# voltage limits at top of charge?



## dimitri (May 16, 2008)

Dan,

theoretically, all these controllers were designed for LA batteries, so you can assume that 120V nominal means 10 12V LA batteries, or 20 6V LA batteries. Since 12V LA batteries can go up to 14.5V when fully charged, you would think that 120V controller was designed to handle brief periods of 145V, which means it should handle 38 LFP cells charged to 3.8V.

Of course all this is theoretical and should be confirmed by controller maker or reseller for warranty reasons.

When I had 144V LA Miata with 12 x 12V LA batteries and Curtis 1231 controller, it worked fine at 160V I had immediately after full charge.

Hope this helps.


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## EVComponents (Apr 20, 2009)

When you see quoted numbers for Zilla, it is nominal voltage.

The base model Zilla Z1K-LV is 72-156 volts nominal. 
It is tested up to 240 volts before it leaves the factory.
It could handle 300+ volts in reality.

It is built with components to safely do much more. Basically it is overengineered so that you cannot hurt it.

If you size your battery pack for 156 volts nominal based on 3.2 volts per cell, you will be perfectly fine with a Zilla Z1K-LV. It can handle the brief period of time that your ThunderSky cells will be at max voltage.


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## dtbaker (Jan 5, 2008)

thanks for confirming what my 'guess' is that controller's voltage limits are most likely to be the nominal voltage, and most likely to take into account peak voltage of a pack coming off a charger.

what this is leading me toward is that the 'wimpy' Curtis 1221c rated at 120v might be safer for me to use than a zilla 1k as far as my batteries go BECAUSE of the lower amp output I basically would not be ABLE to pull more than 5C from a 100ah pack, not more than 3C for 5 minutes, and probably not over 200a for any length of time... which is really all I need to get around in a moderate hilly suburban use. Also nice that the 1221 is half the price of a zilla.


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## TheSGC (Nov 15, 2007)

I think if you stay with the nominal cell voltage of 3.2 volts/cell you should be fine. My old 96 volt Kelly had software limits of up to 120 volts, and 30x3.2=96 volts or 30x3.8= 114 volts. My lead acid charges around 114-118 depending on weather, and if any controller was going to let out the smoke, it would be that one. I had the limit set to 116 volts just so no one would drive off with the power cord still attached.

I now have a Zilla 1K-LV at 96 volts and I ain't going back to anything smaller! I do have my battery AMPs limited to 250 , or 2C just to squeeze as much life as possible from them.


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## dimitri (May 16, 2008)

TheSGC said:


> I think if you stay with the nominal cell voltage of 3.2 volts/cell you should be fine.


You can't stay with 3.2V if you want to have fully or even almost fully charged pack. You have to charge TS cells to at least 3.6V to get most of their capacity, even better to 3.8V. There is very little between 3.6V and 3.8V, but there is plenty between 3.4V and 3.6V when charging.

For example my NG3 has CC phase pushing 22 amps until 3.6V per cell, then CV up to 3.8V per cell. You don't want to cut it before 3.6V.


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## TheSGC (Nov 15, 2007)

dimitri said:


> You can't stay with 3.2V if you want to have fully or even almost fully charged pack. You have to charge TS cells to at least 3.6V to get most of their capacity, even better to 3.8V. There is very little between 3.6V and 3.8V, but there is plenty between 3.4V and 3.6V when charging.
> 
> For example my NG3 has CC phase pushing 22 amps until 3.6V per cell, then CV up to 3.8V per cell. You don't want to cut it before 3.6V.


What I meant was use 3.2 as the voltage for selecting cells for the nominal voltage of a controller, i.e. 120 volt 1221c would be 37.5 cells, so lets say 38 cells as a high end. 38 cells X 3.8 charging volts = 144.4 volts, or that same as 10 12 volt batteries charging a 14.4 volts.


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## ndplume (May 31, 2010)

TheSGC said:


> What I meant was use 3.2 as the voltage for selecting cells for the nominal voltage of a controller, i.e. 120 volt 1221c would be 37.5 cells, so lets say 38 cells as a high end. 38 cells X 3.8 charging volts = 144.4 volts, or that same as 10 12 volt batteries charging a 14.4 volts.


I have a "144V" LA pack on a Curtis 1231C, rated at max voltage of 144V. When I charge, the CV section tops out at 180V. I've never had an issue with my Curtis. AND I have turned on the controller while in the CV mode, that is how I used to check the CV voltage. (Now I have a gauge outside the ignition switch, so its not required).

But I'd still like to know what the max Voltage is. Why? I'm thinking of going to Lithium (finally). For each 12V LA, I'd like to replace it with 4 lithiums, so 12x4 = 48 x 3.2v = 153.6V. The CV on this would be 48*4.0v = 192V. Is that too high for the controller? 

Here is another question : Is there a place that specs for the various controllers are stored or where memebers could post them. Another controller I'm looking at is the Raptor DC600. I found the manual online, it lists the pack voltage as 156V with max volts at 192 volts. That seems to line up pretty well. - Thanks Mike


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## rwaudio (May 22, 2008)

ndplume said:


> I have a "144V" LA pack on a Curtis 1231C, rated at max voltage of 144V. When I charge, the CV section tops out at 180V. I've never had an issue with my Curtis. AND I have turned on the controller while in the CV mode, that is how I used to check the CV voltage. (Now I have a gauge outside the ignition switch, so its not required).
> 
> But I'd still like to know what the max Voltage is. Why? I'm thinking of going to Lithium (finally). For each 12V LA, I'd like to replace it with 4 lithiums, so 12x4 = 48 x 3.2v = 153.6V. The CV on this would be 48*4.0v = 192V. Is that too high for the controller?
> 
> Here is another question : Is there a place that specs for the various controllers are stored or where memebers could post them. Another controller I'm looking at is the Raptor DC600. I found the manual online, it lists the pack voltage as 156V with max volts at 192 volts. That seems to line up pretty well. - Thanks Mike


The controller will be just fine, but you do NOT want to charge lithium to 4v (LiFePO4) 3.45-3.65v seems to be the common charge voltage. 48*3.65 = 175.2v at the most. With the Raptor you might get away with a few more cells.


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## Ziggythewiz (May 16, 2010)

The 1221C has caps rated at 160V. For longevity you wouldn't want to be too close to that for long, but up to 148 for brief periods should be fine.

I've had mine up to a nominal 132V, which means just over 145 fully charged. If I had a 38 cell lithium pack I wouldn't hesitate to hook it to my curtis.

The 1231 rated at 144 likely has 200V caps, but I don't know that.


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## EVfun (Mar 14, 2010)

I wanted to point out that Manzanita Micro responded to another DIY member and recommended limiting the battery pack to 48 cells for the Zilla Z1k-LV controller. This was posted in another thread. 

I would think that a controller rated based on a nominal lead acid pack voltage should be good for a number of LiFePO4 cells equal to that rated voltage divided by 3.1. That would allow for the common choice of 38 cells for a 120 volt controller, but slightly higher number for a 144 and 156 volt pack (46 cells and 50 cell respectively.)


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