some battery usage and solar numbers real life

[saltydawg]

Okay, so I put a solar panel on the trailer and just used the trailer for 3 days. First some specs

120 amps of lifepo4 battery
100 watt renogy glass panel
rich solar mppt charger ( same as the renogy but 20 bucks cheaper )

Started out with a fully charged battery, ran a car radio, usb plugs charging phones, a fan some, lights and my inverter for several hours powering a 120 volt 100 amp speaker/amp. the solar providing power during the day, most power was used at night. Each day was about the same, I used about 20% of the battery or about 25 ah by sunrise. The big part of that was the inverter after dark, and I woke each day to the 80% or 25 ah or so of used power. We only really used the usb and radio during the day and still when the sun went down the battery was basically fully charged.

The during the day usage was the radio at about 2 amps an hour, and the usbs. At night was about .7 amps on exterior lights for about 4 hours, and the speaker/amp for about 3 hours and its draw was between 3-6 amps depending on the music and volume. So the solar ran the stuff during the day and still charged me up.

Yes I know this is not the normal teardrop power usage with the inverter, but the other stuff is pretty normal. I built my power system to be able to handle this type of load and did like a champ.

[TimC]

That's interesting Scott. I am wondering if you are monitoring actual demand on your battery with an ammeter or are you looking at battery SOC in the morning before solar production?

The reason I ask is I'm wondering if you are actually using more than 25 aHr and the daytime aHr use is mostly recovered as it is consumed. I just installed ammeters in my system. I hope to figure out what my actual demand is as I'm using a 12v fridge for the full day (24hr) and try to charge electronics while the sun shines and usually by late afternoon I have a fully charged battery. Maybe if I figure out actual night demand I won't have to worry about charging everything during the day. My equipment is similar other than having 200w of panels.

Tim

[saltydawg]

That's interesting Scott. I am wondering if you are monitoring actual demand on your battery with an ammeter or are you looking at battery SOC in the morning before solar production?

The reason I ask is I'm wondering if you are actually using more than 25 aHr and the daytime aHr use is mostly recovered as it is consumed. I just installed ammeters in my system. I hope to figure out what my actual demand is as I'm using a 12v fridge for the full day (24hr) and try to charge electronics while the sun shines and usually by late afternoon I have a fully charged battery. Maybe if I figure out actual night demand I won't have to worry about charging everything during the day. My equipment is similar other than having 200w of panels.

Tim

I have a shunt on the battery, so I see whats going into the battery, so yes I am consuming as its being made during the day. Thats why i looked at the soc in the morning.

I could have looked at the mppt during the day to see what it was producing but I am not worried about it. I built my system to be hands free and not have to monitor it all the time, i see power going in or power going out and soc. Thats enough info for me. If during the day its going in, solar is working, then state of charge as the sun goes down to see where I am over all.

[TimC]

... I built my system to be hands free and not have to monitor it all the time, i see power going in or power going out and soc. Thats enough info for me. If during the day its going in, solar is working, then state of charge as the sun goes down to see where I am over all.

Gotcha. Sounds like a good approach.

[John61CT]

12V?

That panel should be able to put 30Ah per day back into your bank in good insolation conditions.

Maybe more if tilted to track the sun.

See how that compares over time just as a reality check.

[MickinOz]

Sounds like a very reliable and robust system, assuming the amplifier is 120V 100Watts, not 120V 100 amps!

I must get around to installing my 250W panel one day.
But it hardly seems urgent, since I really only do one-nighters.

My system so far is:
12V 105 amp hour battery
Renogy MPPT regulator, which I hook up to a small 40W panel that lives on my garage roof. Tat panel is very old, at least 30 years. So it only makes about 30 watts these days, but that still does the job.
4 x led lights, drawing about 0.6 amps from memory.
2 usb charge points for phones, etc.
8 inch oscillating fan I haven't used yet.
1 x TV/DVD drawing about 2.5 amps if I turn the volume up, which is unnecessary in the small cabin. Tends to draw about 2 amps max.
Fridge outlet I have only used once. I've pretty much decided I'm going to put in an icebox instead. I'll just run a couple 3 litre milk jugs full of ice, and refreeze in the chest freezer at home. Or in the truck fridge. On the look out for an original metal "Esky". Unfortunately they've become a bit collectable, so sometimes the asking prices rival a cheap 12V fridge.

Seems I seldom use more than 8AH. Still I think I'm only at 3 trips - not a big sample size.

[saltydawg]

assuming the amplifier is 120V 100Watts, not 120V 100 amps!

The wattage was based on the draw the power meter was showing, the speaker/amp was rated at 300 watts. The meter jumped around from 6 to 8 amps 12v most of the times. I bet the actual draw was higher, due to the meter not being able to show true rms type readings, but averaged a few times a second, plus the inverters capacitors smoothing it out as well.

I must get around to installing my 250W panel one day.
But it hardly seems urgent, since I really only do one-nighters.

Well this is the second trip and both where 3 nights, with drives of 400 miles one way. Its getting it excersize.

