Sounds like the best course of action would be to disconnect the BMK and AGS first if they are present. They are just a couple RJ45 plugs in the front of the Inverter.
Or even better. Disconnect the battery first before messing with the inverter,
Magnum tech support says you have to disconnect the positive conductor on the battery terminal first before disconnecting the negative conductor on the battery terminal. I explained that this has nothing to do with disconnecting the 12-volt wires on the inverter itself. I could never get them to clarify if their documentation was referring to the battery terminals or the inverter terminals.
Great suggestion Randy. That should work. It would then allow the neg(-) cable to be removed first.
Like many owners, I have a fuse in the positive battery cable (not a breaker). Removing that fuse is relatively difficult and more dangerous than removing the pos(+) cable from the battery or the inverter.
I hope that disconnecting the BMK and AGS first solves the issue.
Hi Mike, on the last paragraph Magnum engineers want $150 an hour to discuss what has become a serious situation! I'm thinking they should be grateful that you would be taking the time to discuss the situation & with all your knowledge & experience you should be charging the $150 an hour for the privilege of talking to you!
Hard to believe, but that’s what the help desk told me. If my discussion and article saves even one warranty replacement, they’re way ahead of the game.
Mike forget the warranty issues think about someone getting seriously hurt or even killed. I've not seen a battery blow up but I've seen the cables melt down when my friends starter got stuck, not a pretty site!
I totally get the argument to disconnect the negative terminal of a battery first (before removing it) to minimize the risk of shorting the positive terminal to chassis ground while disconnecting it, but I’ve always consider disconnecting the positive terminal of a device first because of the likelihood of inadvertently creating a spark by an inadvertent discharge of stored energy on the positive bus. As was recommended in Mike’s article, opening the circuit breaker or removing the in-line fuse (which is normally in series with the positive terminal) seems like the obvious and best first step in the process of removing a device or a battery. The next step, it seems to me, would depend on how much clearance (and risk of creating a short) there is in each particular situation. In RVs, we frequently see more than one battery present and I’ve seen them mounted in various kinds of boxes which are sometimes made of metal. Removing a device like an inverter isn’t the same thing as removing a battery. It is easy to imagine how there could be stored energy in internal capacitors as well as stray capacitances and the chance that the device was inadvertently left in the on state when disconnecting it. I can also imagine that an engineer in the company may have at one time done a study about how best to disconnect it and passed on results to their support team. The original engineer could have subsequently left the project or the company and all that remains is “corporate knowledge” without a source to go back to when questions come up. Mike, I hope you are able to get to the bottom of this one but it may not be possible. It’s a good reminder that we all need to be thoughtful and very careful when working with situations where stored energy may be present.
So, I haven't seen any newer posts on this topic, so they never got back to you?
As I understand things, if you don't have either of the above mentioned accessories, the disconnecting the negative first does not matter. I have only the ME-RVC module which connects all the info from the inverter to the central screen. This was apparently not mentioned as something to disconnect the positive first. Does that sound right?
I haven't seen any further info from Sensata/Magnum, so I assume they never got back to you?
On July 21, you wrote (in part):
"Here’s my feedback email from Magnum Engineering:"
~~~
“Normally, disconnecting the positive or negative first shouldn’t matter. There is an exception to this. If the ME-BMK is installed or an older generation ME-AGS is installed, then the positive must be disconnected first. The current AGS model doesn’t matter.
If the BMK is installed and the negative removed from the inverter first, the BMK will act as a Vbatt – (neg) return path. Eventually this will damage the control board and the BMK. This is why we suggest always disconnecting the Vbatt+ (pos) first.
Ideally, the user should be disconnecting the inline fuse or circuit break before removing the DC cables from the inverter. "
~~~
One thing that would be nice to know is, *how do we identify an older generation ME-AGS?*
That's important because anyone with a "current model" ME-AGS (and no BMK) can apparently disregard the instruction to disconnect the pos(+) first.
As for the advice: "Ideally, the user should be disconnecting the inline fuse [first]..." -- installations vary, but I doubt I am the only one with a fuse that is more potentially dangerous (and more difficult) to remove than the pos(+) battery cable.
