Ideally I'd install solar but this is for occasional recharges, not daily.
Edit: Solved this. Even my cheap inefficient Chinese generator only uses about $12 in gas to run for six hours, so I will prefer that. But the inverter uses about as much current as idling with the A/C on, headlights, and radio, so it should be safe for occasional use this way.
* This post was last edited 01/04/21 07:59am by SlowBro *
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The inverter to converter makes the most sense, if it won't burn up the alternator. But I'm finding the charge rate of the converter may require a lot of hours of car idling. I guesstimate 6 hours on charging from 50%.
Ed - on the Central Oregon coast
2018 Winnebago Fuse 23A
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time2roll wrote:
If the converter actually puts 45 amps into the battery you might overload the inverter. A single test will confirm with no harm. Of course the inverter would need to be hardwired to the vehicle start battery. And inverters don't really like heat under the hood. If you plan to do this while idling stationary the alternator may not keep up. Otherwise you are good to go. No harm to the alternator.
If the converter actually puts 45 amps into the battery you might overload the inverter. A single test will confirm with no harm. Of course the inverter would need to be hardwired to the vehicle start battery. And inverters don't really like heat under the hood. If you plan to do this while idling stationary the alternator may not keep up. Otherwise you are good to go. No harm to the alternator.
I am fairly certain it doesn't put all 45 amps into the battery. It's a three-stage converter so it has some smarts about sending the right amount of current into the battery. Lead-acid charge rate (I read somewhere) is C/6 to C/8, and group 24 batteries are 80AH, for a charge rate of between 10-13A on DC, to about 1-1.5A on AC, back to about 14-21A on the alternator.
Couldn't find solid numbers on what the alternator is capable of when idling but I think I saw it's 10% of full rated output, so I may have to jam a stick against the gas pedal to rev it up a little while charging.
Inverter runs from inside the cabin, no overheating.
I'm hoping to try it this week to be sure it doesn't scream.
on the converter brand and charging profile and the 12v wiring you may not get 45 amps for long or only half that amount. A good converter could put a solid 45 amps in for maybe 30 minutes before the battery acceptance rate causes the amps to begin tapering off.
If you were buying a separate charger a 10 amp rated unit would work perfectly good.
time2roll wrote:
A 45 amp converter is fully capable of putting 45 amps into the G24 battery. Although depending
on the converter brand and charging profile and the 12v wiring you may not get 45 amps for long or only half that amount. A good converter could put a solid 45 amps in for maybe 30 minutes before the battery acceptance rate causes the amps to begin tapering off.
If you were buying a separate charger a 10 amp rated unit would work perfectly good.
A 45 amp converter is fully capable of putting 45 amps into the G24 battery. Although depending
on the converter brand and charging profile and the 12v wiring you may not get 45 amps for long or only half that amount. A good converter could put a solid 45 amps in for maybe 30 minutes before the battery acceptance rate causes the amps to begin tapering off.
If you were buying a separate charger a 10 amp rated unit would work perfectly good.
That’s good to know. The inverter does 800W continuous, so 45A at the converter x 14V and at 80% efficiency, that comes to 787W at the inverter. Mighty close.
If I do use the 6A car charger I have now it’d be a lot more polite.
The PDF references another document for more details on the charge profile, that I’ll have to check out tomorrow.
https://wfcoelectronics.com/wp-content/uploads/2020/11/8900-Series-Manual-Updated.pdf
Sitting in a car idling with the A/C on, radio going, lights on, uses about the same amount of current the inverter would use, and those kinds of conditions are seen regularly. I believe I should be fine.
https://www.aa1car.com/library/electrical_amp_loads.htm
The inverter is too small IF the converter will go to bulk charging mode.
The WF-8945 draws 780 watts or 11.6 amps @ 120 volts, when running flat out.
11.6 amps @ 120 volts = 116 amps @ 12 volts.
Sizing the inverter suggests that 1000 watts might be a better fit.
