I have lots of outlets because I hate not having an outlet where I need it. But they will never all be loaded at the same time. And I have 6 8w lights.
Need help designing off-grid system
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Outback makes outstanding inverters, but they are large and pricey. And going from your questions so far, I am guessing your top three priorities are price, price and price.
With that in mind, AIMS makes decent (not great) inverters. The PICOGLF series goes down to 2kW, has hardwire connections and includes a battery charger. Takes about 11 watts in standby, 28 watts running with zero load. About $700.
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OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNHComment
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I was on the fence with the Samlax EVO series. The EVO series looks promisingLast edited by Matrix; 10-10-2018, 10:46 PM.285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4Comment
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To charge batteries you need to limit both voltage (to the absorb voltage) and current (to a safe limit.) More importantly, you need to operate in current limit rather than reset or hiccup or anything. LED power supplies are adjustable both for voltage and current. Since they are much cheaper than battery chargers, people who build small EV's (ebikes and scooters) are using those supplies to charge lithium ion batteries. They can be used for lead acid batteries as well, although they can only implement two stages of charging (bulk and absorb) so they are not good if you are going to float your batteries. (Or you could adjust it after absorb is over, but that's annoying.)
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Wanna make your any 3, 4, or 5 Stage Charger a Float Charger is simple. Set the voltages to Float Voltage and on a 48 volt battery is 52 to 54 volts.
MSEE, PEComment
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Here's a question.....My battery bank is 11,520 watt hours wired all in series. I have a 240ah battery. Is my discharge rate is supposed to be somewhere around 24a (C/10)? So if I have an inverter that is 1500w, isn't that a problem? 1500w/12v=125a. What if I had a 2000w inverter? I am only getting this from the stickied post about inverter size vs battery size so I might be totally misunderstanding.
If I never have a load that high, will I be ok? Like ILast edited by Bigbus; 10-19-2018, 12:05 AM.Comment
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Here's a question.....My battery bank is 11,520 watt hours wired all in series. I have a 240ah battery. Is my discharge rate is supposed to be somewhere around 24a (C/10)? So if I have an inverter that is 1500w, isn't that a problem? 1500w/12v=125a. What if I had a 2000w inverter? I am only getting this from the stickied post about inverter size vs battery size so I might be totally misunderstanding.
If I never have a load that high, will I be ok? Like I
Here is the limitation. Batteries have internal resistance, and the resistance is directly proportional to size. Bigger the battery, the lower the resistance. When you have current flowing through resistance develops a Voltage, and when current flows through a battery a voltage loss is uncured. In other words if you were to measure voltage on a battery with out a load or current, you will see an open circuit voltage say 12.6 volts. Now you apply a load aand draw current, the battery voltage goes lower. Demand more current, and the voltage drop increases.
You have to limit that voltage drop to roughly 2 or 3 %, and generically When you go up to C/8, you have lost 2 to 3% of your voltage. You can go higher no problem for the battery, but your Inverter is not going to be happy with Low Voltage and in protest, the Inverter shuts down from under voltage leaving you in the dark with a False Trip.
So at C/2 or 120 amps, your Inverter will likely trip off-line from under voltage despite the batteries being fully charged. That is telling you have a poorly deigned system not capable of doing what you want. So if you really want to run a 12 volt 1500 watt Inverter would require a 750 to 900 AH battery. You only have 1//3rd of that.
One way around that is to use AGM batteries as they can easily handle C/4 and some can discharge at 1C and faster. Smallest AGM I would be comfortable with is 300 to 400 AH range.
MSEE, PEComment
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You have to limit that voltage drop to roughly 2 or 3 %, and generically When you go up to C/8, you have lost 2 to 3% of your voltage. You can go higher no problem for the battery, but your Inverter is not going to be happy with Low Voltage and in protest, the Inverter shuts down from under voltage leaving you in the dark with a False Trip.285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4Comment
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Some inverters are not fixed but let you set the Low Voltage Cut Off point and more advanced inverters have a delay setting in time for the cut off to delay the inverter cut off for a minute (give or take) to allow for short temporary bursts of hi loads. So does it hurt FLA batteries to discharge at hi amps for short periods of time (a minute to say 10 or 15 minutes) providing you do not discharge the battery to under say 50% SOC. Obviously it would not be a good idea to run a battery at 75 amps until it hit 10% SOC.
Be careful here because if you were to lower the voltage to say 10 volts, one morning you wake up after a cloudy day before and you battery voltage is resting just above 10.5 and the Inverter is still drawing current on a dead battery that should have been recharged already and now being damaged. So best solution is a timing loop logic like you suggest, that says something like: If voltage is equal to or less then 11.0 volts for 1 minute or longer, Disconnect.
Hope that helps.Last edited by Sunking; 10-19-2018, 11:00 AM.MSEE, PEComment
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One last question! How do I safely ground the system? Do I need anything other than the ground from my circuit panel? What about when I'm hooked up to shore power?Comment
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I will be running appropriately sized grounding conductors from each piece of gear to the chassis. The ground in my load center is also bonded to the chassis as well as the shore power ground connection.
Also want to be mindful of proper neutral bonding when switching between shore/generator/inverter.
Last edited by PNW_Steve; 11-13-2018, 01:09 PM.Comment
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