Help! Newbie almost blows a hole in his face with MPP 3KVA 24V

[Gertie]

I built my 24 V battery from 16 x 3.2 V 90AH Littokola batteries . It tested at 25.9 v. Then I plugged the DC cable into the bottom of my new MPP unit. You can't mistake polarity on these new ones the cable only goes in one way with red plugging into red and black plugging into black. Next I attached the black cable from the MPP to the negative terminal on my battery and then took the red cable and touched the positive terminal ... that's when a lightening bolt shot a piece of shrapnel at my face.
I retested the battery and I definitely have polarity correct.

So I retested the MPP and it seems the red is negative and black is positive. How is this possible? Has anyone else had this happen from MPP? What do I do next?

 

[Supervstech]

Can you post a picture of the cables and connections?
A spark is normal, and it is why a precharge resistor is recommended.
Shrapnel is NOT normal, and you need to be certain polarity is marked.
Electricity doesn't care what color the insulation is.

 

[Zwy]

I built my 24 V battery from 16 x 3.2 V 90AH Littokola batteries . It tested at 25.9 v. Then I plugged the DC cable into the bottom of my new MPP unit. You can't mistake polarity on these new ones the cable only goes in one way with red plugging into red and black plugging into black. Next I attached the black cable from the MPP to the negative terminal on my battery and then took the red cable and touched the positive terminal ... that's when a lightening bolt shot a piece of shrapnel at my face.
I retested the battery and I definitely have polarity correct.

So I retested the MPP and it seems the red is negative and black is positive. How is this possible? Has anyone else had this happen from MPP? What do I do next?

Pictures please

 

[Gertie]

1. I'm holding my multimeter leads to the MPP and you can see that the polarity is reverse.
2. you can see the chunk blown out of the positive lead.
3. This connection port must be new from MPP because I haven't seen it in any of the videos. But obviously red goes to red and black goes to black, it won't fit any other way.
4. This is my battery with the negative lead on the lower left and positive on the lower right (where MPP positive lead blew up.)

 

[Gertie]

Okay I got off the phone with the guy who runs Watts247 and he walked me through diagnosing it and yes mine was wired backwards internally from the factory. It seems to be working fine as long as I remember that red is negative and black is positive. WARNING to all who purchase a new inverter/charger from MPP--Don't rely on the color of the wires, check polarity first!

 

[markcm]

Okay I got off the phone with the guy who runs Watts247 and he walked me through diagnosing it and yes mine was wired backwards internally from the factory. It seems to be working fine as long as I remember that red is negative and black is positive. WARNING to all who purchase a new inverter/charger from MPP--Don't rely on the color of the wires, check polarity first!

So they told you "oh sorry about that" and left it at that?

I had heard that some MPPT type controllers should be connected to the battery before the solar panels are connected but, reverse polarity due to incorrect internal wiring is just bad QA, I am surprised and not impressed that they didn't offer to correct this for you.

Thanks for reporting/sharing, while most of us would assume the the same that polarity is as marked this proves there is still risk with this much stored energy and a DMM check is good practice.

 

[Supervstech]

I would insist they send you a replacement cable, and unit, as the unit is now questionable reliability.
Reverse polarity can damage parts internally.
Best to be safe...

I retract the recommendation after seeing it was user error...

 

[Bud Martin]

Help! Newbie almost blows a hole in his face with MPP 3KVA 24V

I built my 24 V battery from 16 x 3.2 V 90AH Littokola batteries . It tested at 25.9 v. Then I plugged the DC cable into the bottom of my new MPP unit. You can't mistake polarity on these new ones the cable only goes in one way with red plugging into red and black plugging into black. Next I...

diysolarforum.com

Look at the readout of your meter, it shows NEGATIVE 26.3V, it looks like you have your meter probes in the reverse sockets.

 

[Supervstech]

Help! Newbie almost blows a hole in his face with MPP 3KVA 24V

I built my 24 V battery from 16 x 3.2 V 90AH Littokola batteries . It tested at 25.9 v. Then I plugged the DC cable into the bottom of my new MPP unit. You can't mistake polarity on these new ones the cable only goes in one way with red plugging into red and black plugging into black. Next I...

diysolarforum.com

Look at the readout of your meter, it shows NEGATIVE 26.3V, it looks like you have your meter probes in the reverse sockets.

Yes... his red meter lead is on he positive cable connected to the positive connection, and the meter is showing negative, indicating reverse polarity.

the unit is poorly designed, and QC let it slip out reversed.

 

[Bud Martin]

Yes... his red meter lead is on he positive cable connected to the positive connection, and the meter is showing negative, indicating reverse polarity.

the unit is poorly designed, and QC let it slip out reversed.

"1. I'm holding my multimeter leads to the MPP and you can see that the polarity is reverse." That is due to meter probes cables are in the wrong socket of the meter.

 

[RStone13]

I think you said you were connecting battery to Mpp. Correct? The picture shows PV inputs not battery inputs.

 

[Zwy]

Help! Newbie almost blows a hole in his face with MPP 3KVA 24V

I built my 24 V battery from 16 x 3.2 V 90AH Littokola batteries . It tested at 25.9 v. Then I plugged the DC cable into the bottom of my new MPP unit. You can't mistake polarity on these new ones the cable only goes in one way with red plugging into red and black plugging into black. Next I...

diysolarforum.com

Look at the readout of your meter, it shows NEGATIVE 26.3V, it looks like you have your meter probes in the reverse sockets.

It looks that way to me also, I opened the photo in another tab in order to enlarge it and red lead is plugged into COM port on multimeter.

Then I looked at his bank and just went out to the shop and looked at my cells, the black base terminals are positive and light colored terminals are negative. His multimeter reading shows positive polarity but that is because he has it all backwards.

 

[Zwy]

1. I'm holding my multimeter leads to the MPP and you can see that the polarity is reverse.
2. you can see the chunk blown out of the positive lead.
3. This connection port must be new from MPP because I haven't seen it in any of the videos. But obviously red goes to red and black goes to black, it won't fit any other way.
4. This is my battery with the negative lead on the lower left and positive on the lower right (where MPP positive lead blew up.)

You have your multimeter leads hooked up backwards, the black lead belongs in the COM port.

 

[Supervstech]

You guys are correct...
I bet his battery is doing the same thing...

 

[Bud Martin]

It looks that way to me also, I opened the photo in another tab in order to enlarge it and red lead is plugged into COM port on multimeter.

Then I looked at his bank and just went out to the shop and looked at my cells, the black base terminals are positive and light colored terminals are negative. His multimeter reading shows positive polarity but that is because he has it all backwards.

Yep, it looks like he assumes that the Black terminal of the battery is Negative.

 

[Zwy]

You guys are correct...
I bet his battery is doing the same thing...

He is very fortunate he didn't let some severe smoke out of something........... he needs to correct his mistake all around, get his leads and cables where they belong before something nasty does happen.

 

[Bud Martin]

He sure is lucky.
He also need to check his BMS connections! and hope that the BMS is still OK.

 

[Zwy]

I think you said you were connecting battery to Mpp. Correct? The picture shows PV inputs not battery inputs.

Look below PV and it shows DC input. Sure seemed strange to me. My Growatt has lugs, not sure on the MPP

 

[Zwy]

He also need to check his BMS connections!

Yes, definitely. This could get expensive in a hurry.

 

[MisterSandals]

it looks like you have your meter probes in the reverse sockets.

You have your multimeter leads hooked up backwards, the black lead belongs in the COM port

Exactly!