Qs on buying battery systems for High Discharge rates

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Tom_G
Tom_G Registered Users Posts: 5
Hello,

(Skip if you'd like)
I am an Ornithographer in Ireland, across the pond, and would like to add a Wind battery tied system to an observation outpost on Sliabh Luachra, a fairly barren hilly range here in Ireland.
I'm, of course, new here and before posting I did try and search for terms related to my question but to no avail, like C.C.A etc.

Please correct me wherever I go wrong here:
While trying to get a bearing on all the information out there when sizing a deep cycle battery system, I began down, what I thought was, an intuitive path to calculating roughly what Amp hour and Voltage system I'd need.

As a 1000 Watt load for 1hr is to be powered, and a Deep cycle battery shouldn't be discharged beyond about 50% of its total capacity, I need a battery that at 100% of the Depth of Discharge should be able to support a 1000 Watt load for 2 hours.

This I thought meant I needed at least, a 12V 200 Ah battery, or pack.
(12V)(200A)=2400 Watt capacity battery, double my needs, Perfect!

Now this is probably where I've made a mistake but bear with me.
So off I went looking for battery packs in this range and they're roughly around $500 which was just within our starting budget. All is working out well I thought!
So I began to search around for batteries, and came to the conclusion that two 'Trojan SCS200 9920055' 12V 115aH batteries would fit our needs.

After I saw this battery, I thought that would also work nicely!
12 Volt 200 Amp Hour AGM Battery 8A4D
However upon beginning to look at this battery for sale I began to notice terms like C.C.A and C.A, Capacity at C/100 etc. and became increasing worried about my battery Ah sizing, do some battery companies display the 30 second Cold crank amperage as the Ah rating? or is it always the 20 hr Ah rating as the Surette/Rolls pdf file below depicts?

I get the feeling that my battery 'Ah' rating needs to be at least 400 Ah to have any hopes of powering the 1 kW load for 1 hour each day, and have a battery life worth the investment/a depth of discharge of 50% or higher, restrained by my budget.
I've come to the conclusion that at least a 400 Ah rating is needed after looking at this Surette Rolls pdf
a '410 Ah' 6V battery with a 1 hour capability of 220 Ah, nicely shown in the graph

So what do the experts say, what are your recommendations for the battery system for the outpost, considering the Load and the approximate 1 hour of draw?

The crux of my question being, given a 12V '20hr 400 Ah' battery(which, I think, only pumps out 20 amps per hour during that 20hrs?) is powering a load of 1000 Watts requiring the battery to pump out ~85 amps per hour P=IV (1000W/12V), how long will the battery last? How long can it last in a given specified time? In my case 1 hour, is there a formula or is it all empirical? Have I oversized the 'Ah' rating I need, or will 200 Ah be sufficient?

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    Top o' the morning to you! Ireland is one of the most beautiful countries in the world! :D

    Batteries, on the other hand, are not beautiful. At least not the specs. There's a lot of different data, and usually the data presented represents the intended application of the battery. But not always.

    If you see terms like "Cold Cranking Amps" you're looking at a starting or automotive battery, which is designed to accommodate short, high Amperage draws. Not really suitable for Renewable Energy applications.

    In RE use you're looking for the "20 hour" Amp hour rating. There are other "XX hour" Amp hour ratings, but the 20 is sort of a standard for comparing and calculating. A Trojan T105, for example, has a 20 hour rating of 225 Amp hours. It and other "golf cart" batteries like it are sort of the default basic battery. It's 6 Volt, so you'd put two in series to get 12 Volts. On your side of the pond it may have a different model designation.

    You're correct about the maximum Depth Of Discharge wanting to be limited to 50% or less. So from a 225 Amp hour battery you wouldn't expect to use more than 100 Amp hours @ 12 Volts = 1200 Watt hours. The less you discharge the battery per cycle, the longer it will last. 25% DOD is a wonderful thing if you can manage it.

