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question about chargers  RSS feed

 
scott bendtson
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I am putting together a off the grid solar set up. I'm doing it piece by piece when I find deals. So far I have 1300 watts of panels and 20 225ah 6 volt batteries. I won't be installing these panels until this summer. My question is that I need to charge these batteries while they are in storage and I don't know what charger I should use. I would like to get one that i will use when off the grid to use with my generator. I have been looking at inverter/chargers but My home will have minimal a/c use so I won't need much of an inverter and they are expensive. Could I use a regular household charger if so witch one?
 
Steve Harvey
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scott bendtson wrote:I am putting together a off the grid solar set up. I'm doing it piece by piece when I find deals. So far I have 1300 watts of panels and 20 225ah 6 volt batteries. I won't be installing these panels until this summer. My question is that I need to charge these batteries while they are in storage and I don't know what charger I should use. I would like to get one that i will use when off the grid to use with my generator. I have been looking at inverter/chargers but My home will have minimal a/c use so I won't need much of an inverter and they are expensive. Could I use a regular household charger if so witch one?


6 volt batteries does not explain enough, are they lead acid, agm? What voltage will you be running to your inverter? Most people use a 12 volt to 120v ac inverters because they are more common and cheaper. The higher the amp rating the better, however if you have 1300 watts and 12 volts out of your panels you would need a minimum of 120amp charger. What ever amperage you have coming out of the panels you need a charger that is rated for that amperage. For example a 12 volt 30 amp charger is rated for 12 volts 30 amp input. Output will vary on the type and amount of batteries.

I would get 5, 24 volt 30 amp chargers and divide your 20 batteries into groups of 4 wired in series producing 24volts DC. Your 5 groups of 24volt batteries would require 1 of the 5 chargers per group of 4 batteries wired in series. You can then Hook up your panels in parralel and series and in groups of 5 so that you have 24volts and about 20 amps going to the Chargers per charger. Note! You can have less than 20 amps going to your 30 amp charger, 30 amp is a max input reference, the higher the amperage the faster the charge time. Also if using 12 volt panels, 2 12 volt 3.5 amp panels in series will give you 24 volts 3.5 amps, wire 2 more in series and in parralel to the other 2 panels and you will have 24 volt 7 amp.

You will need one hell of a inverter after the batteries to support the load of the battery banks. Like a 24volt 60amp DC input, to a 120v AC output. Really the larger the amp input rating the safer it will be at the expense of efficiency.

Finally wire gauge size, go big or go home.
 
Steve Harvey
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Ps. 225 amp hr batteries will need 11.25 hrs to charge from drained at 20 amps. I would reduce your amp draw or energy usage so that you are only slightly draining your batteries per day. Energy efficient appliances and led lights are the way to go. Smeg fridges and Fisher and Paykel appliances are flagship brands in energy efficiency and some Smeg fridges also come in cyclic defrost rather than frost free which is insanely more energy efficient than frost free.

Hope this helps.
 
Steve Harvey
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Here is why I say 20 minimum charger. The charger will charge in different stages and automatically reduce amperage to the batteries while charging.

http://www.chargingchargers.com/tutorials/charging.html
 
Steve Harvey
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Obviously a 20 amp charger is less than 25 percent of the amp hour rating of the batteries. It's more like 10. Imo, anything more than a 30 amp charger is not cheap household quality and you would have to get a good quality solar specific multiple bank charger from a solar electronics supply company and it would cost a lot more.
 
Steve Harvey
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As far as mostly DC powered stuff, I don't understand this I live in Canada and most DC appliances available here have inverters on them from AC.
 
scott bendtson
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Thank you for your replies. I haven't thought about using five different charge controllers and wiring it the way you described. I like that just for the fact if something breaks it's cheaper to replace one of the controllers instead of a large expensive one. I guess I may have worded my question wrong. What I was looking at finding out is what type of charger should I use to top off the batteries or charge them completely when hooked up to a generator. I was looking at inverters/chargers but they are pricey. Just recently I stumbled upon perhaps using a rv converter/charger (converts Genny ac to DC) what would your recommendation be? Im very new to all of this and have been learning allot as I go. Thanks for the help
 
scott bendtson
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Oh and the batteries are lead acid and the panels are 24 volt.
 
Steve Harvey
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scott bendtson wrote:Thank you for your replies. I haven't thought about using five different charge controllers and wiring it the way you described. I like that just for the fact if something breaks it's cheaper to replace one of the controllers instead of a large expensive one. I guess I may have worded my question wrong. What I was looking at finding out is what type of charger should I use to top off the batteries or charge them completely when hooked up to a generator. I was looking at inverters/chargers but they are pricey. Just recently I stumbled upon perhaps using a rv converter/charger (converts Genny ac to DC) what would your recommendation be? Im very new to all of this and have been learning allot as I go. Thanks for the help


get 10 automotive 12 volt trickle chargers or 20 6 volt. Note, wire 2 batteries in series to make 12volts. Hook up the 10 separate groups of 2 batteries in series to trickle chargers. Plug trickle chargers to power bar. Plug power bar to generator.

Some generators say in the manual do not plug anything into the generator that uses a circuit board. I would check this.
 
Steve Harvey
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How many watts are your panels and what brand are they?
 
scott bendtson
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They are schuco 245 watt 24 volt. Wont the trickle charger take a really long time to charge vs using a higher amperage converter charger?
 
scott bendtson
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I don't mind paying more for what I need but trying to figure out exactly what I need is the problem.
 
Steve Harvey
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scott bendtson wrote:They are schuco 245 watt 24 volt. Wont the trickle charger take a really long time to charge vs using a higher amperage converter charger?


If you are trying to charge your batteries off the gas generator to use the stored energy there is no point. Just use the generator. You can't get more energy than the original energy supplied, charging the batteries would just mean you are wasting fuel.

If you wanted to charge the batteries and keep the batteries topped up so they don't get damaged during storage, use the trickle charger and use the generator to run your other devices.
 
Steve Harvey
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scott bendtson wrote:They are schuco 245 watt 24 volt. Wont the trickle charger take a really long time to charge vs using a higher amperage converter charger?


Those sound like great panels. Some advice, even with the 20 batteries you will only be able to use a 1000 to 1500 watt inverter. With a 1500 watt inverter. If you are running 1500 watts of devices at the same time your batteries will be drained after 7.5 hours. If you want to run your home on solar you will need to greatly reduce the amount of energy you use in you home by like 90 percent. You should also look into small wind turbines to help charge your batteries faster. For example at night when you are using very little electricity your wind turbine could be recharging your battery bank.
 
Zach Muller
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Hey Steve I am briefly looking around at small wind turbines. Are there any in particular that you have seen working well for people charging battery banks of this size?
 
scott bendtson
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I guess the reason for they Genny would be when we get multiple days of little sun. I was thinking of using the generator to charge the batteries and supply power to the house until they are charged. Luckily I have already planned on not much power usage especially on ac. I will have a propane fridge, hot water, cook top with Wood for heat. As many DC items as possible like water pump, tv and led lights. The inverter would only be used for very intermittent use. I will probably pick up a few more panels soon because they are a great deal. I haven't really thought about wind energy mostly because I have been focused on learning about solar. I did look into small turbines but the reviews on them were not good.
 
Steve Harvey
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Zach Muller wrote:Hey Steve I am briefly looking around at small wind turbines. Are there any in particular that you have seen working well for people charging battery banks of this size?


http://www.ebay.com/itm/1-5KW-24V-i-1500Z-WIND-GENERATOR-ista-BREEZE-WIND-TURBINE-2081/151251117243?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D777000%26algo%3DABA.MBE%26ao%3D1%26asc%3D28808%26meid%3Def13b79f43e14880a8191cadf8a03c50%26pid%3D100009%26rk%3D1%26rkt%3D1%26mehot%3Dpp%26sd%3D301519560129

This one looks good 60amp output you will need an ac to DC charger you could run this in tandem with your solar panels. When it is too windy put a hinge on the wind mill pole and make it so you can pull the turbine down at a 90 degree angle to the ground a few feet off the ground. Stop the blades somehow with a strap or something so they can't spin. Then when the wind settles put it back up.

Charging time equals volts x ah / watts. 2 panels like Scott's in parralel would be 490watts if they are 24volts at peak sunlight they will produce 20 amps of current. So 24 volts times a 225 ah 24 volt battery. Note! 4x 6volt 225 ah batteries in series is, 24volt 225ah. Divide this by 490watts and you get 11 hrs charge time for 2 panels charging 1 battery or group of batteries totaling 24v 225 ah. This is a very basic calculation and usually it takes longer because of resistance and multi stage charge controllers changing charge current and volts to protect the batteries.

As you can see you will not be able to charge 1 24 volt battery with the amount of sunlight supplied, if you only have 6-8 hrs of peak sunlight a day. Therefore a Wind generator is required to charge the batteries after the sunlight is gone or diminishing.

A lead acid battery can only charge at a max of 15amps for like 80 percent of the charge. So the max amount of panels you can use to charge 1x 24 volt 225hr battery is 2x panels in parralel at 11 plus hours charge time. This set up will give you 2.25 hour of usage if drawing 1000watts of current to your devices. If you want more run time on your devices you need to replicate this set up x amount of times until you reach the amount of stored energy you require to run your house 24hrs a day.
 
Steve Harvey
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scott bendtson wrote:I guess the reason for they Genny would be when we get multiple days of little sun. I was thinking of using the generator to charge the batteries and supply power to the house until they are charged. Luckily I have already planned on not much power usage especially on ac. I will have a propane fridge, hot water, cook top with Wood for heat. As many DC items as possible like water pump, tv and led lights. The inverter would only be used for very intermittent use. I will probably pick up a few more panels soon because they are a great deal. I haven't really thought about wind energy mostly because I have been focused on learning about solar. I did look into small turbines but the reviews on them were not good.


