Perdix AI AA Battery

[Hoag]

I'd like to thank @HKGuns for starting this thread. As they say, timing is everything.

I bought a PERDIX AI in January and I haven't used it yet. I did, however, put an Alkaline Battery (Energizer MAX) in it to do the set-up and left it in there when I was done. After reading this thread, I went out yesterday & picked up some Energizer Ultimate Lithium batteries just to be on the safe side. I don't know when I'll be able to use my new computer, but at least now, I won't get and unfortunate surprises from the battery when I do.

BTW, how long do fresh Lithium batteries last (roughly)? For instance if I go on a week long LOB and do 25 dives over the course of the week, will I be changing batteries mid week or would I expect to get through the week on the one battery?

 

[Paul M]

I'd like to thank @HKGuns for starting this thread. As they say, timing is everything.

I bought a PERDIX AI in January and I haven't used it yet. I did, however, put an Alkaline Battery (Energizer MAX) in it to do the set-up and left it in there when I was done. After reading this thread, I went out yesterday & picked up some Energizer Ultimate Lithium batteries just to be on the safe side. I don't know when I'll be able to use my new computer, but at least now, I won't get and unfortunate surprises from the battery when I do.

BTW, how long do fresh Lithium batteries last (roughly)? For instance if I go on a week long LOB and do 25 dives over the course of the week, will I be changing batteries mid week or would I expect to get through the week on the one battery?

I was getting about 35 hours on Energizer Max Alk batteries. This includes bluetooth uploads to the Subsurface and Shearwater smartphone apps after each dive day. I switched to the Energizer Lithium AA, 5 dives ago (7.5hrs) and the needle has barely moved
Mainly cold water diving.

 

[rhwestfall]

Just went and looked at the battery information from my last trip (SW Cloud lets you toggle battery voltage on the graph). Using Energizer Ultimate Lithium cells, the battery indicator basically didn't move in 9 1-hour dives on a week long vacation (0.1v). I don't remember if I was dumping logs or not each day, or if I waited until home that trip.

A "card" of 4 batteries should do you fine. That is usually what I always carry.

 

[Rollin]

Before my DC was stolen in Tenerife, I used to put Eneloops in my Perdix as well. I could do around 30 dives with one battery, even in very cold water. One thing I noticed: when the battery indicator went to orange, the battery was almost dead empty.
Don't do a long dive then. Change every 20 dives or so and you will be fine.

 

[Belzelbub]

When I got my Perdix AI, I was somewhat surprised to see that it had an alkaline battery in it already. Not sure if this was done by SW, or by the LDS. Anyway, I had already decided that I wasn't going to use alkaline batteries (except if needed in a pinch) due to their tendency to leak. On another forum, there was a recent discussion about some name brand alkaline batteries starting to leak in the package, so I'm glad I didn't use those. Although I try to dive fairly regularly, sometimes life gets in the way, so I could see where I might have occasionally left them in longer than 1-2 months.

So, alkalines were out.

I also wanted to use batteries that are compatible with the "Fuel Gauge." This removed NiMh, SAFT. Not sure if the photo lithiums are compatible. I believe the photo lithiums tend to keep full voltage for a while, so I don't think they are compatible. SW's battery guide doesn't say one way or another on these.

I ended up going with the 3.7V Li Ion 14500 rechargeables. I ended up getting a 4 pack, and I bring a spare with me, and leave the other two at home. Those should last me for a good long time.

So for me, it's:
Plan A: 14500 rechargeable
Plan B: Photo Lithium
Plan C: Alkaline (and they'll be removed once I get back home and can revert to Plan A.

 

[tmassey]

I’ll add my anecdote to the list.

I use Eneloops. I’ve only ever used Eneloops.

There’s no real risk of those battery leaking. Theoretically, any canister could leak. But the reason why alkalines are so susceptible to it is the canister is actually a functional part of the battery. The more juice you pull out of the battery, literally the more it eats away at the canister. That’s why alkalines will leak if you leave them in a device for a long time. The vast majority of modern devices aren’t actually off, ever. That means they are always using a tiny bit of juice, and eventually the battery *will* discharge until there’s a hole in it. Guaranteed.

