280AH Lithium Battery

[solarman]

I wonder why they normally rate LifePO4 batteries in AH but rate EV batteries in KWH.

But at least the math is simple. 300AH times 13.6 volts =4.080 KWHs.

-Don- Reno, NV

Watts are a measure of power and work, Amps are meaningless unless one knows the voltage.
in the solar world, we always specify power draw in Watts and required battery capacity in Watt/hr or kW/hrs. capacity and voltage are established when loads are known.

in the EV world, it's a universally accepted measure so there is no confusion when a battery is 2000 W/hr and a motor is 500 Watts therfore one can deduce the anticipated runtime.

 

[DonTom]

Watts are a measure of power and work, Amps are meaningless unless one knows the voltage.
in the solar world, we always specify power draw in Watts and required battery capacity in Watt/hr or kW/hrs. capacity and voltage are established when loads are known.

in the EV world, it's a universally accepted measure so there is no confusion when a battery is 2000 W/hr and a motor is 500 Watts therfore one can deduce the anticipated runtime.

Yes, of course. But there is a little more to it, IMO.

EV AC charge stations are usually rated in amps but the EV AC input charger (which is inside the EV)is usually rated in KW. IOW, I have a 12 KW charger in my Tesla which requires 48 amps at 240 VAC to get anything near 12 KW. So then it is 240VAC times 48 amps=11,520 watts (close enough).

So why do they not simply rate both in KW?

One possible reasonable answer is that this makes the electrician's job easier. They now know what gauge and fuse to use, which MUST be rated in amps, without doing any math. IOW, 32 amps is 32 amps. 48 amps is 48 amps. They do not need to know anything else, such as the voltage or wattage, since neither fuses nor wire gauges can be determined by watts alone. Or by voltage alone. Knowing the amps is all they need.

Imagine how complicated it could get if we tried to rate fuses any other way other than in amps. I know fuses also have a voltage rating but is not used to determine watts, but for fire safety and this voltage rating only comes into play when the fuse blows.

So then the owners get stuck with the math. Not a big deal, but it does kinda explain why things are this way. There is no way to rate a fuse or wire gauge in watts, so this does make some sense.

Besides this, EV owners usually do NOT need to know. Just plug into a J-1772 or a Tesla Destinaion charge station which are NOT chargers at all. They are just AC charge stations BUT with a pilot signal and many extra safety features. It's perfectly safe to charge on a pouring rainy day and tripping any ground faults is unlikely (I never even heard of it happening on an AC EV charge station, but I hear it too is possible).

The "pilot signal" originates in the charge station and is sent to the EV to tell the EV charger to reduce its wattage to a little below what the charge station is capable of. IOW, it is possible to use a 12KW EV charger on a charge station that is only capable of 3KW without overloading. But it will then be charging at 3 KW instead of the 12 KW the EV charger is capable of.

But EV owners do NOT need to know this stuff, they just wonder why it's taking so much longer to charge up than at the same type (as far as looks go) charge station at a different location they used last week or whenever. The amp ratings of 240 (sometimes 208 VAC in the field because of industrial 3-phase stuff nearby) AC EV charge stations are as low as 13 amps (~3 KW) to as high as 70 amps (~17KW). The extra high AC amp charge rates are for the very old Teslas when we didn't have nearly as many Supercharges as today. Still some in service today, but I can only use them at 12 KW.

The display says 15 hours to full instead of the three hours it took last week at a different location. Many EV owners simply call them fast and slow "chargers" even though they are NOT chargers at all. These slow AC charge stations are not used much on long trips but are handy to add a few miles when at a store or restaurant or whatever. Or at a Reno casino. And countless other places. They are normally free to use anywhere in the Reno area which has many of them.

-Don- Reno, NV

 

[John From Detroit]

I wonder why they normally rate LifePO4 batteries in AH but rate EV batteries in KWH.

Very good question but I suspect it's to hide the voltage of the EV battery-OR- Because KWH is what the motors eat.

 

[Viajeros]

Yes, of course. But there is a little more to it, IMO.

EV AC charge stations are usually rated in amps but the EV AC input charger (which is inside the EV)is usually rated in KW. IOW, I have a 12 KW charger in my Tesla which requires 48 amps at 240 VAC to get anything near 12 KW. So then it is 240VAC times 48 amps=11,520 watts (close enough).

