Alternator Power

[JCTex]

Assume a truck camper w (1) a non-AGM starting battery and an 160A OE alternator; (2) a house bank w 2 Lifeline 6CT's rated at 12VDC 300Ah (150Ah @ 50% SOC); (3) an 80W charger powered by 15A 120VAC shore power, when available and used; and (4) 400W of solar providing ~25 Amps/hr x 5 hrs.

 

The 2-6V's are in series, the cables coming out go through a cat fuse and HD cut off switch on pos side and a shunt on neg, then to a buss bar. There all the power sources, an 1000W inverter only, and distribution to the DC panel are attached. There are switches and breakers everywhere, too; but their discussion is not important here.

 

My question is how best to get power from the alternator? The pos and neg cables coming from the front through the firewall will be connected to the above-mentioned bus bar.

 

If I install a smart soloniod to the alternator, the regulator will (after charging the starting battery) send a steady voltage back of 13.2, 14.2, or whatever it's set to do, emphasis on the word "steady". This current will never be subjected to 3-stage bulk/absorption/float charging. Additionally, if the charge controller is putting in power while the alternator is running, the regulator will see that and close the circuit, thinking the solar voltage is coming from the battery.

 

So, how do you properly use a vehicle's alternator to charge a deep cycle, AGM bank?

 

Jerry

[Darryl&Rita]

Properly? One doesn't, with an alternator paralleled to a wet battery. The typical voltages on a vehicle are to low to do much for your AGM bank. Lifeline calls for between 7.1 and 7.3 v bulk charging voltage.

[skp51443]

Head for the boating websites and look for their alternator control systems, expensive from what I recall.

 

Are you going to be driving enough with your batteries low enough to make the investment worth it?

 

Maybe side-step the issue and run an inverter to power your charger? Is the charger really 80W ( 6 Amps ) or 80A?

[Jack Mayer]

Once you put on a smart charging regulator (charger) into the alternator circuit it "should" continue to supply full charge during bulk charge. Assuming the battery is depleted significantly and will stay in bulk. Just make sure that you set your charge points on all charging sources to be the same. Once you leave bulk then you will get some interaction between the charging sources since the battery is not taking on as much charge.

[JCTex]

I'm not sure how an inverter can charge anything. The only way it can get power is from the bank. Sorry on the charger; it' 80 Amps. It's not combined with the inverter and requires manual plugging. I'm only bringing it for when I'm parked next to the MH on shore power.

 

I found a great marine 3-stage regulator by BalMar. Yip, it costs a lot; but less than a 2d, stand-alone alternator. However, they are the ones who suggested I use it only with a selector switch. They said its too dumb to tell the difference between bank voltage and solar panel input. That will be okay because the times when I'll be driving using the alternator and have my 4-100W flexible panels still on top will be very few. 'Course, if the panels are arrayed, the alternator should be off. Unfortunately, that won't always be true. This vehicle has a winch. It's probable the winch and engine may be used with the panels still on the rack and, therefore, plugged in. Thus, a selector switch is a good thing if I don't want to confuse the marine regulator.

 

You're right about first analyzing the need. Say, I left a camp in the morning at 50% SOC, or 150 Ah; that's 147 Ah below 99%. I don't know the maximum rate of recharge for the Lifeline 6CT; but I suspect it's lower than what the alternator can produce. Whatever the number of amps is feeding the bank divided into the number of amps needed should be the number of hours I have to drive at highway rpms to get the bank full. This is assuming the solar panels have been stowed and are not helping. Does anyone have a guess how long that would be given this hypo?

[wa_desert_rat]

Why wouldn't the solar system charge the house batteries on the RV while you're driving? Am I missing something here? Or, as Stanley suggested, you could install an inverter in the engine compartment and then run AC back to a charger near the battery bank, and then appropriate cables to the batteries. This would eliminate needing to do that charging directly from the alternator. The advantage to this method is that you could use a good "smart charger" (which an alternator chearly is not!).

 

WDR

[JCTex]

I'm having trouble communicating my equipment. Sorry.