Rechargeables and lithium batteries don’t work that way. So they won’t leak like an alkaline will.

There are two drawbacks of Eneloops (specifically, low self discharge nickel metal hydride rechargeable batteries):

One: nickel metal hydride batteries have a very flat discharge curve, with a very steep bend at the end. In other words, a battery that’s almost full looks just like a battery that’s almost empty. So battery meters are useless. You see that with the Shearwater computer. It practically only has two states: completely full, then yellow warning. There’s never a drop in the meter as you use it. (Maybe it goes red or some thing later: I’ve never tried to find out.)

How long you get between yellow warning and dead is variable, of course. I have not found it to actually be a problem. I have had it turn yellow on a dive, and then completed even the next dive in that state: call it more than an hour of run time in the yellow warning state. (These were recreational level dives, so I was willing to take the risk rather than risk the entire computer by changing batteries on a bouncing boat.) Having the battery meter turn yellow is far from an emergency for the vast majority of dives.

The other drawback is the relatively low capacity of nickel metal hydride batteries. There’s a reason the world has moved to lithium batteries. The power density of nickel metal hydride just isn’t there. So you don’t get nearly as many dives out of an Eneloop as you would out of an alkaline, let alone anything lithium.

Even that one’s not much of a drawback. I probably get a minimum of 10 dives of plus or minus 45 minute duration — and I actually think it’s more than that. If I am doing multiple serious dives (say, multi-hour cave dives) I simply replace the battery every two days, which still puts me way under the runtime I have already proven I can get. Otherwise, I wait for the meter to turn yellow and change it at the end of the day. So for me, that works just fine.

Seeing as I have standardized on Eneloops in my regular life, I have probably 50 or more. I doubt any single battery has been charged more than a dozen times. I also have a high-quality charger that shows the capacity of the battery, which lets me monitor their condition. Given that infrastructure, using Eneloops in my Shearwater has been far from an issue.

 

[Mark IV]

Not sure if the photo lithiums are compatible. I believe the photo lithiums tend to keep full voltage for a while, so I don't think they are compatible. SW's battery guide doesn't say one way or another on these.
.

According to the engineering manager at Shearwater, "The Energizer Ultimate Lithium batteries are a good choice."
He goes on to say, "Remember to set the “Battery Type” setting to “1.5V Photo Lithium” when using the Energizer Lithium batteries. If you don’t then the warnings will be all wrong. If left at “1.5V Alkaline” you will not get a low battery warning until the battery very quickly dies. If the other way around (using Alkaline but set to Lithium), you will get the warning way too early. This can be seen from the voltage graph showing very different discharge curves, that I have uploaded here:
Box "

Factors Affecting Battery Life on Shearwater Dive Computers - Shearwater Research

 

[tbone1004]

@Mark IV would be great if @tcoen or @Shearwater would be able to update the battery recommendations on their website, fingers crossed since there have been advancements since the last was updated

 

[KenGordon]

Is there any reason to NOT just pull the battery after every trip? I mean, I'll go diving for a day, then not again for weeks. Or do 3 days of local boat diving, then nothing for a month (or longer). Why not just pull the batteries between trips? Is there something I'm missing?
.

Each time you take out the battery you risk not closing it perfectly again.

It is a balance. My policy is to spend a few quid on always having a spare SAFT but only opening the computer to change a battery, either because it is a long time since I last did it, because it shows not 100% full or if a big deal trip is coming and I want to get a dive in before hand so I have a chance to sort out a flooded computer.

 

[KenGordon]

BTW, how long do fresh Lithium batteries last (roughly)? For instance if I go on a week long LOB and do 25 dives over the course of the week, will I be changing batteries mid week or would I expect to get through the week on the one battery?

You could easily do two such weeks, possibly four.