Do I NEED a DC-DC Charger?

[BillandLisa]

I have a 2023 Reflection 367BHS that came with 370W solar panel and a 50 Mppt solar charger. I also added a 2000W inverter to the unit.

I have replaced my lead acid battery with 2 100Ah LifePO4 batteries (parallel) and upgraded the stock converter to a Lithium capable charger.

I understand that with the stock set up my tow vehicle umbilical will only be able to charge my Li-ion batteries to 80% capacity but I can end up getting up to 100% from the solar charger.

Getting ready to take a 8hr trip down the road and I am worried based on an article (off the internet of course) that I could potentially damage the alternator / wiring on my tow vehicle if the trailer battery starts pushing current to the tow vehicle battery.

I understand that a DC-DC charger would prevent that from happening but I am still paying off the other upgrades and would like to not have to add the DC-DC charger.

I know if I want to be absolutely sure that it will not cause a problem I can pull the fuse in the TV that provides power to the power pin on the umbilical.

Am I being overly cautious? With only 370W of solar do I have to worry about overloading the wires in the TV is voltage in the trailer goes higher than the TV Voltage?

Thanks in advance for your insights and recommendations.

Bill

 

[Soundsailor]

In my opinion, you do not need a DC-to-DC charger. While I've heard that damage the alternator claim before, it's never happened to me. You have plenty of battery and solar to handle an 8-hour trip.

 

[BillandLisa]

thank you - Always nice to have your opinion confirmed

 

[JKellerJr]

I have a 2023 Reflection 367BHS that came with 370W solar panel and a 50 Mppt solar charger. I also added a 2000W inverter to the unit.

I have replaced my lead acid battery with 2 100Ah LifePO4 batteries (parallel) and upgraded the stock converter to a Lithium capable charger.

I understand that with the stock set up my tow vehicle umbilical will only be able to charge my Li-ion batteries to 80% capacity but I can end up getting up to 100% from the solar charger.

Your tow vehicle will charge to 100% it will just take a long time. My old truck pushed about 7amps per hour, looks like my new ‘24 gmc pushed about 10amps

Getting ready to take a 8hr trip down the road and I am worried based on an article (off the internet of course) that I could potentially damage the alternator / wiring on my tow vehicle if the trailer battery starts pushing current to the tow vehicle battery.

It will not damage your alternator or wiring using the stock system. Only if you bypass the stock system and tie directly to you alternator and the batteries are low. It will run at max output for as long as it takes to get to full charge and alternators are not designed to run at full output for extended periods. Keeping it stock it will only push what the truck is set up for. (7-10amps normally) that won’t hurt anything

I understand that a DC-DC charger would prevent that from happening but I am still paying off the other upgrades and would like to not have to add the DC-DC charger.

The reason for a dc-dc charger is to use the tow vehicle as a legit charging source. Looks like that it unnecessary for your set up.

I know if I want to be absolutely sure that it will not cause a problem I can pull the fuse in the TV that provides power to the power pin on the umbilical.

Am I being overly cautious? With only 370W of solar do I have to worry about overloading the wires in the TV is voltage in the trailer goes higher than the TV Voltage?

Thanks in advance for your insights and recommendations.

Bill

 

[COGrandDes]

In my opinion, you do not need a DC-to-DC charger. While I've heard that damage the alternator claim before, it's never happened to me. You have plenty of battery and solar to handle an 8-hour trip.

Totally agree with Soundsailor. I have 560 aH of LiP04 batteries that I trickle charge with my new truck's alternator through the 7-pin camper pigtail and I have solar as well. Solar does all the work really. I just don't see the need for myself to ever have a DC-DC charger...at least here in CO where the sun shines most of the time. I've run this camper and my last camper this way for year without issue.

 

[Toy Haulen]

I have a 2023 Reflection 367BHS that came with 370W solar panel and a 50 Mppt solar charger. I also added a 2000W inverter to the unit.

I have replaced my lead acid battery with 2 100Ah LifePO4 batteries (parallel) and upgraded the stock converter to a Lithium capable charger.

