HELP: Inverter is draining battery almost instantly! Why?

[spoon]

Hi,

New to the forum and also, most things electrical aren't really my streong suit so bear with please

Basically, we live in a caravan in the middle of a field. My set up consists of 1x 250w panel connected to this charge controller - http://www.amazon.co.uk/waterproof-c...rge+controller

That is hooked up to a numax 110Ah XV31MF, this is practically new. I bought it (new) about 3 months ago and I took care to trickle charge on mains for 48 hours before putting it into the caravan so should be fine.

Then I have an inverter similar to this one, except it is the 1000w/1500wpeak version - http://www.ebay.co.uk/itm/2000W-Peak...QAAOSwgkRVVMbZ

I can't find my exact inverter anymore, but this is the closest to it, the badge on the front is identical. The inverter is connected via crocodile clips onto the battery terminals.

The problem is this, my system runs fine with the LED lighting etc. When I try and plug my laptop in via the inverter, the indicator on the charge controller goes from green or flashing green to RED very quickly, within a few minutes.

I don't use it once it goes to red, however, the minute I turn the inverter off the CC indicator goes back to green?!?

This problem happened again last night so I used a multimeter on the battery this morning and it was reading 12.56v and slowly increasing (cloudy day down in the SW)... I think ten mins later it had gone to 12.59v. So the battery is definately being recharged via panel.


Am I right in thinking that all of this points to a 'dodgy' inverter?? Or is there something else I am missing/getting wrong.

Any help would be greatly appreciated (especially if in nice easy laymans terms ), I'll try and answer any further questions about setup as best I can.

Many thanks.

[createthis]

Batteries sag under load. The only time you can get an accurate state of charge (SOC) is when they've been idle for about an hour. Idle means no solar input AND no load. It's a rare state in solar systems, so most people do their SOC early in the morning before the sun comes up when they're not using power. You can buy amp hour meters to give you a better idea of what is going on, but they're fairly expensive because they're basically predicting things all the time. They're computers.

I assume that battery is lead acid based on the listing on amazon, so here's a SOC chart: http://www.energymatters.com.au/comp...age-discharge/

That's a 1320Wh battery, so if you only discharge it to 50% or 12.2V SOC, you should get about 660Wh out of it.

The inverter you listed is a 1000W inverter. At full 1000W, you'll drain the 660Wh in just over a half an hour. However, the voltage of the battery will go below 12.2V before you've drained 660Wh from the battery. That's how sag works. You can remove the load and you'll see it "bounce back" pretty quickly. That's why you can't trust voltage readings while the system is in use.

So, I think you could either have a bad battery or a bad inverter. In order to figure out which, I would first get an AC kill-a-watt meter and see how much power I'm using from the inverter, multiply for efficiency losses, and figure out how long you think it should last given 660Wh of usable capacity. Once you know how much power you're using, you can wait for the red light on the charge controller, then remove the load and solar input, let the battery bounce back, and see what the battery's state of charge is.

It's possible you're just seeing sag. It's possible either the battery or inverter is bad. Hard to say from what you've posted so far.

[spoon]

Batteries sag under load. The only time you can get an accurate state of charge (SOC) is when they've been idle for about an hour. Idle means no solar input AND no load. It's a rare state in solar systems, so most people do their SOC early in the morning before the sun comes up when they're not using power. You can buy amp hour meters to give you a better idea of what is going on, but they're fairly expensive because they're basically predicting things all the time. They're computers.

I assume that battery is lead acid based on the listing on amazon, so here's a SOC chart: http://www.energymatters.com.au/comp...age-discharge/

That's a 1320Wh battery, so if you only discharge it to 50% or 12.2V SOC, you should get about 660Wh out of it.

The inverter you listed is a 1000W inverter. At full 1000W, you'll drain the 660Wh in just over a half an hour. However, the voltage of the battery will go below 12.2V before you've drained 660Wh from the battery. That's how sag works. You can remove the load and you'll see it "bounce back" pretty quickly. That's why you can't trust voltage readings while the system is in use.

