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Charge time using truck alternator


Iflyfish

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I am wondering how long it takes you to recharge your battery using your truck generator? I'm trying to sort this out as I use a CPAP that will draw down my 12 volt battery overnight. 

Thanks

Iflyfishwithmycpap

Edited by Iflyfish
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Are you talking about the truck engine alternator or an RV generator??

Your Toyota has a 60 amp alternator and it needs around 25 amps to run. So you will have some 35 amps (475 watts) to charge with. All kinds of magic math means that you will need 1-3 hr, depends on your definition of "draw down".

A 100 solar panel would allow for almost perpetual motion for your CPAP. My wife uses a CPAP and I have 2 house batteries and 200w of solar. I dont even worry about power conservation for anything

 

 

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40 minutes ago, WME said:

Are you talking about the truck engine alternator or an RV generator??

Your Toyota has a 60 amp alternator and it needs around 25 amps to run. So you will have some 35 amps (475 watts) to charge with. All kinds of magic math means that you will need 1-3 hr, depends on your definition of "draw down".

A 100 solar panel would allow for almost perpetual motion for your CPAP. My wife uses a CPAP and I have 2 house batteries and 200w of solar. I dont even worry about power conservation for anything

 

 

l am talking about the alternator. Excellent information. Very helpful! 

I am indeed considering solar. Where do you store your 2 house batteries? I assume you are using 2 deep cycle golf cart batteries in parallel. Did you do the install yourself? Aprox cost?

Thanks a lot.

Iflyfishconmiaigos

 

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I am planning on installing a 2nd 100AH deep cycle battery and have trouble finding suitable location for it. I thinking of building in enclosed box with ventilation leading to outside as hydrogen is being released while charging and it could set the coach on fire. The other option is to install in the outside storage box but it's too far from the 1st battery and I still plan on carrying the generator on the outside box. Any idea?

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I can tell you from experience, that the engine alternator will take a long time to charge the house battery.  I will suggest a small generator. Then you can recharge the coach battery every morning.  If you want to run AC etc, you will need a bigger genset.

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Problem with space for 2 batteries, how about 1 bigger one?

Here is a list of battery dimensions,   https://www.batterystuff.com/kb/tools/bci-battery-group-sizes.html

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I cannot recall starting out with a low battery and charging it with the truck alternator but would guess it would take a long time.  I have to agree with Dan on this and would go with a small generator if doing it for myself.  The generator could be used for other things also.

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Frankly if you have the original charger the truck will do a better job this of course depends on you drive time. The original charger is at best 10 amps charge more often a good bit less. A modern charger will be better they are in the 35 amp plus range. Another effort would be to run another # 8 wire connected to the same spots as the first one lot cheaper than removing the original and replacing it with a bigger wire. 

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My previous RV had an old style 50 amp converter. The battery charger section was rated at 3amps. Running a generator would take a day to recharge a house battery.

Changing the converter to a modern 45 amp unit, the generator could charge a battery is 1-2 hr.

 

 

 

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Yep the old converter/chargers were weighted to lighting 25 amps of old bulbs that were better heaters than lights. Their charge circuits were not much more than poorly regulated trickle chargers.

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I appreciate all the good thinking here. Thank you for your time and consideration.

I have purchased replacement LED bulbs for all lights, save for the florescent bulbs, not sure what to do with those. I did that in my previous motor home and could not believe how much it effected battery power usage! 

I have also purchased a Yamaha EF1000iS, 900 Running Watts/1000 Starting Watts, Gas Powered Portable Inverter, CARB Compliant. It fits perfectly in my factory carrying box on the back. Simply padded the front and back for security. The Yamaha starts on the first pull and is much quieter than I had anticipated. 

Iflyelectrified!

Edited by Iflyfish
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A small generator like that is all you need unless you have to have AC. It's output is plenty for any charging system.

