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Old 08-05-2017, 04:13 PM   #1 (permalink)
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Default Replacing the MSD Fuse to increase performance

Quote:
Originally Posted by Fabulist View Post
My $0.02 on this article:

The author seems to be too preoccupied with looking good in the photos to be taken particularly seriously, using the Revero more as a prop or background. But she is not entirely wrong. The Karma was a revolutionary vehicle in 2008, but there is nothing particularly remarkable about it today. I still love driving my Karma and drive it as often as I can, but the serial hybrid drivetrain is not exactly state of the art in 2018, and definitely not at $130K. Offering a slightly updated 2008 car in 2018 for $130K is a tough sell.

And KA's executives are not doing themselves any favors with the "this car is not for you" campaign and the absurdly long list of people or uses this car is NOT for, and just from personal experience, it is wrong. I have made plenty of airport runs in my Karma, it has been my daily driver and commute car since I bought it, and I have even gone on a couple of long trips in it, and it works perfectly fine in all of those roles, and with my TOM and upgraded MSD fuse, it is plenty quick. I am not sure where KA got the idea that telling people that they are not good enough to buy your car would sell a lot of cars, I think most people would simply accept KA's judgment and move on to something else.


btw, what is "MSD fuse" -- first i heard of it -- I have the TOM and love it, but not the MSD fuse ??
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Old 08-05-2017, 07:29 PM   #2 (permalink)
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btw, what is "MSD fuse" -- first i heard of it -- I have the TOM and love it, but not the MSD fuse ??
The Manual Service Disconnect is a safety device used to isolate the HV battery. It's a big orange plug under the passenger seat on the driver's side. See this post and linked document.

Inside the MSD, there is a fuse that restricts the amount of power that can be drawn from the battery. The factory fuse is limited to 350A which is wildly undersized. The fuse can be safely upgraded to a 630A fuse to allow more power to be drawn out of the battery without blowing the fuse. Combined with the TOM, it puts an additional pep in the Karma's step. This is a fairly inexpensive upgrade, as a new MSD costs less than $100 and the upgraded fuse can be had for another $50. I kept my old MSD as a spare in case the new one dies at an inopportune moment.
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Old 08-06-2017, 12:44 AM   #3 (permalink)
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Originally Posted by Fabulist View Post
The Manual Service Disconnect is a safety device used to isolate the HV battery. It's a big orange plug under the passenger seat on the driver's side. See this post and linked document.

Inside the MSD, there is a fuse that restricts the amount of power that can be drawn from the battery. The factory fuse is limited to 350A which is wildly undersized. The fuse can be safely upgraded to a 630A fuse to allow more power to be drawn out of the battery without blowing the fuse. Combined with the TOM, it puts an additional pep in the Karma's step. This is a fairly inexpensive upgrade, as a new MSD costs less than $100 and the upgraded fuse can be had for another $50. I kept my old MSD as a spare in case the new one dies at an inopportune moment.
did you do it yourself or who did it for you and at what cost?
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Old 08-06-2017, 04:12 PM   #4 (permalink)
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Uh... yeah Fab, I think we need a new thread and some specifics on this MSD thing, including a link or description of where to buy it, whether you did-it-yourself (you know: electrocution risk level and such).

I didn't see it the first time around because it was buried in a discussion about RDM, and I suspect it will be equally difficult to find in this discussion about the Revero review, but I'm very interested in hearing more.
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Old 08-07-2017, 02:59 PM   #5 (permalink)
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Originally Posted by non sequitur View Post
Uh... yeah Fab, I think we need a new thread and some specifics on this MSD thing, including a link or description of where to buy it, whether you did-it-yourself (you know: electrocution risk level and such).

