[chbot] High voltage batteries and electrolytic capacitors

Stephen Irons stephen at irons.nz
Wed Sep 30 23:18:44 BST 2020

At a previous company, when I did hardware develoment, the policy was 
200% maximum design voltage. For example
Nominal 12 V, with 5% regulator -> maximum design voltage is 12 V x 
1.05 = 12.6 V. Minimum capacitor voltage rating: 25.2 V, so you would 
have to use a 35 V capacitor, not the 25 V one.
There was some flexibility. If space or cost were tight, we could 
probably negotiate the smaller one in this example, because it is all 
under our control. But for external inputs, where things are less 
controlled, we would go the other way.

No idea where you would find 800 V capacitors?

EV City (Waltham Street) have a Nissan Leaf cut in half (diagonally, so 
it is still has 4 wheels and is drivable) showing the internal 
components. I think they also have an open drive unit and control unit. 
You might be able to see what they use.

Stephen Irons

On Thu, Oct 1, 2020 at 09:16, Peter Harris <petes.username at gmail.com> 
> General question: What is the rule of thumb for selecting the voltage 
> of electrolytic capacitors?
> Specific question: I am working with a Nissan Leaf battery, the 
> absolute maximum pack voltage is 405V. Are 450V electrolytics likely 
> to explode used at 405V?
>   P

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