If he did not pack it very well, and the power button was pressed there’s a possibility it could’ve run the battery down during the five or so days of shipping transit. But auto-shutoff should have kicked in there.
The only explanation I can really come up with for this battery revival, is that your multimeter is shit and you should get a nicer one.
To elaborate further, sometimes when multimeter batteries get low they show improper readings. How that related to your seemingly successful fix and why the multimeter theory may make sense:
Chargers have a low-voltage cut off, at a certain voltage threshold they will no longer register that anything is connected for charging. That’s certainly the case here, your charger could not recognize how low of a voltage the pack was at and refused to charge.
Generally, my recommendation in these instances is to jump down to a lower voltage output charger such as a 10S charger for a 12S battery, to get things started charging. In your case, you may have been able to charge back just enough juice in the battery to allow the charger to register the pack and begin charging.
This leads me to the theory that your multimeter was lying to you, and you were only slightly below the LVC of the charger, not the pack being nearly stone dead.
I have found, in all my dealings with very odd broken boards, that most people will have an earnestness. However, this doesn’t mean that they have all of the information or expertise to know why things may be the way they are in particular odd cases. There is something, however, that sticks out:
If that’s the case, then that means he’s previous brought a board (I don’t know if you mean to say THIS Nazare, or a different one) down to flat dead.
That gives me a sense that he’s not particularly adept at avoiding the Ravenholms of empty cell voltages.
To your confusion of how motor regen could bring it back up to acceptable voltage, it’s not too farfetched.
In my travels of way-too-dangerous-and-stupid activites of screwing with cells, it’s become very clear that the drop off from 2.5v to 0 is very very steep. Depending on the voltage (or load, if you’re draining) applied, it can be near instant to see a 0.1v cell jump up. The curve flattens very quickly also, despite the ACTUAL amount of energy put into the cell is miniscule.
Addendum:
To clarify: If you have a pack that’s “empty” and you apply a load to it of a few amps, it’ll drop to 0v. You remove the load, it bounces back up.
This is why I’ve found that if you’re trying to drain a pack fully for disposal, you really need to apply a very very small load in order to even observe the energy leaving the cell (through voltage drop), otherwise it’ll just rubber band back and forth.
The voltage below empty doesn’t make intuitive sense. It’s the battery version of Interstellar.
The voltage, as many know, isn’t linear. However since most folks don’t intentionally sit and dangerously discharge cells and recharge them quickly just to see what they’ll do (it’s dangerous, and expensive…but I’m a fool), it’s hard to really intellectualize how quickly that can happen.
If that Nazare has had its battery “kick started” more than once, I wouldn’t personally recommend that you continue using it.
It could be fine. I’m sure it’ll charge and function. But I wouldn’t count on it being safe for really rough use, or for very long. I’d personally start getting my cards in order for a different battery.
I made a video on why I don’t think using that battery is adviseable:
I’m totally famous and a big deal, so you should totally listen to me.
This kind of sparks an interest in making a video about how little there really is between “empty” and “dead flat” on a cell. Could be a fun 1 minute bit.
Anyway, that enclosure looks painfully underutilized. I wonder how much extra could be crammed in there unceremoniously.
Best of luck. Don’t blow up. Especially since it seems fire proof charging bags aren’t a viable idea.
@TheBoardGarage I think you are right. I didn’t think about how steep the voltage curve is from 0.5v to 2.8v.
I believe the seller that it was well balanced and fully charged when he shipped it, so hopefully this is a one time thing where the pack dropped dangerously low. Packing wasn’t the best and I could easily see the board being repeatedly turned on.
Also to your point about enclosure space, yes it’s sadly underutilized. It was designed for 12s6p 20700 and sadly doesnt fit 12s6p 21700
I just bought the paid features in the Xiaoxiang bms app so that I can enable balance when not charging.
@Nordle I wish I had read that before I did my DIY kickstart. I spun the wheels until the voltage hit 28v and then I slammed the 10amp charger on there. I have no idea if I did damage to the batteries bringing them back to life…
The delta isn’t the main factor here, it’s how all of the groups recharged and are behaving. 45mv isn’t too high of a Delta, but a healthy pack of that size shouldn’t go above 20mV.
Plus, this isn’t what you paid for. You paid for a good condition jaws. This is a poor condition jaws. I’d either send it back and buy a Barrell or get a new battery paid for by the seller. My opinion is that this jaws is worth considerably less than what you paid for it as its seemingly been neglected, was defective, or both.
There’s just no way to know what’s going on inside the pack. Dropping below about 2.0V-2.5V can damage a cell but how much, if at all, depends on a lot of things. Which cells, their condition before this happened, how long they were at that voltage, their temps, etc., all affect the possible degree of damage.
It’s why we always just say don’t let it happen. We can’t know what the degree of risk is if it does.
If I’m asked what should be done I am forced to err on the side of caution and to recommend not using the pack and to replace it. I have to say that, we don’t know what the risks of using it are.
That pack might be fine, it probably is, suffering just a bit of capacity loss and internal resistance increase. But if there is even the tiniest chance of it being riskier to use can we say it’s okay?
Each person has to decide what their risk tolerance is, with no info to base it on, and choose whether to use the pack or not. None of us can know.
