Shocked Touching my 12v Car Battery

Hello, I have a Ecoflow Deltra Pro Ultra and wanted to charge it from my EV car battery during power outtages to bring me from 2 days to probably 8-10 days. My car has no official way to bring power out of the traction battery but I know it has a 150amp DC converter to keep the 12v battery maintained. So I ordered off aliexpress a 20amp 12v to 48v step up converter and used that 48v output to feed the low volt 15amp solar input on the Delta Pro Ultra.

Everything was working while testing, and it was showing 700watts input so I went around touching things to see if anything was heating up.. I touched the wires and connectors and when I touched the positive lead on the 12v car battery I got a shock... not a big shock.. but it felt like someone was putting a powerful vibrator in my hand. During this test the Delta Pro Ultra was not plugged into the wall. At the time I was barefoot on the garage concrete and may have been leaning against the plastic bumper cover and my other hand was not touching anything... it was holding my phone recording: check out those cat-like reflexes in action...

Could someone with experience chime in to let me know what I did wrong? I assume it needs grounding? Was that an AC shock or DC shock? Does the Ecoflow backfeed AC? Is that dangerous to use as is if I dont touch those terminals? Is it risky to the car electronics? Or did I just miss a memo growing up that you can't touch a high current draw DC terminal?

**EDIT, wanted to note I rehooked it up and wanted to touch the car frame to test if that would shock.. and yes it does.

Welcome! Watching intensely. I want to do the exact same thing with my son's Chevy Bolt to charge my 48V server rack battery.

Delmar said:

I want to do the exact same thing

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Maybe not exactly the same

Many inverters, at least inexpensive AIO, drive some AC onto PV input leads.
The solution for AIO and hybrids is to ground (bond) PV panel frames to inverter chassis. And to a ground rod.

But PV+ and PV- are NOT to be grounded, just connected between array and inverter.

Your car has 12V battery negative tied to chassis. If you wire car chassis to inverter chassis, that may or may not be a problem.

I haven't found a spec sheet for Ecoflow Deltra Pro Ultra, or an actual installation manual, just some on-line thing.

"

• When connecting solar panels in series, ensure that the maximum voltage output of all panels is within 30V-150V for the low-PV input port, and 80V-450V for the high-PV input port (you can choose either low-PV or high-PV if the maximum voltage output of all panels is between 80V and 150V).
• To avoid product damage, ensure that the solar panels are properly connected to the low-voltage PV or high-voltage PV input port.
• If you connect the EcoFlow DELTA Pro Ultra to PV system circuits installed on or in buildings, according to NEC regulation, the system shall include a rapid shutdown function to ensure the safety of operation and reduce shock hazard for emergency responders.
• If you wish to connect the EcoFlow DELTA Pro Ultra to PV system circuits, the consultation before purchase and the installation must be done by a qualified electrician or installer.

"

If the 12V to 48V DC/DC has isolated output, I think grounding chassis together would be fine. But maybe not if non-isolated.

I would take a meter and measure voltage from both the pos and neg terminals to both car and earth ground. I assume the battery is floating? Also measure without the Ecoflow DC converter connected.

For safety could you run a ground wire from battery neg to earth ground?

Hedges said:

If the 12V to 48V DC/DC has isolated output, I think grounding chassis together would be fine. But maybe not if non-isolated.

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Would there be harm in leaving it as is.. and just... not touching the 12v battery positive terminal?

I assume you would get a similar shock while touching any bare metal on the car.

Static straps used to be a thing in dry Wisconsin to prevent shocks when getting out of your car.

Use a meter to see AC (and DC) voltage between 12V+ terminal and inverter chassis, also to earth ground.

Was inverter connected to anything, or just sitting on garage floor? It's AC output, depending on where it goes, would drive everything in your setup to line AC voltage.

Check 12V- terminal (car chassis) to inverter and to earth. As Delmar noted, it is expected to be a similar shock hazard. Just 12VDC lower than 12V+ terminal.

Hedges said:

Use a meter to see AC (and DC) voltage between 12V+ terminal and inverter chassis, also to earth ground.

Was inverter connected to anything, or just sitting on garage floor? It's AC output, depending on where it goes, would drive everything in your setup to line AC voltage.