C/8 is the acceptance rate of a lead acid battery at 85% state of charge. If it is at 50% that may be a LOT higher.
Most alternators have a duty cycle of 2/3, so if the battery bank is "hungry" the alternator may let out the magic blue smoke, with the caveat that the cables to the inverter are thick enough to handle that much current.
On the other hand, WF converters are FAMOUS for not going into bulk charging mode. In that case the 800 watt inverter would not over load, nor would the alternator fail.
It is far better and probably cheaper to use a dc to DC converter between the alternator and the battery bank. That way charge current may be set where you want it.
Do a short time test, preferably with the house batteries cycled to 50%.
If the voltage drops to 12.7 on the engine battery STOP the test.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
Most newer model vehicles are smart enough to not over-tax the alternator.
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
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Most stock OEM alternators are designed to put out big amperage for a few minutes right after start up then drop back to a much lower output.
Also, were is the inverter? You mention in the "cabin" but does that mean in the vehicle or in the trailer cabin?
Be prepared with a jump pack if you try this (or at a site with shorepower) as you could find your starter battery dead as the inverter drags it down.
Once you get past the inverter of appropriate size, no issues charging...at that point it's no different than being plugged into shore power.
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SlowBro wrote:
Inverter is a WF-8945. Charge profile is on page 7 of this PDF. Charge current isn’t listed, but the circuit branch is I believe only 30A, which the inverter can handle just fine.
The PDF references another document for more details on the charge profile, that I’ll have to check out tomorrow.
https://wfcoelectronics.com/wp-content/uploads/2020/11/8900-Series-Manual-Updated.pdf
Sitting in a car idling with the A/C on, radio going, lights on, uses about the same amount of current the inverter would use, and those kinds of conditions are seen regularly. I believe I should be fine.
https://www.aa1car.com/library/electrical_amp_loads.htm
Inverter is a WF-8945. Charge profile is on page 7 of this PDF. Charge current isn’t listed, but the circuit branch is I believe only 30A, which the inverter can handle just fine.
The PDF references another document for more details on the charge profile, that I’ll have to check out tomorrow.
https://wfcoelectronics.com/wp-content/uploads/2020/11/8900-Series-Manual-Updated.pdf
Sitting in a car idling with the A/C on, radio going, lights on, uses about the same amount of current the inverter would use, and those kinds of conditions are seen regularly. I believe I should be fine.
https://www.aa1car.com/library/electrical_amp_loads.htm
![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/rolleyes.gif "rolleyes")
I know that this is/has been done by quite a few "members" of this forum, BUT, do you realize that this is the same thing as using a "cannon" to swat a fly?
745W = 1 HP..
Your gonna "idle" a large vehicle engine for hrs on end to do something that can be done with a very small portable gen..
One should also realize that the alternator on said vehicle is at MINIMAL charging when engine is at idle.. The alternator should be operated ABOVE idle speeds when drawing a lot of current (as in attempting to charge via a inverter), otherwise you do risk running your starting battery down in the process.
Most car alternators are designed for INTERMITTENT heavy charging, they are compact, have the voltage regulator and the diodes built in, that package gets pretty darn hot under normal use, heat buildup is the enemy..
Getting back to the 1 HP.. depending on size of your engine, you are most likely going to use more fuel than you would with a small purpose built inverter gen. Small gens sip fuel, less than a PINT per hr, larger vehicle engines can consume GALLONS per hr at idle
Your gonna put a lot of idle time on a very expensive vehicle engine and transmission which if it breaks down is going to leave you somewhere that you don't want to be and it will cost you many times more to repair than throwing away a small gen.. Excessive idling also can be very hard on the emissions systems and if a Diesel, something called "wet stacking" can happen and be harmful and shorten the life of the engine.
I personally would never intentionally do this to any of my $50K trucks, too expensive to replace a truck, too expensive to replace/repair engine and transmission (a short block can cost as much as $10K just for the block and transmissions can cost $5K not including labor).. Too expensive and difficult to troubleshoot modern vehicle computerized systems (most mechanics charge at a min of $150 per hr now days)..
