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ackray
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# Posted: 15 Mar 2013 23:15
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New here so please let me know if this is the correct forum to post this.
I've taken over a cabin, main house is 4 bedrooms, then a barn and two greenhouses. It is entirely off grid and the existing systems were around 30 years old and falling apart.
Obviously learning as I go.
Currently I've upgraded the water pump, added three new generators, new 6kw inverter and 10 golf cart batteries for a power bank.
At this point I'd like to ask some advice about the battery banks and the charging.
First I have two banks. One for the house power, deep cycle golf cart batteries hooked up for five 12 volt banks, the second for the 220volt well pump. Bunch of thin plate car batteries to power the pump.
The well bank was isolated because of the initial high surge. The thin plate batteries seem to handle it better. The inverter is an eBay find 3000w surging to 6000w. Oddly enough it's working out really well. So far.
To charge the batteries I am using a mix of generators and chargers.
1 - all power america "2000" watt generator connected to a power max 55 amp 12 volt charger and the 220v inverter charger. The idea with this set up is that the smaller generator just keeps the batteries up for normal use. Runs over six hours on a 1.3 gallon tank.
2- 5500 watt diesel. Powers the second mains, most outlets now live, feeds the 6000w inverter charger , 50 amps @12v, and an iota 50 amp charger for the water bank. This is used for chore days, laundry, vacuming etc.
What I am now trying to do is to; resize the battery bank, calculate amps used, watts in, reserve power and so on. Obviously not a small topic.
Specifically each 6 volt cell is rated at 235 Amp Hours.
Doubled to 12 volt still the same amp hours.
235 x 5 (banks) = 2820 AH
2820 x 12 = 33840 watts
33840 x .4 DoD Gives me 13,536 watts of usage.
However I am not getting even close to that amount.
How do other people calculate available watts out of their banks?
Thanks!
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offgrid ME
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# Posted: 16 Mar 2013 08:43
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First 235 x 5 is 1175ah of battery
40% of this would be 470ah
470ah at 12v would be 5640wh or 5.6 kwh of usable power
When you figure usage you need to take into account the conversion efficiency of the inverter (e bay special could be only 85%). You also need to account for the idle usage of the inverter. Some will use up to 30w of power 24hrs a day for a total of 720wh.
So with this in mind with 40%dod you have about 5640-720 X .85%= around 4.1kwh of usable power.
Ned
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ackray
Member
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# Posted: 16 Mar 2013 09:44
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Do'h Math. Thanks Off Grid!
Don't know where I got the 2820 from. But moving on.
Leaving the water bank out of the mix for now.
House & Barn power are supplied from this bank. This is the third year for the Golf cart batteries.
A normal charge - discharge cycle for the batteries has been from around 12.3v to 11.6 volts. Or roughly 70% to less then 30% of charge.
From what I have now been reading this is not good.
Left running in the house is:
Small fridge - 100w used in morning and again in evening.
Misc Comcast Boxes and WIFI - Maybe 20w.
Light are 6w LED bulb.
The present TV is a 150w Sansui, I'll be swapping it out for a 46w Vizio.
Lets call it 300 watts of use. based on around 4K of reserve power there should be over ten hours of usage from the banks between charges. In reality, once people get home in the evening, lights TV on and so on, we'll need to start charging within a couple of hours.
Obvious culprit are the batteries. Water is up, hydrometer reading shows no dead cells, terminals are tight, Vaseline on top to prevent corrosion.
Less obvious would be appliances eating power but we've checked that pretty carefully so far.
I am presently in the process of wiring in the diesel generator, transfer switch, second mains and the Royal Power PIC6000. until that is complete we are running off an old (20-30 years?) Heart Inverter charger. From what I hear it was hit by lightning a few times. at least on one ocasion smoke was pouring out. Currently only the 12v to 120v function is working. That of course could be the problem also.
Basically I'm throwing this on the forum to come up with ideas and pointers as I seem to be doing things twice - get it working and then do it right. So hopefully I can learn enough to do it right the first time.
Thanks again!
