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| Panasonic NKY467B2 36V 15AH 540Wh. Ebike Li ion upgrade, burning my father'ass? |
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| Zucca:
I want to upgrade my father's chinesium ebike from stupid AGM to Li ion battery. It's a crappy bike but it was a present... After the chinesium charger melted the 3x12V (already replaced once) batteries, I throw those stupid heavy (my mother don't even want to touch the bike because it's too heavy) AGMs with the charger out of the window. So I got an used ebike li ion battery from evilbay for a very reasonable price, plus I got my self another used ebike lion charger again stupid cheap. Cheap IS a must, I am not gonna to spend money on a sick horse. :horse: The battery I got it's a Panasonic NKY467B2 36V 15AH 540Wh, and the charger it's 42V 2A. In the description the charger gauge reported 4/5 state of charge, so far so good. Today it arrived and I started to play with it. Battery voltage was 22V, freaking 22V but the gauge always shows 4 of 5 led on... so I can't trust those leds. Oh well... I started the rescue mission. First I open the battery... very well done. It's a 900€ (new!) battery, so I was expecting something good inside. The package is a potting fest inside a nice plastic bag with am air vent (goretex?). there are two main connectors: one for the bike/big charger and one for a small charger unit. Here some pics smaller charger connector I took the battery from 22V to about 30V with 100mA charging current. Then I moved with about 1C to 36V... now it has just reached 36V. Of course I check the single cells voltage and they are always pretty close the others. yes. Who knows if the battery is still good... meh. It's a 10S3P configuration BTW, I am almost sure. Now I have to understand how that BMS works and rev-eng it... Do you guys knows what these letters means on the bike/big charger connector? + and -, I know it C: the charger port D: ? (Drive?) S: ? Let's see if my father's ass will burn on that upgraded bike. Safety first... :-DD Any help is appreciate. More to come. |
| John Heath:
Nice test bench. BMS stands for battery management system. BMS is your friend as it will shut the entire battery pack down if any of the lithium batteries ventures below 3 volts discharging and stop charging at 4 volts. This is good as discharging a lithium below 3 volts is throwing the dice. You can get away with it a few times but once too often and the lithium is toast. I would leave the BMS alone. The bike will run fine on 38 volts so why change it , a bird in the hand... On another note if the battery pack was stupid cheap then chances are there is a bad lithium which will limit the bike range when the BMS shuts it down. With BMS you are only as good as the weakest lithium battery. The way to tell is cycle the battery pack through a charge and discharge. Towards the end of the discharge measure the individual lithium batteries. If most say 3.5 volts but 1 says 3.1 then you found the bad guy. With a little luck they will all say the same voltage + - 200 m volts so you are good to go. :-+ I was going to leave at this but I have to know. What is the square box in the lower right corner of the test bench with the round circle on it?? A compass ? |
| Zucca:
--- Quote from: John Heath on October 09, 2018, 02:16:50 am ---I was going to leave at this but I have to know. What is the square box in the lower right corner of the test bench with the round circle on it?? A compass ? --- End quote --- Do you mean the Nespesso coffee box? Thanks John to stay with me in this madness. I charged 1C up the battery to 40V and the 10 cells were all at about 4.00V so cool :clap:. No temperature rising whatsoever, it looks good. I don't like that BMS for two reasons: 1) The state of charge was showing 4/5 full with a 22V battery voltage. It can't be right. 2) I think there are MOSFET https://www.st.com/resource/en/datasheet/stp260n6f6.pdf to enable the + and the charging port... and I think that's why I didn't have 40V on the external bike connector between + and -. This means I need to rev eng also before to attach the battery charger. Best case the BMS is stuck in error and power cycle with a charged battery will do. Now I am logging the self discharge voltage of the battery with that BMS attached... will see. |
| Zucca:
Ok, instead of rev eng I will remove completely that BMS and go with these cheap cheap chinesium toys BMS, I hope 20A cont./30A peak are enough: eBay auction: #263901952562 Battery Gauge: eBay auction: #162766012576 and done deal. PS: Don't you love the technical description of those cheap toys? I think I will connect the BMS like this: cristal clear, thank God there are just + and - in a battery... How many time they put a - instead of a +? :horse: |O EDIT: This makes more sense: |
| nctnico:
Keep the original BMS! It will be way better than a replacement. The state of charge usually is determined by current going in & out and it will be tuned for the particular cells used. If you do one discharge / charge cycle the state of charge will show the right value. Unlike other chemistries you can not use the voltage for the state of charge in Li-ion batteries. The original BMS probably shows a wrong value because the cells self-discharged. |
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