Inverter in Vechicle
- Thread starter Big Bob
- Start date
WFK
Senior Something
Nothing wrong with that.
Keep in mind though: A =W/V
At 500 Watts you draw over 40 Amps from the battery, and you can't do that for very long.
Equally important: depending on distance between battery and inverter, you need heavy gage cable. It needs to be sized for voltage drop because the inverter will shut down when the voltage at ITS input goes below the threshold and not when the battery goes below the threshold.
Keep in mind though: A =W/V
At 500 Watts you draw over 40 Amps from the battery, and you can't do that for very long.
Equally important: depending on distance between battery and inverter, you need heavy gage cable. It needs to be sized for voltage drop because the inverter will shut down when the voltage at ITS input goes below the threshold and not when the battery goes below the threshold.
I recently installed a WAGAN 350W (800 surge, modified sinewave) in my truck. I ran a 10ga stranded direct from the + battery lug..about a 5ft run. 8 prolly would have been better but used what I had at hand..remembered later I had some aircraft 9ga. Inverter has it's own external 35A input fuse so I didn't need to do an inliner.
I couldn't see an easy way to run it off an ignition key turnoff. So need to remember to separately turn off. Specs say <0.3A no load but that's enough to drain some small car/truck starter batts fairly quickly.
Among other things it runs a small (200W draw) swamp cooler for my non-AC truck. [yeah..I are a cheap redneck
]
WFK-- 10ga big enough? Or should I double it up?
I think if I'd gone to a 500W or higher I'd mount the inverter under the hood near the batt and run a normal 120V extension cord from it to the cab. Cheaper/easier to work with than DC rated wire. Prolly need to do some waterproofing if mounted up there tho.
I couldn't see an easy way to run it off an ignition key turnoff. So need to remember to separately turn off. Specs say <0.3A no load but that's enough to drain some small car/truck starter batts fairly quickly.
Among other things it runs a small (200W draw) swamp cooler for my non-AC truck. [yeah..I are a cheap redneck
]WFK-- 10ga big enough? Or should I double it up?
I think if I'd gone to a 500W or higher I'd mount the inverter under the hood near the batt and run a normal 120V extension cord from it to the cab. Cheaper/easier to work with than DC rated wire. Prolly need to do some waterproofing if mounted up there tho.
DC wire guage wiring table
Found this table for wire guage needs for DC.
http://www.powerstream.com/Wire_Size.htm
Most tables use resistance per 100ft to calculate heat producing resistance (voltage drop), so with this table use the "Chassis" wiring column for short runs...<10ft or thereabouts.
Subject being corrected, IMO 10ga is adequate with some safety factor for 350W (12V/35A) draw for wire lengths <10ft. 8ga for 500W.
I suggest using stranded wire for ease of routing in vehicles. You also need to locate the inverter where it will get good airflow and not where it'll collect crud. This last is sorta important because 350s up usually have their own case cooling fan..essentially a mini vacuum sucking in crud.
Found this table for wire guage needs for DC.
http://www.powerstream.com/Wire_Size.htm
Most tables use resistance per 100ft to calculate heat producing resistance (voltage drop), so with this table use the "Chassis" wiring column for short runs...<10ft or thereabouts.
Subject being corrected, IMO 10ga is adequate with some safety factor for 350W (12V/35A) draw for wire lengths <10ft. 8ga for 500W.
I suggest using stranded wire for ease of routing in vehicles. You also need to locate the inverter where it will get good airflow and not where it'll collect crud. This last is sorta important because 350s up usually have their own case cooling fan..essentially a mini vacuum sucking in crud.
WFK
Senior Something
After Synap did the work of finding the table 
these are my comments:
"Safe" wire sizes are those that won't burn under specified current load. That current is lower for cables (bundled wires) than for single wires. The entire subject of safety is covered by the National electric Code and includes fusing, etc.
But when one designs for minimizing voltage drop, the game changes because voltage drop can be a tougher constraint if the voltage is low to begin with. (12VDC is LOW.) Or hundreds of feet to a submersible pump is subject to the same considerations...
From Table: AWG10 has 1 Ohm/1000ft or 1 Milliohm/ft
At 40 Amps, you get 40 mV drop / ft
Double for TO and FROM.
Assume distance between inverter and battery = 10 feet.
double for wire length = 20 feet
drop at 40 A = 800 Millivolts ( .8 Volts)
If inverter trip-out is at 10.5 V (normal value), it will trip out with battery still at 10.5 + 0.8 = 11.3 Volts.
It is basically up to you if that is acceptable or not.
But inverter trip-outs on starting currents are a pain!
Of course, if you double up AWG 10 you cut the drop in half. That is sometimes preferrable to the use of heavier wire.
At 40 Amps you also run into fuse (size) problems.
I would use automotive CBs instead of a fuse.
----------------------------------------------------------
The point is that with a long DC run between battery and inverter you can limit unduly what you can take out of a battery.
Also that is why really big inverters are often sized for 24 or 48 Volt systems.
these are my comments:
"Safe" wire sizes are those that won't burn under specified current load. That current is lower for cables (bundled wires) than for single wires. The entire subject of safety is covered by the National electric Code and includes fusing, etc.
But when one designs for minimizing voltage drop, the game changes because voltage drop can be a tougher constraint if the voltage is low to begin with. (12VDC is LOW.) Or hundreds of feet to a submersible pump is subject to the same considerations...
From Table: AWG10 has 1 Ohm/1000ft or 1 Milliohm/ft
At 40 Amps, you get 40 mV drop / ft
Double for TO and FROM.
Assume distance between inverter and battery = 10 feet.
double for wire length = 20 feet
drop at 40 A = 800 Millivolts ( .8 Volts)
If inverter trip-out is at 10.5 V (normal value), it will trip out with battery still at 10.5 + 0.8 = 11.3 Volts.
It is basically up to you if that is acceptable or not.
But inverter trip-outs on starting currents are a pain!
Of course, if you double up AWG 10 you cut the drop in half. That is sometimes preferrable to the use of heavier wire.
At 40 Amps you also run into fuse (size) problems.
I would use automotive CBs instead of a fuse.
----------------------------------------------------------
The point is that with a long DC run between battery and inverter you can limit unduly what you can take out of a battery.
Also that is why really big inverters are often sized for 24 or 48 Volt systems.