the solar system bring it back up the last 10% or so.

    Generators are typically more efficient if operated at 50-100% of rated load. Generators use fuel at ~50% of full power full flow at 50% loads or less. Size gensets to the load. Running a generator at 10% load uses roughly the same amount of fuel as running a 50% load. So, plan you genset loads so that you keep it loaded while running (such as bulk charging your battery bank to 80-90% full using full current of the battery charger), use heavy loads while generator is already running (coffee maker in morning, pumping water, vacuuming, etc.).

    Size your inverters to your loads... For example, use a small 300 watt True Sine Wave inverter for your computer, cell phone charger, small TV, radio, a few CFL lights, etc. Run a second larger inverter only when you use power tools, microwave, etc. Larger inverters tend to have higher losses, especially when only operating light loads vs its rated capacity.

    True Sine Wave inverters vs Modified Sine Wave inverters... TSW inverters are way more expensive than MSW types. However, when running inductive loads (motors, pumps, fridge, etc.), a TSW inverter is more efficient. The Modified Square Wave of the MSW inverter can cause up to 20% additional losses in motors (and some other) devices (added heat loss in devices can cause reduced life in some devices too).

    Looking at your loads and possibly using less electricity. Obviously, conservation is job #1 for off grid homes. But, you can also look at your loads and decide which are worth running on battery/AC vs alternate power... For example, propane vs solar PV powered refrigerator.

    Typically, propane is the batter choice if you are their less than 9 months of the year (weekend summer cabin, etc.). Propane is only consumed when you are there. Solar, because you can only store ~3 days of useful power, is lost/wasted if it is not used. So, if you are there only on weekends, using alternative sources of power for larger loads (fridge, well pumps, etc.) maybe better served with a fuel efficient genset.

    A major cost for off-grid solar is batteries... And AGM batteries probably cost 2x that of flooded cell. And they have a limited life time. Read battery FAQ's, like this one:

    Deep Cycle Battery FAQ

    To make sure your batteries last a long time (closer to 10 years vs 3-4 years). Towards that end, I always recommend some sort of Battery Monitor to help keep track of battery capacity. Especially helpful for spouses, kids, and visitors... Tell them to 1. cut power use if less than 75% State of Charge, and 2. turn on the generator if less than 50% State of Charge... No explaining voltages and specific gravity issues. The first time you don't kill your batteries from over discharging/deficit charging--the meter will have paid for itself.

    Remember that your Off-Grid electricity is probably costing you $1-$2+ per kWhr (10x that of utility power). Evaluate your electrical needs based on those costs.

    To help manage electrical uses, besides the Battery Monitor... There is the Kill-A-Watt meter (useful for off-grid and on-grid use for conservation). If you have a lot of (low wattage) DC power usage, take a look at getting a Amp*Hour / Watt*Hour meter for DC battery systems to evaluate those DC loads too.

    Anyway--those are thing things I can think of off-hand.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    Just to clarify a couple of things that Bill says that are correct, but might be confusing. When he speaks about an MPPT controller ~96% efficient, that is correct. But what is important to realize is that is not system efficiency, just charge controller ef. In other words, a good controller will pass ~96% of the power through the controller to the battery.

    In order, (and I'm sure I will miss some), here are some system loses. Wiring from PV to controller, greater loses with distance and with lower voltage systems. Charge controller loses, as mentioned above, wiring loses between charge controller and battery.

    The big one is basic battery charging efficiency. In simple terms, it takes ~120 amp hours of charge to replace 100 ah of draw,, a 20% loss. There is nothing you can do to limit that. Additionally, with any battery based system, controlling charge more often than not will invloved "wasting" Pv capacity because as the batteries near full charge, they can't use all the PV capacity. (The single biggest reason why Grid tie PV beats battery based hands down in terms of efficiency).

    Next, you have wiring loses between the battery and the inverter. Finally you then have inverter efficiency.

    The net/net is that I like to figure that the net system efficiency of ~50%. I think there are others that use a figure of ~53%. I like 50% just because the numbers are easy to calculate. Can you make small changes across the system? Sure. Can you make the system 90% efficient? No way. I suspect if you got to 60% it would be a huge help.

    My quick and easy formula is this take the nameplate rating of the PV, divide by 2 ro take in the system loses, multiply that number by 4 which is the average hours of (good) sun one can expect. Leaving a number to start your figuring from.

    I have two rules of PV that have been born out from experience. First, people always have their loads grow with time, and the second is that people over estimate how much sun they really get.