 

I asked you to assume a truck camper because that's the normal place for this multi-source power problem. In fact, I have a 4-dr Jeep Rubicon that's being re-built for semi-extreme crawling but also converted inside for 7-10 day overlanding. It will be towed behind my MH. So, one question I haven't posed is how can I get power from my coach to my Jeep's battery bank.

 

But back on what I asked earlier: my 4-100W solar panels are really good; but they are the flex type. This is to,allow for the Jeep's twisting and bouncing on rugged trails. I just didn't figure glass panels could stand that. Also, I'm rigging them to slide into slots on my overhead rack. I want to get them off and store inside to lower the theft probability. So, contrary to our MH/trailer setup, these solar panels will not always be up there.

 

And I'm still not getting the inverter suggestion. If I put an inverter under the hood, I presume it will get its power from the alternator? Then, I take that a/C power back to my stand-alone charger and run it to my bus bar. I don't understand why that's better?

[oldjohnt]

Absent spending some bigger bucks, while driving with the AGM bank connected essentially in parallel with a conventional lead acid truck battery, I don't see the AGM's ever getting a proper (certainly NOT smart) charge, although sure some electrons will get pumped into them. It's my understanding AGM's are more particular as to their charging voltage versus the lead acid, which is why my smart charger as well as my smart solar charge controller both have individual settings (AGM or Lead Acid) depending on the type of batteries. Here's another issue, when you place the AGM's in parallel with your engine battery (you now have a current divider network mind you), its hard to accurately predict setting here how much current flows one way (engine) and how much the other (AGM) as it depends on resistance of the batteries as well as all the cables and connections plus your mixing apples and oranges since the AGM's prefer different charging then the lead acid. I JUST DONT SEE IT WORKING ALL THAT WELL unless you do some conversions and some type of smart regulation, BUT STILL THERES A CURRENT DIVIDER AND THE AGM DOESNT REACT THE SAME AS THE LEAD ACID BATTERY and I imagine resistance differences in the AGM's versus the lead battery, you're still mixin apples n oranges.

 

If you have 400 watts of solar and if your solar charge controller is "smart" plus has a setting for AGM, I think I'd be tempted to just use solar to charge the AGM's and let the alternator charge the truck PERIOD. However, If its necessary to supply more charge to the AGM's then the solar can supply, you could hook up an Inverter (12 VDC to 120 VAC) fed off the truck battery when driving which powers a 120 VAC powered Smart Charger suitable for AGM charging as that will do a better and more precise job of charging the AGM's then connecting them up in parallel with your trucks lead acid battery. Can you tell I don't think AGM's in parallel with a lead acid will do a great job of providing any quality charge to the AGM's?????????????

 

 

That being said, I have my four six volt golf cart batteries (460 Amp hrs, series parallel for 12 volts, of course) essentially in parallel with my motorhome battery while Im driving, BUT they are all lead acid no mixing AGM's into the equation. I cant say its perfect and NO my batteries aren't being "smart" charged but while driving their voltage pretty well sets around 13.9 to 14.2, they're still getting somewhat replenished but not SMARTLY like my smart charger or smart solar controller would do. However, if I'm going to be driving 6 or 8 hours I don't care that much, they still get "some" charge even if not at 14.4 + bulk then 13.6 absorption etc.

 

I don't see it hurting anything if you hook the AGM's up to your buss so the alternator does "something" (I say its hard to predict just what due to different resistances and a current divider plus different battery technology) to them while driving, but then depend on either some smart solar controller charging or a smart charger once plugged in. Either that or run an Inverter off your truck battery while driving and let it power a smart AGM compatible charger............

 

Best I have to offer, I was more into AC Power Distribution most of my professional life then DC and electronics, so don't bet the farm on anything I said lol The other fine gents here are more savvy on this then yours truly.

 

PS you ask why an Inverter is better??????? Its because I'm assuming its used (while driving so alternator feeds truck battery) to power a 3/4 stage SMART CHARGER with AGM feature/settings which has to do a better job of precisely charging the AGM's then if they're setting there in a parallel current divider circuit coupled up to a different type (lead acid) battery!!!!!!!!!!!!!!!!

 

 

John T

[wa_desert_rat]

I'm having trouble communicating my equipment. Sorry.