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So now you have a house battery and a small generator, should be good to go for some time to come.   Someone on here mentioned running the genset on what ever gas is available and then when putting it into storage running it dry on ethanol free gas, on the surface seems like a good idea. Now that I am doing short trips and use the genset only a little I buy the no ethanol gas and run it on that all the time and then run it dry when done with it and drain the carb.   I am only buying a couple gallons and the ethanol free is widely available.  

 

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Sta-bil fuel storage is the simple answer. Put it in the gas can you use. Keep the generator tank full. No need to drain and refill.

Or for the that's to complicated crowd   http://trufuel50.com/product-info/4-cycle/

 

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I don't use enough 4 cycle gas to be bothered mixing oil and stabil and gas together so now use Tru fuel in my weed wacker. Weed whackers used to last about 2 years, now using Tru fuel I am on my 4th year with this weed wacker.  I use about 2 cans of it a year, so no big deal.

Same thing with the genset, I will not use enough gas to be bothered mixing the stuff up. So easier and likely cheaper in the long run to buy the non ethanol.

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On 7/8/2017 at 4:42 PM, WME said:

Problem with space for 2 batteries, how about 1 bigger one?

Here is a list of battery dimensions,   https://www.batterystuff.com/kb/tools/bci-battery-group-sizes.html

This is very helpful. Look like the biggest one that fits on the compartment is 125AH. I am building an vented box soon If I decide that I need a 2nd battery. Let's see how fast the 170A alternator can charge the battery with the engine running. It should pump out about 140A at 1000rpm so it takes about 1 hr. To top off the battery when not driving. I can still carry the Honda EU2000I if needed. Adding a 2nd battery will add weight to the overloaded MH. I can run the truck engine at anytime even mid night where I can't run the generator during quiet hrs.

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I finally bought a new and bigger deep cycle battery for $109 from the Homedepot as I found the Excite battery is about twice heavy compared to the regular truck battery I had in the coach. This one has 115AH reserve capacity and 13" long which is the longest one that fits on my Itasca battery compartment. I also moved the inverter back to right above the battery, re-ran #2/0 cable (good for 200A) thru 150A DC breaker and a current shunt to measure current flow. That was I could have time fore before our Monterey camping trip. I also received the 170A alternator...will do some more work in the upcoming weeks. I don't think a 2nd battery is necessary and not planning on it.

20170715_124542.jpg

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I hope everybody remembers the SAFE charging rules for batteries.

MAXIMUM safe charging rate for lead batteries, 10-85% charged, is 20% of capacity. Above 85% charged its 10%.

Overcharging will overheat the battery and thats not good.

 

Edited by WME
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On 7/11/2017 at 9:53 AM, Nam said:

This is very helpful. Look like the biggest one that fits on the compartment is 125AH. I am building an vented box soon If I decide that I need a 2nd battery. Let's see how fast the 170A alternator can charge the battery with the engine running. It should pump out about 140A at 1000rpm so it takes about 1 hr. To top off the battery when not driving. I can still carry the Honda EU2000I if needed. Adding a 2nd battery will add weight to the overloaded MH. I can run the truck engine at anytime even mid night where I can't run the generator during quiet hrs.

The alternator relies on the battery it is connected to for regulation so unless the coach battery draws down the truck battery too you will not see that kind of current, the regulation is voltage dependent not current. Unless you feed the coach battery with a VERY heavy cable it will never see that kind of current no matter how big your alternator is. It is also doubtful you will see anything close to 140 amps at a high idle. You do also realize that in order achieve that kind of output the alternator would have to be driven with dual belts a single 1/2 “ belt won’t cut it. Yes modern alternators have that kind of output but they are also driven by a very wide serpentine belt.