    Tony

    PS A note on the "4 hour" rule. Folks will say, "My roof gets sun all day, so I can figure 7 hours, from sun up to sun down" The reality is by the time you take into account fixed array time of day positioning, clouds, haze, fog, dust in the air, etc, etc, the reality is 4 hours might be optimistic.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: battery charger

    and i'll add to tony's comments that you can do something about these losses and it is something that should be gone over in the beginning of your pv plans. larger wires can better overcome losses. agm batteries can have a charge efficiency around 90%. get an efficient charge controller and many quality ccs are far into the 90%+ range and set the pv input and output voltages to keep within the high charge efficiency range. inverters too list efficiencies, but often for a certain select high rate. even idle losses can be minimized with some features that some inverters have. careful selection of the inverter for one's loads are in order as smaller loads often decrease efficiency with also weighing in the other power saving features it may have. mileage may vary here and thus your working efficiency.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: battery charger
    Yes the garage is a mile from the house. It's because I want a place to use my tools and charge my batteries. Possibly in the next few year, they will also develop a router that can go the distance so I would be able to have a regular internet provider and not work with cellular...I will have another one close to my house also.

    As for the batteries - put them on a trailer with a quick disconnect. Drag the trailer down to the garage when needed. But a generator is better.


    As for the internet - if you can get internet to the garage then that last mile is not hard to do now.

    Two of these 400mw units with external antenna connections and PoE:

    http://www.netgate.com/product_info.php?cPath=31_61&products_id=564

    And a couple of good high gain directional antennae:

    http://www.l-com.com/item.aspx?id=22448

    And you can shoot a point-to-point link a mile if you have a decent line of sight.
  • alexis.marcilalexis.marcil Registered Users Posts: 11
    Re: battery charger

    again, thanks for the answer

    I've abandonned the idea of hauling the batteries...

    Could I run some kind of loooooooooooooong extension from my garage to my house. Something that would bring 15a 120v of electricity to the house and would be constantly charging my batteries? If something like that would be 1-2K of wire and I do the trench myself...

    thanks

    Alexis
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    Please re-read post number 8. I discuss that very idea.

    Tony
  • alexis.marcilalexis.marcil Registered Users Posts: 11
    Re: battery charger

    icarus, I will be checking on your suggestion tonight, I called an electrician to get a quote. The problem is that I will need two transformers if I want higher voltage and I am affraid the cost will be too important.

    My question was really about keeping the current in 240v and getting a large wire to my house. I know that if there is too much current drop, it can be bad for an electrical device but for charging a battery, i don't see why I would do a difference other than longer charging time... In wouldn't mind investing 2-3K in that wire if it would allow me to have a constant 15a supply to my battery bank.

    am i missing something, or would that keep my batteries always 100% charge ( almost) 15a X 240V=3600W charging capacity... even with 10 or 20% lost, it still amount to a lot. I could even downsize my pv array to 2kw.

    please bear in mind that I am a beginner, I read everything I can but still... I might not understanding it fully

    thanks

    Alexis
  • BB.BB. Super Moderators, Administrators Posts: 29,697 admin
    Re: battery charger

    Regarding how much power you will need...

    Remember that you have 24 hours to make good on the energy taken from the batteries during bad weather.

    Say you use 8 kWhrs per day (240 kWhrs per month)... And that your battery charger and batteries and inverter are 80%*80%*85%=0.54-efficient.
    • 8,000 Watt Hours per day * 1/24hours * 1/0.54 eff = 617 watts (5 amps # 120 VAC)
    So, you don't need a whole lot of power for backup. Notice that you still have about 50% losses just in the power conversion... So local solar panels and possible generator backup/use for unusual power usage (pumping, arc welding, construction, etc.) may still make economic sense even if you use your "trickle charge" AC branch circuit.

    Step up / Step down Transformers have losses too... Perhaps you can only switch them on for bad weather/heavy power usage (remote control?).

    Perhaps a local electrician or somebody here can discuss the implications of step-up/step-down transformers to drive a mile of line.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    Use the wiring loss calculator somewhere on this site. I did a calc on an off site calculator using #1 awg wire, 5280' 30 amp load, 240 vac and it gave me ~ 190 vac at the end.

    Now interestingly enough, if you run #6 wire you will get essential no voltage at the end, but if you ran #4 you would get ~140vac. Now I suppose that you could start with the 240, and end up near 120 vac, use it as 120 and it might work fine. ( I would run this by someone who knows however). The result how ever, would be that for every KWH you pay for you would only be getting 500wh worth of work out of it, effectively doubling your power cost. (not to mention the cost of the wire!) Might be cheaper than your PV power however.