So why do they not simply rate both in KW?

One possible reasonable answer is that this makes the electrician's job easier. They now know what gauge and fuse to use, which MUST be rated in amps, without doing any math. IOW, 32 amps is 32 amps. 48 amps is 48 amps. They do not need to know anything else, such as the voltage or wattage, since neither fuses nor wire gauges can be determined by watts alone. Or by voltage alone. Knowing the amps is all they need.

Imagine how complicated it could get if we tried to rate fuses any other way other than in amps. I know fuses also have a voltage rating but is not used to determine watts, but for fire safety and this voltage rating only comes into play when the fuse blows.

So then the owners get stuck with the math. Not a big deal, but it does kinda explain why things are this way. There is no way to rate a fuse or wire gauge in watts, so this does make some sense.

Besides this, EV owners usually do NOT need to know. Just plug into a J-1772 or a Tesla Destinaion charge station which are NOT chargers at all. They are just AC charge stations BUT with a pilot signal and many extra safety features. It's perfectly safe to charge on a pouring rainy day and tripping any ground faults is unlikely (I never even heard of it happening on an AC EV charge station, but I hear it too is possible).

The "pilot signal" originates in the charge station and is sent to the EV to tell the EV charger to reduce its wattage to a little below what the charge station is capable of. IOW, it is possible to use a 12KW EV charger on a charge station that is only capable of 3KW without overloading. But it will then be charging at 3 KW instead of the 12 KW the EV charger is capable of.

But EV owners do NOT need to know this stuff, they just wonder why it's taking so much longer to charge up than at the same type (as far as looks go) charge station at a different location they used last week or whenever. The amp ratings of 240 (sometimes 208 VAC in the field because of industrial 3-phase stuff nearby) AC EV charge stations are as low as 13 amps (~3 KW) to as high as 70 amps (~17KW). The extra high AC amp charge rates are for the very old Teslas when we didn't have nearly as many Supercharges as today. Still some in service today, but I can only use them at 12 KW.

The display says 15 hours to full instead of the three hours it took last week at a different location. Many EV owners simply call them fast and slow "chargers" even though they are NOT chargers at all. These slow AC charge stations are not used much on long trips but are handy to add a few miles when at a store or restaurant or whatever. Or at a Reno casino. And countless other places. They are normally free to use anywhere in the Reno area which has many of them.

-Don- Reno, NV

Good post. Informative.

 

[solarman]

Yes, of course. But there is a little more to it, IMO.

EV AC charge stations are usually rated in amps but the EV AC input charger (which is inside the EV)is usually rated in KW. IOW, I have a 12 KW charger in my Tesla which requires 48 amps at 240 VAC to get anything near 12 KW. So then it is 240VAC times 48 amps=11,520 watts (close enough).

So why do they not simply rate both in KW?

One possible reasonable answer is that this makes the electrician's job easier. They now know what gauge and fuse to use, which MUST be rated in amps, without doing any math. IOW, 32 amps is 32 amps. 48 amps is 48 amps. They do not need to know anything else, such as the voltage or wattage, since neither fuses nor wire gauges can be determined by watts alone. Or by voltage alone. Knowing the amps is all they need.

I agree, Amps would be common sense for fuse and wiring specifications.

Watts or kW would be a better unit for charging stations

Imagine how complicated it could get if we tried to rate fuses any other way other than in amps. I know fuses also have a voltage rating but is not used to determine watts, but for fire safety and this voltage rating only comes into play when the fuse blows.

So then the owners get stuck with the math. Not a big deal, but it does kinda explain why things are this way. There is no way to rate a fuse or wire gauge in watts, so this does make some sense.

Besides this, EV owners usually do NOT need to know. Just plug into a J-1772 or a Tesla Destinaion charge station which are NOT chargers at all. They are just AC charge stations BUT with a pilot signal and many extra safety features. It's perfectly safe to charge on a pouring rainy day and tripping any ground faults is unlikely (I never even heard of it happening on an AC EV charge station, but I hear it too is possible).

with a few exceptions, I'd say most EV owners have no clue or even need or want to know voltage or amperage..