Just because it has been or is being done, doesn't mean that it is a good idea to do it.
Buy a small gen and or solar, instead of cobbling up some half baked idea.
2011 Keystone Sprinter 323BHS. Retired Master Electrician. Retired Building Inspector.
All Motor Homes are RV's. All RV's are not Motor Homes.
Gdetrailer wrote:
I know that this is/has been done by quite a few "members" of this forum
I know that this is/has been done by quite a few "members" of this forum
Oh sorry, I searched before asking and couldn't find others doing it. Maybe my search skills are off.
Gdetrailer wrote:
Your gonna "idle" a large vehicle engine for hrs on end to do something that can be done with a very small portable gen..
Your gonna "idle" a large vehicle engine for hrs on end to do something that can be done with a very small portable gen..
I do have one of those cheap and inefficient Chinese generators and my van uses less gas per hour idling, despite having a larger engine.
Gdetrailer wrote:
Most car alternators are designed for INTERMITTENT heavy charging
Most car alternators are designed for INTERMITTENT heavy charging
Oh then that's perfect. I have in mind intermittent use, otherwise I would be buying solar.
pianotuna wrote:
The inverter is too small IF the converter will go to bulk charging mode.
The WF-8945 draws 780 watts or 11.6 amps @ 120 volts, when running flat out.
The inverter is too small IF the converter will go to bulk charging mode.
The WF-8945 draws 780 watts or 11.6 amps @ 120 volts, when running flat out.
780 watts at 80% efficiency and 14.4V = 43.3A which is in line with the rating on the plate.
Wouldn't that be for everything though? Lights, accessories, and battery? The branch for the battery is 30A so I can't see how it'd be more than that. Unless the branch circuit isn't where the battery is plugged in... I'm not near the RV at the moment to check.
pianotuna wrote:
Do a short time test, preferably with the house batteries cycled to 50%.
If the voltage drops to 12.7 on the engine battery STOP the test.
Do a short time test, preferably with the house batteries cycled to 50%.
If the voltage drops to 12.7 on the engine battery STOP the test.
Good to know.
You probably already know this, but it is important enough to repeat.
-Speak
It's just Mrs. SpeakEasy and me now (empty-nesters). But we can choose from among 7 grandchildren to drag along with us!
2014 F-150 Super Crew Short Bed 3.5L Ecoboost
2014 Flagstaff Micro Lite 23LB
valhalla360 wrote:
Is this a high output 150amp alternator or the stock alternator?
Is this a high output 150amp alternator or the stock alternator?
Sienna stock alternator is rated at 150A.
valhalla360 wrote:
Also, were is the inverter? You mention in the "cabin" but does that mean in the vehicle or in the trailer cabin?
Also, were is the inverter? You mention in the "cabin" but does that mean in the vehicle or in the trailer cabin?
Vehicle cabin.
valhalla360 wrote:
Be prepared with a jump pack if you try this (or at a site with shorepower) as you could find your starter battery dead as the inverter drags it down.
Be prepared with a jump pack if you try this (or at a site with shorepower) as you could find your starter battery dead as the inverter drags it down.
Good to know. I was told above to watch that voltage stays above 12.7.
valhalla360 wrote:
Once you get past the inverter of appropriate size, no issues charging...at that point it's no different than being plugged into shore power.
Once you get past the inverter of appropriate size, no issues charging...at that point it's no different than being plugged into shore power.
Yeah, that's what I thought. Was criticized above for "reinventing the wheel" when I thought, surely someone somewhere has done this already and I just missed it in my search.
SpeakEasy wrote:
Do NOT under any circumstances, connect the inverter through your cigarette lighter port.
Do NOT under any circumstances, connect the inverter through your cigarette lighter port.
Yes indeedie. The inverter has ring terminals for the battery.
