to run a computer

[ALM]

I'm slowly piecing together a solar system that I intend to use as a complete off-grid home power source (with eventually a couple of wind turbines to help keep up charge those few weeks during the year it's cloudy out here in the Mojave desert and at night). I have only just begun gathering the components, and I already have a question about exactly what I need to make it all work. I have some good batteries (a couple of deep cell marine batteries and a bus battery), 4 60 watt solar panels, a very simple 7 amp charge controller, and a 750 watt inverter. It runs a TV and antenna just fine, but the inverter alarm goes off if I try to run my laptop which requires 120 W/18.5 V/6.5 A (it'll charge, just not run). With just that info, can you tell me whether I need a different charge controller or a different inverter? I think I need a pure sine inverter to safely run electronics - is that the problem? Or is it just really and truly draining each battery so fast? Or is there another component I'm missing? All I'm trying to do at the moment is run the laptop on a sunny day.... Thanks!

[inetdog]

I'm slowly piecing together a solar system that I intend to use as a complete off-grid home power source (with eventually a couple of wind turbines to help keep up charge those few weeks during the year it's cloudy out here in the Mojave desert and at night). I have only just begun gathering the components, and I already have a question about exactly what I need to make it all work. I have some good batteries (a couple of deep cell marine batteries and a bus battery), 4 60 watt solar panels, a very simple 7 amp charge controller, and a 750 watt inverter. It runs a TV and antenna just fine, but the inverter alarm goes off if I try to run my laptop which requires 120 W/18.5 V/6.5 A (it'll charge, just not run). With just that info, can you tell me whether I need a different charge controller or a different inverter? I think I need a pure sine inverter to safely run electronics - is that the problem? Or is it just really and truly draining each battery so fast? Or is there another component I'm missing? All I'm trying to do at the moment is run the laptop on a sunny day.... Thanks!

1. Get a Kill-a-watt meter or similar so that you can see the exact power consumption of your loads.
2. Computer power supplies are notorious in that some will work just fine with a Modified Square Wave (MSW inverter, while others really need Pure Sine Wave (PSW). In addition, the computer requires "clean" power in excess of what is needed to charge the battery before it will choose to run.
3. If the inverter alarm goes off, then either the battery cannot deliver the roughly 15 amps needed to satisfy the computer power supply or else there is an output surge when you attach the computer supply and the inverter never recovers.
4. Please tell us more about your batteries.
5. What happens when you hook up two 100 watt light bulbs to the inverter at the same time.

[PNjunction]

... 4 60 watt solar panels, a very simple 7 amp charge controller, and a 750 watt inverter..

Let me guess - that 7amp charge controller is a Sunforce or equivalent on/off controller with leds for 13.2v and 14.6v ? I'm assuming you are parallelling all 4 panels together - that would be about 12amps under good conditions - too much for that controller, and 4 in parallel may not be the best idea - perhaps 2 strings of 2 each with it's own controller to the battery would be better / safer.

Or is it just really and truly draining each battery so fast? Or is there another component I'm missing?

I got a feeling the batteries aren't getting charged in the first place - typically too much battery and not enough panel. More info on batteries needed. Are you taking any voltage measurements on them after 4 hours or so of rest with no charge/discharge to determine the SOC?

[Wy_White_Wolf]

For the laptop get a 12VDC car adaptor and bypass the inverter. No reason to Convert from DC to AC just to go back to DC again.

WWW

[Sunking]

What is your laptop battery voltage?

[ALM]

1. Get a Kill-a-watt meter or similar so that you can see the exact power consumption of your loads.
2. Computer power supplies are notorious in that some will work just fine with a Modified Square Wave (MSW inverter, while others really need Pure Sine Wave (PSW). In addition, the computer requires "clean" power in excess of what is needed to charge the battery before it will choose to run.
3. If the inverter alarm goes off, then either the battery cannot deliver the roughly 15 amps needed to satisfy the computer power supply or else there is an output surge when you attach the computer supply and the inverter never recovers.
4. Please tell us more about your batteries.
5. What happens when you hook up two 100 watt light bulbs to the inverter at the same time.

I can't tell you how much I appreciate all this good info. I can't seem to find any 100 watt light bulbs anymore, but I will get a Kill-a-watt meter to measure consumption and see what's really happening. And I'll get the specs off the batteries this weekend and see how that factors in to it all.

[ALM]

What is your laptop battery voltage?

Is that different from the A/C adapter output specs? Would that kill-a-watt meter or something like it be able to tell me what it is?

[Sunking]

I can't seem to find any 100 watt light bulbs anymore,

That is because you live on the Left Coast and 100 watt light bulbs are illegal in California and will get you a life sentence if you are caught with them. But not all is lost, Ganja is legal, smoke all you want.

[ALM]

Let me guess - that 7amp charge controller is a Sunforce or equivalent on/off controller with leds for 13.2v and 14.6v ? I'm assuming you are parallelling all 4 panels together - that would be about 12amps under good conditions - too much for that controller, and 4 in parallel may not be the best idea - perhaps 2 strings of 2 each with it's own controller to the battery would be better / safer.


I got a feeling the batteries aren't getting charged in the first place - typically too much battery and not enough panel. More info on batteries needed. Are you taking any voltage measurements on them after 4 hours or so of rest with no charge/discharge to determine the SOC?

You're exactly right on the charge controller and paralleling the 4 panels. Since I have 3 batteries, running 2 panels to each of 2 and working off the 3rd would be easy. I'll get the battery specs this weekend. But how do I measure voltage on the batteries? It seems I've heard of something called a volt-meter or something in reference to auto repair - is that the tool I need? What is "SOC?" And thanks so much for taking the time to help!

[ALM]

That is because you live on the Left Coast and 100 watt light bulbs are illegal in California and will get you a life sentence if you are caught with them. But not all is lost, Ganja is legal, smoke all you want.

I got no problem at all swapping my 100 watt light bulbs for my smoke!

[ALM]

For the laptop get a 12VDC car adaptor and bypass the inverter. No reason to Convert from DC to AC just to go back to DC again.

WWW

Hmmm. ...common sense. Thanks for stating the obvious - I didn't even think about that. Can you run an inverter and a DC plug off one battery at the same time? Would you just clamp one on to the battery posts and one onto the charging posts?

[inetdog]

Hmmm. ...common sense. Thanks for stating the obvious - I didn't even think about that. Can you run an inverter and a DC plug off one battery at the same time? Would you just clamp one on to the battery posts and one onto the charging posts?

Nothing difficult here. You can attach a cigarette lighter plug for use with the computer 12 volt power supply to the same terminals as the inverter. As a practical matter it will probably be easier to attach at the inverter end of the inverter cables or at the charge controller end of the charging cables. If you have a battery bus bar arrangement, that will be the best place to attach.