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Old 20-11-2019, 14:40   #1
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Bypassing Inverter for DC > DC charging

I'm in the midst of reworking my whole electrical system, and am realizing that a most of the things I'd be using an inverter for would be charging other batteries - tools, phones, rechargeable AAs, etc. It seems silly to run all those things through an inverter when I just want DC power at the end of the day.

Is there a decent way I can hook these tool-specific batter chargers (e.g. DeWalt 20v) up to a 12V socket? Does the voltage of the tool matter? Obviously, the phones/tablets are no trouble, but everything else comes with an AC plug. I'm assuming I can't just cut it off and splice the DC plug on.

Thanks, ye wiring wizards!
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Old 20-11-2019, 14:59   #2
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Re: Bypassing Inverter for DC > DC charging

No, you need a 12V (car) charger for each device or battery type.

aka DCDC converter.

And yes much more efficient.
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Old 20-11-2019, 15:05   #3
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Re: Bypassing Inverter for DC > DC charging

Look on eBay, you will find a lot of DC DC converters at different power ratings. They are sold with a range of voltages, you tune the voltage you want with a sort of potentiometer with a screwdriver.


Buy a couple of them - they are only a couple of dollars - and set one up for every voltage you need. It won't break the bank
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Old 20-11-2019, 15:17   #4
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Re: Bypassing Inverter for DC > DC charging

Right, I'll get a couple of those DC DC converters and hook em up to DC sockets. So then how do I modify the chargers themselves to use the DC power? Surely I don't need to buy ready-made DC chargers for everything, assuming they even exist.
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Old 20-11-2019, 15:21   #5
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Re: Bypassing Inverter for DC > DC charging

You will need to buy an car charger for each device since they are the brains the devices battery charge profiles. Dewalt DCB119 is about $100.

Personally, I would just use the inverter if show power was not available. That's what I do.
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Old 20-11-2019, 15:54   #6
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Re: Bypassing Inverter for DC > DC charging

Your main DC voltage is nominal 12V (10-15)

As long as each DC converter / charger accepts that input you're fine.

Barrel / pin size, polarity and enough watts / amps / mA are the other factors.

Start with what you think is the hardest, post here
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Old 20-11-2019, 15:57   #7
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Re: Bypassing Inverter for DC > DC charging

Hmm. What about a device like this: Haisito iMAX B6 80W 6A Lipo Charger RC Battery Balance Discharger for LiPo/Li-ion/Life/LiHV Battery (1-6S), NiMH/NiCd (1-15S), Rc Hobby Battery Balance Charger LED W/AC Power Adapter https://www.amazon.com/dp/B07QRQT3LC..._UrC1DbVV0Y4P9 ?
Found this video that makes it look easy: https://youtu.be/aKm_lA5gz4A .
Bad idea?
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Old 20-11-2019, 16:27   #8
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Re: Bypassing Inverter for DC > DC charging

How often do you need to charge? A small 100w inverter or thereabouts should be fine for tool chargers and will save the overhead of running the main inverter.
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Old 20-11-2019, 16:32   #9
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Re: Bypassing Inverter for DC > DC charging

Not often. I just thought it would be cool to bypass the AC altogether. Philosophically speaking.
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Old 20-11-2019, 16:48   #10
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Re: Bypassing Inverter for DC > DC charging

I'd go the small inverter option. I have an 18V DC supply charger and a 12V AC supply charger that has (ironically) no 12 volt DC supply version available. With a small inverter, the efficiency losses aren't worth losing sleep over. I find the best policy when the energy budget is tight is to charge the tool batteries when there is plenty of power available; Marina, middle of the day solar, engine running etc.
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Old 20-11-2019, 18:46   #11
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Re: Bypassing Inverter for DC > DC charging

That hobby charger is great for RC batteries, but in your case needs DC input not AC.

Again, be specific about what you want to power and/or charge, there is no one "suits all" device.
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Old 21-11-2019, 02:15   #12
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Re: Bypassing Inverter for DC > DC charging

If your device draws DC from a 110v/DC wall wart or brick converter you can bypass these converters and connect boat battery power to your device directly thru a DC/DC step-down buck converter. Buck converters are highly efficient. These devices give you adjustable output voltages to suit your device. Check amp ratings of your devices compared to buck converter. Typically converters delivering low amps are just circuit boards, med amp boards have heatsinks and the higher amp boards will have multiple heat sinks and/or fans.
You need to be a bit of a hobbyist to use them as they are, in most cases, just circuit boards. My son has 3D printed a nice case for the boards I am using. It's a fun project yet very useful.

https://www.amazon.com/DROK-Adjustab...4326179&sr=8-5

I don't use the board above as It's too fancy. Lol. However, I do use Drok. They have lots of different types of boards. Like I said, a fun project. Don't forget to add a fuse.
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Old 21-11-2019, 02:27   #13
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Re: Bypassing Inverter for DC > DC charging

There is one universal power supply, it is the mains AC voltage. In terms of efficiency, the losses involved in using inverted AC is a few % of a few Ahr. Worst case say 80% inverter efficiency to charge a 18V 2Ahr power tool, you would waste 36 WattHrs or about 3Ahr @ 12V which assumes the DC-DC conversion is 100% efficient, which it isn't. The maths tell me to concentrate my efforts elsewhere.
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Old 21-11-2019, 02:34   #14
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Re: Bypassing Inverter for DC > DC charging

Quote:
Originally Posted by Santiano View Post
Right, I'll get a couple of those DC DC converters and hook em up to DC sockets. So then how do I modify the chargers themselves to use the DC power? Surely I don't need to buy ready-made DC chargers for everything, assuming they even exist.
The DC-DC converter tuned to the output voltage of your AC charger is your new charger. You do not need that 110AC to xxDC charger anymore! Keep it simple
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Old 21-11-2019, 02:48   #15
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Re: Bypassing Inverter for DC > DC charging

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Originally Posted by Reefmagnet View Post
I'd go the small inverter option. I have an 18V DC supply charger and a 12V AC supply charger that has (ironically) no 12 volt DC supply version available. With a small inverter, the efficiency losses aren't worth losing sleep over. I find the best policy when the energy budget is tight is to charge the tool batteries when there is plenty of power available; Marina, middle of the day solar, engine running etc.
We do the same. Laptop runs off a 100w inverter, 12v > 240v > 19v and the tele is the same off a 350w inverter. Its not worth getting too excited about a few watts that could be saved with alternative systems and the inverters also run the battery charger for the Dewalt drill, soldering iron, dremel and finally slow cooker.

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