    Now I'll make it worse for you. Sorry.
    Your intended load of 1000 Watts is pretty big for a 12 Volt system. At the nominal Voltage it will draw 83+ Amps. But system Voltages don't stay nominal. The default shut-down for an inverter is 10.5 Volts, because at that point the battery is dead. You'd be drawing 95+ Amps at that point. This is fairly heavy current for continuous use. This is where problems develop with wire sizing and connectors. A slight bit of corrosion and the resistance goes up. You might want to consider upping your system Voltage to 24, if possible.

    Others may have different opinions on this.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    hi tom and welcome.
    i am doing my 2nd attempt as i was starting to confuse myself with the long first one so i'll take a more simplified approach.

    to put it simply, a battery that can discharge so many ah over the usual specified 20hrs will not be as efficient doing the same power in a lesser time. it's the peukert effect if you'd like to find other threads or research on it. this is why you see different ah for different time periods and in your 400ah example you are correct that it is rated to give 20a over 20hrs. you can't just make that same bank deliver 40a over 10hrs as it will not do it. either reduce the time or the load or both would be necessary there.

    let's convert the 1000w to amps firstly. 1000w/12v=83.3a. now doing this over a 1hr period of time it becomes 83.3ah. so you'd think ok let's get a battery rated for 83.3ah then right?

    no. the time is over the period of an hour and a battery will need to be rated probably in the area of 100ah to do that due to the inefficiency. so you'd say get a 100ah battery, right?

    no as this is 100% discharging the battery, which you don't want to do so now we'll figure we didn't want this to go below 50% dod so we can over simplify this and just call it roughly 100ah x 2 or about 200ah. done?

    not quite as the battery can deliver the power, but the voltage will dip and trip the low voltage disconnect or cutoff so at least doubling that again is recommended just to keep the voltage semi usable for some time that you'd want for an hour. this is extreme discharging that drops the voltage very low otherwise i'd have told you to stop at the 200ah battery. now 300ah may work, but that's questionable and i can't say for sure. i have a 1kva inverter and i elected to go with about 400ah in batteries. i don't ever intend to drain it in an hour or go with full power so i can't say what my voltage drop would be, but my batteries are agm batteries just as the mk battery you sited is.

    i'll stop here and hopefully you understand this as it can get confusing.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    If you click on the item "AGM Brochure" in the table, you will get to a PDF and on page 2, look up your battery type, over on the right side of the table you will find the amps delivered for 60 minutes. 115A

    http://www.mkbattery.com/content_container.php?page=downloads-and-technical-reference

    HTH;)
     
    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
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Qs on buying battery systems for High Discharge rates

    That sounds like a pretty large load for a "small" battery system...

    AGM type would probably be a much better fit for you -- if you need to keep the physical size of the bank small... AGM's are very good at providing very high current relative to battery capacity (low "Peukert" factor). Your loading you are looking at is the C/2 discharge rate (to much current for a 200 AH flooded cell battery bank).

    Assuming that a 200-300 AH AGM is your choice (and the life may not be that great--500 to 1,000 cycles?) and it meets the needs of your loads--How are you going to recharge it?

    You asked about Wind--That tends to be highly variable and seasonal in most locations. And Solar is may not be a good fit for your area either (seasons, marine layer, etc.--Solar panels do need lots of direct sunlight to provide good output).

    So--What about a Honda eu2000i (1,600 watt continous--at least at 120 VAC 60 Hz North American units) or equivalent? Roughly your 1,000 watt load for 1 hour per day would be around 1 liter of petrol per day and change the oil once every 25 days.

    They are very quiet...

    Do you think you have enough sun (recommended) or wind (are the trees "flagging" from prevailing wind and can you put up a 20 meter tall tower at least 100 meters from obstructions?

    I am not a big fan of small wind--Even good turbines need a good site and maintenance to keep them running.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom_G
    Tom_G Registered Users Posts: 5
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    Re: Qs on buying battery systems for High Discharge rates

    Thanks everyone for the speedy replies, Especially Niel for the pointer on the Peukert effect, and the well layed out reply, which was most helpful!

