Is my inverter draining power?

litninrod · October 2017

I'm just getting started, so all help appreciated.
I bought a small cabin on 15 acres, and I'm trying to set up an off grid system. It already had 3 tiny panels and a little charge controller, but I found that I could do almost nothing with that. So here's my setup so far.
2 - Trina 235 w panels
2 - Duracell Ultra 230AH 6v golf cart batteries connected in series to make a 12v 230 AH system
HQST 40A MPPT Solar Charge Controller
Mighty Max 12 Volt 1000 Watt Pure sine wave inverter

So far, I've used the system to charge lanterns/flashlight and cell phone. I have a cell phone booster antenna plugged in. I don't have the stats for that but it uses minuscule power. I have 3 - 6w .5a 12v LED bulbs in a fixture, The CC says that load is 1.4a, so looks about accurate.

The only other thing I've run is a 12" fan. The tag says it's 120volt, .4amp.
The charge controller has a battery picture with 4 bars to show how charged it is. Leaving the 3 bulb light fixture on for 4 hours doesn't see to affect that reading much.
However, running that fan for 4 - 5 hours will drain all 4 of those bars. The voltage reading goes from 13.8 at full charge to 12.3 or so after running the fan.
So .4 amps at 120 volts is the same as 4 amps at 12 volts, correct? Running that fan 5 hours then, should be 20 amp hours. A 230 Ah battery bank minus 20 Ah should mean my battery has 210 Ah left. So maybe enough to take me down to 3 bars from 4, but not clearing all 4 bars.

The near future plan is to add 2 more of the Duracells. A few DC lights, a fan, a small chest freezer, and a TV or Radio would be pretty much everything I want to run at this time. (I have a generator to use for power tools and such.)

So my questions - Is there something wrong with the inverter that's sucking out way more juice than it should? Or have I misunderstood something and that fan actually would use that much power?

litninrod · October 2017

I meant to include some current PV stats. During mid-day and assuming the battery isn't full, I get as much as 62 volts, (though usually high 50's), and 6.1 amps from my solar panels according to the charge controller readings. I have the 2 panels wired in series.

Photowhit · October 2017

You have some misconceptions, Your fully charged battery has a resting voltage of 12.7 volts. It may appear to be 13.8 while charging, or when it is receiving some energy from your panels. 12.3 volts May or may not be the resting voltage. Is this with the fan running? 12.3 volts on a resting battery would be about 70-80% full. This is just from my faulty mind, remembering that 12.7 is roughly fully charged and 12 volts is roughly 50%.

I have no idea what the bars are suppose to represent. The fan will certainly be a large load for your system. At about 48 watts. The inverter it's self likely runs at 15-30 watts continuous load and will likely be about 85% efficient. so your 48 watt load becomes about a 56 watt load.

I couldn't find a spec sheet on line, but Amazon has a reply from a seller who says to call for a spec sheet;

https://www.amazon.com/1000-Watt-Pure-Inverter-Marine/dp/B01N3MBB0K

You might look at O2cool 10 inch fans they run under 10 watts and put out pretty good volume of air. I've got 2 running now!

litninrod · October 2017

Thanks Photowit. I thought the 13.8 was high, thinking I had read somewhere that 12. something was fully charged. I'll look into the O2Cool. I've been just trying to figure out what I have and what I can do with it, as opposed to the proper way of adding up total load of everything and then sizing a system to it.
13.8 reading would be when I've just arrived for the weekend and during the day, so fully charged from the week of no load and sunlight hitting the panels.
According to the CC manual, Full battery shows 4 bars, then 3, 2, 1 and no bars as power is being used. Get below that and the no bars battery icon begins to blink on and off, indicating you've gone too far. The load automatically cuts out at that point until it's recharged. How accurate that is I don't know. But even at a 56 watt load with that fan, how much should I expect the 230 Ah battery bank to drain in an hour?
Oh I should point out that this drain was during mid day sun, so even with the panels bringing me all they could, it still dropped down to 12.3 or so.

Photowhit · October 2017

If that's while the batteries are connected to the charge controller and you have the panels in the sun, something is wrong...

mcgivor · October 2017

Photowhit said:

If that's while the batteries are connected to the charge controller and you have the panels in the sun, something is wrong...

Could that be the float voltage perhaps? One other point, is the inverter connected to the load terminals of the controller ? If so remove and connect directly to the battery via a fuse or circuit breaker rated to protect the conductors between the two. What size are the conductors?

mcgivor · October 2017

Regarding fans, I use a 12 VDC oscillating fan with a brushless motor, it's about 14" diameter, 15 watt 1.3A, no need to have the inverter running.