[MickinOz]

Well this is the second trip and both where 3 nights, with drives of 400 miles one way. Its getting it excersize.

400 miles each way is a long haul - even here in South Oz where you can do that while only passing through a half dozen towns and rarely encountering a hill worthy of the name.

I gotta get out more.
I will be retiring soon. At that point, I'm hoping to be away more than one night at a time.
Probably be leaving the missus at home a bit. 1 night is her limit.

assuming the amplifier is 120V 100Watts, not 120V 100 amps!

The wattage was based on the draw the power meter was showing

Yeah, I figured the 120V 100amps in your first post could be assumed to be watts.
I considered a radio or other music player, didn't eventuate. TV takes a USB stick if I get keen.

[saltydawg]

I have a radio too, but when your at a huge paintball event with 1200 other people with a few hundred of those camping, volume is your friend. the louder the better.

[troubleScottie]

You did not state, so not sure what you did with your inverter.

Inverters are notorious for a) being inefficient and b) being a parasitic draw.

Converting 12VDC to 120VAC does suffer from loses. Generally speaking cheaper inverters work less well. Hence the use of any many 12VDC items as possible. Especially bad is doing something like charging a USB device from an AC outlet OR running a computer off AC as it just converting back to a DC voltage, often not 12V but still DC. It would be better to use a DC based dual USB port or a 12VDC adapter/connector for the computer.

The parasitic draw is a real issue. Even when there is no load on the inverter, it still draws power. You need to disconnect it from the battery ie switch it off or remove the connections. Most inverters do not have a on-off switch. As with inefficiencies, cheaper inverters are generally worse with parasitic draw.

[saltydawg]

You did not state, so not sure what you did with your inverter.

Inverters are notorious for a) being inefficient and b) being a parasitic draw.

Converting 12VDC to 120VAC does suffer from loses. Generally speaking cheaper inverters work less well. Hence the use of any many 12VDC items as possible. Especially bad is doing something like charging a USB device from an AC outlet OR running a computer off AC as it just converting back to a DC voltage, often not 12V but still DC. It would be better to use a DC based dual USB port or a 12VDC adapter/connector for the computer.

The parasitic draw is a real issue. Even when there is no load on the inverter, it still draws power. You need to disconnect it from the battery ie switch it off or remove the connections. Most inverters do not have a on-off switch. As with inefficiencies, cheaper inverters are generally worse with parasitic draw.

The inverter was running the speaker/amp or a powered speaker like a dj would use. I dont know the brand but it said 300 watts and its 120 v ac, but we where not running it at full volume.

My inverter is renogy 1000 watt pure sign wave, controlled by a remote switch. When its off, it does not draw anything. My power meter when everything is off shows a draw of .001 amp, when the light on the power meter is on it shows a draw of .007 amp. The inverter does run thru the shunt so I do see the draw if any. I know there are losses, but with 120 ah of lifepo4 battery i dont care, if I need 120 volts i need 120 volts. I can turn it on and give you the actual stand by load if you want edit. Just went and did it, the standby draw of the inverter is .534 amps at 12 volts, so I could run it on standby for over 9 days if I disconnected the solar. Obviously the solar can keep up with the standby load if I needed to.

I have several 12 vdc usb ports, everything is 12 volts except the inverter.

[MickinOz]

I just had a look at the inverters n the Renogy Australia website. Sure get a lot of features and functionality for your money.
Pretty impressive, your average aut supply shop inverter seldom has remote switching and I've never seen one setup to run automatically in UPS mode.

[RJ Howell]

I see amp base, I see amp recovery.. What I don't see is amp use. Since you bouncing between Ac/DC it's better to discuss this as wattage.

What are you using? Time to do a Power Audit! Break it down by item and time of use. No other way to work through this, no short cuts. What do you wish to run? What does it take? How long do you wish it to recover?

Right, Wrong, indifferent... It's how I approach this. I survive on 60ah lithium, yet building up a bit more for some more convince!

[saltydawg]

I see amp base, I see amp recovery.. What I don't see is amp use. Since you bouncing between Ac/DC it's better to discuss this as wattage.

What are you using? Time to do a Power Audit! Break it down by item and time of use. No other way to work through this, no short cuts. What do you wish to run? What does it take? How long do you wish it to recover?

Right, Wrong, indifferent... It's how I approach this. I survive on 60ah lithium, yet building up a bit more for some more convince!

Believe me I have thought about over doing the calcs as its one of the things I do daily. But I dont need to, I ran the system pretty hard with the inverter and it worked. I know in the real normal use with out the inverter I would be good for at least 5 days, not including any solar charging.

The purpose of the thread was to show that with 100 watts of solar, even with a pretty heavy load most people would be fine. Tony runs a cpap plus a few lights and a fan and is charged by noon according to him.

My full load not including the water pump, when I turn everything on is about 3 ah. Thats radio, fan, lights, usb plugs.

[tony.latham]

Tony runs a cpap plus a few lights and a fan and is charged by noon according to him.

8-10 amps per night. I watch the battery monitor like she's my 16-year-old daughter.



100 watts on the roof, 30 on the tongue box.

Tony