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#### F16bmathis

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I'm doing it! But... I have 225 ah 144V Trojans. So 32.4 KW. How low of an AH can I go with Thundersky's and keep the same range?

I understand I can go lower cause I can discharge them more?

And I just found a site that has HiPower batteries at slightly cheaper than ThunderSky's, Which is better?

Plus, does anyone know how many amps I can pull with those? I don't understand "C" ratings, but would love to pull the 1000 amps the Zilla is cabable of.

#### rillip3

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I'm assuming the Trojans are FLA. If so, of that 32.4, you're only getting half after Peukert. Assuming you are going to keep a 20% Depth of Discharge on both, you would want 125 Ah; I believe they only make 100 and 200, so you'd have to get the 200 to keep the range. You'll get some extra range.

EDIT: This was the OP. As Roughrider pointed out, this is not correct. I'll leave it for historical purposes but see his post below for correct answers.

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1c = the normal, 20 hour ratting, which is used in calculating the size you see on your batteries. So for a 225 Ah battery, it's 1C rating is 11.25 (11.25 x 20 = 225). 1c on a 200 Ah battery is 10 A. You can pull up to 3c safely for a limited period (you'd have to check the specs, but I think it's like 3 minutes), so 30 A per battery. TS tops out at 4c for bursts (< 10s I believe).

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/EDIT

Okay for some better numbers. If you went with 160 (since you need 125) 1c = 160 A. The 3c is still only 480, and even a burst of 5c, which you can do on some lithiums, but not all (check your specs before you try it!!) is only 800 A before Puekert. You still won't top out 1k if you buy the 160 Ah. The 200 you could, if Puekert didn't come into effect. Realistically, with cabling loses, internal resistance, etc. you would probably only get around 800-850 A from the 200's and 640-700 on the 160's.

Not sure about the other brand of batteries.

#### Pirape

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thundersky are making 40ah, 90ah, 100ah, 160ah, 200ah

If you want to keep cost low I suggest you pick lower AH and higher voltage

Less amps = less heat = more distance

#### RoughRider

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I'm assuming the Trojans are FLA. If so, of that 32.4, you're only getting half after Peukert. Assuming you are going to keep a 20% Depth of Discharge on both, you would want 125 Ah; I believe they only make 100 and 200, so you'd have to get the 200 to keep the range. You'll get some extra range.

1c = the normal, 20 hour ratting, which is used in calculating the size you see on your batteries. So for a 225 Ah battery, it's 1C rating is 11.25 (11.25 x 20 = 225). 1c on a 200 Ah battery is 10 A. You can pull up to 3c safely for a limited period (you'd have to check the specs, but I think it's like 3 minutes), so 30 A per battery. TS tops out at 4c for bursts (< 10s I believe).

Not sure about the other brand of batteries.
this seams not right to me...

1C means that you can pull the full capacity in 1hour ==> 1C for a 200Ah battery means 200Amps and not 10A

3C means 600Amps

1000Amps ==> 5C

#### dimitri

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I'm doing it! But... I have 225 ah 144V Trojans. So 32.4 KW. How low of an AH can I go with Thundersky's and keep the same range?

I understand I can go lower cause I can discharge them more?

And I just found a site that has HiPower batteries at slightly cheaper than ThunderSky's, Which is better?

Plus, does anyone know how many amps I can pull with those? I don't understand "C" ratings, but would love to pull the 1000 amps the Zilla is cabable of.
Few issues here:

1. 1000 Zilla amps are motor amps, not battery, plus its only for a few seconds, which is good, or you would blow your motor . Battery amps should be much less and should be limited by Zilla settings, so you don't kill your cells.
2. Theoretically you'd get same range with 100AH Lithium cells, but then you'd be limited to 3C ( rule of thumb ), which is 300 battery amps, which is low for your car.
3. Based on above, I would recommend to go for 200AH ( If you choose HiPower, since they only come in 100AH and 200AH), or at least 160AH Thundersky. This way you can pull more battery amps, 600 for 200AH pack, or 480 for 160AH pack and get more range as a bonus.
4. HiPower now has new 3C cells, their old ones were not so good 1C cells. New cells are very good quality, arguably better than Thundersky, but they are a bit larger and have large terminals. They will be fixing terminal size in future batches, but if you order now you'd probably get cells with large terminals. There is thread about it, search for it.