Photowhit · October 2017

mcgivor said:

Photowhit said:

If that's while the batteries are connected to the charge controller and you have the panels in the sun, something is wrong...

Could that be the float voltage perhaps?

12.3 volts is not a float voltage that anyone can imagine...

mcgivor · October 2017

Reference was to 13.8V upon arrival, but yes 12.3V with sun and a small load it should be higher, the panels should be able to support such a small load and charge, missed the last sentence details.

softdown · October 2017

I think my bedroom ceiling *may* be an energy hog. It seems that some fans are capable of being energy hogs. Seems that smaller, newer fans with plastic blades are generally more efficient.

litninrod · October 2017

mcgivor said:

One other point, is the inverter connected to the load terminals of the controller ? If so remove and connect directly to the battery via a fuse or circuit breaker rated to protect the conductors between the two. What size are the conductors?

No, the inverter is connected directly to the batteries. I have the load terminals running to a DC blade fuse panel which currently only powers the one light fixture.
At the moment, the inverter is connected directly to the battery via the cables supplied with the inverter. Cabin is 2 hours away, but I want to say it's 6awg wire? No breaker or fuse in line yet.

litninrod · October 2017

Photowhit said:

If that's while the batteries are connected to the charge controller and you have the panels in the sun, something is wrong...

To verify, panels in the mid day sun, connected to the CC and the CC connected to the batteries. The inverter runs off the batteries, and the fan is the only thing running. So that's why I came here, because I thought the same as you - something is wrong. That fan might not be the ideal appliance to use, but it just didn't seem like it should be depleting the battery that much during the day while the panels should be charging it.

littleharbor2 · October 2017

Did you buy the batteries new? What is the mfg. date on them?

litninrod · October 2017

littleharbor2 said:

Did you buy the batteries new? What is the mfg. date on them?

New from Batteries Plus about 3 months ago. I'll check the manufacture date when I go down this weekend

mcgivor · October 2017

Do you have a digital volt meter and a clamp on ammeter? Knowing what the actual output of the panels is is invaluable, remember the current output from the panels will be lower, due to the increased voltage, but the output from the charge controller to the battery would be what is going into the battery, the voltage would be dependent on the state of charge and the arrays ability to overcome the battery voltage. As the battery voltage rises the current will drop as it approaches full charge, before going into float, having tools to measure will take a lot of guesswork out of the equation. The graphics on the controller are just indications, not accurate measurements.

Estragon · October 2017

The inverter efficiency ratings are typically ~85% *peak*, which is likely at close to full output. With a 48w load on a 1000w inverter, I suspect the efficiency is much lower.

You might be able to get a rough idea of this. If, when you arrive at the cabin, the batteries are full and the pv has good sun, see what difference there is in the pv output on the controller without the inverter and fan, and with them turned on.

pdh · October 2017

mcgivor wrote:
> Do you have a digital volt meter and a clamp on ammeter? Knowing what the actual output of the panels is is invaluable

I'll second that. When you get down to problems like this, where the key question is "how much power is that thing actually drawing (or producing)", a DVM and clamp-on ammeter are absolutely invaluable. You don't need lab-grade instruments -- if you can measure volts and amps to within even 5%, then you can troubleshoot much more quickly based on those numbers than you can via trial and error.

BB. · October 2017

This DC/AC Current Clamp DMM from Sears is "good enough" for the job ($60 normally, on sale for $50 right now):

http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P

Note that DC current clamp meters require Zeroing for accurate DC current measurements (the zero point drifts over time). With no current flowing wire in the meter clamp, press the Zero button, then make measurements (the zero button removes the offset/drift from the Hall Effect Transistor).

-Bill

litninrod · October 2017

I do have a multimeter, and a meter that plugs in between the outlet and the appliance to see what it uses. The Ammeter looks like something I should add. I just bought the cabin/acreage about 3 months ago, and there's been a lot of work needed to the property, so I admit I haven't spent near as much time with measuring/calibrating/observing the solar set up as I obviously need to. I haven't plugged in the inline meter yet to see what that fans is drawing, which is first on my list for this weekend.

I have a little digital meter for battery output, but I haven't wired it in yet, because the batteries and components are in a temporary corner until I get a little more work done on the corner where the battery box and components will be permanently located.

