Battery life & replacement question

[linberl]

I have a rear hub motor on my recumbent trike. The first battery was 36v13ah. Lasted just 2 years. I ride 6 days a week, avg 15-18 miles always in level 1, with the KT LCD3 set for minimal assist and lowest current. Charge only to 80% probably more than half the time, no cutoff, so it's hit or miss. Now I am on the 2d battery, and it's been 2 years. It shut off on me yesterday when I was waiting for a left turn (not moving) at 36.9v. I was able to restart the battery a few minutes later when I got home. My installer is planning to bench test but I can tell it's the same as the first battery. Is this reasonably normal lifespan? Second question: while it will cost me more, probably an extra hundred bucks, would a 52v 16ah have substantially more longevity? Enough to make it cost effective? The installer gave me half off the replacement battery because he gives an 18 mo warranty and and this isn't so far out. But this is my sole transportation so I'd like something more reliable as it is a hassle getting the battery to him to test and getting the replacements. Finally, since i have the KT dialed down to provide absolutely minimal assist, will it still "feel" the same way when riding if I have a 52v or am I going to have more assist than I want in the lowest levels of PAS?
TIA.

 

[docw009]

My opinion is you stress the battery more going from 80% down to 30% than from 100% down to 50% I charge mine to 100% and recharge after every ride. You're not getting the expected life out of your battery now, Try it at 100% (or 95%). We're both only using about half the battery, but you're using the bottom half, where the effects of ageing are amplified.

One data point I have is my 48V7AH pack, twenty six Sanyo GA cells. It's puny, with only 300 watt-hours. I've been running it like that from 2022-2025, and it's seen over 500 of these half cycles. Performs fine. Powers a 20" folder with LCD3 and KT controller and a 27" Raleigh with a low power TSDZ2 mid drive,

For the other part of your post, a 52V will spin the motor 8% faster than a 48V, You can dial that down in the LCD3 using the C5 parameter is it is an issue,

 

[linberl]

So my 36v battery reads typically 37.5v after an average ride and I charge it right before riding to 40v. Full charge is 42.1v. So that's only around 70%, if I understand correctly. so I'm shallow charging and shallow depleting as I understand it. 30% would be 35.43v.

 

[E-HP]

So my 36v battery reads typically 37.5v after an average ride and I charge it right before riding to 40v. Full charge is 42.1v. So that's only around 70%, if I understand correctly. so I'm shallow charging and shallow depleting as I understand it. 30% would be 35.43v.

Your charging routine seems pretty good. What cells are in the packs? I’d spend some time reviewing the datasheets for different cells to find what would work best given your use. The cycle life varies widely. For example, a cell that may be good for other applications, but not good for most ebike applications would be cell like the Samsung 50S, that can only go through 250 charge cycles before the capacity drops to 60% of new. Other cells may go through a thousand cycles and lose less capacity.

Cycle life tests of High Energy density cylindrical cells

Please note: You can find my other tests on my Patreon channel www.patreon.com/Pajda704 These tests will not be available anywhere else for a certain period of time. By subscribing, you will also support my future work here on the ES DIY forum. "Standard Power Rate" test (1C continuous...

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[linberl]

I don't know a lot about batteries. It's a 36 volt 13AH Samsung Lithium NCM Battery Li[NiMnCo]O2 Cylindrical Cells Battery. Now i charged it fully today (42.3v) and did my normal 18.9 mile ride and ended up with 39.v after resting it at home a few minutes. It did NOT shut down. It ran all of last week without shutdown, but i never dropped below 38v. The shutoff while I was stopped happened at just under 37v, a day when I only charged to barely 40v. So, logically, I'm wondering if I can just charge it fully from now on instead of to 80% so I never get close to 37v - and get substantially more use out of it. Or will it shut down at higher volts going forward? My choice for a new battery is either the same but 15AH or a 52v 16AH for an extra $130. All same brand/type.

 

[E-HP]

I don't know a lot about batteries. It's a 36 volt 13AH Samsung Lithium NCM Battery Li[NiMnCo]O2 Cylindrical Cells Battery. Now i charged it fully today (42.3v) and did my normal 18.9 mile ride and ended up with 39.v after resting it at home a few minutes. It did NOT shut down. It ran all of last week without shutdown, but i never dropped below 38v. The shutoff while I was stopped happened at just under 37v, a day when I only charged to barely 40v. So, logically, I'm wondering if I can just charge it fully from now on instead of to 80% so I never get close to 37v - and get substantially more use out of it. Or will it shut down at higher volts going forward? My choice for a new battery is either the same but 15AH or a 52v 16AH for an extra $130. All same brand/type.

How often do you fully balance the pack? If the cell groups are out of balance, or getting old, you could have the BMS cutting off due to a weak series group sagging below 3V (for example), even though voltage of the total pack is higher than the LVC for a 36V pack. You might want to balance the pack a few times a year (you'll need to leave it on the charger, even when the charger stops, and let it cycle on and off for a while).
Note that 42.3V is higher than a fully charged 10S 36V pack should be charged to (42V), so you may want to adjust your charger output voltage.

