How is the 12V battery recharged? Max amperage?

[gregoryjward]

ht2 wrote:
When the Leaf is ON, DC-DC converter is always on and supplying 13.5V or Turn on only when 12V battery is low?

drees wrote:
Yes, when the LEAF is on it will always supply ~13.5v to make sure the 12v battery is charged.

Should be clear between "Off", "ACC," "On," and "Ready" states. Only the "Ready to drive" mode engages the traction battery and continuously supplies 13.5volts even after the 12v battery is charged. What's called "On" state in the manual is arrived at after two pushes of the power button from "Off" without touching the brake pedal. All 12v accessories, power windows, windshield wipers, Carwings, etc. are available, but anything requiring 400v is deactivated. Unpowered devices include power steering, climate control (fan will run but no heater or A/C), traction motor (obviously), and DC/DC converter. From "On" you can move the transmission between 'P' and 'N' only. Useful for getting a tow after you've killed your battery...

One other fun bit of trivia. The 12v charging system is smart enough to notice when the lead-acid battery has reached full charge, at which point it backs off the voltage from 14.5v or so to 13.5v. This is really ideal care for these batteries -- the Leaf is really kind to its 12v baby. Given that the thing never does much more than operate a few relays and accessories (i.e., no cranking amperage), it should have a good, long service life. What other car checks that its 12v is topped up and charges it automatically every week or so?

[Ingineer]

The Leaf's DC-DC converter can supply up to about 1.7kW or 135a. This unit takes ~400v power from the traction battery and makes approximately 13 volts. (varies according to charge requirements of the 12v aux battery) It should be able to power up to 1.5kW of external load with no problems, provided most of the accessories are left off.

One interesting thing is, unlike the 12v system on a ICE car, there is almost no voltage sag. The DC-DC converter is a high-frequency switch mode converter, so it can respond very fast to high current surges, whereas a normal ICE car alternator cannot, and it's also RPM dependant for maximum output.

WARNING: NEVER connect anything directly to the negative post of the Leaf's 12v aux battery! This is a current sensor and doing so will disrupt the charging system! (Connect all accessories to the body ground, or, if high-current, the black wire screwed to the top of the DC-DC JB. (Behind the inverter)

Note: I have not tested it at full load for an extended period of time, so there may be some thermal limiting that could cause output to drop after long runs of high-current use.

Here's my test:


-Phil

[gregoryjward]

The Leaf's DC-DC converter can supply up to about 1.7kW or 135a. This unit takes ~400v power from the traction battery and makes approximately 13 volts. (varies according to charge requirements of the 12v aux battery) It should be able to power up to 1.5kW of external load with no problems, provided most of the accessories are left off.

One interesting thing is, unlike the 12v system on a ICE car, there is almost no voltage sag. The DC-DC converter is a high-frequency switch mode converter, so it can respond very fast to high current surges, whereas a normal ICE car alternator cannot, and it's also RPM dependant for maximum output.

WARNING: NEVER connect anything directly to the negative post of the Leaf's 12v aux battery! This is a current sensor and doing so will disrupt the charging system! (Connect all accessories to the body ground, or, if high-current, the black wire screwed to the top of the DC-DC JB. (Behind the inverter)

Note: I have not tested it at full load for an extended period of time, so there may be some thermal limiting that could cause output to drop after long runs of high-current use.

Thanks, Ingineer -- great info., as usual!

I didn't realize about the current sensor on the (-) battery lead. Is there a similar problem connecting to the (+) battery terminal? Fuse amperage or something like that? I don't know where else one would connect.

[Ingineer]

Is there a similar problem connecting to the (+) battery terminal? Fuse amperage or something like that? I don't know where else one would connect.

Not at all, just be sure to fuse or circuit breaker it properly, and do so as close to the (+) terminal as possible. Connecting the (-) to the body or the DC-DC case will ensure a low-noise connection.

-Phil

[Herm]

so it looks like we can use the Leaf's battery as an emergency power source.. run a small fridge, computer.. etc

[essaunders]

Phil - thanks for that information. Is your information source Nissan documentation or your own investigative work?


also,(a little off topic, but perhaps relevant) how does this LEAF behavior compare to the "iconic" (04-09) and "New" (10+) Prii? I thought the Prii were slightly more limited in 12V power - do they have the same resistance to voltage sag?

thanks

[CWO4Mann]

so it looks like we can use the Leaf's battery as an emergency power source.. run a small fridge, computer.. etc

I have a VHF-UHF Ham Radio tranceiver and a High Frequency all-band SSB Ham Radio in the Leaf. The mobile antenna for the HF rig is a tuned whip, but can be detached and a portable NVIS wire antenna can be set up in about 5 minutes to give high-reliability data communcations using a laptop computer and PSK and WinLink. Also, my portable 6KW Generac genset outputs 220V and can be connected directly to the upgraded EVSE cable set. As long as the gasoline and bullets last we can communicate with almost 99% reliability out to about 500 mile radius of Nashville.

I'm fixing to post a complete review with photos of this system, real soon now, so other Preppers can benefit when TSHTF.

Dave

[Ingineer]

Phil - thanks for that information. Is your information source Nissan documentation or your own investigative work?


also,(a little off topic, but perhaps relevant) how does this LEAF behavior compare to the "iconic" (04-09) and "New" (10+) Prii? I thought the Prii were slightly more limited in 12V power - do they have the same resistance to voltage sag?

thanks

As you can see from my picture above, I actually performed a laboratory test. Previously, I have also tested the Gen II (04-09) Prius, and it is not as capable, nor does it provide a true 3-stage charge algorithm for the Lead-calcium battery like the Leaf does.

You could safely hook up a 1000w inverter to the Leaf. Though remember you'll only be able to run it (assume 70% load) for about day before the Leaf is dead.

-Phil

[LTLFTcomposite]

You could safely hook up a 1000w inverter to the Leaf. Though remember you'll only be able to run it (assume 70% load) for about day before the Leaf is dead.
...
WARNING: NEVER connect anything directly to the negative post of the Leaf's 12v aux battery!

Should be clear between "Off", "ACC," "On," and "Ready" states. Only the "Ready to drive" mode engages the traction battery and continuously supplies 13.5volts even after the 12v battery is charged.

With a tropical storm bearing down this topic has renewed interest to me.

So to summarize, it should be OK to connect an inverter (up to 1000w, although mine is just a little 400w) to the Leaf using alligator clips to the positive battery terminal and the car frame, and run it with the car in the "Ready to drive" state?

[TonyWilliams]

You could safely hook up a 1000w inverter to the Leaf. Though remember you'll only be able to run it (assume 70% load) for about day before the Leaf is dead.
...
WARNING: NEVER connect anything directly to the negative post of the Leaf's 12v aux battery!

Should be clear between "Off", "ACC," "On," and "Ready" states. Only the "Ready to drive" mode engages the traction battery and continuously supplies 13.5volts even after the 12v battery is charged.

With a tropical storm bearing down this topic has renewed interest to me.

So to summarize, it should be OK to connect an inverter (up to 1000w, although mine is just a little 400w) to the Leaf using alligator clips to the positive battery terminal and the car frame, and run it with the car in the "Ready to drive" state?

Sounds reasonable. What are you going to power? The refrigerator?