Fast Car Charging

I recently purchased a 15 amp 12 volt to 48 volt DC converter with the intentions of seeing if faster charging my AC200 from a vehicle was feasible. Here is a link to the converter I chose:

The description states 10 amp max but the item I was sent was clearly a 15 amp to 48 volt converter. I already had a 175 amp anderson connector installed directly to the battery of my Isuzu Trooper (80 amp alternator which is not much) and I wanted a portable quick disconnect system. I had a few extension cables already fitted with 50 amp anderson connectors so I made up a cable for the converter that would connect from a 50 amp anderson to the 175 amp anderson cable in the Trooper. Pic below:

IMG_6477|666x500 !

Since My alternator was so small, I wanted to use heavy gauge cables and simply used battery cables for the input side and 10 ga. wire for the output 48 volt side to the XT90 connector.

I was able to charge at a steady rate of 574 watts from 37% to full.

The alternator when idling was barely able to keep up with the approx. 55 amp demand and I was able to maintain 12.71 volts from vehicle battery. If I ran the engine at 2,000 RPM, I was able to maintain sufficient voltage unless I turned on both the headlights and AC so this was marginall at best. I connected a 30 amp AC charger to the vehicle (so I would not have to run the engine) to complete the full charge test.

The AC200 remained at 574 watts charging rate until full. The only issue is that the metal casing of the 12 volt to 48 volt *converter got hot enough that I could not touch the bottom for more than about 1 second. No problems were notice other than the hot running unit.

If I were to hard mount this unit in a vehicle that had sufficient alternator capacity, I would mount it with some stand off tubes so that the converter had at least 1/2" of clearance on the botom for air flow. I also think it would be a good idea to mount a small 12 volt PC fan that would constantly cool the converter. I previously tested a 24 volt to 48 volt converter and it did not run nearly as hot. I would also mount the converter absolutely as close to the vehicle batteries as practical with heavy ga. cable. This will maximize the voltage the converter receives which will lower the amp load and likewise will lower the heat output.


For the last test, I wanted to see how much charge I could put into the AC200 by connecting a 12 volt pair of group 24 AGM 2 year old batteries that each have a 78 amp hour capacity. They were connected in parallel and fully charged immediately before beginning the test. The beginning battery voltage was 12.99 under no load / 12.12 while under full charging load at beginning of test / 10.90 under load when test ended / 11.7 under no load at end of test.

AC200 was charged from 0% to 54% in about 1 1/2 hours at which time the voltage converter no longer received sufficient input voltate and the charging rate began to fluctuate down to 174 watts. I discontinued the test as the under load voltage was less than 10.

The voltage converter was hot at the end of the test and the heating increased esp. at the end when the incoming voltage dropped causing a higher amp draw. The casing was uncomfortagle to grab, touch or handle and I would make sure whever it was mounted, that nothing could come into contact with the case that would be easily damaged by heat. The converter does say it has overtemp protection with auto restart, but it never did shut down so I assume the temps were within an acceptable range.

After performing this test, I think there may be a case where it would be advantageous to use a converter like this to use on board battery power alone to charge the AC200 quickly before operating or driving the vehicle. This should enable the vehicle batteries to charge at a much faster rate since full alternator power would then be transferred to charging the batteries via the existing heavy ga. battery cables.

All in all, If a 12 volt to 48 volt converter was available that could output only 10 amps even though it could be capable of 20 to 25 the case heating would be minimized. The challenge with this is that the AC200 wil be trying to pull the full 12 amp input load from whatever is connected and the converter will be overloaded.

Assuming you have a vehicle with a high capacity alternator, this set up while driving should give you the option of receiving a 574 watt incoming charge rate which would fully charge an empty AC200 in about 3 1/2 hours of driving or less if the AC200 was not fully depleted. The unit will draw from around 45 to 55 amps and you will need to plan for high amperage switch, 75 amp fuse or circuit breaker as well as heavy gauge cables on the input side. A 12 volt fan should not be too difficult to mount and could connect directly to the cable attachment points on the converter which would run the fan anytime the converter is running.


