My trucks alternator is rated at 150 amps. Its starting battery is your typical 600 CCA AC Delco variety.My goal is to increase charging capability through the 7 pin pigtail connector near the hitch. Is this possible via a larger TV battery or alternator? I recently upgraded from 1 group 24 battery in the TT to 2 GC2 6 volts in series. Current setup doesn't provide much charging when underway, even after 5-6 hours of driving. I know I can install a DC to DC charger in the trailer. I'd have to run a dedicated line from under the hood to the front passthrough storage compartment of the trailer. Just wondering if there was an easier route.Don't want to invest in solar as I wont utilize it much. An 8 week to Alaska next summer is really what I'm planning for. Otherwise, we rarely boondock. It would be nice to drive for 4-5 hours and have a "topped-off" battery bank for each leg of the trip.Any suggestions?

I'd run dedicated wiring so at least your trailer battery gets nearly the same voltage as the engine battery.The voltage your engine battery gets is decided by the vehicle's voltage regulator, and none of these are programmed intending to quickly and fully recharge depleted batteries. Mostly they are designed to never overcharge, and as such, will drop to mid to high 13's relatively quickly, but all vehicles will vary in the max voltage and for how long it is held.Only if your alternator was incapable of meeting all the loads applied to it would increasing its rating prove beneficial, and likely only at higher rpm, not idling.Likewise a larger better starting battery is not going to assist trailer battery charging.I'd get the following 6awg harness or similar, and run it to alternator + and a - mounting bolt. Disconnect the connector manually when parked for any length of time so trailer cannot discharge engine starter battery.

landyacht318 wrote:I'd run dedicated wiring so at least your trailer battery gets nearly the same voltage as the engine battery.The voltage your engine battery gets is decided by the vehicle's voltage regulator, and none of these are programmed intending to quickly and fully recharge depleted batteries. Mostly they are designed to never overcharge, and as such, will drop to mid to high 13's relatively quickly, but all vehicles will vary in the max voltage and for how long it is held.Only if your alternator was incapable of meeting all the loads applied to it would increasing its rating prove beneficial, and likely only at higher rpm, not idling.Likewise a larger better starting battery is not going to assist trailer battery charging.I'd get the following 6awg harness or similar, and run it to alternator + and a - mounting bolt. Disconnect the connector manually when parked for any length of time so trailer cannot discharge engine starter battery.Thanks for the response. 2 follow up questions. If my DC to DC charger is rated at 40 amps (Renogy has one), would it be a bit taxing on the 150 amp OEM alternator? Any benefit to upgrading to a 220 amp alternator in this case?Secondly, do these dc to DC chargers act just like a conventional onboard RV multiphase converter? Bulk to absorption to float? From my understanding, with this setup, I would rarely get above 80% stage of charge after a 3 hour drive, right?

I would stick with the existing charge wire and just get the DC/DC booster mounted on the trailer. You will need to be 10 amps rated lower than the charge line. Most of these lines are fused at 40 amps so you are looking for the Renogy 20 amp DC/DC charger. The manual says you can use the 40 amp rated on a 40 amp fuse but I don't buy that.Three hours at 20 amps is actually a good charge into the battery. The existing alternator will do just fine. Yes it does the three stage charging routine putting full voltage right on the battery terminals and will be a huge improvement. Use the setting for 14.7 volts on the pair of GC2.Charge to 90% is fairly quick at this voltage and the last 10% takes some extra time no matter how many alternator amps, charging capacity or wire size.

