How fast does the 12 volt battery charger charge?

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3ricj

Member
Joined
Mar 16, 2012
Messages
6
I'm sure some of ya'll are trying to max your miles and usage - - but I'm headed in the other direction.

I'd like to hook up some power hungry 12 volt devices to my 2012 leaf. Specifically, around a 1kw sound system.

I'm sure the 12 volt battery can deliver the watts I need. From what I can tell, the leaf will topup the charge on the 12 volt battery using the solar cell (I assume this is at best 50 watts).. but in addition also uses some onboard charger to maintain charge using the main batteries.

My question is: At what rate does the onboard charge system charge the 12 volt battery?

Cheers,
-3ric
 
It should be able to power your 1kW stereo rig with no problems, and no voltage sag.

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:
pic


-Phil
 
That is perfect to know! thank you! Will the 12v battery be charged when the car is "turned off"? .. For example if i connect some appliances to the 12v that will use power when car is off? .. By the way, is there outlets in the car that can give 12v while car is off?
 
Ingineer said:
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)

Thank you for that one! I just know one of these days I'll be connecting my inverter directly to the battery to run something big and I probably would have done this!

PS: LeafScan looks pretty. Where is mine? :D :D :D
 
For reference, my own system has been running about 6 months - total of about 60A max draw, most channels driven at minimum acceptable impedance, and the impact to range has been below measurable levels. No visible impact to 12v accessory systems either (no lights dimming, etc). It's been so surprisingly low impact that I'm planning to ~double it :)

the one thing I've been extremely dissatisfied with is the head - I thought due to its interaction with the rest of the vehicle I'd figure out some way to make line output converters work, but it just hasn't been an acceptable solution. The output from the head unit itself is simply too low quality.

If giving up some functionality is acceptable, you can definitely run an aftermarket unit, but you lose quite a bit:
-Control over charging timers
-Display of climate control functions
-Remote control (climate/charging) functionality
-All carwings functions
-Setting of car functions like auto headlights and auto door locks
-most power consumption/usage displays

Now none of those are functionally critical, but some are relatively important - probably most notably being the charging timer controls.

I started development of a USB device and PC software to interface via CAN and replicate a lot of those functions (so you could use an in-dash PC to replace the stock head unit), but got distracted on other projects. I did get basic CAN-to-device and device-to-PC functionality, but that's about as far as I got. Need to get back to work on that darnit...

Most of the development is just needed work, no hurdles other than time... The only real hurdles I had were hardware... I really don't want to cut wires, but I need to interface with about 2/3 of the ridiculous number of wires connected to the thing :) Wish I could find wired connectors to connect to all the plugs, but I'm pretty sure that's not happening. Thought about dissecting my stock unit and just using the plugs from it, but when I found out the factory prices them in the $1200 range, I thought maybe I should keep it intact :)
 
Ingineer said:
It should be able to power your 1kW stereo rig with no problems, and no voltage sag.

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....

-Phil

Phil, isn't this somewhat below a typical alternator setup? Although some blame the reflectors, I think this is maybe why the high-beams are underwhelming despite having what are normally high-output bulbs. Lumen output of a incandescent bulb is highly dependent on voltage.
 
I know into the early 2000's many alternators were in the just-over-100A range (ie, most 90's-to-2000's GM Alternators were 105A). Also keep in mind those ratings are not idle amperages, I think they generally need to be spinning @~2000rpm to reach rated output.

Just checked on a couple examples - a 2010 Escalade Platinum uses a 160A alternator, so they're definitely increasing, but amperages in the 135A range still should NOT be a problem, especially considering the constant nature of the dc/dc in comparison to an alternator at idle/low cruise...

Oh wait, you're saying voltage, aren't you? That's a fair point then - If the leaf is in the 13v range, that does compare a little bit unfavorably to expected alternator system voltage of ~14.4v
 
It's maybe slightly lower, but that doesn't explain the high-beams. Reflectors is one, and the other is that the LED low beams work so well that in comparison the halogen high's just don't look all that bright.

One thing you can do is adjust the LED low beams a little higher, then use the wheel on the dash to raise them high when on dark roads.

-Phil
 
Here's a question: could you replace the original 12-v battery in Leaf with a larger deep-cycle one (assuming you could make it fit in the space)? (Or would this do more harm than good, since car recharges this from the traction battery?
 
electrifeyed said:
Here's a question: could you replace the original 12-v battery in Leaf with a larger deep-cycle one (assuming you could make it fit in the space)? (Or would this do more harm than good, since car recharges this from the traction battery?

There is really no reason to do this. If you don't abuse your battery there should be no issues.
 
electrifeyed said:
Here's a question: could you replace the original 12-v battery in Leaf with a larger deep-cycle one (assuming you could make it fit in the space)? (Or would this do more harm than good, since car recharges this from the traction battery?

If you're looking for more "run time" on your hi-fi (or accessories), consider replacing the 12v lead-acid with a 12v Lithium; I've been very happy with mine. Search for my thread or read my MNL blog entry ("Get the Lead Out").
 
