# Can any controller limit battery amps by time?



## Guest (Mar 5, 2010)

No, many controllers are dumb controllers in that they can't be programmed. More smart controllers are being offered and it depends upon the what features the company put into the controller. Can some limit that? I am sure there are a few, Zilla to name one. Others, I do not know which. I know my Synkromotive controller has many parameters to control and limit. As for a timed limit I am not sure. Usually a max limit. Most of the time you would not be at max anyway. It is usually for only a few seconds. Even at the drags it is like 12 seconds (or less) at max. 

Pete


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## Tesseract (Sep 27, 2008)

maxvtol said:


> ...
> So can any controller limit the battery current draw by time, ie 20seconds at 3C and 2C thereafter (and let the battery rest at 2C or less for some period)? I haven't seen this capability on any spec sheet. ...


No, and from a practical standpoint this doesn't seem desirable because it would cause a sudden and very noticeable drop in acceleration. Besides, the current draw from the battery pack is very erratic - just take a look at any of the dyno charts Qer has posted!

The best way we have come up with so far in the Soliton1 is to let you set limits on maximum battery current (e.g. - 3C) and minimum battery voltage (e.g. - 2.9V per LFP cell) and, optionally, set one of the programmable inputs to regulate max motor current when a single cell reports it has hit LVC (via a BMS alarm signal). Anything more complicated strikes us as, well, more complicated... and with vastly diminishing returns. At some point the intelligence needs to shift out of the controller and into the charger/battery management system - you can't expect the motor controller to cover all possible battery types and driving situations.


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