    I was probably going to go with one of the combinations below, but since I don't live in the USA, and shipping costs would tend to be fairly high for even AGM batteries, I would be very lucky if anyone knew of an Irish Company that acts as a distributor for some of the large manufacturers? or to cut down on shipping, a European supplier?

    There doesn't seem to be any singular unit 12V 400Ah battery out there for sale, parallel wiring two 200 Ah batteries may be more cost effective, or perhaps those with experience would recommend series wiring two six volts instead?
    Maybe even a bank of series wired 2V batteries may come out as the best solution for our needs, for their lighter weight, but I'd like to hear everyones views on that, and any experience you've had with them?

    There are some nice 6V Rolls batteries here in the 400 Ah range that might work well series wired
    Two 6V Surrette S6-460 Rolls 212 Ah for 1 hr, series wired, would give us the desired less than 50% discharge, price $958 for both, I hope these are Absorptive Glass Mat!

    Two AGM 12V Concorde Sun xtender 165 Ah at 1hr rated battery, there's no price listed though

    Two 12 V 245 Ah at 20 hrs MK AGM, The PDF provided by Westbranch(Sonas ort) has this rated at 151 Ah at 1 hr, price $592 each

    Two 12V 250Ah at 20 hrs AGM battery. $569 each

    So what do you all think of that selection, The Rolls Surrette S6-460 seems to be the best value?

    Is there no other way but to go to the $1000 mark for what is required?

    Cariboocoot, 'Top O' the morning to you' shush the leprauchauns might hear you! agus cuid eile an lae leat féin!
    Your suggestion to up the system to 24V is wise indeed, but the reason I began with 12V is that inverters and Chargers may be cheaper and more available in the 12V rating, but maybe this is a misguided belief? I am new to this!

    BB You bring up a good point about charging, and battery life! That is definitely on the list for me in researching this, Since Sliabh Luachra is ~1000ft above sea level, and is quite barren, with very little Sun (Ireland gets around 300 days a year of overcast unfortunately) another member of our club is looking into wind turbines and positioning one near the crest of a hill a fair distance away, someone even mentioned a Microwace Rectenna for beaming power to the cabin!

    A backup generator like the Honda eu2000i would come in handy all right! but as petrol/gas prices here in Éire hover around E 1.5 a liter or $8.2 a US Gallon it's Loco! We're also trying to be less dependant on petrofuels for the sake of the Glen.
    Another more down to earth member is looking into a 'woodgas' powered generator system, and as I'm led to believe, woodgas can be ignited in a IC engine like petrol/gas it might prove cost effective to buy a petrol generator and use woodgas to power it.

    In the mean time however it is mains charging that will be used and transportation by Horse as there are no roads where the cabin is.

    Generators, turbines and cars have a bad habit of scaring the Birds!
  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
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    Re: Qs on buying battery systems for High Discharge rates
    powering the 1 kW load for 1 hour each day,

    Please describe your loads (type & W/VA) and usage patterns, 1kw for one hour or 1 kw spread over the day makes a lot of difference to design.

    Have a good one
    Tim

    ps MOD`s please delete if out of order, wrong side of the pond for you so I am presuming not.

    If you can not find locally / in stock, http://www.barden-ukshop.com/
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    Hi Tom_G,

    Another option for deep cycle and high Amp batteries are forklift batts. There should be many suppliers in Ireland that can source them. They come with differing number of plates to provide different instantaneous Amps out, for the same given Ah capacity rating, e.g. a battery model of "7 PzS 300" means it has 7 plates and 300Ah (usually at C5). Generally, the more plates the more instantaneous Amps it can deliver. So the very same 300Ah capacity might also be provided by a "3 PzS 300", which only has 3 plates, but they're thicker and still provide 300Ah, but fewer instantaneous Amps.

    A distributor will be able to give you advice as to the most appropriate cell type, popular manufacturers in Europe are: Hawker, Hoppecke, Sunlight, Tudor, TAB.

