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 > Talk about voltage drop (12v)

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wopachop

Who run bartertown

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Posted: 08/03/21 01:19pm Link  |  Quote  |  Print  |  Notify Moderator

Have the trailer in boondocking mode. Some old batteries and 150w of solar. The batteries are showing 13v. I have a little 300w inverter to charge my laptop and things. 14 gauge wire is feeding the little inverter and the USB panel.

Doesnt that seem weird its dropping below 12v and only pulling 3amps?

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wopachop

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Posted: 08/03/21 01:23pm Link  |  Quote  |  Print  |  Notify Moderator

Should mention the circuit is roughly 15 feet long and i believe 14 gauge wire feeds it. I tapped in and added another couple feet of 14 gauge wire up to the USB panel.

Its been a couple years but im pretty sure im on a dedicated circuit. I might have tapped into the electric awning. Point being i dont think there is any other load besides the 3amps.

enblethen

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Posted: 08/03/21 01:32pm Link  |  Quote  |  Print  |  Notify Moderator

Sounds about right!


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theoldwizard1

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Posted: 08/03/21 02:53pm Link  |  Quote  |  Print  |  Notify Moderator

What brand is that panel meter ?

Some inexpensive meters are known to be off by 10%.

time2roll

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Posted: 08/03/21 03:04pm Link  |  Quote  |  Print  |  Notify Moderator

#14 and 300 watts... is that the fuse? Or is that by design so the inverter will drop out before the fire ensues?


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wopachop

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Posted: 08/03/21 03:22pm Link  |  Quote  |  Print  |  Notify Moderator

Hmm good point. It's that little red cube. Maybe a 150W.

enblethen

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Posted: 08/03/21 03:59pm Link  |  Quote  |  Print  |  Notify Moderator

The meter and LEDs add to the load. There is losses within the unit that draws power.

pianotuna

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Posted: 08/03/21 04:06pm Link  |  Quote  |  Print  |  Notify Moderator

#10 wire would be much better. I would expect 7.5% voltage drop with 15 feet of #14 and the loads.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, soon to have SiO2 batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

wa8yxm

Davison Michigan (East of Flint)

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Posted: 08/03/21 05:33pm Link  |  Quote  |  Print  |  Notify Moderator

300 watts is about 30 amps at the battery 14GA is good for half that at 120 volt and even less at 12 volt due to voltage drop.

Plus there is a voltage drop INTERNAL to the batteries (I do not know how much)

The key to battery/inverter is three fold
One, Keep the leads as short as you can but do not mount the inverter inside the same space as the batteries

Two HEAVY cable for a 300 watt Starter cable works very well and is low cost up to around 750 watts it works well. long about 1000 it might be a bit...er.. anemic

3: for as much of the run tape or wire loom the cables like this ============
Side by side. This is more important on larger inverters.

AND MORE battery never hurts..

DEEP CYCLE batteries work best for House use.
(As opposed to MARINE/deep cycle) note how I use case on those)


Home was where I park it. but alas the.
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after a semi "nicked" it. Still have the radios
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wopachop

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Posted: 08/03/21 06:06pm Link  |  Quote  |  Print  |  Notify Moderator

I'm seeing voltage drop along the wire correct? Not battery sag? The test is during the day with solar hooked up. Only drawing 3amps.

Why dont I see similar voltage drop while on shore power? Pretend the Led display read 14v. When I apply the same 3a load why doesnt the display show 12-13 volts?

I understand that higher voltage sags less. But we are only talking the difference of 12v boondocking to 14v on shore power.

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