The "pilot signal" originates in the charge station and is sent to the EV to tell the EV charger to reduce its wattage to a little below what the charge station is capable of. IOW, it is possible to use a 12KW EV charger on a charge station that is only capable of 3KW without overloading. But it will then be charging at 3 KW instead of the 12 KW the EV charger is capable of.

But EV owners do NOT need to know this stuff, they just wonder why it's taking so much longer to charge up than at the same type (as far as looks go) charge station at a different location they used last week or whenever. The amp ratings of 240 (sometimes 208 VAC in the field because of industrial 3-phase stuff nearby) AC EV charge stations are as low as 13 amps (~3 KW) to as high as 70 amps (~17KW). The extra high AC amp charge rates are for the very old Teslas when we didn't have nearly as many Supercharges as today. Still some in service today, but I can only use them at 12 KW.

The display says 15 hours to full instead of the three hours it took last week at a different location. Many EV owners simply call them fast and slow "chargers" even though they are NOT chargers at all. These slow AC charge stations are not used much on long trips but are handy to add a few miles when at a store or restaurant or whatever. Or at a Reno casino. And countless other places. They are normally free to use anywhere in the Reno area which has many of them.

-Don- Reno, NV

 

[DonTom]

Watts or kW would be a better unit for charging stations

I also would prefer them to use watts and for a couple of reasons. One of them is because sometimes the voltage of the AC charge station in the field is only 208 volts AC. But most often is 240 VAC. So to know the wattage, I need to measure the voltage as NONE of the AC charge stations know what voltage they are being used at, so they do not say on their label (which is usually on the side of the charge stations but only shows amps).

On my two older electric motorcycles, I added a way to use external chargers, and I can charge at or above the full capacity of many AC charge stations as they ignore the pilot signal. So I must adjust them manually by using one, two or three chargers. I added a switch to turn off the OBC (1.4 KW On Board Charger) as necessary to prevent overloads. I can often charge my little motorcycle battery at a higher rate than ANY car. I can charge my 2017 Zero motorcycles as high as 1C. "C" is measured in amps, but it comes out very close to the KWH capacity of the battery. IOW, at 1C a 10 KWH battery can usually be charged at 10KW max. Easy to figure when watts are used. If 2C, then a 10 KWH battery can be charged at 20KW.

7 KWH battery on my smallest electric motorcycle and around 16 KWH on my largest. So even when I see the amperage rating on the charge station, I sometimes need to guess if they are using 208 or 240 VAC--or measure it, which I have also done, as I do have a way to activate these stations before I use them.

So yeah, the wattage rating would be a lot better for me with my two oldest electric motorcycles which ignore the pilot signal when I use my homebrew charger setup. My 2017 Zero SR motorcycle is designed for a long overnight charge, using the OBC at just 1.4 KW. I sometimes use this bike for trips of hundreds of miles and waiting more than ten hours for a charge is not anything near reasonable. I charge it as high as 8 KW on the road with my homebrew charger setup.

I bought these external chargers at Elcon in Sacramento and one of the techs their knew how to program them for my 2017 electric motorcycles. He also owns an electric motorcycle and I have since done rides with him.

-Don- Reno, NV

 

[DonTom]

Watts or kW would be a better unit for charging stations

The amps ratings are only for the AC charge stations. They never say the wattage.

However, DCFCs (DC Fast Chargers) always are rated in watts. So now it matches both ends and most charging for longer trips is from DCFC. This type of charging bypasses the EV charger and goes directly to the battery.

The slow AC input charging is mainly for home charging and for when at restaurants and shopping or whatever, just to get perhaps 45 miles of range added every hour of car charging. Often for free, especially here in the Reno area, where the restaurant, casinos shopping malls and often even motels pay for it and usually (but not always) let non-customers use them. But at these charge stations, some of my motorcycles can add three times that range in the same charging time, ~135 miles of range added in an hour. That is useful even on longer trips, as I enjoy the longer breaks every couple of hours of riding or so.

You say solar uses watts, great. But why do they use AH instead of KWH for the battery the solar is charging? Not that it is a big deal for those who know the basics of Ohm's Law. But probably most RV owners do not.