I understand that with the stock set up my tow vehicle umbilical will only be able to charge my Li-ion batteries to 80% capacity but I can end up getting up to 100% from the solar charger.

Getting ready to take a 8hr trip down the road and I am worried based on an article (off the internet of course) that I could potentially damage the alternator / wiring on my tow vehicle if the trailer battery starts pushing current to the tow vehicle battery.

I understand that a DC-DC charger would prevent that from happening but I am still paying off the other upgrades and would like to not have to add the DC-DC charger.

I know if I want to be absolutely sure that it will not cause a problem I can pull the fuse in the TV that provides power to the power pin on the umbilical.

Am I being overly cautious? With only 370W of solar do I have to worry about overloading the wires in the TV is voltage in the trailer goes higher than the TV Voltage?

Thanks in advance for your insights and recommendations.

Bill

Which converter did you purchase? I did this modification last year but have been holding off on my Amazon order for the latest firmware on the WFCO WF-8955-AD-MBA converter. This summer we only have state park reservations with electric hookups so it won't be any issue until late fall for us. Thanks!

 

[BillandLisa]

Thank you for your very complete and thorough answer! It doesn't hurt that this is exactly what I wanted to hear!

 

[BillandLisa]

Here is the link but it looks like it is not available any longer.

https://www.amazon.com/gp/product/B07DP3X16F/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

 

[BoredWeasel]

Here is what is happening.

The 7 pin wiring harness with the smallist diameter wire acts like a resistor and protects the alternator.

The issue no one here is mentioning is the excess voltage feeding back into the truck and causing issues. You have 370 watts of solar charging your lithuim battery in the trailer to 14.6-15 volts, depending on your setup, your truck will not like that. It has caused an issue with all of the domestic truck manufactures. GM has an open recall to replace the brake controller module . Ram and ford have not redesigned or issued and updated part to my knowledge. Folks are seeing over voltage messages and brake conntroler disconnect messages while towing.

The DC to DC isolates the power systems from each other, as well as, limiting charge current to the battery.

A work around to prevent the over charging is to turn off your solar panels when towing. If you install the dc to dc charger make sure to disable the charge circuit in the 7 pin connector

 

[COGrandDes]

Here is what is happening.

The 7 pin wiring harness with the smallist diameter wire acts like a resistor and protects the alternator.

The issue no one here is mentioning is the excess voltage feeding back into the truck and causing issues. You have 370 watts of solar charging your lithuim battery in the trailer to 14.6-15 volts, depending on your setup, your truck will not like that. It has caused an issue with all of the domestic truck manufactures. GM has an open recall to replace the brake controller module . Ram and ford have not redesigned or issued and updated part to my knowledge. Folks are seeing over voltage messages and brake conntroler disconnect messages while towing.

The DC to DC isolates the power systems from each other, as well as, limiting charge current to the battery.

A work around to prevent the over charging is to turn off your solar panels when towing. If you install the dc to dc charger make sure to disable the charge circuit in the 7 pin connector

I have a 2022 GMC Sierra 3500 Duramax truck and use the factory 7 pin connector in the bed for my camper without issue. I never turn off my solar panels when driving or being plugged into my truck. My truck was two years old last March and I've had no issues with warning lights, brake controllers, or voltage issues with the truck or camper. I also have nearly 600 watts of solar that are constantly charging with my Victron solar controller. I've evaluated these posts about the DC-DC charger numerous times and still can't justify the need.

 

[triplethreat]

Here is what is happening.

The 7 pin wiring harness with the smallist diameter wire acts like a resistor and protects the alternator.

The issue no one here is mentioning is the excess voltage feeding back into the truck and causing issues. You have 370 watts of solar charging your lithuim battery in the trailer to 14.6-15 volts, depending on your setup, your truck will not like that. It has caused an issue with all of the domestic truck manufactures. GM has an open recall to replace the brake controller module . Ram and ford have not redesigned or issued and updated part to my knowledge. Folks are seeing over voltage messages and brake conntroler disconnect messages while towing.