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offgrid Me
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# Posted: 16 Mar 2013 13:29
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We dont know the health of your batteries right now. If they have been deeply discharged and not properly charged they may be nearing the end of their life at three years old. What are the specific gravities. They should be around 1.265 when fully charged if at room temp. If they are cold the sg should be higher, about .004 per 10degrees colder. So at 40 a fully charged battery should have an sg of about 1.280. There is also something called the peukert effect which says that the faster a battery is discharged the less total capacity it will have. This is why deep cycle batteries are rated with an hour#. Is 235ah the rating at 20hrs. This will be less because you are trying to use their capacity in 10 hours.
Ned
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ackray
Member
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# Posted: 16 Mar 2013 15:18
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Thanks Ned.
That was my first guess too. Just ordered a hydrometer with thermometer for testing as opposed to the ball one that is being used.
Next question. Define "charged" at how many volts am I to consider the battery's charged? I don't think I've ever seen this bank over 12.6v and then only for a few minutes right after turning off the generator.
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Anonymous
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# Posted: 16 Mar 2013 15:58
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Quoting: ackray I've ever seen this bank over 12.6v
then they have never been fully charged. 12.7 is full 100% being close is not good enough when it is the normal thing that is part of the problem with relying on a generator, the last little bit takes a long time and wates fuel. some pv will help finish off the charge to 100% don't rely on a voltage reading that gives false readings unless the batteries have been at rest for several hours use a float, not a ball type hydrometer.
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ackray
Member
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# Posted: 17 Mar 2013 22:53
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Switched over to the iota tonight after the power max just fried. New inverter wired in today as well. Plan to run the generator all night and see what they come up to.
Thanks.
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rayyy
Member
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# Posted: 18 Mar 2013 13:39
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I know I probably could have got away with a 1000 watt Honda.Other than my microwave and vaccuum cleaner are the only things that would draw anything near that.The EU2000I can handle anything I plug into it.Because it's electronic system can detect a motor starting up,it generates enough punch to kick the moter into full RPM's.Like my air compressor and table saw.I know my old 2500 watt Coleman cant get a simple motor spinning fast enough to kick in the run windings.I sometimes wonder if the EU1000I would get twice the running time on a gallon of gas,though?
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ackray
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# Posted: 21 Mar 2013 01:20
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@rayy
Since there is no renewable energy at this site yet I've spent lots of time playing around with the generators I have. Wen 3500, all power america 2000 and a power land diesel 6500 w
The Wen is a rock star and I would recommend it to anyone. Over 1000 hours within the first year. Will surge to well over the 3500 rating.
To get the best fuel use I try to run the generators at 1/2 load.
The 2000w APA was set to power the pm3-55 and the 220v inverter charger. Even so I had to adjust the throttle to get enough RPMs to keep the voltage up. On the other hand the 80cc motor will run for around 6 hours on 1.3 gallons. If you want to try this gen get two of them. You'll need one for parts. Yes, I do have two of them.
Currently I am still learning but so far I've managed to cut the fuel bill to about a third of what it was.
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Moving Pictures
Member
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# Posted: 21 Mar 2013 18:18
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KIll-o-watt those boxes and wifi. My router is 10w - that's 240 watts a day, if not turned off.
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ackray
Member
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# Posted: 21 Mar 2013 19:45
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@moving pictures.
Thanks. Stuff like the wifi an lights seem pretty straight forward. What I am looking at now is the 350watt washing machine, the 100watt fridge different TV's and so on to try and establish patterns of use.
It would also be useful to see how much electricity the different battery chargers take and what the different generators are putting out.
I'd like to start looking at patterns and fine tuning the data.
Talked to some people at efergy today and their meters look promising. As well as the ability to log it on-line and get real time updates.
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Alaskaman
Member
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# Posted: 5 Apr 2013 15:17
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If you change over to LED and put everything on power strips it will save you thousands of watts. If it is not on shut offt the power strip. The ghost loads are killers. I even went with an LED T.V. went from LCD at 550w down to 55w. With every light in my cabin on and the TV with sat running, the load is between 150w-210w. I also recommend investing in new appliances preferably Danfrost manufactured items. The biggest thing you can do to save money is lesson your consumption. The biggest investment I made was in my off-grid set up. It's expensive to drain down your batteries. Okay off my soap box. Good luck to you.
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