Fuel consumption while idling engine to save house-battery life.

[BigT]

I work a job with insanely long, fatigue-inducing hours (5.25hrs AM - 4.75hrs split/break - 5.0hrs evening & 268 miles driven), and have started sleeping in my van, not only overnight at work to avoid commuting, but also during my split in the middle of the day, in a desperate attempt to fight off the inevitable sleepiness during my shift that could result in a catastrophic crash and multiple injuries (not to mention losing my commercial license and going to prison).  

The problem is, I don't have a very high Amp hour capacity to play with (75Ah AGM) and I fear, even though my usage is fairly low (Approx. 12Ah/day max), that over time I'll kill my battery.  
I run a CPAP machine while sleeping (no humidifier) and leave my iPhone plugged in/charging while listening to classical music to help me sleep.
I'm told to expect approx. 0.5 - 1.0 Amp draw with the CPAP.  

I can't find it now, but a while ago I saw a thread here where someone was asking how much fuel you burn while idling the engine in your car/van to save the house batteries.  Tonight I found this link with some really good, of correct, answers in it.  

https://www.quora.com/How-much-gas-does-a-car-burn-per-hour-while-idling

One guy's reply is ridiculously complicated and I think he's just trying to show off, but if he's correct, the consumption is very little. 

Of course there are several factors that can have an effect on the final numbers (engine size, idle speed, altitude, etc.), but the general consensus is that it doesn't take very much at all, which makes me very happy. 

My plan/hope is to use the house-battery *without* the assistance of the engine for the 8 hours at night, but idle the engine during my 4-5 hour nap in the middle of the day.  That way I'll really only be taxing the system with 8 +/- unassisted Ah a night.   
I also have a 190W solar panel, so hopefully between the idling, solar, and possible 1 hour round-trip home-and-back highway drive in the afternoon to feed my cat, the system will stay happy.  (I'm hoping SternWake will chime in after reading this paragraph).  

I only need to do this for two weeks, then I go back to sleeping 10+ hours at night and working an 8-hour/80 mile day like everyone else.  
My idling engine will not bother anyone as I will be in a secluded, sunken parking lot, surrounded by idling vehicles and busy mechanics.  

Does this sound doable to the electrical gurus on the site?

 

[WheelEstate USA]

Is there somewhere you could plug in a battery charger and be out of the way of the mechanics??

 

[NeedAnEscape]

I wouldn't want to sleep in an idling vehicle unless it's exhaust exited above the roof. Since you are staying in your work parking lot, ask if there is somewhere you can plug in an extension cord.

 

[SternWake]

BigT, this is unnecessary with your stated consumption.

At only 10 AH depleted overnight, the battery is only going to accept ~8 amps maximum after 1 minute at absorption voltage.
Your 190 watts of solar can make that, so you would be essentially idling for no purpose, except to run AC or heat.

My northstar continues to impress me as long as it can be returned to full regularly and a a high amp rate  from when most depleted regularly.




You already paid for the Solar system, why then pay for gas so you can not have to use it?

I bet that Northstar AGM could be drawn down to 11.6 volts resting, and still crank your engine to life easily, over 45 degrees F ambient.

My 90 Ah NS AGM has cranked my v8 engine at 11.6v, 64Ah from full, first thing in the morning  before sunrise, after streaming movies all night.

The battery has a job to do.  Its expected float life, at 77f, if NEVER discharged, and kept at the precise float voltage of 13.6v is 12 years.

I view the batteries like tires, they have a shelf life at 5 years no matter how little they are used.  Might as well use them right?

Just recharge it right and it will treat you right for a long long time.

---

I also have some recent alternator temperature data on my full size van., Idling at 32 amps total output vs driving at 25 to 40mph at 55 amps output.

It was 30 degrees cooler at 25 to 40 mph producing 23 amps more juice.  Heat is what kills alternators.  My max reading was after 30 seconds max output at idle, parked.  It shot up 20 degrees  to 159.5 f when I ended test and turned off  55 amps of lighting and blower loads.
220F is the danger zone

How applicable this is to a ford transit is unknown but obvious parallels can be drawn.

If you are going to idle the engine, don't do it just to recharge.  This is folly except in emergency situations.