 

I asked you to assume a truck camper because that's the normal place for this multi-source power problem. In fact, I have a 4-dr Jeep Rubicon that's being re-built for semi-extreme crawling but also converted inside for 7-10 day overlanding. It will be towed behind my MH. So, one question I haven't posed is how can I get power from my coach to my Jeep's battery bank.

 

But back on what I asked earlier: my 4-100W solar panels are really good; but they are the flex type. This is to,allow for the Jeep's twisting and bouncing on rugged trails. I just didn't figure glass panels could stand that. Also, I'm rigging them to slide into slots on my overhead rack. I want to get them off and store inside to lower the theft probability. So, contrary to our MH/trailer setup, these solar panels will not always be up there.

 

And I'm still not getting the inverter suggestion. If I put an inverter under the hood, I presume it will get its power from the alternator? Then, I take that a/C power back to my stand-alone charger and run it to my bus bar. I don't understand why that's better?

Knowiing what it is we're supposed to be answering is always a plus.

 

If you were in a pickup truck towing a 5th wheel or a travel trailer, an inverter in the pickup would let you use MUCH SMALLER CABLES back to the 5er or TT. This is because it would be 120vac in those cables and the current (amps) lower for the same power (volts higher, current lower) and lower current means smaller wire.

 

Then that 120vac would power the smart charger. Since the engine on the pickup would be running any losses would not be an issue (e.g.: inverter inefficiencies and cable lengths). But your Rubicon's battery doesn't need much charging. Just one of those 100-watt panels (secured to the top of the Jeep) would be more than sufficient to keep its battery charged while you're towing it; even with the ignition key engaged.

 

Trying to keep a big battery bank charged using a tow vehicles alternator would mean that you'd have to run a very large cable for that 13 or 14vdc (alternator output) to get enough current to the batteries. So the inverter suggestion is actually more effective. You just have to run an extension cord not #6 cables.

 

WDR

[Jaydrvr]

So, let me be the contrary voice. I understand all the different facets of doing this - I've been experimenting with this setup for twenty plus years. I've settled on two 8d Lifelines charged almost exclusively from the 130 amp truck alternator via a BlueSea automatic charge relay with the alternator output set at 14.2 volts, through, if I remember, an 8 gauge cable which limits charging current to 80 amps. I use this system about three hundred days a year, and the Lifelines are almost six years old. I rarely pull them below 80% soc. My starter batteries are flooded, and I get reasonable life from them. Not sure how many years - I didn't look it up. So, it may not be optimal, but at least in my installation,I would call their performance flawless..ymmv.

 

Jay

[JCTex]

Like everyone who spends the money on solar, I hope it will do all the charging my bank needs. I do believe that's realistic but I have more than the usual if's. First, I may have rolled into camp too late and too tired to pull out the panels and set them ready for morning sun. A similar thing is if we're planning on doing another trail run the next morning before I can get the panels on. I can go on and on about why my solar set up,great but not the total answer.

 

Fortunately, I DO have some help if my house bank gets drawn down to 50% SOC (150Ah). The Rubicon comes equipped,with 2-12VDC receptacles powered by the starting battery. I couldrobably get through a night with that. Also, my refer which draws 7/24 to a low-demand Danfoss compressor could, if necessary, be unplugged from my house bank DC and into the Jeep's DC. This is particularly helpful if I do this while driving. It would allow whatever system I have to charge the bank from the alternator not to have to compete with amps going out the other side to power the refer.

 

I kinda get the inverter idea better. Let's say I bring proper-size cables from the starting battery posts (thru some fuses and switches, of course) thru the firewall back to the elec center behind my front seats. There, I connect the leads to my 1000W PSW inverter. I plug the 120VAC plug on the charger to the 120 receptacle on the inverter. Last, I run cables from the charger to the buss bars for the house battery bank.

 

I start the engine and turn a switch that manually connects the starting battery to,the inverter. My charger is 3-staged but only shows status with idiot lights; however, I can wire in a battery monitor like RV'S use. By watching the % of State Of Charge as I drive, I should know when to disconnect the inverter, if ever, before arriving at my destination.

