jray3
Posts: 1585
Joined: Tue Dec 06, 2011 1:05 am
Location: Tacoma area, WA
Contact: Website

Supplemental cooling for the charger.

Wed Jul 11, 2018 1:02 pm

After the charger failure, I'm keeping a closer eye on the new one and have been reminded that after several hours of charging, the top cover is extremely hot to the touch (actual temperatures coming soon), much warmer than the outbound coolant line. My pump is running and there is vigorous circulation, but of course, that heat exchanger is in the bottom of the box where it can't do the most good. Since the little filter box on top of the charger is in firm contact with the sound insulation on the underside of the motor room hatch, it has little chance to cool off.
For how much heat we're dealing with, at 96% assumed charger efficiency, 4% of 3300W= 132W or 640 Watt-hours per full recharge.
Throw in the DC-DC operation and I'd bet we're dealing with as much as 1 kWh of waste heat. To remove just 0.5 kWh of heat we'd need to soak up 1706 Btu.

SO, I'm considering the following unprioritized list of options.
#1- Remove some insulation to create an air gap above the charger. (and then likely add Dynamat to offset any increased noise)
#2- Add a ducted fan fed by the charger AC input to blow cool air across the top of the charger or pull hot air away.
#3- Add a liquid-cooled cold plate atop the charger and plumb it into the coolant loop.
(here's a candidate https://www.shopaavid.com/Product/416401U00000G Once could alternatively make a copper coil or use a tiny radiator designed for computer overclocking. I also a tiny heater core that serves to preheat winter combustion air in a Honda Odyssey.
#4- Add a bladder full of phase-change wax to serve as a heat sink atop the charger. Paraffin with a phase change at 84 degrees F will absorb 87 Btu/lb in the melting process. So, a whopping 20lbs of wax would be needed to reduce the heat by half, and not help at all on a warm summer day... wow. no go there
#5- Cut a hole in the motor room hatch and put a butterfly vent in so that the hot air rises into the cabin. Free heat in winter, but less effective in summer when needed most. https://www.etrailer.com/Enclosed-Trailer-Parts/Redline/371800.html?feed=npn&gclid=EAIaIQobChMItfjtpeqX3AIVGMRkCh3JYQoxEAQYASABEgLEK_D_BwE
#6- prop open the motor room hatch during recharging and open the windows a crack...

Comments please. Is any of this worthwhile, or is a charger replacement every 50-90k just to be expected?
2012 i-SE "MR BEAN" 96,000 miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh
1965 Karmann Ghia Cabriolet

Aerowhatt
Gold Member
Posts: 434
Joined: Wed Jan 28, 2015 1:52 pm

Re: Supplemental cooling for the charger.

Thu Jul 12, 2018 6:05 am

jray3 wrote:SO, I'm considering the following unprioritized list of options.
#1- Remove some insulation to create an air gap above the charger. (and then likely add Dynamat to offset any increased noise)
#2- Add a ducted fan fed by the charger AC input to blow cool air across the top of the charger or pull hot air away.
#3- Add a liquid-cooled cold plate atop the charger and plumb it into the coolant loop.
(here's a candidate https://www.shopaavid.com/Product/416401U00000G Once could alternatively make a copper coil or use a tiny radiator designed for computer overclocking. I also a tiny heater core that serves to preheat winter combustion air in a Honda Odyssey.
#4- Add a bladder full of phase-change wax to serve as a heat sink atop the charger. Paraffin with a phase change at 84 degrees F will absorb 87 Btu/lb in the melting process. So, a whopping 20lbs of wax would be needed to reduce the heat by half, and not help at all on a warm summer day... wow. no go there
#5- Cut a hole in the motor room hatch and put a butterfly vent in so that the hot air rises into the cabin. Free heat in winter, but less effective in summer when needed most. https://www.etrailer.com/Enclosed-Trailer-Parts/Redline/371800.html?feed=npn&gclid=EAIaIQobChMItfjtpeqX3AIVGMRkCh3JYQoxEAQYASABEgLEK_D_BwE
#6- prop open the motor room hatch during recharging and open the windows a crack...