As mentioned above, an alternator at idle generates very little power beyond what it takes to operate the vehicle.
It would be much faster and cheaper to get a 2000W inverter generator to do the job. The expense of a $500 Predator is a drop in the bucket compared to the wear and tear on your car.
John & Kathy
2014 Grand Design Reflection 303RLS
2014 F250 SBCC 6.2L 3.73
2112 wrote:
Can you get your vehicle close enough to the house battery to use jumper cables? That's how I do it.
Can you get your vehicle close enough to the house battery to use jumper cables? That's how I do it.
Per this battery manufacturer, alternators direct connected (using battery cables or jumper cables) are not designed to charge batteries, only maintain them. Also, I recall an Interstate battery tech telling me the same.
But inverters are common, provided I get the sizing right, engine RPMs, all that.
Idling cars are also common, and running the headlights, A/C, and radio uses about the same amount of current as the inverter would.
I feel pretty safe doing this occasionally. Six hours of idling every six months or year.
2112 wrote:
Most newer model vehicles are smart enough to not over-tax the alternator.
Most newer model vehicles are smart enough to not over-tax the alternator.
That's good to know. Do they have temperature sensors to detect overheating?
* This post was edited 01/04/21 07:41am by SlowBro *
Not clear but that "30a" could be the converter's 120v spec as opposed to 50a like in a bigger RV.
As mentioned earlier you can do the thing when stationary so that the inverter is clamped to the car battery with short fat wires, hanging outside the engine compartment away from the heat, with the hood up and engine idling. But you must use an inverter that can handle the charger, and a charger that only pulls what the car can supply to the inverter while maintaining its voltage.
Doing this while driving means using fatter and longer wires routed somehow to get the inverter away from the engine heat. You can get the long 120v wire back to the trailer where the charger would be close to the RV battery though, if you rig it so it stays off the road.
What happens is when the car system is overloaded, the car's voltage sags. You can find what it can do by trial and error if you had a charger with amps settings, such as a Vector with 35, 20, 10 amp settings.
I was able to run at 35 amps of charger with a 1000w MSW inverter with the 2003 Chev truck idling, but higher amps caused the truck's voltage to fall off. Don't forget to turn off the car's blower etc, which uses some that you want for the inverter.
I also can run a Vector at the 20 amp setting with a 400w MSW inverter that runs at 320w.
">]
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Yeah, I'll stick to the cheap genny--but feel comfortable knowing that if for some reason I can't use the genny, using it on the van once in a great while SHOULDN'T blow up the alternator.
Thanks all!
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BFL13 wrote:
You can't run the 45 amp converter at 45 amps from an 800w inverter. First the inverter will have a continuous rating of maybe 600w.
You can't run the 45 amp converter at 45 amps from an 800w inverter. First the inverter will have a continuous rating of maybe 600w.
Its continuous rating is 800W.
BFL13 wrote:
Not clear but that "30a" could be the converter's 120v spec as opposed to 50a like in a bigger RV.
Not clear but that "30a" could be the converter's 120v spec as opposed to 50a like in a bigger RV.
The user manual says the branch is 30A DC, but that may not be for the battery. It's unclear.
Thanks for the picture and confirmation! That's more-or-less what I had in mind.
QCMan wrote:
If you are only going to charge the battery once or twice a year why don't you just take it home and put a battery tender on it?
If you are only going to charge the battery once or twice a year why don't you just take it home and put a battery tender on it?
It's a long story and I don't want to derail the thread. Let's stick to the tech, and I believe my problem is solved.
Thank you.
A good set of battery jumper cables while parked close to the rv will do the trick.
H/R Endeavor 2008
2013 Ford Edge toad
Full Timers
YC 1 wrote:
Sure seems like a long road to get there on with lots of twists and efficiencies.
A good set of battery jumper cables while parked close to the rv will do the trick.
Sure seems like a long road to get there on with lots of twists and efficiencies.
A good set of battery jumper cables while parked close to the rv will do the trick.
