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shagginwagon83 Mon Nov 28, 2022 8:06 am

I am considering externally mounting my Redarc DC/DC charger since it is a self-contained unit (no fans) that is meant to be cooled with airflow.

The spot I am thinking of is the wall behind the tail light - since this area receives cool air from the rear vents. So technically this area is 'engine bay' area - but I believe should be fine while moving. I imagine in traffic the unit will get hot and throttle down charging - which in my opinion is desirable in traffic.

I could also make a right angle bracket to raise the unit up into the rear vents more - but then I will not have visibility of the LEDs on the unit.

Quote: While the REDARC BCDC1250D AUS | US is designed to be used in extreme climatic conditions, it performs best when not mounted inside hot engine bays. Commonly they are installed in the cooling airflow in the front of the radiator. With the correct gauge wiring, though, itís possible to mount them almost anywhere within your adventure mobile.

revolution337 Mon Nov 28, 2022 9:02 am

Does the exact location you are thinking of mounting it keep the operational LEDs easily visible? Or only with the engine cover off?

Mine is mounted under the rear bench seat. Initially when I mounted it, I wanted to keep the LEDs visible, but didn't actually plan on looking at them very often. Now that I have had it installed for over a year, I found myself checking on the status LEDs quite often, especially when camping and using solar. It's nice to be able to see at a glance in which mode the unit is currently charging (bulk, float, etc). The LEDs also serve as a display for any error messages that may occur. I will say that I am very glad I mounted the unit in a location with easy visual access to it. I can't imagine it being mounted somewhere "hidden". Just my .02

shagginwagon83 Mon Nov 28, 2022 9:15 am

revolution337 wrote: Does the exact location you are thinking of mounting it keep the operational LEDs easily visible? Or only with the engine cover off?

Mine is mounted under the rear bench seat. Initially when I mounted it, I wanted to keep the LEDs visible, but didn't actually plan on looking at them very often. Now that I have had it installed for over a year, I found myself checking on the status LEDs quite often, especially when camping and using solar. It's nice to be able to see at a glance in which mode the unit is currently charging (bulk, float, etc). The LEDs also serve as a display for any error messages that may occur. I will say that I am very glad I mounted the unit in a location with easy visual access to it. I can't imagine it being mounted somewhere "hidden". Just my .02

Engine cover off only. What issues have you ran into with yours? My battery has a bluetooth BMS and I can verify charging through that.

My current DC-DC and solar setup has been pretty much set and forget.

Also - it appears you have the 25amp model mounted inside on wood. Have you experienced any thermal throttling? With the 50amp model I imagine I would at minimum need to mount it to metal.

revolution337 Mon Nov 28, 2022 9:47 am

shagginwagon83 wrote: Engine cover off only. What issues have you ran into with yours? My battery has a bluetooth BMS and I can verify charging through that.

My current DC-DC and solar setup has been pretty much set and forget.

My battery does not have any bluetooth functions, but I have a small battery monitor mounted right near the battery as well. I had to make a few tweaks the the setup right after the initial installation, but since then it was been working flawlessly.

One other thing to note about the updated versions of the Redarc unit. When the charging profile is set to "lithium", the unit will not allow charging below freezing . I have experienced this first hand, with my van parked in my garage. Ambient temps were about 28* F one morning. I went out and checked the LED status on the BCDC unit and noticed it was flashing LEDs which matched the error code for "unit under temperature". Once the ambient temp came back above freezing, the error message went away. Keep this in mind if you plan on mounting the unit where temps may frequently get below freezing.

My aux battery is installed directly next to my BCDC unit, so I know that if the BCDC is below temp, so is my battery. If you have the BCDC mounted outside the van (and its below freezing), but your aux battery is installed inside the van, where it is warmer, it still won't allow charging until the BCDC is warmed up enough.

From Redarcs website:

Quote: As of December 2019, there are two features that have been added into the BCDC Dual Input range.

