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Old 05-12-2012, 07:42 PM   #1
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Question Surplus Current?

In preparation for getting a new Puma 253-FSB, I just bought a 2011 Silverado 2500 diesel. It came with two batteries and dual 125 amp alternators. It seems a shame to waste all that extra capacity, but the 10 AWG wires in the standard harness are far too small to make much use of it.

We mostly boondock, so i would like to be able to use more of that 150 amps to charge the house batteries? Is there a convenient way to do that? Where would i connect an additional cable? Does it make any difference which alternator I draw from?
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Old 05-12-2012, 09:08 PM   #2
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could you not use jumper cables?
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Old 05-12-2012, 09:15 PM   #3
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I could use jumper cables when I'm not driving. I Would like to find a more robust solution.
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Old 05-12-2012, 09:39 PM   #4
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Why not run a heavier gauge wire to the trailer with a heavy duty plug. Jump off the same connection as the 10 AWG wire.
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Old 05-12-2012, 09:54 PM   #5
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From the 7 pin connector to the 5er is not a problem. However, I haven't figured out where the battery lead in the 7 pin connects in the front of the truck. Also, since not all trucks have two alternators, the 7 pin would probably be connected to the standard alternator. I would probably be better off connecting to the aux. alternator.
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Old 05-13-2012, 01:10 AM   #6
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10 gauge wire is good for 30 amps. Now how much current do you think you can put in to your batteries while driving down the road? As for boon docking and charging the batteries, jumper cables are going to be your best source. You might find a plug for a golf cart or electric fork lift that will handle 50 amps at 12 VDC, but not much more. Anything else is going to be impractical.

As for which alternator to draw from, they are in parallel, and can;t be separated. The batteries are in parallel also, and can't be separated. With duel alternators, you must have the snow plow package. Thinking you can pump 250 amps in to your camper batteries will never happen, as it would fry them in a short time. The voltage regulator is going to limit the current, and they will charge at a rate they can stand. Maybe you should read the 12 volt side of life. Sorry I don't have the URL handy, but a search should find it.

As for the 7 pin pin plug and the battery lead, I think it goes through a relay, and is only "hot" when the key is on. This keeps the camper from draining your truck batteries if parked and connected. If you are thinking of upgrading the wire size, the 7 pin plug will only handle so much current, so waste of time.

I often read post on here where people say the tow vehicle will not charge the rv battery, but I find, when all is well, it works very good. People with problems usually have corroded plugs, corroded connections, bad batteries, and the list goes on.

Good luck with what you decide, but if you think you can pump 250 amps in to your trailer batteries, better have on a safety suit and safety glasses for when they explode.
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Old 05-13-2012, 04:00 AM   #7
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Thank you Windrider, you make some good points.

As you guessed, this truck does have the snow plow package, but never had a plow or roof lamp installed. It has the off road skid plates, but from examining the underside, I don't think it was ever used off road. It has the heavy duty trailering package but no fifth wheel hitch and the receiver looks like it was never used. It has a factory bed liner with not a scuff mark. I can't figure out what is was used for. And yes, I know that I can't put a hitch on top of the liner.

I am glad to hear that the alternators and truck batteries are in parallel I suspected that they might be, but I had not been able to confirm it. This would suggest that there must be a single voltage regulator. By the way, do you know why a snow plow would need that much current?

I certainly don't expect to be pumping 250 amps into the batteries. However, I will be using four 6 volt batteries in series / parallel. It would not be at all unreasonable to pump 50 or 60 amps into them when they are low, without frying them.

The #10 wire is good for 30 amps, but the #10 ground wire will also have to carry the battery current as well as the current for all of the running lights on the 5er. There is also a fuse (#63) for the trailer battery circuit. I haven't yet had a chance to check it out, but I would guess that it would not be more than 20 (or at most 30) amp.

You mentioned that "I often read post on here where people say the tow vehicle will not charge the rv battery, but I find, when all is well, it works very good. People with problems usually have corroded plugs, corroded connections, bad batteries, and the list goes on."There may be another reason. I noticed in the manual that "If charging a remote (non-vehicle)
battery, press the Tow/Haul Mode button, if equipped, located at the end of the shift lever. This will boost the vehicle system voltage and properly charge the battery. There is also "The fuses for these two circuits (battery feed and trailer brake) are installed in the underhood electrical center, but the wires are not connected. They should be connected by your dealer or a qualified service center." It is possible that some people might not have the battery feed connected.

Thanks again for your help,
Joel
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Old 05-13-2012, 07:28 AM   #8
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Quote:
Originally Posted by Great Horned Owl View Post
Thank you Windrider, you make some good points.

