Bluetti, Espar, Low Voltage, No Heat

Bluetti AC200 fails to start Espar M2 B4L heater due to low voltage at the heater or potential CAN bus communication error.

Espar heater starts and runs reliably with car battery. I believe the wiring harness is functioning correctly.

It appears my problem is with the Bluetti DC 25 amp output. When checking the startup voltage, it drops to approximately 11 volts at the heater just long enough for the Espar EasystartPro (CAN bus) to stop the ignition process and/or throw an error code. Or, maybe the DC voltage isn’t clean enough for the CAN bus. Voltage at the Bluetti and heater is 13.25 volts.

Apparently, many lithium battery systems are not working well with Espar heaters for unknown reasons.

I need help finding a fix to make my Bluetti power my Espar/Eberspacher heater.


If your startup voltage drops to 11 volts, my first thought is the length of wire run is too long between the Bluetti and the heater or the wiring size is too small which is allowing excessive voltage drop. How long is your wiring run and what ga. is the wire? If too small the first thing I would try is larger ga. wire from the Aviation output connector to the heater. You could also build an aviation cable with 12 ga. wire that would allow more current with less voltage drop.

The length of cable is about 13.5 feet, 12 ga. wire with one crimped and soldered butt splice. 8-9 amp is supposed to be the maximum needed at start up.

I’ve read that the Bluetti AC200 ramps up the power as needed and apparently, it’s not fast enough for the Espar.

I find it interesting that a small car battery out of my Honda runs the Espar just fine. It’s hard to get an accurate reading on the voltage drop. I believe the Espar will only tolerate a .5 volt drop.

Thank you for your help.

Your car battery is probably capable of providing a momentary instant 500 or so cold amps and the Bluetti is only about 5% of that. The early Bluetti Aviation output cables were 16 ga wire and you may get a better result by rebuilding your cable with 10 or 12 ga. The shorter the run and thicker the cable, the better chance you have.

Have you by chance connected the Espar directly to the cig socket to see if it overloads indicating a high amp draw initially?’

I inspected the Bluetti Aviation plug yesterday. It’s made with 14 gauge wire; however, I wasn’t able to confirm the wire being soldered to the pins.

I did try the cigarette socket and Bluetti gave a fault of Low Voltage which I assume was due to >10 amps.

I was looking last night at finding a source of WEIPU SA20 plug to build 12 ga. short cable. I’d assume not using a Blue Marine fuse block, bypassing it for now, is beneficial.

Where does one purchase 12 gauge 100% copper wire? The 12 gauge wire I purchased was tinted. It is silicone and appears to be good quality.

Thank you.

You can change the actual contact pieces in the shells to change the gender.

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Here’s what I have (details):

3’ Bluetti Aviation Cable 14 gauge (between Bluetti AC200 and Patch Cable)

3.5’ 12 gauge Patch Cable (between Bluetti Aviation and Blue Sea System Fuse Block)

13.5’ 12 gauge Espar Wiring Harness (between Blue Sea System Fuse Block and Espar Furnace) including 1.5’ added length of 12 gauge to Espar Wiring Harness

This totals approximately 20’ between Bluetti and Espar Furnace (17’ of 12 gauge plus 3’ of 14 gauge). Looking at a Blue Sea System chart, I have approximately a 3-4% voltage drop at 10 amps or 0.5 voltage drop. I may need to try using a 10 gauge wire from Bluetti to Espar furnace.

I have tried skipping over the Patch Cable and Blue Sea System Fuse block. It made no changes on the Espar heater starting.

To date, I have several recommendations:

  1. Put a lead acid buffer between the Bluetti and Espar heater. See if it works.
  2. Add a large capacitor similar what is done in 12 volt audio systems.
  3. Use a good quality, 120 volt to 12 volt DC converter.

I don’t have details on how to accomplish any of the recommendations.

Bluetti’s customer Service has responded via email. We’ll see if they have a recommendation. They’re very slow and I’m not sure they truly understand my issue. It would be nice to learn more about this “lag time under initial load.” I still feel that the Bluetti (less the lag time) and current wire configuration should be acceptable to the Espar Furnace.

