Perdix AI / Perdix 2 battery display changes during/after dives

[Capt Jim Wyatt]

I never remove the battery from my Shearwaters. I have seen bad batches of these and other type batteries.

 

[BlueTrin]

Do you leave the battery in the computer inbetween dives? I take it out if I am not diving the next day. I wonder if there is a small current draw even when off that reduces the duration of your batteries

I would be more worried of damaging the o-ring tbh if I was removing the battery so frequently. However if you use Alkaline, you should remove it if you don’t use the computer for an extended period because of possible leakage, but that’s not in days.

 

[BlueTrin]

I never remove the battery from my Shearwaters. I have seen bad batches of these and other type batteries.

It’s hard nowadays to know if you bought genuine batteries …

 

[Kendall Raine]

There is at least one other thread about Perdix batteries being displayed with much lower voltages during dives:

Perdix 2 Energizer Ultimate voltage drop during dive

I bought a Perdix 2 recently and used it on its first trip. A strange thing I noticed which is leaving me in doubt, is that the stock Energizer Ultimate battery voltage seems to drop a lot during the dive compared to pre-dive. After only about 20 hours of diving it prompted me LOW BATT INT...

scubaboard.com

And following advice in that thread I looked at the plot of battery voltage during the dives. Not very informative, as they all show a straight-line with a voltage reading of 1.5V (what a fresh AA should have), even though the display definitely changed (a lot!) during the dive. I think the "plot" is just showing the expected voltage for a battery of the type inserted, not the actual voltage.

I have experienced the same pre-during-post dive (blue yellow blue) variation in the battery “fuel gauge.” The battery line on the cloud dive profile shows straight line voltage during the dive (which is what I would expect). I then looked at the voltage line from the first dive in the series to dive 20 at the end of the week. The line on the graph was straight on all profiles, but dropped from 1.5v to 1.3v over the week. Again, what I would expect. That was with Duracell Allaline AA’s. I’m stating the think the fuel gauge doesn’t work well, for whatever reason, in some (many) units and voltage is a better metric.

I recently switched to Energizer Lithium’s because of leakage concerns and will keep an eye on the same metrics.

Has anyone empirically determined the minimum voltage? That is run it until it dies and then checked the voltage.

 

[GF99/99]

My Perdix AI and my buddy's Perdix 2 both show the same odd behavior: the battery level appears full (or >90%) before the dive, but shortly after jumping in it drops 30-70% (and shows yellow instead of blue). After getting out of the water it recovers to about the same as before the dive. We're both using (edit) EverReady Energizer Lithium AA batteries. Needless to say, it's easy and cheap enough to swap out the battery after seeing it in the yellow during the dive but I didn't expect Li batteries to show any "rebound" effect and appear 90-100% after the dive. That's actually very misleading if you're deciding whether to change to a fresh battery.

Maybe this is related to the power drain when communicating with the transmitter (10 sec intervals)? FWIW, I have an old transmitter from a different AI PDC, but my buddy has a brand new Swift and we both see the same thing. My battery had ca. 35 dives on a fresh AA before hitting the yellow during a dive today.

Any thoughts?

PS I've been using my Perdix AI for about 150 dives and never noticed this behavior until recently. Something different in a recent firmware update?

As others have mentioned as well I have seen the same thing as well with Energizer Lithium’s. I run all rechargeable in my Shearwater platforms and no issues now. But the rechargeable don't last as long as the Energizer however who cares, they are rechargeable. I find they get to about half after about 20hr. I always just throw them on the charger when they are about half. Cheap insurance to know you will never have a dead battery, the luxury of rechargeable batteries you should never get close to having a dead battery.

 

[mje113]

Glad I found this thread as this just happened to me last week. I was seeing yellow on all dives, and it dropped to a bit below 20%, so planned on replacing the battery when I got home. But when I turned the computer back on it was showing 90% blue.

If this issue is specific to Energizer Ultimates (I'm still on the factory battery at 17hrs, but got energizers for replacement), what's a good alternative lithium brand to switch to that would actually work?

 

[Kendall Raine]

I always just throw them on the charger when they are about half.

Do you swap between rechargeables or top up the one and get it back in the computer before the super capacitor runs out?