Coleman 800w inverter - Issues

shortfatguy

Issue I had this morning when I turned on the inverter with 12.5v in the bank was I could not run/charge laptop. Alarm went off on the inverter and then shutdown. Unplugged the laptop and ran the two lamps & radio with no problem.

This is a Coleman 800w inverter and auto shut off at 10v.

Has anybody had problems with this type of inverter?

Thanks

icarus

Re: Coleman 800w inverter - Issues

Sounds like a low voltage alarm/shut down. Try it again with the same loads, while measuring the battery voltage. Your laptop probably draw ~75 watts, (~6.5amp/12vdc). Depending on the battery and the soc it may draw it down too far, even if the battery is full charged.

Do you have a book on the inverter, or find one on line? I suspect there is a low voltage shut down to protect the battery from too much discharge.

Icarus

PS From an ad for a coleman 800msw inverter,,,:Short Circuit Protection: Automatically shuts off until short is removed
Over-Voltage Protection: Automatically shuts off when input exceeds 15 V DC.
Low Voltage Alarm: Audible when battery discharges to 10.6 V DC.
Under-Voltage Protection: Automatically shuts off when input is less than 10 V DC.
Overload Protection: Automatically shuts down unit when continuous draw exceeds 800 watts.
Thermal Protection: Automatically shuts off when surface temperature exceeds 150 degree F.

shortfatguy

Re: Coleman 800w inverter - Issues

Look's like I used my battery bank's capacity to below 80% yet my voltage was at 12.5. Yet the marketing poop that you listed and is on my package really doesn't list keeping an eye on amperage.

icarus

Re: Coleman 800w inverter - Issues

shortfatguy wrote: »

Look's like I used my battery bank's capacity to below 80% yet my voltage was at 12.5. Yet the marketing poop that you listed and is on my package really doesn't list keeping an eye on amperage.

Your battery may be 12.5vdc in a static state, but under load it can't produce enough voltage for the amperage draw.

Elsewhere you have stated that your laptop draws ~95 watts. With inverter losses lets round that up to 120 just for fun. That translates to a 10 amp draw at 12vdc on the battery, a not insignificant number for a small battery bank.

Imagine if you take 8 D cell batteries, wired them in series to get 12vdc, and then tried to start your car. The result would be a click and nothing more. If you measured the voltage while under load it would read ~0vdc. Turn off the key and it would once again read ~12vdc.

As the suggested reading points out, batteries have a finite capacity to produce instantanious power. They are a chemical "factory".

Icarus

BB.

Re: Coleman 800w inverter - Issues

The other thing to check is your wire sizes/lengths and connections.

At 800 watts and minimum battery voltage, you are talking about 100 amps... as an example; 10' of 12 gauge wire between a battery and an inverter is only going to be good for 200-400 watts--not the 800 Watts rating of the inverter.

And, checking your laptop's power requirements--is it 95 watts average or is that the "peak" average when it is charging its internal battery (or it is more than 95 watts when charging its internal battery).

A good way to wiring problems is to put a steady load on your device (inverter in this case) and use your DVM to measure the voltage drop from the battery lug to the inverter lug... If you get more than a few tenth's of volt drop--then you may have a loose/dirty connection or undersized wire carrying too much current. You can also measure the battery lug voltage (say 12.2 volts under load) and the inverter lug voltage (10.5 volts) and see that there is too much drop somewhere....

It is hard to describe in words--but it is really easy to isolate problems by measuring voltage drop with a good (and calibrated) DVM.

-Bill

shortfatguy

Re: Coleman 800w inverter - Issues

BB. wrote: »

The other thing to check is your wire sizes/lengths and connections.

At 800 watts and minimum battery voltage, you are talking about 100 amps... as an example; 10' of 12 gauge wire between a battery and an inverter is only going to be good for 200-400 watts--not the 800 Watts rating of the inverter.
-Bill

This could be it. I've redirected a generator start/stop switch from 50' away to the positive side of the battery bank & inverter to shutdown it for the evening. So we're talking about 100' of loss, correct?

