MetallicaJunkie

I was preparing for tomorrow charging all my batteries, and after i was done charging battery #1 , i heard a startling pop. it is a NIMH 2000 mah battery pack i was using my triton jr set at 1 amp to fast charge. The "explosion" happened about an hour after i was done charging

Campgems

OUCH.

Was it on trickle charge?? If so, that is probably what kicked it off. NiMh keep trying to take a charge on trickle and will overcharge. You can feel them start to get really hot. I've cooked a couple by not catching them soon enough.

Don

bigtim

My Feedback: (13)

wow I have heard they can do that but this is the first time I have seen the results I charge the couple of NIMH batterys in my planes,after looking at yours I will rethink that method,my charger has a alarm when the batterys are fully charged so I unplug them when there done.

Stuntpilot51

Charging at 1 Amp is a bit excessive. I'll bet that batt was really hot before the explosion.

Charge a little slower and show your batteries some mercy.

flyinrog

My Feedback: (1)

Sorry for the loss! I hope the pilots butt didnt get burned too bad...but why "fast' charge for tomorrow?,, Nimd cant take the same as Nicd's can....Rog

JohnBuckner

My Feedback: (1)

I keep hearing these kind of stories at the field of folks cooking their batterys with their expensive chargers all the while talking about always fast charging their batterys. Good heavens give your batteries a break, C10 for 2 thousands is 200Mah

John

MetallicaJunkie

Yeah i think i'll ease up on the charging ... the reason i fast charged last night is because whenever i charge at the rate i'm supposed to on my triton jr(.1-.2), it "times out" before its fully charged..... Its the old model of the triton jr, that doesnt let you disable that feature

flyinrog

My Feedback: (1)

Dont you just have a wall wart charger, its probably still more than half capacity when you put in on so a big pack like that would take 10 hours to finish off...Rog

Missileman

What is your time limit?
Consider this:
First off you are not completely dischrging your battery to begin with so you won't need anywhere near 2000mah of replacement charge. I bet 1500mah probably would be close.
Divide that by your time limit (in hours) and see what rate you really need.
Another thing about fast charging NiMh on a peak charger is you can get a false peak and really not be near a full charge.

MetallicaJunkie

i believe it times out after an hour 1.5-2.0 hours

Gray Beard

My Feedback: (-1)

That's the very first time I have ever seen A nim blow. Most every one I know is using them and we all will fast charge at the field at some point, I do it A lot, just never seen anything like that happen except with the Li types.

JohnBuckner

My Feedback: (1)

Double post by error

JohnBuckner

My Feedback: (1)

Any charger that will not allow normal C10 charging for the capacitys you are using is a fast charger only and in my opinion should only be used infrequently. Fast charging agine in my opinion all three of the battery technologies we normally use causes heat (sometimes to the extreme) will result at best in shortening service life. At worst it can and will cause well what happened to you.

If money is an issue tower sells 200 Mah wallworts that would work well with your 2000Mah batteries. Or there are hundreds of remarkable chargers avaliable now for cheap that are fully peak detecting and fully selectable for the normal capacity batteries we use.

The photos are my three little lovelys that are fully capable for all battery types and capacitys and even charge your lead acid (PB) flite box batterys.

The yellow ones are Prodigy Pro Peaks and magnificent units, been using them for about two years now and the other is a Mystery from Hobby City in Hong Kong for fifty bucks and it even more capable in a tiny package and came with the nice metal case and a selection of leads.

For normal flying days there is no reason to fast charge just start the evning before and heck you can even up it say another 100 mills if you like but this fast stuff makes me cringe when I see them doing that and they are always the ones that come to me and want to know whats wrong with there batteries!

Nothing but just my opinion

John

j.duncker

My Feedback: (2)

I have seen several NiMH packs blow. The lecky boys like to get them hot just before launch to get max power. When they exceed the critical temp they do go bang!

I stay with 1/4 C as my max charge rate on NiMH cells.

MetallicaJunkie

mods could u please delete this thread? I now know why my battery "exploded", i posted this because i was in shock, i had never experienced this my whole life

Missileman

Why delete the thread this is good info for others.
What did you find out?

MetallicaJunkie

i found out that charging at 1 amp(1000mah) all the time is bad for my 2000 mah nimh packs. That explains why ive killed two nice battery packs, one by explosion, and the other just lost a cell.

Stuntpilot51

Metallica,
This is great info for most newbies, don't feel bad sometimes you have to learn the hard way.

IMHO fast charging is just a bad thing, I use the Accu-cycle and charge my 2000's at .125 for the cycle time of 15 hours., this is only after I discharge. Also it was mentioned that most of the time you will never use more than 1/3 of your large pack, keep this in mind when charging, in that case I put it on .050 setting and let it go overnight, similar to a wall wart. 12 hours on a WW is the same as 600 Mah or 12 times the output rating on your charger.

Think about your 1 amp rate for 2 hours, 2000 Mah for a pack that only needed 500.[X(][X(] hence the explosion.