 

So, to,all you inverter-idea folks, is this what you had in mind?

 

Thanks to all who've tried to help. Most of you have forgotten more about DC power than I know.

[JCTex]

I read a couple of your helps after my previous post; so, the startling appearance of my ignorance is a shadow of its former self. That being said . . .

 

Is my 1000A inverter big enough to produce enough A/C for the charger to fill the bank? Im guessing the answer is 1000W, less 10% inefficiency, divided by 120 is 7.5 Amps. That's all the charger will get. So, what does the "80A" rating mean?

[wa_desert_rat]

I read a couple of your helps after my previous post; so, the startling appearance of my ignorance is a shadow of its former self. That being said . . .

 

Is my 1000A inverter big enough to produce enough A/C for the charger to fill the bank? Im guessing the answer is 1000W, less 10% inefficiency, divided by 120 is 7.5 Amps. That's all the charger will get. So, what does the "80A" rating mean?

Well, since the output of a charger is about 14vdc... do the math.

 

On edit: Let me give you a hint here... the power doesn't change. But if the voltage goes down, the current goes up and vice-versa. So 7.5amps at 120vac is something your 1,000 watt inverter could handle pretty easily. 1,000 watts at 14vdc (which is what you'd need to actually charge your battery) would be a LOT more than 7.5 amps and require a LOT bigger cable.

 

And the smart charger running off an inverter would probably be more gentle on your battery bank. But, having said that, as Jaydrvr said, above, he does it the old fashioned way and it seems to work for him. But he is running a pretty big wire back to his 5er.

 

There are lots of ways to do this... and if it were me with a flexible 100-watt solar panel I think I'd try real hard to figure out a way to put it on my Jeep in such a way that it would be secure.

 

WDR

[Kirk W]

Is my 1000A inverter big enough to produce enough A/C for the charger to fill the bank?

I believe that you mean to say, 1000 watt inverter? watts = amps X volts

[oldjohnt]

Pebble man, wow this is getting good, here are my thought to you most recent questions:

 

"I kinda get the inverter idea better. Let's say I bring proper-size cables from the starting battery posts (thru some fuses and switches, of course) thru the firewall back to the elec center behind my front seats. There, I connect the leads to my 1000W PSW inverter. I plug the 120VAC plug on the charger to the 120 receptacle on the inverter. Last, I run cables from the charger to the buss bars for the house battery bank.

Lets run the math first. Looks like I'm in the camp wit the good wa desert rat man on this one!!!!!!!!!!!

 

1) At 120 VAC output, your 1000 W Inverter can supply around 8 Amps into a 120 VAC input charger. "Is that enough to power your 80 Amp DC charger????????

 

80 Amps at lets use 14 charging volts, would be 1120 watts which is a MORE THEN 1000 watts, although I doubt it actually pumps out 80 amps continuous very

long. Regardless, a 1000 watt inverter isn't quite big enough (it can still "work" to some extent, although marginal) but Id be more comfy with say a 1500 watt

Inverter. NOTE I dint take inefficiency into account which makes things even a bit worse, more reason why Id use a 1500 watt inverter.

 

2) Supplying current from truck battery back to Inverter:

 

If you used a 1000 watt (not quite enough perhaps) inverter at its max , that would require around 1000/14 = 71 amps DC to power it. Allowing for voltage drop

that could require something like 6 to 4 (depends on enclosures and jacketing and length and temp) Gauge conductors from truck battery back to Inverter. I

DONT LIKE THAT PLAN its expensive, and a bit impractical

 

IN THE ALTERNATIVE I AGREE WITH WHAT WAS POSTED ABOVE,,,,,,,,,,,I would place the 1000/1500 Watt Inverter right at the truck battery and then you run

120 VAC back to your battery chargers input WHICH WOULD ONLY BE A MORE MANAGEABLE MORE PRACTICAL AROUND 10 OR SO AMPS and for that

you could use 12/2 w/ ground cord which is MUCH cheaper and more practical and standard.

 

 

"So, to,all you inverter-idea folks, is this what you had in mind?"

