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Discussion Starter #1
Let’s say you were lucky enough to be able to inspect a module before you buy.
How would you evaluate it the field?
The list might include:
- Physical damage, particularly noting the condition of the fuse wires soldered to the cell tops.
- Voltage? I’m not sure I see much more usefulness than a snapshot from this.
- Use a “pack sniffer” or other device to get more info?
We’ll presume that the vendor won’t allow a timed load test.
How about other concerns?
- Any way to ID when it was built?
- Are there any modules to be avoided? There are different revisions to the circuit board that is commonly replaced by 057, EVTv, or other aftermarket bms boards. Are there modules that Don’t work with these?
Many thanks for your replies.
 

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Biggest risk: coolant leaked into the battery, this causes current leakage and is non recoverable.

how to detect (except visually): cells out of balance.

all cells from a good pack should be the same voltage withing a couple of mV

you can bring a SimpBMS to read out the modules quickly on site.
 

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Let’s say you were lucky enough to be able to inspect a module before you buy.
How would you evaluate it the field?
The list might include:
- Physical damage, particularly noting the condition of the fuse wires soldered to the cell tops.
- Voltage? I’m not sure I see much more usefulness than a snapshot from this.
- Use a “pack sniffer” or other device to get more info?
We’ll presume that the vendor won’t allow a timed load test.
How about other concerns?
- Any way to ID when it was built?
- Are there any modules to be avoided? There are different revisions to the circuit board that is commonly replaced by 057, EVTv, or other aftermarket bms boards. Are there modules that Don’t work with these?
Many thanks for your replies.
First of all, I get my modules from the best source in the country, in fact it’s where most other places get their modules from usually. The place I get them from goes through hundreds and hundreds of modules, and inventory moves fast. But one thing they do best is carefully inspecting all of the batteries, and keeping each pack sorted together with mileage. So a 27k mile pack he keeps together on a shelf, which is absolutely wonderful. When a customer calls and orders modules, I go check with my source to make sure we can secure modules from the same pack, with low miles.

So with that, there’s a 99% chance your modules will be perfectly balanced. I just actually got 7 modules to put into my 96’ Celica convertible, my personal car, and my modules came balanced within 0.006V! Never would’ve imagined I would’ve had a pack that balanced before!:)

Anyways, my source packages these modules extremely well when shipping, which is also very rare these days.

You don’t want to load test, because you’ll get them out of the perfect balance that they’re in, but from this source, I’ve yet to have a bad experience. The modules don’t sag too much under high loads, and they just run really well! Honestly I can’t be happier.

When you order your voltage tap boards, that will replace the OEM Tesla BMS boards, you basically just order for either the older modules with wired connectors, or newer modules with ribbon cables.

If you want some help getting modules from this source, let me know and I’ll be glad to help. I have the best prices on these and the only reason I sell them is to help guys/gals like us get great lithium for the best price we can for our builds.

Cheers,
Adam
[email protected]
 

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Discussion Starter #6
You can tell nothing about a battery’s capacity by voltage alone. A Tesla cell can charge to 4.2V and still only have 50% capacity, or 100%, you can’t tell.
Only a load test will tell you. Tesla does this ($235) for their owners with battery issues: a timed load test to determine battery capacity.
You’d think this’d be a common test for someone selling used modules, but I didn’t find any. Some guys never even did a full charge test. They had them ready to sell, depleted down to 20% to make them safe to ship, never tested, no warranty. And they’re asking $1x00 a module for that? Crazy.
The power blackouts from the fires here in California have every warm body looking for Tesla modules for backups and maybe those guys don’t care so there’s no giveaways. As great as the Tesla modules are, buying salvage is a total crapshoot, even if you have the wreck in front of you (unless you can get the car to cough up it’s charging history). Tesla modules are not immune from age and chemistry. John61ct is absolutely correct.
 

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You can tell nothing about a battery’s capacity by voltage alone. A Tesla cell can charge to 4.2V and still only have 50% capacity, or 100%, you can’t tell.
Only a load test will tell you. Tesla does this ($235) for their owners with battery issues: a timed load test to determine battery capacity.
You’d think this’d be a common test for someone selling used modules, but I didn’t find any. Some guys never even did a full charge test. They had them ready to sell, depleted down to 20% to make them safe to ship, never tested, no warranty. And they’re asking $1x00 a module for that? Crazy.
The power blackouts from the fires here in California have every warm body looking for Tesla modules for backups and maybe those guys don’t care so there’s no giveaways. As great as the Tesla modules are, buying salvage is a total crapshoot, even if you have the wreck in front of you (unless you can get the car to cough up it’s charging history). Tesla modules are not immune from age and chemistry. John61ct is absolutely correct.
All very true indeed! There’s certainly a lot of risk in buying any used batteries with little history known. But if you don’t like the risk, then go get some brand new cells.

All I will say is that I’ve gone through so many modules now, others I know have been going through them like crazy, and I’ve yet to hear of a single issue of the modules I’ve been getting from my source.
 
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