a stupid question but any 4300mah battery (12v, 16.8v, 7.2v) should recharge to approx. 4300mah if discharged to 0.8v per cell?
my 7.2v 4300mah cell wont charge above 2500mah?! also, what should the full charged voltage be of a 7.2v nimh pack be?
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a stupid question but any 4300mah battery (12v, 16.8v, 7.2v) should recharge to approx. 4300mah if discharged to 0.8v per cell?
my 7.2v 4300mah cell wont charge above 2500mah?! also, what should the full charged voltage be of a 7.2v nimh pack be?
If you've got a fancy charger you could try to cycle charge it and see how that goes?
tried. got a constellation charger
I'm not sure exactly how that charger works, but on mine you have to set voltage, charge current, capacity etc but I assume you have done all that correctly. My charger also has a cut off timer that can cut in before the battery is fully charger, is it possible that that is the issue?
How was the battery pack made? If the cells were overheated when being soldered together, the capacity will have dropped off. Found this one out the hard way with a home made pack of A123s
have had problems like this in the past, after cycling quite a few times if your still getting low amp readings then i would suggest cycling each cell individually as the constallation charger will charge 1 cell, you may find some cells are poor and letting the pack down. or you might find they are all just as bad as each other :cry:
time for another pack then :!:
its really weird. it charged last night to 4250mah which is basically fully charged. then i discharged it. got in today and tried again and it did the same trick?! once its fully charged, its being wired up to the rest of them for the 24v pack!
Check your charger is set to the right capacity or automatic charge.
capacity is fine. must admit, i havent tried the auto charge yet and i kinda remember being quite good for conditioning new batteries?
The nimh auto mode seems to have done the trick! bit weird how the proper setting wont work?!
right, ive now got the whole battery made up so its a 24v 20-cell Nimh pack. However, the constellation's discharge limit is 3 amps but when ive tried to discharge the newly-wired pack for the first time as a 24v pack, its jumping to 5.06 amps and the heat sink is actually getting colder due to the fan kicking in?! any help?! its currently discharging on the Nimh auto mode
ive separated the packs again but now they wont discharge at all?!
I'm in the pub, too drunk to help now !
I'm on a123 now and going good !
lol. put it this way, if i cant get the batteries to work, ill probably be selling the lot.
The 7.2v pack is no longer charging or discharging (won't move from 8.1v?!) and the 16.8v pack is discharging very very slowly. I guess this means the 7.2v pack is dead and the 16.8v is damaged?
or your charger is nackered. Got another charger to hand or a friend with one nearby?
Nope. Any other ways of checking?
As a last resort you could send them to someone to check them over for you?
Well I'm guessing if a charger rated up to 3 amps jumped upto 5 amps when discharging, it's probably broken the charger! Can't understand why it would do it though. However, getting some to check the batteries would be cool.
No in that case it does sound like your charger is nackered. The batteries would happily flow 30A plus through the charger if they were allowed to.
If your stuck, post em to me and I will cycle them 4 u.
Another weird thing, the 7.2v isnt discharging at all (well 0.02amps) but the 16.8v is discharging at 1.05 amps but the voltage isn't really dropping?
Thanks Terry. I'm thinking of getting a new constellation unless anyone has any suggestions?
ive ordered a new constellation (should arrive tomorrow) and i want to run through the procedure one more time so please feel free to call me stupid if any of this is wrong.
1. to start with i have a 16.8v 4300 nimh pack and a 7.2v 4300 nimh pack. both made up from the same type of cells from the same company.
2. i will be discharging both to 0.8v per cell on the corresponding set-ups (max discharge 3A)
3. I will then charge both up to full capacity (one after the other as i only have one charger, max charge rate 3 amps)
4. I'll then join them up as required to make a 24v 4300 nimh pack
5. This will then be discharged on the NIMH automatic setting
6. The next time its charged will be on the auto setting again (probably will end up cycling a couple of times)
Any help?
Can you not charge it as one pack? I'm not familiar with that charger so cant help on the technical aspect of it, but i'm confused as to why you're doing that.
Before joining them up, I've been informed on the forums that both packs must be fully charged?
Ahh you're going to physically join them up?
I meant charge them in series and just leave them as they are in the robot. Hopefully that takes away a potential problem of having to remake the packs, might also let you cram them into the robot a bit better if space is a bit tight.
oh! they are to be wired in series and installed into the robot, where they will stay unless theres a reason to remove them. Its just i have to charge them before i connect them in series (i think?!)
Ahh ok. I just soldered 2 deans connectors in series and connect that to my charger and charge them through that. Thats 2 9.6v 3300mAh batteries so I tell the charger it is one 19.2v 3300mAh battery and that has always worked for me.
thats what ive done in the past and what i did when i made the 24v pack. for some reason the charger took exception to it!
If 1 pack is flat and 1 pack is charged then connected in series and charged together in series the charged pack will get very hot and could get damaged.
All you need to do is discharge them 1st so they ate all roughly the same voltage. My nimh packs were 25 cell 30v.
So what your saying is it doesnt matter if they are fully charged or empty, As long as they are the same?
They should be empty.
viewtopic.php?f=111&t=4006
im confused???
Yes its better if they are empty, but at events there is no time to discharge before charging again, a constellation charger will cut of anyway .
When there is time to discharge its good as it helps to balance the cells again.
New charger's working great. Am I right in thinking that the higher the battery voltage, the lower the discharge current? ( the 7.2v pack discharged around 2.7a and the 16.8v pack is going at 1.2a)
yes thats correct the higher the voltage the lower the amps will be.
I think its 300w charge and 120w discharge, my 30v cells used to take
about 7 hrs to discharge !
the 16.8v is pushing 2 and half hours now. how long du reakon to charge upto 24v 4300mah @ 3amps?
Sorry should have been full :PQuote:
Originally Posted by kane
If you discharge both packs fully first then the pack with the lower capacity will end up getting overcharged to some extent. If they are both fully charged then they should discharge to the same level.
what should a 24v battery charge to?