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[MVetter]

Ye gods! So the original OBC is using the battery as a heat sink. Now you've stacked another onto it which is ... using the original OBC as a heat sink.

I wish you luck but I think this setup is not long for this world

[TheRan]

Does the original charger actually touch the battery? I didn't unmount it completely but it doesn't seem like it would. Also on the 7.2 only half of it would be touching the battery, the other half would be touching the storage compartment. I did look up the specs for the charger and they say the thermal limit is 80°C external, which I assume means the outside case temp. Putting my hand on the lower charger after an hour or so of charging it certainly wasn't anywhere near that, I haven't measured it yet but it's not uncomfortable to keep in contact with it so I'd say between 30 and 40.

My ideal plan would be to add a heatsink between the two chargers (I've had a look and found some that would cover enough area) and then another below, although I haven't left enough length on the threaded rods for that so I'd need to buy some more and it means having the skid plate mounted even lower down. I might have a look at adding heatsinks along the sides of the cases. I've also considered adding some small fans at the front but I sometimes ride through deep water.

[MVetter]

Yes it touches the battery. It is using the battery as a heat sink. The thing gets HOT.

[Specter]

If you can't / don't want to fiddle around buying new heat sinks online, you can usually get them very cheap in pawn shops /junk yards etc.  Look for old stereo amps people are getting rid of /junking and take them out of those.  Ive gotten some pretty massive beefcake heatsinks that way for verious projects.  CPU's have them too but they are rather small.

Old power supplies for CEMS equipment / Tube / Hydrogen / Helium lasers also have huge sinks in them too.

Aaron

[TheRan]

Yes it touches the battery. It is using the battery as a heat sink. The thing gets HOT.

I see. Does the top (mounting tab side) get hotter than the rest of the casing then? I know they're all potted inside so assumed it would be fairly consistent. If that's the case then it would make more sense for me to have the heatsink between the two chargers thermally adhered to the lower one. I was also considering swapping the control connectors and having the lower as the primary (for when charging with just one, so it will do so with the bike keyed off) so that it's getting rid of most of its heat to the air, but it would seem that the upper one is going to have the better heatsinking to the battery case.

[MVetter]

Yes, the battery side is what I call the hot side. You wouldn't want to touch it. In a perfect world you'd just chuck the thing entirely and stash a smaller, but more powerful and less crappy, charger unit in the pocket stash area. But that's not a simple task for the average person.

[TheRan]

Yeah when I first got the bike I considered putting something in the storage compartment area (I think I measured up that a Delta would fit there with the mounting tabs cut off) but over time I've come to appreciate that extra storage. Then I wanted a charge tank but it's like two grand and no nearby dealers would get back to me. A nice "plug and play" setup like the Diginows would be ideal, no loss of storage, but that's never happening, and I don't feel like going through the hassle of custom ordering some chargers.

I do have a 12v temperature probe from an old computer laying about somewhere, I could slip that in-between the chargers to get an idea of how bad things are. I may have enough cable to play with that I could flip the lower charger so the hot side is open to the air.

[MVetter]

For what it's worth I have been told that the Charge Tank is plug and play, and doesn't necessarily need a dealership. At least that's what Harlan at Hollywood Electrics (RIP) told me.

[TheRan]

So I did a little temperature test, although hardly conclusive as I'll get to.

Around 1.5 hours charging at 2500W to start and then it had risen to 2800W towards the end, think I started off around 40% SoC. Ambient temperature was just under 20°C so actually fairly warm for here in the UK (surprisingly so at this time of year and at about 8pm). I managed to find a little bit of space on the top surface of each charger towards the rear (cable end), not the ideal position but I figured the entire plate would probably end up close to the same temperature over enough time. The final reading ended up being 40°C on the top charger and 43°C on the bottom. A few surprises here, I expected the top to get hotter, I would have thought the difference would be bigger, and I expected a much higher temperature.

Putting my finger right next to the temperature probe it didn't seem that hot however putting my hand on the underside of the bottom charger it felt much hotter so I decided to move the probe to that position and as I expected it was 53°C, and the side of the upper charger was at 51°C. This tells me that my positioning of the probes on the top surface wasn't an accurate measurement.

I'm not sure how to test it further from here. I could loosen off the nuts to create enough space between the chargers and the upper charger and the battery to slip the probes in and get them to the centre of the top surface, but by doing so I get rid of the heatsinking that the contact would provide. I suppose I could maybe slacken it all off and then hold it together with a strap, then at the end of charging quickly release it and slip the probes in there. It's just trying to get enough pressure to ensure decent thermal contact (I don't have any ratchet straps) and trying to be quick enough while juggling everything so it doesn't cool off too much so I still get an accurate measurement.

[MVetter]

Do you not have one of those temperature laser guns?

[TheRan]

I do have one somewhere, as well as a Flir I can plug into my phone. I wanted to go with the thermocouples as they're more accurate, some electrical tape on a surface can give a fairly decent non-contact temp reading but I'm not getting my hands between the chargers to apply some without removing them completely.

[Specter]

Instead of a thermocouple, you can use just the TC wire.  K is the most common.  Very small, just twist the ends together and shove where you want it, fits in tight places a LOT better than a TC and a lot cheaper to get as well.  You can get the plugs to fit your  meter side very cheap as well, or really, just shove the other ends of the wires into the respective holes.

Being the wire is very small, it's response is very fast, you don't have to wait for the whole shell holding it to heat up  and if you have to run the wire places to keep it out of the way it fits very nicely in tight places.

Aaron

[TheRan]

I'm using just a bare thermocouple as you describe, not one of those rod type ones. I'm not sure if there's a specific term to describe the type I'm using. I could easily slip them between the chargers and the top charger and battery, my worry is that tightening down the mounting bolts would just crush and damage them.

[Specter]

You'd have to torque the piss out of the wires to crush them,  They should be fine.  As long as they got good contact with each other they should be fine.   If you are worried about other metals getting into the conduction path, put a dab of tape or something around them.

The TC designation,  K, R, S, etc is the wire that is used to make the junction.  The different types are good for different temp ranges and environments.  K is cheap and the most common. 

K- is Chromel, Alumel wire and is pretty sturdy and able to stand up to high temps and a lot of nasty places, like motors, engines etc.

  Typically it's yellow wire /red wire and in a yellow jacket,  or braided sheath.
Aaron