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Do mppt boost buck solar chargers exist? What to do....

scottc19

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Joined
Mar 10, 2022
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I'm in a weird predicament.

Background:
I have a camper van that I built about 3 years ago and my wife and I lived in it for a year. Now I am looking to change out my old lead acid setup to ideally a 16s 304ah lithium system in order to run some higher power electric devices. Yes this will be a huge pack and I will have multiple ways to charge it, shore power, alternator, solar. I have a massive roof rack but solar space is somewhat limited( have to have some space to walk around to load ww kayaks). I currently have a sunpower 345 panel that has been working great, its a nice panel Vimpp 57.2, Impp 6.02. I am going to add a second panel (300-400watts), but have been unable to find a similar panel that I can put in series with this one. Most larger panels I have found for sale around are 8-10amps.

So then I was thinking I would get two chargers one for each panel and run them in parallel, but the sunpower panel is in an odd voltage area and would require a buck/boost charger... I looked online a bit but didnt find much one or two Chinese chargers but no datasheets. I know mppt buck/boost chips exist (they come up when I search for chargers) but doesnt look like manufactures have started using them yet, probably because the use market is pretty small. Has anyone found anything or have any ideas?

I know the most logical solution is bumping down to a 24v system, my EE background just cringes at the idea of running so much current and having to use big wires to reduce voltage drop when it can be avoided. So this is my last ditch effort before I give in.
 
Most larger panels I have found for sale around are 8-10amps.
Its not the worst thing in the world to have slightly mismatched panels. If you have a (using your rough numbers) 400W panels with Imp of 8A, put in series with your existing panel:

345W + (400W x 6A/8A) = 645W (you leave 100W up on the roof).

Not a disaster if it makes everything else work. It'd essentially be like finding a bigger 300W panel that matches your existing 345W.
 
If you're using separate solar charge controllers then the voltage/amperage of each panel doesn't matter. The MPPT controller will figure out what voltage your battery needs. However, for a 48 volt system that probably won't work. The PV voltage input will need to be higher than the system voltage. If each panel can't provide ~60 volts then it won't charge a 48 volt battery.

You're going to need to put two panels in series to get a voltage high enough.

What high power electric devices are you looking to use?
 
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