Can I put the DC/DC charger in my truck instead?

[jeffmc306]

Originally Posted by Life is a Highway

Love ya Jeff! But I get fixated on that upside down mount. Lol

There, fixed it for ya

[Mr Wonderful]

Originally Posted by jeffmc306

Mr Wonderful, I can share where I put my DC-DC charger in our 27’ GT FBT. I have a Renogy 40A unit and put it under the curb side bed, just above the DC junction box.

I’ve got a Battle Born GC3 inside the street side compartment extending into the front compartment. I did run a pair of 4 AWG cables under the truck to the bumper and used Anderson 150A connectors to the trailer.

I think you’re right about the distance being close to the same if you installed the DC-DC charger in the truck bed vs. inside the trailer. That said, inside the trailer the charger is protected and not that hard to get to.

By the way, the DC-DC charger worked great and allowed us to run the 3-way fridge on 12V instead of propane when on the road. Well worth the effort!

Hope that helps!
-Jeff

Thanks for the pic Jeff. I'm sure I'll end up in a similar location.

Mike

[uncle_bob]

Originally Posted by Mr Wonderful

Haha yes, it’s only $$$. I will likely find a place on the trailer.

Some additional info. I have a 2021 Globetrotter. 2 100a batteries in the battery box. The thought was to but the DC/DC converter right inside the tailgate mounted on the side. I’m not envisioning to much of difference in cable length (maybe a few feet)

Anyway, I appreciate the feedback. Will likely find a spot on the AS in the storage area up front.

Thank all!

Hi

Assuming you do this with the existing harness, you still have the length of the 7 pin cable and then the wiring from the junction point back to the batteries.

You will find that there is a lot of this and that involved in this project. You have to get to a lot of places in the trailer. It very much is not just a "swap the batteries and you are done" sort of thing. Various unusual tools are involved as well.

All of that is on top of the "learn how to do this" part of it. Lots of reasons to let a pro do the work if you have concerns.

Bob

[rickst29]

Originally Posted by Mr Wonderful

I've not seen much discussion on putting the DC/DC charger within the truck vs the trailer. Any reason this would not work or is a bad idea?
. . .

Mike

The DC-to-DC chargers need to monitor the Trailer Battery charging bus voltage, in order to avoid overcharging the "target batteries", and also to present an adequate voltage at their terminals.


In the case of LiFePO4 batteries, the BMS units within the the battery packs is also capable of preventing input charging current (and power) when the battery cells are already full.


But installation of the DC->DC converter/charger unit within the truck, using the normal "Trailer Battery Charge" wiring path to reach the batteries with a somewhat boosted level of voltage, will leave the unit unable to judge the voltage drop while high current is running "downstream", into the batteries).


A the battery terminals,. the resulting voltage becomes reduced by variable amounts, and might not be effective for charging - or might left to high, if you fudge the paramter to "make up" for wiring voltage drops.


Properly installed, the voltage drop between the unit and the battery terminals is low. You could do a lot of crazy wiring upgrades to improve gthe TBC wire path, but the boosting charger/converter units were mostly invented top avoid doing that.

[2008RN]

Originally Posted by ITSNO60

Victron says to locate it as close to the battery bank being charged as possible, allowing for ventilation, protection from the elements and not on top of any batteries. Voltage drop due to wire resistance might play a role here resulting in the batteries not receiving a high enough voltage to top off.

I look forward to comments from others on this.

I agree, The voltage drop from the cab/engine compartment of the tow vehicle to the trailer batteries would most likely be low enough to improperly charge the trailer batteries. The DC to DC converter mounted close to the trailer batteries can use a lower voltage and increase the voltage to properly charge whatever type of battery is in the trailer. I am laying the ground work to install 2 30amp DC to DC converter close to my Battery bank in the trailer.



I have seen one person that mounted a 30 amp converter in the trailer and another in the truck bed side wall to charge an extra mobile battery to run a 12v cooler in the truck bed.

[kmclaren]

I have an Orion smart DC-DC in the engine compartment of my F150. I used a powerpost high amp cable and the connection is under the rear bumper. Since you can monitor the performance through the Victron app. on your phone I have not noticed any drop-off in amps. In other words it works as it should. Install it where it makes the most sense for your set-up.

[ITSNO60]

Originally Posted by kmclaren

I have an Orion smart DC-DC in the engine compartment of my F150. I used a powerpost high amp cable and the connection is under the rear bumper. Since you can monitor the performance through the Victron app. on your phone I have not noticed any drop-off in amps. In other words it works as it should. Install it where it makes the most sense for your set-up.

So what is your voltage at the LiFePo4 terminals at or near the end of the charge? When you say you have not noticed any drop off of amps, what exactly do you mean? There should be a substantial drop off of amps (current) near the end of the cycle, and a rise in voltage, in order to completely charge and balance a LiFePO4.
This is not so critical if you have other ways to top off the LiFePO4, everyone should have at least one way to completely top off and balance occasionally.

[pboomerx]

Originally Posted by Mr Wonderful

I've not seen much discussion on putting the DC/DC charger within the truck vs the trailer. Any reason this would not work or is a bad idea?

I'm old and not a contortionist, which seems to be the pre-requisite for electronic upgrades in Airstream trailers. Like things simple and easy to get too. I have a cab on top of the truck and thinking of mounting it somewhere inside and running a pig tail to the bumper side that can mate with the AS.

This would also allow me to charge something besides my AS. I don't have a need as of yet, but gives me the option.

Mike

Hi

Figured I would share my rationale and solution.
I have a 2021 AS 30’ Classic with two Battleborn batteries in the battery box. Each are 100ah and capable of significant charge and discharge rates. I have a 2021 GMC 2500 HD as my TV. I don’t have a cap over the truck bed.

My goal is to arrive at camp after a 3-4 hour drive with full to near full batteries. No way a 7 pin connector would be able to do that. Decided to put a Redarc 40A dc to dc converter in the battery box. The reason for 40A is that I could use 6 gauge wire to the truck battery instead of 4 gauge, which was hard enough to route. The Redarc unit is waterproof and they have awesome customer service. The reason for the battery box location is that the Redarc unit also has MPPT solar controller to handle all the ground mount solar. All connectors are Anderson.

Won’t go into all the rationale for a dc to dc converter. Assuming you know all that stuff.

Good luck

[kmclaren]

Originally Posted by ITSNO60

So what is your voltage at the LiFePo4 terminals at or near the end of the charge? When you say you have not noticed any drop off of amps, what exactly do you mean? There should be a substantial drop off of amps (current) near the end of the cycle, and a rise in voltage, in order to completely charge and balance a LiFePO4.
This is not so critical if you have other ways to top off the LiFePO4, everyone should have at least one way to completely top off and balance occasionally.

I have not measured the drop-off. But discussing with Victron the estimate over 19 feet is <3%. Also when using volatge drop calculators on-line, it appears it could be less. At some point I will measure, but it works for me so I am not concerned. I also have 200w of solar on the roof. I have a Sport 22FB and space is extremely limited to cram the batteries, controller and inverter close by. The priority was to have the inverter close to the battery bank.

[Mr Wonderful]

Hi all OP here. Just a quick update. I have the Globetrotter in for service to replace the POS WFCO auto sensing converter. The plan is to have them install a DC/DC converter on the trailer side as well.

I really appreciate the feedback. I’ve never had 2 pages of responses before.


Mike

[uncle_bob]

Originally Posted by pboomerx

Hi

Figured I would share my rationale and solution.
I have a 2021 AS 30’ Classic with two Battleborn batteries in the battery box. Each are 100ah and capable of significant charge and discharge rates. I have a 2021 GMC 2500 HD as my TV. I don’t have a cap over the truck bed.

My goal is to arrive at camp after a 3-4 hour drive with full to near full batteries. No way a 7 pin connector would be able to do that. Decided to put a Redarc 40A dc to dc converter in the battery box. The reason for 40A is that I could use 6 gauge wire to the truck battery instead of 4 gauge, which was hard enough to route. The Redarc unit is waterproof and they have awesome customer service. The reason for the battery box location is that the Redarc unit also has MPPT solar controller to handle all the ground mount solar. All connectors are Anderson.

Won’t go into all the rationale for a dc to dc converter. Assuming you know all that stuff.

Good luck

Hi

If the expectation is to push 50 to 60A towards the batteries (to be putting in 40A after losses) for 3 to 4 hours, you probably should consider a second alternator on the truck. Most modern vehicles don't have that sort of "spare current" available. The "2 minutes at 10,000 RPM" rating on the alternator isn't what you want to go by

Bob

[pboomerx]

Originally Posted by uncle_bob

Hi

If the expectation is to push 50 to 60A towards the batteries (to be putting in 40A after losses) for 3 to 4 hours, you probably should consider a second alternator on the truck. Most modern vehicles don't have that sort of "spare current" available. The "2 minutes at 10,000 RPM" rating on the alternator isn't what you want to go by

Bob

.0

Excellent point. In my case, my 2500 HD has two alternators (factory) rated for around 400A

[uncle_bob]

Originally Posted by pboomerx

.0

Excellent point. In my case, my 2500 HD has two alternators (factory) rated for around 400A

Hi

If you do a bit of digging on the forum, you can find threads about folks frying their 350A alternators with a 40A added load. Turns out that magic amps number is not quite what you might think it is ....

Bob

[pboomerx]

Originally Posted by uncle_bob

Hi

If you do a bit of digging on the forum, you can find threads about folks frying their 350A alternators with a 40A added load. Turns out that magic amps number is not quite what you might think it is ....

Bob

After 10k miles I am calling it good