CJM1973 wrote: If my DC to DC charger is rated at 40 amps (Renogy has one), would it be a bit taxing on the 150 amp OEM alternator? Any benefit to upgrading to a 220 amp alternator in this case?Secondly, do these dc to DC chargers act just like a conventional onboard RV multiphase converter? Bulk to absorption to float? From my understanding, with this setup, I would rarely get above 80% stage of charge after a 3 hour drive, right?How taxing it would be to the alternator would depend on how long your depleted batteries could suck up 40 amps, and how much other loads the alternator is having to power, like headlamps@~15 amps, blower motor on high @~18 amps, ect. My 1989 engine at 2k rpm requires 12.2 amps to run ignition and fuel pump, not including field current to alternator. Other vehicles will vary.Heating of the alternator is the issue, and how hot it gets depends a large amount on the vehicle's engine bay, and the speed one is travelling. I can max mine out at 120ish amps@ 65mph and the stator does not exceed 138f, but idling parked at 50 amps max and it shoots upto 220f in a few minutes. An alternator with a bigger rating 'should' be able to handle or exhaust the heat better.I have no experience with the DC to DC chargers sold as such, but I do believe they take whatever vehicle voltage is allowed by the vehicles voltage regulator and try to do 3 stage battery charging stepping it both up and then down once it has decided to 'float' them.I'd not want to be limited to the Renogy 40 amp max, but I have an externally regulated alternator and use a modified voltage regulator so I spin a dial to choose a voltage and watch voltmeter and ammeter respond accordingly.I had to trick my engine computer in order to do this without setting off the check engine light, but it has been a great reliable modification.I do make use of Dc to DC voltage boost, and voltage buck devices, but I have not tried to add one to a 7 pin trailer harness. I did buy a '1800' watt voltage booster to experiment with, but it was so poorly soldered and things went pop, and smoked a wattmeter rated upto 60 volts when I had it set to 24v with little load, then changed the load. I have a 150 watt voltage booster that works well considering it was sub 3$, there are 300 400 and 600 watt ones sold too. I've used this booster to equalize one battery at 16.2v from another at 12v which had a regular charger on it. Some of these have current limiting potentiometers so you could limit it to ~15 amps to save the 7 pin wiring harness.Some have done the inverter on engine battery, powering a high amp charger in the trailer, over a quality 120vac extension cord, in your situation. If the inverter can draw more than the alternator can make then it feeds off the engine battery when charging the depleted trailer batteries at a high rate. In this case a larger engine battery gives more of a cushion when rpms are low or one forgets to turn off inverter when parked. One needs to keep in mind engine starting batteries do not appreciate being cycled, and perhaps employ a marine battery instead when one is due for a new engine starting battery.There's lots of ways to get more juice from alternator to depleted trailer batteries, and no 'one' single correct way, no matter how loudly the opinion is typed.-Fat copper to trailer batteries and whatever voltage is allowed by vehicle, is what it is.Dc to DC chargers, over adequate cabling.Inverter on engine battery to feed charger on trailer battery over a good ac extension corda simple dc voltage booster on the 7 pin wire.All are valid ways, and the choice can be influenced by what voltage the vehicle allows when the alternator is hot.The big enemy is voltage drop, as depleted batteries only getting 13.6v at their battery terminals will be accepting 1/3 to 1/2 that they would had 14.7v been reaching the terminals. I get a lot of bile about this 1/2 to 1/3 cobservation, but I have ammeters and voltmeters on my dash next to my voltage control dial, so this is actual repeatable observation and the main variable over the last 4 years has been the battery condition, 1/3 when newer, now closer to 1/2.When disbelievers call me out its like one is travelling 60mph, as indicated by a radar sign, highway milemarkers and a clock, and ones own speedometer, but someone else is saying you are only doing 48mph based on their beliefs alone.1/2 to 1/3 the amp flow is real data, when 13.6v reaches the terminals compared to 14.7v. Other batteries might vary some, but not a lot.as far as how much charging you can get done driving in x amount of time, it is all dependent on how low your batteries were when you started charging/driving, and how many amps you can feed them and this is dependent on the voltage reaching their battery terminals.regardless, it basically is impossible to recharge lead acid from 80% to 100% charged in less than 3.5 hours assuming ideal voltages reaching battery terminals, But 2.5 hours at ideal charge voltages in the mid 14's can at least get one in the 97% state of charge range, where 13.6v might get one from 80% to 84% in the same amount of time.The more aged the batteries the longer the 80% to 100% takes, especially at lower charging voltages.

I forgot to ask; if I do proceed with the DC to DC charger, do I wire it directly to the + battery terminal or + alternator lead? The renogy diagram shows multiple methods.Also, what type of connector is preferred from TV to trailer? Wire will be 4 or 6 awg.

Tow Vehicle Battery and Alternator | Good Sam Community

Vintage465
Nomad
Feb 27, 2020
There is a blog called the "Adventurous Way". A young man named Matt Knight and his wife(Mrs. White?)are boon docking there way thu all the state parks. He has posted several "charging" upgrades he did on his rig. The last one I read was specific to this subject. He detailed it from start to finish. He got real successful results. Successful enough to cause me to consider.....but I have several other irons in the fire right now! And just for the record, I know nothing about blogs, I just stumbled upon it as someone posted a link to this episode of the blog on an Outdoor-RV forum or Outdoor-RV Facebook page.
beck_vega
Explorer
Feb 27, 2020
You can try bamaboys towing.
Rbertalotto
Explorer
Feb 26, 2020
LC Terminal = ????