I didn't see it the first time around because it was buried in a discussion about RDM, and I suspect it will be equally difficult to find in this discussion about the Revero review, but I'm very interested in hearing more.
Fair point; did not mean to hijack the thread, just making a point about the Revero's extra performance vs. The Karma. If there is interest in further discussion, please start a new thread and I will be happy to respond.
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Old 08-07-2017, 03:23 PM   #6 (permalink)
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Default Replacing the MSD Fuse to increase performance

In a recent thread [https://www.fiskerbuzz.com/forums/13-...46-sad-3.html]], it emerged that it may be possible to increase the performance of a 2012 Fisker Karma by replacing a fuse in the "Manual Service Disconnect" (or "MSD"): a safety device used to isolate the HV battery, described as "a big orange plug under the passenger seat on the driver's side."

From Fabulist's post in the above link:
"Inside the MSD, there is a fuse that restricts the amount of power that can be drawn from the battery. The factory fuse is limited to 350A which is wildly undersized. The fuse can be safely upgraded to a 630A fuse to allow more power to be drawn out of the battery without blowing the fuse. Combined with the TOM, it puts an additional pep in the Karma's step. This is a fairly inexpensive upgrade, as a new MSD costs less than $100 and the upgraded fuse can be had for another $50. I kept my old MSD as a spare in case the new one dies at an inopportune moment."

This is exactly the kind of info that makes this board so valuable to 2012 owners, so let's hear from anyone who has done this upgrade:
-where did you purchase the fuse, and for how much (link please)?
-what was your experience as far as ease of replacement?
-any downsides to doing this? (any risk to weigh against the reward?)
-what differences/improvements did you notice as a result of the fix?

Fire away!
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Old 08-07-2017, 04:28 PM   #7 (permalink)
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Quote:
Originally Posted by non sequitur View Post
In a recent thread [https://www.fiskerbuzz.com/forums/13-...46-sad-3.html]], it emerged that it may be possible to increase the performance of a 2012 Fisker Karma by replacing a fuse in the "Manual Service Disconnect" (or "MSD"): a safety device used to isolate the HV battery, described as "a big orange plug under the passenger seat on the driver's side."

From Fabulist's post in the above link:
"Inside the MSD, there is a fuse that restricts the amount of power that can be drawn from the battery. The factory fuse is limited to 350A which is wildly undersized. The fuse can be safely upgraded to a 630A fuse to allow more power to be drawn out of the battery without blowing the fuse. Combined with the TOM, it puts an additional pep in the Karma's step. This is a fairly inexpensive upgrade, as a new MSD costs less than $100 and the upgraded fuse can be had for another $50. I kept my old MSD as a spare in case the new one dies at an inopportune moment."

This is exactly the kind of info that makes this board so valuable to 2012 owners, so let's hear from anyone who has done this upgrade:
-where did you purchase the fuse, and for how much (link please)?
-what was your experience as far as ease of replacement?
-any downsides to doing this? (any risk to weigh against the reward?)
-what differences/improvements did you notice as a result of the fix?

Fire away!
Some clarification: To get the best results from this fix, you need to have a TOM module that increases to top limit of power output from the inverters. But even without a TOM this upgrade is helpful in a very important way. Because the current fuse is undersized for the power flow, even without a TOM power upgrade, it is possible to blow the fuse by demanding a lot of power from a standard Karma (for example by accelerating hard onto a on ramp or going uphill), and when the fuse blows, the car will not go into "Start" mode until you can get a replacement MSD, and it's basically bricked. Needless to say, this never happens at a convenient location or when you have access to a spare MSD. Since the MSD is readily available, and fairly cheap (<$100) it makes sense to buy and carry a spare with you, irrespective of the performance gains. Even if you don't plan to upgrade the fuse, it is worth the small expense to buy a spare MSD and keep it in the car with you.

Disclaimer Regarding Upgrading the Fuse: Do this at your own risk. I am just telling you about what I have done and I claim no responsibility for any damage or issue arising from anyone using this information. I am not advising anyone to upgrade the fuse, that's entirely your own decision. If you have any concerns about this, do not do it. YMMV

-where did you purchase the fuse, and for how much (link please)?

I purchased the fuse on E-Bay. The price tends to vary depending on availability. I paid $40 for mine.

This is a photo of the standard fuse in a stock MSD



Note that it is limited to 350A.

Here is a photo of the upgraded fuse:



Note that it is the same brand, just rated at 630A instead of 350A.

