AliExpress: Beware OYE Store!

ptd006

New Member
Joined
Sep 8, 2021
Messages
25
Those cheap capacity testers work fine. Keep it to 15 amps (instead of 20) and it won't blow up.

Thanks. I will order one of the capacity testers.

Following advice in another post I cleaned all the battery terminals and busbars. I had unpacked them all in my gloomy garage and hadn't noticed they were really grimy.

I got a 10A bench supply. It would take too long to charge them from flat with this tiddler. So, I ensured all batteries were charged to ~3.15v and then reconnected (in series) to the Sofar ME3000SP. I just put ~4.5kWh into them and no cell ran away (in voltage terms), i.e. charging seems more balanced than before. So, cleaning the terminals seems to have made an improvement but I will need to see how they behave at a higher state of charge tomorrow. (No more charging tonight so I can go to bed and sleep with less worry!) Hopefully I can get all cells to ~3.50v by charging in series with the Sofar unit. After that I'll disassemble the pack again and charge in parallel to 3.65v with the bench supply.

@Watchout - I scanned 15 out of 16 QR codes and they are all P721s. I couldn't find a QR sticker on one of the batteries- possibly it is on the side of the battery but I forgot to check when I had the pack apart.

They may or may not be perfectly safe, although to my thinking they are much more prone to dendrites and thus internal shorts. Cell manufacturers recommend replacing them when 70 to 80% of original capacity for a reason.
I am a newbie so will need to read about dendrites but I understand there are serious risks with old degraded things that have lots of energy stored in them. I plan to relocate these batteries to a waterproof box outside the garage or sell them and swallow the loss. Really I don't like this game any more. It was supposed to be a "fun" project ahead of getting solar panels installed so I could get cheap electric for working from home and crypto mining.
 

Just John

Photon Sorcerer
Joined
Aug 15, 2020
Messages
2,380
Thanks. I will order one of the capacity testers.

Following advice in another post I cleaned all the battery terminals and busbars. I had unpacked them all in my gloomy garage and hadn't noticed they were really grimy.

I got a 10A bench supply. It would take too long to charge them from flat with this tiddler. So, I ensured all batteries were charged to ~3.15v and then reconnected (in series) to the Sofar ME3000SP. I just put ~4.5kWh into them and no cell ran away (in voltage terms), i.e. charging seems more balanced than before. So, cleaning the terminals seems to have made an improvement but I will need to see how they behave at a higher state of charge tomorrow. (No more charging tonight so I can go to bed and sleep with less worry!) Hopefully I can get all cells to ~3.50v by charging in series with the Sofar unit. After that I'll disassemble the pack again and charge in parallel to 3.65v with the bench supply.

@Watchout - I scanned 15 out of 16 QR codes and they are all P721s. I couldn't find a QR sticker on one of the batteries- possibly it is on the side of the battery but I forgot to check when I had the pack apart.


I am a newbie so will need to read about dendrites but I understand there are serious risks with old degraded things that have lots of energy stored in them. I plan to relocate these batteries to a waterproof box outside the garage or sell them and swallow the loss. Really I don't like this game any more. It was supposed to be a "fun" project ahead of getting solar panels installed so I could get cheap electric for working from home and crypto mining.
Capacity Tester info.

The cells a lot of people are buying are either grade B factory rejects, or removed from service. Yes the chemistry is safer than that used in US electric vehicles. But there is a reason they are cheap.
 
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