Search found 137 matches

by docware
Oct 16 2019 7:37am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

I have peak load 0,9 C = 3A per cell on my ebike 8)
by docware
Oct 15 2019 2:52am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

The rate at which a battery or cell can be charged or discharged is limited by the rate at which the active chemicals in the cells can be transformed. Forcing high currents through the battery results in incomplete transformation of the active chemicals reducing the battery’s effective charge capac...
by docware
Oct 14 2019 1:45am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

Now#2, pulling about 120A from a 17.5Ah 25R pack is abusing it as I've seen 25R packs being totaled after 10 month of use (not even daily) at 110A 20Ah which is bursts of 5.5C. So I'm abusing my poor 7P 25R pack. Yes, we agree with you. And you already know it : you are abusing your pack by high cu...
by docware
Oct 13 2019 4:41am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

why do you stop recording after stopping the discharge? in my experience the temperaure continues to rise in high amp testing as the heat takes time to travel to the outside of the cell. Yes, you are right, there is always some thermal momentum adequate to amperage. I don´t stop temp recording with...
by docware
Oct 13 2019 3:42am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

Why would I need it to be so fast? I don't think a cell would ever flactuate in temp very fast... I have chosen such subtle, thin wires because I wanted to have very fast thermocouple. For cells warming measurement is my thermocouple probably unnecessarily fast, but on the other hand I am sure that...
by docware
Oct 13 2019 3:19am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

flippy wrote:
Oct 12 2019 9:39am

how did you kill the channel?
I killed EBC-A10H tester by incessant calibrating only high current during capacity measurements. Proper procedure is calibrate both, high and low current. Very probably that is also reason for issue with one channel of EBC-X0510. So it was my mistake.
by docware
Oct 11 2019 12:23pm
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

i use the same one. but callibrating is a b itch. i also got a single channel one that can do 50A for testing big cells or large parrallel cell blocks. I don´t like ZKETECH calibration, in fact I hate ZKETECH calibration :-) I killed my EBC-A10H tester by incessant calibration, I killed also one ch...
by docware
Oct 11 2019 11:14am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

Can you please check out the link I attached in the previous message and tell me if it's a device that enables to create charts? btw, what is the difference between the temp probe that comes in the link I posted to the super thin one you use? Thermometer MASTECH MS6514 has logging possibility and U...
by docware
Oct 11 2019 3:54am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

ZKETECH EBC-X0510 is 8 – channel equipment for long term cycling obtainable at Aliexpress. Allows full control of testing parameters : charge and discharge currents, charge cut-off, charge and discharge voltage, waiting time between cycles. Accuracy better than 0,3 %.
by docware
Oct 10 2019 2:10pm
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

Current is variable at all ebikes. Solution is estimation of the average current and perform the warming test at constant average current. You can get the cell holder BF-2A from Aliexpress. My version is 10 A max. Equipment : GW Instek GDM-8351, Maynuo M9712, ZKETECH EBC-X for charging, Omega HH520,...
by docware
Oct 09 2019 10:47am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

Thats very interesting! Is that from the datasheet? I would like to know the temps for about double these currents for about 1 minute constant It´s my measurement. 1 minute is too short time to see the temperature change on the surface of the cell. Can you describe intention of such measurement mor...
by docware
Oct 09 2019 4:39am
Forum: Battery Technology
Topic: Sweet spot for cycle life?
Replies: 9
Views: 298

Re: Sweet spot for cycle life?

Since at 30 % SOC is my ebike „lazy“, I tend to be around 40 %.
by docware
Oct 09 2019 1:15am
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

Well rg12, then 21700 format may be interesting for you. Samsung 50E for high energy application and Samsung 40T for high power application. See informative graphs for single cell warming in the BF-2A fixture. Here is cell cooled by ambient air and also by BF-2A itself. Of course, in the battery pac...
by docware
Oct 09 2019 12:24am
Forum: Battery Technology
Topic: Sweet spot for cycle life?
Replies: 9
Views: 298

Re: Sweet spot for cycle life?

According this study, for very shallow DOD like 20 % is better to cycle at low SOC ( 20 – 40 % SOC or 30 – 50 % SOC, generally bellow 50% SOC). https://www.mdpi.com/2076-3417/8/10/1825 But avoid cycling too close to low end SOC, as there is increased anode degradation at such low SOC cycling : „ For...
by docware
Oct 08 2019 2:26pm
Forum: Battery Technology
Topic: Samsung 40T and other cells like it?
Replies: 75
Views: 1665

Re: Samsung 40T and other cells like it?