-what was your experience as far as ease of replacement?

Replacing the old MSD with the upgraded one is a piece of cake. Replacing the fuse inside the MSD is tricky, however, because the fuse in the MSD was not designed to be replaced. I did not want to break the MSD while trying to release the small plastic tabs to extract the old fuse, and got help from a friend who is handy with this sort of thing. YMMV. I also keep the original MSD as spare in the car.

-any downsides to doing this? (any risk to weigh against the reward?)

See disclaimer above. Also, whenever you put in a higher rated fuse in an electrical circuit, you are risking damaging downstream components. I have not had any issues since I upgraded mine, but that does not mean that there is no risk. Another minor downside is that by drawing more power from the battery, you are reducing your range, which in the case of the Karma, is not exactly stellar to begin with, but I am OK with having more power at my disposal in exchange for a few miles reduction in overall EV range.

-what differences/improvements did you notice as a result of the fix?

I have not had the opportunity to do a data collection run with Dynolicious, but the car definitely feels faster. I don't know how much of the extra umph is attributable to the TOM vs. the MSD, but the car definitely has more zip than it did before.
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Last edited by Fabulist; 08-07-2017 at 04:57 PM.
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Old 08-07-2017, 08:51 PM   #8 (permalink)
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Originally Posted by Fabulist View Post
Some clarification:Some clarification: To get the best results from this fix, you need to have a TOM module that increases to top limit of power output from the inverters. But even without a TOM this upgrade is helpful in a very important way. Because the current fuse is undersized for the power flow, even without a TOM power upgrade, it is possible to blow the fuse by demanding a lot of power from a standard Karma (for example by accelerating hard onto a on ramp or going uphill), and when the fuse blows, the car will not go into "Start" mode until you can get a replacement MSD, and it's basically bricked. Needless to say, this never happens at a convenient location or when you have access to a spare MSD. Since the MSD is readily available, and fairly cheap (<$100) it makes sense to buy and carry a spare with you, irrespective of the performance gains. Even if you don't plan to upgrade the fuse, it is worth the small expense to buy a spare MSD and keep it in the car with you.
so are you saying the fuse can actually blow and the car will have bricked symptoms ?

also can we can some clarification on "exactly" one needs to do -- i read the description, but i'm to dense to understand without some pictures -- thanks
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Old 08-07-2017, 09:11 PM   #9 (permalink)
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so are you saying the fuse can actually blow and the car will have bricked symptoms ?
Yes, the whole point of a fuse is to protect the circuit by blowing when the rated current is exceeded. My understanding is that the original 350A fuses do tend to blow under hard acceleration or power demand. It is less likely for the 630A fuse to blow, but it may happen. If this happens, the car will not go into "Start" mode until you install an MSD with a new fuse, which is why it is smart to carry a spare MSD, even if you do not upgrade the fuse.

Quote:
Originally Posted by Nin ja View Post
also can we can some clarification on "exactly" one needs to do -- i read the description, but i'm to dense to understand without some pictures -- thanks
The steps are:

1 Acquire a second MSD (either new or one with a blown fuse);
2 Acquire 630A Fuse;
3 Remove 350A fuse from MSD;
4 Install 640A Fuse in place of 350A fuse;
5 Remove existing MSD and store in vehicle;
6 install MSD with 630A fuse; and
7 profit!

Steps 3 and 4 are the tricky ones because the MSD is not designed to be repaired, but it is possible to carefully unhook a couple of plastic tabs and remove the internal assembly. Here is the schematic of the MSD:



Like I said, I asked a friend of mine who is more deft at this sort of thing to safely remove the existing fuse without damaging the MSD. Installing the new fuse and reassembling the MSD is pretty easy from that point on.
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Old 08-07-2017, 10:22 PM   #10 (permalink)
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Originally Posted by Fabulist View Post


3 Remove 350A fuse from MSD;

this is the part i would like to know more, where is the fuse -- i read from your other post that it's under the driver side seat? if so, do you have to take out the seat or is it accessable ?? this is the part that i'm stuck on ;-)

thanks in advance
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