I had that thought as well, but...
SlowBro wrote:
Well, maybe nevermind. I found my cheap Chinese generator's manual, and the rated gallons per hour is 0.47 which is much lower than I thought. Even if the number is really twice that it's only about $12 to run for six hours, which isn't enough of a difference to justify using the van.
Yeah, I'll stick to the cheap genny--but feel comfortable knowing that if for some reason I can't use the genny, using it on the van once in a great while SHOULDN'T blow up the alternator.
Thanks all!
Well, maybe nevermind. I found my cheap Chinese generator's manual, and the rated gallons per hour is 0.47 which is much lower than I thought. Even if the number is really twice that it's only about $12 to run for six hours, which isn't enough of a difference to justify using the van.
Yeah, I'll stick to the cheap genny--but feel comfortable knowing that if for some reason I can't use the genny, using it on the van once in a great while SHOULDN'T blow up the alternator.
Thanks all!
![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/smile.gif "smile")
Yep!
At least you do now realize the gen you already have will use far less fuel.. A very smart move for this application.
As far as "blowing up" your vehicles alternator, you most likely would not have done that, but just drives me nuts that folks think it is efficient to use the vehicle engine/alternator/drive train for a charging application like this as an inexpensive "substitute".
Break your vehicle just once and the cost to repair will be many times more than your portable gen.
Besides, using such an oversized engine in an underutilized mode like 1 HP of engine really flies in the face of being "Earth Friendly" when it comes to using considerably more carbon based fuels for no real good reason (and NO, I am not a "tree hugger").. Just pointing out an "oxymoron" which is counter culture to todays modern tree hugging society.
Gdetrailer wrote:
At least you do now realize the gen you already have will use far less fuel..
At least you do now realize the gen you already have will use far less fuel..
No it uses far more, because it's not an inverter genny. It's a cheap inefficient Chinese genny. Uses at least 50% more gas per hour, maybe as much as 300% more. My car uses about 0.25gph idling but the rating on the genny at half load is 0.47gph, and if that's overly optimistic it would be even worse. The RV would only need half the genny load so maybe it is only 0.47gph.
However, the cost difference for such a small amount of usage is what convinced me. Not worth saving eight bucks or so.
Alrighty thanks everyone, I have the answers I need and have marked this thread solved, so I am unsubscribing from this thread. Have a great day!
* This post was last edited 01/04/21 12:47pm by SlowBro *
In my case, that is almost never. I have remote electric start. So the generator only idles until my inverter charger "flips" to generator power.
SlowBro wrote:
those cheap and inefficient Chinese generators and my van uses less gas per hour idling, despite having a larger engine.
Oh then that's perfect. I have in mind intermittent use, otherwise I would be buying solar.
those cheap and inefficient Chinese generators and my van uses less gas per hour idling, despite having a larger engine.
Gdetrailer wrote:
Most car alternators are designed for INTERMITTENT heavy charging
Most car alternators are designed for INTERMITTENT heavy charging
Oh then that's perfect. I have in mind intermittent use, otherwise I would be buying solar.
By INTERMITTENT heavy charging, that means for a few minutes at a time. Basically when you start the motor, it's pulling hundreds of amps to turn the starter for a few seconds...so a few minutes charging at 80-100amps will replace the amp-hr that were pulled. After that it just puts out a few amps to run the lights, radio and other light loads. Nothing close to 150amps.
You can buy specialty after market alternators designed to put out high amperage for a longer period of time. Most are geared toward full size pickups with big V8 engines that won't notice the power needed to run them. They are also frequently optimized to put out significant amperage at lower engine RPM.
As you indicated it's the stock alternator, I would be very surprised if it can withstand anything close to 150amps output for more than a few minutes. If you are lucky, there will be a cut out that stops the output. Otherwise, very good chance of burning out the alternator. (This is made even worse by the idea of doing it with the vehicle parked and no airflow flushing the heat out of the engine bay)
From the battery to the inverter, you will need some pretty heavy cables as you are going to be pulling upwards of 80-100amps off the truck battery.