 

[linberl]

My charger is a basic 2 amp with no settings. It used to charge to 42.1 but last night i left it on all night to do what you said - balance. I normally charge fully once or maybe twice a month. If it's the BMS cutting off, and not a worn out battery (which it doesn't seem to be based on today's use) - do you think I should keep using it and just charge it fully each time or should I replace it now? Atm, the installer will give me half off the new battery as a slightly out of warranty concession. Not sure if that will apply in 6 months, bu then I would have 6 more months usage.

 

[99t4]

do you think I should keep using it and just charge it fully each time or should I replace it now?

The cells don't like sitting at full charge (4.2V) for extended periods. If you can schedule your charging sessions to just reach 100% full charge (or better yet 95%) immediately before you start your ride any damage will be minimal. Many here have been doing this for years.

Hopefully that gets you enough range to complete your ride without overly degrading the battery.

Did you find out which model Samsung cells are in your battery?

 

[linberl]

no, i couldn't get the info on the exact type. all i know is this: 36 volt 13AH Samsung Lithium NCM Battery Li[NiMnCo]O2 Cylindrical Cells Battery. I actually DO charge just before riding, so that works out. Wondering if i should try chargling a long time to "rebalance"?

 

[E-HP]

no, i couldn't get the info on the exact type. all i know is this: 36 volt 13AH Samsung Lithium NCM Battery Li[NiMnCo]O2 Cylindrical Cells Battery. I actually DO charge just before riding, so that works out. Wondering if i should try chargling a long time to "rebalance"?

Dividing 13Ah by an integer, I’d guess a 4P pack. So 13/4 =2600mAh. Samsung cells with a 2600mAh capacity could likely be their 26J cell, good for 5.2A. So, if this is the correct cell, then the 4P pack would be good for 20.8A when new. The cells drop to 70% capacity after 300 charge cycles.

 

[linberl]

Dividing 13Ah by an integer, I’d guess a 4P pack. So 13/4 =2600mAh. Samsung cells with a 2600mAh capacity could likely be their 26J cell, good for 5.2A. So, if this is the correct cell, then the 4P pack would be good for 20.8A when new. The cells drop to 70% capacity after 300 charge cycles.

So how do i translate that to volts? I'm not very knowledgeable about electric stuff. Today I charged up to 42.0v immediately before I rode, so it dropped to 41.7 right away. I did my normal ride (but the one where i do part of the mileage with the assist on zero for 8 miles) so 10.9 miles with assist mostly level 1 but two overpasses at level 3. When I got home the display read 39.7 after a couple minutes. And no shutdown, not even on the overpasses. So that's basically 2 volts for 10 miles which is how it's been since it was new. So my experience riding is that it performs pretty much like new as long as the volts don't go down too far (37v was the shutdown last week). I guess I kind of expected as batteries age and loss capacity that my range per volt would decrease.

 

[E-HP]

So how do i translate that to volts? I'm not very knowledgeable about electric stuff. Today I charged up to 42.0v immediately before I rode, so it dropped to 41.7 right away. I did my normal ride (but the one where i do part of the mileage with the assist on zero for 8 miles) so 10.9 miles with assist mostly level 1 but two overpasses at level 3. When I got home the display read 39.7 after a couple minutes. And no shutdown, not even on the overpasses. So that's basically 2 volts for 10 miles which is how it's been since it was new. So my experience riding is that it performs pretty much like new as long as the volts don't go down too far (37v was the shutdown last week). I guess I kind of expected as batteries age and loss capacity that my range per volt would decrease.

Many/most KT controllers that support 36v also support 24v or 48v batteries. The label usually shows 24/36/48 for example. I’m trying to recall, but I believe the lcd3 does not have a parameter to set the battery nominal voltage (36v in your case). Instead, the controller auto guesses the pack voltage. It sounds like maybe the controller thinks there’s a 48v pack. Parameter C12 allows you to adjust the lvc relative to the default value of what the controller guesses, so you can drop it down 1.5v from the default and see if that helps, without resetting the nominal voltage. I think there’s a routine of disconnecting the pack, fully charging it while letting the controller discharge, then reconnecting the battery to get the controller to recognize the pack voltage. There are experts on those controller here that may chime in, but C12 may be a bandaid.

 

[linberl]

My c12 setting is "4" which is 30v for a 36v system. I believe it "can" be set lower, but i would want some more knowledgeable folks to chime in on that first.

 

[E-HP]

My c12 setting is "4" which is 30v for a 36v system. I believe it "can" be set lower, but i would want some more knowledgeable folks to chime in on that first.

If the controller “thinks” you have a 48v battery, then it’s defaulting lvc to 40v.
Setting C12 to 0 should hurt anything if the system is already cutting out at 37v, but it would get you insight into whether it’s an lvc issue with the controller, vs a battery issue.