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400 watt inverter

Discussion in 'General Discussion' started by lawman0210, Oct 25, 2015.

  1. lawman0210

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    So I bought a 400 watt inverter to plug in a P3 charger and a P2 charger. I think they are both around 65 watts. It won't allow me to plug both in. Why can't a 400 watt handle 2 chargers that are surely under 170 watts? I did not have my vehicle running. Could that be it. The store recommended I get the 1000 watt inverter but it was twice the price, much larger and I thought that was going to be overkill.

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  2. TheWire

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    A couple things.

    1. How are you connecting this to the vehicle? A 400 Watt inverter could draw at 35 - 45 amps. Which is twice what most cigarette lighters can supply.
    2. Many inverters have a low voltage cut-off. Measure the DC voltage at the inverter input terminals. Try a test with the car running, which will give you a higher voltage.
    3. If this is a cheaper inverter (< $200) its likely not pure sine and is a modified sine inverter which can cause issues with digital electronics. DJI's chargers are switching supplies and 2 of them may cause unusual harmonics that fault the inverter. Try powering a resistive load such as a 40 or 60 watt incandescent light bulb at the same time as the chargers. That may help filter out funky current draw of 2 switching power supplies.
    4. Bear in mind that engine starting batteries will have a MUCH shorter life if subjected to discharging from a continuous draw like an inverter. They are made for short bursts of power to start a vehicle as opposed to deep discharging like marine or golf cart batteries.
    If you would like to post the model# of the inverter, I can look at the specs on it. Let me know if you have any other questions.
     
  3. lawman0210

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    I will post the Model # tomorrow. From what your saying it may not be the inverter but most likely is it faulting when reading the voltage from my battery? I will have vehicle running next time. Although not sure if an inverter will do me any good after thinking about it. If it takes several hours to charge a battery. Then if it's not charged I will need to start vehicle to go home and doesn't that cut the power while cranking? That will restart the battery cycle?

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  4. lawman0210

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    I forgot to get the model number but it worked fine connected straight to battery charging 1 p2 and 1 p3 battery. I then went out to garage and found my old 400 watt inverter that I always thought was bad (connecting to a cigarette lighter) I plugged that one and it worked fine as well. Only difference is the new one has a usb plug as well. I did note that while vehicle running my battery tester read output was 14.1 (I have a new 900 cranking amps battery. As soon as I turned engine off it immediately dropped to 12.9 and within 20 mins down to 12.2. Restarted vehicle with no problem and batteries continued to charge normally. I do believe it charges faster tho with the engine running
     
  5. Ti22

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    Back in the day when electric cigarette lighters in a car were actually used for lighting cigarettes you could draw 30A or sometimes more from most any outlet. Wire gauge in the dash and fuse rating was plenty for drawing that much current.

    Now they’ve become neutered “accessory” power outlets for cell phones. I was recently surprised my iCharger had a helluva time drawing more than 10-12A from a 2008 Escape/Mariner outlet.

    At one point blew the **** 15A fuse. That’s not gonna supply much power to something like an DC/AC inverter or some other type high power device.

    Another issue, unless you measure Ah/Wh consumption using inline power meter it’s awfully hard and/or impossible to “guesstimate” how much energy’s taken from a vehicle starting/cranking battery.

    Key description is: “starting/cranking” - supplying battery power over a long period of time is much different than momentarily spinning an IC engine for starting. You’re not doing your vehicle starting battery any favors running loads without the engine running. And then you're not doing your vehicle or MPG any favors idling for long periods of time.

    For me at least in the field, ‘now bring a separate 12V battery to power my invertor or RC Charger. Preferably, deep cycle or something along those lines.
     
  6. lawman0210

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    12 Volt battery? How do you recharge that? Never had much luck recharging a 12 Volt car battery. Seems when they are dying they are gone

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  7. tcope

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    I just bought A 300 watt Bestek inverter . I agree with what I've read, a quality inverter is a must. My old one would cut out with a low voltage reading even if the engine was running and putting out 14 volts. My triple battery charger puts out 4 amps per battery. I can charge two batteries without issue. The problem with a 3rd is the amps being pulled through the lighter. 8 amps is fine but at 12 amps the inverter usually trips. So it's not the watts or volts, it's the amps through the lighter. The inverter trips as it starts to get low voltage. I spent an extra few dollars and got the batter clips with my inverter.
     
  8. iammrbt

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    This brand works great. About 60 bucks at autozone. Your problem was probably amperage with the other one. Watts divided by voltage will give you your amperage. Car had to be running to charge off of the cig lighter. But it also comes with cables to hook up to your car battery directly to give you the 410w max. You get less than half those watts from the cigarette lighter.
     

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