Hope this helps

#### Lordwacky

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Ok here goes nothing,

as pointed out above. The C rating is the discharge/charge rating for the battery expressed as a function of the batteries energy storage capacity (Ahr rating). So for example thundersky batteries are rated at 4C continious discharge. This means that if you have a 100 Ahr thundersky battery you can discharge continiously at 4(100) = 400amps continious.

You are basicaly asking two different questions in your original post, but you may not realize it.

1) what size of thundersky pack do I need for comparable range?
2) what size pack do I need for my 1000 amp rated controller?

The key thing missing is your desired system voltage. You existing system voltage is 144V so I'm going to assume you have a LV zilla. If you have a HV zilla then my answer will be different.

#1) you currently have a 32.4 kWh pack (but this rated at 20 hour discharge) at EV current levels you are probably getting about 50-60% of this capacity so you actualy have a 16.2kWh pack, assuming same DOD levels for the new pack and old pack you will need 144v 112ah pack, but you car will be lighter so you can proably use a 100ah pack and get similar range. If you increase your pack voltage to ~152 volts (max for LV zilla) at 100ahr you should definitly get similar range.
no the not so good part a 100 ahr pack max discharge is 4C, so 400amps. This isn't exactly using your Zilla much.

#2) if you want you use your zilla to its full capability you will need 1000amps/4C , 250 ah rated pack (they have a 200 and a 260). at your system voltage of 144V this will be a monster pack of 37.4 kWh, big range, big money.

my advice, buy the biggest battery you can possibly afford, I wouldn't recommend using a battery smaller then 160 ah with the Zilla. the CALB 180 Ah batteries may be a good choice and the 200 ah Thunderskys would be great if you can afford them. If you go for the 200 ah TS cells make sure you are getting new stock with smaller form factor (same size as teh CALB 180 and TS 160 cells) they will be easier to integrate. The old 200 ah batteries would quite large. Consider upping your system voltage to 152 V (48 cells) instead of 144V (45cells) but check your other components, but your Zilla can handle it. Also you'll need a new charger, or to reprogram your old one. Also there is the big BMS or no BMS question.

hope this helps.

#### F16bmathis

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My current "dead weight" is Lead acid Trojans. When the batteries were new, I could get 1000 amps on the motor side, unsure of battery side. I did limit the Zilla to 400 amps, but Zilla really doesn't explain what those functions do, just how to change them. I played some, set it where I didn't think I was blowing anything up and left it that way. It been a while, so I forget what settings there were. That was 7000 miles ago.

Looks like at least 160 AH Thundersky's and maybe even up the voltage some. At 1C I can discharge it at 160 amps for an hour, for my 30 minute drive I could pull 2C at 320 amps, since I drive more around 0-200 amps, I can also hit 3C at 480 amps occasionally?

Less weight, more discharge, equals a smaller pack, but for a few extra bucks I could get the 200 ah's and not worry I bought too small of a pack. Throw in an extra 3 batteries and...

#### F16bmathis

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Doesn't voltage equal top speed, and amps equals acceleration? My 144 pack had 80 mph top speed, and the 400 amps (limited in Zilla) had great acceleration.

#### F16bmathis

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I guess I'll go with 48- 200ah Thundersky's. I only need to travel just less than 20 miles, then charge for up to 8 hours, then drive home. Occasionally driving a little around town, but I would like more. More is better, especially if I can drive to EV shows with it.
I'm still looking into BMS systems, don't want to fry these new batts.
My charger is a Manzanita, so I can adjust as needed.

#### Duncan

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Hi Guys

I think there is a misunderstanding here

The Zilla operates on a Voltage in x Current in = Voltage out x Current out

If your motor is using 50v (at that time) and your battery is 150v then if you have
100Ah batteries at 3C = 300A battery = 900A motor

The voltage that the motor needs will be dependent on its speed
I believe most DC series motors that we use normally operate at a good bit lower voltage than the pack voltage

I was originally going for 200Ah cells, but I am now going for 100Ah as they are
Cheaper!
Lighter!
I will lose range - definitely
I may lose acceleration - not sure,
If I can break traction with the smaller cells then the larger cells would actually make me slower -
I look forwards to finding out!

