Batteries - We have the power

As underwater photographers, we rely heavily on batteries to power our strobes and other gear. There are a lot of different battery types and chemistries to choose from, but not all types are suitable for all condition

 
Photograph: Pixabay

Photograph: Pixabay

 

Diving in the cold water here in Norway, and even in warm water like in the Mediterranean sea, can prove challenging for many batteries. As we know most types of batteries loses a lot of effect in colder environments. As an example, I tried using normal Duracell AA alkaline batteries on a dive on Malta, a warm water destination, and the batteries lasted for about 50 shots, I usually take around 150 images during each dive. In comparison, when using Energizer ultimate lithium AA batteries the batteries last for about 300 pictures, even in the cold winter water of Norway, making one set of Energizer lithium batteries last for a whole dive day.

Many strobes and similar underwater photo gear comes with integrated Lithium polymer batteries nowadays.  The big advantage of integrated LiPo batteries is, of course, the fact that you do not need to worry about buying new batteries. The downside is, the battery is not replaceable by the user so you are dependent on either a regular USB wall charger or worse, a proprietary charger. In most circumstances, this is not a problem, but when it is, it is a significant annoyance. Here is just a few of the situations that I personally have encountered, The proprietary charger is forgotten and is half a world away when I need it, The battery dies for an unknown reason, and of course the classic, forgetting to charge the battery, and the strobes stops working 5 min into the dive, since I did not have backup batteries with me on the dive boat. For this reason, I prefer to have user replaceable batteries. I also favor to use standard sized batteries, so when I am on a remote island, I can go to the local minimart and get batteries that are suitable, and when I am using user replaceable batteries I can add the batteries to the save-a-dive kit, so in the worst case, I can change the batteries on the dive boat.

 
Photograph: Michal Kulesza

Photograph: Michal Kulesza

 

The Energizer Ultimat lithium, a brand name for lithium-iron disulfide batteries, works great in cold conditions, are standard AA and user replaceable, so this solves the problem, right? Well, there are some significant downsides with this solution, the first one is the fact this battery type is not rechargeable, so for two strobe that uses 4 AA batteries each, with 4 dive days a week, resulting in around 1600 batteries a year, and that is just for the strobes. Using so many non-rechargeable batteries is not very environmentally friendly, and where I live, those batteries cost about 10 USD for a pack of four. Underwater photography is costly enough even without this added cost of disposable batteries. One more problem I have faced is traveling the globe to a remote jungle island with hundreds of lithium-based batteries is problematical, both in regards to airlines regulations and wasted space in the suitcase.

I have been in search for a solution to this problem for a while, and recently I stumbled over a Chinese company called KENTLI who produces lithium polymer batteries in AA/AAA form factors so you can use them instead of disposable lithium batteries, alkaline or NiMH batteries. LiPo batteries normally have a nominal voltage of 3.7 volts, which is no good if the electronics expects the 1.5-volt standard AA batteries deliver. The KENTLI AA LiPo batteries solve this problem by integrating an electronic circuit inside the battery, that regulates the voltage down to 1.5 volts. This approach also has a nice side-effect, I will not go into discharge graphs and the technical stuff here, but this means that you can squeeze more juice out of the batteries, so you get more run time than you might expect from the mAh rating. The one drawback of this is that you need specialized chargers to charge the KENTLI batteries, generic LiPo charger won`t work, and might even ruin the batteries.

 

 
Photograph: Kentli Inc.

Photograph: Kentli Inc.

 

I haven`t tested the KENTLI batteries fully yet, so it is too early for me to recommend them or not, but so far it is looking very promising.

EDIT (04.09.2018): After comprehensive testing of the KENTLI batteries in real-world situations I have found the voltage regulator in this type of batteries is prone to fail, making them not suitable for critical applications
 

So to summarize:
Alkaline batteries

  •     + Cheap.
  •     + User changable.
  •     + Comes in standard AA/AAA sizes.
  •     - Weak cold water performance.

    - Non rechargeable.    
NiMH batteries

  •     + Rechargeable.
  •     + User replaceable.
  •     + Cheap in the long run.
  •     + Comes in standard AA/AAA sizes.
  •     - Weak cold water performance.

Lithium-iron disulfide batteries

  •     + Excellent coldwater performance.
  •     + User replaceable.
  •     + Comes in standard AA/AAA sizes.
  •     - Expensive.
  •     - Non rechargeable.

KENTLI LiPo 1.5v

  •     + Excellent coldwater performance (haven´t tested it in extreme conditions yet).
  •     + User replaceable.
  •     + Comes in standard AA/AAA sizes.
  •     + Rechargeable.
  •     + The discharge curve gives us longer run time than other types with the same mAh rating.
  •     + Very stable voltage output.
  •     + Cheap in the long run.
  •     - Requires proprietary charger.
  •     - Not suitable for electronics that uses the voltage to estimate the remaining battery life.
  •     - Somewhat expensive upfront cost.
  •     - The voltage regulator chip in them is prone to fail.

Integrated LiPo Batteries

  •     + Excellent coldwater performance.
  •     + Rechargeable.
  •     + No need to worry about bringing batteries.
  •     - Not user replaceable.
  •     - Not possible to bring backup batteries with you.
  •     - Might require chargers that you forgot to pack.
  •      - If the battery becomes corrupted the gear is dead.

The list of battery types presented in this article is by no means comprehensive, and there are many other types of battery types out there, like Lithium-Thionyl chloride batteries. The main reason other battery types are not included in this article is that I have little or no experience with those, the battery type is non-standard either in physical size or in voltage rating or the battery type are specialized, hard and \ or expensive to get hold of.