Surplus Current?

[Great Horned Owl]

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?

[caper]

could you not use jumper cables?

[Great Horned Owl]

I could use jumper cables when I'm not driving. I Would like to find a more robust solution.

[caper]

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.

[Great Horned Owl]

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.

[LadyWindrider]

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.

[Great Horned Owl]

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

[wrenchrob]

Originally Posted by Great Horned Owl

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

[Triguy]

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.

[Herk7769]

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.

[RonaldMcDonald]

Originally Posted by Triguy

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.

It seems to me that if your are wired in parrallel with the alternators, the voltage regulators wouldn't care what the TV batteries are charged at. Isn't it just a voltage regulator and not a current regulator?

I think a separate large cable, fusing and connector would have to be installed between the TV and RV. Large enough cable and connector to handle the current. Fuse would have to be sized to not overcurrent the wiring.

This wouldn't be optimal due to the differences in the charging requirement for standard truck batteries and deep cycle batteries, but would allow for substantial charge.

Is there a commercial inverter/deepcycle charger available or would you have to have a large inverter powered by the TV to supply a deep-cycle charger ?

[Herk7769]

Originally Posted by RonaldMcDonald

It seems to me that if your are wired in parrallel with the alternators, the voltage regulators wouldn't care what the TV batteries are charged at. Isn't it just a voltage regulator and not a current regulator?

I think a separate large cable, fusing and connector would have to be installed between the TV and RV. Large enough cable and connector to handle the current. Fuse would have to be sized to not overcurrent the wiring.

This wouldn't be optimal due to the differences in the charging requirement for standard truck batteries and deep cycle batteries, but would allow for substantial charge.

Is there a commercial inverter/deepcycle charger available or would you have to have a large inverter powered by the TV to supply a deep-cycle charger ?

IMHO, this is a recipe for a battery disaster while driving.

As stated in just about every deep cycle battery FAQ around (including ours) single stage (full blast) charging regardless of battery capacity will boil your battery dry without constant monitoring. If the charging current is not reduced as the battery fills, excess heat is generated. That heat gets dumped into the electrolyte and it will boil it away in short order.

Do this at your peril.

[RonaldMcDonald]

Originally Posted by herk7769

IMHO, this is a recipe for a battery disaster while driving.

As stated in just about every deep cycle battery FAQ around (including ours) single stage (full blast) charging regardless of battery capacity will boil your battery dry without constant monitoring. If the charging current is not reduced as the battery fills, excess heat is generated. That heat gets dumped into the electrolyte and it will boil it away in short order.

Do this at your peril.

IMHO, There have been deepcycle batteries around many years before the high tech. chargers were designed. They had to be charged somehow?? I would monitor them also but doubt that a truck alternator at 13.8 to 14 volts would blast a deepcycle battery but rather undercharge it .

[MtnGuy]

I don't have any proof of my batteries charging during travel, other than my batteries have more voltage when I get home from a dry camping excursion, then when I left the campsite.

The same was true when I had my Trailmanor with dual 12 volt batteries, and I had the 12 volt fridge heating element and fridge coil circulation fan running during travel. Unless it was a short trip, the Trailmanor battery monitor always showed a charged reading when I arrived at my next destination.

[Herk7769]

Originally Posted by RonaldMcDonald

IMHO, There have been deepcycle batteries around many years before the high tech. chargers were designed. They had to be charged somehow?? I would monitor them also but doubt that a truck alternator at 13.8 to 14 volts would blast a deepcycle battery but rather undercharge it .

I respect your opinion. Just remember there is a difference between charging voltage and charging current.

A multistage charger reduces charging current and varies charging voltage as the battery fills to avoid damaging the battery or overheating the electrolyte. I also use a high capacity charger 4 stage charger when in camp to fast charge my batteries, but I have the caps off and top them up with distilled water before I start and after I am done.

It is tough to monitor them while driving is all that I am saying.
Wish you the best of luck with whatever you decide.

[RonaldMcDonald]

Originally Posted by herk7769

I respect your opinion. Just remember there is a difference between charging voltage and charging current.

A multistage charger reduces charging current and varies charging voltage as the battery fills to avoid damaging the battery or overheating the electrolyte. I also use a high capacity charger 4 stage charger when in camp to fast charge my batteries, but I have the caps off and top them up with distilled water before I start and after I am done.

It is tough to monitor them while driving is all that I am saying.
Wish you the best of luck with whatever you decide.

You're correct about the multi-stage charger regulating the the voltage and current but they are designed to give the maximum charge at the quickest rate without damage to the battery. On a vehicle voltage regulated charging system , the current isn't regulated , the voltage is ,but as the battery being charged reaches the charging voltage, the current drops off to a trickle. Therefore in my opinion the deep cycle batterys would just be undercharged. I don't believe they would boil out anymore than your standard truck battery would boil out.
Thanks for your input. You offer alot of great and awesome information and material to this forum!

[Triguy]

Originally Posted by RonaldMcDonald

It seems to me that if your are wired in parrallel with the alternators, the voltage regulators wouldn't care what the TV batteries are charged at. Isn't it just a voltage regulator and not a current regulator?

I think a separate large cable, fusing and connector would have to be installed between the TV and RV. Large enough cable and connector to handle the current. Fuse would have to be sized to not overcurrent the wiring.

This wouldn't be optimal due to the differences in the charging requirement for standard truck batteries and deep cycle batteries, but would allow for substantial charge.

Is there a commercial inverter/deepcycle charger available or would you have to have a large inverter powered by the TV to supply a deep-cycle charger ?

Ronald - thanks for your thoughts. Lots of good points there.

Yes, the truck's alternators regulate voltage because its set up for power supply; not charging deep cycle batteries.

I still say that you cannot charge batteries of different sizes and types in the same circuit without damaging some or all of the batteries regardless of using the alternator as a battery charger.

Here's an example ...

Say that the house batteries were at 60% SOC when starting to charge through the alternator. Because they are in parallel, current will flow from the starter to the house bank in order to equalize (unless the banks are isolated), wouldn't it?

If the alternator runs many hours, than equalization will occur and both house and starter batteries would charge eventually. Not optimal, as you say, but it would charge the entire bank over time.

But does anyone want to idle their truck for hours to charge this way? And, if the charge was less time - say 30-60 minutes - than both batteries would equalize to above 60% and below 100%. The starter batteries were not made to do this. Starter batteries are not designed to discharge that deeply and then recharge due to their thinner plates. How many charge cycles like that can they take?

It won't be good for the house batteries either because undercharging of any battery to only 80-90% of capacity will allow sulfation of the battery using the 10-20% of battery chemistry not reactivated by the incomplete charging cycle.

So, I guess if doing it this way, plan on the time to idle the truck long enough for a full charge. Also plan on the batteries dying faster than they should.

In my opinion, the process as discussed is a very poor substitute for a decent portable generator and a smart charger.

But there is a proper way to do this. Full timers on sailboats achieve the desired results, but its more involved than what we've discussed. They parallel the two banks and use dual-purpose battery isolation/selector switches, a second marine alternator built for continuous duty with a smart external regulator plus some other modifications. Its an entire cottage industry for them and more important than it us to us because of the consequences of running out of power on the water.

I would spend a lot of time learning from them if I was interested in doing this type of setup.