Comments please. Is any of this worthwhile, or is a charger replacement every 50-90k just to be expected?


I have a long history with air cooling components on EVs. The Charger is a perfect candidate because it sits high in the bay where heat rises and becomes trapped. While the car is moving there is plenty of airflow, but when parked there would be very little. A finned heat sink on the cover plate. With a Nidec blower situated such that it gives good flow across the heatsink and creates enough turbulence it the compartment to not be recirculating hot air over and over would do the trick nicely IMO.

Aerowhatt
2014 cool silver ES, acquired new 4/2015 (42.7ah at ~26K miles)
2014 Labrador Black Pearl ES, acquired new 3/2016 (41.5ah at ~15k miles)

mikedufty
Posts: 29
Joined: Tue Apr 05, 2016 1:04 am
Location: Western Australia

Re: Supplemental cooling for the charger.

Thu Jul 12, 2018 8:07 am

According to wikipedia over 30,000 i-MiEVs have been sold. I think if there was a fundamental design fault with the charger that required more cooling, you would be seeing more reports of failures than we are.

I suspect you would be very unlucky to have two fail.

Don
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Joined: Thu May 10, 2012 3:55 pm
Location: Biloxi MS

Re: Supplemental cooling for the charger.

Thu Jul 12, 2018 4:40 pm

jray3 wrote:Comments please. Is any of this worthwhile, or is a charger replacement every 50-90k just to be expected?
I guess if you're always in need of a quick turnaround, your 3300 watt figure just can't be avoided - But, if not, recharging L1 at 12 amps (1440 watts) will cut your waste heat by more than half and it's a completely free option, costing you nothing and no mods needed. Also, our L2 EVSE is set limited to 12 amps, so we have never once used the full 3300 watts the charger is capable of. Quite probably, 2,880 watts is much less of a strain than the full 3300 watts is. Also, I never plug in to recharge until the car has been sitting, cooling off for at least a couple hours, usually longer

On our '17 Chevy Volt, I have the EVSE set to just 8 amps at 240 volts - Once I park it to charge, I never need to drive it again before the next day, so why push things??

We have always used L1 more often than L2 since we bought the first car more than 6 years ago. We never plug in L2 overnight because there's just no need - The car will be full in the morning no matter which you use and when we don't need a bunch of amps in a hurry, L1 is the obvious choice for us. A very large percentage of the time, we don't recharge to full anyway and 4 or 5 hours of L1 is easier to manage (for us anyway) than 2 or 3 hours of L2. - If we plug in L2 and forget about it, the car usually gets a full recharge when we really only wanted 75 or 80%.
When one car is already using the L1 EVSE, we sometimes use L2 for the other car, but usually just for an hour or two and not to fully recharge it

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

jray3
Posts: 1585
Joined: Tue Dec 06, 2011 1:05 am
Location: Tacoma area, WA
Contact: Website

Re: Supplemental cooling for the charger.

Fri Jul 13, 2018 7:38 am

Good point Don, I’ll try to run a test to confirm the lower max temp on lower amps. The top of the charger is thermally insulated so effectively that I wouldn’t be very surprised if it reaches a similar temperature after 10-12 hrs and just spends more time cooking!

Our usage patterns usually dictate either L2 recharging, or to use another car (how else does one accumulate 110,000 i-miles in 6 1/2 yrs?). Though there are many days when L1 could suffice, but doing that mental math on every plug-in is not acceptable to my wife.
2012 i-SE "MR BEAN" 96,000 miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh
1965 Karmann Ghia Cabriolet

Aerowhatt
Gold Member
Posts: 434
Joined: Wed Jan 28, 2015 1:52 pm

Re: Supplemental cooling for the charger.

Fri Jul 13, 2018 4:40 pm

So I had hooked up a remote sensor to the charger top plate last night and had a lot of driving this morning. On the road the unit working as only the DC to DC with all that air flowing around from motion only runs 3 or 4 degrees F above the ambient temperature.