The BCDC will not attempt to charge a Lithium (LiFePO4) battery if the ambient temperature is below 0įC/32įF (note LiFePO4 charging profile only). This feature is designed to help protect your Lithium battery and maximize its service life.

shagginwagon83 Mon Nov 28, 2022 10:00 am

revolution337 wrote:
From Redarcs website:

Quote: As of December 2019, there are two features that have been added into the BCDC Dual Input range.

The BCDC will not attempt to charge a Lithium (LiFePO4) battery if the ambient temperature is below 0įC/32įF (note LiFePO4 charging profile only). This feature is designed to help protect your Lithium battery and maximize its service life.

Well, that pretty much ends this thread. Bummer - as the BMS should be in charge of controlling the charge. I messaged Redarc asking if this feature can be disabled.

Thanks for that info.

revolution337 Mon Nov 28, 2022 10:58 am

shagginwagon83 wrote: Also - it appears you have the 25amp model mounted inside on wood. Have you experienced any thermal throttling? With the 50amp model I imagine I would at minimum need to mount it to metal.

I have not yet noticed any thermal throttling due to excessive heat. When my battery has been heavily discharged, and the unit puts out the full 25 amps for several hours, it does get noticeably hot. Never enough to back down the current, though. I imagine with the 50 amp version, you would want as much cooling capability as possible.

I want to say that I recall reading somewhere that the only way to bypass the low temp charging projection is to wire in a manual override switch that changes the battery mode from lithium to something else, like AGM (the low temp protection is only active in lithium mode) temporarily until the BCDC warms up enough. But that is a less than desirable solution for most.

I'm curious to hear the response from Redarc regarding the low temp charging protection. Please let us know what you hear from them.

tikiman71 Mon Nov 28, 2022 11:12 am

I installed my Redarc BCDC1240 behind the driverís seat, so it would be closest to my under-seat 135ah battery and provide access to the unitís indicator lights. That said, itís worked flawlessly for 2 years and never gave me a reason to look, other than to say hi. I also like being able to reach back and check its heat output, which is never more than warm to the touch. It is mounted to the Westy laminate cabinet, but elevated with washers for airflow.

It typically charges in excess of 40 amps while underway, usually around 42-43. This is from my "stock" EJ22 95 amp alternator which will be upgraded when I have a chance.

My battery seldom goes below 70%, so the Redarc does not spend much time charging and getting hot. I could see this being a potential issue if one has a deeply discharged battery. The system has been completely set and forget since installing, and Iím considering getting rid of my solar panel at this point, as it contributes very little to the overall system.

Good to know about the temp control revision. I will need to check to see if my unit has it since I have been relying on the Overkill BMS to handle temp restrictions. Iíve only had it to 40 degrees F so far.

Good luck with your system. I enjoy your posts. Cheers!

shagginwagon83 Tue Nov 29, 2022 7:42 am

Quote: Hello Brandon,

Thank you for your inquiry and continued loyal support of our products, I hope this reply sees you as having had a great weekend so far and looking forward to your week aheadÖ

My name is ----, Iím the International Training and Development Manager here at REDARC and Iím an integral part of our North American Customer Support Team.

Iíve attached here a copy of the BCDC1250D manual for your reference, check out page 11 as this illustrates a typical wiring diagram to help better explain the installation and application process.

BCDC1250D Dual Input 50A In-vehicle DC Battery Charger - REDARC (redarcelectronics.com)

Our Lithium profile is not able to be disabled in any way, this has a minimum charging threshold of 0įC (32įF)

In some circumstances, we have advised customers if their battery allows it, switching the charging profile to ĎA/AGMí allows charging temperatures as low as -20įC (-4įF)

This proves successful when traveling during the colder season, as long as your battery (BMS) allows it, it should be noted alsoÖ when using the ĎA/AGMí profile for a lithium battery, the recovery is likely to be ~90%

Please be assured, selecting the AGM setting will not damage the lithium battery in the slightest, however, you might find it going to float a little earlier than normal, resulting in a maximum charge of ~90% SOC.

