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:
Internally, the device features what I believe is a buck-boost design:
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.
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
- 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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