Battery Pack Break-in?

I'm wondering how many folks follow a break-in procedure with a new battery pack (lithium ion). I came across an article on an e-bike blog that described a break-in procedure, similar how you needed to break-in a new motor in the old days (don't discharge at high rates or tax the battery in any way until the break-in is completed), mainly to ensure the pack is completely balanced before stressing it.
It makes sense, to get a new battery in a state where no individual or set of cells are not optimized at the get go, and since I never did it, I was thinking about going through and balancing it over a couple of days since the pack is still pretty young.

Yes, the cells should not be pushed too hard on the first few cycles. It's also important to make sure the cells are balanced if the pack has been sitting around for a long time. I don't know how important the break in really is, but you will notice better performance after a few cycles.

I have read that "some" companies make lithium batteries with a dash of some type of preservative chemical to help their shelf life. And that it takes two or three light cycles to deactivate it, in order to get the full range and the full C-rate.

However, I don't have any specific details, so...who knows?

Sounds like it wouldn’t do any harm at this point. The procedure went something like charge to full, remove the charger, let the battery rest/balance over night, bleed/ride off a little charge, let it cool, charge to full, repeat. Said it could take a few cycles, but it didn’t describe too well how to tell when balancing is complete. Weather looks like it will suck until the weekend, so I may try it.


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That sounds like a balancing procedure. I don't think it will hurt. If you have a way to measure individual cell voltages, you could see if it even needs balancing or not.

You can also put a little load on it with an old light bulb or if strong enough battery a hair dryer. Then recharge. So what battery you got. To run what and what amp controller ?

fechter said:

That sounds like a balancing procedure. I don't think it will hurt. If you have a way to measure individual cell voltages, you could see if it even needs balancing or not.

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Would another way to telling how far out of balance the pack is, is by measuring the voltage in the morning after the BMS has done its thing to see what the voltage drop is? In other words, reading about how the BMS transfers some of the charge from the group(s) that achieved a full charge to the groups that didn't, I would think the overall pack voltage would drop more by morning if it started way out of balance, and less of a drop after each subsequent balancing cycle?

Most packs just need a better balance, if a bms was running while it stored or shipped. A few short rides, then recharges, usually tops it up a few times and gets it in balance.

I don't think in matters too much if you ride farther, like half its capacity or so, but it definitely gets through the three or four charges faster if you only ride around the block each time.

Every pack will lose some charge sitting there overnight, or in a half hour if a bms is discharging a high cell. If you see more discharge than you have found normal for the pack, then its unbalanced. Or really old.

Just use lighty for 4or5 times . No race to cutoff or lvc. Don't find the steepest hill to blow it up.

E-HP said:

Would another way to telling how far out of balance the pack is, is by measuring the voltage in the morning after the BMS has done its thing to see what the voltage drop is? In other words, reading about how the BMS transfers some of the charge from the group(s) that achieved a full charge to the groups that didn't, I would think the overall pack voltage would drop more by morning if it started way out of balance, and less of a drop after each subsequent balancing cycle?

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It's hard to tell from the resting voltage. Even if there was no BMS, the cell voltage would drop slightly after coming off the charger. In theory what you are saying should work but the voltage drop would be very small and may be affected by temperature. It might be worth checking since it's easy to do. If you see a relatively large or fast drop in voltage, it might indicate a problem.

fechter said:

E-HP said:

Would another way to telling how far out of balance the pack is, is by measuring the voltage in the morning after the BMS has done its thing to see what the voltage drop is? In other words, reading about how the BMS transfers some of the charge from the group(s) that achieved a full charge to the groups that didn't, I would think the overall pack voltage would drop more by morning if it started way out of balance, and less of a drop after each subsequent balancing cycle?

Click to expand...

It's hard to tell from the resting voltage. Even if there was no BMS, the cell voltage would drop slightly after coming off the charger. In theory what you are saying should work but the voltage drop would be very small and may be affected by temperature. It might be worth checking since it's easy to do. If you see a relatively large or fast drop in voltage, it might indicate a problem.

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Makes sense. The last couple of charges I've noticed that very early in my ride the voltage seems to drop almost 2 volts right away and then discharges at a normal rate after that, so I'm wondering if it may be related to the pack being out of balance. I'll try dong the routine this weekend and take some measurements.

Thanks to everyone; I'm probably learning stuff I should have studied up on in the beginning.

Re resting voltage, you will find that in the am you see a typical next morning voltage. When you see its way less than that, you will know you need to balance it. As your pack ages, its next morning charge will diminish, as the cells become unable to hold the full 4.2v. Cheap packs will show this age effect when new, due to a few substandard cells in there.


What you get is what you get. But you can tell when it just got suddenly worse, and try to fix it with some extra balancing.

Force it to balance with bms packs by doing the charge, wait half an hour, charge again, and repeat. Ride around the block to get the charger to restart, if it won't.

Dropping 2v right away when you start is not unusual. That last .1v in each cell does not hold all that much energy in any case, so you see it fade in a block typically. When that drop becomes 4v instantly, or even just overnight before you start, its the cells getting older, and unable to hold that last .2v of charge, with any actual energy in the cell.


