Battery (EN-4) conditioning tips

Started Dec 12, 2001 | Discussions thread
Stan Disbrow Veteran Member • Posts: 3,000
Re: Battery (EN-4) conditioning tips

Thom,

No. Don't perform a refresh as the first step with a new pack. Always fully charge it as the first step. Here's why:

Pressing the refresh button on a new pack can cause cell polarity reversal in the exact same way as shooting with the camera. All the refresh button does is turn on a transistor that switches in a load resistor. There is an A/D input on the charging controller that monitors the pack voltage and switches the load off and turns on the charger output when the pack hits a predetermined voltage level.

This is exactly the same way that the camera works, except the low voltage point is lower in the charger than in the camera when the camera stops firing. The only benefit from the refresh button is that the load is steady where the load in the camera varies with whatever operation it needs to perform.

If you have new cells in a new pack that have varied capacity, then even on the refresh cycle of the charger, a cell that is significantly lower in capacity than the others will still be subjected to a reverse polarity. It will still run out of charge before the others, regardless of the nature of the load applied.

This can cause a premature failure of the cell many charge/discharge cycles later. It generally will not cause a noticable problem right away. In other words the ultimate life of the pack can easily be shortened by performing a refresh on a brand-new pack as the first step.

The only correct way to handle a brand-new pack is to fully charge it right out of the box. That will force all cells in the pack to the same capacity level. Then, it'd be fine to discharge it by use in the camera until the camera indicates the pack is exhausted. After that, use of the charger load resistor (by engaging the refresh button) would not cause a problem.

Heck, one could just charge it all the way up and then hit the refresh button to discharge it. You'll be waiting for quite a few hours for the load resistor to drop a fully charged pack, though. It's better to just use it in the camera until it runs out of charge.

Actually, if one regularly runs the pack down all the way in the camera, then the use of the refresh button would not be required at all. Nikon stuck that feature on there because photographers usually don't understand rechargeble battery pack chemistries (and why should they, it's a boring subject) and are likely to swap packs long before they really need to.

Stan

Amateur Photographer
Professional Electronics Development Engineer
(whos products are powered by rechargable battery packs)

Thom Hogan wrote:

JHsu wrote:

There is absolutely no need to "sit" your batteries on your MH-16
during all three reconditioning cycles. Just use your battery
inside the D1x (as usual). When the camera's battery indicator
changes to "half-full", battery pack's voltage is at around 7.8V,
and when the camera no longer operates, the battery pack's voltage
has dropped down to around 7.3V.

In practice, I tend to agree with you. In theory, however, you're
ignoring the fact that the D1 battery is made up of separate cells,
not a single cell. The issue is whether all the cells are at the
same voltage when you receive them. With NimH, there's the
potential for a reverse flow if you try to use the battery
immediately.

That said, it's unlikely to happen, though since we don't know how
Nikon handles building and prepping the battery. Given that we know
that a series of refresh cycles changes the ability of the battery
to hold voltage, I have to wonder if part of this is differences in
cell voltages coming from the factory. So, I still play it safe
with a new battery, though I've altered my recommendation slightly:

1. Put the battery on the charger, press the Refresh button. Wait
for a full discharge/charge cycle to complete.
2. Use the battery in the camera. When it is exhausted, put it on
the charger, press Refresh, wait for the full discharge/charge
cycle to complete.
3. Repeat step 2.

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Stan

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