Charging on L1 at 12 amps it peaked at 128F which is 48F above ambient. Switching to L2 the temperature rose to a a peak of 136F or 56F above ambient temperature. So an extra 8F degrees of heat build up for L2 charging.

Jay if I'm understanding your description of the motor bay hatch insulation on your 2012 it actually touches the top of the charger unit? The 2014 hatch definitely has some air space between the hatch sound insulation and the top of the charger. I would guess somewhere around 3/4 of an inch. The insulation is molded on the bottom side to provide this space. Still since heat rises I'm sure the air temperature under there while charging hovers significantly above ambient temperature. I think a well placed Nidec blower (12 volt 0.6 amps 25 cfm) would lower those numbers by around 20F. My experience is that all electronics run better and longer if kept as cool as possible. 136F isn't all that bad, in my experience, but the internal components are hotter than the casing.

Something to consider for sure considering the out of warranty cost and/or hassle of replacing a charger dc/dc. Another thought what if the coolant pump ran full time instead of just 25% of the time while charging???

Aerowhatt
2014 cool silver ES, acquired new 4/2015 (42.7ah at ~26K miles)
2014 Labrador Black Pearl ES, acquired new 3/2016 (41.5ah at ~15k miles)

siai47
Posts: 360
Joined: Fri Jun 14, 2013 5:54 pm

Re: Supplemental cooling for the charger.

Fri Jul 13, 2018 5:45 pm

The charger, inverter and motor are in the same cooling loop. There is a pump that circulates coolant through all three during charging. If you put your hand on the coolant hose between the inverter and the charger you can feel the circulating pump cycling on and off. And yes, the motor gets hot during charging as it's windings are used as part of the charging circuit. The coolant flows to the radiator at the front of the car and there in is the problem. Although the radiator heats up, with the car stationary, there is no airflow to cool the radiator. If the cooling fan would start during charging, the problem would be solved. However, it doesn't. I have used a fan blowing in the radiator opening and with the hood open a whole lot of hot air comes out of the radiator. The components in rear cool right down. So, try a way of turning on the radiator fan when charging and solve the problem or put a fan in front of the radiator and see if this works for you. In the summer in central Florida I always used this method when L2 charging.

jray3
Posts: 1585
Joined: Tue Dec 06, 2011 1:05 am
Location: Tacoma area, WA
Contact: Website

Re: Supplemental cooling for the charger.

Fri Jul 13, 2018 9:27 pm

Thanks siai47, so glad to see you still dropping by to contribute. A reed switch on the pump circuit to activate the radiator fan relay could be a way to maximize that cooling without excessive runtime.
2012 i-SE "MR BEAN" 96,000 miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh
1965 Karmann Ghia Cabriolet

Aerowhatt
Gold Member
Posts: 434
Joined: Wed Jan 28, 2015 1:52 pm

Re: Supplemental cooling for the charger.

Sat Jul 14, 2018 6:30 am

The radiator fan has two speeds. The low one is very unobtrusive and almost unnoticeable. I noticed it inside the garage with the AC on medium. It will come on to cool the AC condenser periodically. This fan speed would be perfect for getting the job done without using a bunch of power or making much sound.

Me too: thanks for checking in Siai47!

Aerowhatt
2014 cool silver ES, acquired new 4/2015 (42.7ah at ~26K miles)
2014 Labrador Black Pearl ES, acquired new 3/2016 (41.5ah at ~15k miles)

kiev
Posts: 815
Joined: Sun May 03, 2015 7:15 am
Location: The Heart o' Dixie
Contact: Website

Re: Supplemental cooling for the charger.

Sat Jul 14, 2018 7:47 am

Maybe someone with a CDROM version can check for the US cars, but there are two relays shown in the online workshop manual, Lo and Hi, for the fan. Maybe a jumper wire with a switch can be made to turn on the Lo relay whenever you want it.
kiev = kenny's innovative electric vehicle

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