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Old 10-03-2022, 01:10 PM   #1
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What performance difference can I see with a DC to DC converter?

What kind of charging performance difference I can see if I were to get a DC to DC converter installed. My understanding is this would impact charging via the 7-pin from my truck. I currently have two Battleborn LiFePo batteries (considering adding 2 more). I also have 300 watts of solar already on the roof. I'm just trying to understand what the difference would be and if it's worth it.
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Old 10-03-2022, 01:45 PM   #2
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Two major differences from what I see...

1) The lithium batteries will always charge at the correct voltage and according to the proper protocol. You can set the specific protocol your battery manufacturer recommends.

2) if you run larger wires from the tow vehicle battery to the rear of the truck and feed the DC-to-DC with this connection, you have the potential to have a much higher amp charge than what your stock 7-pin wiring will ever do. Could be helpful if you're going from campsite to campsite on a rainy day and hope to have full batteries when you arrive.
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Old 10-03-2022, 01:50 PM   #3
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The difference will be no charging without the converter versus charging of somewhere between 5 amps and maybe 50 or so amps depending upon how the converter is wired. Without the DC-DC you pretty much need to disconnect the charge wire on the 7 pin.
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Old 10-03-2022, 03:13 PM   #4
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What kind of charging performance difference I can see if I were to get a DC to DC converter installed. My understanding is this would impact charging via the 7-pin from my truck. I currently have two Battleborn LiFePo batteries (considering adding 2 more). I also have 300 watts of solar already on the roof. I'm just trying to understand what the difference would be and if it's worth it.
Even lead acid batteries benefit from DC to DC chargers. These offset the voltage drop on the wiring from the alternator to the trailer battery. Think of them as a booster pump for the voltage after it arrives in the trailer. It can take the 10 volts 30 amps that arrives in the trailer after voltage drop and create 25 amps at 14 volts that can properly charge your battery. I like the Renogy 30 amp DC to DC charger because it has a on/off trigger. I wire this to the running lights power so when the lights are on the tow vehicle charges, when the lights are off the solar is primary and the tow vehicle charger secondary. This saves fuel by not charging from the alternator. It allows the solar charger to maximize its potential. Often the chargers will compete and the solar will back down thinking the battery is fully charged. All trailers should have a DC to DC charger.
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Old 10-03-2022, 03:53 PM   #5
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...I like the Renogy 30 amp DC to DC charger because it has a on/off trigger. I wire this to the running lights power so when the lights are on the tow vehicle charges, when the lights are off the solar is primary and the tow vehicle charger secondary. ....
The Victron Orion also can be wired with an on/off trigger. The manual calls for it to typically be wired to trigger charging on the DC-to-DC whenever the ignition is on, but instead I used this to install a simple on/off toggle switch.

On days the sun is shining and we've got plenty of daylight travel ahead I turn off the switch and let the solar do all the charging. Like you said, this reduces load on the engine. On cloudy/overcast days or when traveling at night it gets turned on.

There is also a voltage cutoff, so even if I have it turned on the Victron will only charge when the engine is running and producing voltage if I have it set properly.
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Old 10-03-2022, 04:38 PM   #6
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The Victron Orion also can be wired with an on/off trigger. The manual calls for it to typically be wired to trigger charging on the DC-to-DC whenever the ignition is on, but instead I used this to install a simple on/off toggle switch.

On days the sun is shining and we've got plenty of daylight travel ahead I turn off the switch and let the solar do all the charging. Like you said, this reduces load on the engine. On cloudy/overcast days or when traveling at night it gets turned on.

There is also a voltage cutoff, so even if I have it turned on the Victron will only charge when the engine is running and producing voltage if I have it set properly.
At night and cloudy days your running lights probably get turned on? This is why this makes a good trigger. Plus if the switch gets left on the trailer is still connected electrically to the vehicle. I like the convenience of triggering the charger from the cab of the truck.
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Old 10-03-2022, 05:15 PM   #7
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Originally Posted by richard5933 View Post
if you run larger wires from the tow vehicle battery to the rear of the truck and feed the DC-to-DC with this connection, you have the potential to have a much higher amp charge than what your stock 7-pin wiring will ever do. Could be helpful if you're going from campsite to campsite on a rainy day and hope to have full batteries when you arrive.
That would certainly be nice. My truck does have a 2000W generator built in with outlets in the hub, but I can't get my Airstream to charge from it, the converter trips the ground fault protection. I can get around it using a portable power station that is charged from the truck's generator and have that power my trailer. But sure would be nice not to need that middle man.