    Going to 24V does not increase the cost of inverters/chargers, and it will in fact decrease your cabling costs because they don't need to carry so much current. The Victron Multiplus range are excellent value and high quality inverters with built in chargers - very popular with European installers and particularly the marine world. If you search for "victron energy" you'll find their site and under "information" they have their retail price list.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    What will be recharging the batteries ? Solar ? Wind ? generator ?

    I hate to throw another option in, but also consider a bank of 6V golf cart batteries, wired in series, for 48V. That will reduce the amp load of the batteries down quite a bit, and the batteries are much more common (less expensive) than the more exotic types.
    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 ,

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    "In the mean time however it is mains charging that will be used and transportation by Horse as there are no roads where the cabin is."

    ouch, this is going to cost you anyway in lugging heavy batteries back and forth, not to mention give you a hernia. forklift batteries just about would need a forklift too. it may be good to have say 4 12v 100ah batteries paralleled, but there's nothing wrong with series/parallel or just series to come up with the current you'd want. you don't seem to have many options, but multiple batteries will spread out the weight to allow moving them a tad easier.

    i don't know of many european dealers except for nightomdaw who is a member here on this forum and is a british expatriot living in spain. (hope i said that right.) stephendv may also know of some dealers. most dealers, i would guess, would still pay the high shipping and just pass it on to you. you could call our host northern arizona wind and sun and get a quote from them on various battery combos with shipping just for a comparison.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    Tom;

    It may look like you're getting conflicting or at least divergent info here. Really we're all saying the same thing: a continuous draw of 1000 Watts on a 12 Volt system is high. Yes, it's the Peukert effect. Mike has suggested 48 Volt. I suggest 24 Volt. My reasoning being it's a good compromise between the barely adequate 12 Volt and the possibly too difficult 48 Volt. :D If you need separate battery charger, you can put two 12 Volt standard chargers on (some inverters have built-in chargers).

    I know they have golf courses in Ireland, so the standard "golf cart" type battery should be obtainable for a reasonable amount of money. With four of them you could have either 12 Volt @ 400 Amp hour or 24 Volt @ 200 Amp hour (same over-all power). And they are not unreasonably heavy. It's a good idea not to spend too much money on a first set of batteries because of the greater likelihood of something going wrong before you get all the details worked out. No sense killing expensive batteries to begin with.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Qs on buying battery systems for High Discharge rates

    Everyone,

    Posting commercial links in response to questions asked is never an issue.

    The only time we "moderators" get picky is a first time poster creating a new thread (or answering a question never asked) with commercial links (aka spamming).

    Tom_G,

    One thing we always go back to is conservation... Is the 1,000 watt load the least amount of energy that you can use? Frequently it is less expensive over time to reduce energy usage vs throwing more wind/panels/batteries/generator at the problem.

    I understand the fuel cost issues. The Honda, Yamaha, and some other smaller gensets can be extremely quiet and should not bother the wildlife.

    Can you get low tax fuel for non-road use or NGO type use?

    WoodGas--May end up being dirtier, more expensive, and dangerous than other solutions.

    If you can get "hours of sunlight" or equivalent numbers for your region--we could size a solar array (light overcast is not as bad as dark and stormy weather). But it may be too expensive to use solar panels anyway for heavy loads.

    Other alternatives... There are lithium iron phosphate type rechargeable batteries. They are much lighter than Lead Acid so would be easier to transport back to the grid for recharging--Not cheap, but they have very good cycle life and are safe to use--May be "good enough" for your long term needs without the local wind/sun/genset costs/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: Qs on buying battery systems for High Discharge rates

    It would perhaps help if we knew what the actual end-use loads are. Then we could take a more "holistic" approach to solutions. For instance, all DC loads or all AC or a mixture, any induction loads, et cetera.
  • Tom_G
    Tom_G Registered Users Posts: 5
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    Re: Qs on buying battery systems for High Discharge rates
    BB. wrote: »

    Is the 1,000 watt load the least amount of energy that you can use?
    -Bill

    Yes unfortunately it is the minimum, what with number of ornithographers who will be working at the site, their equipment etc. Not to mention heat lamps for fostering and the reintroduction of birds into the environment. We have looked into catalytic LPG heaters with no open flame but decided against them.
    Cariboocoot-'all DC loads or all AC or a mixture, any induction loads, et cetera.'

