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frontpage Posted by Navy-Wife | Staff • 6d ago
frontpage Posted by Navy-Wife | Staff • 6d ago

Rombica 2-Port Up to 75W Car Charger (1x USB-C, 1x USB-A) w/ 2-Pack USB-C Cables

& More

$4.05

$8.99

54% off
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iHPower Labs Inc via Amazon has Select Rombica Car Charger on sale from $4.04 when you visit the 50% off coupon page to activate (or clip the 50% off coupon on the product page). Shipping is free with Prime or orders $35+.

Thanks to Deal Hunter Navy-Wife for finding this deal.

Note: Refer to the individual product page for complete details regarding the charging rates for these car chargers.

Available (prices after 50% off coupon):

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Written by Corwin | Staff

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Community Notes
About the Poster
iHPower Labs Inc via Amazon has Select Rombica Car Charger on sale from $4.04 when you visit the 50% off coupon page to activate (or clip the 50% off coupon on the product page). Shipping is free with Prime or orders $35+.

Thanks to Deal Hunter Navy-Wife for finding this deal.

Note: Refer to the individual product page for complete details regarding the charging rates for these car chargers.

Available (prices after 50% off coupon):

No longer available:

Editor's Notes

Written by Corwin | Staff

Original Post

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19 Comments

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Quote from Dave_B :
All the cars I've owned/driven have used 20 amp fuses for the power ports. So, theoretical max power would be 240 watts. However, no USB charger is 100% efficient, so I'd guess the actual power limit for USB charger output is closer to 190 watts. If your car uses a 10 amp fuse, you'd risk blowing it with chargers outputting 100watts. The exact number depends on the charger efficiency.Also, if you use the charger when the engine isn't running, the battery voltage will drop(as it's not being charged by the alternator) and the current being pulled from the port will increase(amps = watts/volts). So, your laptop could be pulling 100watts from the USB charger on a 10 amp fuse with no issues while the engine is running, but when you turn off the engine (or if auto engine stop activates) your fuse might blow. On a 20 amp fuse this shouldn't be an issue for a 130 amp changer.
Your car battery would be 'dead' (aka would not start your car) if it was only delivering 10 volts thus had the hypothetical risk of delivering 10a at 100w. ("amps = watts/volts"). We are talking about a 12 volt battery that normally should be 12.6 and 12.8 volts when the engine is off to be considered 'healthy.' If your car battery falls outside of that range you have bigger problems than a 30 cent fuse or worrying about your laptop's charge.

For reference:
-A car battery is generally considered dead or very low when the voltage drops below 10.5 volts
-To pull over 10 amps at 100 watts, the voltage would need to be slightly less than 10 volts.

LOL....so yes, when completely stranded on the side of the road with a dead battery and gaming or editing video on your laptop (to have it even ask for 100w) you could, in theory, pull 10 amps from a 100w charger. But I guess that is the way you could pass the time waiting for the tow truck
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Quote from Dave_B :
You're assuming 100% efficiency in a DC boost converter, which is literally impossible. I have no idea what the efficiency of this device is, but if we assume 80%, then it would pull 125 watts from the car in order to supply 100 watts to the laptop. If the battery is at 12 volts, that would be 10.4 amps, and in danger of blowing a 10 amp fuse.
So you admit you'd still need a functionally dead battery to make your hypothetical problem even theoretically possible. Hardly a counter argument. At 10 amps your engine isn't even going to make a sound when you turn the key. But you are still gaming away with your laptop drawing from that dead battery? LOL

Quote :
I'm speaking from experience on this. Years ago, before USB-C, I used to run a laptop off an inverter plugged into the car power port. It would work just fine while the car was running, but blow the fuse nearly immediately after the engine was turned off, and that was a 20 amp fuse.
I love when evidence is based on a single random anecdotal account from decades ago.

Regardless, so a 100w load would blow a 20 amp fuse?!? Run your "amps = watts/volts" to let us know when that would be. Hint...5 volts. Was your car a 6 volt PowerWheel?

