# How many AH is enough?



## jockepocke (Nov 24, 2009)

Depends on how deep you can discharge your LiFePO4. Your lead-acid batteries should not go beyond 80 %. That leaves 180 Ah that you actually use in your car today. 


I would have bough as much batteries as I could afford  (Doesn't a lower dept of discharge give the cells better life span? )


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## dimitri (May 16, 2008)

F16bmathis said:


> Does anyone know the math for that?


Since Puekert eats about half of your 20 hour rate, you actually have about 120AH -150AH of useful capacity. The key question is how much battery current you typically pull during accelerations and normal cruising? You want to size your LFP cells for approx 1C cruising and 3C acceleration or better to ensure their long and happy life. I would recommend at least 160AH cells for you, although it would give you more range than you need, but its not all that bad  . Then, you need to decide on how many cells to get for final pack voltage, which largely depends on your charger and controller, unless you want to change those too. Since you are getting more range than you need, you can actually go lower on your voltage and save $$$ on extra cells, but then again, you need to figure out your charger situation.

If you list your controller and charger models I can narrow it down.

Hope this helps.


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## dexion (Aug 22, 2009)

What I am finding is that the la range is about 55% of the 20 hour amp rate for an ev. For instance I had 12 105ah batteries in my saturn and was able to do 30 miles with it (no heat at that time.) I should be able to do about 50-60 miles with 100AH lifepo4's which seems to be correct I have about a 55 mile range to roughly 20% soc. So factor in the lower weight and more usable (per actual reported ah lifepo's have a much smaller Puekert effect) power you really might be able to get away with 120AH cells. BUT, you cant pull as much out of them on acceleration as with LA cells. So you should bump it up to 160's (4C on 160= 640 BATTERY amps max if sky energy cells) so you can accelerate. Plus, you get more range than you need which isnt a bad thing. So 43 160 amp hour cells.


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## F16bmathis (Jun 6, 2008)

I have the Zilla 1K and a Manzanita 20 charger. I have the Zilla set to 500 amps (battery current?) and will hit 500A accelerating. I usually drive to 65mph, coast to 55mph, then accelerate back to 65. Seems to work great and give the batteries a resting period. Plus I think keeping the motor running at a constant speed is just burning off amps. Accelerate or nothing!

I was looking to get 45 100AH Thundersky's based on an El-Camino conversion here in Wisconsin. The guy says he gets a 200 mile range with his 200AH and I believe he's running at 144V, he does have a Curtis 500 A controller he modified to run at 650. But I think his estimate is off by about 100 plus miles.


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## dimitri (May 16, 2008)

Pulling 500 amps from 100AH cells on regular basis will put them in early grave, you need 160AH cells for that.

Since you have adjustable charger and controller, you are all set, just need to decide between 40 and 45 cells to roughly match your previous system voltage for comparable performance.

Hope this helps.


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## F16bmathis (Jun 6, 2008)

I converted a Ford Probe using a 48V Forklift motor, my used Curtis 1231C 500A controller, and 12- 12V Trojan something or others. The thing goes fast! Tried to sell it as I have the S10, but the bidding didn't get past $3000. I'm thinking of pulling the parts and getting the darn thing out of my way. The S10 is all I really need.


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## F16bmathis (Jun 6, 2008)

Thanks, guess I'll wait and get some 200Ah's then.


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## Tesseract (Sep 27, 2008)

F16bmathis said:


> I have the Zilla 1K and a Manzanita 20 charger. I have the Zilla set to 500 amps (battery current?) and will hit 500A accelerating.


Good question... is this 500A while accelerating battery current or motor current? Battery current determines RANGE while motor current determines TORQUE (acceleration). 




F16bmathis said:


> Plus I think keeping the motor running at a constant speed is just burning off amps. Accelerate or nothing!


Not following you on this one... driving at a constant speed - even if that speed is 1mph - requires power. Accelerating requires even more power on top of what is necessary to maintain a given constant speed. And faster constant speeds require more power to maintain because of wind resistance. So, no free lunch ever, of course.




F16bmathis said:


> I was looking to get 45 100AH Thundersky's


Then that's approximately 14.4kWh of capacity (45 x 100 x 3.2) which will get you somewhere between 32 and 55 miles of range depending on how fast you drive and how hard you accelerate.




F16bmathis said:


> The guy says he gets a 200 mile range with his 200AH and I believe he's running at 144V, he does have a Curtis 500 A controller he modified to run at 650. But I think his estimate is off by about 100 plus miles.


I'm inclined to agree with you, as 200Ah x 3.2V x 45 cells is closer to 100 miles in real-world range.

For example, Rebirth Auto was contracted to convert a bunch of New Beetles for a customer in the Netherlands and they wanted to be able to go 100miles at 75MPH. Well, they started off with 60 TS-160Ah cells and could go about 80 miles at 75MPH. This would imply they need 75 cells to get to 100 miles, but they can only fit in 5 more cells without ripping out the back seats so they and the customer compromised (granted, just by reducing the speed to 65mph they should hit 100 miles of range).