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Originally Posted by Bill M. View Post
The difference will be no charging without the converter versus charging of somewhere between 5 amps and maybe 50 or so amps depending upon how the converter is wired. Without the DC-DC you pretty much need to disconnect the charge wire on the 7 pin.
Hmm... you and my dealer's head service guy seem to disagree on that point. He claims that my LiFePo batteries are getting charged, just not "the right way" (his words). I have no idea how this works. But you're not the first person to say it won't charge and he's not the first person to say it will. LOL.


Quote:
Originally Posted by richard5933 View Post
The Victron Orion also can be wired with an on/off trigger. The manual calls for it to typically be wired to trigger charging on the DC-to-DC whenever the ignition is on, but instead I used this to install a simple on/off toggle switch.

It would be nice to stick with Victron so that I can tie it in with my MPPT and battery monitors. Assuming I can get bluetooth on the DC to DC as well.
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Old 10-03-2022, 05:23 PM   #8
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At night and cloudy days your running lights probably get turned on? This is why this makes a good trigger. Plus if the switch gets left on the trailer is still connected electrically to the vehicle. I like the convenience of triggering the charger from the cab of the truck.
The Victron will break the connection between the tow vehicle and the trailer when the tow vehicle's voltage is below the set point in order to prevent problems.

Not much of a difference in how we're doing this - I like to have the control on when the system is on and not have it connected to another function. But, I can see the benefit of how you're doing things in that it's one less switch to flip and one less thing to forget.
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Old 10-03-2022, 05:25 PM   #9
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...It would be nice to stick with Victron so that I can tie it in with my MPPT and battery monitors. Assuming I can get bluetooth on the DC to DC as well.
Mine has the Bluetooth connection, and when the DC-to-DC is on I can monitor on my smartphone. Haven't tried it from the driver's seat though, so I can't speak to the range. Typically I check it on when starting the drive and periodically when we stop along the way.
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Old 10-04-2022, 09:58 AM   #10
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It doesn’t Make sense to install lithium’s and not charge them properly. A converter and DC to DC charger will charge them to 100% for very little additional $. Especially if you can install it yourself. One advantage that is important with lithium is you can drain them almost fully without damage and the voltage stays fairly flat. Lead acid should only be drained to half or so and the voltage is more of a curve. Lithium’s do need to see 14.6 volts so the BMS can cell balance. Maintaining 14.6 volts is best.
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Old 10-04-2022, 10:08 AM   #11
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Just spent 5 days without hookups at a sight that would not allow solar recharging due to rain and shade. Did a little test by running the truck fora 1/2 hr. I put back in 5% of my 200 Amh lithiums. I was happy to know I had a decent backup for the unlikely need for emergency power production. I have the Renogy 40 amp Dc Dc
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Old 10-04-2022, 10:24 AM   #12
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Lots of good comments. I have 30 amp Victron DC-DC Charger connected with 4 AWG on both positive and ground side of the TV battery to the rear of the trailer. My thoughts:

1. You will get no charging through the 7 pin. The 10 AWG wire will not carry enough current. Worse is that on some TV, the voltage drop will cause the TV to think the trailer has become disconnected and electric trailer brakes will go offline. See my report on this here.

2. The Victron Charger has blue tooth but the signal is not enough to reach the TV driver seat. The Victron MPPT controller which is installed right next to the DC-DC charger does reach. Go figure.

3. The Victron Charger is not networked with the other Victron equipment so does not show up on the Cerbo GX display. You can see the amperage into the battery but not its source.

4. If you get a DC-DC charger, my experience was to not try to ground through the truck chassis. Run a ground wire to the TV battery as well as the positive wire. The 1.5 V drop put the setpoint to turn off in a place where sometimes the charger would not detect that the engine was no longer running leaving the TV battery charging the trailer batteries and potentially draining the TV battery.

5. When underway, I run the 110V refrigerator instead of on propane. The charger carries that load with no difficulty.
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Old 10-04-2022, 10:39 AM   #13
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It doesn’t Make sense to install lithium’s and not charge them properly. A converter and DC to DC charger will charge them to 100% for very little additional $. Especially if you can install it yourself. One advantage that is important with lithium is you can drain them almost fully without damage and the voltage stays fairly flat. Lead acid should only be drained to half or so and the voltage is more of a curve. Lithium’s do need to see 14.6 volts so the BMS can cell balance. Maintaining 14.6 volts is best.