    No Motors or washing machines as far as I know, possibly some tracking motors on tripod mounted cameras. A few computers, printers, a handful of AC IR heat lamps for fostering birds and their reintroduction into the habitat, these lamps may have Ballasts and be classed as induction loads, possibly a comfirmation of that would be helpful, do electrical ballasts equal induction loads?
    Lots of sensors, a few flood lights for finding our way in the dark evenings, In total the bank has to be able to provide 1kW for 1 hour.

    Using efficient DC designed appliances as much as possible would be helpful but for convenience an AC Inverter system is requested by the rest of the club, We are also possibly getting sponsorship from an Environmental agency so that will help with the Financing.
    A large efficient AC Inverter is also on the To Do list in terms of research, and also a large Battery Charger to charge the battery bank back up to full charge in 2 hours, a tall order I know!
    BB. wrote: »
    I understand the fuel cost issues. The Honda, Yamaha, and some other smaller gensets can be extremely quiet and should not bother the wildlife.
    Can you get low tax fuel for non-road use or NGO type use?
    -Bill
    We can get non taxed Diesel and kerosene at around 70 cent a liter, but transportation of the fuel to the cabin(without a road as that would interfere with the protected site status) might be difficult, the energy density of auto fuels are much higher than lead acid batteries, so possibly building up a top up supply on site might not be a bad idea, especially since the batteries may need to be recharged in 2 hours max on some occasions.

    The horse might have difficulty bringing the generator up the mountain, perhaps we should look into a Helicopter set down, or dismantling and reassembly of the generator.
    BB. wrote: »
    If you can get "hours of sunlight" or equivalent numbers for your region--we could size a solar array (light overcast is not as bad as dark and stormy weather). But it may be too expensive to use solar panels anyway for heavy loads.
    -Bill
    Average hours of Sunlight over the year in Ireland is around 3 hours a day apparently(but we get many weeks without a break in the clouds), and in Sliabh Luachra it is quite misty most of the year, but I would be interested in the sizing of a solar array! the Cabin is to be used every day for at least 1 hour but possibly up to 4 hours a day(this latter figure has me concerned about recharge rates on my battery pack and generator size) .

    Sunshine hours in Ireland graph incl hours per month average pg 7

    A Wind system is probably the best bet for us as Ireland is one of the windiest places going!
    MW Wind farms already installed around the Counties and Country

    Since my last post I have taken all that is said on board and if possible a 24V system would be a benefit, but only if inverters and chargers are roughly the same price.

    The Trojan T-105 & T-125 here on an Irish golf battery site, total around E740 for four T-125s, for a 12V 480 Ah system at C/20.
    However these aren't AGMs, my desire for AGMs really stemmed from shipping and flying concerns if I bought anything but AGMs online.

    This English site seems to be even more expensive than the Irish site above, barden-ukshop, which is surprising

    These low 34 Ah AGMs on another Irish golf site don't seem to be any brand I've heard of, and I'd need to fork out E900 for a 400 Ah system

    The Elecsol battery brand is new to me! To buy three to make a 12V 400 Ah bank would cost E742. and they are AGM's to boot
    This Irish company sells things in Sterling? strange! but they also stock chargers and Victron cables! and if the AGM claim is true, and no one has had bad experience with this Elecsol brand, they may be the most cost effective solution for our needs as AGMs normally have higher cycle lifes, right?

    Is there performance data for Trojan batteries at 1 hour discharge rates?
    akin to the information on this Rolls battery
    Rolls performance data
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    Mulling this over a bit. My initial reactions:

    1). It doesn't look as though solar will do you enough good to justify the expense. That sort of depends on how prices are over there, though.