Selecting this profile when traveling during these temperature extremes, also helps protect the battery by not saturating the lithium cells to 100%... 😉

It should also be noted, it is industry standard that lithium batteries should not be charged at temperatures below 0įC (32įF), however, if the battery specifications allow this, then Iím confident our solution above will provide the charging performance requiredÖ

This too could be achieved by simply placing a switch between the orange and green wires of a BCDC1250D i.e. on for LI profile and off for A profileÖ

I would however strongly suggest, given your environment and battery specs, youíd likely be better served by placing the BCDC1250D inside the cab also?

Thanks again Brandon, for many more tips and diagrams, please be sure to reach out to me directlyÖ Iím here to help!

Keep well, travel safe and have a great night!

Best regards,


Well it looks like it is going in the cab. I was hoping to save some interior space by mounting it externally...I guess not now.

revolution337 Tue Nov 29, 2022 8:58 am

Thanks for the update, that was a quick response on their end! It's good to know that at least one has the ability to safely bypass the lithium mode if required.

Maybe this helps give them feedback for future product model updates.

MsTaboo Wed Nov 30, 2022 6:13 pm

revolution337 wrote: Thanks for the update, that was a quick response on their end! It's good to know that at least one has the ability to safely bypass the lithium mode if required.

Maybe this helps give them feedback for future product model updates.

Yeah, they need to address this for those who have self-heating LiFePO4 batteries.
If the DC-DC charger won't allow any current to the battery when cold the self-heating unit won't have the juice to heat the battery before charging can start.

Howesight Wed Nov 30, 2022 8:09 pm

Even though the Redarc DC-DC chargers are rugged and have high build quality, I still would not want mine subjected to the elements outside of the vehicle - - like slush, mud, salt, etc.

My install location is very close to the location of my LiFePo4 battery - - by design. When camping in cold weather, I always use my CDH and if ambient temps are really cold, I leave the door open on the cabinet where my LiFePo4 battery lives. That keeps it well above freezing.

I realize that if our rig were not a spoiled garage queen, I might have times when the battery and the Redarc could get below freezing temps. If so, I would run the engine and use the factory heater until the battery got up over freezing temps. The risk I prefer to avoid is accidentally charging the LiFePo4 when it is below 32F degrees.




dobryan Wed Nov 30, 2022 8:12 pm

^^^^ But you have a BMS which will prevent charging when below the lower set temp limit.

T3TRIS Wed Nov 30, 2022 10:15 pm

Agreed, the BMS can handle the cold temperature threshold, especially since having a temperature sensor NOT on the cells themselves isnít very useful. This is definitely a drawback on the Redarc charger that I wasnít aware of when getting ours. I was actually thinking of relocating our charger to the outside somewhere, but now am rethinking because of that internal temperature sensor (not the durability of the charger though).
Changing the chargerís battery profile could be a good solution though (albeit not ideal of course). Iím thinking a normally-closed temperature switch. Both wires can be bridged by that temperature activated switch that would be powered by a key-in signal. The sensor would be taped to the outside of the charger. When the temperature is low, the switch is open and the chargerís in AGM mode. As soon as the chargerís temp climbs above a set temperature, the switch closes and the charger profile becomes lithium again. If the switch looses power, itís normally closed and the charging profile remains lithium.
The question is: does switching profiles while charging damage the charger?

shagginwagon83 Thu Dec 01, 2022 8:16 am

T3TRIS wrote: Agreed, the BMS can handle the cold temperature threshold, especially since having a temperature sensor NOT on the cells themselves isnít very useful. This is definitely a drawback on the Redarc charger that I wasnít aware of when getting ours. I was actually thinking of relocating our charger to the outside somewhere, but now am rethinking because of that internal temperature sensor (not the durability of the charger though).
Changing the chargerís battery profile could be a good solution though (albeit not ideal of course). Iím thinking a normally-closed temperature switch. Both wires can be bridged by that temperature activated switch that would be powered by a key-in signal. The sensor would be taped to the outside of the charger. When the temperature is low, the switch is open and the chargerís in AGM mode. As soon as the chargerís temp climbs above a set temperature, the switch closes and the charger profile becomes lithium again. If the switch looses power, itís normally closed and the charging profile remains lithium.
The question is: does switching profiles while charging damage the charger?

