Eneloop pro battery 2500 overcharged to 3600mah. Help please!

Hello, this is my first post. Sorry if this is not the place to write. I hope you can help me.

I am wedding photographer and this weekend I have two hard wedding in terms of flash use. More than 6 hours of party both days.

I have bought 20 new eneloop pro bateries in amazon and a new powerex 9000pro charger to charge my new batteries.

I am refreshing all my bateries. I also have 2500 mah amazon bateries. So I have used refresh and analize mode. Charge at 1200 and discharge 600 as the manual says.

Yesterday I was refreshing 4 of amazon 2500 mah bateries and 3 of the stop charging at around 2550 mah… but one was 2890 and keep charging. I thought that was because maybe the battery was no good. So today I put to refresh the new 4 enelopp pro… I saw that the discharge was good, all of them around 2500-2600, but after 2-3 hours I went to see and 1 battery was DONE with 2580, 2 of them still charging with 2550mah, but the last battery had 3600 mah I have just taken all for bateries out from the charger… Now… I dont know what to do. Second time something weird happens. Is this battery going to brake my flash? I put a fan near the powerex charger to avoid heating…can this be a problem? Why is this happening? Now I am afraid of charging during night… Can this battery could continue charging until explotion? Please help me.

always better to charge when you are awake, so you can monitor the progress and prevent overheating…

I dont have your charger, but I did some google reading

Here is the manual

it says:
“Charging too slow may prevent the charger from terminating correctly.”

so, I suggest you read the maual, and follow the instructions to set the capacity and charge rate

I cannot explain why the charger is producing different results with different batteries… but I would stop the charging when the correct amount of time has passed…

definite No to leaving the charger running while you are sleeping

I hope you figure out how best to use the charger

Well you’ve got 20 batteries, that’s 5 X 4. When you charge another set of batteries, does the same thing happen? And if so, does it happen at the same slot?
When I charge batteries I ALWAYS clean both sides of the charger, and both ends of the batteries (nothing fancy, just dry cloth).
But I NEVER leave them unattended. You don’t have to hover over them, being in the same room is enough.

It’s nice to see you, fran_spain!

I’d have thought that charger is pretty good so I’m surprised it’s missed a termination.

1.2A is plenty charge current for it to detect “full”.

The cell won’t ruin your camera, voltage (which can cause damage) and capacity (which is energy like size of fuel tank) are different things.

1 Thank

Looks like it missed the cutoff, but something else to think about, NiMH charging isn’t 100% efficient. I think it’s something like 70-80%. So to get 2500mah into the battery the charger has to read >2500mah.

Even though the charger says it tried to put 3600ma into the battery, it actually did not stay in the battery…

the excess charge just left the battery as heat
similar to trying to overfil a gas tank, the excess that does not fit, just overflows onto the ground

Is this battery going to brake my flash?

the attempted overfill wont hurt the camera flash…

just turn the charger off when the correct fill capacity has been reached, or when the other batteries have stopped charging…

1 Thank

Capacity is for discharge only.

Put a 5gal bucket on the floor 10ft away from you. Sling pints of water at the bucket, trying to get it in. A good portion will miss the bucket entirely and end up on the floor.

You might end up tossing 15gal of water before the bucket’s full.

But on pouring it out, you’ll still only get 5gal.

Inefficiencies in the chemical processes involved, heat, etc., will “waste” energy input on charging, and sometimes lots of it.

I wouldn’t be too worried about it. Nimh charging is a little different.
As others said, it isn’t close to 100% efficient like lithium charging.
Nimh batteries are done charging when they start heating up and a little heat is normal.
I haven’t tested my eneloops on anything other than the included panasonic charger, but maybe I should try using my xtar.
You could charge a 2500mah nimh battery at 1 amp all day long, putting well over 24,000 mah in it, and you’ll still only get 2500mah out of it (if it doesn’t degrade from the heat of overcharging lol).

Yes overcharging a Nimh battery is “bad”, but not as bad as you think, and depends on how long it was overcharging. If you over charge them every time they are charged, then I would expect accelerated degradation. But “1 time”, nah you’re good.

Nimh batteries also won’t catch on fire either like lithium batteries.

Heat is the ultimate killer of batteries in the end, so any way to prevent that would be best.

The C9000 is more of an analyzer than a charger. Although it can charge batteries, its not the best tool for the job.