You will need to look at the continuous output of the inverter. Usually, they give a peak load rating as the main number. That peak load is usually only good for seconds or minutes. There is a continuous rating (often hard to find) that is much lower.
If you upgrade everything from the alternator thru the inverter to handle the loads, it's pretty straight forward and at 120v, the cabling to go back to the trailer converter (charger) doesn't have to be excessively large due to the higher voltage (typical extension cords is good for this size load) and as previously mentioned once you get 120v power of sufficient amperage back to the trailer, the converter won't know the difference between your system and shore power.
If you have the alternator that can provide the amps, it's actually a good solution to charging while towing (not so much while stationary). The problem with charging directly off the 12v system is the wires going to the hitch are tiny and often the connections are of poor quality with low voltage (12v) you get a lot of power lost. This results in only a few amps making it back to the trailer battery.
Probably not worth replacing the generator if it's in good running condition but watch and you can find a good quality inverter generator for $4-500 (helped a friend pick out a 3100w dual fuel Champion last summer for $500). And yes, they do save on fuel consumption compared to the old cheap fixed speed generators. Only under high loads will it be comparable fuel consumption. So an 800w load on a 3000w generator will be throttled way back with an inverter generator and do significantly better (and be much quieter).
SlowBro wrote:
Per this battery manufacturer, alternators direct connected (using battery cables or jumper cables) are not designed to charge batteries, only maintain them. Also, I recall an Interstate battery tech telling me the same.
But inverters are common, provided I get the sizing right, engine RPMs, all that
So let me see if I got this correct: You are concerned about using your charging system going straight from the source (alternator) to your depleted group 24 battery, but you're ok with going from the source, through an inefficient inverter, back through an inefficient converter to recreate the DC you just had? How could that possibly be better? 2112 wrote:
Can you get your vehicle close enough to the house battery to use jumper cables? That's how I do it.
Can you get your vehicle close enough to the house battery to use jumper cables? That's how I do it.
Per this battery manufacturer, alternators direct connected (using battery cables or jumper cables) are not designed to charge batteries, only maintain them. Also, I recall an Interstate battery tech telling me the same.
But inverters are common, provided I get the sizing right, engine RPMs, all that
I bulk my group 29 battery for about 20 minutes with jumper cables when needed. That gets me back to about 75%. You don't need to completely recharge your battery every time. It's inefficient doing so with a generator. Give it a good full charge when you get home.
SlowBro wrote:
No it uses far more, because it's not an inverter genny. It's a cheap inefficient Chinese genny. Uses at least 50% more gas per hour, maybe as much as 300% more.
However, the cost difference for such a small amount of usage is what convinced me. Not worth saving eight bucks or so.
Gdetrailer wrote:
At least you do now realize the gen you already have will use far less fuel..
At least you do now realize the gen you already have will use far less fuel..
No it uses far more, because it's not an inverter genny. It's a cheap inefficient Chinese genny. Uses at least 50% more gas per hour, maybe as much as 300% more.
However, the cost difference for such a small amount of usage is what convinced me. Not worth saving eight bucks or so.
Fuel usage on portable gens are typically are for HALF LOAD or FULL LOAD, need to read pretty closely. They don't typically give no load figures since for the most part you WILL be putting some sort of load on the gen..
Found some info on fuel typical useage at idle for vehicles..
HERE
2 liter engines .16 Gal per hr
4.6 liter engines .39 gal per hr
5-7 liter engines .84 gal per hr
Although, those numbers look suspiciously low, but I will humor these folks by using the the numbers above for comparison..
It takes a certain amount of fuel to air ratio to keep any ICE engine just running, period. Even with the use of fuel injection, idle cannot be sustained if you do not supply enough fuel for the air in each cylinder.
The more "displacement", the MORE fuel you will use just to keep the engine running at idle with no load.
