Using a step up Converter 12V to 24V to charge blows fuse

Charging up a EB70 in the vehicle using a 12V to24V (10amp) Step up converter. The cigarette plug is a quality plug with an Anderson connector on the end. Fuse in the cigarette plug is a 15 amp (F15AL glass fuse)

The Bluetti started charging at 183 watts and ran for about 7 minutes. The fuse in the cigarette plug then blew. The step up converter was VOM tested and put out 24.1 volts.

My understanding was that the draw was still limited to 10 amps and I don’t understand why a 15 amp fuse would blow inside the adapter.

Thank you for any help!

If the bluetti was charging at 183 watts, then it was using approximately 15.25 amps at 12 volts (and that’s not taking into account any losses from the conversion). Definitely over the fuse limit.


Thank you. Appreciate your help. So even though the Bluetti was showing 183 Watts and the input was at 24.1 volts, the math for this is still 183 watts at 12.0 volts in order to get 15.25 amps? I thought it would have been 183 watts at 24.1 volts which is 7.6 amps.

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That converter will take slightly over 20 amps at 12 volts to provide the maximum of 10 amps at the 24 volt output. It is doubtful that the wiring in the vehicle for the power outlet would be sufficient for that current draw. What you may want to consider is to run wiring directly from the battery, with an in-line 25 amp fuse (I recommend an automotive auto-reset breaker), and use that to power the converter. That would supply the current you need and allow full use up to the 240 watts the converter can provide.

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Aw yes, makes sense. Yes, I think running a larger cable directly to the battery with a larger fuse is the way to go.

Thank you again!

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10 amps at 24 volts would require approx. 22 amps of 12 volt power to produce. SInce your fused recepticle is limited to 15 amps and you were drawing more amperage than 15, the fuse blew.

You are also going to find that you will need a 20 amp converter rather than the 10 amp converter you have. Running the 10 amp converter will run it at a temp that is very very hot since it will be maxed out all the time. A 20 amp capacity running at half capacity will run cooler and longer. You can also put a small 12 volt fan on the converter to assist the cooling.

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Thank you Scott. You have been very helpful on a few questions.

I had seen a video of someone using a 12-24V step up converter to charge their Bluetti. Think it might have been Hobotech. They mentioned or maybe I assumed they used the 12V accessory port on their dash to power it. I again assumed that since it was a 15 amp port, I was ok. Since I obviously didn’t do my homework, I don’t think this will be a good solution for me and I need to go a different route.

I think I may go ahead and install a Redarc DC DC battery charger instead since I will end up having now to run new power cable from under the hood to my house (van) power.

I have been right on the fence to either add the AC200P or the EB240, (already own the EB70) but that was based on charging from my cigarette port. Since I really need the 12V DC storage capacity and have no need for an inverter, I may end up just wiring some LIFePo4 batteries in parallel to my fuse panel in the van. I had planned on solar up on the fiberglass roof but long story short, it is not the way to go on this van.

Thank you again!

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