When you see 2v drop is normal, and then suddenly one ride its 6v, that's a problem to try to fix by balancing. Hopefully, its just that your charge was not full, and balanced 100% full. You took off with 90% full, because of poor balancing. Or a loose charger plug. :lol:

dogman dan said:

Force it to balance with bms packs by doing the charge, wait half an hour, charge again, and repeat. Ride around the block to get the charger to restart, if it won't.

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Well I tried the method of charging, then resting overnight to balance, then repeating a couple times. It improved a little both times, but last night I did the forced balancing routine. I could get the charger to cycle after resting, by just flipping the breaker I used to connect the battery. After 4 or 5 cycles the voltage would barely drop and the charger would cycle off in less than a minute. This morning the battery was right where it was last night, so it seems like the balancing was successful.

One thing I noticed is that when pulling a lot of watts while bleeding off some of the charge before starting the forced balancing, even when fully charged, I'm getting significant sag, something like 4 to 5 volts at 1800 watts. I didn't notice it before, so maybe I wasn't paying enough attention. 1800 watts is above what the battery and BMS rating (30 amps), although I've pulled 2000+watts for a fair distance without having the BMS shut it down. I'm sure it's not good for the cheap Chinese cells though.

Anyway, I'm going to try a few experiments on the relationship between current draw to voltage sag since I found a nice little loop in my neighborhood that has no traffic at night and a decent short steady climb so I can hold the current steady while observing the drop, then regen down to the bottom of the loop. I have three other routes for testing regen, sag over a longer distance, and the last to test motor temperature before and after adding Statorade. I'll start another thread, but will only be editing the post, since the data is only to help me geek out and understand the various relationships (and anyone else that may be interested), but don't want the thread bumping to the top.

Here's the little loop that I'll be using for the first set of tests. I noticed last night that I could set my PAS to a certain base level, then use the throttle and pedaling to keep the watts steady. The climbing section is only 13%, but that's enough to use the battery's full range, while controlling my pedaling and throttle. I'll probably mount my phone to record the data on the display and graph the results.



EDIT: I did a pre-test last night and rode around the loop twice to see what I should expect. I forgot that to get to the loop is also a decent climb up a couple of blocks at 10%, so I let the battery rest for 5 minutes before riding the loop. So climbing up, then regening down, and letting the battery rest 5 minutes, I lost 0.2 volts per loop (58>57.8>57.6). I love the regen. Pretty consistent sag at 1800 watts, at a little more than 4 volts.

Depending on the size of your pack, 4-5v of sag at 30A is pretty typical. As long as the cells aren't getting hot, it should be OK.

Yeah, you definitely are expected to see that much sag, if you are hammering it. If it stays cool, you can keep that up. Stop if your pack gets a lot hotter than the hottest summer day.

But if you see 8v of sag or more, no matter what, that's killing your pack imo.


Nice that it responded to balancing. But it will over time, drop overnight to lower voltage than when new. A couple volts less, like 54.6v to 52.6v overnight is still usable. more, when balanced, its time for new batteries. You should go a few years before you even see 2v gone overnight, if its treated nice.

dogman dan said:

Yeah, you definitely are expected to see that much sag, if you are hammering it. If it stays cool, you can keep that up. Stop if your pack gets a lot hotter than the hottest summer day.

But if you see 8v of sag or more, no matter what, that's killing your pack imo.


Nice that it responded to balancing. But it will over time, drop overnight to lower voltage than when new. A couple volts less, like 54.6v to 52.6v overnight is still usable. more, when balanced, its time for new batteries. You should go a few years before you even see 2v gone overnight, if its treated nice.

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Thanks!! These are great guidelines for me to keep in mind. I was wondering whether I was damaging it, but I haven't had any of the bad signs. I've never felt my battery, motor, or controller get hot yet, but maybe my hand isn't a good judge. I'm going to start carrying my IR thermometer until I get a better feel for it.

Interesting indeed.
I have a professional battery diagnosis machine in my workshop.
I could try to run a few monitored discharge-recharge cycles on 2 new 36V 10,4Ah batteries of the same model, from the same batch.
One with slow discharge, like 0.3C, and one with fast discharge, like 1C, and see if there is a significant difference in performance after that.
The result won't be a scientific proof because not enough quantity but if there is a big difference it will surely give a hint...

1c shouldn't heat them much, so even lower will have an effect, but not a ton. It should be measurable though, any warmth is capacity that went to heat. In the world out there riding, almost nobody does a cold discharge. I have tried to get to that point to maximize range while touring. Discharging at about .25c, the air was warmer than the battery gets. With enough paralleled, I could wring almost double the capacity out of very old, very worn out lipos. At 1c they'd only get barely warm, but it would be able to put out about 40% of rated capacity. But at .25c, 70% at least.

Once you make a battery hot discharging it at 3 or 4c, then it lost a ton of energy into that heat, as well as doing at least some damage inside. At least, more wear than a 1c cycle for sure. Whatever the c rate is, if you are seeing more than 6 v of sag, its getting pretty warm discharging. 8v it will get hot. 2v sag is great, but I only ever saw that from lipos. 18650's I had would sag 5v for sure, in 20 ah size and 1.5c. Better cells can do better, I had generic shit cells.

The 36V 10,4Ah packs in my shop have 10s Samsung 26e cells, 1C is the maximum I let my systems pull from it, to assure a long life for my clients.
At constant discharge of 1C they get quite warm already.
If I remember correctly, the BMS is 20A max on these, but I will not push new batteries to their limits and sell them as new after that