BTW, on a normal sunny day at a fairly normal temp , how much power in watts should I expect from a decent 100W solar panel? I assume the 100 watts would be very rare and will only last for a few minutes on a perfect day.

-Don- Reno, NV

 

[DonTom]

with a few exceptions, I'd say most EV owners have no clue or even need or want to know voltage or amperage..

Yeah, but in both of my EV cars that info shows right on the screen, in both amps and KW while charging. IIRC, they also show the charging voltage.

I can even do that on my Zero motorcycles but then I need to use a Smartphone with Bluetooth to get the info. On my Enegica motorcycles is shows the charging watts right on the screen.

All EVs show the time it takes to get to a full charge in hours. But . . . It is NEVER accurate. It will always be a bit longer to get to the full charge. That is because the time to get to full, is calculated by the current charge rate which decreases as the battery gets more charged.

-Don- Reno, NV

 

[John From Detroit]

Though I don't know how the charge stations are designed or the vehicle side either from what some are saying it is a two part system the charger will not output more than it can (After all circuit breakers limit) and the Vehicle will not accept overly fast..they "Chat" to set it up. Makes sense.

With modern systems it's almost like Charlotte my robo-maid. If she forgets how to chat with my router.. The phone app links to her with Blue Tooth.. and reminds her (With some button pushing on my part) Then the wi-fi side of the app can .. "Turn her On" (That sounds NSFW but well... She is a machine)

She also has a charging station.. Not sure how she finds it but guessing Blue Tooth I do know she can find it.

 

[DonTom]

will not output more than it can (After all circuit breakers limit)

I have deliberately gone over the capacity of J-1772 AC stations to see what will happen. Say it's a 7.2 KW J-1772 (30-amp, very common)and I draw 7.3 KW from it. The 7.2 KW charge stn will then say it is charging at 7.3 KW and continues to work perfectly. I charge a little higher than that, say 7.7 KW, the machine shuts down and I get an email (from ChargePoint--the only charge stations I have tried this on) that says I have possible trouble with my EV and the machine has shut down to prevent the CB from blowing. As soon as I remove my load the same charge station can be used again.

I just now found such an old email:

"Dear Donald, The station at which your vehicle is charging, CAPITAL PLAZA /
STATION 1, has detected that your vehicle is drawing more current than the
station's rating, and has suspended charging to prevent the circuit
breaker from tripping. This typically indicates an issue with configuration
of the vehicle or an issue with the battery management system on the
vehicle. Please contact the manufacturer of the vehicle if you receive this
notification again.
Team ChargePoint"

So as you can see, the AC EV charge station will shut down automatically to prevent the CB from turning off the power.

In reality, in a stock EV, this should never happen. The Control Pilot signal from the charge station will lower the EV charger (the real charger, located inside the EV) wattage to below the charge station's rating. The Control Pilot is a 1 kHz PWM at ±12 volts and sets the EV charger just below the charge station's capacity.

But when I use my external after-market (fork-lift chargers, but programmed for my bike battery) to charge my 2017 Zero motorcycles, the control pilot is not connected so the charge station cannot lower my charge rate, so I can overload it with my chargers--something a stock EV charging system cannot do. But I can manually adjust my charge rate by not using one of my external chargers. I can charge as low as 1.4 KW and as high as 8KW when on the road, with several steps in between. I can also use two J-1772's at the same time and then I can always charge at 8KW. I carry the extra J-1772 adapter for when I want to charge at 8KW, where they have two plugs available. Then my motorcycle charges at a higher rate from these charge stations than can any EV car.

-Don- Reno, NV

 

[rvlifer]

I prefer the old days when computers didnt address you by name

 

[solarman]

You say solar uses watts, great. But why do they use AH instead of KWH for the battery the solar is charging? Not that it is a big deal for those who know the basics of Ohm's Law. But probably most RV owners do not.

I think most users want to be able to relate capacity to how long the battery(s) will support a load for a specific amount of time, typically hours or a portion of an hour. Having the capacity stated in Amp/hrs, just makes it easy to figure out, most people can calculate the result in their head and get a pretty good estimate. Amp hour capacity has become a standard and also helps in making comparisons for equivalent voltage and battery types, or to figure out which battery to select for a specific task, typically associated with a time period that is needed for the load to do the task. It could be done in Coulombs, but that would just make life more complicated. !!