BTW - that's a calculated power consumption of 384Wh/mi, which seems consistent for most modern "aerodynamic" vehicles when driven at "real" highway speeds (70-75mph).

Hope this helps you out.


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## F16bmathis (Jun 6, 2008)

I have my Zilla set up at 500 battery amps. When it was at 1000 amps, the pedal was very sensitive, but I could easily outrun most other cars.

I found that I can get better range by accelerating to speed (65), then coasting down to 55-60 and accelerating up to 65 again. Holding the S10 at 65 kills my mileage. I guess its like driving my wifes car. Normal driving gets about 33 mpg, while accelerating to 65 then tossing it in nuetral and coasting down to 55, I can get closer to 40mpg.

As far as the batteries goes, I'll have to go with 200AH, but I'll have to wait till they come down in price.


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## jockepocke (Nov 24, 2009)

F16bmathis said:


> I have my Zilla set up at 500 battery amps. When it was at 1000 amps, the pedal was very sensitive, but I could easily outrun most other cars.
> 
> I found that I can get better range by accelerating to speed (65), then coasting down to 55-60 and accelerating up to 65 again. Holding the S10 at 65 kills my mileage. I guess its like driving my wifes car. Normal driving gets about 33 mpg, while accelerating to 65 then tossing it in nuetral and coasting down to 55, I can get closer to 40mpg.
> 
> As far as the batteries goes, I'll have to go with 200AH, but I'll have to wait till they come down in price.


Yes, of course you will have a better range when you are accelerating to 65 and then let your speed drop to 55, then go up to 65 again. You average speed will be much lower than 65 in that case, so of course an average speed of 65 mph will crave higher amps (more air drag etc).


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## Lordwacky (Jan 28, 2009)

Tesseract said:


> FRebirth Auto was contracted to convert a bunch of New Beetles for a customer in the Netherlands and they wanted to be able to go 100miles at 75MPH. Well, they started off with 60 TS-160Ah cells and could go about 80 miles at 75MPH. This would imply they need 75 cells to get to 100 miles, but they can only fit in 5 more cells without ripping out the back seats so they and the customer compromised (granted, just by reducing the speed to 65mph they should hit 100 miles of range).


I thought the new TS 200ahr batteries are the same form factor as the 160ahr batteries? If that is the case you should be able to the get to original range/speed requirement by using those cells. It'll cost you a bit of a weight penalty though. Congrats on your contract, sounds awesome.


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## icec0o1 (Sep 3, 2009)

F16bmathis said:


> I have my Zilla set up at 500 battery amps. When it was at 1000 amps, the pedal was very sensitive, but I could easily outrun most other cars.
> 
> I found that I can get better range by accelerating to speed (65), then coasting down to 55-60 and accelerating up to 65 again. Holding the S10 at 65 kills my mileage. I guess its like driving my wifes car. Normal driving gets about 33 mpg, while accelerating to 65 then tossing it in nuetral and coasting down to 55, I can get closer to 40mpg.
> 
> As far as the batteries goes, I'll have to go with 200AH, but I'll have to wait till they come down in price.


You'll get the same mpg if you hold at 60mph, which is the average of accelerating to 65 then coasting to 55. Keeping it at 65 would mean accelerating to 70 and coasting to 60.


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## Tesseract (Sep 27, 2008)

Lordwacky said:


> I thought the new TS 200ahr batteries are the same form factor as the 160ahr batteries?...


Hey LW... The 200Ah cells they have now are significantly larger than the 160Ah... I think it's the new 180Ah cells that are supposed to be the same, or similar in, physical size as the 160s?

Thanks for reminding me, though, that there might be an intermediate solution that isn't so painful. Those 200Ah cells are really awkwardly shaped beasts.


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## EVComponents (Apr 20, 2009)

Tesseract said:


> Hey LW... The 200Ah cells they have now are significantly larger than the 160Ah... I think it's the new 180Ah cells that are supposed to be the same, or similar in, physical size as the 160s?
> 
> Thanks for reminding me, though, that there might be an intermediate solution that isn't so painful. Those 200Ah cells are really awkwardly shaped beasts.


At Rebirth Auto you are dealing with old cells in the TS 200 AH size. 
The new 200 AH size is the same case as the 160 AH. 

You must be buying from someone that is giving you their obsolete leftovers.

The ThunderSky 160 Ah, 180 Ah and 200 Ah cells all are available in the same size case.


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## MN Driver (Sep 29, 2009)

EVComponents said:


> At Rebirth Auto you are dealing with old cells in the TS 200 AH size.
> The new 200 AH size is the same case as the 160 AH.
> 
> You must be buying from someone that is giving you their obsolete leftovers.
> ...