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Thanks for great info. While the truck is running, the two batteries are connected in parallel so I am counting on internal regulator to not over charging the batteries. #2/0 is over killed a bit but I already had cables and connectors it also helps minimizing voltage drop. Let see how much current can the new alternator can generate. I can measure up to 200A thru the shunt

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20 hours ago, Nam said:

Thanks for great info. While the truck is running, the two batteries are connected in parallel so I am counting on internal regulator to not over charging the batteries. #2/0 is over killed a bit but I already had cables and connectors it also helps minimizing voltage drop. Let see how much current can the new alternator can generate. I can measure up to 200A thru the shunt

In order to deliver that much the batteries have to need it. Yes the batteries are connected but again the alt. sees only voltage so if the two match that is what they will do in short order as soon as they are connected it will charge accordingly. An other factor you need to understand is the alt output cable to battery is only a #8 wire so at full smoke it's going to suffer. I don't know what year your MH is but just about all were run through a 60 amp body fuse or a fuse link.  An alternator's output is controlled by field voltage the total output is by design full field voltage = full output anything less the current drops so the draw needs to be there, the internal regulator is what alone controls field voltage and it looks at incoming voltage from the battery/batteries. Many years ago I tested a huge Delco alternator from a piece of construction equip I supplied full field voltage to the field during the test the vents in the twin 6 volt 200 amp batteries blew water out the top like a fountain. Again if you are still using the single 1/2" belt it does not have enough grip to make even a hundred amps. In order to check that you will need a resistive load not just a battery because they are also capacitive.

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I don't have resistive load except I can connect the heat gun thru the inverter. I also setup two 200A meters  (one before the coach battery and one after) I just want to know if the alternator can supply enough power for the AC (inverter's load) otherwise I may get to the destination with a dead coach battery. Mine is 1990 and the Alternator's fuse is 80A. I am replacing the main cable connecting to the new alternator and batteries with #2/0 (good for 195A) please take a look at the attached diagram and kindly let me know if I am on the right track

Toyota RV_0.jpg

Edited by Nam
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Yes that would work. Let me get this straight you are trying to run the AC while moving with the Alt.? If that is the case fat chance. You would be better off with a 120V AC alternator generally called a auxiliary generator. The stock alternator is over driven meaning it turns faster than the engine the reason being it will charge at lower engine RPM so it requires more engine power and a better belt drive, Again you are back to the fact a single belt will not make the power you seem to think it will I don't care how big the cables are the belt will slip. If you really want to see what would happen you will need some thing like a resistive battery load tester, (kind of like a toaster) adjust to full smoke and see where the belt starts to slip. The stock alternator belt will slip (squeal) at highway speeds unless it is super tight.  So with a large crowbar against the alternator till the belt sings may gain a few amps at the cost of the water pump bearings.

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Some limits. Basic math 750 watts = 1hp. Also 750 w = 55 amps. For all you Math PHD types these are approximate, easy to use numbers.

A 1/2" wide v-belt can transmit 3 hp around a 3" pulley, 1 hp around a 2" pulley, BUT only 1/3 hp around a 1.5" pulley

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Thanks. That makes sense. I will run thru the test and see how much this new alternator can handle

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  • 1 month later...

I finally completed the new 170A alternator installation and put the system to test. It turns out that the alternator can pump out 160A (measured with my DC AMP meter) at 2000 RPMS which is more than what I needed (125A, 25A for the truck and 100A for the AC thru the inverter). No sign of belt slippage. I tried to use a high quality belt and not tight in it excessively. At full load the AC draws almost 100A DC or about 800W on the AC (after inverter's loss). I did run into another issue which the Sunforce 2000A pure sine wave inverter cannot handle the AC and refrigerator at the same time. It barely handles the AC alone. I ended getting a new huge 2000W low frequency inverter. I learned a great deal thru this experiment. So far so good as I've taken the motor home on short trips and the system seems to handle just fine...will try to a detailed write up later.

20170904_084824.jpg

20170904_084907.jpg

20170904_084848.jpg

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How are you measuring the current? No I understand the clamp meter what are you using to draw than much current? Next question what is suffering the alt or the battery?

 

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The loads are 8000BTU AC unit and a small refrigerator thru a 2000W inverter which I have a shunt to measure current flow to the inverter as well. I think the inverter is the one which suffers the most right now. I am planning to get a 3000W unit so it doesn't heat up as much. Pic below shows just refrigerator's load.

20170904_084715.jpg

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