Car wouldn't start, now does after charging. What happened?

[LeftieBiker]

In the Leaf, if the computer detects the right voltage, it starts, if it doesn't it doesn't start. It's digital, not analog. An ICE car takes a huge current to start, the Leaf just needs the computer to see the "right" voltage. Completely different animal.

This shows a basic misunderstanding of how the car works. If the above were true, the car wouldn't really need a 12 volt battery - it would just turn the DC/DC converter on or off as needed. What actually happens, however, is the "computer" is off, (or sleeping, whichever you prefer), until the power button is pressed. Then about 2 amps, IIRC, is needed from the accessory battery to energize an electro-mechanical relay or two, to boot up the car - including the electronics that run things. So the "computer" isn't "looking" for 12 volts as a signal. It can't do anything until the startup relay(s) energize the car's systems. And that takes at least 11.9 volts, IIRC, and about 2 amps (it may be 10 amps, I just woke up!) to actually power the relay(s).

 

[VitaminJ]

Just a matter of semantics, the underlying point is true: if the computer sees a 12v voltage too low it won't go into ready mode and will show xmas tree dash.

As you say the current draw is very low and the voltage is the key.

 

[IssacZachary]

It can't do anything until the startup relay(s) energize the car's systems. And that takes at least 11.9 volts, IIRC, and about 2 amps (it may be 10 amps, I just woke up!) to actually power the relay(s).

At least 11.9V! I've been wanting to look up what the starting voltage would have to be on a Leaf but that's ridiculous! The fine electronics in any other car can run off of much less than that!

 

[IssacZachary]

Interesting scenario. The wife left the car on in accessory mode for about three hours, at night, with the lights and CC fan on and the radio playing. The red battery light was on, but the car started right away.

 

[IssacZachary]

Leaf dead again!

I didn't charge it last night. Got in it this morning and no lights turned on at all on the dash. Checked the voltage and it was 6.1! Threw on a jumper cable from my Golf and voltage shot up to 13.3 according to the analog voltmeter. Tried starting the car with the charger (jumper from Golf) on it and still wouldn't start. I tried putting the negative on the frame and still no start. I also put a shunt from the negative post to the negative terminal and got around 5 amps charging.

I'm still charging just the 12V batter to see what happens.

EDIT: Sorry, I didn't adjust the ammeter correctly. It was charging at around 7.5 amps. Then I disconnected the charger (jumper from Golf) and just plugged in the EVSE. Now it's charging at 22.5 amps. I'll leave it at that for now and see what happens.

And sorry if I made any confussion when I kept calling the jumper from my running Golf a "charger."

 

[jjeff]

Sounds like a shot 12v battery, almost an open and my guess as to why the Leaf didn't start even with your charger hooked up is because your charger isn't putting out a clean enough voltage and the battery being almost an open, isn't filtering it.
I'd look for a decent replacement, either a Optima yellow top battery, 12v Li battery or the cheapest route would be a similar lead acid battery as the original.

 

[IssacZachary]

Sounds like a shot 12v battery, almost an open and my guess as to why the Leaf didn't start even with your charger hooked up is because your charger isn't putting out a clean enough voltage and the battery being almost an open, isn't filtering it.
I'd look for a decent replacement, either a Optima yellow top battery, 12v Li battery or the cheapest route would be a similar lead acid battery as the original.

Thanks! I need something that can tolerate sub-zero temperatures in Colorado so I'll probably go with the Optima although I'd really like a lithium battery.

 

[IssacZachary]

After just a few minutes charging current went down to near zero. I unplugged the EVSE and the Leaf started just fine. The shunt didn't even get warm to the touch! That sounds like a really poor battery!

 

[IssacZachary]

Well I ordered the Optima Yellow Top. It'll be in on Wednesday. We'll see how it goes.

 

[GerryAZ]

22 amperes charging current from DC-DC converter indicates relatively high internal resistance; only a few minutes of charging before current dropped indicates very little capacity in the old battery--new Optima should solve your issue. I still don't understand why your car would not start when connected to the Golf since I started my 2011 from a running SUV after the OBDII Bluetooth adapter (with Leaf Spy running on a phone left on the seat) completely drained the original 12-volt battery while I was out of town for a few days.

