NiCd to Liion question

[Golyo]

We have an old Sparta Pharos in the family, it is a clone of the Yamaha XPC26 by the looks of it. It has a 24V brushed controller that is meant to work with NiCd batteries. From that I am assuming that it is similar with the other such controllers, and it cuts off the batteries at 20V+-0.5V. Because of this, if I use a 6S Liion pack the only problem is that about 25% of the batteries total capacity will not be used, because they will be cut off at about 3.3V. Somewhere I've seen that the NiCd packs had a built in 30A fuse, so if I use NCR18650PF Panasonic batteries in a 4P6S pack I should have almost 10 Ah and be on the safe side considering drain (the batteries are rated for constant 10A).
Is there something I am missing?
Obviously I will need to use a different charger. But other than that?

 

[wesnewell]

An LVC of 20V is good for a 6s pack. You wouldn't want it any lower. You will get over 98% of the batteries energy with that lvc.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=47294

 

[Golyo]

An LVC of 20V is good for a 6s pack. You wouldn't want it any lower. You will get over 98% of the batteries energy with that lvc.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=47294

I was asking about Liion, and was trying to mean LiNMC. In my language it Liion only refers to LiNMC - 3.7V nominal, 4.2V max batteries.

 

[999zip999]

Don't discharge below 3.5v as under load ( riding ) it will be a lot lower. It math so be safe. Get the cheap alarms and set lvc. 6s about 4usd.

 

[wesnewell]

There's a huge difference in 18650 batteries, so it depends on which you have and how many amps you're going to pull from them.
http://lygte-info.dk/review/batteries2012/Common18650comparator.php

 

[Golyo]

There's a huge difference in 18650 batteries, so it depends on which you have and how many amps you're going to pull from them.
http://lygte-info.dk/review/batteries2012/Common18650comparator.php

Thanks for reminding me about that! I'd better use LG HE2 for this then.

 

[dogman dan]

Might consider 7s, if using a chemistry that can go lower than 3.3v without harm. Won't be too high voltage at all, well under 30v.

3.5v a good number to use for Hobby RC, lithium cobalt packs. 7s ideal for 24v with them.

To avoid over discharge with 7s NMC or whatever, just add a low voltage alarm beeper. (with on off switch on the - wire in the wiring for when you park) Lots of them are at least 6s, and can be hooked up to at least 6 cells of the pack. That will do.

 

[Golyo]

Might consider 7s, if using a chemistry that can go lower than 3.3v without harm. Won't be too high voltage at all, well under 30v.

I definitely don't want to fry the controller. The whole problem is that it is so integrated with the motor, that I don't want to touch it at all. I fear that 29V might be too much. Am I too conservative?