Ni-MH batteries

Manufacturers of (mostly older) strobes which lack a safety valve warn against the use of Ni-MH batteries because of the explosion risk (due to formation of hydrogen). Does the same risk exist with ordinary small dive torches or is it the strobe's high voltage that is the problem? I have put this question to a shop that only sells batteries as well as to a battery manufacturer's technical department but neither could answer. Can anybody here help? I would love to be able to use Ni-MH batteries in my dive lights.

I note, by the way that the Instruction manual for my YS-60 TTL/N strobes specifically warns against the use of batteries other than manganese, alkaline or Ni-Cd whereas Sea & Sea's 2004 catalogue states "Battery requirement 4 x AA Alkaline, Ni-Cd or Ni-MH batteries" for this strobe. Very confusing!!!

Grateful for help from somebody who knows what they're talking about.

John

Ok - I will give it a go - but to be brutal some of the spec's are open to interpretation.

Basically both NIMH and NICAD will both off gas under two sets of conditions.

1: Overcharging (NIMH is particularly intolerant of this).

2: Serious over discharge.

If you use a modern good quality charger then condition 1 should not happen.

However FWIW I would be real careful of the 15 minute chargers out there.

That does not mean that I would not use them but I would be careful in their use.

Similarly condition 2 should not be met up until you flood the thing in sea water

and then it will get messy - been there done that.

Some strobes object to the high capacity rechargables. My understanding is that this

is down to the ESR (Equivilent series resistance) of the cells.

When you take a LOT of current out of one of these cells it gets warm

( or even hot ). To minimize this heating manufacturers are trying

to minimize the ESR this also allows more current to be drawn before the cell voltage

starts to droop.

However, some strobes may well be using the ESR to limit the inrush current into

the charge circuit of the strobe. Chuck in a set of cells with a lower ESR than

the designer anticipated and much more current may flow and could lead to

internal damage.

So for my money I will use NIMH most anywhere but I will be careful of

how I charge them and probably avoid the 15 minute chargers.

Paul C

Thanks Paul! That sounds reassuring. I have a Fujicell Smart 3 hr Charger, so I shouldn't have any problems.

Yea - don't get bent out of shape over my personal suspicion of the fast chargers!

NIMH chargers control their output by monitoring the cell voltage in a number of complex ways.

Often turning on and off the current supply and monitoring the drop and recovery times of the

cell voltage.

My suspicion is that the really fast chargers may be cutting a few corners in the monitoring and that the

cells themselves need time to stabilize during the charge cycle.

I would and have used one myself but would not be too quick to seal up a load of freshly charged cells

into an air or watertight enclosure. Cells often come out of the charge phase pretty hot with

these fast chargers and I don't know what that does for the battery chemistry longer term.

A three hour smart charger sounds ideal.

Paul C

As I understand it, the charging/discharging of battery cells is very similar to corrosion cells in that both are electrochemical reactions. Gas is emitted at the cathode (typically hydrogen for corrosion cells in marine environments). With a "fast" charger, the kinetics probably increase such that more gas is produced quicker??? Again, I have no direct experience with battery technology per se but significant "exposure" to corrosion technology (particularly, marine corrosion).

It seems the larger objective (regardless of charging type and cell type) is to provide a way for gases to dissipate while avoiding an ignition source. PRC's post on this matter are practical, enlightening, interesting, and helpful. thx

Scott

www.H2O-Planet.com

Provision is made in the cell design for a limited amount of gas control within the cell itself. It is when you start overcharging or deep discharging that more gas is generated than can be dealt with internally - so they vent (or maybe go bang if you get real lucky!).

While the really fast charger may do some damage and reduce the service life of the cell that would need to be weighed against the cost of the cell and convenience of the fast charge.

In the case of say AA cells it may be an advantage to only carry one set and fast charge them on a trip rather than carrying all of the extra weight.

Given my recent experience none of mine are never going to reach end of life before salt water ingress gets them anyhow!

Paul C

Interesting thread. Somewhat along the same lines I have LED lights from two different companies. Both companies state in the literature not to use lithium batteries on their lights. I emailed one of the companies asking them if lithium batteries could be used in their LED light. Here's their response:

There are two types of Lithium Batteries:

1. Rechargeable Lithium-ion batteries (Not to be confused with Lithium battery.)

2. Lithium Batteries - are not rechargeable, they are one step above alkaline.

While Rechargeable Lithium-ion batteries can be used, Lithium batteries should not be used with it. These batteries can provide extremely high currents and can discharge very rapidly when short-circuited. Although this is useful in applications where high currents are required, a too-rapid discharge of a lithium battery can result in overheating of the battery, rupture, and even explosion. This can happen when water comes in contact with the battery compartment. Therefore, in order to eliminate the risk of such an explosion, Lithium batteries should not be used with this waterproof product.

I emailed Canon and asked them the same question about their 430EX and 580EX flashes. Their response:

" Thank you for your inquiry about using Lithium batteries in your

Speedlite 430EX. We value you as a Canon customer and appreciate the

opportunity to assist you.

You can use AA size alkaline, NiMH, and lithium batteries in your flash

and the 580EX.

We hope this information is helpful to you. Please let us know if we

can be of any further assistance with your 430EX.

Thank you for choosing Canon."

Here is a link from Sea & Sea listing serial numbers for their strobes and niMH compatibility. Good luck though, it is very confusing. I have a yellow YS120 duo with serial number 941002294 and I can't work out where it fits. The serial numbers listed for the yellow 120 seem to have an extra digit in their range, an extra zero in the middle.

http://www.seaandsea.jp/products/strobe/nimh.html

HTH

Mary

Hello,

Is anyone currently using rechargeable batteries with YS120 strobes?

If so would you please tell me what kind of batteries work well.

I have read the previous (older) posts, but have not quite found the info I'm looking for.

Thank you