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Old 02-17-2013, 08:59 PM   #369
_cy_ OP
Beastly Adventurer
 
Joined: Sep 2011
Location: Tulsa, Oklahoma
Oddometer: 5,893
Quote:
Originally Posted by meijer's trails View Post
I wanted to have someone build me a battery replacement t for my 87honda xl600r. The original is 12v and quite small.

Its kick start only, but the battery does need to run a headlight, horn, turn signals and indicator and instruments lights.

There's very few other weight saving opportunities .

I thought of trying to build my own but I think there needs to be a balancing circuit.
What do you think?
A pre made up earth x or maybe some custom soldered cells? What is a balancer? Do I need that on an 87 xl600r?
if you've got access to a spot welder .. go for it... LiFePO4 cell suppliers often will also offer BMS mated to your configuration.

there's many different types of balancing circuits. simplest are shunts that connect to every cell. when voltage goes over a set point. current is shunted off, allowing rest of cells to come up to full charge.

4 cell LiFePO4 20 AH (actual 19AH @ 8amp discharge rate) using Thundersky prismatic cells... uses four balance circuits (one shown)


batteries that have balance ports have a separate wire to each cell. this allows charger to balance cells ... some by shunting off excess voltage, some by regulating current to needed cell, etc.

for a smaller LiFePO4, my recommendation is to go with Earth-X. which has an internal BMS and has outperformed Shorai on smaller sizes during 200amp crank tests. both Shorai LFX 36 and Earth-X ETX 36 give outstanding cranking amps and perform at about the same levels.

Shorai doesn't say much about internal BMS, but Shorai LFX 36 bleeds down to about 13.85 after a full 14.6v charge. indicating an internal BMS is in action. further when a balancer charger is used on LFX 36, cells are very close in voltage.

LiFePO4 batteries without BMS will bleed down to about 14.1v-14.2v after sitting overnight. then when a balancing charger is used, differences in cell voltages shows up on Powerlab 8 during charge.

here's a snapshot of four cell LiFePO4 battery finishing up a balance charge .. when all four cells reaches 3.65v .. charge is finished.

_cy_ screwed with this post 02-19-2013 at 05:13 AM
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