48 replies to this topic

[Jsoboti]

Trying to work smarter not harder...

 

Picking up a new Hawk in December to be put on my 2014 F-350. Specced with a single 79Ah AGM battery and "pre-wired" for solar (no charge controller installed). I plan on adding a second 79Ah battery right away and eventually solar. 

 

I'll be doing a lot of winter camping and I think I would like to install a DC-DC charger. (more amps= less truck idling time to top off batteries if needed??). I don't know if the 2014 F350 has a "smart alternator" or not. 

 

My real question is... should I ask the installer, Mule Expedition Outfitters, to install 4AWG wiring on initial install instead of the smaller diameter normal wiring harness. So that I don't have double efforts in a month or so when I want to install the DC-DC charger and presumably need heavier gauge wire? If I don't install a DC-DC charger, will having 4AWG wiring from truck to camper increase the amps I see come across while driving anyway, perhaps receiving me of the necessity of the DC-DC charger? 

[rando]

If you are installing a DC-DC charger, you don't need larger wiring.  The DC-DC charger will boost the voltage, offsetting the voltage drop on the skinnier wiring.   

 

With heavier gauge wiring you may not need the DC-DC, but have you priced a DC-DC vs ~50' of 4AWG wire?  The DC-DC converter is not much more.....

[Jon R]

Call Mitch or the shop at Mule Outfitters and I'm sure they can tell you what they are willing to do on installation.  I suspect they'll do whatever you want but may need to charge extra for the heavier wire or extra labor.  I know from having asked that FWC at the factory isn't doing any changes beyond the offered configurations. 

 

I assume the reason for the DC-DC charger is to raise the voltage delivered to the camper battery and allow a high level of current to be delivered even though the truck's "smart" alternator and the wiring to the camper are causing insufficient voltage at the camper battery for charging.  If you have that situation, increasing the wire size may help some by reducing the loss in the wire but I suspect it won't be sufficient to compensate for the low alternator voltage.  Maybe others have actual experience with this. 

 

From what I've read all new trucks are being delivered with smart alternators as of a few years ago.  I don't see why FWC still delivers a camper charging system that doesn't work effectively with the new trucks.  The installer can put in a relay that hard switches the charging connection on when the truck is running rather than using an isolator, but that doesn't solve the inadequate alternator voltage problem.  FWC's production has been high so maybe they are planning a change but haven't had time to develop and implement it.  I'm crossing my fingers hoping FWC addresses that issue (and offers a lithium battery option) before my camper gets built in late Spring 2021.  Otherwise I'll have to do a lot of modification to get the capability I want.  I don't mind doing the work but I hate paying for wiring and components I just have to take out. 

[Vic Harder]

+1 to what rando said.  Just get the DC-DC charger.  I would imagine that it is important to position the charger close to the camper battery to minimize charging losses between it and the battery though!

 

The DC-DC is also a "better" option than heavy wire if you are planning to go LiFePo4 later, and/or you are worried about smoking your alternator.  With 2g wiring on my "dumb" alternator 2002 GMC truck and feeding 275AH of AGM batteries, I occasionally saw 90A when charging, but not for long because of the internal resistance of the AGM batteries.  LiFePo4 batteries have much lower internal resistance, so I imagine (have not tried this yet) that they would suck down even more amps for longer... potentially burning out my alternator.

 

I am using a Victron Orion non-isolated charger.  It delivers 30A to my 200AH Battleborn battery pack in a safe, predictable and controlled manner.

[Jsoboti]

Thanks for the replies. 

 

Doing a quick search of the Victron Orion Instruction Manual, it looks like the lightest gauge wires the recommend is 5AWG from the truck battery to the unit itself. I think that I'm not interpreting something correctly. 

 

You're saying I should be able to have them install the same wiring they do on every FWC install (12AWG right?), slap the DC-DC charger in and be totally good to go? 

 

I'm new at this so I really appreciate the help!

[rando]

The Victron recommendation is unclear, it would makes sense for the output cable, but not for the input cable.   I am pretty sure FWC uses 10 AWG wire, which is rated for (and should be fused for a maximum of) 60A, so you have plenty of margin there.  One thing to note is that they typically install a 30A breaker, if you plan on using a 30A DC-DC charger, you may need to switch it out for a larger breaker. 

[Jon R]

Just as an example, here is the manual for a line of Renogy DC-DC chargers.  Page 14 of the manual has a chart with recommended wire gage versus wire run length and nominal charging current for the upstream and downstream runs.  You should be able to interpolate for a 30 amp charger, or look for a similar chart in the manual for whatever charger you are buying.

 

https://www.renogy.c...4060-Manual.pdf

 

 

[Vic Harder]

To add to what rando is saying (totally agree) I'd go with 40A breakers (one on each end of the wires... you want to protect the wire from a short happening).  Why?  Let's assume the Orion is trying to create 30A output at 13.0V to charge the batteries that are sitting at 12.4V (partially discharged).  30A going across 10g wire will suffer about a 12% voltage drop, or power loss.  Combine with about 5% efficiency (didn't look that up) of the Orion itself, it is conceivable that the Orion will need 36A to generate 30A.  

[Jon R]

The Victron recommendation is unclear, it would makes sense for the output cable, but not for the input cable. I am pretty sure FWC uses 10 AWG wire, which is rated for (and should be fused for a maximum of) 60A, so you have plenty of margin there. One thing to note is that they typically install a 30A breaker, if you plan on using a 30A DC-DC charger, you may need to switch it out for a larger breaker.

What kind of 10 awg wire is rated for 60 amps? Typical rating for 10awg is 30 amps, isn’t it?

Edited by Jon R, 12 November 2020 - 04:08 AM.

[rando]

This is the ABYC (marine) spec, you are likely thinking of household wiring: