Troubleshooting a DC Charging Voltage Drop

[Regular Guy]

I'm experiencing a voltage drop between the truck and the camper when charging. I've done some troubleshooting already with no success. I'm in over my head and appreciate any help I can get. I'm wondering what my next step is.

As background I have a 2022 FWC Hawk with (2) 100 amp lithium, Redarc 30 Manager. I first noticed the issue while on a trip when the batteries weren't charging as expected while driving, charging sometimes but not always. While watching the Redarc remote as I idled I noticed the voltage would slowly drop, sometime faster than others, until it usually hovered around 11/10.9 and then finally stopped charging, immediately voltage at the remote would return to (no load) 12/13. The cycle would repeat after every engine restart (the Redarc "trigger" was set to "ignition").

I checked for voltage under the hood and for any loose connections inside the camper, but everything was fine. I verified that the voltage at Redarc (and breaker before the Redarc) was the same as displayed on the remote. Many times I have pushed on and gave a little wiggle to the trolling motor plug from the inside of the camper without any change in voltage. This is a very awkward reach through the camper to the plug inside the truck bed. I can't push very firmly on the plug and I fear I may not to be able to replug it if I unplug it without removing the camper. I was able to insert probes in both sides of the crimp connectors on the back/fender side of the trolling motor receptacle and there was not a drop there while charging. I did lower maximum charge amps, it made a difference but even at 20 and 15 amps there was still a voltage drop and sometimes charging would stop.

I noticed what I hope is a clue. While wiggling the plug from inside the camper I noticed the wire after the plug was hotter, probably much hotter, than the wire in the fender behind the receptacle. If I grasped wire after the plug I had to release it immediately. I never did this before the issue so I have no idea what is normal, but this seemed way too hot for a wire. And that heat was only after minutes of charging.

My current thinking is something is happening at or near the trolling motor connector. I'm thinking either it is the plug/receptacle itself or the crimp connectors behind the receptacle. I believe the crimp connectors should be suspected more but they seem to test OK and I want to believe that the trolling motor connector is robust and reliable and not subject to voltage drops. For many reasons I'm reluctant to remove the camper and want to avoid that if possible. So I'm thinking maybe my next step is to either try to replace the crimp connectors or try to unplug/replug the trolling motor connector with the camper in place. Both of these actions involve very awkward positions and it may be impossible for me to complete without removing the camper. I would find out once I started.

I'm also thinking that if I removed the camper about all I could do is remove and reinsert the plug and try again. I can't test anything at the connector without being connected to the camper/load. I think I would need an extension cord so I could remove the camper and keep it connected and then check the voltage in the extension.

I don't have a schematic for the FWC but based on the typical setup in the Redarc manual I'm assuming there's just a short run of wire (and a breaker) between the plug and the Redarc. However, when I try to follow the wire after the plug blindly with my hand through the camper it seems like it runs first to the battery compartment. Is there something else, someplace else I should be checking in the camper?

Thanks for reading so far. I do have 2 related questions and would also welcome input. The Redarc manual recommends 6 or 8 wire, it looks like I have 10 from the truck to the connector. If I have to do work with the camper off should I upgrade the wiring and connector to a 8? Also I thought if I had to limp by on my next trip maybe I could charge at lower amps and change the "trigger" to "voltage" which would restart charging repeatedly while driving. Of course, I'm wondering if this would be safe especially considering the hot wire mentioned above.

Any thoughts are welcome

 

[Wandering Sagebrush]

I don’t have any experience with your Redarc gear or lithium camper batteries, but you’ve definitely got a dangerous situation with the hot wire. My guess is you have some corrosion or other reason for high impedance, and it needs immediate attention.

I do believe you need bigger wires, and probably quit trying to charge through the Atwood connector. Consider disabling that circuit, and using a separate set of larger wires and an Anderson connector.

Check Vic Harder’s suggestions that are linked on his profile.

 

[Dadocut]

Dollar to a doughnut says the voltage drop between your alternator and the Redarc is way too high. This problem fits the things you describe. When the Redarc pulls 30 amps, the voltage into the Redarc drops (you mentioned 10.5v). Then the Redarc cuts out and the voltage goes back up. Repeat. That's why you saw the intermittent charging.

You need heavier gauge wire and a better connector. Also, the connector shouldn't get hot. It's either too small a connector or the pins are dirty. The Redarc can pull 30+ amps from your alternator. That's a fairly high current and can result in significant voltage drop over a 10 gauge wire.

You can fix this by running 6 or 4 AWG wire from your battery to the Redarc. Be sure and fuse the wire at the battery. Like mentioned earlier, Anderson makes great connectors for the heavy gauge wire where it enters your camper. I used a MRBF fuse at the battery, 4 AWG wire, and an SB120 connector (bigger connector than I need, but it supports the 4 AWG wire).

I used one of the "upfitter" switches on my F250's dashboard to run an "enable" wire to my DC-DC converter. THat way I only charge the camper from the truck when I throw the switch. I like this so it doesn't load my engine when I'm idling and doesn't charge the camper when I know I'll be getting enough solar. No sense in charging the battery at a higher rate than need be.

Hope this helps and good luck with your fix.

 

[Vic Harder]

+1 to what Dadocut said.

 

[Regular Guy]

Thanks everyone for the input. You made it clear that I have too small of wiring and a not so great connector. The upgrades sound difficult and complicated for me, possibly beyond may capabilities. I'll man up and do it if it needs to be done but I'm not yet convinced it needs to be done. Things have been "fine" in the first 3 years of owning the camper, something just recently changed. Your input also keeps my suspicion on the connector. I'm hoping it's dirty or loose. At least I know my next step. I'm going to disconnect, clean and reconnect and hope for the best. If I find the connector needs to be replaced, I will then probably bite off the upgrades you recommend.

 

[Vic Harder]

Sounds like a reasonable plan. The fact that it used to work wasn’t clear to me, so yes, do that first!

 

[Dadocut]

For several years I too lived with inadequate charging from the truck. It rarely mattered because solar is generally good enough. Initially my DC-DC converter was connected with stock 10 gauge wire. Trouble was the round trip was over 50' and had way too much voltage drop. The wire ran from the fuse box to the license plate area (to power the 7 pin connector for a trailer) then back up to the front of the truck bed. The DC-DC converter cycled on and off from the low voltage but the battery eventually charged.

Repairing or replacing the connector might fix your voltage drop enough that you can get some charging from the DC-DC converter. That and your solar and you'll likely solve most your camper charging.

Replacing the wiring isn't hard electrically but it is a challenge to get all the steps done well: good connections to the battery terminals that already have plenty of wires attached to them, add a quality MRBF fuse to the connector, neatly dress the wiring (bundled together in some sort of wire loom for protections) route the wire from the battery through the truck and to the camper, crimp on a high current connector etc. I also had to buy a hydraulic crimper for all the 4 AWG wire crimps and connectors I was using for this and other camper electrical projects.

Like most projects, fixing up my camper has meant learning new mechanical skills, new tools, and has taken longer than expected. But in the end it works well and its great to get out with things working right.

 

[Bos_Trok]

Battery charging requires a complete circuit, not just one +12v wire. I would be checking your grounds as well, make sure there isn't high resistance between the DC-DC ground and the alternator ground.

 

[GflGdog]

I recently upgraded my wiring to 6 awg completely. I am having a similar issue, and I also used a trolling motor plug. I strongly suspect my issue is the marine plug. I will be changing to the Anderson connectors as soon as we get back home, as that is the only weak link in the wiring. Hopefully that solves your issue as well.

 

[Regular Guy]

Thanks for all your help. Please keep up the good work. It takes a village!

Long story, short, it is mostly the connector and the small (#10) wiring from the truck just adds to the problem. The problem mostly went away when I removed the Atwood and only used a couple of Wago connectors between the camper and the existing wiring and it was even better when I used a new and slightly (15%?) shorter #10 jumper from the truck. There were no too hot to hold spots like before and I was charging for longer periods and mostly at 30a. It seemed like the jumper wire was only warm, evenly down its length, neither side of the Wagos was hotter than the rest. Still probably hotter than preferred.

I think my next step is to just take a bite out of the elephant and only replace the connector and the wiring from the truck at this time. Leaving rewiring the camper, if needed, for another time. This is based on the hope that I can use an Anderson between the new #6 from the truck and the existing #10 in the camper. It looks like SB50s might work. The housings and the contacts, except for the wire sockets, appear to be the same for #6 and #10. Is this right, will this work?

If SB50s or something similar will work I will take all the advice I can get regarding: replacing the thermal fuse at truck battery, type of wiring to use, passing the #6 into the bed through the opening from the old Atwood, the crimp tool required, and anything else I should consider. Links to any recommended equipment would be a bonus!

 

[Dadocut]

I looked at powerworx.com, a Power Pole distributor, and the SB50 has pins for both 6AWG and 10 too (you buy the connector body independent of the pins). They also have reducing bushings to convert to 10 AWG. I'm sure that connector will work well for you.

Not sure if this was mentioned, but run both a positive and negative wire from the battery. That's way better than relying on the car's frame ground. Also fuse the wire at the battery.

I used blue sea battery connectors and attached an MRBF fuse right at the battery. I used "Blue Sea Systems 5191 Fuse Block Terminal 30-300 AMP" from amazon. I was able to attach it directly to my F250's existing battery cables. I used ancor wire too, good stuff. Crimping the SB50 might be a challenge. I've never tried. I had to use a handheld hydraulic crimper for my SB120. Use heat shrink tubing where the connector meets the wire. And some sort of wire loom around the two wires for protection. Hope this helps.

 

[Regular Guy]

Thanks Dadocut. I already ordered a 5191 and a 50 amp fuse. I got my shopping cart set up at powerworx with the Anderson stuff but waiting to order in case I get my wiring from them also. I also found a local shop that will do the crimping. I still need to clarify the type of wire and what to do with the ground at the battery.

Regarding the wire, I saw Ancor black and red single conductor on the Powerworx site. The #10 I'm replacing is 2 conductor in a grey sheath. Since I have to route the wire through the engine compartment and under the cab I'm thinking I need some type of sheath. That led me to Ancor Marine tin plated wire. Is that your recommendation? Is direct burial wire a crazy thought?

My #10 ground was not attached directly to the battery. Are you recommending a certain type of terminal connector for the ground or just a round lug around a terminal post?

 

[Dadocut]

For wire, I used Ancor 113502 tinned copper wire with good insulation. Crimp on connectors were Ancor 242254. I routed both wires in some sort of plastic mesh wire loom that I found on Amazon.. I also had to pick up zip ties with mounts that insert into holes in sheetmetal. And use heat shrink tubing to cover the wire-connector area.

It is ideal to run the ground wire back to the battery. There are many options for going between the battery lug and 1/4" posts that you can connect your wire to.. Many options. Find something that works with the existing wiring on your vehicle. I was able to do something pretty simple but it took a bit of effort to find the parts. I'll post a photo tomorrow.

 

[Regular Guy]

For wire, I used Ancor 113502 tinned copper wire with good insulation. Crimp on connectors were Ancor 242254. I routed both wires in some sort of plastic mesh wire loom that I found on Amazon.. I also had to pick up zip ties with mounts that insert into holes in sheetmetal. And use heat shrink tubing to cover the wire-connector area.

It is ideal to run the ground wire back to the battery. There are many options for going between the battery lug and 1/4" posts that you can connect your wire to.. Many options. Find something that works with the existing wiring on your vehicle. I was able to do something pretty simple but it took a bit of effort to find the parts. I'll post a photo tomorrow.

Thanks again, you saved me alot of research. Things are ordered, soon comes the hard part, the install. I hope to report back in a couple weeks that all went well.

 

[Wandering Sagebrush]

For wire, I used Ancor 113502 tinned copper wire with good insulation. Crimp on connectors were Ancor 242254. I routed both wires in some sort of plastic mesh wire loom that I found on Amazon.. I also had to pick up zip ties with mounts that insert into holes in sheetmetal. And use heat shrink tubing to cover the wire-connector area.

It is ideal to run the ground wire back to the battery. There are many options for going between the battery lug and 1/4" posts that you can connect your wire to.. Many options. Find something that works with the existing wiring on your vehicle. I was able to do something pretty simple but it took a bit of effort to find the parts. I'll post a photo tomorrow.

Well done!

 

[Dadocut]

Here are a few photos of my truck's battery connections to the 4AWG wire going to the camper. I was able to use the truck's existing wire harness and just piggyback on connections to my wire and MRBF. The wires go to the front of the bed. I used a hole punch to open a spot in the bed side and used a simple bushing to keep the wires from getting nicked. I also have two additional AWG 10 duplex wires connecting to the camper. One comes from the dashboard upfitter switch. I use that to enable the 12v DC-DC converter. Th

e other powers a ham radio in the truck and lets me run the radio off the campers battery.

 

[Regular Guy]

Here are a few photos of my truck's battery connections to the 4AWG wire going to the camper. I was able to use the truck's existing wire harness and just piggyback on connections to my wire and MRBF. The wires go to the front of the bed. I used a hole punch to open a spot in the bed side and used a simple bushing to keep the wires from getting nicked. I also have two additional AWG 10 duplex wires connecting to the camper. One comes from the dashboard upfitter switch. I use that to enable the 12v DC-DC converter. ThView attachment 1329591View attachment 1329590View attachment 1329589e other powers a ham radio in the truck and lets me run the radio off the campers battery.

Nice, pictures are worth a thousand words. Your words were also very helpful

 

[Regular Guy]

All went well with the rewiring but now I'm being bothered by my smart alternator.

As someone here said, working with #6 wasn't too hard and a hydraulic crimper made the crimping easy. The Anderson connectors are great and easy to work with. I ran the #6 through the back of the bed, through the drain knockout for bed covers. I ran the running lights wire through the drilled out old Atwood receptacle. All in all it's a purdy installation. My only slight concerns were the connections at the battery. The fuse block is mounted on a small diameter accessory stud and the ground lug is mounted on a small diameter terminal clamp stud, I wish I had larger studs at the battery but I think I got a good connection using washers. At 30 amps I noted a 0.6v drop from the start battery to the Anderson (19') and another 1.2v drop from the Anderson to the Redarc. I can maintain a 30a charge with my alternator putting out 12.7 or greater. Less than 12.7 that the Redarc sees 10.9 or less and stops charging. My alternator often puts out only 12.4 when idling with no load. I believe this confused me my during some of my initial troubleshooting.

Before my problem I didn't pay much attention to voltage and charging, I just knew I got charged up after several hours of driving. I didn't even know or care that I had a smart alternator. Now I'm paying attention. I need to take a road trip and see if I charge up on the drive like the good old days. I need to figure out if my alternator or start battery has an issue. It seems to me, if it was so smart it would know I'm drawing 30a and not cutback to 12.4v. I also need to consider triggering by the ignition (add an isolator and wiring) as recommended by Redarc or keeping it as FWC provided (Auto triggering; on 12.7, off 10). I don't yet understand the difference, I haven't been able to reach Redarc, I think their having phone issues.

I also wonder if, just like previously recommended, the ultimate answer is upgrading the wiring inside the camper (#10 to #6), that should make the issue go away since even at 12.4 with #6 wiring the Redarc would always see greater than 10.9v.

Your help was appreciated, and any more thoughts are welcome.

 

[Dadocut]

Great Progress RE. Your terminal connections at the battery look solid and should work fine. I can't see the wiring but I assume you routed the wires with grommets going through the holes and secured the wire so it doesn't vibrate and rub.

Regarding the "trigger" for the DC-DC converter, I suspect FWC does the auto triggering because it's easier and doesn't require an extra wire. You need some sort of triggering to prevent the DC-DC converter from running when the engine is off. I used one of my F250's "upfitter switches" so I can use a dashboard switch to control the charging. That way I only charge when I need it and can turn it off when I'm starting up a cold engine or if I'll have plenty of sun. When the engine is off the power from the switch is cut and the DC-DC converter turns off.

If you install a switch or connect the trigger to an ignition "happy" wire you'll be able to turn the charger on even if your smart alternator lowers it's output. WIth your new 6AWG wire from the battery and your existing 10AWG wire in the FWC, you're seeing a combined 1.8v drop. Even with an alternator output of 12.4v the DC-DC converter is getting 10.6v when it's pulling 30amps. That is just above the converters input cutout voltage. Might not work, but it's worth a try.

To see how your setup is really working, you should drive and monitor the battery charge current and maybe the alternator output voltage too. My camper battery has a bluetooth BMS so it's easy to monitor from the cab. If the DC-DC converter charges at a 30amp rate continuously then you're golden. It's working good enough. But you might see the DC-DC converter cycle on and off or cycle the charging rate as it keeps starting up and then shutting down due to insufficient input voltage. Electrical debugging is easy when you have visibility to what's going on.

As to your question about replacing the wiring inside the camper, try your current setup first. If it works you're done. If not, move on to the wiring inside the camper. Good luck, you're almost done with the project.

BTW, I checked the voltage drops you're seeing against what one might expect to see for 30amps running through 6 or 10 AWG wire. If your 6AwG wire run is 19', the roundtrip current goes 38'. My table says 30amps throug 6AWG for 38' drops 0.45v. Close enough to what you're seeing. But the 1.2v drop through the 10AWG wire seems high. You're seeing a 1.2v drop over what, 10' distance? A 20' roundtrip w/ 10AWG wire should have a drop of only 0.6v. A connection in that 10AWG path might be loose. While idling the engine and charging the camper battery at a 30a rate, touch each connection and see if anything is warm. (remove rings, watches etc ahead of time!). A thermal camera works too but at these voltages a finger is easier. I wouldn't be surprised if you can lower that voltage drop without replacing the 10AWG wire.

 

[Regular Guy]

Thanks Dadocut. Great feedback. Before I install a switch or ignition trigger I will hit the road and monitor the charging. I wish my Redarc had bluetooth, no such luck but I will install leads from the cab to the battery and monitor battery voltage. I should be able to assume if the battery voltage is greater than 12.7, I'm charging and the Redarc is seeing 1.8v less. I hope for a trip right after Labor day. I figured If I have any charging problems on the trip I now know a few work arounds to get by. The worse thing is my beer won't be ice cold.

Regarding the voltage drops I'm seeing. I'm not sure this is always the case but today I noticed I was charging at 30 but I was drawing 32 plus a little. This was with only essential loads, nothing else was running but I had 2 amps going to the camper vs. 0.1v with solar only. I'm not sure where it was going, but regardless that's 7% more amps through the #6 making the actual drop closer to the calculated.

The 1.2v drop in the camper does seem high especially compared to your estimate. The camper wiring is still very much a mystery to me. I have requested more info from FWC. In the meantime, I will check for warm connections. If I don't notice anything while idling I will make it part of my road trip monitoring. It would be great to find something. I think just reducing the drop by 0.2-0.4v would maintain charging even at the typical low battery voltage of 12.4.

BTW in a previous email I wrote that the Redarc in Auto triggering start at 12.7 and off at 10, it should have read 10.9