How do I know when my battery has reached 20% SOC?

LikeThompson

New Member
According to the Juiced chart for a 52V battery, 45.4V is 20%. My question is, should I aim to stop using the battery as soon as the display shows 45.4v under load or is it okay to continue riding until the "static" reading (the reading when stopped) shows 45.4v - which would mean operating below 45.4v while under load?
 

Browneye

Well-Known Member
Static reading.
Don't sweat it. When it runs out plug it back in. ;)
If it's nearing LVC (love voltage cutoff) it will shut itself off anyway. Not good to leave it like that - charge to 50-70% or thereabouts for storage. Top up to ride.

Some manufacturers say to charge all the way up to store - but seems this can shorten battery life/cycles/capacity. I dunno, my dustbuster is ALWAYS plugged in. LOL
 

LikeThompson

New Member
The low voltage cutoff is user-adjustable and I've changed it several times now. I don't remember what the factory setting was. I'm trying to decide what voltage I should set as the cutoff point and I want to adjust for a 1 volt difference in the display vs multi meter reading. I haven't ridden the bike all the way to the LVC yet. I will eventually, but usually I need to recharge before I get there. I'll probably just set the LVC for 44.4V (which should read as 45.4 on my multimeter) and keep riding. Thank you!
 

harryS

Well-Known Member
45.4 for a 14S pack is 3.25V/cell. I don't think you will be going that low after you see how weak your ebike runs, compared to a full charge. If you recharge at 50%, I think it's better for life.

Browneye, my dustbuster has a 3 min run time these days. That's nimH anyway.
 

LikeThompson

New Member
45.4 for a 14S pack is 3.25V/cell. I don't think you will be going that low after you see how weak your ebike runs, compared to a full charge. If you recharge at 50%, I think it's better for life.
That's an interesting point. Most of what I've read focuses on battery longevity and the standard recommendation is to keep the battery beetween 80%-20% SOC. It sounds like you add the consideration of available power to the equation and adjust the range to 100%-50%. I'm going to try running the battery down to 45.4 and see how weak it feels.
 

Browneye

Well-Known Member
45.4 for a 14S pack is 3.25V/cell. I don't think you will be going that low after you see how weak your ebike runs, compared to a full charge. If you recharge at 50%, I think it's better for life.

Browneye, my dustbuster has a 3 min run time these days. That's nimH anyway.
Mine is lithium and runs for about 15 minutes. LOL It's actually useful!
Nimh were notorious for degradation and memory. My, we've come a long ways. 👍

The ideal SOC of 20-80% can help for ultimate charge capacity and longevity. So a low voltage cut off should be set for 20% for sure.
Charging your bike up to 100% to ride it is what it was made for. Just sayin'.
 

harryS

Well-Known Member
What kind of service life can we expect charging to 100%?
Look at a cell like the Panasonic 18650 GA. The manufacturer's testing will cycle it from 100% to 0% , recharge, and then cycle it again. After 200 cycles, it will still have 75% of its original capacity. After 500 cycles, 60%, THat's pretty rough treatment, so the battery makers will say their packs will still have 70% capacity after 600 cycles because they know we aren't going down to 0%. The ebike shuts off at 20%. So you can probably expect 500 cycles charging to 100%.

My wife rode her bike 83 times last year. I rode 160 times. 1000 and 1800 miles respectively, I charge after every ride. So I could go 3 years on a battery before I get to 500 cycles. The battery isn't dead at 500 cycles, either. It's just not at strong as when it was new. I started ebiking in 2015 when we were told to charge to 100%. I'm still using those batteries. While they might be down to 66%, they still work well enough for our use, a 60-90 minute ride.

Someone who rides to work 5 days a week, on an $800 battery, they might want to charge to 80% for extended life.
 

Bruce Arnold

Well-Known Member
We get a lot of chatter about battery usage and battery life around here. Great way to start an argument. LOL.

It's a good idea not to go below 20%. There seems to be a general consensus that putting a load on a battery below this level will have a noticeable effect on its longevity. That and keeping it out in the cold are likely to be bad for it.

I have a 48 volt battery, so the 20% level is at 42 volts. I set the cut-off at 42, but rarely go below 44. Not because of battery life, so much as that's the level where there is very little boost left. I have gone down to 42 2-3 times (owned the bike 2 years), when I was out on a long ride and getting close to home.

So here we are, 2 years and 3000+ miles down the road, and the battery is still doing fine. So it's working for me.

I've noticed that newcomers tend to overthink battery stuff. Get a few hundred miles under your tires and you'll see what happens -- you'll find a groove that works for you and not think about it any more.
 

LikeThompson

New Member
I've noticed that newcomers tend to overthink battery stuff. Get a few hundred miles under your tires and you'll see what happens -- you'll find a groove that works for you and not think about it any more.
As with most things. A little experience takes the mystery out of things and helps make good decisions.

Thanks for your input, everyone!