Charging the camper batteries with the truck motor

[GoFish]

I have not been able to get a good charge to the camper house batteries using the truck alternator. I have the dual 105 amp alternator option on my 2004 Duramax for total of 210 amps of potential output. It seems like the regulator is sensing that the truck batteries are charged and it reduces the current output so that the camper batteries only get a trickle.

Has anybody else found a way to get around this problem and allow the camper batteries to get a full charge from the alternators while driving?

[mkirsch]

GoFish wrote:
Thanks for all of your replies. I now feel even dumber than before and that was quite a hurdle.

You asked an electrical question. Electrical questions and online forums almost always combine to form a massive confusing fist fight.

[AnEv942]

GoFish-is your supply thru the solenoid (constant duty?) set up as seperate feed to camper? Or is it feeding, replacing stock 12v feed?

When I set mine up, also 10gage, I ran as an aux, factory charge line is still intact, so new charge is addition to factory. Does require seperate plug. I added amp gauge in line on the aux line so I could see charge. With out any real load I see 2-5 amps on auxillary line, with load or after first turning on 12-15 amps. Usually drops to 8 then downward. I never measured but I'm guessing the factory line at best is suppling 2-3 amps.

IF you engage a high load, refer or something, will the truck input increase?

[DiploStrat]

eb145 wrote:


OP, I'm pretty sure this is exactly what you are looking for.

Ed

Ed, with deepest respect, the CTEK is exactly what he does not need. The CTEK 250 Dual is a B2B with a solar controller built in. It does have a nice, multi-stage charger and it does raise the charging voltage to over 14v, but his Chevrolet already has a multi-stage charger and already runs at over 14v.

The CTEK has a maximum charge rate of 20A while his truck is already capable of charge rates well above 100A.

This kind of device does work well if you have an older truck with a 13v system. (A friend of mine uses a pair of 40A B2B's on his Unimog.)

In either case, he will have to significantly upgrade his wiring.

Finally, if you are determined to use the CTEK system, you really need to add the Smartpass, which boosts your charge rate up to 100A and allows for bidirectional charging to maintain the starter batteries when using solar or shore power. Smartpass

Or, you could simply use THIS with properly sized wire, call it 100mm2.

[eb145]

bcbigfoot wrote:
Here is a DC to DC battery charger/isolator that is discussed in another RV.net thread. http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27446869.cfm

Clicky - about CTEK battery charger

OP, I'm pretty sure this is exactly what you are looking for.

Ed

[DiploStrat]

Secondary regulators, sold as Alternator to Battery chargers or Battery to Battery chargers work. An A2B will achieve a much higher charge rate than a B2B. Sterling A2B and Sterling B2B You can also find B2B's from CTEK. These products work as advertised.

But the simple fact is that the original poster has no need to spend money for either if his alternator/regulator already runs at 14v. And, with a Chevrolet, this is an easy determination. All you have to do is look at the voltmeter on the dash; if the central number is 13, then you either need to boost the alternator voltage (though diodes or something like this: Mechman voltage adjuster

If the number is 14, then all that is needed is upgraded wire and a high capacity solenoid. You can run new wires, or as noted, above, you can add additional wires of the same size or larger. it makes no difference - copper is copper.

A more detailed discussion can be found here: SmartGauge UK Tech info

[bcbigfoot]

Here is a DC to DC battery charger/isolator that is discussed in another RV.net thread. http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27446869.cfm

[Bedlam]

DiploStrat wrote:

GoFish wrote:

… is there a way around this without having to rewire everything?

No, because it is the small wire, and distance to your camper, that is limiting your charge rate.

You can run additional wires from your current setup to increase charging without janking what you already have installed. If your current charge wire is #10, you can run one or two additional #10 wires in parallel with your original run to boost charging capacity.

[wwest]

GoFish wrote:
Thanks for all of your replies. I now feel even dumber than before and that was quite a hurdle.

Some of these comments are just way over my comprehension level, so I don't know if my question has been answered, or not.

I should probably restate my original query. As I am now configured, I take power from the combined battery output tap and send it to a solenoid and on to the camper through a 10ga. stranded wire. It seems to me that the voltage regulator is limiting the output to the camper batteries when I am driving because it senses that the truck batteries are fully charged. I have a Trimetric battery monitor installed and output to the camper batteries with the truck running is only in the 5-8 amp range. It seems like I should be able to get more out of the alternators than that.

In simple English, is there a way around this without having to rewire everything? In my owners manual, it briefly references an option for what it calls an alternate battery and shows an image of a connection that is supposed to be located on the firewall near the rear battery in the truck engine compartment. I have briefly looked for that connector and can't find it.

First, they is NO way to detect/sense, the SOC of a battery while it's under electrical loads. The best that can be done is supply a fixed voltage target/setpoint for the alternator output that will, hopefully, maintain at least a 60-70% SOC, but not high enough to boil off the battery electrolyte.

If you disbelieve then go for a long enough drive to be certain the Chassis battery gets charged, switch the engine OFF, then use a "smart" charger to "measure" the SOC with the battery disconnected from the load.

But the answer to Ops problem.

Go to HF and purchase an 800W DC-to-AC inverter and buy (elsewhere) a good multi-mode battery charger.

Note that the inverter will function even if the supply voltage is at least 10.5 volts. Hook the inverter into the TV 12 volt source and use the inverter output to power the charger.