As you guessed, this truck does have the snow plow package, but never had a plow or roof lamp installed. It has the off road skid plates, but from examining the underside, I don't think it was ever used off road. It has the heavy duty trailering package but no fifth wheel hitch and the receiver looks like it was never used. It has a factory bed liner with not a scuff mark. I can't figure out what is was used for. And yes, I know that I can't put a hitch on top of the liner.

I am glad to hear that the alternators and truck batteries are in parallel I suspected that they might be, but I had not been able to confirm it. This would suggest that there must be a single voltage regulator. By the way, do you know why a snow plow would need that much current?

I certainly don't expect to be pumping 250 amps into the batteries. However, I will be using four 6 volt batteries in series / parallel. It would not be at all unreasonable to pump 50 or 60 amps into them when they are low, without frying them.

The #10 wire is good for 30 amps, but the #10 ground wire will also have to carry the battery current as well as the current for all of the running lights on the 5er. There is also a fuse (#63) for the trailer battery circuit. I haven't yet had a chance to check it out, but I would guess that it would not be more than 20 (or at most 30) amp.

You mentioned that "I often read post on here where people say the tow vehicle will not charge the rv battery, but I find, when all is well, it works very good. People with problems usually have corroded plugs, corroded connections, bad batteries, and the list goes on."There may be another reason. I noticed in the manual that "If charging a remote (non-vehicle)
battery, press the Tow/Haul Mode button, if equipped, located at the end of the shift lever. This will boost the vehicle system voltage and properly charge the battery. There is also "The fuses for these two circuits (battery feed and trailer brake) are installed in the underhood electrical center, but the wires are not connected. They should be connected by your dealer or a qualified service center." It is possible that some people might not have the battery feed connected.

Thanks again for your help,
Joel
When you depress your TOW/HAUL button it does not "BOOST" the voltage. What it does is keep th engine RPMs up by either late shifting the transmission or keeping the torque convertor unlocked thus resulting in more amperage available. Your alternator amperage output is not rated at idle/low speeds it requires higher RPMs to make the current. The voltage will/should remain constant around 14.4V unless at idle and the load exceeds the alternator output
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Old 05-13-2012, 08:01 AM   #9
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I read these threads where people charge their trailer batteries through the vehicle and would really like to see some numbers showing amps and volts at the trailer batteries. Let me just throw out some thoughts and questions so that others can educate me.

I'm NOT saying its impossible, but I do question the effectiveness because of the following.

My experience has been that charging through the TVs alternator and Bargeman plug while towing is good for a nearly fully charged bank of trailer batteries. It can also work well with depleted batteries but it takes many hours of driving to charge a battery bank that's at 50%. I know that's not what you are talking about, but I mention it for other readers.

So, what I understand you and others want to do is to run heavier gauge wire directly from the alternator to the trailer for when you are at your site. The hope is that you have a way to charge your trailer batteries using the truck as a big portable battery charger.

In general, a smart charger or your 5ers converter has the appropriate algorithm to charge deep cycle batteries. Does the truck have that same algorithm being that it's designed to charge car batteries that are rarely discharged by more than 5% of their capacity? In other words, wouldn't it regulate the amps down very low and relatively quickly?

1) Do you plan to idle the truck at the campsite in order to charge? And, for how many hours?

2) Has anyone charged this way, removed the surface charge appropriately and then measured the voltage of their battery bank? What were the results?

2) What are the amps and volts measured at the battery after one hour of charging with an idled TV? After 2 hours? Etc.

3) If charging through the alternator at idle, wouldn't the fully charged truck batteries force the amps to a trickle to avoid overcharging? If so, the trailer batteries would not get the boost they need to charge from a 50% state.

4) Connecting your fully charged TV batteries to your depleted RV battery bank directly with cables goes against the rule that only like size, like age and like batteries can be connected. It was not clear to me that was what you intended but I thought I'd throw it out there.

Food for thought and lots of questions about this method.
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Old 05-13-2012, 08:35 AM   #10
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I would like to hear your response as well.

Scott is right on regarding truck charging vs a generator and battery charger / on board converter.

I use the TM2025RV battery monitoring system when I dry camp and I can recharge my 150AH bank from 50% to 98% using the generator in about 6 hours using the on board converter (initial charging current about 28 amps stepping down to about 500 milli-amps as the battery fills to avoid damage like it is designed to) and using the Ship-n-Shore battery charger it takes 4 hours (it uses a slightly higher initial charging current but never goes below 2 amps).

When using the battery charger I MUST shut off the master switch to the camper; pull the caps on the batteries; and leave the basement door open. The electrolyte "boils" quite vigorously when on the battery charger and I always need to top off the cells with distilled water.

We hooked up the camper last winter (2010) with a low battery (65% on the meter) in the morning when leaving our Key West "roost" and drive to Miami Everglades Campground and charged with our Duramax high output alternator.

After driving about 3 1/2 hours, our battery state was 75% of capacity. By nightfall our batteries were at 99% and did not show 100% until the next morning.
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