Check 12V- terminal (car chassis) to inverter and to earth. As Delmar noted, it is expected to be a similar shock hazard. Just 12VDC lower than 12V+ terminal.

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I rehooked it up and can confirm.. bare metal on the car also shocks. I put my multimeter in AC voltage mode and touched it to the +/- 12v inputs on the DC inverter and car and it didnt read anything. The DC stepup inverter was sitting in the engine bay but on plastic trim. The Ecoflow inverter was just on the garage floor, and had a heatgun plugged into it, and that is it.

"and to earth."
There is no earth on this setup - the battery "generator" is portable and not plugged into earth and neither would the car.

If my ecoflow was plugged into the house, would that ground it and stop this from happening? Current state, the outlet I want to use has a GFCI and the Ecoflow trips it before it ever starts charging. The internet says to get a 2 prong converter stat strips out the ground, and then use the GFCI, but I can swap the outlet out for a standard one so it has a functional ground.

This has me concerned about also buying a smaller inverter gas/propane generator to charge it during a power outtage.. would that be energized too? It would be plugged into the 120v plug though.

You have two probably unrelated issues:

"There is no earth on this setup". Your feet are earth grounded and are completing the circuit for the shock.

"The internet says to get a 2 prong converter stat strips out the ground," The neutral in your house panel is bonded to ground.

Delmar said:

You have two probably unrelated issues:

"There is no earth on this setup". Your feet are earth grounded and are completing the circuit for the shock.

"The internet says to get a 2 prong converter stat strips out the ground," The neutral in your house panel is bonded to ground.

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Good point on the ground bonded to neutral.

If I resetup this thing again but have the Delta Pro Ultra also plugged into the house outlet, should that mean there is no more shock when touching the car frame?

Not much AC voltage between +/- DC inputs.
But try checking for AC voltage between a DC pin and the inverter chassis.

The concrete has high resistance, some conductivity due to moisture. That limited severity of shock. If you grounded inverter to house ground, water pipe, etc. then you might get a more dangerous higher current shock if you touched car chassis and something grounded. I think it is driving its DC input pins to AC voltage. I don't know if it is DC coupled or AC coupled through a capacitor which would be current limiting.

You do NOT want AC line voltage going in one hand and out the other. Been there, done that. The outcome is a matter if timing relative to your heart rhythm, a form of Russian Roulette.

I think you are best off not connecting a non-isolated source to the inverter. Something like PV panels is good, and ground the frames. Maybe a 48V battery or 12V battery + boost converter inside an insulated box.

In other words, I recommend you don't feed it from car battery as you have done. You could use a 12V inverter to feed its AC input for charging. Bond and ground the various chassis.

MtnXfreeride said:

off aliexpress a 20amp 12v to 48v step up converter and used that 48v output to feed the low volt 15amp solar input on the Delta Pro Ultra.

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Perhaps not the ideal purchace to connect to an expensive EV.
Are you certain the EV HV to 12v battery charging process is not generating a high voltage impulse?

Probably safer to use the EcoFlow Alternator Charger, which was designed for what you are doing. Although it may or may not be compatible with your particular EcoFlow model?

Otherwise, would suggest running ground cable from the EcoFlow to the vehicle chassis. There should be a ground bolt on the Ecoflow somewhere.

Is the DC/DC stepup converter isolated?
It must be.
The MPPT is NEVER isolated ... so you got the AC on it.
This means part of the Ecoflow own AC is on your battery cable.

This is similar to that test I posted long ago where a non isolated basic inverter's AC is present on the DC side ... so if this inverter is grounded then the battery cables and terminals can give a lethal AC shock.

mrzed001 said:

The MPPT is NEVER isolated ... so you got the AC on it.
This means part of the Ecoflow own AC is on your battery cable.

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Not quite true. I think it is safe to say, assume MPPT is NOT isolated these days (like over 15 years) on string inverters.

There are indeed still millions of isolated MPPTs rolling off the assembly lines every year — microinverters.

zanydroid said:

Not quite true. I think it is safe to say, assume MPPT is NOT isolated these days (like over 15 years) on string inverters.

There are indeed still millions of isolated MPPTs rolling off the assembly lines every year — microinverters.

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Only one recently used MPPT unit is isolated the Victron Smartsolar RS 100-200A.
All others are not.

