I purchased a Profoto B2 250 Air TTL Location Kit which comes with two lithium ion batteries. Unfortunately, other than testing it when I got it, I never really needed to use the second battery as my first battery seemed to hold up for most jobs. When I went to charge it recently, I found that it could no longer take any charge and was completely dead. Unfortunately, it's out of warranty so there's not much Profoto can do.

Has anyone successfully revived a Profoto B2 Li-Ion battery after it's been fully discharged?

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    Whilst this might be perfectly valid information, as it stands it doesn't fit the accepted Stack Exchange format, which is strictly Question & Answer. It is perfectly acceptable [& indeed encouraged] to answer your own question, so if you could reformulate it as a distinct Q&A, I'm sure the membership here would be more than happy to welcome your contribution. [Another note: if you link to an external site with instructions etc, it's best if you at least précis that information here, just in case of future link-rot] – Tetsujin Dec 24 '17 at 13:43
  • No problem. Do you have an example where some one has done this so I can follow the same format? – Sam Dec 24 '17 at 13:52
  • As a truly wild example, I picked this one. The simplest of questions, with an absolute killer set of answers - photo.stackexchange.com/questions/6598/… So, for your issue, I'd maybe take time to explain these batteries have a known issue if left fallow for a long time, 'wonder' how it could be fixed - a bit of anecdote is fine, your backstory etc. Then you can put all the detail of the fix into the answer. As you've invested the time & effort so far, as a first time contributor, I'm sure people will help out if you have any queries on format etc – Tetsujin Dec 24 '17 at 13:58
  • Note, too, that comments are ephemeral - the Q/A is what ought to stand over time, as a googleable reference for the future, so this conversation will no doubt be tidied up once we have the final QA in place. If comments get too long, there is an option to move the convo to a separate chat room, where details can be ironed out without cluttering the comment space. & btw, there's really not a great deal wrong with the content of your original post, so mainly the exercise is just to separate Q from A] – Tetsujin Dec 24 '17 at 14:03
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    Hi Sam, welcome to Photo.SE. After reworking, this is a good first post. It probably won't receive too much upvoting love here (it's a rather specialized, narrowly-focused question/answer), but I doubt it will receive any hate either. Great job, nice write-up! Also, excellent guidance, @Tetsujin! – scottbb Dec 24 '17 at 15:26

Do NOT do this.

Please read this post from Electrical Engineering SE regarding Li-Ion battery.

Li-Ion have one failure mode. Fire. And it's not a normal, lighter fire, or even a stove fire. It is a fire-that-burns-in-a-vacuum fire. It's a fire-that-reacts-with-water-and-air fire.

Li-Ion is not the battery type to play around with. They are dead not because the chemicals are not working. They are dead because the safety circuit shut off the battery to prevent it from exploding and causing lots of damage.

  • Actually, early pre-safty Li-ion cells had two failure modes. One makes your model RC plane fall dead out of the sky; the second destroys the plane in a ball of fire. That is, it will either fail open-circuit or short-circuit. – JDługosz Dec 25 '17 at 7:14
  • Three failure modes. Lithium ion packs typically have a low-voltage cutoff to prevent the battery from discharging to the point where cell damage would occur. Unfortunately, often the charge controller circuits in the batteries are poorly designed, and don't come back up correctly after the power is disconnected, so the batteries are bricked as soon as they drop below the low-voltage cutoff. Chargers often refuse to charge them at that point, even though the pack would work just fine if you could bring the battery back above the cutoff voltage. – dgatwood Jul 23 at 4:03

Disclaimer: I cannot be held responsible for any damage, injury or risks associated with what I am about to describe. This is an account of my own experience. Please proceed at your own risk.

I've seen a few posts out there where some of you have experienced the same misfortune I have with having your additional profoto B2 lithium Ion (Li-Ion) battery become discharged due to lack of use and then find yourself in a position where it seemingly fails to recharge. What's worse is that Profoto's solution is for you to shell out $230 for a new one. It's an incredibly frustrating situation, especially when you haven't even had a chance to use the battery. I had the same situation happen to me and was able to successfully revive my battery.

