Navigating in Darkness

[rjack321]

I am fully aware of the shifts in voltage in a NiMH battery pack throughout its charge cycle. Not that hard to monitor and track current-in if you're concerned about it.

Have fun riding your flooded beast when you skipped a backup. You bring an extra wing to keep it from plowing a furrow? I suppose your still using a SLA canister light too eh?

 

[Orlando Eric]

Okay, so in order to see my compass in the dark I have to buy a scooter and a backup scooter?

Screw that I'll just dive during the day.....

 

[Jason B]

I am fully aware of the shifts in voltage in a NiMH battery pack throughout its charge cycle. Not that hard to monitor and track current-in if you're concerned about it.

He's talking about the discharge cycle not the charge cycle.

 

[MXGratefulDiver]

Which brings us back to the question ... how would you read your scooter while discharging your compass in the dark ...

... Bob (Grateful Diver)

 

[rjack321]

He's talking about the discharge cycle not the charge cycle.

It doesn't really matter, I was refering to getting a consistent charge. For which a NiMH should be in series, not parallel like some light manufactures make them. Regardless SLAs are not the solution to unknown burn times or conservative use (like 1/3rds).

Of course the OP doesn't have a scooter at all and there's no elegant way for him to shine his light on the left wrist. Hosed, totally hosed.

 

[Soggy]

Another reason for the use of SLA in scooters is because they don't go along at seemingly full power and then just shut off like NiMH. SLAs will progressively get weaker and weaker, but allow you to still use them. When they do die, a few minutes off the trigger, and they will rejuvenate a bit so you can continue to use it again. This could prove useful, depending on the situation.

 

[RTodd]

Another reason for the use of SLA in scooters is because they don't go along at seemingly full power and then just shut off like NiMH. SLAs will progressively get weaker and weaker, but allow you to still use them. When they do die, a few minutes off the trigger, and they will rejuvenate a bit so you can continue to use it again. This could prove useful, depending on the situation.

Exactly, because the voltage steadily drops on SLAs as they age. Assuming you have burn tested recently, checking the voltage on a SLA prior to the dive is a very good indication (i.e. betting your life on it for exploration dives) of how long the battery will last since SLAs don't just crap out, they decay over time (obviously there are rare exceptions). NiMH can go from full voltage to dead in minutes without any warning. For NiMH the voltage at the start of the dive is completely useless for determining the expected burn time. The voltage drop occurs right before the battery is toast. The effort put into making the old Ni-Cad scooters (similar but more pronounced problems than NiMH) usable as exploration scooters was ridiculous and not worth it.

I need a way to mark the non-singing pigs so I don't accidently try to explain this stuff to them. Thank goodness this is a threadjack and there is little risk of a person that actual wants useful information stumbling on this thread with a search.

And yes, I do still use SLA batteries in my dive lights when the dive time allows for it and I am going to a location where I leave cannisters. HID and NiMH is a necessary evil that is worth it for the performance but is far, far more failure prone than older halogen SLAs. (I don't use halogen anymore but I miss it's greater reliability.)

 

[dsteding]

Exactly, because the voltage steadily drops on SLAs as they age. Assuming you have burn tested recently, checking the voltage on a SLA prior to the dive is a very good indication (i.e. betting your life on it for exploration dives) of how long the battery will last since SLAs don't just crap out, they decay over time (obviously there are rare exceptions). NiMH can go from full voltage to dead in minutes without any warning. For NiMH the voltage at the start of the dive is completely useless for determining the expected burn time. The voltage drop occurs right before the battery is toast. The effort put into making the old Ni-Cad scooters (similar but more pronounced problems than NiMH) usable as exploration scooters was ridiculous and not worth it.

Thanks for this, that is one of the more concise, better reasoned arguments for SLAs that I've seen. Certainly something to consider in buying a scooter-although I don't know if I'll ever be in a situation where the scooter crapping out on me means my life. Understanding the tradeoffs on these things is very useful in becoming a more educated diver.

 

[RTodd]

Thanks for this, that is one of the more concise, better reasoned arguments for SLAs that I've seen. Certainly something to consider in buying a scooter-although I don't know if I'll ever be in a situation where the scooter crapping out on me means my life. Understanding the tradeoffs on these things is very useful in becoming a more educated diver.

NimH has its place. I have several Gavins and considered buying some NimH scooters when I lived in the South Pacific since you don't need a heavy reliable scooter to go play in the ocean and the lighter scooters are nicer for boat and beach dives. But, I don't use scooters in open water enough to justify having that many expensive battery packs sitting around going bad. We used short bodies in the coral sea several hundred miles offshore on a few occasions. Diving sites a mile away from the boat was cool and since the tenders are watching for you a failure of multiple NimH scooter batteries would not be a big deal. But, IMHO the increased reliability and durability of the SLAs outweighed the added effort of getting them on and off the boat.

 

[dsteding]

Diving sites a mile away from the boat was cool and since the tenders are watching for you a failure of multiple NimH scooter batteries would not be a big deal. But, IMHO the increased reliability and durability of the SLAs outweighed the added effort of getting them on and off the boat.

Whatever scooter I purchase, I'll be using it in only open water situations, eventhough I do see Cave 1 in my future at some point, I'll probably never spend enough time in a cave to be able to use a scooter in one. So, I'm looking at scooters to be used from shore locally, from boats in BC on wrecks in the 100 fsw range, and to travel with for recreational/tech 1 use overseas. Honestly, with the X being built locally, being light enough to travel with and handle from shore, and for the uses I am contemplating, there is a huge incentive to buy one, but I haven't ruled out other options.

Right tool for the right job, my goal is to make an educated decision on what that tool is for my purposes.