Alternator Charging ? Again

[BFL13]

I need to use the truck to recharge the batteries for the truck camper when off grid because there is no room for a generator, and solar can't always keep up.

I know you are supposed to upgrade to fatter wire instead of using the existing 7-pin. However, I am not sure what that really means for connecting wires from where to what. I have read here that you should by-pass the truck battery and use the alternator connections. It is a 105a it seems, and it has a lug for the positive wire that goes via some sort of little box which is wired to the battery pos, and the alternator is marked GRD where it is bolted on to its bracket. I do get about one more DC volt by taking the voltage from the alternator's pos lug instead of the battery's.

I just can't understand what people are doing to get their reported 60 amps or whatever from using their alternators. What is the secret?
Thanks.

So far, I have been playing with my long jumper cables, 25 ft of #1 cu/al which have fairly low resistance. Results so far:

A. 7-pin. Gets 10 amps at first then tapers to about 6 amps within four minutes. Truck at idle 600 revs, going to 2000 revs makes little diff.

B. Jumper cables from truck battery to house batts. Gets about 20 amps at first then quickly tapers. Higher revs make little diff.

C. Using the long set of jumpers from truck battery to 2000w MSW inverter, to run a 35 amp (gets 33 amps max) Vector smart charger to the house batts. Gets 33 amps nice and steady, truck voltage holds at around 12.2 volts steady at 600 revs idle.

D. Same as C, but using adjustable voltage modified PowerMax PM3-55 converter. Runs ok, but where it gets 57 amps on shore power, on the MSW inverter on this long wire set, it gets about 50 amps. The truck has a hard time holding its own battery voltage at near 11.7 volts. Amps taper a little as truck starts losing the fight. At 49 amps, revving the truck to 2000 revs from 600 at idle did make a diff. Amps rose from 49 to 51 and truck voltage stopped sliding away.

So it looks like I can somehow run cables back to the truck camper to an inverter to run a charger, solving a few physical layout problems, and it will work, especially if I use the 35 amper. If I use the 55 amper, it will mean putting a brick on the gas pedal or something to hold the revs up for an hour instead of idling with no complications as with the 35 amper. Means 33 AH vs 50 AH for an hour of idling (batteries would be low so no tapering amps then)

Some time ago I used this method with the 35 amper and idled the truck for an hour no problems at all. That was working outside and not having the inverter and charger and wiring all inside so it could be done without going out in the dark and rain. (Which is likely to be the case, since otherwise the solar would keep up, and this charging from the truck would not be necessary 🙂 )

So before I do some renos on the truck camper's set up for all this, is there an easier way to get those good amps from the truck to the house batts? (Where the amps won't taper like crazy from whatever they start out as. I get constant amps with the Vector or the PowerMax chargers, which is the big advantage of using them)

BTW, not related, but the Xantrex MSW inverter will not run the VEC1093DBD at all. It shows code OPP, which means incompatible device (that code is not in the owner's manual, I got that from tech support) It does run the Vector 1092A though. I wonder if the 1093DBD needs PSW. No matter, I can do 33 instead of 40 since I have one of each.

[MEXICOWANDERER]

GM offered the CS-144 alternator as an option on almost all pickups and HD chassis. Different mounting bracket and longer serpentine belt needed. Personally I prefer the 145-amp Cadillac model alt and change the regulator to a 437 and convert to a 4-wire reg plug. Hot idle amperage more than doubles.

I put up with the toad's Bosch 40/90 alternator long enough. A 50/120 Mitsubishi awaits me at my P.O. Back to the land of year-round A/C until I bug out to Guatemala.

[BFL13]

When I did this a few years ago, the inverter was on #1 cu, 18 inches from truck battery, and the truck voltage stayed near 14. This time the inverter is 25 ft away on #1 cu-al. Same 35 amp Vector.

