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abeness avatar image
abeness asked

SmartSolar MPPT 100/30, DC-DC boost converter as input

Hello, all. I would value a quick check on my plans as I'm building out my portable project.

What I want to do is use a 12V to 28V DC-DC boost converter to provide alternate power input from my 250A alternator at sufficient voltage, when PV input is not available. Yes, I know I could pick up (and did consider) an Orion Tr-Smart, but how many blasted chargers do I need when a simple boost converter can provide the power and my MPPT controller can run the pro charging algorithms? ;-) This is a portable project with physically switched connections; no plans to burn up my solar panels by connecting them to a DC supply.

This Victron unit is rated at 30A charge current, so theoretically 432W at 14.4V out. Nominal PV input max for 12V is 440W.

I understand that the controller will limit additional input current, so my understanding is that the SmartSolar would pull only its max capacity from a larger boost converter. So a 560W boost converter ought to do the trick, with ~20% headroom so as to not run full-out.

Any flaws in my plans? Thanks!

MPPT Controllers
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abeness avatar image abeness commented ·

To follow up, the 12-28V 560W Daygreen DC-DC boost converter I installed on a board next to my SmartSolar MPPT 100/30 to supply alternator power as alternate "PV" input works perfectly. I put MC-4 connectors on the output side so I can easily switch the SmartSolar between solar and alternator input.

Side note: I've learned that the ratings/quality of those inline circuit breakers are unreliable: the 50A unit I had installed on the 12V supply was tripping on less than 40A draw. I was able to reduce the SmartSolar output to 20A and limp along, but now even the reduced draw trips the inline breaker after a while. On to a better replacement.

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radioactiveskull avatar image radioactiveskull abeness commented ·
how you going, my name is wayne. what you have done 12 to 28v to work on your charge controller interests me as i have a 24v/28v Alternater...im wondrering if i could add another victron 12/24 100/30 Via the altenater to help ease the load on the 1st controller, i have 1 30v/100v 8a solar panel.. runs @ 32/35v 8a. going to use Lynx Distributor. any info would really help. newby
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JohnC answered ·

Hi @abeness

One issue you may face is the Victron mppt is designed for solar panels. It requires a min 5V difference between battery V and 'feed' V, which reduces to min 1V when charging. Even the adjustable Victron converters don't go beyond 30V, unless you chose a 12/48. 30V is maybe enough if your batts are down?

You could also consider paralleling in a 'flat' (but adjustable) converter, set to (say) 27.0V to charge (but not overcharge) your 24V bank while driving, and let the solar top it off daily with the full algorithm. No switching connections either.

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abeness avatar image abeness commented ·

Hi, JohnC. Thanks for the voltage reminder and suggestions. Sorry that in my tired state last night I apparently omitted making clear that I’m charging a 12V battery, which is why I’m planning to use the 24-28V boost converter to ensure that I will always have Vbatt+5. Plus reduce cable gauge requirements a tad. This really is a backup/portable power project, not an installed system. Movement (between home, vehicle, and outdoors) is inevitable. It’s in a Pelican case.

With this in mind, does it sound like my capacity assumptions are correct?

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JohnC avatar image JohnC ♦ abeness commented ·

@abeness

Yeh, good you've allowed for that. Your figures look ok.

You might also look at a battery combiner, like these: https://www.victronenergy.com/battery-isolators-and-combiners/cyrix-battery-combiners


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abeness avatar image abeness JohnC ♦ commented ·

Err, seems my last comment went in as an answer instead of reply, maybe mobile device confusion. Moving it here:

Battery combiner looks like a useful tool. Thanks, and for the verification. Good weekend.

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