Rechargable NiMH Batteries - hold charge

[WesternGuy]

I got a new Canon 580EX for Christmas and this plunged me into the world of rechargable NiMH batteries. I have two sets of four of these for the flash and would like to know how long they hold their charge outside of the flash unit. Both sets are 2500 mAH and today, both are fully charged. One set is in the flash unit and the other set is a spare. So how long will the spare hold its charge while the other set is being used to run the flash? Also, is it okay to leave them in the charger (unplugged) after they have been charged?

Any insight, experience that anyone would care to share is greatly appreciated. :thumbsup:

Cheers,

WesternGuy

[Franglais]

I got a new Canon 580EX for Christmas and this plunged me into the world of rechargable NiMH batteries. I have two sets of four of these for the flash and would like to know how long they hold their charge outside of the flash unit. Both sets are 2500 mAH and today, both are fully charged. One set is in the flash unit and the other set is a spare. So how long will the spare hold its charge while the other set is being used to run the flash? Also, is it okay to leave them in the charger (unplugged) after they have been charged?

Any insight, experience that anyone would care to share is greatly appreciated. :thumbsup:

Cheers,

WesternGuy

I did the same sort of thing when I bought my SB800. Left the NiMh's in the flash for a few weeks, went out for a shoot and had to change batteries in the middle. I don't have any accurate figures but it feels like they lose at least 10% of their charge each week.

My strategy right now is to just take one set of batteries and charge them up just before going out. If it's really important or if there are a large number of photos to do then I bring along a second set of batteries, also fully charged

Charles

[another view]

The 10% loss per week sounds about right, possibly even more in my experience. The two big downfalls of Nimh batteries are this and cold weather...

[SmartWombat]

I'm trying some new Uniroiss hybrio batteries, charge as NiMH but have better retention.

[payn817]

Have you tried energizer e2 lithium? I use them in my flash, and get good recycle speed, and a couple 100 flashes before they start getting too slow or weak.

If you want to stick to rechargeables, you could get one of the chargers with car adapter, and charge on the go. Also, for like $30 there is a 15 minute charger available.

[another view]

E2's are great for cold weather, but they're expensive at about $10/set of 4. I used 2100mah rechargeables and didn't have to worry about changing batteries - this was when I shot a few weddings and events. I'd drain and charge all my batteries the day before so they were ready to go, but not so early that I'd start to lose the charge. When you're shooting a lot (like that or maybe a vacation) it works great, but for a few shots here and there it does become a hassle.

[freygr]

The charge retention depends on the storage temperature, the hotter it is, the faster the discharge rate is. Unluckily I don't remember the web site with the tables but it does exist on the web someplace ;-)

By the way, the self discharge happens with all batteries, but the discharge rates change with the battery chemistry.

[WesternGuy]

Thanks to all for their insight and information -- greatly appreciated.

WesternGuy

[GB1]

I used to use rechargable NiMH batteries, but the recharge issue became a little too much hassle. I think they lost 15-20% a week or so. I do plan on using them again however.

Here's the way to go with that: charge them and whatever extra set you are planning on using on a shoot, but keep a spare set of regular lith batteries as a backup. Even if you have to use the liths, it might only be for a few shots and they'll be close to new. Just keep them as backups for awhile. They should last years if you do it right.

[payn817]

Good advice. I have used the same set of e2 since around the first of december. I do not use flash often though. Something to consider is how often you use flash, and is it for paid work. If it's a job, add it to the invoice.

I too am looking into getting the recharge setup, but a this time it doesn't make since for me. I think your needs really dictate what you should use.

light use - lithiums
frequent - GB1 is spot on
heavy - battery packs?

[freygr]

I used to use rechargable NiMH batteries, but the recharge issue became a little too much hassle. I think they lost 15-20% a week or so. I do plan on using them again however.

Here's the way to go with that: charge them and whatever extra set you are planning on using on a shoot, but keep a spare set of regular lith batteries as a backup. Even if you have to use the liths, it might only be for a few shots and they'll be close to new. Just keep them as backups for awhile. They should last years if you do it right.

That is strange, I had my NiMH batteries lasted for a month in use in the C-3030. But now they are not holding the charge, in a month there dead but there are old (new in 2000) but that is to be expected. With NiMH batteries unlike NiCAD don't develop a memory so you can charge them after use without that memory problem. With NiCAD you have to run them dead before recharging. You do need to use a NiMH charger with NiMH batteries not an old NiCAd charger. Also the higher the MA hour in a battery size the faster it will self discharge (plates closer together)

[GB1]

That is strange, I had my NiMH batteries lasted for a month in use in the C-3030. But now they are not holding the charge, in a month there dead but there are old (new in 2000) but that is to be expected. With NiMH batteries unlike NiCAD don't develop a memory so you can charge them after use without that memory problem. With NiCAD you have to run them dead before recharging. You do need to use a NiMH charger with NiMH batteries not an old NiCAd charger. Also the higher the MA hour in a battery size the faster it will self discharge (plates closer together)

Same here. I think the marketing guys pumped them up a little too much.

They're definitely better than NiCAD batteries (which sucked) but they don't seem to hold the charge as well as they used to. It might not be the same as NiCAD memory but a different kind of degragation. I just bought an expensive wind-up flashlight/lamp for camping with an internal NiMH.. I hope the same doesn't happen with it.

GB

[danno]

NiMH batteries have been known to loose almost 20% of their charge even just a day after charging them. Temperature has a lot to do with that (just repeating what was already said). Lithium AA batteries have a shelf life of about 1 1/2 to 2 years... they're a little more expensive, but great to keep around just in case.

[WesternGuy]

Thanks for the insite danno.

WesternGuy