Too hot to grid charge or bad bat?

**thedhgroup** · 07-17-2011, 06:57 PM

I built a grid charger and the first time I balanced the pack it made a huge difference. No more charging off the engine for a whole day and no recals. I recently installed a clutch switch and I got a little behind in keeping the battery up. But I got way more lean burn time. So on Friday I came home with the soc at about 1/4. I could not resist the urge to use the grid charger again but the soc won't go up to the top. The most it went up was half and after soaking it for 12 hours the current dropped so I assumed it was charged. The next morning I checked the voltage and it was 158. It either did not charge all the way or it lost 10v over 10 hours.

The pack fan runs when charging and the intake air temp was around 85 degrees and the output was hotter but not that big of difference. At rest the air temp was 100 but I was not charging and the fan not running. So did I not give it enough time to charge, does the voltage sag when hot or is my pack on its way out? I guess at this point I may reduce the use of the clutch switch mod and grid charging when hot out if my quest for high mpgs is hurting the car.

**uhtrinity** · 07-17-2011, 07:08 PM

Do you know the temp of the battery? A hot battery will be limited in its top voltage and any additional charge will be converted to heat. I could and would never charge in the open sun, however now that I have a shop I have found I can charge during the day without the temps I used to get. 120 - 125 F is to high imo.

gilbertguy · 07-17-2011, 07:20 PM

I have a grid charger on order so haven't actually done it yet myself. My garage runs around 95F even at night so I'm a little worried that might be to warm but at least the sun can't beat down on the car in there.

**thedhgroup** · 07-17-2011, 07:40 PM

I don't have a temp probe in the pack but I would not be surprised if it is in the 120 range. Lesson learned. No trying to top off a pack when it is super hot outside. The car is in the garage in the shade but the heat is beating on the roof during the day and the mass of the cement is holding it in at night. It is just to hot to charge. I've never driven this car in this kind of heat. I wonder how the assist and regen will behave?

Eli · 07-17-2011, 08:00 PM

You're charging the pack at 350mA right? Also, you have the BCM on while you're charging? That's the only way to watch the SoC go up.

I grid charged when it was over 90 degrees outside. At 350mA, there is not a lot of heat being produced, even when the pack is fully topped off.

When it was 90+ outside, the battery temp was 96 degrees as measured by the pack's four thermistors, and the exhaust temp was around 102 degrees.

If the fan was running, it is likely the pack's temperature was only a few degrees above ambient. I think your pack just wasn't full yet? Voltage will be depressed at those temps, but not that much in my experience.

**thedhgroup** · 07-17-2011, 08:16 PM

350ma? No, I built mine at 700ma. My thought was to opportunity charge and bump the pack up a little from time to time. So without changing the settings on the charger I got one good charge last week and one not so good yesterday. The only difference is that this time it is hot out. The voltage meter said it was at 168 and the current down to 200ma so I quit and a few hours later the voltmeter said 158.

I've noticed it takes about 10 minutes or so to register the new SOC and with this heat I just can't get it up to the top.

**uhtrinity** · 07-17-2011, 08:20 PM

700mA will definitely push a singles packs temps up. Either charge in the shade or don't charge during the day.

**thedhgroup** · 07-17-2011, 08:32 PM

Another reason I chose 700ma was that I have a second pack I will be adding to the system soon. I figured I'd need a higher output charger to get them both charged up. If it is 90 degrees out and 120 in the car, I guess I forget about opportunity charging during the day.

3-Wheeler · 07-17-2011, 08:46 PM

I have noticed that my pack easily looses about 10 volts, dropping from topped-off to 160 or so volts anytime the outside temperature is 90F or above.

This has happened on several occasions now. Today in Wisconsin we are sitting at almost 100F.

I suppose it could mean that I have some weak cells, but daily grid charging has seemed to perk-up the pack somewhat.

Jim.

Eli · 07-17-2011, 08:46 PM

Oh wow.. Yeah, 700mA is a lot. I have no experience with that. I just hope you didn't cook your pack.

700mA would be a good bulk charge, but I don't think you want to be topping your pack off at 700mA???

That's why everyone has 350mA chargers.. It's safe to give topped off cells 350mA while the others catch up. I don't know about 700mA.....

Also, I open both doors and the hatch to increase air flow when grid charging no matter what the temperature.