Thank you for the help.

How about trying connecting your heater directly to your heater with your exising 3’ Bluetti output cable without all the other wiring you have.

All you need to do is connect and XT60 connector to your heater input wire (close to your heater) and plug that end into the yellow XT60 connector at the end of your 3’ bluetti output cable. If you no longer have the XT60 yellow connector on your bluetti output cable, just wire up whatever you have to be as short as you can between the bluetti and your heater.

If the heater works fine that way, you know your cable runs are too long to carry the high short term (spike) current that may be tripping off your heater error.

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Yes, this is a good thought. I have everything I need to try this; however, the Espar wiring is somewhat complex within itself. See picture.

I’d like to bypass Espars 13.5’ 12 gauge power cable in it’s entirety to minimize voltage drop. I don’t want to cut any Espar wires. I’d like to tie into the main plug titled “to heater.” I know which wire are plus and negative, but they’re not easy to remove from the plug.

I have a recommendation from Esoar to “put lead acid buffer between the system (Bluetti) and the heater.” Exactly how to do this isn’t apparent. Plus, it sound risky.

This is a problem for Will.

Have you found the solution for your Espar powered by you Bluetti AC200P? I bought the AC200MAX lately and experience the very same problem…Espar fan starts for a couple of seconds and everything shuts off afterwards…no heat produced. The Espar is plugged on a Blue Sea distribution panel with a 20A fuse.
If i plug the Espar directly on a 100AH lithium battery…everything is fine.! I bought the Bluetti to power up my Sprinter van. I do not need more than 30A DC… and 2200W AC is perfect for me. But this is a major flaw since the heating system is a must for me (Canadian) !! Also the power meter is no accurate. everything is shutting off when there is still 28-30% remaining on battery (according to the screen) !

@BLUETTI I’m having this same issue. Based on the specs of the Bluetti and the Espar S2, I cannot see why this would not work. When I use a car battery the Espar works fine. The only difference I can measure is that when I use the battery, the output voltage is steady at 12v, when I use the AC200MAX (30A RV) the output voltage jumps around between 13v and 14v.

I don’t have this equipment to test it; however, the issue appears to be a matter of the start-up surge current, and over sensitive equipment. However that would seem to mean that adding a large capacitor close to the heater could help for the start-up current need. Perhaps it would be worth someone trying to a capacitor like this one I linked below.

I saw this: put a small 12v battery as a buffer (recharged by the Bluetti) as for the solution with the capacitor proposed by Mr hnymann : Powering Esbar S2 D2L diesel heater from Bluetti B230 12V/10A cigarette lighter port | Page 2 |

Thanks to you both! I will try the capacitor and my backup plan is to use a battery and charge it from the AC200MAX. Thanks again.

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I was in the process of testing out an inline battery with charge controller and noticed the charge controller had a “power supply” mode. I removed the battery and just put the charger inline, then set the output voltage to a constant 12v and the heater works great. For some reason the S2 does not like the 13+V from the Bluetti but it does love a constant 12V. No battery, capacitor, or anything else required.

I’m using a charger from Victron, DC/DC isolated, again, set in power supply mode. Make sure you remove the remote charge jumper, connect it all up, use the bluetooth app to set the mode to “power supply” the reinsert the jumper and you’re good to go.


Congratulations for the discovery. I see in the specifications that this intelligent charger/power supply (victron orion tr smart 12/12 -18: 18A nominal/220w) is capable of stabilizing the voltage and maintaining a maximum output current of 25A at nominal output voltage, for 10 seconds. It must be sufficient for the inrush current of the appliance.

I saw another model in the specs above which could be even closer to the specifications of 12v RV port 25A(ac200p) / 30A (ac200max ac240…) of the bluetti AC or D40 for the AC200L : the victron orion tr smart 12/12 -30 (30A 360watt nominal) >>Maximum output current of 40A (10 s) at nominal output voltage.

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Thanks again for the guidance here. It’s nice to have an active forum with real solutions! Appreciate it. I might upgrade to the one more closely matched, too.

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Thanks especially to you who have found a solution that I’m sure will interest many people here !

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