Before, when I added more load to about 55 DCamps of Vectors, the truck voltage just couldn't stay up and it fell right off. This time, it does not fall off but just sits there steady at the lower voltage of 12.2. (so the battery will be at 12.2 instead of the usual 12.5 when truck engine off.(it still has parasite loads) (but at 1.275SG)

I was hoping that 12.2 instead of 12.5 would not matter much for an hour.

[JiminDenver]

I would think if the battery/alt could cover the load easily the voltage would be higher. What you are seeing is what I saw when I ran the A/C off of two panels that almost covered the load. It took hours to get the voltage down but it did come down ever so slowly. Taking a break and getting the voltage of the starting battery back up would be multiple cycles vs one deep cycle. Multiple cycles will shorten its life, too deep of one may kill it.

[BFL13]

With the truck system holding truck battery voltage at 12.2 while the inverter is running, I suppose the truck battery could be losing some AH? I have no idea what the current out would be at that "loaded voltage" It is a starting battery so it can't take much.

Or is the battery still not being drawn down, but it is just showing that loaded voltage and the voltage will bounce right back? It would not take long to recharge the starting battery after the TC charging session has been completed of course. Just leave the truck on a bit longer.

Would it help to stop the TC recharge every 20 minutes and let the truck battery get recharged for a few minutes, then go back at it? That way the truck battery would be doing shallower cycles sort of?

[landyacht318]

And for reference my 1.8 cubic foot 12v Vitrifrigo c51is draws ~32 watts and has a 25% duty cycle or less in 80F ambient.

BUt I do have extra insulation.

My PSW inverter draws 0.24 amps turned on powering nothing
My MSW inverter draws 0.72 amps turned on powering nothing

My MSW inverter turned on powering nothing draws more than my fridge does in an hour, 60% of the time.

BFL, you said before the truck battery was dropping to 12.2v when idling to do the inverter/charger thing. Sounds like you are robbing Peter to Pay Paul.

Peter being the partially charged and now unhappy engine starting battery.

While My alternator is has rather pathetic output at 525 hot idle, this does not mean yours will too. I understand that you need not do anything to continue with the inverter jumper cable charger method.

Your alternator well wired to the house bank, could easily outperform the inverter/charger method.

[westend]

JiminDenver wrote:
I was reading through the thread because I found out I could get a 350a alternator for the Expy and the info may come in handy someday.

What I can add is that I have been looking to add the second fridge next year for extended trips and am going through the same process that I did with the little A/C. I have found that most 1 ft cube fridges pull the same 1.3-1.5a as the larger 2 and 3 foot units. oddly you can find 10 ft units that use little more even though they are 10x the space.

The least draw I have found has been the Edgestar 3.1 two door. It pulls .64a which is only .04a more than a Grape 5 ft 12v fridge. Adding insulation can drop the daily draw down 40%.

Jim,
You have found the holy nugget of wisdom about refrigeration, the smaller ones have almost identical draw as the big ones. As the boxes get bigger, they have more freezer space and different air transfer designs within the box. This can add to electrical draw. My 1.8 cu ft. refer draws 80W. The duty cycle in temperate MN Summer is 1/3-> 1/4.

[JiminDenver]

Thank you for the link. I just hadn't gone back far enough in your post to find it. .8 is one of the lower draws I have seen and I shouldn't be surprised that it ran under that considering the little A/C is listed at 3.9a and runs around 33a 12vDc.

Mex

I have only used the alternator one trip and it was nothing fancy. What got me looking at the alternators was seeing a 250a alternator listed in the specs for the new Expedition. My 03 likely has a 110a but I wouldn't upgrade it unless there was a real reason to.

[MEXICOWANDERER]

If I may...

If the 350 ampere alternator is from Ford, fine and dandy. You will absolutely have to go to the recommended super wide serpentine belt to drive that intense of a load. 1-AWG Is fine up to 10' in length.

Remanufactured 3, 4, & 6-G alternators that boast hopped-up amperage are garbage. Low speed amperage disappears. In a 6 inch case only a ND HAIRPIN alternator will work correctly. Even the haipins should utilize an external rectifier.

Overcooked hopped up alternators remind me of the VW bug craze of the 60's and 70's.

