Renogy DCC1212 DC-DC charger teardown


It's winter here in the southern hemisphere. That means shorter and more overcast days and less solar energy charging my son's 2013 Sprinter's LiFePO4 house battery. To augment the solar system we recently installed a Renogy DCC1212 DC-DC charger, the 40A version. Before installing it, I wanted to take a look at the build quality - the Renogy is priced quite a bit lower than many others, did they take any shortcuts to get to that price?

The short version is though I did note one undesirable assembly-related issue, the device appears to be well made and good value for money.

The device is configured via 4 DIP switches, for a LiFePO4:
  • S5 = OFF (battery charge profile = Lithium)
  • S3,S4 = ON (for Lithium)
  • S1,S2 = OFF (charge termination voltage; 14.0V)
    • 14.0-14.6 in 0.2V increments
The connections are straightforward, heavy duty terminals for input and output, and two control signals:
  • D+: on/off (connect to "engine running" signal)
  • LC: low charge rate, 12.5% (optional, connect to switch to control high/low charge current); the purpose of this feature is unstated and I'm as puzzled as Will is as to its utility

Internally, the device features what I believe is a buck-boost design:
  • one heatsink: 4 x HY4306 MOSFETs
  • other heatsink: 2 x 40CPQ100 Schottky rectifier diode pairs, 40A
  • two fans with a plastic separator that appears to be intended to direct airflow over two distinct "halves" of the board
    • the fans only turn on when needed
    • the fan wiring passes by the heatsinks and is protected with a braided sleeve
  • two separate control boards, one on the input section, one output
    • output has 2 x trimpots (I didn't try fiddling with them :))
    • the device markings are unclear (have been removed), but both boards have "program" headers so presumably they're microcontrollers
  • 2 x 40A fuses on input (in parallel)
  • "JP" capacitors, 105C
  • the case appears to be electrically isolated (well, excepting the flaw discussed below), a basic continuity test shows open-circuit from all combinations of input-output, and to chassis

The teardown photos below show all of the above. They also show the one concerning issue I found: two different length case mounting screws were used, and the longer screws come awfully close to PCB pins (within less than 1mm). It's not hard to imagine a tiny conductive piece of detritus floating in to the unit through the ventilation holes and bridging the gap. I trimmed the screws down before reinstalling them.

One last note: if you do disassemble your charger, make sure to position the plastic air divider correctly - it's easy to miss this and then wonder why on earth your charger is buzzing once the fans kick in!

The last shot is as-installed in the Sprinter, within the passenger seat pedestal. It's alongside the diesel air heater which might get a bit warm - but hopefully that won't be an issue as the heater is only ever on when the vehicle is stopped, and the charger only when the vehicle is moving.

For the Sprinter, I connected the charger to the spare link conveniently available at the battery distribution block, via a 60A MIDI fuse (much as this fellow did). The Sprinter has a 220 A alternator, and Mercedes' Sprinter Body & Equipment Guidelines 2016/2017 section 7.3.1 indicates the maximum alternator load is 40A. The Sprinter has a D+ signal under the driver's seat, this becomes active a few seconds after the engine is actually running (i.e. not just when the ignition is on) - perfect for this use case.

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air guide.jpg

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Solar Enthusiast
Thanks for this info. I just received a DCC1212-20 to install into my motorhome. I chose the 20A version because I did not want to overload the 80Amp alternator, but FYI, the LC (Current limit input) now limits the current to 50% of the units rating. I wish I would have read the specs more closely and got the 40A version which I could have limited to 20A when desired.

I'm in Canada so its spring right now and still waiting for my LiFePO4 (2x100Ahr) to install.

I see you wrote this nearly one year ago. Do you have any updates now that you have some experience with this unit?



G'Day RF; the DC-DC charger has been running fine for since installation; it was invaluable over the 2020 winter (southern hemisphere), and will no doubt get some exercise in this coming winter.

The 'low current' switch to 50% rated current is good news; actually could be useful. The manual that notes this is labelled v1.4; as it happens I bought another unit earlier this year for another vehicle, however I believe that's also a v1.2 unit (12.5%). Oh well.


New Member
Great writeup bdl! Any idea how many mA the Renogy draws on that D+ to turn it on? I'm using a BMS (Electrodacus SBMS0) that can only supply up to 50ma before needing extra circuitry. I'll be picking up the 60A version.


Great writeup bdl! Any idea how many mA the Renogy draws on that D+ to turn it on? I'm using a BMS (Electrodacus SBMS0) that can only supply up to 50ma before needing extra circuitry. I'll be picking up the 60A version.
Ta; alas I've not been able to catch up with my son (well, his van at any rate!) to measure the current draw from the D+. I'd expect it to be quite low of course. (then again, what do they say about assuming things? :)


Solar Enthusiast
I used a pair of #22 signal wires for the D+ and Low Current (LC) signal wires. I measured the voltage drop (about 6m of wire) and found it to be well under a volt. They call for #18 I believe... Anyway I can hear the "click" of a small relay when D+ is energized, so I can't image the current draw being over 200mA on either input.
I used a SPDT center OFF switch to select OFF, ON(hi), ON(low) currents.


Solar Addict
I have the 40A version in my truck. I'm confused about the Low Current (LC) option. Can you explain what it does and how to wire it? Thank You....


Solar Enthusiast
The low current mode just reduces the "Bulk" charging current to 50% (12.5% in early models). So if you have a 40A version, applying 12V to the LC input will reduce the output charging current to 50% or 20Amps. This will mean charging will take twice as long in the Bulk charge mode, but it will reduce the load on your alternator... say on a very hot day with your AC going at MAX.


Solar Addict
Thanks, my truck has a 220A alternator so I shouldn't have any issues with overload. So far, the DC to DC charger works great!