Amps is just a measure of charge, kWh is a measure of capacity. when designing solar, the standard is to use watts for all loads and Watt hours ( or kWh ) for capacity, when the total figure is established, it's then a simple matter to calculate the required battery size based on power load and voltage.

also, I'm not aware of any standard voltage for EV batteries, every manufacturer is different, so EV's are defined in kWh, I think most people can relate to the difference of a vehicle that has a 75 kWh or 100 kWh battery without knowing the voltage. It's also the standard unit for purchasing power from the grid, so people are familiar with the units.

BTW, on a normal sunny day at a fairly normal temp , how much power in watts should I expect from a decent 100W solar panel? I assume the 100 watts would be very rare and will only last for a few minutes on a perfect day.

-Don- Reno, NV

a typical panel in strong sunlight on a clear day at solar noon should produce greater than 95% of it's rated output until it heats up. Temperature is your enemy here, output drops as the panel heats up.

STC or standard test conditions are measured at 25 degrees Celcius and 1000 Watts per square meter.
those conditions don't exist for long even in the peak of summer.

A panel CAN produce more than it's rated output under certain conditions.
Those conditions do exist in certain climates, dessert is one, a panel that is cold from overnight low temps illuminated by strong sun moving out of a shadow will potentially generate as much as 120% output for a short time until it heats up. (That and the increased Voc/Vmpp has to be considered in any design also)

 

[DonTom]

Amps is just a measure of charge, kWh is a measure of capacity.

But AH is a measurement of capacity just as is KWH.

Amps is a measurement of the charge current or drain current in or out of the battery and tells us nothing about the capacity of the battery. At least not until the battery blows up from too many amps!

BTW, I think your explanation on EV batteries is correct, for everything other than the AC charge stations that are always rated in amps. But it makes no difference if one looks at their EV screen and see the amps as well as the KW rate. Even the voltage. Telsa shows it like this on the very bottom of the screen as soon as a charge cable is connected::

a typical panel in strong sunlight on a clear day at solar noon should produce greater than 95% of it's rated output until it heats up.

I wonder why I was only getting around 55% max when I was in OPCNM with my 100-watt solar setup on the ground pointed directly at the sun on a mild day. I cannot remember the make and model of my solar right now, I will have to get back to Auburn to check, which will be in a few days. I did remove the PWM controller and put it on an MPPT control which has a setting for my (300-AH) Lifep04 battery. Same Ampertime 300-AH battery in each of my motorhomes.

STC or standard test conditions are measured at 25 degrees Celcius

Does that mean 25°C (77°F) is the perfect temp for solar and the output drops if much hotter or cooler than that? In OPCNM when I was there last month, I think the daytime high was just a little below that. Comfortable, whatever it was.

I know the output drops when they are too hot and I assume the same for when too cold. But I know little about solar. I am only a user--and not all that often. Don't you own a solar shop or something like that?

I had no idea that solar can do 120% under perfect conditions. I assumed they were rated in the very max possible and this was difficult to get on any day.

-Don- Reno, NV

 

[John From Detroit]

Then my motorcycle charges at a higher rate from these charge stations than can any EV car.

Copied text just so folks can look back.
Thanks.that's a bit better than I thought they worked... But you did a good job of explaining the built in safety and limiters. Sound well designed.

 

[DonTom]

Sound well designed.

Yes, it was well thought out for J-1772. But Tesla was able to improve the charging in every possible way, connector and all. But the basics are exactly the same, for an example, the Tesla Destination chargers and Tesla Wall connectors also use the same type of control pilot. But from a smaller and lighter connector that can handle even more power than the J-1772. That is why Tesla won the war to become the charging standard in the USA and I assume for the entire world someday.

-Don- Reno, NV

 

[solarman]

I wonder why I was only getting around 55% max when I was in OPCNM with my 100-watt solar setup on the ground pointed directly at the sun on a mild day. I cannot remember the make and model of my solar right now, I will have to get back to Auburn to check, which will be in a few days. I did remove the PWM controller and put it on an MPPT control which has a setting for my (300-AH) Lifep04 battery. Same Ampertime 300-AH battery in each of my motorhomes.