    2). You might want something like this Exeltech inverter: http://www.solar-electric.com/exxp24vol11w.html It seems your power needs are not a steady 1 kW, but loads up to 1 kW. Shame about the need for heating via electric; it's rather inefficient.

    3). Little inverter generators like the Honda EU2000i can be carried by one man, so a horse & cart should have no trouble. They are also very fuel efficient and extremely quiet.

    4). If you're staying with the 200 Amp hour 24 Volt idea, you'd probably only need a 1 kW generator for charging. It's a bit difficult to put a full charge into any sizable battery bank in just two hours. The fastest you'd want to charge a battery is usually C/8 - about 13% of the Amp hour rate. Could be dicey.

    Let's let some others get there ideas in here too! :D
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Qs on buying battery systems for High Discharge rates

    If you can get diesel at a good price (vs a Honda eu1000i or eu2000i on petrol)... I wounder what is the smallest/quietest diesel you can find there?

    To make a good off-grid system--you really need to balances loads against the battery bank. Then match the charging sources against the battery bank.

    Too large of battery, it takes a lot of power to properly recharge it. Too large of genset (you should aim at 50% minimum electrical load from the charger/AC loads for best fuel economy) and you can use 2-4x or more fuel because of over-sizing.

    If you have AC loads--You might want to get a Kill-a-Watt (UK version) or equivalent. It will really help you measure your power requirements.

    AGM's are certainly the better choice for quick charge/discharge--but you have to size the rest of the equipment/wiring to manage those higher currents.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom_G
    Tom_G Registered Users Posts: 5
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    Re: Qs on buying battery systems for High Discharge rates

    What will be the effect of operating a half sine wave inverter on say ballasted CFLs be like? and do the Honda Generators have a built in Full sine wave output when operating on AC?
  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates
    What will be the effect of operating a half sine wave inverter on say ballasted CFLs be like? and do the Honda Generators have a built in Full sine wave output when operating on AC?
    Tom, the generators they are referring to are called inverter generators that produce sine wave power and the motors have an eco mode where the motor only runs fast enough to provide the power required. They are perfectly save for inductive loads and sensitive electronics. On eco mode they can run many hours on a liter of fuel.
    Mike
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    I'd take another look at the catalytic LPG heaters. Much more efficient than charging batteries and turning that into heat.

    catalytic LPG heaters = 98% efficient
    Generator charging batteries = 7% efficient. (engine =14%, battery charge=50%)

    As others said, auto throttle inverter generator is your best bet, in the 2,000w class, and you can get extended run kits to run off large gas tanks or propane.

    because of clouds and short days, solar is a poor choice - it needs direct sun.
    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 ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Qs on buying battery systems for High Discharge rates

    If we assume a minimum of 2 hours of day of sunlight with a fixed array (the two-three months of winter can be down to 1.5 hours per day average--so plan on genset/reduced power output during winter):
    • 1,000 WH per day * 1/2 hours of sun per day * 1/0.52 system efficiency = 962 watts of solar panels minimum
    So--How does 1,000+ watts of solar panels look for your site (cost/impact wise)?

    For dead of winter, you will still need a genset/alternative power for your system.

    Also look at how you will use power--In general, there is quite a bit of losses every time you do a power conversion/transfer. It is possible that you may make "battery packs" for your users... Charge those directly on the solar system over several days, then swap with people going out in the field (camera battery, instrumentation, computer, etc.).

    It would not be unusual to have a 20-50% loss trying to quick charge devices from your solar battery bank, vs a 20% loss by charging directly from solar during the day.

    Also be very careful about what inverter you choose for your system. For your use--I would highly suggest the more expensive TSW (True Sine Wave) Inverter over the MSW. Many small electronics can be damaged by MSW (Modified Square Wave) inverters.

    Also, you may end up with several inverters. A smaller one for charging small electronics and a larger one for heavy loads (possibly even cheap MSW) like power tools.