 

[IssacZachary]

I know, it's very odd how the Leaf reacts to situations that should theoretically work. For an example while the Leaf is connected to the Golf the red battery light doesn't turn on. Maybe if the voltage is too high the car won't turn on?

Back to keeping the Leaf running, I'm contemplating getting a Priority Start battery saver. The idea is if the battery gets down to 11.7V the Priority Start disconnects it completely which saves the lead acid battery from damage since draining it any more can damage it. Running a battery down to 0V will take off half it's capacity.

 

[LeftieBiker]

Damage starts to occur well before you get a lead-acid battery down to 11.7 volts. If the thing can be adjusted I'd set it for about 12.2.

 

[IssacZachary]

Damage starts to occur well before you get a lead-acid battery down to 11.7 volts. If the thing can be adjusted I'd set it for about 12.2.

Thanks! I'll look into it.

The way I understand it, lead acid batteries love to be kept topped off. I'm also thinking of getting a bigger solar charger to put on the roof.

 

[LeftieBiker]

They love to be kept charged, but can also suffer if overcharged. You don't want the electrolyte to boil, or even "simmer."

 

[IssacZachary]

They love to be kept charged, but can also suffer if overcharged. You don't want the electrolyte to boil, or even "simmer."

I understand that the Optima battery is very touchy with that. They have a solid electrolyte in a sealed case so boiling would cause major problems.

If I put a solar panel on the roof I'd make sure it had a proper battery charge controller.

 

[GerryAZ]

AGM batteries (like the Optima) should not be overcharged because there is no way to replace any electrolyte lost through the pressure relief. The charging algorithm of the Leaf's DC-DC converter is ideal for the Optima so you should be fine once you get your new battery. I will buy a yellow top Optima as soon as my original battery starts showing weakness.

AGM batteries have liquid electrolyte absorbed in fiberglass mat material so they can handle high discharging and charging rates (provided long term float voltage is not too high). Their high current capability and low internal resistance make them far superior to gel cell batteries (semisolid electrolyte) for most applications.

 

[stifn43]

The way I understand it, lead acid batteries love to be kept topped off. I'm also thinking of getting a bigger led light solar panel to put on the roof.

Hello IssacZachary,

How Heat Affects Solar Panel Efficiency??

 

[IssacZachary]

Hello IssacZachary,

How Heat Affects Solar Panel Efficiency??

As far as I understand it, heat causes solar panel efficiency to lessen. It might also lower the longevity of the panels. The great thing is for me that I live in a cool area. I just woke up to a couple inches of snow. The bad thing though is that I'll have to brush the snow of the car quite regularly.

 

[JohnKuthe]

Damage starts to occur well before you get a lead-acid battery down to 11.7 volts. If the thing can be adjusted I'd set it for about 12.2.

Thanks! I'll look into it.

The way I understand it, lead acid batteries love to be kept topped off. I'm also thinking of getting a bigger solar charger to put on the roof.

All other things being "nominally equal" a larger area solar panel can only be a good thing! More electrical energy can be converted from light that way.

PS I have a Bachelor's degree in Electrical Engineering so I kinda know what I'm talking about!

John Kuthe...

 

[IssacZachary]

All other things being "nominally equal" a larger area solar panel can only be a good thing! More electrical energy can be converted from light that way.

PS I have a Bachelor's degree in Electrical Engineering so I kinda know what I'm talking about!

John Kuthe...

Either a bigger solar panel or a large magnifying glass over the little solar panel. :lol:

No but seriously, my dream would be to plaster the whole car in PV cells and have them charge a 12V 500F ultracapacitor pack (made up of 6 x 3000F ultracapacitors in series) that powers a 120V AC inverter that charges the traction battery through a 6A 120V EVSE somehow hardwired directly to the onboard charger, or use the energy from the solar panels and ultracapacitors to directly charge the 12V battery when the traction battery is not charging. As far as I understand (man, I seem to overuse that phrase) when the traction battery is being charged, so is the 12V battery, so a setup like this would tend to keep the 12V battery plenty charged all the time.