Work the battery.  It is your servant, and you pay it well which will keep it happy to serve you.

Now if you were to cycle it to 50% nightly, you'd have to pay it a it more and it would still eventually quit.

 

[Canine]

I started falling asleep when I was driving in my commercial truck. I absolutely had to pull over and catch a power nap. I did this several times until one day the wind was just right and instead of being refreshed after 20 minutes, I woke up sick several hours later. While I can't say definitively what happened, I don't think it is a reach to say I got a touch of CO poisoning.

If you sleep enough with the engine running, it will catch up to you. Be careful.  

 

[BigT]

BigT, this is unnecessary with your stated consumption.

At only 10 AH depleted overnight, the battery is only going to accept ~8 amps maximum after 1 minute at absorption voltage.
Your 190 watts of solar can make that, so you would be essentially idling for no purpose, except to run AC or heat.

You already paid for the Solar system, why then pay for gas so you can not have to use it?
I view the batteries like tires, they have a shelf life at 5 years no matter how little they are used.  Might as well use them right?

Just recharge it right and it will treat you right for a long long time.
Work the battery.  It is your servant, and you pay it well which will keep it happy to serve you.

I can't say I completely understand the line about "accepting ~8 amps after 1 minute at absorption voltage", but I am glad to hear my system should be able to handle 8 hours of unassisted, nighttime use and 4 or 5 hours of midday, solar-assisted, use.  Maybe it's time I picked up one of those digital displays that plug into the charge controller so I can monitor exactly what the battery and panel are doing.  Right now all I have are the three little lights on the CC that tell me if the battery is fully charged or not, and those lights never change. 

I should also probably learn what exactly my system is doing and how much I can run.  I'm fairly clueless about electrical and solar systems.  

I keep trying to remind myself that I bought this expensive AGM battery to use it, and not to be a slave to it.  One of these days I really need to stop worrying about hurting it so much and get some use out of it before it dies, unused, of old age.  

It should be noted that we're supposed to be, and have been, getting some cloudy weather here, so I'm a little concerned that I won't get any help at all from the solar panel for a while.  If that's the case, I'd imagine idling might become a necessary option given I plan to sleep in the van 4 nights and afternoons a week (Mon. thru Thurs.) for the next two weeks.

 

[BigT]

I started falling asleep when I was driving in my commercial truck. I absolutely had to pull over and catch a power nap. I did this several times until one day the wind was just right and instead of being refreshed after 20 minutes, I woke up sick several hours later. While I can't say definitively what happened, I don't think it is a reach to say I got a touch of CO poisoning.

If you sleep enough with the engine running, it will catch up to you. Be careful.  

Hmmm...  I'm not really very well versed on the dangers of CO getting into the van while it's idling, windows up and doors closed.  
I do know that the parking lot I'll be in tends to get quite windy day and night, so hopefully it blows the exhaust away from me.  

I've also considered putting some sort of thermal ducting (tube/hose) around the tailpipe and running it vertically up the side the van, securing it with a bungie to the roof rack so the fumes float harmlessly up into the air.  

Unfortunately, I transport passengers so I don't have the option to pull over for a cat-nap.  I have to be sure to get enough sleep/rest *before* starting out.  
Given my 15 hour splits, I plan to sleep in the lot at night to avoid having to commute morning and evening, thus giving myself that much more time for sleep.  
I don't always have a lot of luck napping in the middle of the day, and sometimes wake up feeling worse than when I went to sleep, but I'm hopeful it will reduce the chances of dangerous fatigue.

 

[Canine]

Oh, I should give a little more context on my date with carbon monoxide. My truck's exhaust didn't vent above the cab, out the side, or out the back. It was a stubby length that vented just past the cab directly under the box of the straight truck. Because of how the exhaust was routed, with no wind the fumes floated directly up and into the cab. Even on the new truck, the cab was no where near tight enough to keep fumes out.

When I parked, I made sure I faced the wind, but the wind doesn't always blow the same way. One morning it decided to change just enough to help push the fumes toward the cab allowing more fumes than normal to penetrate.

