Anatomy of The DC/DC Converter

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ddoxey

Well-known member
Joined
Feb 20, 2017
Messages
60
I picked up a used DC/DC converter on ebay.
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Today I dissected it.
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Mounted to the sides are two circuit boards.
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This smaller board on the side holds two Bussmann FWP-40A14Fa diodes -- presumably the ones that burn out when the cabin heater craps out.

On a final note, here's a little connection diagram:
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Very cool. Sure looks serviceable to me... socketed and all.

Thanks for sharing this!
 
Today seemed like a good time to compare a broken (not powering the heater) DC/DC converter with a good one.

On the Left is the broken unit, and on the right is the good one.

lXqrT7B.png


I placed the ohmmeter on the +/- terminals of:
* the cabin heater power: 100kΩ is normal
* the battery coolant heater power: 0.4MΩ is normal
* the AC compressor power: 100kΩ is normal.

It looks like a slam dunk. If you're cabin heater power is an open circuit then you've got a fried diode in your DC/DC converter.
 
Can you move the image to a different image host? The image doesn't render for me. When I'm logged in with a Google ID, it shows the minus sign in a circle, whatever that icon is called. When I'm logged out, it shows the forum broken image icon.

Anyway, I would be very interested to see that the DC/DC can be repaired by just changing the diode. The only other thing is how to properly seal the case so it's water tight after repair.
 
TonyWilliams said:
I'm having a HELL of a time with that glued on cover. I must need a hammer ;-)

I initially approached it like baking open a headlight. But the adhesive is actually very tough, with a very high melting point and having the smell and consistency of inner tube rubber. The manufacturer must be pressing the enclosure cover on at a very high temperature.

I think the best approach is to use a square tip exacto blade and stab through the adhesive one blade width at a time. Be careful to avoid pentarating too deep near the connector pass-throughs.

I haven't reassembled one yet. My plan is to thoroughly remove the original adhesive and then apply a bead of the type of butyl glue used for sealing headlight enclosures. I would then apply clamps and the place it in an oven preheated to 260F for 20 min, just like resealing a headlight.

The butyl glue is not nearly as heat tolerant. But I doubt it gets up to 260F under the hood.
 
I'm just going to use "gasket maker" to reassemble. That is nutty how that is glued together, with no access to fuses.

My new fuses should arrive in the morning. Swing on by and check out our work! We will be installed a JdeMO both Friday and Saturday morning.

Quick Charge Power LLC
1780 La Costa Meadows Drive
Suite 104
San Marcos, CA 92078

Office 760-798-0342
M-F 9am to 5pm
 
Diodes typically fail shorted, and when I saw dox's measurements I became suspicious.

ddoxey said:


This smaller board on the side holds two Bussmann FWP-40A14Fa [edit by ALS: fuses] -- presumably the ones that burn out when the cabin heater craps out.

TonyWilliams said:
Awesome work. I'll be pulling one part next week, with a blown diode.

It's not a diode, it's a high-speed fuse, 40 ampere, used to protect more-sensitive semiconductor circuits.

http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/technical-literature/bus-ele-an-10507-hsf.pdf
[Mar2023: new URL: https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/fuses/bussmann-series-high-speed-fuses/bus-ele-an-10507-hsf.pdf , pg. 5]

Page 5:
Fuse_not_a_diode.png


Bussman said:
What is this symbol?
The term "semiconductor fuse" used for high speed fuses is misleading. Although high speed fuses often display a fuse and diode symbol on their label (like the one above), there is no semiconductor material in their construction. The symbol on their label is there solely to denote their application is for protecting "semiconductor" devices.

I presume that the failed heater causes a fuse in the DC converter to fail. When you both (Tony & dox) had it apart, was it just one, or both, that were open on your units?
 
ddoxey's Google Docs links are all dead.

The generic Toyota part No. for the RAV4 EV DC/DC Converter is G9270-0R011, according to TSB T-SB-0111-14. I posted that TSB as images in this thread.

The Toyota-branded DC/DC Converter may be the same part as Tesla 6009170 (or 1458271 for Refurb? (ie the fuse was replaced)), which is the Gen1 converter used on 2012-2013 Tesla Model S.

There are several on eBay ATM in the $350-$630 range (May2022: $250-$500). Some canned eBay searches:

DC-DC_Converter_03b.jpg
DC-DC_Converter_04b.jpg
DC-DC_Converter_Refurb_01b.jpg
DC-DC_Converter_Refurb_02b.jpg
DC-DC_Converter_12b.jpg
DC-DC_Converter_13b.jpg
DC-DC_Converter_13-1b.jpg
DC-DC_Converter_14b.jpg
 
ddoxey said:
Today seemed like a good time to compare a broken (not powering the heater) DC/DC converter with a good one.

