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garygid
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 10:49 am

I AGREE!!!

IF (yes, IF) there is NO "non-political" reason, Nissan should say so.

Then, with sufficient time available, there is no technical reason to avoid using L1, and it does not harm the battery to use L1 frequently, or even exclusively.

Something like: "We do not recommend frequent L1 charging, but there is no known technical reason to avoid using L1 charging."
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AndyH
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 11:06 am

Nubo wrote:I've read that certain batteries actually charge better at higher rates vs. trickle-charging. This is due to the way that some chargers determine the charging cutoff point. For consumer-type rechargeable batteries, a "smart charger" will usually use a combination of Delta-V (change in voltage over time), and DT/Dt (rate of temperature change over time). Changes in these values are interpreted as "signals" that the pack has reached a certain state of charge. At very low current levels, these "signals" can be harder to detect and the charger may have to fall back to it's fail-safe method of temperature cutoff, resulting in some degree of overcharging.

This info comes from consumer-grade cells and I have no idea if this has any bearing on the LEAF battery chemistry or charging algorithms.
The delta V and temperature bump are end of charge points for NiMH cells. They're charged with constant current up to the end of charge point. These methods are also used when charging the earlier EVs that use nickel metal hydride cells. So yes - there is absolutely an "EV" connection here - it just doesn't apply to the Leaf.

Lithium is charged with a 2-stage process of constant current then constant voltage - just like lead acid cells. Lithium doesn't get the 'float' stage that lead gets, and lithium doesn't get the 'scheduled overcharge' that some lead gets for cell balancing.

Lead acid batteries lose about 20% of their charge each month, so they are routinely 'trickle charged' at maybe 1-2A to keep them full. Lithium only loses about 3% per month so doesn't need the 2A tourniquet to stop the bleeding. ;) In a real sense, the Leaf's level 1 charge isn't a true 'trickle charge' as it's feeding about 5A into the pack initially.


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AndyH
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 11:07 am

garygid wrote:I AGREE!!!

IF (yes, IF) there is NO "non-political" reason, Nissan should say so.

Then, with sufficient time available, there is no technical reason to avoid using L1, and it does not harm the battery to use L1 frequently, or even exclusively.

Something like: "We do not recommend frequent L1 charging, but there is no known technical reason to avoid using L1 charging."
That would be a much more clear message than saying "we felt it useful to include a Level 1 EVSE in a bag in the trunk but just like common sense we don't recommend you use it." ;)

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sdbonez
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 11:10 am

Jimmydreams wrote:
mogur wrote:One interesting thing I discovered in studying the schematics is that the Leaf has the same oddity that most other Japanese cars seem to have: The accessory outlet is off if the car is not "On" or in "Acc". Our Acura did the same and it is highly annoying if you want to charge a cell phone or such when the car is off. I will be rewiring the Leaf just as I did on the Acura.
Yeah, but leave your radar detector in the car in the "ON" position for a few days = dead battery. It's happened to me on a few occasions. (I drive slower now and don't need a radar detector).

To each his/her own, I guess. ;)
Not me, already thinking about how I'm going to custom-mount my V1 :)
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PaulScott
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 11:40 am

I suspect the reason might be two-fold. As some have mentioned already, the length of time might be a problem for some people, and BTW, this should always be phrased as "L1 charges at 5 miles of range for every hour of charging." instead of "It take 20 hours to charge at L1." This tells people who need to go X miles that they only need to charge enough to get where they are going instead of waiting for a full charge. A lot of my customers are under the impression they have to keep charging till full and this scares them.

The other reason may have to do with the overhead of charging and that the total kWh going into the pack is slightly higher due to the higher percentage of energy devoted to the overhead at L1 vs. L2.

Just a guess, but that might be their reasoning. I agree that they should tell us why they are concerned.

smkettner
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 12:22 pm

PaulScott wrote: As some have mentioned already, the length of time might be a problem for some people, and BTW, this should always be phrased as "L1 charges at 5 miles of range for every hour of charging." instead of "It take 20 hours to charge at L1." This tells people who need to go X miles that they only need to charge enough to get where they are going instead of waiting for a full charge. A lot of my customers are under the impression they have to keep charging till full and this scares them.
I completely agree. If you have 12 hours each night to charge then you can refill 60 miles each night. Actually I think L1 will prove faster than 5mph up to 80% charged. So a person may well get 6 to 7mph during the first 10 hours from a low start.
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DarkStar
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 12:23 pm

PaulScott wrote:A lot of my customers are under the impression they have to keep charging till full and this scares them.
This is exactly why I never supported the whole "it takes 20 hours or 8 hours to charge" and will just state that Level 1 charges at a rate of 5.5 miles per hour and Level 2 charges at a rate of 12.5 miles per hour.

Assuming:

Level 1 = 120 volts @ 12 amps
Level 2 = 240 volts @ ~14 amps (Maximum of 208 volts @ 16 amps for a 3.3 KW charger)
Pack Capacity = 24 KWh, but takes 26.4 KWh of energy to completely charge (10% inefficiency)
24 KWh = Average of 100 miles
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evnow
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 2:02 pm

AndyH wrote:Lead acid batteries lose about 20% of their charge each month, so they are routinely 'trickle charged' at maybe 1-2A to keep them full. Lithium only loses about 3% per month so doesn't need the 2A tourniquet to stop the bleeding. ;) In a real sense, the Leaf's level 1 charge isn't a true 'trickle charge' as it's feeding about 5A into the pack initially.
Hmmm ... is this what the manual actually means ?

They are just saying don't top off the battery all the time ?
1st Leaf : 2/28/2011 to 5/6/2013
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garygid
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 2:28 pm

L2 current at 240v (just like 208v) is still the same 16 amps, we believe.

Quite possibly, using an L1 EVSE (120v on a 20-amp circuit) set to "16-amps max output", the LEAF's charger would "eat" all 16 amps.
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AndyH
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Re: "Trickle charging is not recommended for regular use"

Wed Dec 22, 2010 3:12 pm

evnow wrote:
AndyH wrote:In a real sense, the Leaf's level 1 charge isn't a true 'trickle charge' as it's feeding about 5A into the pack initially.
Hmmm ... is this what the manual actually means ?

They are just saying don't top off the battery all the time ?
Probably not. Maybe a tech writer decided that the 120V cord can only supply a trickle compared with 16A from an L2 EVSE. :?

When we plug-in with half charge remaining, the pack will measure about 345V. The L1 at 12A is about 1440W - so we'll get about 4A into the pack. If the charger maxes out at 3300W when fed 240V, the L2 will push a bit over 13A into the pack.

Trickle charge is designed to make up for the self discharge. For our 24kWh pack, we're talking about 720Wh per month self discharge - roughly 1/2 an hour of L1 time per month...

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