Solar panels MPPT charge controller and 1500 watt Go power pure sine wave inverter part 5

[michael970]

Nice update Looks like its working great.TAKE CARE

[Fearlessthinker]

Looking forward to your AH vid. One of the hardest things is sizing a system to match the avaiable sun and usage without taking more than 25% charge off of the battery bank. (12.37V)

[Xringer]

@Fearlessthinker Me too.

Helloman and I have had some discussions (arguments?) about how much can be safely taken off a bank.

I've been told that an inverter-cut-off at 10.5v (under load) is okay, since the voltage will bounce back up, once the load is gone.. (Seems like that would depend on the size of the load).

I'm worried about my 48v inverter, since it has a 10v (40v) cutoff. Makes me wonder about the Bounce Affect.. :(

Not sure I want to drain my little bank that low..

[Fearlessthinker]

@Xringer 20-25% should be the average with 50% only when unavoidable. The AH rating is at 50%, so it is easy to undersize the bank. Even at 5000 watt hours (4 12V batterries), that's only 200w sustained for 24 hours, or 70w sustained for 3 days. Most people design around the 3-days under no sun. We try to stay under 400w continuous average when not heating or cooling. This is essentially 1 computer and a fridge.

[Xringer]

@Fearlessthinker My emergency backup system is primarily to run sump pumps in the basement. I'm afraid to do any real testing now, since we are expecting more bad weather. (This is New England) So, I want to have a good supply of electrons on hand.

I did a simple test today using an upstairs circuit. Used the PCs, clock radios & some lights. About 190 watts for 5 hours. But a lot of the time, we had Sun! So the bank wasn't being depleted. Right now (@50 deg F) it's 12.925v each (51.7v bank)

[helloman1976]

@Xringer That's what I've been told too is the 10V cutoff is fine as long as you are using deep cycle batteries as they will spring back. My bank springs back to 23.16V after they hit the 10V cutoff. The real damage happens when you drag the bank down to the 10V and keep a load on it OR after the cutoff is hit you reset your inverter and start drawing on them again. This bank is going to be run through the ringer to see how long they last before we buy a large bank and decide which batteries...

[helloman1976]

@Fearlessthinker We take our battery bank down to cutoff voltage if the demand calls for it otherwise we'll let it fall where it falls. The purpose of buying a deep cycle battery is so you can drain and fill it. If less you take off it the longer it lasts but only trying to take 25% of would be absurd. Most people who seriously live off these systems try not to go below 50% but deep cycles will handle 80% and still be ok it just shortens their long term lifecycle. For us...we dont care :)

[MrHorsetail]

So does your charge controller have a USB port that goes to the computer? That's a nice program running on your laptop showing all the readings, very useful. You have one nice system there.

[helloman1976]

@MrHorsetail No USB port, this is through the built in Ethernet port. This "website" will be available from the internet when I'm done doing all the connections. I'm waiting on a 50 foot ethernet cable I ordered last week. Thanks!

[shartne]

I like that you can actually run your washer that is sweet. So the MPPT is changing the array voltage to what in voltage? It can probably run your fridge no problem if it can run the washer. I like that inverter so far.

[helloman1976]

@shartne I must have run 4 or 5 loads today on the washing machine and it barely made a dent in the battery bank. I was pulling over 900 watts at one point for about an hour and it barely moved the voltage. Also, I saw some nice spikes today of about 700W on the MPPT side so this charger is mega-efficient. Tomorrow is supposed to be a very clear and sunny day so we'll see what happens tomorrow!! More videos coming very soon...

[shartne]

@helloman1976 I am going to get me a different inverter.

[helloman1976]

@shartne Awesome, let m know what you end up with and post videos!

[helloman1976]

@shartne The MPPT is changing the incoming voltage of around 60V to whatever the best voltage is to get the highest wattage out of the system at that point. MPPT will sweep the voltage and amperage curves and lock in on the "sweet spot". When MPPT reduces the voltage the amperage goes up so you can see 50V at 2A but the batteries are charging at 24V @ 3.75A since the voltage was reduced, the amperage went up. It's very, very efficient, I saw 800W out of 1150W of panels in partial shade. NICE!