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Old 05-17-2012, 08:12 AM   #11
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Originally Posted by Triguy View Post
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 ?
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Old 05-17-2012, 08:28 AM   #12
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Originally Posted by RonaldMcDonald View Post
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.
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Old 05-17-2012, 08:45 AM   #13
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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 .
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Old 05-17-2012, 09:05 AM   #14
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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.
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Old 05-17-2012, 09:37 AM   #15
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Originally Posted by RonaldMcDonald View Post
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.
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Old 05-17-2012, 09:50 AM   #16
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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!
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Old 05-17-2012, 03:17 PM   #17
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Quote:
Originally Posted by RonaldMcDonald View Post
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.
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