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24v/6s: Will a positive ground charge controller work with a dc-dc converter?
#1
Hello everyone,
So my order for the POS charge controller from china got cancelled on aliexpress and i went and bought myself a 40a renogy rover mppt, and i bought the positive ground version because it was $50 cheaper than the negative ground version. So i have plans to use it hooked up with this 480w 12 to 24v step up converter with a switch in between so i can only turn it on during highway rides so i don't burn out the alternator. And also the charge controller will be wired to two 170w  12v panels in series that i have so i'll be able to have the 370wsolar+480w from alternator charging going even on sunny days, theoretically. But my main question is will this dc-dc converter fry the positive ground charge controller since the car battery is negative grounded? I'm  running two cables from the car battery of course.
Here is the charge controller: https://www.amazon.com/gp/product/B07DNV..._qh_dp_hza
and the step up converter: https://www.amazon.com/gp/product/B081RF...UTF8&psc=1

Anyway positive ground seems like a horrible idea, why is it even a thing? I think I'm gonna have to return this charge controller.
*Or should i set it up so that i by pass the charge controller all together and just hookup the dc dc converter to the battery pack directly and keep an eye on the voltage manually?
I chose 6s because 24v is basically 100% full whereas for 7s it would only charge it past 20% percent or so (24/7=3.42v)
Thank you in advance for any infoz!!!
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#2
Back in the day there were vehicles that uses Positive ground. Not sure why, but I remember my uncle telling me about it. Usually was on 6V systems.

As long as the physical device cases don't touch, you may be ok. However, I'm not EE and not sure. You might need to use an isolator transformer to make the conversion over to Neg ground.

This is interesting question. I didn't even know they made Pos ground MPPT's or inverters.
loserextrodinaire likes this post
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#3
(06-09-2020, 08:09 PM)Korishan Wrote: Back in the day there were vehicles that uses Positive ground. Not sure why, but I remember my uncle telling me about it. Usually was on 6V systems.

As long as the physical device cases don't touch, you may be ok. However, I'm not EE and not sure. You might need to use an isolator transformer to make the conversion over to Neg ground.

This is interesting question. I didn't even know they made Pos ground MPPT's or inverters.

hmm interesting, thanks for the reply. Another question that is inerrant in all this is will the dc dc converter plus the solar panels interfere with one another or the charge controller when they are both turned on? the wattage is well within the limits of 40a. I've seen this done with cheap pwm controllers with battery packs on youtube where they used a pc power supply with 12v through a pwm controller to charge there pack and it seemed to work well.
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#4
If you keep all the wiring (& case) except the pos ground controllers output wires isolated from the chassis & other wiring, it should be fine.
The panels wiring will have to isolated too. The panel's frames should already be isolated from the panel's cells & wiring, but best to check that is so.

If you try & do it manually, it'll end badly! Make sure it's automatic!
Korishan likes this post
Running off solar, DIY & electronics fan :-)
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#5
Agree with Redpacket. Also, use an DMM in Ohm/Resistance/Beep setting and check multiple times to absolutely verify everything is isolated. You don't want throw the switch and see a bunch of smoke bombs going off.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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