 

[BigT]

It sounds like getting a carbon monoxide alarm and setting it on the floor of the van would be a good idea.
Just for the days when there's no sun.

 

[SternWake]

BigT, a lead acid battery discharged to 80% or above, cannot accept much charge current. In this state of charge range, time at absorption voltage is required, huge charging amp availability will not be utilized as the battery can simply not accept it.

When an 'unlimited' charging source, like a cold alternator, is allowed to make everything it can in its job to bring the battery to absorption voltage, a 90% battery will accept about 70 amps for a few seconds, and this number of amps will quickly taper down to the single digits, likely within a minute.


So if you were 10AH from full, at noon, and decided to start your engine, the amperage required to hold 14.x would be in the single digits within a minute. Your 190 watts of solar panel could make this much for a few hours either side of solar noon on a sunny day.

There is also the high probability that your ford's voltage regulator would seek only mid to high 13's, which would elongate the absorption stage considerably making the solar more effective as it should seek and hold at least 14.4v for a period of time.

It sounds as if you are willing to burn hundreds of dollars in gas idling in a bid to extend the life of a 300 dollar battery without realizing that in daytime, your solar could very well do more than your alternator and idling to recharge would/could/might be choosing the less effective of the two available charging sources, and burning gas to do so, with that CO risk involved as well.

No way would I ever Idle the engine just to recharge a 90% charged battery. This is simply insanity, especially when one has 190 watts of solar on the roof and uses very minimal battery battery capacity.

And as far as blinking lights on your solar controller goes in indicating a fully charged battery, do not fall into believing faithfully, this trap.

An AGM battery can ONLY be determined to be fully charged when it can only accept 0.5% of its capacity at absorption voltage. Anything else is a guess.

The Northstar AGM fully charged rested voltage is 13 volts or higher. Most flooded batteries are in the 12.8v range. When your Northstar reads 12.8v rested, it is around 85 to 92% charged, but any 'indicator, is going to see 12.8+ and proudly yet delusionally display a 100% charged battery.

A voltmeter is not a battery monitor, but it does give a good clue as the general state of charge range of the battery, but less so during actual charging or discharging .
Get yourself a simple voltmeter and if you idle just to recharge when your battery is above 12.6v, I am going to hunt you down and slap you upside your anal retentive head!



Now 12.2v is another matter.

http://www.amazon.com/HappyPrimeDay...TF8&qid=1456093489&sr=8-18&keywords=voltmeter

 

[BigT]

Thanks, SW, that makes more sense to me now....  And for the record, I'm not considering idling the engine in an attempt to save the $300 battery.  I'm not *that* anal.   
I simply didn't realize the solar would/could produce enough power to replenish the system after discharging the battery for 8 hours in the evening, and then an additional 4 or 5 hours the following afternoon without starting the engine, esp. given I plan to do this 5 nights/days in a row for 2 weeks.  
It's supposed to be cloudy this week with a chance of rain.  

Just to be safe, I purchased a CO detector/alarm in case there isn't enough sunlight during the two weeks I'll be there.  
From what I've read, the cost in gasoline would be so tiny as to be laughable.  
I'll bring my volt meter to work, assuming it's functioning properly, and take a few readings straight off the battery.  

I'm still not completely sure what the draw from the CPAP is.  I bought one of the meters with the clamps that you recommended on Amazon, but I'm not sure where on the CPAP cord to connect it.  There are two large, black cylinders built into the cord that house, I-don't-know-what, and depending on where I attach the Amp meter, I get a different reading.  
I'm also not certain there isn't something wrong with the meter itself.  When I attach the clamp I get a reading for a split second, but then it goes back to zero, even with the clamp firmly in place.  :huh:

With the CPAP set at 7.0 cmH2O starting rate, I get 4 different readings (between the 12V plug and first cylinder, .203 - between the two cylinders, .167 - closer to the CPAP but still between the two black cylinders I get .96...  between the second cylinder and the CPAP I get a reading of .104)  
I have the meter set at 2.0A, though in the picture it shows 20 Amps.  In either case, the reading quickly returns to zero after climbing to a max amount.

 

[SternWake]

The clamp meter needs to go over only one wire, not both together.