So, I think you could either have a bad battery or a bad inverter. In order to figure out which, I would first get an AC kill-a-watt meter and see how much power I'm using from the inverter, multiply for efficiency losses, and figure out how long you think it should last given 660Wh of usable capacity. Once you know how much power you're using, you can wait for the red light on the charge controller, then remove the load and solar input, let the battery bounce back, and see what the battery's state of charge is.

It's possible you're just seeing sag. It's possible either the battery or inverter is bad. Hard to say from what you've posted so far.

Sorry, but alot of this is beyond my knowledge. However, I think I understand. Let me run it by you... I should check the battery voltage without load, i.e. disconnect everything then apply multimeter to get a truer reading... after leaving it for an hour.

What do you mean by an AC kill-a-watt meter? I have a multimeter...


What I can say, is that the last time this happened the battery got to around 13.5v after a few days good sun and only minimal LED lighting being used.

The only thing I run on this inverter is my laptop via charger which is rated @ 19v, 3.42a and 65w or my mobile phone charger which I assume is even less.

What other info can I provide to pinpoint whether its battery or inverter?

(btw, thank you and apologies for my more than basic understanding of such things)

[Wy_White_Wolf]

First problem it looks like you have a mismatch between the charge controller and solar panel to battery voltage. At 250 watts that should be a grid intended or 24v panel. You have a PWM controller. You need an MPPT or you're throwing over 1/2 you power away. What's the VOC rating of the panel to know for sure?

Not knowing which light is flashing/turning red it could be showing an overvoltage problem. That would be from the panel and PWM CC being mismatched to the battery.

WWW

[spoon]

First problem it looks like you have a mismatch between the charge controller and solar panel to battery voltage. At 250 watts that should be a grid intended or 24v panel. You have a PWM controller. You need an MPPT or you're throwing over 1/2 you power away. What's the VOC rating of the panel to know for sure?

Not knowing which light is flashing/turning red it could be showing an overvoltage problem. That would be from the panel and PWM CC being mismatched to the battery.

WWW

Yep, the panel is a cast off from a friend who works for a solar company. So I imagine it is a 'grid intended'. I don't know what the VOC of the panel is, how do I find out?

The CC has 2 lights. The panel indicator is supposed to flash if overvoltage, it has never done so. The other is the 'battery status indicator'. This is the one that flips from green to red within 5 minutes of turning the inverter on.

[createthis]

Sorry, but alot of this is beyond my knowledge. However, I think I understand. Let me run it by you... I should check the battery voltage without load, i.e. disconnect everything then apply multimeter to get a truer reading... after leaving it for an hour.

Yup. You don't have to disconnect everything as long as the inverter is off and the charge controller isn't charging, but yup, that's it in a nut shell.

What do you mean by an AC kill-a-watt meter? I have a multimeter...

You'd need two multimeters to get an accurate reading, because multimeters only measure volts OR amps, not both at the same time (watts). Most multimeters max out at 10 amps or so. With a 1000W 12V inverter, you might be pulling well over that 10 amp rating, depending on load, so I don't really recommend using a multimeter to measure amps unless you have the fancy inductive clamp kind of amp meter.

Kill-a-watt is a brand of meter that tells you how many watts you're using on an AC circuit. Other brands make similar meters. I happen to have a Ryobi meter. You can see it in use here: https://youtu.be/VlaHBB3GRwg?t=96 Some inverters have a watt meter built-in, btw. Mine doesn't. Judging from the faceplate, it doesn't look like yours does either.

I think the Watts-Up brand meters do the same thing, but on the DC end of the inverter. Six in one, half dozen in the other. Doesn't matter which kind you use, just helps to have a meter so you can see what's going on in the system.

[spoon]

Ok, well by the time I get back this eve it will have been dark for over an hour with nothing being drawn, so will test battery voltage then.

I also have an identical battery bought at the same time for emergency back up. I will try putting that on, but I'm sure i tried this previously and had the same result.

[createthis]

Ok, well by the time I get back this eve it will have been dark for over an hour with nothing being drawn, so will test battery voltage then.

I also have an identical battery bought at the same time for emergency back up. I will try putting that on, but I'm sure i tried this previously and had the same result.