On the Left is the broken unit, and on the right is the good one.

lXqrT7B.png


I placed the ohmmeter on the +/- terminals of:
* the cabin heater power: 100kΩ is normal
* the battery coolant heater power: 0.4MΩ is normal
* the AC compressor power: 100kΩ is normal.

It looks like a slam dunk. If you're cabin heater power is an open circuit then you've got a fried diode in your DC/DC converter.

Thank you for the Technical Analysis. Does the DC-DC Converter fail completely when it goes or can it be intermittent?
Thanks again,
 
The early Tesla Model S, and the RAV4EV that shares the same part, have a DC-DC Converter that is also the vehicle's High Voltage Junction Block (HVJB). As such, it doesn't just convert the HV ~400Vdc to ~14Vdc, it also routes HV to the A/C motor-compressor and the heater.

I guess to answer your question, I'd have to know "what's intermittent"?

The air-conditioning and heater should probably "just work", and if they stop working, I would expect they would continue to not work . . . if the issue involved is within the DC-DC Converter. One of those fuses opened, and fuses always open for a valid reason, they don't "get weak"*. In the Model S, where there are a whole lot more of these in service, lots of failed A/C compressors took out their fuse inside the DC-DC, and it sometimes took the service center a while to realize that they needed to replace the A/C motor-compressor assy. as well as the DC-DC on a repeat failure of the fuse.

The later Model S (starting around Jan2014 (ref.)) moved the HVJB to a separate location, which simplifies both diagnostics and service (and cost!) when either the A/C or the heater start frying fuses.

If your battery isn't staying charged, it's probably the battery, not the DC-DC.

If your battery is being overcharged . . . well, that's a feature, as has been documented :0 . The charge voltage that the DC-DC outputs is above what lead-acid batteries like for hours on end. It's hard on the battery when you go on very long drives or use your RAV4EV to drive a standalone 12Vdc->120Vdc inverter during a home power outage.

[Sep2023: I've come around to the notion that the particular Ferraz Shawmut (now Mersen) semiconductor fuses that Tesla spec'd for the first two years of production may have fuses that fail for no readily apparent reason; there are several documented instances where a single failed fuse of a pair was replaced, and subsequently the other fuse failed within two years. This pattern seems concentrated on the GEN1 OBC AC input fuses, and this early GEN1 DC-DC Converter. Further reading here.]
 
asavage said:
The early Tesla Model S, and the RAV4EV that shares the same part, have a DC-DC Converter that is also the vehicle's High Voltage Junction Block (HVJB). As such, it doesn't just convert the HV ~400Vdc to ~14Vdc, it also routes HV to the A/C motor-compressor and the heater.

I guess to answer your question, I'd have to know "what's intermittent"?

The air-conditioning and heater should probably "just work", and if they stop working, I would expect they would continue to not work . . . if the issue involved is within the DC-DC Converter. One of those fuses opened, and fuses always open for a valid reason, they don't "get weak". In the Model S, where there are a whole lot more of these in service, lots of failed A/C compressors took out their fuse inside the DC-DC, and it sometimes took the service center a while to realize that they needed to replace the A/C motor-compressor assy. as well as the DC-DC on a repeat
failure of the fuse.

The (post-facelift, 2015?) later Model S moved the HVJB to a separate location, which simplifies both diagnostics and service (and cost!) when either the A/C or the heater start frying fuses.

If your battery isn't staying charged, it's probably the battery, not the DC-DC.

If your battery is being overcharged . . . well, that's a feature, as has been documented :0 . The charge voltage that the DC-DC outputs is above what lead-acid batteries like for hours on end. It's hard on the battery when you go on very long drives or use your RAV4EV to drive a standalone 12Vdc->120Vdc inverter during a home power outage.

The failure mode is that it would go into to "Neutral" during hard acceleration onto a freeway onramp. A Jumper Box would get it back into a drivable mode but the "Service Vehicle Immediately" message was displayed with the ! in a Triangle also illuminated. Charging the 12V Battery at home had no positive effect.
However, it was still drivable for about 30 miles when I drove it to the Dealer. The Dealer (Crown Toyota) confirmed the problem as it happened to them on their test drive. Their Tech replaced the Battery and says the DC-DC Converter has failed ($3,400 plus Labor because the Platinum Warranty has expired). This same issue occurred in January (when the Platinum Warranty was still valid) when another dealer (Findlay Toyota) just replaced the Battery and it ran fine for 8 months. This is why I am asking if the DC-DC Converter could have been intermittent (or Walking wounded) since January.
Thank you for sharing your knowledge and experience.

UPDATE 6 WEEKS LATER: the Technician at Crown Toyota replaced the DC to DC Converter which did not remedy the fault. They told me that this resulted in a "new" Trouble Code which indicated the Traction Battery needs replacement. I have filed a claim with Toyota's Platinum Warranty services as the RAV is now beyond the Battery's 8 year warranty.

This saga continues.

Rich
 
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