Voltage Question for Shorai Owners

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jaydee75

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I have had a Shorai LFX18 in my Mk3 for over 2 years and it is functioning well. No problems, but one thing has always bothered me. I want to hear from others what their experience is. Specifically:
When I unboxed my battery the voltage was 13.34. I charged it up to 14.3v. I have a good charging system on my bike and after a ride, it will measure high 13's. A few hours later it will be back at 13.3x. I have tried charging it to the recommended 14.4v, but after a few hours it will be back at 13.3x. It seems that is where it wants to be.
It works great and never needs charging between rides, I just wonder if this 13.3v is typical or is my particular battery a little weak from the factory.

What is your resting voltage after a few days?

Jaydee
 
Mine is in the same voltage range. And since the same Shorai 18AH has been in my Alton Estart '73 since '12, it clearly has no problem with that voltage/state of charge. By FAR the best battery I have ever had in a motorcycle.
 
Yup, same for me. I'll shut down after a ride with the battery sitting at 14+ (I have a voltmeter on the handle bars), and the next time I turn the ignition on it'll be 13.3. The only exception was at the beginning of this season when I put the Shorai charger in "charge" mode after sitting on "storage" all winter. It was up to 14 v at that point.

The charger's storage mode maintains about 13.2V, so I guess that's where they want to be.
 
An LiFePO4 cell has a nominal voltage during discharge of 3.2 Volts, so the typical, e.g. Shorai, 12 Volt battery has a nominal discharge voltage of 12.8 Volts. But the cutoff charge voltage is 3.65 Volts, so they can be charged to an open circuit voltage of 14.6 Volts. Most of the manufacturers recommend no more than 3.6 Volts per cell (14.4 Volts for the 12 Volt battery) charging, to prevent damage, so that's what you typically see for a fully charged battery right after you take it off the charger. The initial discharge rate just from current through internal resistance is quite rapid, and the voltage rapidly drops to something closer to the nominal 3.2 Volts per cell, and stays near that until it is nearly discharged, then drops off rapidly. This is a typical charge/discharge curve for a cell

Voltage Question for Shorai Owners


As you can see, after removal from the charger, the voltage rapidly drops to around 3.4 Volts even with little load, and stabilizes around 3.3 Votls, slowly dropping under load to just under 3.2 Vots, after which it drops precipitously. At somewhere around 2.5 Volts you start to see damage to the cell. That would explain why you see it drop almost immediately from 14.3 Volts on your charger to ~ 13.3 Volts. It's just the normal operation of this type of battery.

Ken
 
Here's an anecdotal comment regarding a Lithium Iron battery. I have experienced just how much internal resistance they can have and still read over 13 volts no load.

I put a relay in my ignition circuit to isolate the kill switch. Relay pulls in when ignition turns on. Total battery current with the relay, TriSpark EI and warning light is less than an amp.

I was chasing a charging issue down one day, and had started the bike 2-3 times (e-start) without the alternator connected. The next attempt to start went like this: Battery showing 13.1 volts. Turn the key on and the relay pulls in and feeds the ignition. Battery drops to about 7 volts, below the relay's minimum holding voltage. Relay drops out. Battery returns to 13.1V, relay pulls in again. The cycle repeated with the relay clicking on/off repeatedly. Key off, battery still says 13 volts no load. Very odd. I put the Shorai charger on it and the lights said "severe under charge". Ya think?
 
That is one of the issues with these batteries. When they get to that point in the discharge curve, it's all over. Still, I now have them on three different bikes, and I'm pretty happy with them. On older bikes with no current drain when the key is off, they will hold their charge seemingly forever. Well, at least for a long time. With modern bikes that have some current drain for the electronics, even when the key is off, I still have to be careful to put them on the battery tender, or the Shorai charger, regularly. Some years back, with my first Shorai battery, I managed to kill it by discharging down past the damage point several times. In my defense, it was on a total loss race bike, so a little more difficult to keep charged. Since then I've had no issues with them, except for a new one that was dead right out of the box, and Shorai replaced it immediately.

Ken
 
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