BB.

Re: Coleman 800w inverter - Issues

shortfatguy wrote: »

This could be it. I've redirected a generator start/stop switch from 50' away to the positive side of the battery bank & inverter to shutdown it for the evening. So we're talking about 100' of loss, correct?

If we are talking about the + power lead from the battery, through the 100' of wire, switch, and back to the inverter--yep... I would be surprised that it worked much at all (switching power supplies can draw very "sharp" current spikes which can, very easily, cause long "unblanced" wire runs to "ring" (feedback into the inverter control circuits--causing them to shutdown--and/or lots of "radio" noise in your radio/TV/satellite receivers.

--In addition to just I*R drop (current * resistance = voltage drop).

Take a look at the "voltage drop calculator" thread... There is an Excel spreadsheet that allows you to plug in wire gauge, temperature, and run lengths to see how much voltage drop you will have...

For example, 12 awg wire, 122 F, 100' (round trip length), and 20 amps gives you a 3.55 volt drop. So, your 12.5 volt battery trying to supply ~180 watts through the inverter, will give 9.05 volts at the inverter input...

Note that you can have a 3.5 volt drop on a 120 VAC 20 amp circuit and everything will run just find at 116.5 volts.

At the inverter:

9 volt * 20 amp = 180 watts available -- 60 watt loss

Now, rewire the inverter with short 12 vdc leads, and run the 120 vac to your cabin (assuming same wire gauge even though using 1/10th the current)...

120 volts at 2 amps = 240 watts
120-0.3v * 2 amp = 239.4 watts

So--with the identical load and wire run, you only have a 0.6 watt loss--1/100th the amount of power loss with the long 12 vdc run...

The short answer is to rewire your inverter with an appropriate fuse, short/heavy gauge wire, and a single switch (or relay with remote switch) to turn off the power. Run your long runs at 120 VAC.

And measure the inverter's idle power--if the inverter has relatively low idle losses vs your power use--it may not even be worth turning off most of the time.

And look at your maximum 120 VAC loads--the MorningStar 300 watt inverter would work very nicely for your system... Even has a remote off switch.

Some of the mid-range Exeltech also have a remote off option (you will need to check with Wind-Sun to see if they offer this option on their units).

I know that pure sine inverters are expensive--but by the time you go through trying to make everything work--and worry about the issues with Mod-Sine/Square wave inverters (noisy radios/tv's, possible damage to some motors/electronic devices)--if you want a reliable home without surprises--bite the bullet and do it right--with the correct equipment.

If you go with a larger system, look at the Outback or Xantrex Inverter/Charger systems--getting one combined unit instead of separate AC charger, inverter, transfer switch, generator controller, etc. is probably where you will end up eventually anyways...

-Bill

shortfatguy

Re: Coleman 800w inverter - Issues

BB

BB. wrote: »

Now, rewire the inverter with short 12 vdc leads, and run the 120 vac to your cabin (assuming same wire gauge even though using 1/10th the current)...

AH HA, Time to correct you. In Maine a summer home on the ocean is a "cottage". Summer home in the woods is a "cabin" and a summer home on a lake is a "camp". Almost was given a smart lump a few years ago mixing that up.

Thank you. I thought the switching may play a part in drop of V & A.

Mw

icarus

Re: Coleman 800w inverter - Issues

Bill has it dialed.

If you are running ~100 of 12volt wire to your inverter you will have the said HUGE drop.

I used to wire an inverter that way because it was easy and I only had a couple light bulbs (15watt) load. I would see almost a .5 volt drop, and that was running it with two pairs of #6 copper wire. Moved the inverter to about 2' from the battery and had no measurable drop.

Icarus

PS No point in paying for amperage just to heat up the wire and go off into space!