And I don't doubt you had a blown fuse, but pretending that a 100w load (or 125-ish watts at 80% efficiency) caused a 20 amp fuse to blow (unless faulty) is just plain silly. There was something else drawing power or there was a problem within the circuit.

Speaking of your "100w load," that inverter was probably pulling 150-200w input (if it was rated at exactly at 100w output). Your inverter, which takes DC to AC then your laptop transformer converts it back to DC far less than "100% efficient" (huge losses at each of those ***three conversions***) compared to a 12v-to-12v (DC-to-DC) device. I'd assume assume your inverter was actually rated at 200-400w output so could pull 250-500w, even if the demand wasn't there.
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Dave_B
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I feel you're being disingenuous now.

In your response to the first quote, you mention 10 amps. Now I assume you mean 10 volts, but in the text you quoted I am specifically referencing a scenario with a battery at 12 volts. Are you really claiming that if you turn the key with a 12 volt battery, your engine won't turn over? A car battery can easily drop to 12 volts if your engine is off and you're still pulling power.

As to your comments on the second quote, I never referred to that as evidence, but rather my personal experience. You're the one referring to that as evidence, not me.

Furthermore, I'm not sure where you're getting the idea that my laptop only used 100 watts. I never made that claim, so all the calculations you base on that are irrelevant. As I described, this is before USB-C, so my laptop didn't have the 100 watt limit that most USB-C charging laptops are bound to. My laptop was likely pulling well over 100 watts, which is why it caused a 20 amp fuse to blow in a car with a fully functional battery (and not just once, but multiple times) until I got in the habit of unplugging my laptop before the car was turned off. And yes, of course an inverter is a much less efficient way to power a laptop in a car than a DC-DC converter. After a bit I did buy a 3rd party universal car power port laptop power brick to reduce power draw.

Also, you claim that an inverter pulls power based on its maximum wattage rating, which is false. It only pulls the amount of power necessary for it to provide the power currently being demanded by the device plugged into it.

If you draw 100 watts from the AC plug on an inverter rated for 500 watts, it probably pulls around 120-150 watts from the car power port.

If your laptop draws 160 watts from the power adapter, the power adapter could demand 200 watts from the inverter, which could demand 250 watts from the car power port. As long as your car battery is around 13 volts or higher(such as when the car is running), a 20 amp fuse will likely hold up, provided it's accurately rated and assuming no significant resistance in the car wiring. (realistically, given that fuses have a margin for error and the wires carrying the power though the car do have resistance, the fuse could easily trip at a lower wattage) But, if you shut off the engine while your laptop is still using 160 watts, thus still pulling 250 watts from the car power port, the battery could quickly drop to 12.5 volts, resulting in 20 amps being demanded from the car power port to supply this power.

That is how a 20 amp fuse blows.
Last edited by Dave_B June 8, 2025 at 08:31 PM.
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azchadillac
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Coupon code says 50% off but it is 0% at checkout.
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Quote from Dave_B :
I feel you're being disingenuous now.
Said the person claiming 100w is going to blow a 10 or 20 amp fuse @ 12+V....what a properly working car battery outputs. The rest of your fairytale voltages are completely make believe and wouldn't be possible if you car were still able to start. I see little point in discussing these disingenuous "what if's" outside of properly functioning circuits and cars.

Furthermore; not sure what was worse; you confusing your 'years ago' 12V DC to 120V AC inverter back to 12V DC transformer situation with direct 12V DC to 12V DC device....or thinking you are going to be pulling 5 volts from a 12V car accessory outlet to exceed 20A on a 100w load.

FYI: I didn't read the rest, you have proven you have no idea what you are talking about and I have invested enough time trying to help you understand something clearly beyond your grasp....or waiting for you to admit you were wrong in your original claim. No biggie, we all make mistakes but moving goalposts endlessly is not helpful nor makes you less wrong at the end of the day.

BTW. no one else on the planet has blown a fuse with a 100w load on a 10-20A 12V accessory outlet (everything properly working on a 12V circuit of course) ...but thanks for the warning for something that could only happen if I need to charge my laptop on a dead car battery outputting far less than useful voltage.

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