A typical non inverter 4Kw portable gen uses a 6.5HP 212 CC engine like THIS one. While this gen doesn't "idle" and it runs at 3600RPM all the time it is better on fuel than you think.
The gen in the link is rated at 16hrs of run time at 50% load, the fuel tank is only 4 gallons which comes out to only .25 gal (ONE QUARTER OF A GALLON)of fuel per hr at half load!
a Lighter load on that gen than half will most likely result in even a slightly lower amount of fuel used per hr.
Another example is a smaller 2Kw gen I used to have yrs ago, a "Buffalo Tools" Gen154, 2.4 HP engine, had 1.32 gallon tank and was rated at 9hrs run time at half load..
That is only .15 Gallon per hr at half load..
You can find some info on that one HERE
So, for a car to use less fuel idling than what that a 4Kw gen uses you would HAVE to have a displacement much smaller than a 2.0 liter engine and to find a car that uses less fuel than the old school 2Kw gen you would have to have a car with nothing more than a 2.0 HP lawn mower engine!
ANYONE that says else wise is only kidding themselves and totally ignoring physics.
valhalla360 wrote:
By INTERMITTENT heavy charging, that means for a few minutes at a time. Basically when you start the motor, it's pulling hundreds of amps to turn the starter for a few seconds...so a few minutes charging at 80-100amps will replace the amp-hr that were pulled. After that it just puts out a few amps to run the lights, radio and other light loads. Nothing close to 150amps.
SlowBro wrote:
those cheap and inefficient Chinese generators and my van uses less gas per hour idling, despite having a larger engine.
Oh then that's perfect. I have in mind intermittent use, otherwise I would be buying solar.
those cheap and inefficient Chinese generators and my van uses less gas per hour idling, despite having a larger engine.
Gdetrailer wrote:
Most car alternators are designed for INTERMITTENT heavy charging
Most car alternators are designed for INTERMITTENT heavy charging
Oh then that's perfect. I have in mind intermittent use, otherwise I would be buying solar.
By INTERMITTENT heavy charging, that means for a few minutes at a time. Basically when you start the motor, it's pulling hundreds of amps to turn the starter for a few seconds...so a few minutes charging at 80-100amps will replace the amp-hr that were pulled. After that it just puts out a few amps to run the lights, radio and other light loads. Nothing close to 150amps.
Typically in the seconds to a minute time frame a alternator might putout more than HALF the rating after startup, batteries can be discharged heavily while starting an engine and the regulator will attempt to put that back into the battery as quick as possible but it may take 15 minutes to an hr to FULLY recharge the battery since the battery voltage goes up as it is charged and the alternator voltage will typically max out around 14.4V so the amperage going back into the battery will taper down very quickly often within a couple of seconds..
It wasn't until you got into the 1990s when autos started to get alternators larger than 35A-60A and the reason was because of additional high power accessories like power windows becoming standard on vehicles.. Most accessories are ALSO intermittent loads, used for SECONDS at a time..
I have repaired alternators, trust me, there is very little space in there to dissipate heat from the regulator, windings and the diode packs..
Excellent replies.
In that photo posted earlier I was actually trying for a faster recharge with more amps, by adding the amps from the charger on the inverter- truck combo with the other chargers' amps being run from the Honda 3000 in the bed of the truck at the same time.
That worked until the amps tapered to where the Honda would run the total amps being accepted, and the amps from the extra charger on the inverter were not needed anymore. ( I did not have solar then or it would have added even more amps)
The OP's plan is not stupid. He just needs to get his spec numbers correct to make it work.
In my test, I ran the truck in idle for an hour, no problem. (I did not set fire to the wet grass with the cat cov either!) Adding some gas to get more revs did nothing at all to help make it work better.
ISTR trying it with the lights on too, but that sure didn't help--I read that somewhere, but think it must have been an idea from the old days before the newer style alternators and their voltage regulation.
