nanoT wrote:TIAN NENG 6DZM20 Lead-Acid batteres 12V20Ah (6 pieces) connected to give 72V20Ah
Controller SINE MOTOR for PMSM. Rated 72V, max current 35 A. Protection 63V
I travel 30-40 km/h with median range of 25 km. I am quite happy with the speed but would like to increase the range to 40-50 km and make the battery pack removable - to charge in the office.
My idea is to upgrade the battery to a Lithium pack of 60V 30 Ah with Andersson contacts. Would it be sufficent? The motor is getting 72V now, not sure if the 60V will do.
If you're happy with the speed now, keep in mind it won't be as high after you're done. Speed will be slower by the same ratio as the battery voltage is lower.
The slower speed by itself will give you more range, because it takes less power to go slower. (assuming you're going faster now than it will be capable of after the change).
You'd have to change the controller (don't know which kelly is good) because your battery pack's nominal voltage will be lower than the LVC (protection voltage) of the existing controller, meaning you'd only get to use a very small portion of the new pack before the controller shut down.
As to whether any particular pack will work, you first have to test on your actual ride how much current your system draws from the pack now. Then make sure the continous rating of the new pack is at least as good as that (better, if possible, for longevity).
If the new controller you're getting will make the system draw more current, then your pack also has to handle the new higher load, too. Until you change the controller and test the actual current draw, you won't know what that load is, though you can make some basic guess from the controller specifications. (I've had various controllers that are rated at a particular current, but either can't deliver anything near that current, or they supply much more than that rating even though they aren't supposed to).
To know if you will get the range you want, you need to know how many Wh (not just Ah) your system is actually using on the trips you take. You'll need a wattmeter to measure that.
You can divide that by how many miles (or km) the trips are, to find out the efficiency of the system. Then use that Wh/mile (Wh/km) to multiple times the new range you want, to find out the minimum Wh you have to have for that.
Then when you know the Wh, you can get a battery pack that is rated for at least as many Wh as you want for the new range.
The Cycle Analyst v2 (or v3 but you don't need it) http://ebikes.ca
does all the readings above, including the wh/mile (wh/km) if you attach a speed sensor.
There's dozens of hobby RC wattmeters that do the other stuff, but they don't track the last one. (no speed sensor).