My understanding is the DC to DC converter will affect only charging via the 7-pin. Or will it affect charging from the 30amp plug as well?
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Old 10-04-2022, 12:03 PM   #14
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(4. If you get a DC-DC charger, my experience was to not try to ground through the truck chassis. Run a ground wire to the TV battery as well as the positive wire. The 1.5 V drop put the setpoint to turn off in a place where sometimes the charger would not detect that the engine was no longer running leaving the TV battery charging the trailer batteries and potentially draining the TV battery.)

I''m curious if you did initially use the chassis ground and then made the change. And exactly how you found that to be a shortcoming. I've wired up mine using #6 on the positive and grabbed a chassis ground point near the back bumper for the negative all going to an Anderson connector. I've yet to have fully checked that part of my upgrade.
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Old 10-04-2022, 01:04 PM   #15
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Just spent 5 days without hookups at a sight that would not allow solar recharging due to rain and shade. Did a little test by running the truck fora 1/2 hr. I put back in 5% of my 200 Amh lithiums. I was happy to know I had a decent backup for the unlikely need for emergency power production. I have the Renogy 40 amp Dc Dc
Well done. In your area does the sun ever come out?
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Old 10-04-2022, 01:09 PM   #16
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(4. If you get a DC-DC charger, my experience was to not try to ground through the truck chassis. Run a ground wire to the TV battery as well as the positive wire. The 1.5 V drop put the setpoint to turn off in a place where sometimes the charger would not detect that the engine was no longer running leaving the TV battery charging the trailer batteries and potentially draining the TV battery.)

I''m curious if you did initially use the chassis ground and then made the change. And exactly how you found that to be a shortcoming. I've wired up mine using #6 on the positive and grabbed a chassis ground point near the back bumper for the negative all going to an Anderson connector. I've yet to have fully checked that part of my upgrade.
The chassis ground is pretty massive. As long as your connection points are really good the drop on the negative is negligible.
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Old 10-04-2022, 01:09 PM   #17
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Just spent 5 days without hookups at a sight that would not allow solar recharging due to rain and shade. Did a little test by running the truck fora 1/2 hr. I put back in 5% of my 200 Amh lithiums. I was happy to know I had a decent backup for the unlikely need for emergency power production. I have the Renogy 40 amp Dc Dc

Wow, I apparently can't go 48 hours without burning through all 200aH of our Lithium Battleborn batteries. And we were pretty conservative with our usage. I don't understand how we went through power that quickly... It was not like that in our old trailer with 200aH of AGMs...
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Old 10-04-2022, 01:18 PM   #18
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The chassis ground is pretty massive. As long as your connection points are really good the drop on the negative is negligible.
Chassis ground problems have a way of sneaking up on you. Seems like a great percentage of electrical issues are traced back to a poor ground, both in the trailer and the tow vehicle.

I ran a pair of 6ga...It was no more work than running a single wire.
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Old 10-04-2022, 01:19 PM   #19
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My understanding is the DC to DC converter will affect only charging via the 7-pin. Or will it affect charging from the 30amp plug as well?
The DC to DC charger only boosts the tow vehicle 12 volt positive to negative lead. It has nothing to do with your 120 volt 30 amp shore power. The converter is the charger on the 120 side.
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Old 10-04-2022, 01:27 PM   #20
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The DC to DC charger only boosts the tow vehicle 12 volt positive to negative lead. It has nothing to do with your 120 volt 30 amp shore power. The converter is the charger on the 120 side.

Yeah, that's what I thought. The way you were talking, it just made it seem like I could never charge my batteries up without it, lol. But since I have three other ways they charge (solar on the roof and portable panels, direct to a wall, or to a battery pack that is being charged by my truck's built in generator), I'm trying to see if improving the charging from the truck while towing is significant enough to make it worth it. the vast majority of our trips are single destination. We are not driving it around a lot between sites. Though if the DC to DC makes it so that charging from the 7-pin is as effective as charging from the generator in our truck, then it could be worth it, so I don't need to middle man powerstation between the truck generator and the AS (due to ground fault issues on the truck generator).
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