Thanks for taking the time to look into this and write it up, Mike!
"If the BMK is installed and the negative removed from the inverter first, the BMK will act as a Vbatt – (neg) return path. Eventually this will damage the control board and the BMK. This is why we suggest always disconnecting the Vbatt+ (pos) first.
Ideally, the user should be disconnecting the inline fuse or circuit break before removing the DC cables from the inverter. "
It is outrageous that a mfr -- especially a respected one like Magnum -- would design a piece of equipment such that the pos(+) cable must be disconnected first.
Quote:
"I’m still waiting for Magnum engineering to contact me, but their help desk says I have to pay their engineers $150/hr to discuss."
Seriously?! I can understand that a company might not want randos calling and wasting their engineers' time -- but this is different. I assume they know that you (Mike) are an engineer yourself, and that you created the "No-Shock Zone" and have thousands of followers. And they still want to CHARGE you $150/hour?! That's outrageous, not to mention short-sighted.
If it helps, I was able to speak with a knowledgeable person at Sensata (for free) regarding programming the MS2000 charger for LiFePO4 batteries. He may have been a tech, not an engineer, but he knew the inverter.
Yeah, it does seem shortsighted. I did identify myself as an engineer and technology writer for RV owners with thousands of readers, as well as being a Level-3 RVTI instructor for RV Techs, but that didn’t help. I do have a business card from Sensata that I picked up at the RV Dealer Open House in Elkhart last year, so that will be my next call.
I understand the risk of putting a wrench to a hot terminal, but reasonable awareness should be enough to avoid shorting. I see exposed hot wires on batteries, cables, solar installations etc, in storage compartments that I feel are much greater dangers!
I should do an article on insulated tools for working on electrical systems. DC battery systems can produce huge fault currents if there’s an accidental short circuit.
Sounds like the best course of action would be to disconnect the BMK and AGS first if they are present. They are just a couple RJ45 plugs in the front of the Inverter.
Or even better. Disconnect the battery first before messing with the inverter,
Magnum tech support says you have to disconnect the positive conductor on the battery terminal first before disconnecting the negative conductor on the battery terminal. I explained that this has nothing to do with disconnecting the 12-volt wires on the inverter itself. I could never get them to clarify if their documentation was referring to the battery terminals or the inverter terminals.
Great suggestion Randy. That should work. It would then allow the neg(-) cable to be removed first.
Like many owners, I have a fuse in the positive battery cable (not a breaker). Removing that fuse is relatively difficult and more dangerous than removing the pos(+) cable from the battery or the inverter.
I hope that disconnecting the BMK and AGS first solves the issue.
That’s one of the questions I have for Magnum engineering. But I suspect you are correct…
Hi Mike, on the last paragraph Magnum engineers want $150 an hour to discuss what has become a serious situation! I'm thinking they should be grateful that you would be taking the time to discuss the situation & with all your knowledge & experience you should be charging the $150 an hour for the privilege of talking to you!
Thanks
Snoopy
Hard to believe, but that’s what the help desk told me. If my discussion and article saves even one warranty replacement, they’re way ahead of the game.
Mike forget the warranty issues think about someone getting seriously hurt or even killed. I've not seen a battery blow up but I've seen the cables melt down when my friends starter got stuck, not a pretty site!
Snoopy
I totally get the argument to disconnect the negative terminal of a battery first (before removing it) to minimize the risk of shorting the positive terminal to chassis ground while disconnecting it, but I’ve always consider disconnecting the positive terminal of a device first because of the likelihood of inadvertently creating a spark by an inadvertent discharge of stored energy on the positive bus. As was recommended in Mike’s article, opening the circuit breaker or removing the in-line fuse (which is normally in series with the positive terminal) seems like the obvious and best first step in the process of removing a device or a battery. The next step, it seems to me, would depend on how much clearance (and risk of creating a short) there is in each particular situation. In RVs, we frequently see more than one battery present and I’ve seen them mounted in various kinds of boxes which are sometimes made of metal. Removing a device like an inverter isn’t the same thing as removing a battery. It is easy to imagine how there could be stored energy in internal capacitors as well as stray capacitances and the chance that the device was inadvertently left in the on state when disconnecting it. I can also imagine that an engineer in the company may have at one time done a study about how best to disconnect it and passed on results to their support team. The original engineer could have subsequently left the project or the company and all that remains is “corporate knowledge” without a source to go back to when questions come up. Mike, I hope you are able to get to the bottom of this one but it may not be possible. It’s a good reminder that we all need to be thoughtful and very careful when working with situations where stored energy may be present.
