Grid Charging Outdoors - Heat Issues?

[Artric]

I'm proud to have assembled my awesome grid charger, with a big thanks to Mr. Mike Dabrowski (my hero)!

Anyway, as much as I'd like for my Insight to live indoors, it's the workhorse. My garage is filled already with my lovely S2000, 599, two Ruckuses and my girlfriend's baby - her CRX. This means that when I'm charging - I'm charging outdoors.

I'm a little worried about this - should I be? Note that I'm in FL, and the heat of summer is coming upon us. But also note that I do have a full 12v going to the battery fan and also 12v to a 120mm fan that cools my 350ma charger.

My battery is technically in the shade, and I do my best to situate the charger under the shade of the roof of the car, but the temps inside the car can surely get high. I haven't tested them yet, but plan to. At what point should I consider the ambient temp unsafe?

Is charging in the hot summer sun a terrible idea? It doesn't seem like there are any safeguards in place, but at 350ma, does there need to be?

Any educated thoughts very much appreciated!

I eventually would like to move to a more complex setup, but in the meantime, I may assemble a 700ma charger to do a large part of the charging in the cool hours and control it manually. I'll then use those parts to assemble Mike's automatic charger, once I learn a little bit more.

[Artric]

Where's everybody at? No input?

[RobertSmalls]

With the fan running, I expect you'll see the battery at ambient during bulk charging, and only slightly hotter during topping off. I wouldn't worry about it.

Without any other data, my only recommendations include leaving a sun shade in the windshield, tinting your glass to the legal limit, and running the charger on a timer.

Request for data: Stick a thermal probe in your car, and in your battery.

[aisbell]

Originally Posted by RobertSmalls

Without any other data, my only recommendations include leaving a sun shade in the windshield

I found a collapsing reflective sunshade that fits nicely over the inside of the rear hatch window. It is designed to fit on one half of a large windshield. Heat isn't as much a problem in Sweden as it was in Honolulu but I use the rear sunshields to hide cargo that I'm carrying on the rear shelf. I lay one of these sunshields directly over my cargo and install the other in the gap between the rear hatch glass and its frame so that it hugs the glass pretty well. That does reduce the interior temperature when my car is parked in the sun.

[MN Driver]

I'd personally try and wire in some sort of thermal protection to where if the batteries reach, say 40C it stops charging until it gets unplugged and plugged back in again with the pack fan running full tilt while charging on a hot day. With 350mAh I don't see it being too big of an issue as the cells won't heat up much from that but I don't know what the ambient temp will be in the car either as there have been times where I've gotten in my car after it was parked in the sun and have had my car be in current limit based on the stock charge/assist meter right off the bat.

[uhtrinity]

I never charge my batteries in the sun, only at night, unless it is cold outside or very overcast. Fortunately I park on the shaded side of the house. Over a year ago I saw battery temps hit 130F due to charging during the day and it was only 90F outside. The fans were also running on a 9V brick.

[Mr. Mik]

Originally Posted by Artric

...
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This means that when I'm charging - I'm charging outdoors.

I'm a little worried about this - should I be? Note that I'm in FL, and the heat of summer is coming upon us. But also note that I do have a full 12v going to the battery fan and also 12v to a 120mm fan that cools my 350ma charger.

My battery is technically in the shade, and I do my best to situate the charger under the shade of the roof of the car, but the temps inside the car can surely get high. I haven't tested them yet, but plan to. At what point should I consider the ambient temp unsafe?

Is charging in the hot summer sun a terrible idea? It doesn't seem like there are any safeguards in place, but at 350ma, does there need to be?
...
...

It all depends where the air in being sucked in from.

If you run the fan at 12V to pump 70degC hot air through the battery then you will be heating the battery - at least in the initial charging stages.

It may matter if the charger is in the shady area inside the car, but it matters at least as much if the entire car is in the shade.

This is the main reason why I wanted about 600mA for my grid charger: It allows to commence an EQ charge in the evening, reaching the most heat producing stage of charging in the early morning hours and finishes before the heat is getting severe again.

But is EQ charging really what you are trying to do?

If you want to regularly charge your battery, then you must stay far away from the 100% full mark, or you will destroy it in short order. You might get temporarily improved mileage, but your battery will be toast in a couple of years or less.

Charging from 30% SOC to 70% SOC at 350mA produces very little heat and not much battery ageing. But even that could be a problem if the car is parked in the sun.

Can you install an air intake pipe that provides fresh outside air to the batteries (without letting water and animals like mice and wasps in)?

[RobertSmalls]

Originally Posted by Mr. Mik

If you want to regularly charge your battery, then you must stay far away from the 100% full mark, or you will destroy it in short order. You might get temporarily improved mileage, but your battery will be toast in a couple of years or less.

"Stay far away", or just avoid spending hour after hour there every day? Either way, [citation needed].

Originally Posted by Mr. Mik

Can you install an air intake pipe that provides fresh outside air to the batteries (without letting water and animals like mice and wasps in)?

There already are two external ducts on the Insight with fans on them: the IPU fan and under-dash blower.

[uhtrinity]

Originally Posted by Mr. Mik

If you want to regularly charge your battery, then you must stay far away from the 100% full mark, or you will destroy it in short order. You might get temporarily improved mileage, but your battery will be toast in a couple of years or less. ?

I tend to disagree, that is as long as you trickle charge to the full mark and avoid excessive heat. I figure I have cycled my packs at least 600 times in the last two years and haven't seen any noticeable loss in battery capacity. Out of those 600 times the packs had to have been well into the 90 percent range since I was using a dumb charger set at 175 volts putting out a maximum of 700mA (for two packs).

My current charger (no pun intended) is of the meanwell variety and stays right at 350mA per battery until the pack voltage hits 169 - 170 volts. It is bound to hit into the 90 percent if I leave it plugged in for too long.

[Mr. Mik]

Originally Posted by RobertSmalls

"Stay far away", or just avoid spending hour after hour there every day? Either way, [citation needed].

There already are two external ducts on the Insight with fans on them: the IPU fan and under-dash blower.

Don't stuff them and don't drain them on a regular basis if you want long life out of a NiMH battery - that seems to be generally accepted gospel in EV and hybrid vehicle circles. Maybe it's only true for stuffing too fast, with heat production, but at 350mA = C/18 you can do a lot of cumulative damage. C/100 is often mentioned as the maximum "permanently on" trickle charge. Never doing a full EQ charge and never doing a full discharge is also bad, of course!

I for one think it is true that Insight, Civic, Prius and RAV 4 EV achieve their very long battery life predominantly due to the fact that they keep the SOC somewhere between about 40% and 60% (or relatively close to that).

I don't know where these fans are, but what you need is outside air to go straight to the batteries, without mixing with the solar -oven heated cabin air first.