[stevenal]

Yes, there is a fairly simple way around this without rewiring everything. You can fool your voltage regulator by using the diode method I linked to.

[DiploStrat]

GoFish wrote:

… is there a way around this without having to rewire everything?

No, because it is the small wire, and distance to your camper, that is limiting your charge rate.

[GoFish]

Thanks for all of your replies. I now feel even dumber than before and that was quite a hurdle.

Some of these comments are just way over my comprehension level, so I don't know if my question has been answered, or not.

I should probably restate my original query. As I am now configured, I take power from the combined battery output tap and send it to a solenoid and on to the camper through a 10ga. stranded wire. It seems to me that the voltage regulator is limiting the output to the camper batteries when I am driving because it senses that the truck batteries are fully charged. I have a Trimetric battery monitor installed and output to the camper batteries with the truck running is only in the 5-8 amp range. It seems like I should be able to get more out of the alternators than that.

In simple English, is there a way around this without having to rewire everything? In my owners manual, it briefly references an option for what it calls an alternate battery and shows an image of a connection that is supposed to be located on the firewall near the rear battery in the truck engine compartment. I have briefly looked for that connector and can't find it.

[DiploStrat]

I have a 600Ah bank, made up of Lifeline AGM batteries. Using all electric appliances, my overnight consumption is typically 125Ah. (I have seen as high as 200Ah.)

In my case, 5C is moot, as with 2x125A alternators, the best I could ever achieve is about C/3. (Now the RAM is equipped with 2x200A alternators.) The best that my solar kit can provide is 30A, which is much lower, but still very useful as the solar kit keeps charging long after the engine stops.

The 2013 Chevrolet Silverado has a very sophisticated charging system. When I took delivery of my camper in December it was cold and the truck had been sitting for several months during contraction. My usual charge voltage was 15.5v. My guess is that between winter cold and batteries that had been sitting for a while, the Chevrolet went into some combination of temp adjust and equalization. Once that was complete, about a month later, the voltage dropped to about 14.5v and has stayed down. Will have to see what happens next winter.

This is an extract from the GM shop manual. It specifically notes that the Chevrolet uses a shunt and is temperature compensated. This is a far cry from the voltage regulators of some years ago.
=============================================================================================================================
CHARGING SYSTEM OPERATION
The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:
• Battery Sulfation Mode
• Charge Mode
• Fuel Economy Mode
• Headlamp Mode
• Start Up Mode
• Voltage Reduction Mode
The engine control module (ECM) controls the generator through the generator turn on signal. It monitors the generator performance though
the generator field duty cycle signal circuit. The signal is a 5 volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100
percent. Normal duty cycle is between 5-95 percent. Between 0-5 percent and 95-100 percent are for diagnostic purposes. The following table
shows the commanded duty cycle and output voltage of the generator:
The generator provides a feedback signal of the generator voltage
output through the generator field duty cycle signal circuit to the
ECM. This information is sent to the body control module (BCM).
The signal is a 5 volt PWM signal of 128 Hz with a duty cycle
of 0-100 percent. Normal duty cycle is between 5-99 percent.
Between 0-5 percent and 100 percent are for diagnostic purposes.

Commanded Duty Cycle Generator Output Voltage
10% 11 V
20% 11.56 V
30% 12.12 V
40% 12.68 V
50% 13.25 V
60% 13.81 V
70% 14.37 V
80% 14.94 V
90% 15.5 V
===========================================================================================================================
The obvious point is that the Chevrolet runs well above 14v for a lot of the time. I have no reason to suspect that Ford and RAM are any less sophisticated.

With the batteries in parallel, I can typically recoup 200Ah within three hours of driving.

YMMV, but the simple fact remains, with proper wiring, the original poster's Chevrolet is capable of much better performance than he is seeing.

I find that the biggest reason that people doubt this is that they have simply never seen a truck with wiring much larger than 6 AWG and so they accept that as the limit of the system.

[HMS_Beagle]

DiploStrat wrote:


-- Current: Lifeline AGM batteries spec a charge amperage of up to 5C. Some others actually spec no limit. Open lead acid batteries typically want a lower charge rate.

Lifelines can be charged at no current limit as long as the acceptance voltage is limited. But in any ordinary situation (like down to 40-50% SOC) they will only accept about 0.5C. If you want 5C, you need LFP batteries!

Also, automotive regulators don't seem to be set very high these days. They start out in the low 14s and then settle out in the high 13s, at least the ones I have seen on my trucks. I think they do this on purpose, after all they are intended to charge the starter battery, these are "maintenance free" (meaning mainly you cannot replace the lost water) and they don't want to cook them. So they have a negative temp coefficient built into the regulator (my theory). It doesn't take much voltage loss ( a few tenths) to have a slowly charged/undercharged camper battery. All the more reason to go with solar! I put in #6 wire and a lift gate connector, now I don't even bother to hook it up, the solar provides all the charge needed.

[msiminoff]

HMS Beagle wrote:
Larger than #8 wire may allow higher charge rates, but in most installations still will not make much difference in charge time as you will not see those higher charge rates for long.

Good point. I should have said; "higher initial charge rate".

GordonThree wrote:
What is the name of this connector set? It's impressive looking and looks "marine" in nature.

It is called a "lift gate connector".

-Mark