    Personally, I still would consider grid power to the building, or at very least transformed HV at the beginning and end.

    Tony
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    Your 15 amp desire at the end, would yield a max of ~1800 watts @120vac. Delivering this to a 12 volt charger would deliver a max of maybe 90 amps into a 12vdc battery bank, 45 into 24 vdc or ~22 into 48 vdc, by the time you factor in power factor.

    Tony
  • alexis.marcilalexis.marcil Registered Users Posts: 11
    Re: battery charger

    all right, I have a meeting with an electrician at 8:00...

    in the meantime, I played with the voltage calculator and calculated my distance more accurately...

    I have about 1800ft from the garage to the house. If i use #8 wire wich cost about 1$/ft, I can have 5amp at 240v of continuous power and still being in the 5% maximum voltage drop recommended.

    now is there a way to bypass the batteries during the day and use the power directly from the wire?

    thanks

    Alexis
  • icarusicarus Solar Expert Posts: 5,345 ✭✭✭✭
    Re: battery charger

    The short answer is you can do anything you wish to do with the power once it gets to the house.

    But at 1800' it begs the original question,, why is it so expensive to run utility power upt there? It seems if you are going to do the ditch, and they need to set a transformer anyway, running 1800' of utility HV conductor shouldn't be that expensive. I did a google search just for grins, and the average price to extend grid power nationally runs between $20-80,000 per mile. At ~1/3 of a mile that should be ~$7500-30,000. This of course depends on terrain etc. Underground, in your ditch, I just don't see how they get $40K+ to do it.

    I would look into whether or not you could run private HV up the house from a CT meter at the last utility pole. Assuming the utility fuses it, I don't see a reason why they wouldn't do it, except it is not what is normally done, and then stepping down from HV to 240 split phase is going to be expensive on your end.
  • alexis.marcilalexis.marcil Registered Users Posts: 11
    Re: battery charger

    this is my update,

    I finally managed to get a submission from an electrician. It was hard cause it seems not a lot of them are comfortable and willing to do this kind of job,

    so for 1800 feet of underground cable, the telephone cable, two transformer, 3 pole all of this installed will cost 18K taxe included.

    So I will hook up to the utilities for 18K instead of the 42K they were asking me... it pays to shop around

    thanks everybody for your advice

    Alexis
  • BB.BB. Super Moderators, Administrators Posts: 29,697 admin
    Re: battery charger

    Sounds down right reasonable-after the first scary high estimate.

    Congratulations!
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: battery charger

    Jumping in late here (long swim meet weekend), but we did exactly this when we were building our last house. I had our two SW2512 inverters and battery bank at the site. They wanted close to $1000 to run a temporary feed for construction so I ran a line from my parents about 1200 feet away. I didn't think it would start a motor, I did try our air compressor, no luck starting it on the cord itself. I then used an iota charger feeding the batteries and let the inverters do their thing. They could start compressors, table saws just fine and the charger pretty much kept up. Once in a while the batteries would drop to maybe 95% when they were doing a lot of cutting and compressor running, then once they stopped the iota would catch back up.

    I would suggest something like #8 or #6 at 240v and at the "house" end put two iota chargers on the 240 (120 on each side) and connect them to your battery bank and your good to go. The iota chargers will run fine down to about 90v and then the output falls off after that. Your inverter will do the regulating and balance out on the load.

    Never mind it looks like you found a better solution.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: battery charger

    dwh, I understand you delema; when I purchaced my property pacificorp wanted $37,000+ to run 1/2 mile overhead + I had to purchace an additional 30' of right of way from my neighbors and clear it. Then to boot the wouldn't bring it in because I lived in a trailer and wouldn't use enough!?
    Last year had them look again, $27,000+ undreground. I dug the trench, bought the conduit, 5-4x4' concrete vaults, glued the conduit and covered, and bought the transformer.
    I went with $30,000 of off grid system. Just added $4,000 more pv + charge controller.
    Now when "the grid" goes down, I call up my friends and say "outage? what outage? still power here!", Priceless!
    By the way; Telephone was $0.17/ft and they did everything! $2,500 Total

    A wirless router with an outside antenna and 1 repeater should get you a mile with no problem. Only need 1/2 mile of small wire to power the repeater!? LOL
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