I don't like DC-DC Chargers

Comments · 498

• AN

  @andygsp · 1 year ago · pinned

  I don't think a DC-DC Battery Charger will overcharge a LFP battery.  It can't.  Fiirstly, the battery management system will prevent it from doing so. Secondly, the battery charger is managing the voltage going to the battery and will prevent overcharging - that is literally it's job.  So I don't think you are correct to say it will overcharge an LFP battery, that's one thing it will not do.

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• SA

  @SailingVesselPrism · 1 year ago

  Hello Clarke,<br><br>First-time viewer here—I was referred to your videos because I install and advise other Hans Christian owners with LiFePO4 battery banks on boats. I’m taking the time to write this because it’s easier to address you directly and publicly than to continue answering concerned or curious individuals I’ve already worked with or who are looking to install similar systems.<br><br>After cruising through your videos, I found your approach to charging interesting. I see no inherent issue with it, but it seems more convoluted than it needs to be in practice. My opinion is entirely based on firsthand experience installing, servicing, and using LiFePO4 chemistry since 2018.<br><br>Let me go through the reasons to use a DC-DC charger from a cruiser’s perspective. These are points you didn’t quite mention but are essential for a fair argument about their place in a system.<br>1. Not All DC-DC Chargers Are the Same<br> • I have experience with the exact Renogy model you use, and I can attest it’s not a unit I recommend or would ever use. Its lack of control in charge profiles and the RF pollution it emits while running can disrupt your VHF radio. Specifically, the RF interference dramatically reduces the range of AIS targets at sea, which is critical for safety.<br> • After research and testing, I initially used the Sterling BBW1260. It’s highly efficient (~94%) and waterproof, making it perfect for the marine environment, especially on boats that aren’t completely dry. This was my go-to until recently, when I switched to the Victron Orion-Tr Smart 50A. It’s also IP-rated, equally efficient, integrates with the Victron network, and is fully adjustable via the app. You can even run multiple units in parallel and configure them independently if more output is needed.<br>2. Redundancy<br> • When designing electrical systems for offshore cruising, redundancy and system separation are critical.<br> • In my setup, the engine is wired directly to the starter battery using the OEM wiring, with a burnout fuse placed within a foot of the starter battery. Optionally, I include a kill switch to isolate the engine leads for maintenance.<br> • From the engine side of the burnout fuse, a lead runs to the DC-DC charger, which is also fused for its appropriate current rating. The DC-DC charger connects directly to the LiFePO4 house bank. These chargers are voltage-sensitive, so they activate only when the engine is running and disconnect when it’s off.<br><br>Why is this important?<br>If there’s any issue with the lithium bank—such as a cell failure (unlikely) or a BMS failure (more likely in lightning-prone areas)—the starter battery remains unaffected. The BMS and other electronics are sensitive to EMP hits, but with this setup, a mechanically governed diesel engine can still start and run independently.<br><br>While your system appears to achieve this as well, my design ensures the lead-acid starter battery remains isolated with less wiring. Additionally, the newer Victron Orion has a “backwards start” mode, allowing it to reverse current to help a weak or dead starter battery. Alternatively, a bypass switch can be added to combine the banks temporarily for starting before separating them again.<br>3. Alternator Considerations<br> • Using a DC-DC charger allows the use of an internally regulated or stock alternator, which simplifies installation and reduces costs when upgrading to lithium.<br> • Sizing the DC-DC charger is straightforward: aim for about 50% of the alternator’s rated output. For example, on a 60A alternator, set the charger to 30A; on a 120A alternator, it can run at full 50A output. This prevents overheating and extends alternator lifespan.<br><br>Small-frame alternators are particularly sensitive to heat, and pushing them too hard will dramatically shorten their lifespan—or burn them out entirely. Replacing an alternator in a foreign port is expensive and inconvenient, and overloading it compromises your propulsion system’s reliability.<br><br>While external regulation can increase output, I generally avoid it for smaller setups. Engines with single V-belts are typically limited to 60A. Dual V-belts can handle more, but they’ll generate excessive belt dust from the load. Even serpentine belts transfer significant side-load stress to the crankshaft and water pump bearings, which aren’t designed for such strain. Crankshaft and water pump bearing wear might not show immediate symptoms, but over time, this can lead to significant failures, which are costly and challenging to repair while cruising.<br>4. Proven Reliability<br> • This design has been 100% reliable in every system I’ve designed and installed. My primary concern is always ensuring the engine and its components remain operational and uncompromised to maximize their lifespan and reliability.<br>If you have any questions or want to discuss this further, please feel free to reach out. Thanks for your videos and for fostering these valuable discussions within the community.<br>- Jon Neely S/V Prism

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• PE

  @peterkadelbach7010 · 1 year ago

  I have had a 30A one in my van for 3 years and it works like charm.

  12

• 0X

  @0xdeadbeeef · 11 months ago (edited)

  Hi Clark. Great to see a product like yours. 6 years ago I came to the same conclusion as you and designed and built my own &quot;bank manager&quot;. It uses a shunt and FET switches. It also has a low voltage switch for the consumers and a charge input for solar. There is a 4 row separate display.

  1

• RZ

  @Rz8551 · 1 year ago

  Another good video. Thanks Clark

• SV

  @SVFresh2Salty · 1 year ago

  We have a victron DC-DC and it’s fully programmable . Pretty happy with it, we run it off the engine to power the house when under way.

  2

• EL

  @Eli-InTheWolverineState · 1 year ago

  I own one, but I am in the cold north. And yes I use it for my lead acid semi batteries. It seems to work good at our off grid camp.

  2

• MA

  @matthewsellers82 · 1 year ago

  Your arguments are well made as are many of the comments. Constructive discourse is good for everyone.

  1

• JA

  @jacobjohnson7125 · 1 year ago

  I&apos;m doing a project right now where I&apos;m putting together a pan-tilt kit (just got done with that), hooking it into a Bottango servo shield, and from there to a Raspberry Pi (going to put an all-weather camera enclosure on top of the pan-tilt and put thermal cameras in it - the schedule will keep the thermals from getting damaged by the sun when it comes up in the morning, possibly before I get up). &nbsp;I bet you&apos;d be tons better than me at getting the electrical hooked up. &nbsp;Here&apos;s crossing my fingers I don&apos;t smoke it when I do that next.

• DA

  @DavidPritt-xh7qq · 1 year ago

  Clark, <br>There are good reasons to have DC-DC chargers.<br>I have one on my boat that pumps 24v from my 12V LiFePO4 bank to the batteries my bow thruster uses.<br>Likewise I keep the starter batteries maintained using Victron Orion DC-DC boxes.<br>The shore and Solar power go to the Lithium bank, managed by a Bank Manager.<br>Keeps the lead acid batteries happy over winter when the boat is not used.

• KA

  @kajuan85 · 1 year ago

  I use my 60a dc dc charger in my semi truck. I run lead acid for the truck, and 3 190ah agms for accessories. Works fine for me!

• AN

  @andysutils · 1 year ago

  My victron one works great. It saved me the massive cost of having to purchase an additional solar panel and an additional charge controller for my lithium battery.<br><br>You&apos;re right about the output though. They do limit the capacity that they are advertised.