Inverters & Battery Life Questions

[JWA]

Okay I know this is probably an all-too-often asked question but want to have a few real-life user experiences with those who've used inverters with single battery vehicles, IOW no house or second battery bank.

Running a stock 2005 E-350 with 5.4, factory stock 130 amp alternator recently rebuilt due failed internal diodes (at 177K miles) along with an NAPA Legend battery rated at 850/1045 CCA. FWIW my alternator rebuilder says we could upgrade mine to 160 amp output if that would be useful for my anticipated use.

Adding an inverter (minimum of 2500 Watts) to my van would be an occasional use device, it would power nothing more than a Milwaukee 120 VAC Sawzall tool, it draws about 8 amps under a full load. Honestly it would never ever be used for any other reasons. For some reason Milwaukee rates this tool at 13 amps but so far I've not seen it peak much above those 8 amps.

Currently (no pun intended ) this inverter and tool would be used maybe once a month if that. It would be used about 20 minutes, engine running the whole time and after the job was finished to replenish any higher-than-usual amp draw.

I would connect it to the stock starter battery with heavy duty alligator clamps and probably 1/0 cables extending far enough to sit the inverter on the ground while running an extension cord to my work. I work on big trucks so might occasionally be able to tap into their massive chassis multi-battery arrays, the truck engine running the whole time then as well too. It would be stowed away when not in use, possibly in the future a fixed well ventilated location with properly run cables running to the factory alternator, quite possibly the starter's positive terminal.

So then my questions become would my anticipated inverter use in any way damage or shorten the chassis battery life? If it would or its installation would require too much more than I've outlined it would easier to buy a Honda EU2200i generator---money isn't the concern here. My resistance to the generator is it would be vastly under utilized and I don't care to carry fuel inside my van.

There would also be a minor storage space concern BUT if the inverter use would potentially leave me stranded with a failed battery or over-stressed alternator it'll be a no-go.

So looking for any real world experiences with this sort of set up as I've tried describing. Thanks in advance and it's 100% okay to play Devil's advocate for me----we're just spit ballin' so far.

[Twoxentrix]

Originally Posted by JWA

...BUT if the inverter use would potentially leave me stranded with a failed battery or over-stressed alternator it'll be a no-go.

You will undoubtedly get some insightful responses, but I'll just throw this out: If you're able to orchestrate your initial plan (simplicity of Inverter & alligator clip extension cord), and only real concern hinges on the slight possibility of draining your starter battery then a relatively inexpensive safeguard would be adding something like a Noco Jump Start Power Pack to your arsenal of tools/gadgets.

[posplayr]

I think I would look to see if a battery operated sawzall might do what you need. You would not need a 2500 watt inventory to charge it. 300 watt would do.

https://products.bestreviews.com/best-cordless-sawzall

At 8A @120v you are looking at 100A @ 12v with losses. If the 13A rating is due to the inductive load of the saws all motor then the peak is going to be closer to 150A. You might at least need some clamps and if you have even a 50 amp-hr battery it will be close to dead in 25 min of operation. Ideling the engine can get you into an overheating problem with the alternator like happens when a dc-dc charger for demands 60 amps to generate 40A into a LiFepO4 bank.

[JWA]

Originally Posted by Twoxentrix

You will undoubtedly get some insightful responses, but I'll just throw this out: If you're able to orchestrate your initial plan (simplicity of Inverter & alligator clip extension cord), and only real concern hinges on the slight possibility of draining your starter battery then a relatively inexpensive safeguard would be adding something like a Noco Jump Start Power Pack to your arsenal of tools/gadgets.

Good thoughts and its sage advice whatever way I go for my Sawzall power supply. Having the Noco is just a good idea regardless. Thanks for the reminder!

Originally Posted by posplayr

I think I would look to see if a battery operated sawzall might do what you need. You would not need a 2500 watt inventory to charge it. 300 watt would do.

I have a number of Milwaukee NiCd 12 volt batteries still in use, charge them in the vehicle with a special Milwaukee charger for that purpose.

