Battery Charging

[Judderman 0]

Adoo all,

thought it bout time i charged me battery ready to set the toe in-out, alignment of the wheels and such, the battery at the mo is flat so i cant run it and see what it does.

The battery i have is a powertech RC3000 nickel metal hydride battery pack i assume its a 7.2V as most of them seem to be, standard size ( sorry i dont know a lot about them )

it says on the battery itself : " standard charge 10 hours @ 300ma - Fast charge 1 hour @ 3000ma

the charger i have is a vector nx81 with switchable outputs that are in steps of : 0.5A, 1.0A, 2.0A, 3.5A, 5.0A

which one do i use dudes ? this is the first charge the battery is gonna recieve so i imagine its gonna be a slow one but which one ? then which one for regular charging ? is there a formula of some sort to work out which charge to use.... i aint gotta clue & stuck with a flat battery frightened of charging it in case i cook it lol

many thanks

[Zak001 0]

Rule of thumb is 1000mah 1A

2000mah 2A

3000mah 3A

Ect.....

Alot of my friends just charge at 1A to be on the safe side and it extends the life of the battery, Im sure 2A would be ok though, some charge even higher, people have different views on charging but you cant go wrong with 1A, it will take longer but thats what I charge mine at.

[94eg! 834]

If your nimh has been sitting too long, the voltage of the cells could have dropped to zero. This can/will kill individual cells or even the whole pack. You can try to charge it at a very low rate (the lowest your charger goes), to nurse it back to life, but chances are it's done for. If you have a volt meter and a discharger, you would be able to see your individual cells won't hold voltage under load any more. Even if their resting voltage is 1.25, the voltage will instantly drop down to 0.8v once a load is put on them. This is what makes your car run so sluggish with a stale pack.

Now would be a good time to invest in Lipo equipment (charger, battery & low-voltage cutoff)...

[igbandy 34]

Set the charge rate at 2.0A, it should take about 1.5 hours. You could charge it at 3.5A and it would take about 45 minutes but the battery wont last quite as long.

[Taman 3]

Rule of thumb is 1000mah 1A

2000mah 2A

3000mah 3A

Ect.....

Alot of my friends just charge at 1A to be on the safe side and it extends the life of the battery, Im sure 2A would be ok though, some charge even higher, people have different views on charging but you cant go wrong with 1A, it will take longer but thats what I charge mine at.

Does this apply for Nicad batterys as well eg: 2400mah = 2.4A?

cheers

[Zak001 0]

Does this apply for Nicad batterys as well eg: 2400mah = 2.4A?

cheers

Now thats something Im not sure about having never used them

[PaPeRo 30]

Does this apply for Nicad batterys as well eg: 2400mah = 2.4A?

cheers

No, most NiCD stick packs could be charged at 5A or more. In fact with NiCD you will want to charge at 5A or more so that the pack will have more punch.

[94eg! 834]

No, most NiCD stick packs could be charged at 5A or more.

Most Nimh should charge at 4 to 5amps as well. I don't know where the 1C rule came from with Nimh as it was originally meant for Lipo. I have been charging my nimh at 4+ amps since the days of 3000mah cells and never had trouble. I had NEVER heard this 1C/Nimh rule until long after Lipo came on the scene. Long after people started having trouble with exploding Intellect 4200 cells.

[stu22 12]

Most Nimh should charge at 4 to 5amps as well. I don't know where the 1C rule came from with Nimh as it was originally meant for Lipo. I have been charging my nimh at 4+ amps since the days of 3000mah cells and never had trouble. I had NEVER heard this 1C/Nimh rule until long after Lipo came on the scene. Long after people started having trouble with exploding Intellect 4200 cells.

People are told to charge at 1C because it's safe. The problem that comes up is the different cells in a pack will discharge at different rates when running. Add to this, the different cells will self discharge at different rates. When you charge a pack there is a very good chance that the individual cells will reach capacity at different times. If you charge at a higher rate and one cell hits capacity before the others you stand a chance of overheating and venting that cell.

This actually became an issue when the first high performance/discharge IP4200 cells came out. People would put storage charges on them and let them sit for a while. When they went back and charged them at 6A (like the little sticker on the side of the cell tells you to) they would find one of the cells had discharged less than the others and it would overheat and vent. The solution was to start using a discharge tray and bring all the cells down to 0.9v before charging.

As a rule when charging NiMH I charge stick packs at 1C and anything that I can run through a discharge tray (I don't have anything under 3300) at 5A.

BTW, a NiMH pack is perfectly fine if it self discharges down to 0v. You only run into problems with reversing the polarity of the cell if a cell in a pack is fully discharged and you start running current from the other cells through it. If a pack has not been used for a while you almost have to trickle charge it since the thing will false peak on you.

[94eg! 834]

A higher performance modern cell will be irreparably damaged if the resting voltage drops below 0.9v. They may still work, but capacity, internal resistance and average voltage will be adversely effected. I had 2 matched IB4600 packs die and they never got low enough to reverse voltage. They simply dropped to zero and never came back up. BTW: These cells would make random hiss noises since they were new, even when charging at 4.5ams (lower than 1C). Is it any wonder the industry has moved on to Lipo.

BTW: The main reason cells were exploding was because the vent size of the IB4200 was inadequate and people would also smother them in solder plugging them up (and charge at 8+ amps). In a stick pack, the tabs are welded to the cells so no worries about solder blocking the vents.

[Judderman 0]

ive set it to charge for 1.0A bout an hour and a half later its on charged/trickle setting and the battery dont feel hot or theres no warning lights on the charger telling me ive done wrong so i think im on a winner there. Thanks for that all, saved me cooking my battery and the rule of thumb zak001 is alright by me an hour and a half aint a too longer wait & its safe at that level. job done !

[Taman 3]

Good to hear you got yours sorted (aplogies if I hijacked your thread)

With the Ni-Cad do you discharge them every now and again to keep the working correctly? My charger has a dicharge/charge cycle on it? Also what rate is safe to discharge at?

thanks

[PaPeRo 30]

You should completely discharge after every run, either through your discharger or simply run the car until it stops moving. After discharging you should let the battery cool down before you recharge it again. You could discharge at any rate. At lower rates you get a more complete discharge but you have to wait longer, but it makes very little difference.

[tundragumski 1]

I thought that NIMH batteries over 2000mah should always be fast charged using a delta peak charger at 3A plus. A shop told me that slow charging un-balances the cells and wrecks the battery.

Is this true? I use a quick charger that has a fixed charge current of 3.5A and it seems fine - batteires get a bit hot but never had a seroius problem.

[94eg! 834]

I thought that NIMH batteries over 2000mah should always be fast charged using a delta peak charger at 3A plus. A shop told me that slow charging un-balances the cells and wrecks the battery.

Is this true? I use a quick charger that has a fixed charge current of 3.5A and it seems fine - batteires get a bit hot but never had a seroius problem.

That is correct. Nimh should be charged with a peak detection charger. Nimh is much more senstive to overcharging than Nicad. This is the reason they get so hot. A timed charger is a recepie for distaster with Nimh.

You can still charge at a very low rate with nimh, but it still should have active peak detection. No trickle charging.