Well, if we are on the topic... What is the highest capacity I can find in Li Ion cylindrical? (above 21700 of course) The problem with your „Monster bike“ is that your 25R 24s 7p battery is not properly designed to your 5 kW motor. For your expected 80 – 100 A you need much higher capacity, much b...
by docware
Oct 06 2019 10:16pm
Forum: Battery Technology
Topic: Any need to Balance?
Replies: 20
Views: 442

Re: Any need to Balance?

Doc, I see that at about 3.4V there is a noticeable fall off on discharge. Do you have a measure of capacity or total elapsed time for each graph? I'm hoping to see about 3000 mAh. But it's true....so far all my data is from the spec sheet. Bob Typical GA discharge curves : Sanyo GA 1A 2A 3A 4,2-2,...
by docware
Oct 06 2019 3:51pm
Forum: Battery Technology
Topic: Any need to Balance?
Replies: 20
Views: 442

Re: Any need to Balance?

John in CR wrote:
Oct 06 2019 2:49pm
In the future, prior to pack assembly put all cells in parallel for a day or 2 to get the cells in perfect balance to start.
Yes, very good remark. Levelling the cells should be No 1 step.
by docware
Oct 06 2019 12:32pm
Forum: Battery Technology
Topic: Any need to Balance?
Replies: 20
Views: 442

Re: Any need to Balance?

I have also Sanyo GA cells in my 10s5p pack. Your information are probably mainly from Panasonic/Sanyo datasheets. Assumptions for decent GA lifetime (up to 1000 cycles/80 % capacity) : charge 1A max, discharge continuous 2,5 - 3A max, peak short time discharge cca 4 - 5 A max, 50 – 60 % DOD max. Ch...
by docware
Oct 05 2019 11:40am
Forum: Battery Technology
Topic: Any need to Balance?
Replies: 20
Views: 442

Re: Any need to Balance?

If your 20s 4p battery pack is designed to 10A peak discharge, than Sanyo GA is probably wrong choice. I am saying probably because we don´t know average DOD and average discharge.
by docware
Oct 05 2019 1:39am
Forum: Battery Technology
Topic: Any need to Balance?
Replies: 20
Views: 442

Re: Any need to Balance?

If I understand properly, charging current is 3 A.

What is average and peak discharge currents ?

What is an average DOD ?
by docware
Sep 29 2019 7:01pm
Forum: Battery Technology
Topic: What charger to use for 12S Li-Ion.?
Replies: 15
Views: 401

Re: What charger to use for 12S Li-Ion.?

YZPOWER Auto-Stop 50,4 V battery charger can be what you are looking for. Just choose current, input and output plug. 5A could be optimal for 6p. Fan is silent.

https://www.aliexpress.com/item/3282983 ... 1cdeWvSXOk
by docware
Sep 29 2019 4:43am
Forum: Battery Technology
Topic: 14s8p triangle battery pack cell layout
Replies: 6
Views: 210

Re: 14s8p triangle battery pack cell layout

Yes I have battery on my mind, current limiting will be positive for the lifetime.

Temperatures are currently well bellow 15 °C in Norway, so more and more from optimal temperature range
20 – 30 °C.
by docware
Sep 29 2019 3:41am
Forum: Battery Technology
Topic: 14s8p triangle battery pack cell layout
Replies: 6
Views: 210

Re: 14s8p triangle battery pack cell layout

It is a disadvantage of direct drive motor that is working at very low effectivity at lower speed/high torque situation and is wasting energy. I highly recommend to limit peak current to 25 - 30 A max. Do you use regenerative braking ?
What about the heating pads ?
by docware
Sep 29 2019 1:41am
Forum: Battery Technology
Topic: 14s8p triangle battery pack cell layout
Replies: 6
Views: 210

Re: 14s8p triangle battery pack cell layout

Peak load 50 A – how do you measure current ? How often are such high peaks and how long last ?
In what situation are those peaks ? Can you give more info about your motor ?
by docware
Sep 25 2019 2:57am
Forum: Battery Technology
Topic: LG M50T Grade A high capacity 5000mAh 21700 cell's test
Replies: 10
Views: 676

Re: LG M50T Grade A high capacity 5000mAh 21700 cell's test

Here is another point of view at this cell. I measured LG M50T cell capacity and DCIR across the whole SOC. Cell´s production date January 2019. Charging 1,45 A to 4,2 V, 0,05 A cut-off, 60 min rest. Ambient temperature 25 ± 1 °C. Equipment : GW Instek GDM-8351, Maynuo M9712, ZKETECH EBC-X for charg...