When I show up at the cabin during the day with the batteries fully charged, the CC will show PV output of 57-62 volts (depending on exact time and any little clouds, etc) and minimal amps, like .1a. Turning on the fan doesn't change the voltage but the PV input will now be 1.2 - 1.4 amps, and the battery output according to the CC will also show that -1.4 amps.

After a few hours, the battery level indicator on the CC will show some of the bars missing as it's discharged some. The PV input now will be something like 58 v, 5.6 a, and the battery voltage would be down to around 12.2 or so. It was at 13.8 when I arrived, so fully charged plus receiving power from the panels, down to 12.2 still receiving power from the panels the whole day.

Aguarancher · October 2017

just for reference..all voltages are with the battery bank in a resting position..ie. not being used

Image: https://us.v-cdn.net/6024911/uploads/editor/av/bio00gro33vh.jpg

litninrod · October 2017

Footnote - reviewing my CC manual, 13.8 v is the float charging value, so that's why I see that number when I first arrive at the cabin

Aguarancher · October 2017

Have you checked the water level in those batteries? Only refill with distilled water and when they are cool is best. Try not to overfill.

litninrod · October 2017

Aguarancher said:

Have you checked the water level in those batteries? Only refill with distilled water and when they are cool is best. Try not to overfill.

I haven't checked that. I will do that when I go down Friday though.

mcgivor · October 2017

Generally when the batteries are new, water consumption is pretty low, as thy age, it will gradually increase, but do keep an eye on the levels, make it a habit, as habits are hard to break. The discharge whilst in good sunlight is something that needs attention, something is not right, the voltage should remain at float with the load explained, you really need a clamp on ammeter to check the status of the system.

litninrod · October 2017

Just updating from this weekend.
I ordered the ammeter but it hasn't arrived yet.
Someone asked manufacture date of the batteries One is 6/2017 and the other is 7/2017. Water levels on both are full and bubbling.
I have a little digital inline meter that I hadn't installed yet. Blue back light, readings for Volts, Current in Amps, Power in Watts and Energy in Watt hours, about $17 on Amazon - you guys probably know what I'm talking about. I wired it in this weekend.
I also have a meter that plugs in between an outlet and an appliance. I have a cellphone signal booster antenna plugged in at all times, so that accounts for a little power usage.
Voltage on the inline meter matches what my CC says within a 100th, so one might say 13.35 and the other 13.34, so that appears accurate. I find it annoying that it gives me the charging voltage rather than the actual battery voltage. The only way to read current battery voltage is to disconnect the PV or wait until nightfall.
The fan label says .4 amps AC. The meter I plugged in between the fan and inverter said .389 with a little variation. The digital meter on the battery said 4 to 4.1 amps DC. Allowing for the cell phone antenna, tat also seems correct.
Someone mentioned inverter efficiency above. The fan should be about 48 watts, and my Power reading was 58 watts, so about an 82% efficiency or 18% loss if I calculated that right.
I failed to note the exact time when I got everything set up to start metering, but closest guess is a 6 hour test. At the end of that, the Energy setting read 382 Wh. Divide that by 58 watts and you get 6.5, so that's about right. Divide 382 watts by 12 volts and I get 31.8 amp hours. If I multiply the 31.8 times the above figured 82% efficiency of the inverter, I get 26.1 amp hours. So the 4 amp fan running 6 hours would be 24. Add a little for the cellphone booster, and the math all comes out right.
So, a 230 Ah battery bank minus 31.8 Ah used is 198.2 left. So I should have roughly 86% charge on the battery bank. At nightfall, I had 12.49 on the voltage reading, which according to the chart above is around 80%. It was overcast, so not the best day for testing, but just using batteries alone, the power I used should have left me with 86% charged. Adding in that I was getting some power from the PV, I would expect to be at 90% or better. And on a full sun day I would think running just that fan and cell phone booster would be more than covered by incoming power.
The little battery icon with the bars that had me so concerned is still a mystery. The manual refers to it as "battery capacity" but no further description. It seems that maybe it is a measure of how much power I'm getting from the PV relative to how much charge is in the battery. But it's not a fuel gauge, which is how I was initially reading it. At night it showed no bars, while the new voltage meter showed 12.49, or 80%. So basically I've decided that icon is worthless and to pay more attention to the numbers than the pictures.

Probably too much information, but I wanted to give you guys everything you might need. So, any observations on my math or my assumptions?

Is my inverter draining power?

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