Scott to answer your question about using the same chargers to charge your batteries as the chargers to charge via your panels. If your gennys power output is 120v ac then no you can not. A car battery charger rated at 120v or this marine style 120 volt ac to 24volt DC 4 bank charger would charge your batteries from dead in less than 6 hours. It would also charge 16 of your 20 batteries through this one charger if you hookup 4 banks of 4x 6 volt batteries in series.

http://www.batterystuff.com/battery-chargers/12-volt/marine-chargers/DPSS4.html
 
Steve Farmer
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you only need to charge each battery less than once a month while they are in storage so get a $10 - $20 car battery charger that is able to do 6V and has desulphating pulse feature and switches automatically to trickle charge once batt is full. Make sure it has ALL of these features. take 15 seconds each day to put a different battery on charge
 
frank li
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Scott, what dc voltage are you planning on using to power house loads?
If you are buying equipment for your future permanent installation, you will need to settle on a battery voltage and have at least a rough system layout. A primary detail first on, is the battery wiring. You have a bundle of batteries, they may need to be broken down into two or more systems for the sake of avoiding having too many parallel strings.

If you intend to use all of your batteries and adopted 12v, you would have 10 strings of 2x 6v batteries in series. Capacity is 2250ah or roughly 20Kwh, maximum usable. 20,000 watt hours for micro system folks. Not an ideal battery scenario, cables get big at 12v and distance is rough unless most of these loads are a couple amps or less.

The required charge amps is over 200a if you are using it and 100a for a minimum effective charger, if only occasionally using it. for storage, you can go lower, but you would still want 50a or more and you will want to equalize at some point.

For this amount of batteries, 48v is going to let you have 2 strings of 8 batteries as a main house battery and another smaller standalone system of 12v or 24v, outbuildings and or a dedicated use such as comms, fencers, security, water works, landscape/outdoor lighting, boiler, ssmall vehicle, battery electric power tools etc.,along with a backup for main system failure or maintenance shut-down come to mind as applications.

24v is great for off grid dc load and battery voltage and step down to 12v is efficient to gain access to the rv, yachting, and trucker appliances along with the scads of 12v common devices and electronics including aa, aaa, and other small rechargable battery chargers.

48v can be fine even if it must be stepped all the way to 12v, but to step it to 24v will be slightly better. You could supply 48v to switching power supplies near the point of use and convert there for appliances or groups of them (lighting, office electronics, power over ethernet anyone?).

Also, are you a DC'er for life? This also may be a fork in the road, sometimes ac power is just convenient and if you gotta have a generator you will need to decide on how important ac power is in your system and if you will have a dc gen-set or an ac one. This helps with inverter selection.

My favorite small system inverter/charger right now for integrating a grid or generator ac source is the magnum 1524ae, it has an automatic transfer switch, charger, low consumption standing by, awesome surge capability, and is available in 12v, though not 48v and will assist pv for charging larger batteries while passing generator or grid ac to loads.

If you have batteries and solar panels you will likely need a pv charge controller(s).
I suggest good money be spent in this area, especially if you plan on pv-battery- dc as primary power. Here is a good place to start, outback, morningstar, midnite, schneider, use a good one with a nice battery monitor or at least a good state of charge meter.

The Midnite Classic series is our preferred control for many systems, high amp rates, high voltage, great monitoring, flexible battery voltage, high quality, relay control, and super programable. You could, with this controller or one like it, charge and maintain all of your batteries in two strings of 10 at 60v with several modules temporarily mounted. You will need a good controller eventually and midnite is hard to beat for much of the work we do.



If you only need a supply for occasional, low power ac, there are a couple nice inverter choices (morningstar, samlex, powerbright, zantrex) and transfer switch/load control devices that leave room for an ac charger budget assuming you already have an ac generator.

In my experience 24v and 48v smart chargers are as expensive or more expensive than RE purpose built inverter/chargers and not as usefull in 90% of off grid systems that require them. Also, if you need a big ac charger and occasional big ac power that you need to operate independent of the generator, and especially if you a need low draw-constant standby, outback inverters are hard to beat, come in a range of wattages and are worth every penny, I promise. If you need to get a battery/generator system together before you can mount even temporary modules, and would use this setup for off grid power, then the inverter would be my first RE gear purchase, followed by pv mounting asap. To get this done with a sledgehammer and a tack could be a 48v inverter/charger and a small charge controller $50-$120 for the remaining batteries out of your twenty.

 
S Bengi
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Hourly Energy Production:1300W from the solar panel
Daily Energy Production: 1300W x 4Hr =5,200Wh
Usable Battery Storage: 40% (charging above 90% full wastes alot of energy and going below 50% kills your battery faster)
Minimum Battery Need: 5,200Wh/.4 = 13,000Wh
Actual Battery: 2x Minimum Battery Needs = 27,000Wh
Ashrssuming these batteries are used batteries (storage reduced by 50%) then you would be just about okay. If they are all brand new you have alot of emergency power.

Assuming
P=5,200WH each day,
V=24V DC system
AH= 217
if charging time=4hrs, you are going to need a 54amp 24V charger. (http://www.amazon.com/Tripp-Lite-APS2424-Inverter-Hardwire/dp/B00006HNTD)
if charging time=11hrs, you would need a 20amp 24V charger. (price $300)

 
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