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

[LikeThompson]

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]

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

 

[tomjasz]

They are calling 20% as 3.5V per cell. For best battery life do quit at the static reading at 20%. Do they publish the LVC?

 

[LikeThompson]

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]

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]

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]

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'.

 

[tomjasz]

Charging your bike up to 100% to ride it is what it was made for. Just sayin'.

I have done that and they are the batteries that gave me the least service life.

 

[Partyman1971]

I have done that and they are the batteries that gave me the least service life.

What kind of service life can we expect charging to 100%?

 

[Browneye]

I have done that and they are the batteries that gave me the least service life.

Ah well, I'll be charging mine all the way up when I'm going to ride it. Yes, 100%!

 

[harryS]

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]

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]

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!

 

[tomjasz]

Ah well, I'll be charging mine all the way up when I'm going to ride it. Yes, 100%!

For some, the cost of running at 100% just isn't sustainable. As always YMMV!!

 

[Guitartec]

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?

By the time the average ebike user gets to the maximum charging cycles, new battery tech will be here that will, after becoming mainstream, be higher capacity, lighter in weight, more durable electrically and be less expensive than the cell you're sporting now. Also, due to new tech, you'll probably be able to get a duplicate of your current battery much cheaper as it goes out of style.

 

[tomjasz]

By the time the average ebike user gets to the maximum charging cycles, new battery tech will be here

What new battery tech are you suggesting?

 

[Guitartec]

What new battery tech are you suggesting?

Not suggesting anything particular, but solid state seems most likely to come first. There's literally countless companies working on countless new chemistries from cobalt to sodium. There's huge money at stake here as these new chemistries will power the world.

 

[FlatSix911]

Not suggesting anything particular, but solid state seems most likely to come first.
There's literally countless companies working on countless new chemistries from cobalt to sodium. There's huge money at stake here as these new chemistries will power the world.

Here is a bit of history on energy density along with a forecast on Solid State Wh/kg.

 

[FlatSix911]

Here are some data on charge cycles if you are interested in maximum battery life.

 

[tomjasz]

Not suggesting anything particular, but solid state seems most likely to come first. There's literally countless companies working on countless new chemistries from cobalt to sodium. There's huge money at stake here as these new chemistries will power the world.

Waiting for a technology change seems a futile endeavor for me. I've been reading about new breakthroughs for 7years. NONE have trickled down to eBikes. I'm afraid I'll be taking my dirt nap long before you see any big improvements.