You might want to wire that battery into the circuit permanently in parallel. Lead acid batteries die the true death pretty quickly if they are not topped off regularly. Plus, then you'll have twice the capacity.

[spoon]

You might want to wire that battery into the circuit permanently in parallel. Lead acid batteries die the true death pretty quickly if they are not topped off regularly. Plus, then you'll have twice the capacity.

How simple is that to do, what bits will I need?

[createthis]

How simple is that to do, what bits will I need?

This is a good tutorial: https://youtu.be/dZzinsfI2Y0

I have no idea where you find those fat battery cables. I suspect lots of places carry them. 6 AWG would be more than enough, I'd think. Check around on the internet for 12v cable sizing based on the number of amps you plan to draw from the inverter and the number of feet between the batteries, then find somewhere to source the cables.

[lkruper]

Ok, well by the time I get back this eve it will have been dark for over an hour with nothing being drawn, so will test battery voltage then.

I also have an identical battery bought at the same time for emergency back up. I will try putting that on, but I'm sure i tried this previously and had the same result.

When you first hooked up your laptop how long did it run before you had a problem? From what I see on the net your battery should get 500 cycles at 70% DOD. You say you trickle charged it. With what charger? I see that Numax has their own brand of charger that is a 10 amp charger for a 110AH battery. So evidently a charge rate of 10% of the AH capacity is good for this battery. When you put your spare battery on the inverter, make sure it has been completely charged first and also measure the voltage at rest before you use it.

I see that your 20 amp charge controller has this feature:
Automatic 12V/24V voltage detection and temperature compensation for three battery types (sealed, gel, flooded)

I presume you have it set for sealed? Also, when you charge, does the charge controller finish he charge and indicate it has finished with the leds?

[spoon]

When you first hooked up your laptop how long did it run before you had a problem? From what I see on the net your battery should get 500 cycles at 70% DOD. You say you trickle charged it. With what charger? I see that Numax has their own brand of charger that is a 10 amp charger for a 110AH battery. So evidently a charge rate of 10% of the AH capacity is good for this battery. When you put your spare battery on the inverter, make sure it has been completely charged first and also measure the voltage at rest before you use it.

I see that your 20 amp charge controller has this feature:
Automatic 12V/24V voltage detection and temperature compensation for three battery types (sealed, gel, flooded)

I presume you have it set for sealed? Also, when you charge, does the charge controller finish he charge and indicate it has finished with the leds?

Yep, I'm pretty sure it is set to the correct battery type. I will check again though. My CC is actually a landstar (I think), but is identical to the one I linked in every respect that I can see.

My battery is definately 'sealed' lead acid... Not flooded then.

The CC is quite simple. The LED flashes slowly green when battery is full, stays green when mostly full and goes orange to red when overdischarged.

Mine tends to always be solid green, sometimes it flashes. With a few full days of strong sun and no useage.

[lkruper]

Yep, I'm pretty sure it is set to the correct battery type. I will check again though. My CC is actually a landstar (I think), but is identical to the one I linked in every respect that I can see.

My battery is definately 'sealed' lead acid... Not flooded then.

The CC is quite simple. The LED flashes slowly green when battery is full, stays green when mostly full and goes orange to red when overdischarged.

Mine tends to always be solid green, sometimes it flashes. With a few full days of strong sun and no useage.

I could not find anything about your battery online which specified the charge rate. Did you get a usage guide which tells what amps it likes? 10% is safe, and 20% good for some AGMs. Your charge controller is 20 amps. that is approximately 0.2C where C = 110AH.

[spoon]

I could not find anything about your battery online which specified the charge rate. Did you get a usage guide which tells what amps it likes? 10% is safe, and 20% good for some AGMs. Your charge controller is 20 amps. that is approximately 0.2C where C = 110AH.

Nope, didn't get any usage instructions with battery.

[lkruper]

Nope, didn't get any usage instructions with battery.

Also: When you first hooked up your laptop how long did it run before you had a problem? From what I see on the net your battery should get 500 cycles at 70% DOD. You say you trickle charged it. With what charger?