 

See the above, in my mind I still prefer:

 

1) A smart 3/4 stage AGM compatible 120 VAC powered charger for the Lifelines INSTEAD OF TRYING TO CHARGE BOTH THEM AND THE LEAD

ACID TRUCK BATTERY USING THE TRUCKS DUMB ALTERNATOR (see my post above for reasons why)

 

2) I would place a 1500 watt PSW Inverter right near the truck battery so you only have to run 12/3 Gauge cable back versus 4 Gauge conductors!!!!

 

 

That's my story n Ima stickin to it lol, but its your money and your RV and YOUR choice.

 

Best wishes, if I invested in expensive AGM's Id want them to last which I believe can best be accomplished by the use of a smart charger.........

 

John T

[JCTex]

I keep remembering stuff that I take for granted but forget to tell you. With all the after market adds, I don't have room under the hood for my inverter. Even if I did, I wouldn't subject it to the amount of water it could experience. While I've said this rig is an overland Jeep, it will also do some trail work. Some water crossings can get pretty deep. That's why it has a snorkle for the air intake. So, the inverter has to go inside.

 

I think that's doable. I could runaway rope from the starting battery through the firewall, along under the center console, and behind the front seats to my elec center. Multiplying that x 2 gives my home run distance. A wire sizing chart will tell me the AWG needed IF I knew the amperage.

 

Using a wind/solar site I have that is set up for DC loads, I entered 1000 watts for the inverter, 8' one way, a 1% voltage loss, and a 12V system. The calculator says I need 2/0 AWG. I think that means 00, not #2 AWG. Two welding cables makes this a daunting project. I'm not sure my Xantrex 1000W PSW will accept 00 in its screw-tight connectors. Some of you need to run wire size and see if I did this right.

 

You are right about my inverter's being too small. It's one I bought for another project 4 years ago; and I thoght if try to make it work. I also don't li,e that it doesn't have a combined charger and built-in switchover. I'll look on the web and see what I can get a larger wattage, combined one for.

[JCTex]

DonRowe.com sells a KISAE 2000W, 55A charger PSW, transfer, and several whistles and bells for $619. It's not a Magnum; but I might be willing to take a chance. Assuming an 85% efficiency, would someone please help me with the math.

 

First, what amperage should I use for my wire size chart (160A less 10% = 144A probable output / 14?4V probable maximum voltage = 10 Amps)?

 

Second, if I used this KISAE and was running highway rpms to feed the inverter, how much of the charger's 55 Amps would you expect I could realize? Or, asked a more practical way, if my bank needed 150 Amp Hours to restore to 99% SOC, could this setup do that in ~3 hours?

[Darryl&Rita]

Put The inverter under the hood of the tow vehicle,run AC back to the Jeep, then use the smart charger on the Jeep.

[oldjohnt]

QUESTIONS

 

"First, what amperage should I use for my wire size chart (160A less 10% = 144A probable output / 14?4V probable maximum voltage = 10 Amps)?"

 

To fully power a 2000 watt "input" rated Inverter using lets say around 14 volts, would require 2000/14 or 142 amps INPUT. 14 volts x 142 amps in = 2000 watts

input.

Its output would NOT be a full 2000 watts as some of the 2000 watts in gets converted to heat. If you got lets say 90% or 1800 watts out at 120 volts, that's 15

amps available output.

 

DISCLAIMER I don't know if the 2000 watts you mention is units the rated output or input, if its output, due to heat losses the input would have to be higher, say

2200 watts or 157 amps at 14 volts !!!!!!!!!!!!!!!!!!!!!!!!!!

 

A 55 amp charger operating at say 14 volts = 770 watts, but I'm not counting for heat loss, these are only approximations mind you so don't anyone have a calf

 

BASED ON THE ABOVE IT APPEARS A 55 AMP CHARGER CAN DELIVER THAT CONSTANTLY FROM A 2000 WATT INVERTER NO PROBLEM. Above we were talking about an 80 amp charger which, of course, required more inverter power.

 

 

NOTICE this assumes your alternator can deliver sufficient amps full time to power the inverter plus charge the truck battery, looks like it can but be aware!!!!!!