    If you stay with 12 volt battery bank--The MorningStar 300 Watt TSW inverter with search mode is a pretty nice unit. Search mode puts the inverter in a low power mode where it looks for a 6+watt AC load instead of simply running the inverter 100% with no load. There is both a 115v 60 Hz and a 220 VAC 50 Hz volt version.

    For a smaller system--The MorningStar inverter is hard to beat.

    A couple of articles about MSW/TSW inverters:

    All About Inverters
    Choosing an inverter for water pumping

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom_G
    Tom_G Registered Users Posts: 5
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    Re: Qs on buying battery systems for High Discharge rates
    BB. wrote: »

    It would not be unusual to have a 20-50% loss trying to quick charge devices from your solar battery bank, vs a 20% loss by charging directly from solar during the day.

    Also be very careful about what inverter you choose for your system. For your use--I would highly suggest the more expensive TSW (True Sine Wave) Inverter over the MSW. Many small electronics can be damaged by MSW (Modified Square Wave) inverters.

    Also, you may end up with several inverters. A smaller one for charging small electronics and a larger one for heavy loads (possibly even cheap MSW) like power tools.

    If you stay with 12 volt battery bank--The MorningStar 300 Watt TSW inverter with search mode is a pretty nice unit. Search mode puts the inverter in a low power mode where it looks for a 6+watt AC load instead of simply running the inverter 100% with no load. There is both a 115v 60 Hz and a 220 VAC 50 Hz volt version.

    For a smaller system--The MorningStar inverter is hard to beat.

    A couple of articles about MSW/TSW inverters:

    All About Inverters
    Choosing an inverter for water pumping

    -Bill

    Thanks for the inverter information, especially 'Choosing an inverter for water pumping' After I read through it I noticed the author mentions something that has me pondering, can you series wire two or more of the 300 watt continuous Morningstar TSW inverters in a chain, to meet the 1 kW value? Since I hadn't even factored in the extra starting up load draw from appliances.

    The document also mentions 24 & 48V DC being the new standard for off grid-ers, however I seem to me having trouble finding a reasonable inverter rated in the 24 & 48V DC range. Maybe I'm entering a bad search key?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Qs on buying battery systems for High Discharge rates

    There are some inverters that can be connected together to get more power or split phase 120/240 VAC (sometimes called "stacking")--However, the Morningstar unit cannot.

    You can install multiple inverters on a battery bank--But each will support its own loads (i.e., 2x 300 watt inverters, 600 watt total; but it is two branch circuits of 300 watts each).

    Our host has many 12/24/48 volt inverters.

    Many inverters come in 120 vac 60 Hz or 230 vac 50 Hz--But the above link is for a US retailer--so they do not list many of the 230 vac options... They may be able to order them for you--but, in Europe, you may be better off buying local (to you) and avoid the customs issues.

    We have a couple posters here from Europe that sell solar RE equipment too--They can probably give you more information on locally available product.

    What inverter(s) ratings are you looking for?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Qs on buying battery systems for High Discharge rates

    Good quality inverters and inverter/chargers available in Europe in the 1kW range:

    - Victron Mulitplus (inverter/charger) http://www.victronenergy.com/inverters-chargers/multiplus-12v-24v-48v-800va-3kva/
    - Victron Phoenix (inverter only)
    - Studer Compact (inverter/charger) http://www.studer-inno.com/?cat=sine_wave_inverter-chargers&id=433
    - Studer AJ and SI (inverter only)
    - Steca (rebadged studers, but you might have a local distribuidor that stocks them) http://www.steca.com/index.php?Sine_wave_inverters

    EDIT:
    Bear in mind that most of these will allow a peak power draw of double their rated output for a few milliseconds. Eg. the multiplus 800W can deliver 1600W for a few ms.
    Price of the 800W Multiplus is about 750 Euros. Price of the 750W Phoenix (inverter only) is about half that.

    Complete price list here: http://www.victronenergy.com/upload/documents/WEB_Pricelist%20Victron%202010-Q4%20C%20Euro.pdf