I really like the idea of doing this. I’m not entirely confident I have the skills though…
I’ve wired up my whole van, but that seems simple compared to this. I’ll have a think

Want you have a system figured out I would like you to make one for me and I will pay you

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I am flattered by your confidence however ai am strictly a tinkerer and no not know at this point if the products are workable and reliable long term

Hello I agree with Rob…
I have a Bluetti AC200 that I’m trying to charge while driving from my 2015 Kia Sedona’s battery. I saw a YouTube video charging a Goal Zero ( that looked doable for a novice like me. From the battery I used a 30amp fused 14 gauge wire from the battery to the same Victron Energy Orion-Tr Smart 12/24-Volt 15 amp 360-Watt DC-DC Charger, Isolated (Bluetooth).
For output I used a Bluetti supplied battery charger cable with the clamps cut off. (12v/24v Lead-acid Battery Charging Cable – Bluetti (16 AWG?) with XT90 connector to the Aviation cable.
My question is that I show 29V going in to the Bluetti. How long would it take to get to a full charge? The readout on the screen doesn’t show any amps or watts. Any thoughts?
Thank you! Tom

You are outside the voltage range for charging the AC200. You need to get closer to 24 V or 35 or more for charging to occur.

You can charge in “Car” mode when around 24 volts at approx. 200 watts. To increase the charge rate wattage up to 700 watts input rate the voltage must be between 35 and 150 volts. From what you are saying, you are above the 24 volt car charge threshold and below the 35 volt PV charge threshold.

Thanks for your insights. I guess I could go with a thicker wire to increase current? Saw this on eBay Xt90 8awg Silicone Male/Female Pair 8inch (Fully Customizable) any length needed | eBay
I just have concerns about connecting an 8 AWG to the 16 gauge original Bluetti Aviation cable as being to much. The one you made that I saw in another post is nice but I don’t think I can do that. Any ideas? Tom

A thicker wire will do nothing.

The problem you have is voltage which is not dependant on wire size. You can increase the current all you want, but unless you get the voltage in the proper range, you will not see any charging. If you have a 12 volt to 48 volt converter, the 16 ga. wire will carry the 600 watts of charging current fine. The more voltage, the thinner the wire can be for the same amperage of current. Your primary issue is that you do not have a converter that steps up the voltage to a minimum of 35 volts. The Victron unit you purchased will not and is not designed or speced to do what you want to do.

The absolute best you will see is 200 watts of incoming charging power assuming you can get the victron to output 25 volts or so and you have the AC200 set to Car Charge mode in the settings. If the Victron cannot be confifured to output the 25 volts, then you will see no charging.

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Thanks again. Looks like I need a new game plan. I want to van camp but need to run my CPAP machine at night. I have 2 120 watt portable solar panels and would like to boondock when possible. But when cloudy or rainy? Think Oregon…I’m concerned about stressing my 150 amp alternator. Kinda surprised a product is not available from Bluetti that’s compatible. Like the Yeti link.
I like the features of the Victron such as the Bluetooth app, etc. How do you feel about this 40v model?
I appreciate your patience. Tom

I feel the exact same way. This is not a 40 volt unit, it is 40 amps. You keep confusing volts with amps. You must have 35 volts or more to fast charge and the Renogy unit pictured does not provide that. If you are going to power a Cpap machine all night, I would suggest using a Bluetti EB70 and car charge it while driving. The AC200 consumes a larger amount of power just being turned on due to its size and will have consumed more power overnight than the EB70 would.

Scott, I reset the Victron charger to its factory specs

and double checked as per your suggestion if the Bluetti was in car charge mode and not PV. The Victron now appears to be putting out 200 watts to the Bluetti.

I’m OK with that. Thanks again! Tom

Good to hear. 200 watts is a good charge rate and won’t over stress your alternator

You could prob raise the output voltage of the victron to 25.5 or 26 and get a few more watts of charging power

Thank you for your recommendations! Tom

Check out this link for discussion of high wattage vehicle charging from a couple of users. That will give you around 575 watts of charging power while driving

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