 

 

QUESTION

 

"Second, if I used this KISAE and was running highway rpms to feed the inverter, how much of the charger's 55 Amps would you expect I could realize? Or, asked a more practical way, if my bank needed 150 Amp Hours to restore to 99% SOC, could this setup do that in ~3 hours?"

 

YES it looks like a 2000 watt inverter has plenty of power to feed a 55 amp battery charger, and yes in theory if it pumped 55 amps into your batteries for 3 hours, that would amount to 165 amp hours of energy replacement. To do so requires a smart charger that will remain in the high Bulk state for 3 hours all of which time the batteries are being fed a full 55 amps BUT DONT BET THE FARM ON THAT but Id guess (no specs on charger or battery state so cant say for sure) it could do it in 4 or 5 hours max.

 

Wire size. For the 120 VAC it looks like 12 gauge will do as you can pass 16 amps continuous through it if its romex, but if the run is long you might bump it up to 10 gauge just to reduce voltage drop. On the DC Id look at tables because it makes a HUGE difference if the conductors are in open air or jacketed or in raceway and if so how may conductors and temperature also comes into play.

 

Are we there yet lol

 

John T Again, there are several rough approximations above and a few guesses and heat losses and inefficiencies may not be all accounted for, but I think I'm still in the ballpark.

[JCTex]

Darryl&Rita-the tow vehicle is a diesel pusher 38' motorhome. So, your suggestion needs to be applied differently. My MH's 3000W Magnum inverter runs 7/24 when not hooked to SP because of the Samsung. If I'm tooling down the highway pulling the Jeep, and if I started the journey with the Jeep's on board house bank needed charging, I wonder if I could add a 120VAC breaker to my MH inverter sub-panel and run a 12AWG wire at 120VAC to the Jeep's inverter charger (via an inter-vehicle plug). The Jeep's inverter would think it's receiving shore power and switch off, transferring the 120VAC current to its charger part which, in turn, would multi-stage charge the Jeep's bank. The MH would just see the Jeep as another 120VAC appliance running off the inverter. Sounds good if I'm right,

 

NOW, BACK TO THE JEEP'S INDEPENDENT HOUSE POWER SYSTEM:

 

John-I donno if this inverter/charger measures input or out. I've always been taught to consider the rating to be outflow. For a 2000W unit, the Amps could be 16.67 @120; but allowing for loss, only count on 15 Amps available.

 

I also have a concern whether the OE alternator can power the load of the on-board inverter and run the Jeep, too. I've heard the last thing I should do is put an alternator under full load for very long. They're not designed to do that. This is why it's recommended everywhere I've read not to use a primary alternator to charge a house bank. Since many people do that and get away with it, I guess that advice isn't correct.

 

I re-ran my wire size tool using 142 Amps coming out of my Jeep 160A alternator thru the starter battery, 8' one way, and 1% loss. The calculator said I'd need 0000. Accepting a 2% loss shrunk the cable to 0. I'm still in disbelief this is necessary. Am I using the correct amps number for the calculator? It wants to know the maximum amps that will travel through the wire at 12VDC. I just can't believe I'm using the wire size tool correctly. For example, even the Jeep"s own wiring system doesn't use cables bigger than #2 AWG!

 

Another problem is if I must run cable that big inside where people sit, I don't dare leave it unshielded. Once I enclose it in even flex conduit, the heat factor goes up around the cable which increases the size required. To quote a famous king, " 'this a puzzlement!"

 

To try and put a wrap around this thread, based on what all of you have taught me, my best bet to charge my sized house bank is to use an on-board inverter charger. However, the cabling necessary to get the starting battery power to the inverter seems unsolved. I'll have my Jeep builder look to find somewhere inside near the firewall to install the inverter charger. Shortening the length of the run may make the cable size a little safer and more reasonable.

[oldjohnt]

Good Mornin Jerry, wow youre makin me dust off my old books lol I retired from active power distribution design in 91 but its kind of fun to jump back in lol

 

1) "I also have a concern whether the OE alternator can power the load of the on-board inverter and run the Jeep, too. I've heard the last thing I should do is put an alternator under full load for very long. They're not designed to do that. This is why it's recommended everywhere I've read not to use a primary alternator to charge a house bank. Since many people do that and get away with it, I guess that advice isn't correct."