Reasons I can think of.
1) the winter sun is not as intense, irradiance is much less even though clear blue skies suggest otherwise.
2) your battery was in a high SOC and therefore did not accept or need a high charge.
3) a PWM controller will always be less efficient than an MPPT type.

Does that mean 25°C (77°F) is the perfect temp for solar and the output drops if much hotter or cooler than that? In OPCNM when I was there last month, I think the daytime high was just a little below that. Comfortable, whatever it was.

25C is the optimal temperature for output and is used for the STC test. hotter temps reduce output, if you examine a panel's specification sheet you will see a temperature coefficient.. this is the amount per degree Celcius that the output drops by. Colder temps actually increase output up to a certain point.

the other test that is more pertinant, especially in the US is the PTC test, it refers to the "PVUSA Test conditions"

PTC uses a temperature of 20 Celsius combined with a calculation to measure module performance.

The PTC formula was developed by a California-based solar research and development partnership between the US Department of Energy and several major utilities. This group was established in 1986 and was known as Photovoltaics for Utility Scale Applications (PVUSA). They merged with the California Energy Commission in 1997 and ultimately dissolved in 2000. Although PVUSA no longer exists, their method of rating module performance was found to be more accurate than the STC rating system and is still in use today.
The PTC system collects data on a module’s power output for a designated period of time under conditions of 1,000 Watts per square meter solar irradiance, 20° Celsius air temperature, and a wind speed of one meter per second at 10 meters above ground level. The cell temperature is combined with the temperature coefficient of power to measure the voltage change in the cell relative to the temperature change.

I know the output drops when they are too hot and I assume the same for when too cold. But I know little about solar. I am only a user--and not all that often. Don't you own a solar shop or something like that?

I'm a retired professional engineer, been designing off grid solar and SCADA systems for the last 20yrs
mainly for large oil companies, but also a range of other installations such as telecom, remote monitoring stations and well pumps.

I had no idea that solar can do 120% under perfect conditions. I assumed they were rated in the very max possible and this was difficult to get on any day.

-Don- Reno, NV

yes, they can but only under very specific conditions and only for a short time as I described in my other post.

 

[DonTom]

yes, they can but only under very specific conditions and only for a short time as I described in my other post.

I just checked to see what my portable solar setup is, It is this one. The 90-watt Samlex Portable Solar Charging Kit.

When I purchased my 2022 Class A new in year 2021, RV Country gave me a thousands bucks of parts from their parts store there in Sparks, NV. That was one of the things I purchased with that deal. But I normally only get a few amps out of it. A little less than 5 amps is the most I have seen on a bright sunny desert day at the controller.

I removed the PWM controller and put on a MPPT controller but no difference from what I can tell, still less than 5 amps output at best or around 65 watts at the very most and that doesn't last long.

-Don- Auburn, CA

 

[rvlifer]

I just checked to see what my portable solar setup is, It is this one. The 90-watt Samlex Portable Solar Charging Kit.

When I purchased my 2022 Class A new in year 2021, RV Country gave me a thousands bucks of parts from their parts store there in Sparks, NV. That was one of the things I purchased with that deal. But I normally only get a few amps out of it. A little less than 5 amps is the most I have seen on a bright sunny desert day at the controller.

I removed the PWM controller and put on a MPPT controller but no difference from what I can tell, still less than 5 amps output at best or around 65 watts at the very most and that doesn't last long.

-Don- Auburn, CA

That is about the same as my 100w portable setup from another company. I get abot 6 1/2 amps in full sun

 

[DonTom]

I get abot 6 1/2 amps in full sun

At what voltage (or wattage)? Mine is used to charge a Lifepo4 battery so my voltage could be higher, but still a little below 65 watts at the very best.

-Don- Auburn, CA

 

[rvlifer]

At what voltage (or wattage)? Mine is used to charge a Lifepo4 battery so my voltage could be higher, but still a little below 65 watts at the very best.

-Don- Auburn, CA

Now that you ask i am not sure whether my charge controller is saying that is coming off the panels or going to the batteries. Not sure what the voltage is from thw panels to the charge controller but obviously 12v to the batteries.

I only ever used mine to plug in and trickle charge the battery bank.