Automated Volt Limiting BMS - Does it Exist?

Joined
Aug 6, 2017
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16
Location
Collingwood, Ontario, Canada
I'm looking for a BMS that will limit the output volts to keep RPM and Current max the same. Meaning if I run a 84v system at full charge, the BMS will only deliver 60V consistent until there is only 60v left in the battery cells and after that volts drop and user knows the battery is is close to empty.

Anyone know of a BMS like this if so where, or is anyone interested in developing it with me?
 
You are right, and the best ones out there that allow all the limiting we need are by MGM Controllers :) thank you eee291
 
LogicalDIYBuilder said:
You are right, and the best ones out there that allow all the limiting we need are by MGM Controllers
And by ebikes.ca. And several others.
 
FWIW, if you develop a BMS to do this, you are basically just making a really big DC-DC converter that wastes some of the power in the process.

Since you have to do the conversion inside the controller anyway (even if you also use a DC-DC before it) while running the motor, there's no good reason to have a completely separate converter from the controller to do this. It'd probably be as big as your controller, too, or bigger, depending on the capacitor and transformer sizes you have to use to sustain the loads you're after.


If what you you really want is to maintain a specific speed, or have a maximum speed limit, it's very easy to do with a Cycle Analyst from Grin Tech at http://ebikes.ca. You don't even need the fancy v3.x, you can use the older v2.x types.
 
http://www.lowcarbon-idea.com/eshowshop.asp?/11.html
And if you want to feed charge back (regen) http://www.lowcarbon-idea.com/eshowshop.asp?/81.html

Probably way overkill for you, but you didn't specify. Just a hint at what you need to look for. DC-DC converters that are able to output your 60V.
 
You really don't want the BMS or whatever between the battery and the controller to be dropping the voltage. It is inefficient and would be quite expensive at a decent power level.

Much easier is to let the voltage vary and use the controller to keep the speed constant over a wide voltage range. No additional losses and likely to be much less expensive and heavy.
 
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