As for efficiency--that means nothing! You are off-grid and just want to get by ok. So what if it costs something to get gas the next time you do a "fill-up" earlier than it would have been time for a fill-up?
If you want to save money, don't buy an RV.
Quote:
Oh then that's perfect. I have in mind intermittent use, otherwise I would be buying solar.
Oh then that's perfect. I have in mind intermittent use, otherwise I would be buying solar.
You our idea of intermittent is not the same as the auto MFG
Their idea is closer to a few hard minutes right after startup on a hot day with the dash A/C turned on, so that is dump some quick amps into battery while holding in the a/C compressor clutch and running the blower full blast inside for cool down, and the condenser fan, and the electric radiator fans
When the alternator starts getting warm and or the battery voltage starts rising output is reduced
Your idea is run long enough to charge house battery, then do it again next day or day after
Theirs hard high charge rate,for Minutes every time started,
Yours hard high charge rate, for hours every now and then,
I think.. You have already been suggested better ways, DC to dc voltage converter or jumper cables
Converters are more in the low 70s in percent of efficiency from my observations, converted at or near full output are about 73% efficient, converter or charger will use 1000watts to charge at 730watts into battery, now the inverter is also a loss, even at 80% efficiency the inverter will need 1250w input for the battery to be charged at 730w
At 12.5v that's 100amps from the alternator and that will mean your TOW vehicle chassis battery is being drawn down and not being charged, to keep the vehicle battery charged you need 13.8v
13.8v 90.6 amps 1250watts to inverter,
Plus what ever the vehicle engine system needs are possibly another 30amps or more,that's 120amps total for how ever long it takes for the house battery charge rate to start decreasing,
How well is the alternator going to stand up to that kind of treatment, the 800w inverter is not going to carry 1000watts for more than a few seconds trying to power the converter at full 45 amp charge
I suggest doing this before the battery gets any lower than 75%, try to keep the charge rate closer to 30 amps, so as to not damage the alternator
The heavy load amps is going to be from alternator to inverter, that stock alternator it's the item to worry about, ambulances, POlice cars, fire trucks,
All use heavy full duty rated alternators, this is Optional equipment on vehicles sold for consumer use
I can explain it to you.
But I Can Not understand it for you !
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BFL13 wrote:
...The OP's plan is not stupid. He just needs to get his spec numbers correct to make it work....
....If you want to save money, don't buy an RV.
...The OP's plan is not stupid. He just needs to get his spec numbers correct to make it work....
....If you want to save money, don't buy an RV.
No one said the "plan" was stupid.
However, unwise, wasteful, not the best use of a huge displacement engine, hard on the engine and drive train, hard on the alternator, yes..
No matter HOW you fudge "the numbers" you WILL be at an economic disadvantage using an automobile engine to fully recharge your "camping experience" battery(ies).
Efficiency is governed by the "Laws of Physics", those laws are unchangeable by you, me or anyone else in this world, they are set in stone. Sure you might have a 300HP capable engine idling for hrs on end and you are only making it work for a measly 1 HP worth of work.. But that engine is using much more than 1 HP worth of fuel per hr and that is reflected in a lot of wasted energy in the form of heat.
Some folks just are not able to visually see and analyze that in their head and MUST "demonstrate" and see it for themselves.. Myself I don't "need" "demonstrations" or "experiments" to realize that while it can be done, it is is very inefficient mechanically, physically and chemically to do so.
Engines REQUIRE very specific min fuel to air ratio just to keep it running, that minimum is a "constant" for ALL gas engines. A smaller engine working at half load will consequently use less fuel than a large displacement engine idling.
Granted with the advent of fuel injection, manufacturers can control the min fuel usage closer, but if you lean the mixture too much, you now run into the possibility of burning valves, damaging pistons and overheating the engine.. There is a fine line between destruction and fuel efficiency when it comes to leaning out an engine.
To the second point I quoted.. YES!Buying a RV is not "cheap living", pretty much the same as buying a boat.. Insert money and flush..