From that POV you're correct a cordless tool would be a good idea but the tools I use are moderately modified reciprocating saws to fit special blades used removing urethane-set windshields. As such there are a few offerings but one is just far too big and expensive, the other is the woeful DeWalt brand---I pretty much loathe them for a lot of reasons. I'd be required to spend upwards of $700 for such a tool with a sketchy past for quality and longer term durability. Their batteries are also sketchy which is another huge concern.

Originally Posted by posplayr

At 8A @120v you are looking at 100A @ 12v with losses. If the 13A rating is due to the inductive load of the saws all motor then the peak is going to be closer to 150A. You might at least need some clamps and if you have even a 50 amp-hr battery it will be close to dead in 25 min of operation. Ideling the engine can get you into an overheating problem with the alternator like happens when a dc-dc charger for demands 60 amps to generate 40A into a LiFepO4 bank.

That's a thought I'll run by my trusted auto electrical genius who just happens to rebuild alternators ect---been using him as needed for almost 30 years now. Thanks for bringing that up!

[posplayr]

So I understand the reasons for not wanting to buy a new portable saw, I want to reiterate, this is also an increased battery capacity solution albeit totally isolated from your Van charging system. So I'll focus on adding battery capacity in the van.

Originally Posted by JWA

That's a thought I'll run by my trusted auto electrical genius who just happens to rebuild alternators ect---been using him as needed for almost 30 years now. Thanks for bringing that up!

Just to be clear what you are looking for is more battery capacity. Why?
1.) The start battery not really designed to be drawing down with a 100 Amp load for 20-25 minutes. Adding a 80 Amp-Hr deep cycle will over double your usable Amp-Hr capacity for $100.

https://www.oreillyauto.com/detail/c...kaAsYfEALw_wcB

If you mount to the frame similar to the factory passenger side mounting you will basically be able to do what you want on a permanent basis without having to use clamps and have the hood popped (although thinking about the alternator overheating issues that may not be a bad idea). Wire the inverter to that battery (through the floor) and you just plugin when you are ready to work. There will be less demand put on the alternator because of the extra reserve.


2.) Even with a marginal increase in alternator power capability ( 130A to 160A) unless you are willing to rev your engine to 2500 RPM it is going to have heat problems trying to make up for this 100Amp load.

Essentially this is a scenario that is almost twice as demanding as a known situation with a 40 Amp DC-DC charger which will burn up a Ford E-350 charging system alternator (under 60 amp demand) if allowed to charge at the max rate while running at idle. With more airflow over the alternator it will not burn up, but sitting at idle does not provide that. So there is nothing wrong with changing diodes, but that is not going to do much for getting rid of the extra heat.

Let's say you leave your van as is and demand 100 amp from your start battery. The alternator is going to try and make up for that. At idle it will not be able to do much (maybe 30 amps safely) and if it could generate 100 amps it would most likely overheat and burn itself up.

In real simple terms, you can contrast adding alternator capacity vs adding battery capacity to the van charging system. If you double the battery capacity (e.g. adding an LA deep cycle) then for the same load you will half the voltage drop across the pair of batteries compared to the single one. Nominally this will halve the alternator amperage demand. Due to I^2R losses, there is now 1/4 of the power losses in the alternator. This alone will almost guarantee you will not burn up your alternator.

So there is a direct 1:4 reduction in alternator power (and heat) for a 2:1 increase in cheap LA battery capacity. You can turn that around and see that even a 40% (square root of two) increase in alternator demand will double the heat generated in the alternator. Recognizing that the alternator is apparently only 50% efficient, you can see there is a real possibility of the alternator heat up escalating rapidly if you put more demand on it.

[daveb]

Originally Posted by JWA

it would power nothing more than a Milwaukee 120 VAC Sawzall tool, it draws about 8 amps under a full load. Honestly it would never ever be used for any other reasons. For some reason Milwaukee rates this tool at 13 amps but so far I've not seen it peak much above those 8 amps.

