Sorry if this has been asked and answered here before, couldn't find anything specific via search...........

2005 E-350 with 5.4 gasser, Newer NAPA Legend 84 month battery, 850/1050 CCA, stock but newly rebuilt 130 amp alternator. (Previous factory original alternator had failed diodes @ about 177K miles.) My alternator rebuilder tells me he could increase the amperage up to 160 amps using my same new case.

I have need to occasionally power a windshield cut-out tool that is for the most part a Milwaukee Sawzall, specs say it's rated at 13 amps (1560 Watts) but a very simple amp/Watts draw test shows free running it's about 7 Amps (900 Watts) at most. The tool does undergo a bit of a load from time-to-time during tough cut outs, bursts of higher power demand for short periods of time. The typical time the tool is actually running almost never exceeds 20 minutes during an installation.

(FYI I just now tried simulating an anticipated heavier load then the free running power demand but it just does not exceed that 900 Watts.)

I'd like to install a 2500 Watt or larger inverter for the infrequent need but want to be sure it would not damage or cause a sudden failure of the alternator or the battery. I would run the engine at idle (650 RPM?) with no high-demand loads like blower motors or headlights on at the same time. The Inverter would initially be powered by good quality alligator battery clamps, eventually going with the Anderson-type power pole connectors.

For the big trucks I work on almost exclusively I could use their on-board battery banks for my inverter but I'm more concerned with my daily driver work truck.

Anyone here have an experience with my guess work potential set-up, any horror stories or things to avoid during installation and/or operation? I'm thinking snow plow operators might have some insight into this, those with campers etc too.

BTW if this same question would get more attention or answers in another FTE sub-forum I'd be glad to know which one.

Thanks in advance to any input!

 

Typically you should use a deep cycle battery with an inverter because lead-acid ones do not handle the drain and recharge cycles as well. However, if this is just occasional use you should be fine. Also, be aware that any amp rating the tool draws is at 120v, so the inverter draw at 12v is 10X the amperage. A tool that draws 7 amps will cause the inverter to pull 70ah from the battery, give or take.

One solution to protect your main battery is to install a deep cycle one in parallel with your main one with an inline battery cable switch. That way you can connect the inverter to the deep cycle battery with the switch off, keeping your main battery safe. When your done and you start the engine turn the switch on to start recharging the deep cycle battery or put it on a battery charger when you get back home. This way cost a bit more but you don't have to worry about draining the main battery or getting stranded.

 

If he keeps the engine idling though, I think his plan will work fine with his factory setup. The alternator you have has good output at idle. So it will share the load with the battery.

I had a old 1980 f150 with the stock 60 amp alternator. When I installed the snowplow on it, it would not even lift the plow up when I hit the button. All I had to do on that setup was to increase the idle speed (it was carbed) and after that it lifted the plow right up, and I ran it like that for several years till I got rid of the truck.

 

When we lost power and my genset crapped out I improvised a 2kW inverter to keep our fridge, deep freezer, home entertainment system and a window ac running for several hours with no ill effects running my truck at idle the entire time. I use that same inverter at work when I'm on the road during the summer to power a blower type fan to help ward away heat stroke.




Take a close look at the size of the inverter battery cables, 0 gauge with jumper cable alligator clamps in order to utilize the full capacity of the inverter, it's required as @alloro mentioned above for current draw. Your one little sawzall should work just fine.

For your power needs I highly recommend d/l an ohm's law calculator for your phone or this link for pc. Makes it simple to calculate load/power requirements as you only need to know 2 of the variables to make a full calculation.

 

Okay much to my expectations more than a few great ideas here---thanks for the input so far-----a few thoughts and/or added info that might be important..........

@alloro Agreed on the DC amp draw, I referenced the AC amps and Watts only because it's something I could easily measure. By my calculations the 70 Amps at 12 VDC would equate to about 840 Watts, do correct me if I'm wrong. My original thoughts were towards a minimum 2500 Watt inverter to have a bit of safety margin.

Also a good thought about possibly needing a deep cycle battery alongside the chassis or starter battery, I'd NOT want to be dead in the water if an inverter would kill or greatly shorten the main battery. Being honest though while it would be a bit more costly up front a gasoline generator would be an easier solution. My only concern there is having to drag it around, storing it on the work truck with fuel in the tank and it being used maybe MAYBE once a month, perhaps even less. At first the inverter seemed like a good idea.

@ Franklin2: Because I work only on big trucks (some of which have their own 3500 Watt inverters already installed) I could possibly use their large bank of frame-mounted bank of batteries saving my vehicle from providing the input VDC. The plan if my van were to be used is keeping it running the whole cut-out time, left idling until the job is finished and then of course the ride home, often 20 or more miles. Since its been mentioned I might be stressing the lead-acid battery a bit more than desirable that becomes a concern. FWIW I do carry a PBT digital CCA tester a few tests after inverter use might give me an idea how much drain I was putting on the battery. Just something to consider.

@RLXXI: Nice set up---out of curiosity what was the total AC amp draw on your inverter as you describe? You have a few inductive loads like my Sawzall and it seems your 2000 Watt inverter handled all that well enough? Have you noticed any degrading of your starter battery or is that something you test during routine maintenance?

Money isn't my problem or issue, the inverter being a first choice only because a generator would be highly under utilized, would sit idle most of the year. FWIW I'd use one of the newer Honda The inverter would also be idle most of the time, perhaps left "loose" with various cable sets so it could be set up on the ground outside the work van, the input cables being run to whatever vehicle would be used for the DC power. I tend to use nothing but better quality fittings etc as I know those can be crucial to such transfer(s) of power.

So any other opinions on this greatly appreciated and deeply considered as I move forward with this project.

TIA

 

You'll notice the power level indicator on the inverter is only 3 of 10 bars usage. I'm sure that went up when the fridge/freezer/ac compressors kicked on. The start up load of that inverter is 4kW to handle that type of surge.

I don't remember the exact numbers on device wattage draw but it handled the loads quite handily, that's where the ohm's law calculator comes in, you input 2 of the known specs and it'll give you everything else so you can calculate inverter size requirement.

Battery is just fine and no it's not something I routinely check other than a visual for leakage/cable end corrosion, (maintenance free isn't just a marketing gimmick) when a battery goes bad it just does and usually with no advanced warning.

 

Thanks for the reply RLXXI !

 

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