Sierra Battery question

[Potapko]

Often two or three months pass between scooter dives with my Sierra. How much should I worry about losing battery capacity?

I have read several cases of batteries needing replacement earlier than one might expect. Is there a way to prevent this? Is it batter to use other battery technology when using a scooter only occasionally?

thanks

 

[Peter_C]

Store them in the fridge.

 

[p1p]

Sierra batteries are NiMh, so store them fully charged, and recharge every 2-4 weeks..

 

[fdog]

My testing has shown the typical Sierra battery will lose ~60% of a full charge in 1 month. That's under room temperature storage.

..The best thing you can do for your scooter (and its batteries) is dive it often.


All the best, James

 

[Potapko]

My testing has shown the typical Sierra battery will lose ~60% of a full charge in 1 month. That's under room temperature storage.

..The best thing you can do for your scooter (and its batteries) is dive it often.


All the best, James

Thanks for the answers. What about losing capacity long term? If it is recharged once a month whether used or not, will it still lose capacity? ie. will it run a shorter distance on a full charge? We have cold long winters here. There may be 3 months where it is impossible to dive with the scooter. I am not trying to be negative but I kind of get the feeling this is an "Achilles heel" for these scooters. Or at least these battery packs.

 

[fdog]

That's a valid question.

To put things in perspective, right now we own Cudas. We have the 650 bodies (and batteries), and, the 400 bodies (and batteries).

It seems like I go through cycles, where all I dive for a month or two will be the 650, then, short little single dives for a while on the 400. So each battery gets a month or two here and there where it isn't being used, and all it gets is maintenance charges.

This hasn't impacted capacity one bit. And I'm pretty anal about tracking capacity, and often dive with a data recorder in the scooter.

So my considered opinion is that a couple months off in the winter, with appropriate maintenance charges, will be fine and not impact overall battery life.

**************

Speaking about overall battery life, I try to keep in mind that a scooter battery is a consumable item, much like tires on a car. It will eventually need to be rebuilt. These batteries seem to have a life of ~500 full discharge/charge cycles, over which they begin to display reduced capacity. If you are doing only partial discharges, then that extends the cycle count immensely.

It's worth pointing out that every battery chemistry - Lead Acid, Lithium, NiCad - has a cycle life and is a "consumable".

The two big NiMH battery killers seem to be:

• Over discharge
• Heat

It's hard to over discharge the battery when it's run in the scooter. The electronics make sure of that with the low voltage cut-offs. However, over discharge when not diving is an insidious thing, and I believe responsible for more battery issues than any other.

For example, someone uses their scooter, and they bring it home after diving and disassemble it and put it in the corner of the garage. They don't charge the battery until they intend to go diving again a month later. This means the battery, after being used down to 40% of capacity, has a month to self-discharge, and it will fall below safe voltage levels. A cell reverses it's chemistry after the voltage is low enough, and the battery fails.

What I do, is after a dive, I decide how long until my next dive with the scooter. If it's within 4-5 days (the usual), I'll charge the battery fully, to the point of the LED being solid green. That way I have a scooter at ~95% capacity when I dive again.

If, however, I won't be diving the battery for a while, I will immediately charge it to the point of the flashing green. Here the battery is at ~90% capacity, and is essentially a "partially charged" battery, with less of a hit on cycle times. Then, the day before I dive the battery, I will fully charge it to a solid green.


Kinda wordy but I hope it helps.


All the best, James