In my case, my second battery was only used when I initially purchased the Profoto B2 250 Air TTL Location Kit. I tested both batteries to make sure they were working and then let one of the batteries sit for nearly 2 years as the first was seemed to be sufficient for most of my shoots. So I'd simply recharge it prior to every shoot that seemed to be enough. Plus, swapping the batteries take a tad bit of effort so I didn't feel super motivated to do so. Then one fine day the need arose for me to prepare for longer than average shoot and therefore needed to have my second battery prepped and ready to go. So I went to charge my second battery only to find that it would not recharge. The charging units lights didn't display the climbing LED sequence that would normally indicate the battery was charging. I left it overnight but nothing changed. I then contacted Profoto only to find that my battery was out of warranty and the best they could do was offer me a modest discount on a new one, which after shipping and handling and the requirement to ship my old one back didn't save me a much versus buying a new battery outright. Feeling frustrated, I nearly placed the order for a new one, but before I did I decided to do a bit of googling and then came across this wonderful video.

There were a number of other videos like it but I felt that this one best covered the situation I was potentially facing as well as the fix. So I decided to follow a similar procedure with my own dead B2 Lithium Ion battery. In my case, I used a Paul C Buff Vagabond Mini Battery as my "known good" battery and connected positive and negative leads to the corresponding connectors on the known good battery first, being sure to keep the free ends apart so they don't short and destroy the known good battery. I then connected the free ends to the corresponding positive and negative terminals of the dead b2 battery (note I did not have to dismantle the battery as shown in the video -- the leads were connected to the corresponding negative and positive terminals of the dead battery...that is negative to negative and positive to positive). I then found a way using non-conductive material to hold the leads onto the terminals of the dead battery so they stayed in persistent contact.

I initially let it sit for 2 mins which did not create enough of a minimum charge for the regular charger to work. I then let it sit for 30 mins. This created enough of a minimum charge in the dead battery for the charger to then takeover and fully recharge the dead battery back to life. It's been working ever since.

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    Note that once a Li-ion battery has been deeply discharged, it's no longer safe to try to revive it. See answers to If Li-Ion battery is deeply discharged, is it harmful for it to remain in this state unused? question on Electronics.StackExchange for details. – Ruslan Dec 24 '17 at 18:21
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    Please note that this procedure bypasses the chargers safety protocols. The risk of doing this is internally perforating the battery (due to "spikes" built up by the internal battery chemistry) and a failure mode that ranges from venting to vigorous fire. – casey Dec 24 '17 at 18:50
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    @casey Once a Li-Ion vents, it'll eventually generate fire because the battery is already experiencing thermal runaway, which accelerates the reaction. A venting Li-Ion is extremely dangerous, because you can't do anything to stop the reaction. Water does not stop it. This type of fire can burn in a vacuum. Don't underestimate a Li-Ion fire. – Nelson Dec 25 '17 at 2:46

image of two battery packs connected positive to positive; negative to negative

I experienced two “dead” Profoto B2 batteries. Tried what was described here, but could not make it work. Disassembled both the working battery and the faulty one. Measures close to 0V on the faulty unit, above 16V on the working battery. I hooked up two wires: positive to positive, negative to negative. Let it sit a couple of minutes and observed both batteries go down to 14.8V.

The working battery shows two lights on the indicator and took charging well. The faulty batteries showed 13.8V standalone, and at first it did not charge. It was quite hot, so I let it sit for 10 minutes to cool. When I plugged the charger to the faulty battery, charging worked perfectly! Now I have all batteries in working condition!


Yes the B2 battery does discharge when connected to the B2 control unit, yes the price of the battery is a real killer, so your average user will try anything. Yes I got the same dead results as SAM showing dead battery. Tried charging with control unit for 12 hour, then without for 24 hours, Yes same as SAM got. An old IT (30 years and counting) trick for laptop batteries is heat the battery up in front of a fan heater then put back on charge. Tried and no joy, then the second thing was press the battery test button for 20 seconds and then connect to charger with button pressed and released after charger connected, seemingly nothing at first. Within 20 minutes the charger kicked in with the charger bars lighting up and confirmed charge via the charge test button. Make of this what you will, but I saved the cost of a new battery by doing it. If it failed then I would try the residual charge method, the price of these batteries are ridiculous.


It is bad idea to just hook up other battery. What I would do is: take it apart carefully then test each cell voltage, anything under ~2v (depending on battery specs) goes to recycling, than trickle charge good one's up to 3v, after that charge cells. Than test for self discharge - if it is too high then it goes to recycling. Impedance also should be done!
And in the end use good cells. No job is so urgent that you can not do it safely, so never try like that guy charging from other battery! That's what happens when you don't know what you buy cause these batteries are worth less if you don't use them. And optimal storage conditions is to store them at 40% charge disconnected in cool (10°c - 24°c) dry place. That way it will hold charge longer.


Do you disassembly battery? Try to disassembly and measure voltage on banks.If it is not less 2.5 volt, try recharge banks at outside source. Good luck!

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