 

I just cant say how well or how long your alternator will perform but I would be "concerned" if you loaded a 160 amp rated unit at 140 to 160 amps for a matter of hours??? HOWEVER if the charger is only a 55 amp unit (were no longer talkin the 80 amp right??) and say the jeep battery draws maybe 40 to 60 amps a short time (but that wont last long or remain continuous) I DONT ENVISION YOUR ALTERNATOR HAVING TO DELIVER ANY 142 AMPS FOR ANY EXTENDED PERIOD, MAYBE 100 TO 125 AMP RANGE. If the charger pumps 55 amps and the inverter powers the charger, allowing for heat losses, I dont see the alternator pumping much more then 60 to 65 amps (inverter draw) and add say temporary 40 to 60 amps until the jeep battery is replenished, that's more like 125 amps max NOT 142..... NOTE these are conservative guesses, the alternator may not have to pump more then 100 amps?????? I cant say exactly sitting here !!!!!!

 

 

2) "I re-ran my wire size tool using 142 Amps coming out of my Jeep 160A alternator thru the starter battery, 8' one way, and 1% loss. The calculator said I'd need 0000. Accepting a 2% loss shrunk the cable to 0. I'm still in disbelief this is necessary. Am I using the correct amps number for the calculator? It wants to know the maximum amps that will travel through the wire at 12VDC. I just can't believe I'm using the wire size tool correctly. For example, even the Jeep"s own wiring system doesn't use cables bigger than #2 AWG!"

If you look here : http://www.usawire-cable.com/pdfs/NEC%20AMPACITIES.pdf you will see 2/0 Cable with not more then three in a raceway is rated for 145 amps. However, I always used the 80% max continuous current de-rating factor meaning I would specify 4/0 as 80% of 195 = 156 amps. BUT if the conductors were not enclosed or jacketed and in free air you can use smaller cable. THAT BEING SAID, if I were building the system at home Id probably use 2/0 individual conductors in free air and sleep fine (Im NOT quoting NEC here folks, Im ONLY saying what I might do and feel it reasonably safe, NO WARRANTY)

 

3) "Another problem is if I must run cable that big inside where people sit, I don't dare leave it unshielded. Once I enclose it in even flex conduit, the heat factor goes up around the cable which increases the size required. To quote a famous king, " 'this a puzzlement!""

 

If you use individual conductors in free air not in raceway, I wouldn't worry so much about the grounded conductor as its near the same potential as the Jeeps frame. I might do something like enclose the hot conductor in that split plastic tubing/cover and use care in cable routing so its NOT up against the frame or near sharp objects etc. Again, this is NOT code, just something to consider. When I run such a cable I bind it by cutting and splitting like a 5/8 rubber heater hose to encircle it then use a zip tie etc to tie that for mounting so theres like triple insulation protection.

 

NOTE we haven't discussed overcurrent protection right at the battery source?????????

 

3) "To try and put a wrap around this thread, based on what all of you have taught me, my best bet to charge my sized house bank is to use an on-board inverter charger. However, the cabling necessary to get the starting battery power to the inverter seems unsolved. I'll have my Jeep builder look to find somewhere inside near the firewall to install the inverter charger. Shortening the length of the run may make the cable size a little safer and more reasonable."

 

I hear you and feel your pain, its easy for me sitting here to throw out all this because I dont have to do the heavy lifting and YES I understand this is easier said then done as there are space problems and mounting and wires etc etc. HOWEVER I still think its possible to mount that inverter "somewhere" and run a couple 2/0 or even 4/0 big honkin cable to its input lugs with an easy 12/3 cord out for the 120 VAC power.

 

I still believe this is the best way to properly SMART charge those AGM's PROVIDED THE ALTERNATOR CAN HANDLE THE LOAD?????????????????? That remains my biggest question for now

 

 

 

Best I have to offer, your money your choice now. See what others have to say don't rely only on me, I'm rusty on this stuff, its been too darn long lol

 

John T