Separate the two wires after the ciggy plug just enough to get the clamp in between the wires

 

[BigT]

Oh wow, that's going to be a neat trick.  There's less than 3/4" to play with.  

I'll see what I can do though, thanks.

Any idea what those big, black cylinders are for?  Can I connect the clamp past them, closer to the machine? 
There's a lot more wire to work with further from the plug.

 

[SternWake]

Anywhere you can get at the one single wire, you can measure the current.

Perhaps start a thread and post the Cpap model number and the amp consumption and the battery voltage, or just multiply the voltage and amperage for a wattage figure. You have the tools to definitively answer a lot of people's questions about how much one of these actually consumes, a question from your own not so distant past.

If you can't get the clamp over one wire easily enough, turn off everything and put the clamp over a battery cable.

You can measure how much current your starter draws, and how much juice your alternator returns into the battery at that point in time.

Do some experimenting, turn on lights, blower motor, rev the engine, ect. It will all help you to understand DC electricity.

 

[drysailor]

Oh wow, that's going to be a neat trick.  There's less than 3/4" to play with.  

I'll see what I can do though, thanks.

Any idea what those big, black cylinders are for?  Can I connect the clamp past them, closer to the machine? 
There's a lot more wire to work with further from the plug.

BigT, if you can get your hands on a spare ciggy plug & socket, you could wire them together using a foot or two of separate wires, and either clamp your ammeter pickup on one of them, or just cut one wire in the middle, strip the ends, & attach your regular (current) test leads to those ends. Just in my own experience, low current DC clamp-ons are not always that accurate anyway. The black 'cylinders' you describe are likely chokes/coils, and are there to help filter noise along the line. If you're getting a good reading, it will be the same on either side of them.

 

[SternWake]

I was concerned by the low current reading accuracy on my clamp meter, so I tested a single t10 LED bulb with a DMM inline in the circuit and my craftsman Model # 82369 clampmeter over the circuit, and they read within 0.01a of each other, (0.07 and 0.08a ) So I kind of forgot about the low current inaccuracies possibilities.  Do be sure to hold clamp meter next to wire, and zero it, then clamp it over a single wire. And don't be afraid to read its manual either. Initially  clamping it over both wires indicates you did not.


The Cheaper shunted ammeters I have wired up have had more issues accurately reading low currents than my clamp on meter.

Most digital multimeters are limited to 10 amps when hooked inline to measure amperage, so unless one knows their device cannot exceed that amount it is better to not try, as it might not just be the tiny interior fuse that blows.

I'd not be cutting any copper to test current, and certainly not adding another ciggy plug and receptacle in the circuit.  If one is worried about current consumption then the extra resistance of a butt connector or a ciggy plug and receptacle is kind of self defeating.

Splitting a 2wire lead to get a clamp on meter over one of them can be done so easily, I can do it with my fingers.  My recommendation to do it after the ciggy plug was only to increase accuracy by a smidge.  If there is not enough room, then do it on the other side of the plug.

And play with the meter to get familiar with it, and the electrical draw of all your devices.  Put it over a main battery cable and turn things on and off and check the results.  Put it over the wires to and from the solar controller.  Experiment to learn.  The DC clamp n ammeter might be the most enlightening and convenient of measuring tools at your disposal as one does not need to open the circuit to test the amperage.

The AC/DC clamp meter can also test AC current, but getting the clamp over the hot or neutral wire is usually more difficult than DC systems.

They sells these to make it easier:
http://www.amazon.com/Extech-480172...&qid=1456344595&sr=1-3&keywords=Line+Splitter

I should get one, but I will likely just make one with an old extension cord.

 

[BigT]

I haven't done any test yet, but I did spend Tuesday, Wednesday and Thursday nights and afternoons in the van. So far so good.
I'm planning to spend all of next week in it while I'm on this crazy schedule.

 

[blars]

Cheap meters may be able to handle 10A, but their leads won't. Thick insulation over thin wires is normal for them.

 

[Mobilesport]

You said that you would be driving a hour a day to go feed your pet , I would think that 
in itself would be enough to charge your small battery .
On top of that you have a solar panel .

 

[BigT]

This week I stayed away from home for 5 days.  Today there is no sun.   :-/