When do you figure TS will update their site? 

They show(as of today 12/27/09):
MODEL NO:TS-LFP160AHA
Nominal Capacity:160AH
Operating Voltage:2.5V~4.25V
weight:5.6kg±100g
Dimensions:209×280×65(mm)

MODEL NO:TS-LFP200AHA
Nominal Capacity :200AH
Operating Voltage:2.5V~4.25V
weight:7.3kg±100g
Dimensions:360.6×256.4×55.5(mm)
------
The 200Ah cell spec must be way out of date, 7.3kg vs 6kg and the old 160Ah spec is showing even larger on two dimensions compared to the new spec of 182x279x70.6(mm) on your site.


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## EVComponents (Apr 20, 2009)

That is because ThunderSky does not advertise the new size because of limited quantities. They are still pushing the old monster size when people order the 200 AH cell.

In fact, at one point TS asked us to reduce the quantities that we are ordering because they could not fill all of the the new size 200 AH orders that we were requesting.

We have a bunch of them in the warehouse now in the container that just arrived. 100% sold out.


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## MJ Monterey (Aug 20, 2009)

Wow, that new cell cuts the space volume on 200ah cells by 1/3, or the power density of the 160 cells has increased by 20%. Just wow!

James, is TS pushing to standardize their production on the 160ah size enclosure? Do you see a standard enclosure developing between manufacturers?


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## EVComponents (Apr 20, 2009)

MJ Monterey said:


> James, is TS pushing to standardize their production on the 160ah size enclosure? Do you see a standard enclosure developing between manufacturers?


I don't see standards between manufacturers. Sky Energy and ThunderSky have differences in their case sizes, even when they have equivalent AH products. Both have the 40 Ah, 60 Ah and 100 AH size. But they all have different dimensions. They are close, but off by several mm. 

They are too competitive with each other to work together on standards.

I think it is just a natural progression as they improve their product.
The TS 100 AH cell is in the same case as the TS 90 AH cell.
The TS 160 AH, 180 AH and 200 AH cell are now all available in the same case.

I think that the TS 300 AH cell is going to be available in the same case as that currently used by the TS 260 AH.

These are all moving targets. It seems to change every 3-6 months.


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## MJ Monterey (Aug 20, 2009)

EVComponents said:


> These are all moving targets. It seems to change every 3-6 months.


Thanks James. Change is good it means progress on the battery front.

It's just my personal challenge that I am thinking/designing for a project 2 years out with a key component changing, in a good way, every 3 months.

Jack


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## F16bmathis (Jun 6, 2008)

icec0o1 said:


> You'll get the same mpg if you hold at 60mph, which is the average of accelerating to 65 then coasting to 55. Keeping it at 65 would mean accelerating to 70 and coasting to 60.


You'd think it would, but it doesn't. Starting at a full charge and driving a constant 55mph, gets less distance than going 65, coasting to 55, and repeating during the entire drive. I've heard the batteries like to have discharge and rest cycles. It could be the hills also. At 55 as I enter a hill, it uses the full pedal travel, and one hill I'll slow to 50 before peaking it. Driving at 65+ gets me over those hills at 65. 

My thoughts are, and they can be very wrong, are... Say you are going 55. You are going downhill slightly, enough where if you were in nuetral, you'd still be going 55 for a time. If you are in gear and stepping on the pedal, you're just wasting juice. Same theory works for a level surface. Unless you are actually accelerating, I get more range by coasting. Just maintaining speed uses more juice than if you were putting some power to the road. Plus my batteries get a break!

I base all the above on 3600 miles of highway driving. At a constant 55, plus coasting where I can, I can barely make it 40 miles. (20 to work, 20 home) At 65 & coasting, I can make it 40 miles plus another 5-10 after work.


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## EVComponents (Apr 20, 2009)

MJ Monterey said:


> Thanks James. Change is good it means progress on the battery front.
> 
> It's just my personal challenge that I am thinking/designing for a project 2 years out with a key component changing, in a good way, every 3 months.


ThunderSky does try to keep the case sizes consistent as they improve. 
90 --> 100
160 --> 200
260 --> 300

So if anyone ever upgrades their EV or other application, the new replacement cell will fit and be more energy dense.


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## Duxuk (Jul 11, 2009)

There is some danger in comparing the fuel consumption of an ICE with the energy use in an electric motor. ICEs are most efficint at converting chemical energy in the fuel to motive force when at full throttle due, mainly to less drag in the inlet tract with the choke wide open (plus several toher factors of course). An electric motor is less efficient if it is worked hard such as up a steep hill because it will produce more heat, which is wasted energy. Also remember that accelerating wastes little energy but braking creates heat in the brakes which is lost to the enviroment. So DON'T BRAKE!!!!!!!!!!!!!!!!!!!!!!


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