#### dimitri

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I believe most DC series motors that we use normally operate at a good bit lower voltage than the pack voltage
This is false and it makes your entire argument false.

Yes, power in = power out, but you can't just assume that motor voltage will not rise to the pack voltage, it does it all the time as RPMs go up.

The best way to calculate max battery current is to start with motor power. If Warp9 can take 100kW ( its just a round number to show my point, I don't know how much Warp9 can take off top of my head ) and you have 150V pack for example, then your max battery current could be up to 667Amps.

To back it up with real life data, my EV has 128V pack. Until I set battery current limit in my controller I could easily pull 550Amps from the pack. I even slightly damaged some of my 160AH cells by doing it. Since then I set the battery limit to 450Amps.

#### EVfun

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Hi Guys

I think there is a misunderstanding here

The Zilla operates on a Voltage in x Current in = Voltage out x Current out

If your motor is using 50v (at that time) and your battery is 150v then if you have
100Ah batteries at 3C = 300A battery = 900A motor

The voltage that the motor needs will be dependent on its speed
I believe most DC series motors that we use normally operate at a good bit lower voltage than the pack voltage
I agree with this. The only time the motor sees full pack voltage is when the throttle is floored and the motor rpm is higher than [where is comes out of] current limit.

I was originally going for 200Ah cells, but I am now going for 100Ah as they are
Cheaper!
Lighter!
I will lose range - definitely
I may lose acceleration - not sure,
If I can break traction with the smaller cells then the larger cells would actually make me slower -
I look forwards to finding out!
I disagree. I can show you how to break traction with 25 kW of power (low gears) but you won't be able to sustain that acceleration. 100 kW would most certainly be faster, even if you had to limit the initial acceleration to prevent wheel spin. (400 kW would be a riot!)

#### Duncan

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Hi EVfun

I disagree. I can show you how to break traction with 25 kW of power (low gears)

Aha - but I don't have a gearbox! - I am using direct drive!

But you are right anyway - more power means I can sustain the acceleration longer (higher motor rpm)

The only time this would not count would be if i could reach max speed and still be able to spin wheels (speed limited by something else - max motor rpm? - police?)

#### JRP3

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Not only will larger ah cells give you more range and more power but they will last longer since they will be delivering the same amps at lower C rates and generally being discharged less. If you want to pull higher C rates you might want to consider CALB cells. I've pulled 5.5C from my 100ah SE/CALB cells with no problems. I don't recommend doing it often of course but I've seen no change in capacity or power.

#### F16bmathis

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So I settled for 45 160 AH's, did shopping around, even got quotes, but now I'm not getting any reply's except from the most expensive company. \$1500 more than anyone else, but I can have them in a couple of days.

And BMS systems, the Mini BMS is cheapest, but might get corroded with dirt/water, and the other companies are not replying back (Thundersky, & that other guy with the touch screen BMS's)

I've got the money, sitting in the bank waiting...who wants it?

#### dimitri

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And BMS systems, the Mini BMS is cheapest, but might get corroded with dirt/water
No more corroded than any other BMS and no more corroded than your cell terminals, carrying large currents. So, if you are worried about corrosion, then BMS is not your main worry.

I try to stay away from BMS recommendations based on my bias, so my response is not a sales pitch, just defending my product from such remarks.

Good luck....

#### MN Driver

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Not to mention any of the other electronics added to a car besides a BMS. Most vehicle setups that I've seen have the batteries inside the car or enclosed in some way to prevent at least the terminal side of the battery from being exposed to dirt and water and in colder regions usually you want to keep them somewhat sheltered from the cold as batteries perform much better if they are getting down to freezing temperatures or lower.

#### F16bmathis

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I have now! OMG they are cheap! I can get 200AH for the same price I was going to buy 160AH's! Thanks for that site!

#### F16bmathis

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No more corroded than any other BMS and no more corroded than your cell terminals, carrying large currents. So, if you are worried about corrosion, then BMS is not your main worry.

I try to stay away from BMS recommendations based on my bias, so my response is not a sales pitch, just defending my product from such remarks.

Good luck....
Sorry, didn't mean to bad mouth the product. I just meant I don't currently have a top to my battery boxes (using lead acid). I may even go with them, and from further reading I guess I'll have to cover the Thundersky's, or figure out how to keep them dry and clean.

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