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E
Ed Lee
Guest
It\'s an old thread, but still useful.
That\'s probably from the back stack, which tends to degrade faster. They are keeping the front stacks themselves. My 2012 Leaf came from Seattle (cold weather), so it\'s in better condition. The back stack is around 60% to 70%. The front stacks are around 70% to 80%.
Rereading old forums confirm that the Leaf battery only balance during charging. Using 400 ohm resistors to shunt off higher voltage, the maximum current is around 10mA. When discharged to empty, the voltage difference between strongest and weakest cells is around 0.5V. I am using 4 sets of 100V auxiliary batteries to balance the main batteries.
I am using 4 sets of 18 awg orange wires in 100V segments, with a 22 awg center taps via a 10 ohms 2 watts resistor. I am wondering if i need 1 or 2 ohm resistors to limit the current on each segment, or the wire resistance itself is enough. My 100V auxiliary batteries are actively balanced with BMS ICs. The BMS has OV(4.2V), UV(2.5V) and OC(4A) protections at the cell level. However, tripping the BMS would require manual reset. I can do it on the road, but other drivers would need to bring it back to the shop.
I believe that the better BMS can unlock the 10% to 15% hidden capacity and additional auxiliary batteries can restore it up to 24kwh.
Other people are working on upgrading to 30kwh, 40kwh and 60kwh with CAN bridge. But i think 24kwh is enough for me, while retaining the old battery cells.
Well, I appreciate the advice thusfar, but that thread is getting built
up quite a bit so to keep it \"real\" I start this one.
More of the same. There are a fair number of Nissan Leaf batteries
floating around that are being used to built battery piles for solar
power system and PowerWall like contrivances.
Nissan Leaf Battery Modules Reused in Solar Energy Storage
https://www.youtube.com/watch?v=FlCz40bCZZM&t=152s> (12:13)
One big catch is that most of them seem to test at about 50% of rated
capacity. It\'s in the video.
That\'s probably from the back stack, which tends to degrade faster. They are keeping the front stacks themselves. My 2012 Leaf came from Seattle (cold weather), so it\'s in better condition. The back stack is around 60% to 70%. The front stacks are around 70% to 80%.
Rereading old forums confirm that the Leaf battery only balance during charging. Using 400 ohm resistors to shunt off higher voltage, the maximum current is around 10mA. When discharged to empty, the voltage difference between strongest and weakest cells is around 0.5V. I am using 4 sets of 100V auxiliary batteries to balance the main batteries.
I am using 4 sets of 18 awg orange wires in 100V segments, with a 22 awg center taps via a 10 ohms 2 watts resistor. I am wondering if i need 1 or 2 ohm resistors to limit the current on each segment, or the wire resistance itself is enough. My 100V auxiliary batteries are actively balanced with BMS ICs. The BMS has OV(4.2V), UV(2.5V) and OC(4A) protections at the cell level. However, tripping the BMS would require manual reset. I can do it on the road, but other drivers would need to bring it back to the shop.
I believe that the better BMS can unlock the 10% to 15% hidden capacity and additional auxiliary batteries can restore it up to 24kwh.
Other people are working on upgrading to 30kwh, 40kwh and 60kwh with CAN bridge. But i think 24kwh is enough for me, while retaining the old battery cells.
E
Ed Lee
Guest
On Tuesday, January 15, 2019 at 1:21:07 AM UTC-8, Mike wrote:
For Leaf:
48x 12\"x9\"x2\"
For Tesla:
7000x 18650 for model S/X, 21700 for model 3, 50800 (estimate) for future?
First 2 digits for diameter (in mm), next 2 for height.
For Leaf, it shunt off cells with higher voltage with a 400 ohm resistor during charging. The battery controller expects cells to be closely matched.. There are problems with strong and weak cells. When there are strong cells, it will limit peak charging voltage. When there are weak cells, the controller will disable the battery system prematurely.
Tesla might have a better BMS, since they learned from the Leaf.
No, the parallel cells will all get the same voltage. It\'s the serial combination causing cells to overcharge/discharge.
> Unless you purchase a NEW pack, the pack will have been decommissioned for some unknown reason.
For the Leaf, poor BMS is one reason.
> It takes considerable care to keep the pack balanced. How much of that is in the pack itself and how much is in the charger is unknown.
Balancing has to be done in the pack.
> You probably won\'t find documentation on the protection management.
The Leaf battery system has been reverse engineered to death.
DC/DC converters can help. I am using multiple 5V-12V to 48V boosters to charge my modules.
But i am only charging a small balancing pack, i am still using the main charger with the vehicle.
On 1/14/2019 7:06 PM, jurb...@gmail.com wrote:
Well, I appreciate the advice thusfar, but that thread is getting built up quite a bit so to keep it \"real\" I start this one.
I have found out that all the guy wants is a regular house refrigerator and a toaster oven. Nothing else will run off an invertor. Lighting will all be low voltage, stove and furnace off propane and A/C off a generator, maybe diesel, maybe something else. Maybe if I can get a really good A/C unit form an older car it would work, just have to run the engine. Those old big cars had one hell of an A/C system in them. The new ones are junk in comparison. Now you got an elcheapo cap tube and a weighed in charge. In the old days it had an accumulator and a thermostatically controlled expansion valve. Also those big long compressors were six cylinder ran by a swash plate. Such a system would cool the whole thing. The only question is whether you want to run the engine. Or maybe do both. We\'re already going under the hod for an extra alternator, and I think that will be a rebuilt form about a 1975 police car for the power. New alternators are not able to charge a dead battery, if you change it the instructions say right out to charge the battery first, don\'t just jump start it. The wimpy alternator cannot handle it.
