Overly discharged 40ah LiPO battery... restorable?

[woytovich]

I'm a dope and (apparenty) left a trickle discharge happening on a 40ah LiPO battery. It is discharged to 2.7 volts and won't recharge with my LiPO charger. Has anyone has success getting something like this back to at least usable condition. I see info on the interwebs bout doing so with small lipo batteries for RC cars etc... something called a "boost" mode.
Any info would be appreciated.
Thanks.

 

[Prairie Swamp]

I actually forgot I had a small Hitachi Li-ion drill and it sat unused for years. One battery pack took a charge one wouldn't. Did web searching. Of course it depends on your particular setup. But my charger wouldn't recognize the battery because the voltage was too low. The web recommended using an old wall wart charger to give the battery pack a quick jump. I think I applied 19 volts for maybe 10 seconds. As I recall voltage went from 2ish volts to 7ish. Dropped it in the charger quick and it recognized the battery and charged it. Worth a shot.

 

[thegadgetguy]

On much smaller LiPos I've used the technique Prairie Swamp described of charging with a non-LiPo charger for a few minutes to get the voltage high enough that the LiPo charger will recognize it. I have a charger that will do a bunch of different types of batteries and used the NiCad charge profile set at fairly low current. I just watched the battery voltage until it was above the minimum the charger would recognize as a LiPo, and then switched over to the LiPo profile.

 

[e9999]

One bit of kit I'd recommend to have around is a small bench CV/CC power supply to help with battery charging chores. You can get one that would cover 15V and 5A for less than $50, and a 30V 10A for less than $100. You can set the voltage and current to your choice of max values and it will switch from one to the other as needed. So quite safe to use (if you don't bump the controls by accident) for charging batteries. Can replace various chargers in a pinch but also give you full control over such things as upping voltage to the point a dedicated charger recognizes the battery as in the above, with much less uncertainty than the various sorts of improvised techniques you see mentioned around.

 

[woytovich]

One bit of kit I'd recommend to have around is a small bench CV/CC power supply to help with battery charging chores.

Can you recommend one, seems like the lower range would do for 99% of what I might need.

 

[e9999]

I bought an inexpensive chinese one recently. Did the usual check on specs and reviews on amazon and YT. Honestly, it was more a guessing game than a highly-supported choice at the end, and I'm sure the prices and specs change all the time. There are tons of those. Mine works fine with just one semi-annoying quirk. And the current values displayed are fairly accurate, even on the lower end; but the voltage is right on, which matters more for battery charging. In fact, I also have some older much better lab-quality ones but I end up using the new little guy most of the time, way more convenient and especially much smaller on the bench. One thing I would do now, though, is try to find one that has locking adjustments for V and A, cuz you really don't want to bump the voltage knob by accident and have it go to 30V on your lithium battery..., but I suspect those are probably found in a much pricier category.
You can charge a number of types of batteries with just a CC then CV scheme with the typical PSU, and some of the Lithium types are easy in that respect. You basically have a fully-adjustable battery charger.
PM me if you'd like to know my specific model but, honestly, I can't really recommend it much over others.


added: as to your specific situation, keep in mind that there are 2 issues there, one is the recognition by the charger -easy to fix usually and what we're talking about above- but the other one is that some lithium batteries will get permanently damaged if discharged too much and I don't think you can do much about that.

 

[woytovich]

I was able to bump it up to a 4.3 volt reading (just after removing the low watt/low amp wall wart charger). Now, 24 hours later, it reads 2.8. Even when at 4+ my Battery Tender wouldn't start charging when in LiPo mode - it WOULD charge in AGM/Flooded mode. (Deltran tech support told me: "All of our chargers require at least 3 volts before it will start to charge a battery.")
Soooo I'm thinking this thing might be beyond help.... I will probably give it another try in any case.