Take a beetle. Spend 1500 dollars on modified engine internals. Get maybe 85 hp

Fuel mileage drops to 15. A Ford Mustang would run circles around it, get better mileage, and not eat the drivetrain due to power.

Use wisdom when planning upgrades.

[BFL13]

JiminDenver wrote:
4-5 amps DC is pretty good actually. Nothing like the 12v compressor units but for the money they hold a tiny amount of food.

If you could, list the unit you have as well as link your fridge thread. Thanks

Here is a thread on this, with a post from me included that has my test results and a link to the fridge.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28416091/gotomsg/28421852.cfm#28421852

[JiminDenver]

4-5 amps DC is pretty good actually. Nothing like the 12v compressor units but for the money they hold a tiny amount of food.

If you could, list the unit you have as well as link your fridge thread. Thanks

[BFL13]

Jim, I had a thread on small 120v fridge draws early this year sometime with similar numbers.

The 3.2 we did get (the 3.3 we wanted was too tall by one inch 😞 ) draws about 4 to 5 amps DC while on inverter when fridge is on. Not exact on how much it is on, but it eats AH over the 24 hrs. That means the solar has to do 10 amps during the day and none at night to stay even with the fridge over the whole 24.

[JiminDenver]

I was reading through the thread because I found out I could get a 350a alternator for the Expy and the info may come in handy someday.

What I can add is that I have been looking to add the second fridge next year for extended trips and am going through the same process that I did with the little A/C. I have found that most 1 ft cube fridges pull the same 1.3-1.5a as the larger 2 and 3 foot units. oddly you can find 10 ft units that use little more even though they are 10x the space.

The least draw I have found has been the Edgestar 3.1 two door. It pulls .64a which is only .04a more than a Grape 5 ft 12v fridge. Adding insulation can drop the daily draw down 40%.

[BFL13]

Thanks Mex. If I get ambitious enough I will try that.

Meanwhile, since it has run the truck ok since new in late 2002, I expect it will keep doing so. That dim light must be from some leakage so it just adds to the other parasite draws when the truck is parked.

I have a solution to the TC battery charging problem where the truck engine and the inverter act as an "inverter-generator" to run the Vector 35 amper smart charger. That does constant 33 amps in the bulk stage, so I think that will do more AH in an hour than alternator charging where the amps taper, even if it started out at higher than 33 amps with the alternator improved and fatter wires.

The installation "issues" of the inverter, charger, and cables from truck back to camper have all been solved, so I will go with that method. Turned out I was lucky in the way the TC is laid out inside.

That also gets some more use from this extra gear I have lying around that were "spares" for the 5er left over after various upgrades to that.

[MEXICOWANDERER]

L and I/F are the 2 center terminals. Your alternator HAS NO EXTERNAL VOLTAGE SENSING CIRCUIT. The S terminal wire is missing. The P terminal is a stator tap for AC pulse counting. Not used.

Light circuit in harness is seeing enough ground + bat potential somhow to allow the lamp to glow. So harness or dash board printed circuit board has a fault. Most likely a ground loop due to a POS high resistance firewall connection to ground. Stupid GM electro dipped entire chassis for corrosion coating and caused bad grounds. Another alternator would have done zero to change this.

I ran 16 AWG ground wires from PC board to new firewall ground screw with steel shined bright area. Gas and temp gauges became more accurate. Solid black 22 gauge wires from PC board are OEM ground wires.

Stupid stupid motorhome manufacturer. You can buy a good quality 4-wire reg plug with pigtails. Wire it just like your original plug.

The S wire gets connected to your engine battery + NO SWITCH. This will add .3 volt and auto switch the 1116411 regulator off the internal sensing circuit. This is a simple, piece of cake FOOL PROOF modification that will make your rig like the other 98% of motorhomes on the road.

Plugs are sold in auto parts stores. They are universally superb quality.

Wire that S terminal as close to actual battery post + as you can get it.

Start the engine and put that CS130D to work for a change. It's been strumming its pud charging your batteries.