So, I haven't seen any newer posts on this topic, so they never got back to you?
As I understand things, if you don't have either of the above mentioned accessories, the disconnecting the negative first does not matter. I have only the ME-RVC module which connects all the info from the inverter to the central screen. This was apparently not mentioned as something to disconnect the positive first. Does that sound right?
They refuse to let me talk to an engineer, and the help desk could only read me a troubleshooting chart, which was no help.
Hi Mike,
I haven't seen any further info from Sensata/Magnum, so I assume they never got back to you?
On July 21, you wrote (in part):
"Here’s my feedback email from Magnum Engineering:"
~~~
“Normally, disconnecting the positive or negative first shouldn’t matter. There is an exception to this. If the ME-BMK is installed or an older generation ME-AGS is installed, then the positive must be disconnected first. The current AGS model doesn’t matter.
If the BMK is installed and the negative removed from the inverter first, the BMK will act as a Vbatt – (neg) return path. Eventually this will damage the control board and the BMK. This is why we suggest always disconnecting the Vbatt+ (pos) first.
Ideally, the user should be disconnecting the inline fuse or circuit break before removing the DC cables from the inverter. "
~~~
One thing that would be nice to know is, *how do we identify an older generation ME-AGS?*
That's important because anyone with a "current model" ME-AGS (and no BMK) can apparently disregard the instruction to disconnect the pos(+) first.
As for the advice: "Ideally, the user should be disconnecting the inline fuse [first]..." -- installations vary, but I doubt I am the only one with a fuse that is more potentially dangerous (and more difficult) to remove than the pos(+) battery cable.
Thanks for taking the time to look into this and write it up, Mike!
From Magnum (included in your email Mike):
"If the BMK is installed and the negative removed from the inverter first, the BMK will act as a Vbatt – (neg) return path. Eventually this will damage the control board and the BMK. This is why we suggest always disconnecting the Vbatt+ (pos) first.
Ideally, the user should be disconnecting the inline fuse or circuit break before removing the DC cables from the inverter. "
It is outrageous that a mfr -- especially a respected one like Magnum -- would design a piece of equipment such that the pos(+) cable must be disconnected first.
Quote:
"I’m still waiting for Magnum engineering to contact me, but their help desk says I have to pay their engineers $150/hr to discuss."
Seriously?! I can understand that a company might not want randos calling and wasting their engineers' time -- but this is different. I assume they know that you (Mike) are an engineer yourself, and that you created the "No-Shock Zone" and have thousands of followers. And they still want to CHARGE you $150/hour?! That's outrageous, not to mention short-sighted.
If it helps, I was able to speak with a knowledgeable person at Sensata (for free) regarding programming the MS2000 charger for LiFePO4 batteries. He may have been a tech, not an engineer, but he knew the inverter.
Yeah, it does seem shortsighted. I did identify myself as an engineer and technology writer for RV owners with thousands of readers, as well as being a Level-3 RVTI instructor for RV Techs, but that didn’t help. I do have a business card from Sensata that I picked up at the RV Dealer Open House in Elkhart last year, so that will be my next call.
I understand the risk of putting a wrench to a hot terminal, but reasonable awareness should be enough to avoid shorting. I see exposed hot wires on batteries, cables, solar installations etc, in storage compartments that I feel are much greater dangers!
I should do an article on insulated tools for working on electrical systems. DC battery systems can produce huge fault currents if there’s an accidental short circuit.
I think I would enjoy watching you melt things!
My kids alway want to come by the lab when I plan to blow something up… 🤣🤣🤣