We have no idea what this is for. Even Will Prowse couldn't understand the need. One of these days I'm going to call RENOGY to find out.

Will Prowse Video

There is a fuse with a plastic cover that I had in my junk box from back in the day when I installed high end car audio systems. I cut a hole in the plastic cover and mounted a simple SPST illuminated switch. This switch could be mounted anywhere.....
CJM1973
Explorer
Feb 26, 2020
Rbertalotto wrote:
BTW...These photos do not show a quick disconnect on the 12v+ lead that is feeding the on/off switch. In this configuration, no wire is needed from the licence plate wire.

Thanks for posting the pics. Very helpful. What is the LC terminal for? So you wired in a fused switch between the (+) input and control terminal?
Rbertalotto
Explorer
Feb 26, 2020
BTW...These photos do not show a quick disconnect on the 12v+ lead that is feeding the on/off switch. In this configuration, no wire is needed from the licence plate wire.
Rbertalotto
Explorer
Feb 26, 2020
Actually, I use one Renogy DC to DC charger between the two vehicles. Using ANDERSON high current connectors, I can swap the unit back and forth.

I installed an ON / OFF switch right on the charger so I can shut it off when not needed. I run the DC control wire from my licence plate light wiring. In this way, when the lights are on, the DC to DC charger is on. And I don't need to run another wire from the front of the vehicle.

Battery Connection at tow vehicle
CJM1973
Explorer
Feb 26, 2020
Rbertalotto wrote:
I have two tow vehicles, RAM 2500 with 220a alternator and Toyota Venza with 150a alternator. I use a Renogy 40a DC to DC charger in both for charging batteries in a small off-road tent camper or a large toy hauler. Both vehicles have 2g wire from front battery to charger in rear.
The Renogy works way above my expectations. Amazing product.
I've been experimenting using my vehicle to idle and charge the battery. After 20 minutes charging I'm seeing very little heat rise on either alternator.using laser thermometer. And with a AGM group 31, 100ah, 60% battery, I'm back up to 90% after 20 minutes.
I no longer carry a bulky generator to off grid charge batteries when the sun isn't hitting my solar panels.
Do a Search on YouTube for Will Prowse. He is amazing and has done a great test on this Renogy unit.

Thanks for the late input. Good to hear that it's been working great for you. I have yet to install the Renogy DC to DC charger in my tow vehicle as we are still in the middle of winter in Michigan. How did you wire the control terminal on the unit? Did you use your tow vehicle's ignition circuit? I have 4G wire (both pos & neg) to run from the TV's battery to the input on the Renogy unit. I'm wondering if I can just tap into the trailer's tail lights or do I need to run a dedicated 16-18G wire from the vehicle's ignition wire. House Batteries and Renogy are installed in a tongue box on the travel trailer. I would prefer only to have one 2-pin connector from TV to trailer. Just curious to how yours is wired.
Rbertalotto
Explorer
Feb 26, 2020
I have two tow vehicles, RAM 2500 with 220a alternator and Toyota Venza with 150a alternator. I use a Renogy 40a DC to DC charger in both for charging batteries in a small off-road tent camper or a large toy hauler. Both vehicles have 2g wire from front battery to charger in rear.
The Renogy works way above my expectations. Amazing product.
I've been experimenting using my vehicle to idle and charge the battery. After 20 minutes charging I'm seeing very little heat rise on either alternator.using laser thermometer. And with a AGM group 31, 100ah, 60% battery, I'm back up to 90% after 20 minutes.
I no longer carry a bulky generator to off grid charge batteries when the sun isn't hitting my solar panels.
Do a Search on YouTube for Will Prowse. He is amazing and has done a great test on this Renogy unit.
time2roll
Nomad
Nov 11, 2019
CJM1973 wrote:
One last question regarding my new AGM battery bank. What are the ideal charging parameters to set my AC to DC converter at? Bulk, absorption, and float.
The battery manufacturer will be the best resource on charging specifications.
BFL13
Explorer II
Nov 11, 2019
Undercharging, not overcharging will be the issue. You need an ammeter to tell when amps are down to 0.5/100AH. That does not mean 1.5a for the bank of three, since the middle battery will not get its full share. I use my Trimetric as the ammeter. You need to do each battery separately to true full as often as possible.

On a trip it is too difficult to do all this right, so it is what it is. At home, you can do it right. See the AGM charging guide here, scroll down

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf