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Is Renogy DC-DC with MPPT not designed for travel trailers?

sunrise

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I was pretty excited after watching Will's video on Renogy's DC-DC charger with MPPT. It solves the last issue I had with my trailer solar setup - charging trailer battery with TV starting battery/alternator, and provide isolation. That's until I read the wire sizing requirement.
Unlike van converted RVs, trailer trailer uses 7-way connector to hook up to TV, most common gauge of the power/ground wire in a 7-way cable is 10-12 gauge I believe, if a Renogy DCC30S (30A model) draws full 30A, even for the 10awg cable it's likely it will trip the fuse on TV, when my LiFePo4 battery is at low SOC, which will can draw as much current the 30A charger can provide. For 12awg cable it's a fire hazzard. I am not even talking about the 50A model.

Does this mean this product isn't designed for travel trailers? or are there any settings that can be tweaked to limit the DC amp draw?
Thanks!
 
I don't think the unit is designed for any specific RV type, it's designed to provide charging. So you have to decide how many amps of charging you require. How long will you typically be towing the trailer and how much battery capacity are you trying to recharge? The unit does have settings to lower the charge current, but many people find they need more than a 12 awg cable can provide. So they typically wire the TV and trailer with heavier gauge wire that does not pass through the 7 way connector.
 
I don't regard my truck as a charging source for my 5th wheel. That's covered by solar/shore power.
In fact, pretty soon I'm separating out the 12v battery system entirely and setting it up with a small SLA for the break away brake system.
The hitch connection is only really good for maybe 10a typically. If you want more, you should run a dedicated charging line, slap an anderson connector down there and feed it all the amps you want. (don't forget to fuse it at the battery.)
 
@dvspl , @willo sorry that I wasn't clear - I do not want anything over 20A from my tow vehicle, my concern was the DC/DC charge + LiFePo4 battery would draw too much current (> 30A) that would overload the towing vehicle. I have no intention to run heavy gauge wire from TV to trailer, as I only need ~10A to prevent fridge to drain the battery to the point the breakaway brake would not work - my solar should cover 99% of the time. so this is more or less a safety measure. Good to know the unit can limit charging current.
Right now I am leaning towards a Victron 20A SCC ($160) + Victron DC/DC Orion Tr converter($65). This combo does everything I need and with great software/app support. It's cheaper than DCC30S + BT2 ($270) and has more reliable bluebooth support.

Thank you both!
 
A DC-DC charger is, by its nature, going to limit how many amps it tries to pull from the source. This is true of any DC-DC charger, not just Renogy. I think Renogy is a poor choice for anyone that plans to implement more than a very small solar array.

The Victron pair you're leaning towards is an excellent choice. Make sure you get the smart Tr version, which can be programmed.

Over on the Ford-Trucks forum a guy did a test to see how many amps he could really pull through the 7-pin connection. The circuit on his truck is rated for 30 amps. The alternators are rated to 397 amps. Reality was that the circuit maxxed out around 20 amps.
 
@HRTKD Thank you for this information, but I am actually more confused now, are you saying with a rated 50A DC/DC charger/converter, a low SOC lithium hungry for amps and a alternator rated > 300A, the converter maxed out ~20a? What was limiting the current? It can't be the DCDC converter otherwise they'd get sued for fraud right?

I am actually going to get the 'dumb' version of Orion Tr, for cost and space saving. I will set the constant(no stage) output voltage to 13.4v. With 200ah Lithium battery and 240w solar for a small 16' trailer, I only need it for unanticipated situation - when I had to drive in the rain or during night - I just don't want the fridge drain out the battery so much so that the it doesn't have enough juice for breakaway brake. I assume 13.4 would charge a low SOC battery fast enough and would not damage a fully charged battery (when I drive to camp ground with a fully charged battery)

Is this plan flawed? the smart version cost about $200 more, I just feel it's not worth it for what I need it for.
 
On modern Ford F-series trucks the 7-pin connection is limited to 30 amps - at least the Superduty trucks are, I'm not sure about the 1/2 ton trucks. The real world test was done on an F-350 with an alternator system of 397 amps. It doesn't matter how powerful the alternator system is on these trucks. The 7-pin connection is simply limited to 30 amps. But the test showed that on that truck that the max amps that the trailer would see is 20 amps. It doesn't matter if it was LiFePO4 or lead acid. 20 amps max.

In that particular owner's case, 20 amps wasn't good enough. The only way to get more amps to the trailer was to bypass the 7-pin cable. So he ran a dedicated cable from the engine compartment all the way to the rear bumper where there was a connector. The trailer had a matched connector and cable that then went to a DC-DC charger. That dedicated cable had no 30 amp limit. In theory, it could have handled at least 100 amps. But the owner didn't want to pull that many amps, so he put in a DC-DC charger to limit how many amps were coming from the tow vehicle. The DC-DC charger will use only as many amps as it is rated for.

In your case, I don't know what vehicle you're using or what its 7-pin connection is capable of. The first clue on this would be the power fuse that goes to the 7-pin cable. Look it up and that would be your upper limit.

To answer your question, I think you'll be fine as long as the rating of the Orion is no more than your 7-pin cable is rated for. To be on the safe side, I would get an Orion that is rated for less then your 7-pin rating.
 
On modern Ford F-series trucks the 7-pin connection is limited to 30 amps - at least the Superduty trucks are, I'm not sure about the 1/2 ton trucks. The real world test was done on an F-350 with an alternator system of 397 amps. It doesn't matter how powerful the alternator system is on these trucks. The 7-pin connection is simply limited to 30 amps. But the test showed that on that truck that the max amps that the trailer would see is 20 amps. It doesn't matter if it was LiFePO4 or lead acid. 20 amps max.

In that particular owner's case, 20 amps wasn't good enough. The only way to get more amps to the trailer was to bypass the 7-pin cable. So he ran a dedicated cable from the engine compartment all the way to the rear bumper where there was a connector. The trailer had a matched connector and cable that then went to a DC-DC charger. That dedicated cable had no 30 amp limit. In theory, it could have handled at least 100 amps. But the owner didn't want to pull that many amps, so he put in a DC-DC charger to limit how many amps were coming from the tow vehicle. The DC-DC charger will use only as many amps as it is rated for.

In your case, I don't know what vehicle you're using or what its 7-pin connection is capable of. The first clue on this would be the power fuse that goes to the 7-pin cable. Look it up and that would be your upper limit.

To answer your question, I think you'll be fine as long as the rating of the Orion is no more than your 7-pin cable is rated for. To be on the safe side, I would get an Orion that is rated for less then your 7-pin rating.
Thanks, that make sense. maybe on that truck, between alternator and the 7way connection there is current limiting circuit.
My fuse for that is rated 30A. I plan to get the 10A DC/DC converter with adjustable output. They are very reasonably priced at $64.
 
@HRTKD Thank you for this information, but I am actually more confused now, are you saying with a rated 50A DC/DC charger/converter, a low SOC lithium hungry for amps and a alternator rated > 300A, the converter maxed out ~20a? What was limiting the current? It can't be the DCDC converter otherwise they'd get sued for fraud right?

I am actually going to get the 'dumb' version of Orion Tr, for cost and space saving. I will set the constant(no stage) output voltage to 13.4v. With 200ah Lithium battery and 240w solar for a small 16' trailer, I only need it for unanticipated situation - when I had to drive in the rain or during night - I just don't want the fridge drain out the battery so much so that the it doesn't have enough juice for breakaway brake. I assume 13.4 would charge a low SOC battery fast enough and would not damage a fully charged battery (when I drive to camp ground with a fully charged battery)

Is this plan flawed? the smart version cost about $200 more, I just feel it's not worth it for what I need it for.
i don't think 13.4V will charge an LFP battery effectively - max SOC would be ~60-70% if that
13.4V is on the short sharp charging knee, would need at least 13.6V to get on top of the curve
if SOC was below 60%, the battery would take maximum current from the source, as it would all the way up to 90%, so not sure what fast enough would be
 
i don't think 13.4V will charge an LFP battery effectively - max SOC would be ~60-70% if that
13.4V is on the short sharp charging knee, would need at least 13.6V to get on top of the curve
if SOC was below 60%, the battery would take maximum current from the source, as it would all the way up to 90%, so not sure what fast enough would be
@mkaye - In this case I opt for battery life instead of maximize charging speed, otherwise I would buy a 30A dc dc charger instead of a 10A one. I just want to keep the fridge running and have enough juice so in case of emergency the breakaway brake still functional.
 
Hi
I am new here but follow this interested.

Just in planning to have a boost charger and a solar panel on my trailer.
Wondering if I can use the Renogy DC DC MPPT for both? via the 7 pin plug or a new own dedicated wire?

I am a little confused at th moment.....
 
Do you know if the Renogy Isolates DC negative from one side to the other?
(I don't know for sure but I don't think it is isolated).

Be aware that a non-isolated DC-DC charger will effectively bond the truck DC negative to the house battery DC negative.

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This is not necessarily bad but in that case you don't want to bond the house battery to the trailer chassis or it will create ground loops through the ground in the 7 Pin connector. However, when the trailer is not hitched to the truck, your DC circuit is not bonded to chassis.

There is a version of the Victron Smart Orion that is isolated. I like that version for trailers because it gives you options on whether, where and how to bond DC Negative to ground.....Unfortunatly, it is a lot more expensive.
 
Scamp 13, rav4 six cylinder TV, Renogy 30 amp mmpt dc-dc, I disabled charge circuit on 7 pin, #6 cable from TV battery to connector at hitch, to renogy...
100 amp hr AGM house battery depleted to approx 50% soc, initial charge rate 26 amps, tapered to 10 amps after 1 hr. Seems like it’s doing what it’s advertised to do?
House system all grounds to trailer frame, which is grounded to cars frame...through another #6 cable.
Anything I’m missing? Don’t understand the “bonding” issue?
 
I have a little more room because it's a travel trailer... BUT.. for compartmentalizing I chose a 2000W inverter generator (closer to 1500w on propane) and a Aims 75 amp variable converter. The generator can stand alone as a power source, the Converter can stand alone to chg off the generator or shore power. and one of the two paralleled 280ah batteries can be used as a trolling motor battery when we are not traveling.
 
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