Someone said to get the real numbers. Well we are going to do that tomorrow. We are going to the DIY (Home Depot I think this time, they are all DIY to me) and we will plug in a new refrigerator with my clamp on ammeter on it. the first order of business is to grab that meter and test it, see how out of calibration it is. I\'ll either calibrate it to a Fluke or have a correction factor to apply. Either way we will have real numbers. The way I see it, the cabinet is going to be warm so the power drain should be within a useably measurable range. The only other thing I could do is to run it a while and cover the condenser with something to build up the heat. That would give us a real worst case scenario, like you are in the desert and it is 100ºF out there, but I think we\'ll get by just fine with the numbers we derive tomorrow. Everything in the system is going to be overbuilt.
Someone said don\'t count on the plate on the fridge ? I think I must agree. The one we saw is a full size but small unit. I mean it is not for a dorm or anything like that. What gets me is it says 160 watts on the back. Well I got this oceanfront property in Kansas... Not sure how I am going to effectively guess the starting draw, but I can just use other motors as a sort of \"rule of thumb\". And that will be handled like my ex boss used to handle parts - add a dollar and double it. Whatever everything says, we will double the capacity. That should mean enough reserve for those dark days as well as good charging current on the bright days. I also have to have a talk with him about the varying output of the PVs. Another thing to figure out is just where does he intend to go. I don\'t really need the address (there probably will not be one) but the latitude is important.
And then the charger. There is no way in hell we are getting a Tesla charger for this thing. Oh ye of little faith, I can do this and do it with a SEPIC so that it will charge until the PVs are almost down to zero. If I just get the usual charger and it wants 120 volts it probably will just shut down if the voltage gets below about 100 volts. That makes it unsuitable. From what I\'ve been reading the 240 volt charger will charge faster. Logically that indicates that the battery is not that picky about low charging current, but of course it takes longer to charge. What does he care if he\'s out deer hunting or some shit ?
So, the way to proceed is once I got the numbers, size the PV and storage to suit, and then some. Maybe the guy wants a stereo, he will want a PC, probably a laptop. That will bring on a new set of problems. You can get Hughesnet almost anywhere, the cheap plan which is pretty good is like $70 a month including equipment rental. The problem is every time he drives the thing the dish will have to be re-aimed. I know you can get public wifi in may places but where he is going maybe not. Actually ATT has pissed us off and we are about to get Hughesnet - I think. Maybe I can talk to the installer about that. The only problem I have with Hughesnet is that they got this promotional rate, right ? Well they can\'t tell me what the rate is after the promotional period. They might reveal it because I\'ll say \"OK then, so after each year I quit you, you come and get your MODEM and dish, and then come back and put it all back up, right ? But then we\'ll burn that bridge when we come to it.
All the admonishments about building a charger seem to be about overcharging. That is apparently the absolute worst thing you can do to these batteries. Well I know how to prevent that. So let\'s have a little bit of a vote of confidence here. It simply is not that difficult.
I know just about enough to be scared. I read that a Tesla battery is
11 modules each 9-cells tall in series ~400V. No idea which battery it
is, but bear with me...
For Leaf:
48x 12\"x9\"x2\"
For Tesla:
7000x 18650 for model S/X, 21700 for model 3, 50800 (estimate) for future?
First 2 digits for diameter (in mm), next 2 for height.
In a 400V pack, the difference between a cell that\'s at zero and one
that\'s at full charge is about 1% of the total voltage. You do not want
to overcharge a cell. You don\'t want to undercharge a cell. The terminal
voltage of the pack is INADEQUATE to manage the system.
For Leaf, it shunt off cells with higher voltage with a 400 ohm resistor during charging. The battery controller expects cells to be closely matched.. There are problems with strong and weak cells. When there are strong cells, it will limit peak charging voltage. When there are weak cells, the controller will disable the battery system prematurely.
Tesla might have a better BMS, since they learned from the Leaf.
If one of the cells in a parallel combination gets slightly higher resistance,
the other cells in that combination will overcharge relative to the
other 10 modules and the effect is cumulative.
No, the parallel cells will all get the same voltage. It\'s the serial combination causing cells to overcharge/discharge.
> Unless you purchase a NEW pack, the pack will have been decommissioned for some unknown reason.
For the Leaf, poor BMS is one reason.
> It takes considerable care to keep the pack balanced. How much of that is in the pack itself and how much is in the charger is unknown.
Balancing has to be done in the pack.
> You probably won\'t find documentation on the protection management.
The Leaf battery system has been reverse engineered to death.
Look up \"balance charger\" to see the lengths the model car guys go to
use lithium batteries.
Even if ALL the protection/balance management is inside the pack, you
still have a charging problem. A solar panel is basically a current
source over much of the insolation range where you want to operate it.
MPPT tries to maximize power transfer, and that happens at the knee
of the curve.
Chargers designed for on-grid use depend on a stable voltage over a wide
range of current. It\'s not a stretch to imagine a limit cycle oscillation
as you try to stuff current into a battery management circuit based on
voltage.
DC/DC converters can help. I am using multiple 5V-12V to 48V boosters to charge my modules.
But i am only charging a small balancing pack, i am still using the main charger with the vehicle.