I just responded to Redarc asking about switching profiles while charging. I imagine the charger would heat up quick given charging at 50 amps.

This is a bummer of a 'feature'. I am still on the fence about mounting it inside vs outside. The temperature-activated switch is a great idea, however not sure if it's worth working through that rather than just mounting to the inside.

revolution337 Thu Dec 01, 2022 9:40 am

shagginwagon83 wrote: This is a bummer of a 'feature'. I am still on the fence about mounting it inside vs outside. The temperature-activated switch is a great idea, however not sure if it's worth working through that rather than just mounting to the inside.

Although I certainly understand your point, I wouldn't really call this feature itself a "bummer". The real bummer in this instance is not being able to manually select or bypass this feature if not needed in your application.

Lithium aux batteries are still a relatively new product on the market. Each year they are getting cheaper and easier to produce, but still cost more on average than an equivalent lead acid. I understand that a lot of battery manufacturers are making batteries that are self heating, and a lot of BMS's also have low temp charging protection build in. There are still plenty of lithium batteries that have no low temp systems in place, and that is where this Redarc feature comes into play. It's a nice "safety net" to have in place in the battery system, in case you are using a lower priced battery (non heating) or BMS without the low temp features.

In any case, I would love to see this feature kept in future Redarc units, but have it manually selectable/de-selectable.

MarkWard Thu Dec 01, 2022 10:18 am

Different manufacturer, but I wanted my dc to dc charger as close to my battery as possible. My logic was, its the DC to DC charger that is "cleaning" my alternator output voltage. By having the shortest run possible between my dc charger and my battery, I've lessened any sort of voltage drop that could show up due to length of cable, size, and resistance over time.

shagginwagon83 Thu Dec 01, 2022 12:03 pm

MarkWard wrote: Different manufacturer, but I wanted my dc to dc charger as close to my battery as possible. My logic was, its the DC to DC charger that is "cleaning" my alternator output voltage. By having the shortest run possible between my dc charger and my battery, I've lessened any sort of voltage drop that could show up due to length of cable, size, and resistance over time.

This is sound logic - and works for most use cases. My desire to mount externally was due to the cooling needed for the 50 amps of fury.

MarkWard Thu Dec 01, 2022 1:19 pm

I spent a lot of time thinking about what size dc to dc charger to get. I ended up with a 20amp charger. My alternator is a 120 amp charger. Camped with the heater running I use maybe 10 amps a night. Once on the road, my SOC is 100% in less than an hour of running the engine. Curious, how much power are you folks using in a 12 hour period?

shagginwagon83 Thu Dec 01, 2022 2:20 pm

MarkWard wrote: I spent a lot of time thinking about what size dc to dc charger to get. I ended up with a 20amp charger. My alternator is a 120 amp charger. Camped with the heater running I use maybe 10 amps a night. Once on the road, my SOC is 100% in less than an hour of running the engine. Curious, how much power are you folks using in a 12 hour period?

I will let you know once I am working on the beaches of Baja. Starlink satellite internet (5A DC), two laptops (one being a 230w developer laptop), a fridge, and a heater.

Battery bank is 280aH. To charge from 0% - 100%, it would take 14 hours at 20 amps, or 5.6 hours at 50 amps.

MarkWard Thu Dec 01, 2022 2:35 pm

shagginwagon83 wrote: MarkWard wrote: I spent a lot of time thinking about what size dc to dc charger to get. I ended up with a 20amp charger. My alternator is a 120 amp charger. Camped with the heater running I use maybe 10 amps a night. Once on the road, my SOC is 100% in less than an hour of running the engine. Curious, how much power are you folks using in a 12 hour period?

I will let you know once I am working on the beaches of Baja. Starlink satellite internet (5A DC), two laptops (one being a 230w developer laptop), a fridge, and a heater.

Battery bank is 280aH. To charge from 0% - 100%, it would take 14 hours at 20 amps, or 5.6 hours at 50 amps.

Sounds like work to me.



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