Microinverters jep I forgot about them. But not all microinverters are isolated only the good ones.
Saw some that dont even had a relay on AC side.

MPPT is not isolated on hybrid inverters, off-grid inverters, on-grid inverters.

Drunk Engineer said:

Probably safer to use the EcoFlow Alternator Charger, which was designed for what you are doing. Although it may or may not be compatible with your particular EcoFlow model?

Otherwise, would suggest running ground cable from the EcoFlow to the vehicle chassis. There should be a ground bolt on the Ecoflow somewhere.

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Ecoflow dropped the ball here because the altenator charger isnt compatible with the ultra pro. Neither are either of their smart generators.

mrzed001 said:

Microinverters jep I forgot about them. But not all microinverters are isolated only the good ones.
Saw some that dont even had a relay on AC side.

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Hmm, interesting. I assumed that the isolation is required for safety, since otherwise the DC side is low voltage safety class. The two I considered for my house (Enphase and Hoymiles) both were isolated. (Also thought the AC output disconnect was pretty common, though I think it's safe for it to be FET and not relay based).

Non-isolated IMO is reasonably sane if both the input and the output sides are similar voltage class. That's the same for most hybrids and AIOs. I wouldn't expect 80V+ DC strings to be touch safe.

The EcoFlow MPPTs with low minimum DC side voltage is kind of questionable, because what happened to the OP becomes possible.

Hedges said:

In other words, I recommend you don't feed it from car battery as you have done. You could use a 12V inverter to feed its AC input for charging. Bond and ground the various chassis.

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And to reinforce the concepts here. Pretty sure 12V->120VAC inverters are required to be isolated.

DC DC converters in general are probably safer to assume to be non-isolated, unless advertised to be isolated. Since it's more expensive to build an isolated one (need to add an internal transformer [could be LF or HF] big enough to pass the power)

Drunk Engineer said:

Probably safer to use the EcoFlow Alternator Charger, which was designed for what you are doing. Although it may or may not be compatible with your particular EcoFlow model?

Otherwise, would suggest running ground cable from the EcoFlow to the vehicle chassis. There should be a ground bolt on the Ecoflow somewhere.

Click to expand...

Ecoflow dropped the ball here because the altenator charger isnt compatible with the ultra pro. Neither are either of their smart generators. If the power is out

zanydroid said:

And to reinforce the concepts here. Pretty sure 12V->120VAC inverters are required to be isolated.

DC DC converters in general are probably safer to assume to be non-isolated, unless advertised to be isolated. Since it's more expensive to build an isolated one (need to add an internal transformer [could be LF or HF] big enough to pass the power)

Click to expand...

"Non isolated between input and output"

MtnXfreeride said:

Ecoflow dropped the ball here because the altenator charger isnt compatible with the ultra pro. Neither are either of their smart generators.

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They are targeting home backup with the Ultra I think.

MtnXfreeride said:

At the time I was barefoot on the garage concrete

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Doh!
.
Amazing.

Put shoes on. Retest.

TomC4306 said:

Doh!
.
Amazing.

Put shoes on. Retest.

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Why is this worth retesting for touch safety? There is strong evidence of a ground fault that isn’t going through a path with proper fault detection.

On a listed AIO or hybrid there is supposed to be PV side ground fault detection

I'd say this is more common than people think. Ground is tied to neutral but neutral is not always at "ground" potential. There can be several volts and bare feet make it very easy to feel things. There is a test often performed by utilities where they measure the voltage between the ground wire coming down the pole to the wire on the next pole. If I experienced this I would drive a metal stake in the ground away from the house and pour some water on it because it wouldn't be driven deep. Then measure the voltage between that and the ground in the garage. I had a utility line to the house replaced and 6 months later my lights were flashing. At the fuse box my AC lines were unbalanced 30V. That is amazing because my ground connected to copper water lines to the street and this system was all metal in the neighborhood. The utility came out and found a bad crimp on the neutral at the entrance. I was in an industrial building and there was a cast iron sewer stack pipe. A piece of angle stock was against that and leaning on the building steel column. There were sparks shooting out of where they meet. So, you may have a house problem. Sinking a "bond" stake in the garage may be the solution. I'd first find the source of the problem.