This isn’t actually true. It does both quite well. There is a review on CPF that says something similar in his conclusion,
“The charger is very good for analyzing batteries, but for normal charging the batteries might not always be filled”

but mentions previously in the text that if left in the charger for the recommended top off period, “it just fills the batteries”.
A, what I consider to be a better review, by SilverFox, he said it was in the top 5 chargers for filling cells.

In ay case, I have 3 of them that I use regularly, both for analyzing and charging cells. They do an excellent job. of charging and taking care of cells. I have 10 year old Eneloops that are still going strong and have only been charged in the C9000. I never have had them not terminate properly!

Now… mine are the older models. I haven’t seen good comprehensive reviews of the new PRO model.

Hello again, sorry I could not answer, I had to weddings this weekend and had no time. I am reading every comment and answering everything.


hello!! Yes…it is definitely a good idea to charge during the day… I read the manual from the first letter till the last one the first thing after receiving the charger… I set the charge to 1200mA but this is not working in some batteries… But it is a good idea what you said… and I did that, I discharged at 600mA, then when it is supposed to be uncharged, I charged at 1200 mA and after 2 hours aprox (as 0,5C should charge un two hours) I had a look and just took them out of the charger.

I charged on saturday other 4 batteries that I used the day before in other wedding on saturday and just charged at 800 mA and it work… I dont know if they were 100% charged…but they worked good in my flash.

I will update any news…

Hello henk4u2! I charged the next day 4 amazon batteries…and it was the same or worse… And then when I put them into the flash I had an “Low Power” error… So something is wrong also with this batteries…or the heat has ruined them…

I have to make more tests to see if the problem is always at the same slot, or maybe at some level or charge…I charged 4 eneloop pro on saturday ( I used them on friday) and just charged them at 800 mA, and they didnt get so hot… and the charged stoped at some point. I dont know if they were 100% charged, but…they were not as hot, they stopped with “DONE”, and the did their job in the flash…

I have start cleaning batteries as you say with a piece of cotton cloth. So thanks for the advice. And yes…I will charge them just during the day… I dont want again to smell like to hot things in the charger.

Thank you!! You have very nice eyes haha :wink:

Keep in mind that charging a cell has inefficiencies. IOW, the battery will never actually get charged the same amount as your charger shows going in. This is why capacity is normally checked on the discharge cycle. Not a big deal, especially if the cells are doing what you need then to do. But something to keep in mind. AN OK fudge factor would be to add ~15% to the calculated charging time if you have the goal of getting some specific amount of capacity. That is, when using the formula that you state in your post.

1 Thank

Hello gravelmonkey… Yes…and also as being the new one, the PRO, I thought it would have been good. what is 1.2A? What do you mean but 1.2A is plenty charge? 1000mah is 1A isnt it?

Thanks for the advice… I thought a battery/cell could damage my flash. Eneloop has 1,2V of voltage is this correct? but when charging it says 1,4/ 1,45/ … depending. I suppose that you mean that if I use correct voltage batteries, my flash cant have problems.

Hello! yes…it has happend more than once… I though this eneloop pro batteries where good batteries… I get the point that it has to read more than 2500mah, but the problem was they were so hot also… the smell was like when you put an old electric heating… or when a TV or laptop gets to hot that the inside has a smell. So I have to do more test. Actually I had a wedding on friday, and on saturday I charged again for other weddding but this time at 800mA, and I think it was less hot… and it stopped charging at some point.

hi again jonslider!

Ok, so when the battery or cell ( I dont know the correct way to say it in english) gets hot losses “charge” but the charger counts this?

I did that, however… To do that I have to uncharge first, then from “0 mah” I know that at 2500 more or less I can take them of from the charger. at 1200mA (0,5C) 2 hours… at 800ma (0,3C) 3 hours?

Hi lightbriger! THis is very explanatory.
So you only know real capacity when you discharge…

I love the 5gal bucket explanation… Reading all this I learnt (more or less) how a charger works…

So when it says 3600mah…it means that I have thrown 3,6 gal of water to a bucket, and it might be 2,5 galons (2500mah) But it is impossible to know as I could have loosen more energy because of heat and other things.

If I put a fan cooling them? is it good? Or could I interfere with the charge? I dont know if I read that the charger detects heat to stop charging or this make no sense?

Thanks again for your explanation. Very easy for a persona like me uneducated in these matters.