The DC to DC isolates the power systems from each other, as well as, limiting charge current to the battery.

A work around to prevent the over charging is to turn off your solar panels when towing. If you install the dc to dc charger make sure to disable the charge circuit in the 7 pin connector

Why would anyone EVERY have a higher voltage than 14.6V being applied to the LFP battery? 14.6V is the maximum that they should ever see (3.65V per cell) and most BMS protection units will cut off anything over that. To me, the solar controller settings should be tweaked to prevent anything over the 14.6 number.
Disclaimer: I don't have solar anything, but I do have some LFP battery knowledge....which is well known to have a 14.6V max for a 4 cell battery.

 

[Scott'n'Wendy]

Here is what is happening.

The 7 pin wiring harness with the smallist diameter wire acts like a resistor and protects the alternator.

The issue no one here is mentioning is the excess voltage feeding back into the truck and causing issues. You have 370 watts of solar charging your lithuim battery in the trailer to 14.6-15 volts, depending on your setup, your truck will not like that. It has caused an issue with all of the domestic truck manufactures.

That would be true if your solar charge controller is set incorrectly? If you are hitting ANY type 12vdc battery with over 14.6 volts...you will kill it eventually.

Edit...Xrated beat me to it.

 

[BoredWeasel]

I have a 2022 GMC Sierra 3500 Duramax truck and use the factory 7 pin connector in the bed for my camper without issue. I never turn off my solar panels when driving or being plugged into my truck. My truck was two years old last March and I've had no issues with warning lights, brake controllers, or voltage issues with the truck or camper. I also have nearly 600 watts of solar that are constantly charging with my Victron solar controller. I've evaluated these posts about the DC-DC charger numerous times and still can't justify the need.

Every situation is unique.

I also have a 2022 Sierra and have had zero issues.

It is about providing all the relevant information so the reading can either take it at face value, or do more research on their own.

 

[BoredWeasel]

Why would anyone EVERY have a higher voltage than 14.6V being applied to the LFP battery? 14.6V is the maximum that they should ever see (3.65V per cell) and most BMS protection units will cut off anything over that. To me, the solar controller settings should be tweaked to prevent anything over the 14.6 number.
Disclaimer: I don't have solar anything, but I do have some LFP battery knowledge....which is well known to have a 14.6V max for a 4 cell battery.

Yep, battleborn recommends 14.6 volts, ran into a fellow charging at 15 volts in a boondocking spot in florida, with the currents and level of solar he was running his charge controller was at 15 volts and the voltage at the battery was 14.2-15 volts depending on current from the solar array. Yes, he was having problems.

my point is it happens and we shouldn't discount what we "know" with what is seen in the wild.

 

[triplethreat]

Yep, battleborn recommends 14.6 volts, ran into a fellow charging at 15 volts in a boondocking spot in florida, with the currents and level of solar he was running his charge controller was at 15 volts and the voltage at the battery was 14.2-15 volts depending on current from the solar array. Yes, he was having problems.

my point is it happens and we shouldn't discount what we "know" with what is seen in the wild.

It's not just Battleborn, any, all, every manufacturer of LFP batteries will tell you, 14.6V is the max number for that type of battery. And yes, I agree...there are people out there that are doing it wrong and it will cause issues, but I wanted to make sure and point out the "correct" numbers that are not variable for the top/max voltage that is safe. And personally, I don't even go that high with my voltage....mine is set at 14.2V and even though it might take a bit longer to get to 100% SOC vs. 14.6V, it's also less stress on the cells over the long haul.

 

[BillandLisa]

Here is what is happening.

The 7 pin wiring harness with the smallist diameter wire acts like a resistor and protects the alternator.

The issue no one here is mentioning is the excess voltage feeding back into the truck and causing issues. You have 370 watts of solar charging your lithuim battery in the trailer to 14.6-15 volts, depending on your setup, your truck will not like that. It has caused an issue with all of the domestic truck manufactures. GM has an open recall to replace the brake controller module . Ram and ford have not redesigned or issued and updated part to my knowledge. Folks are seeing over voltage messages and brake conntroler disconnect messages while towing.

