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624 Posts
Discussion Starter · #1 ·
My converted, 1980 Kawasaki 440 LTD, motorcycle is currently running
...a 8kW brushed motor (~48V)
...controlled by a Kelly KDZ72550 speed controller
...& powered by a 2kWh 12S module out of a Chevy Volt (with the top charge voltage on the charger set @ ~49.8V)

With this set up my top speed is ~35MPH
...& the range is ~25 miles.

I have been thinking about upgrading to a 14S pack (with the top charge set @ 58.1V)
...or even a 16S pack (with the top charge set @ 66.4V)

To do this, I thinking that I may be necessary to change some components. (contactor &/or voltage reduced)

So, my question is, what is the highest voltage that most 48V components are designed to handle?

I believe most DC components are designed (or at least used to be) based on to voltage ranges of Lead chemistry.
...& going by this reasoning, a 48V system should be able to handle, at least ~54V (13.3V x 4 = 53.2V)
...but, can they safely handle a fully charged 14S pack? (~58V)
...or a 16S pack? (~66.5V)

Thanks, Kevin

1,078 Posts
Only the motor is (more than likely) fine.

You need to be intimate with the controller components

and even if they are all "rated" higher, reliability and longevity suffer as you get closer to the stressful areas near absolute maximum voltage

so very likely needs an upgrade

BMS 99% sure needs swapping

And shoot for a higher Ah capacity since your energy efficiency per mile will decline a lot with your going faster

624 Posts
Discussion Starter · #3 ·
Hey John, thanks for the reply.

Yup, I agree, the motor should be able to handle more voltage...just fine.
...& my controller is rated for 72V, it should be fine too.

It's the contactor & voltage reducer, that I was mainly concerned about.

The voltage convertor is labeled 48V-12V
...& lists an input voltage range of 30V-60V, IMO it should be able to handle 14S (~58V)
...but, like you mentioned, longevity may be compromised.

The contactor I'm thinkin' is probably a NO
...a 48V coil likely cannot handle ~58V being applied to it.

I'm not using a BMS, on my Volt pack
...or more accurately, I'm the BMS

I've put almost 500 miles on her since the conversion
...& the batt pack is perfectly "in balance" every time

I check/monitor before every ride, during my ride, after my ride & even after charging too
...& (knock on wood) both of my balance meters "always" show the exact same readings.

Again, thanks for the input, Kevin
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