Currently (no pun intended ) this inverter and tool would be used maybe once a month if that. It would be used about 20 minutes, engine running the whole time and after the job was finished to replenish any higher-than-usual amp draw.

Kind of big (and expensive) but if cost is no issue, why not just buy a Milwaukee MX FUEL power supply?


https://www.milwaukeetool.com/Produc...ply/MXF002-2XC

[JWA]

Originally Posted by daveb

Kind of big (and expensive) but if cost is no issue, why not just buy a Milwaukee MX FUEL power supply?

Wow---that's not only impressive (at least on paper) and certainly challenges my claim "money isn't an issue........" right?

A few reviews show presently its not all it can be and with a quite limited 2 year warranty on the batteries (exclusive of "normal wear and tear......") that's a chunk of Ducat's to throw down. Still, in concept its one cool cat of a job or camp site power supply.

Originally Posted by posplayr

So I understand the reasons for not wanting to buy a new portable saw, I want to reiterate, this is also an increased battery capacity solution albeit totally isolated from your Van charging system. So I'll focus on adding battery capacity in the van.

Just to be clear what you are looking for is more battery capacity. Why?
1.) The start battery not really designed to be drawing down with a 100 Amp load for 20-25 minutes. Adding a 80 Amp-Hr deep cycle will over double your usable Amp-Hr capacity for $100.

Thanks soooooooo much for the further and quite easily understood reasons counter to my thoughts of running an inverter from the van without adding the deep cycle battery and accompanying parts & labor for installation. I greatly appreciate your time explaining it all!

I will for the most part abandon my original thoughts and move towards acquiring a Honda Generator OR devising a way to use my customer's trucks existing battery arrays to power my AC tool via an inverter. I've already used 3 different branded systems to good effect, both with and without their engines running. I'm leaning towards the inverter as it would be by far easiest to stow when not in use. Set up time would vary but "easy" enough to not have too big a negative impact on the decision.

If I could only get my stubborn customers to park their trucks close to 120 VAC none of this would be necessary. In fact for the past 30 years it wasn't even a blip on the workplace radar!

[Weebles]

I don't know if this helps, but my friend is building an off-grid cabin in Wyoming. I built a solar-powered system to run his tools using a 2000W MSW Xantrex Freedom Inverter/Charger powered off a pair of cheap Costco 6V GCs (about 200AH capacity). He runs an older Delta table saw, and also runs an ancient Skil worm-drive saw (back when Skil was a premium brand) either of which must pull a good 15 amps @ 120VAC (1800W). The inverter is powered by a pair of 275W solar panels, so peaks at around 30-amps @ 17V.

An additional data point that will argue for the purchase of a small generator: The draw-down on a single FLA battery with a large power draw will be significant. In my van, I have a pair of 6V GC2 batteries with combined 220AH @12V capacity. I like to run a small 700W electric tea kettle to make coffee. It will pull-down my batteries from 12.8v to 12.0V while heating, then recover voltage a couple minutes after load is removed. I would think the draw-down on a single starter battery might be excessive even with 2/0 cables (though a starter-battery's higher CCA might handle the load better than my GCs do).

[86Scotty]

Originally Posted by daveb

Kind of big (and expensive) but if cost is no issue, why not just buy a Milwaukee MX FUEL power supply?


https://www.milwaukeetool.com/Produc...ply/MXF002-2XC

That is a bad a*s tool. Unfortunately it has a price to match.

Very handy stuff coming out these days.

@JWA, I'd buy a cheap MSW inverter for your purposes, honestly. I don't think there's any risk of challenging your batteries using the tools you propose with a running vehicle. I recommend going cheap on the inverter for this experiment based on your idea of moving it around, which even with great care it will be beat on a little more than a fixed mount inverter in an occasionally used camper like most of us have.

[REF]

I was going to suggest taking a look at the Goal Zero portable power stations, but it looks like they’re even more dough than the MX Fuel, but can be charged directly by a solar panel.
You can essentially put your own “kit” together with a decent 3000W inverter, deep cycle battery and a small portable solar panel for a fraction of the cost, it just won’t be an all in one neatly contained package.