Battery Degradation

[Tadas]

50 minutes ago, Boogieman said:

And i guess with the 84V charger i have to charge those 50-60hours as the cells have never been charged that high before?

The long time is only for balancing the cells. The heating problem on one side you describe could be because of unbalanced cell pack, or not, very hard to say.

[Boogieman]

Ok, i guess i should disconnect in following order to minimize risk of any current flowing in thin wires. (As both thin and thick wires connect the packs, i guess the thin ones are powering less challanging task and has NOTHING to do with balancing between the two packs?)

1&2. The two thin connectors (1) (2) from left battery (to totally separate the two batteries, and prevent any equalisation going through those leads preventing separate voltage readouts)

3. The big connector from left battery (3) (on top) 

4. The big connector from right battery (4)(just below)

5. No reason to disconnect mother board connector (5) that joins the two batteries with the mobo (and to reach it i would have to pull off battery adhesivethat sticks crazy and remove mobo)

6/7 No reason to disconnect the two small connectors (6/7) on right battery as there is no load on theese when powered off and shouldnt affect batt voltage?

FINAL: Measure on each of the big connectors (3) and (4) of course.

Correct?

 

Man this is some shitty harness routing, saw that one battery connector had rubbed against something. They should be frekkin fixated with a bracket. Crazy sloppy chinese guys

Edited August 8, 2019 by Boogieman

[Boogieman]

Battery packs messsured separately (the yellow contacts i am not holding). Both are exactly the same voltage  

Left 82.6 (+/-0.7 meassure error)

Right 82.6 (+/- 0.7 meassure error)

So both packs are charged as per charge voltage from charger (82.3-82.5), even slightly higher but thats likely measuring error due to components in charger vs batteries.

So if i get this right, i just need to get a 84V charger to top off and balance the packs at 84V every 10th charge.

To make sure batteries get more charge cycles, charge at 90% (82.3-82.5) with this original charger.

[Boogieman]

This is really silly and proof Gotway engineers do not design harness and connectors for electrical safety but for fast manufacturing (or i dont know, haste?)

A. Strand (1) takes the same amps as strand (2), but strand 2 is heavier gauge, seems like the forgot strand (1) that is allrrady after the parallel of the batteries....ooops

B. connector (3) is totally unnecessary (and thus i taped it shit to make sure it stays shut and wires protected from main board where it rattles) and just another point of possible failure. They could have used a cable directly from mobo to (R) connector. I really dont get the design here? Batt packs have their pwn connectors so why...lol

Edited August 8, 2019 by Boogieman

[Boogieman]

This one being probably the most Dangerous. Originally those loose silicone tubes just slide back and forth over the bare motor cable metal connectors by just pushing them (imagine sustained vibration making them move 1/1000mm per vibration). I just pushed 2 by hand (really low force) and voila bare metal open for shorts. 

 

As its silicone, tape does not adhere very good so cable ties to the rescue

Edited August 8, 2019 by Boogieman

[Boogieman]

Tesla charger, adjustment and eye opener.

There was ONE adjustable pot, marked VR1. All drenched in glue to keep it from floating.

Hence i read what it was supposed to do, removed glue and adjusted 1/2 turn left and right while measuring output voltage.

Now here is the funny thing.

I have meassured output voltage on idle during following circumstances

When the charger was not opened: 82.3-82.5

After opening charger, nothing else: 83V

Adjusting 0.5 turn ccw 84.2V

Adjusting 0.5 turn cw 84.1V

Now, regardless of how i turn the pot i can not get below 84V. Starting to think this is NOT output voltage reg, but rather cutoff amp pot.

Luckily i took a photo of the angle before touching it so it's now back to start state, but output voltage is still 84.2V.

While this would be good for balancing, i do not like when things change without reason.

Hence i tried charging at default setting and touched the components meanwhile to check hotspots and DAMN, one of the capacitors were squeeky hot in just minutes.

Looking at the inside of the lid, this + the choke has obviously been running hot gor quite a while. This is probably the biggest fire hazard on Gotway wheels. I understand that the aftermarket charger in a slightly smaller package melts (different thread on that subject)

Made in China when i was young used to mean crap, now they make all the shit in the world, but hopefully it's better manufacturing practice when they get the schemes from trusted us/eu developers than when they skimp on components like this to keep cost down. Who wouldnt gladly pay an extra 100$ for a safe charger and batt pack? That would cover the costs with huge MARGIN to make something robust.

Man, I love the feeling of the wheel, but i dont line to be worried every time its time to charge

Supet hot capacitor (starting to show signs of bulge, going poof)

 

Heat pattern on top cover of charger lid, pulled my finger through the "pattern" after photo and yes that is some smoke/plastic burn that scraped right off. 