EVDRIVER said:
electrifeyed said:
Here's a question: could you replace the original 12-v battery in Leaf with a larger deep-cycle one (assuming you could make it fit in the space)? (Or would this do more harm than good, since car recharges this from the traction battery?

There is really no reason to do this. If you don't abuse your battery there should be no issues.

From the point of view of a lead-acid battery, this car abuses the 12V battery as a matter of course. My OEM was on the way out after a year's duty. I wouldn't consider my habits abusive, although I commonly leave the car plugged into the EVSE on days where I don't drive it. This increases the dark-current load on the 12V battery and, perversely, inhibits the car from charging it. Thus the LEAF's battery experiences deep cycling by its design.

I replaced the 12V with an AGM deep-cycle, which is so far holding up quite well. http://www.mynissanleaf.com/viewtopic.php?f=27&t=11094&p=257210" onclick="window.open(this.href);return false;
 
Ingineer said:
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)

-Phil

I just looked my Leaf over, and while I agree you shouldn't connect anything directly to the negative post, clamp or screw, it is fine to connect to the post/nut where the chassis negative cable connects. The current sensor is in between that point and the battery post clamp.
 
^^^ Correct.
As clearly stated by Phil in the jump starting instructions.
See http://www.mynissanleaf.com/viewtopic.php?f=9&t=6707&hilit=jump+start&start=10#p148133.
 
I don't think that anyone answered the critically important question of whether or not the car charges the 12 volt battery while off, because of the possibility of adding large drain accessories. The car does charge the battery every few days, but not enough for any additional loads! In fact, it often isn't enough for expected loads, like having the charging cable connected while the car isn't charging. I short, don't add any car-off loads.
 
LeftieBiker said:
I don't think that anyone answered the critically important question of whether or not the car charges the 12 volt battery while off, because of the possibility of adding large drain accessories. The car does charge the battery every few days, but not enough for any additional loads! In fact, it often isn't enough for expected loads, like having the charging cable connected while the car isn't charging. I short, don't add any car-off loads.
If the vehicle is in ACC mode (just the radio works) then it will run the 12 volt battery to shutdown, no recharge, you'll need a jump to get the vehicle working again. If the vehicle is off, you can run the battery down also, no charging will activate.

If the vehicle is in Standby mode (dash active, radio active, but not drive-able), it will activate the 12 volt system when the battery gets down to 10.5 volts to charge it back up. This is the mode I use to power up my house for emergency power (so the vehicle can't be driven off by accident). But I keep the charge mode active non-stop by keeping a load of at-least 50 watts going so that the battery never tops off and it stops charging.

Finally, if the vehicle is in drive mode, the 12 volt system is active all the time until you drain the traction battery to shutdown.
 
knightmb said:
LeftieBiker said:
If the vehicle is in Standby mode (dash active, radio active, but not drive-able), it will activate the 12 volt system when the battery gets down to 10.5 volts to charge it back up. This is the mode I use to power up my house for emergency power (so the vehicle can't be driven off by accident). But I keep the charge mode active non-stop by keeping a load of at-least 50 watts going so that the battery never tops off and it stops charging.
I take it your powering a 120v inverter off the 12v Leaf battery and what is it's wattage? On a link somewhere at MNL I saw where it was possible(or maybe a future thought) to power a mains outlet directly from the traction battery. The vehicle in question was a eNV200 and was meant to provide mains power to construction job sites where a noisy smelly generator wasn't wanted.
Personally thats the type of power I'd want, something I could run my house off of for a limited amount of time during a several hour power outage. Of course not the central air or things like a stove or dryer but things like the TV, lights, refrigerator/freezer and maybe water pump for those with a well. Maybe someday it will be reality......
 
The LEAF has a wonderful DC to DC for charging the 12V.
But the software for its use does a poor job of keeping it anywhere near fully charged.

Using high power demand devices will make things worse.

At least in drive it will hold the 12V near 13V.
But you will need to frquently put a battery tender on it if you expect it to hold up long term.
 
jjeff said:
Personally thats the type of power I'd want, something I could run my house off of for a limited amount of time during a several hour power outage. Of course not the central air or things like a stove or dryer but things like the TV, lights, refrigerator/freezer and maybe water pump for those with a well. Maybe someday it will be reality......

It's been done by many with the Prius traction battery - up to 4-5 kw peak. Two major differences;
1. The Prius will recharge the (smallish) traction battery indefinitely as long as the tank has gasoline
2 . The Prius traction battery voltage is ~ 200 VDC - there are a number of commercial quality inverters that operate in that range and that have commercial quality transformers to produce the needed 240 VAC split phase.

I am not able to find any such equivalent inverter/transformer combinations that match the ~ 400 VDC requirement. There is an 8 kw inverter that operates at 400 VDC, but requires a center (battery) tap at 0 VDC (+/-200 VDC) that appears to direct connect to the 240 VAC "neutral" output - which likely disqualifies it for any use except a self-contained battery system - not being an EE, I'm not sure. I'll bet that soon there will be a V2H system that has such an inverter designed for 240 VAC split phase - can I justify it? Probably not.
 
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