The DC to DC isolates the power systems from each other, as well as, limiting charge current to the battery.

A work around to prevent the over charging is to turn off your solar panels when towing. If you install the dc to dc charger make sure to disable the charge circuit in the 7 pin connector

Given that the solar panels produce more power than the alternator and can take the Li ion batters to full charge it seems to me a better work around would be to pull the fuse to disable the charging circuit in the 7 pin connector. Would this prevent the truck from seeing the over voltage condition you warned against or would the higher voltage still make it to the truck via the brake controller wires? I definitely don't want to damage the truck so if I have to disconnect the solar and let the truck charge the batteries to ~80% and charge the rest of the way up at my destination.

 

[BillandLisa]

I have a 2022 GMC Sierra 3500 Duramax truck and use the factory 7 pin connector in the bed for my camper without issue. I never turn off my solar panels when driving or being plugged into my truck. My truck was two years old last March and I've had no issues with warning lights, brake controllers, or voltage issues with the truck or camper. I also have nearly 600 watts of solar that are constantly charging with my Victron solar controller. I've evaluated these posts about the DC-DC charger numerous times and still can't justify the need.

My TV is a 2020 GMC 2500 Denali Duramax. One issue/feature/quirk I have noticed is when the rv is parked but still connected to the TV (i.e. loading up for a trip in front of the house), I will get a periodic "Flash" of the trailer break lights, the duration of which is so short it does not illuminate the LED bulbs fully before it disappears. I "address" the issue by unplugging the 7 pin cord but I honestly do not know what causes the flash or if it represents an issue or can be left alone
.

 

[COGrandDes]

Given that the solar panels produce more power than the alternator and can take the Li ion batters to full charge it seems to me a better work around would be to pull the fuse to disable the charging circuit in the 7 pin connector. Would this prevent the truck from seeing the over voltage condition you warned against or would the higher voltage still make it to the truck via the brake controller wires? I definitely don't want to damage the truck so if I have to disconnect the solar and let the truck charge the batteries to ~80% and charge the rest of the way up at my destination.

I believe I've read that some using the DC-DC chargers are using the 7-pin charging wire to trigger the operation of the charger. There are always ten ways to do things if there's a will! For me.....I still don't see the need so I am not the expert on the DC-DC chargers.....

 

[COGrandDes]

My TV is a 2020 GMC 2500 Denali Duramax. One issue/feature/quirk I have noticed is when the rv is parked but still connected to the TV (i.e. loading up for a trip in front of the house), I will get a periodic "Flash" of the trailer break lights, the duration of which is so short it does not illuminate the LED bulbs fully before it disappears. I "address" the issue by unplugging the 7 pin cord but I honestly do not know what causes the flash or if it represents an issue or can be left alone
.

That's not a quirk but a designed in feature with the GMs....

When a trailer is connected and the vehicle is off, the Trailering App System will
periodically pulse the lighting circuits of the trailer to verify it is still connected. The trailer lights may periodically flash as a result of this trailer connection detection. These flashes may be more visible in dark ambient light environments. The flashing or flickering lights are a normal condition and the Trailering App System has built-in
protections to prevent the battery from draining.

 

[triplethreat]

Given that the solar panels produce more power than the alternator and can take the Li ion batters to full charge it seems to me a better work around would be to pull the fuse to disable the charging circuit in the 7 pin connector. Would this prevent the truck from seeing the over voltage condition you warned against or would the higher voltage still make it to the truck via the brake controller wires? I definitely don't want to damage the truck so if I have to disconnect the solar and let the truck charge the batteries to ~80% and charge the rest of the way up at my destination.

Just remember this......the solar output is controlled by the Solar Controller and that should never be set to give the batteries more than 14.6V for LiFePO batteries. If it does, the solar controller settings need to be changed to stop that from happening. If not....AND the BMS in the battery is not taking the battery off line for high voltage, you run the risk of cell damage in the battery.