[Planemo]

Don't know what the specs are like within our EUC chargers, but a whizzkid on an ebike forum I am on identified a problem with the capacitors on ebike chargers and the problem applied to lots of different suppliers as the internals of the charger were virtually the same (36v 2A). His charger packed up and identified it was the capacitors (x2) which were right on the edge of the demands asked of them and one had popped. He posted up the type to replace them with (cant remember if it was higher voltage/higher farad or both) which were quite a bit bigger in size. I and many others replaced them in our chargers and no one has had a problem since. We also cut round holes in the plastic casing to reduce heat further. Maybe we could do something similar with our EUC chargers to future-proof them?

[alcatraz]

On 8/4/2019 at 10:16 AM, Boogieman said:

Definitely seems like BMS is at the hot spot, or what are those sauare things if not components of some kind?

This is a good picture. I was thinking if it were possible to figure out where the individual group terminals on the tesla were and just cut the shrinkwrap over them. Cut a flap that can be lifted and then taped shut again. That would be a great way to monitor tesla packs without much hassle or risk.

[WI_Hedgehog]

On 2/6/2019 at 5:36 AM, Chriull said:

From my readings the only real solution to have long lasting packs is perfect cell matching when producing battery packs!

What provides the BMS to prevent premature cell degradation and keeps us safe (fire hazard):

- overvoltage protection on cell basis:

Afaik from different discussions/BMS fotos/datasheets normally used BMS provide passive balancing. From (2) "Passive balancing bleeds high-voltage cells on a resistor during charge in the 70–80 percent SoC curve; active balancing shuttles the extra charge from higher-voltage cells during discharge to those with a lower voltage."

But (2) "A battery expert once said: “I have not seen a cell balancing circuit that works.” For multi-cell packs, he suggested using quality Li-ion cells that have been factory-sorted on capacity and voltage. This works well for Li-ion packs up to 24V; packs above 24V should have balancing. Most balancing is passive; active balancing is complex and is only used in very large systems." 

What a BMS does not provide:

- cell undervoltage detection: (except the new ninebot BMS -  they imo report cell undervoltage!)

A lot of excellent information has been provided in this thread, to add a bit more:

• Cell balancing isn't overly important because battery packs have uneven wear due to uneven heating. Cells on the inside of the pack cannot shed heat during discharge and charge, and heat ages cells. (Cells generate heat, and are surrounded by cells generating heat, with no real cooling ability. This is partially why Tesla car company flows coolant through the battery packs.)
• Passive balancing works well, but not with fast chargers unless the BMS is designed to handle fast charging (they are not). While cost is a driving factor in supplying low-current chargers, so are parallel charging considerations. (Parallel charging adds many non-obvious risks; EUCs usually have many cells in parallel.)
• Passive balancing does not monitor for dead (0V) cells. 0V cells pass the full current and voltage to remaining cells, which is one reason why BMSs shut down charging if any cell is over-voltage. Because there is no alert, this can lead to prompt battery failure as cell balancing is not occurring, worsening the problem. It is up to the owner to determine the EUC charge cycle is "shorter than normal" and range is degraded. This is not stated in any EUC manual I'm aware of, making the risk to the owner much higher than necessary.
• Charging batteries to only 80% does not activate balancing circuits, which is dangerous and does not prolong battery life in EUCs. 80% charge is done in R/C with Smart Chargers that balance cells at the set voltage--they are designed for this, EUC BMSs are not. As such, usual practice should probably be to charge batteries to 75% for storage, 100% for usage.

[.....]

On 8/10/2019 at 10:20 PM, Boogieman said:

Made in China when i was young used to mean crap, now they make all the shit in the world, but hopefully it's better manufacturing practice when they get the schemes from trusted us/eu developers than when they skimp on components like this to keep cost down. Who wouldnt gladly pay an extra 100$ for a safe charger and batt pack? That would cover the costs with huge MARGIN to make something robust.

A LOT of people wouldnt pay the extra $100. Havent you seen how high amazon stock has soared? We like to think that consumers will opt to pay more for better quality and for assurances of warranty. We like to think that people may pay more, as they know the food on their neighbors table depends on it. Alas, the truth is in the numbers and its harder to ignore than to accept it: people will try to save money no matter what, and people will patron you for only as long as you are cheapest. Brand loyalty and purchasing based on quality, is not the typical behavior of consumers.

I think it's a shame that competition in price has been the driving factor in a LOT of these decisions. I would gladly pay a LOT more for higher quality wheels and safer battery tech. However, I am in the minority, as the endless bitching about prices of toys, isnt calming anytime soon. I mean hell, people are buying $1 hamburgers and $.05 'chicken' nuggets. These are things we eat!

[Alj]

On 8/8/2019 at 8:27 AM, Boogieman said:

This one being probably the most Dangerous. Originally those loose silicone tubes just slide back and forth over the bare motor cable metal connectors by just pushing them (imagine sustained vibration making them move 1/1000mm per vibration). I just pushed 2 by hand (really low force) and voila bare metal open for shorts. 

Oh man! Why couldn't they use automotive waterproof connectors there? It hurts to see this.

 

[Planemo]

Yeah that's pretty poor. On the MSX the motors wires go directly from the motor to the board - no connections at all. Any other connection on the wheel (that's carries any importance) is either XT60 or XT30.