Let us wake everyone up

So we know that lipos are to charged at 1C (which means you charge a 2200mah lipo at 2.2Amps max).  The known exception is the new Hyperion lipos, which can be charged at up to 5C (users have not posted any long term side effects of the same, if any).

The question is, how fast can we charge the other types of batteries like regular NiCDs and NiMHs that we routinely use in RC.  NiCD charging instructions typically say charge at 15mA overnight or something like that.  If one's charger allows it, can we charge it at say, 1A ?  (This is handy if you forgot to charge overnight, and you have only 1 hour before you head out to the field for flying!).

So what is the safe method for fast charging these (if any) ?

NiCds will tolerate some abuse but the down side is that slowly would loose thier life. The best charge rate is 1/10 C for NiCd and NiMh.
Having said that you can fast charge them upto 1.5 C which means you get a charged battery in an 1 hour. The thumb rule in slow charging being that you need to inpuit 1.5 times the Mah capacity of the pack/cell

The biggest ememy for NiMh is heat, if you cooked up your NiMh cells say good bye to them sooner or later. 

Great ! Now let us take this a bit further (along with summarizing/clarifying what was said).

So it is OK to fast charge a NiCD around 1C once in a while ?

For NiMHs, did you mean the heat due to fast charging, or due to (say) keeping them in the sun ?

Sun will also heat up and you have a solution for that by keeping them in shade. But what is more important is the internal heat build up due to fast charge.

Yes once in a while it is ok to fast charge your NiCd

Also, what about fast charging NiMHs ?

What are delta peak chargers, and is it important to use them for these type of batteries ?

 i have MAHA battery analyzer/charger for nimh/ni cd batteries,from my experiece i can say the better way to charge nimh/ nicd is 1/10 th of the battery capacity. my charger can charge the batterey in one hour, conditioning of the battery  can take upto 48 hours, not much difference in performance after putting the battery in the conditioning mode.... heating up the battery is the main problem, always go for standard charging.


santhosh

more info abt maha chargers
   
www.mahaenergy.com

santhosh

QuoteSo it is OK to fast charge a NiCD around 1C once in a while ?

This would be acceptable if the battery was - at least - close to being fully discharged. Charging an almost fully charged battery would certainly cause it to overcharge and therefore overheat.

Fast charges for NiCd or NiMh at 1 or 1.5C should only be used if the charger has some sort of detection (e.g. peak). Or the battery should be discharged before starting.

Sanyo fast charge Nicd can be easily charged at 2c and higher and so can some high discharge Nimh like the Intellect Battery 3600 .

this is my story and I am sticking to it.

Shortening of battery life is largely irrelevant to rc'ers who will sooner get bored of the same
old pack and dump it for the latest brand of XYZ super batteries.

Quote from: saikat on September 04, 2009, 05:16:16 PM

this is my story and I am sticking to it.

Wow    Sahil is in a bad mood today    

Updated: I meant to say Saikat !

How many packs have we seen made of Sanyo fast charge cells, and BTW I still fly with my old packs which are well taken care off.

And then when you are putting in facts it applies to majority of the case there would always be exceptions to the rule. 

For eg the rule with most LiPo is to charge them at max 1C but then you also have latest packs which can be charged at 5C. Then again a slow charge never harms but fast charge has the potential to do so

BTW  This is my story and I am sticking to it through thick and thin 

QuoteSahil is in a bad mood today

is saikat's name also sahil  

how many of you guys still use Nicds or Nimhs ?? i have been charging my lipos at 1.5c n problems still get the same run time and i have personally observed that a slow charged Nicd/Nimh will have more rum time then a pack charged at .7c or higher rate.

sahil

Quote from: sahilkit on September 04, 2009, 06:52:49 PM

QuoteSahil is in a bad mood today

is saikat's name also sahil 

No I am Saikat - although you can call me "James Bond" if you wish ...


Re: Flyingboxcar's post ...... I am unable to think of an effective rejoinder at the moment
so I concur ..... for now......

QuoteSanyo fast charge Nicd can be easily charged at 2c and higher and so can some high discharge Nimh like the Intellect Battery 3600 .

As flyingboxcar says, exceptions are just that. Both of us are referring to common usage. For example, Sanyo ENELOOP NiMh cells have a very low self discharge rate - 15% over 6 months as compared to typically 5% 1st day + 1%/day after that for what most of us use. Would you say that NiMh have a low self discharge rate, therefore?

QuoteShortening of battery life is largely irrelevant to rc'ers

Can we take a poll on this one?

I will be getting a 3000Mah battery with my e revo 1/16.Any idea on how I should charge it?IT says that it will take approximately 6 hours to charge it.ANd I don't think that the stock charger is adjustable.How can I do six hours of watching over the battery when I go to school at 9 and come back at 4???

Set an alarm and ask your parents to switch it off when you are away. Note that some charges discharge the cells if cells are not removed from them.

Another way is to buy a simple accucel 6 which is accessible from HC for 1500 bucks including shipping and discounts. Or buy one locally if your customs office is strict / you dont have access to paypal or CC.

These charges help you set up the charging current and help you charge in less than 2 hrs safely. Though cells charge cycles reduce if you charge fast. But since cells are cheaper these days, you dont have to worry abt charge cycles.

hi everyone.
Any nicad or nimh battery has a standard charge rate of 1/10 of the capacity, so if u have a pack which is 2,000 mah, u can charge it at 200mah for 10 to 12 hours, this is standard, If any pack does not have "FAST CHARGE"  stamped on it, u cannot exceed that standard charge rate mentioned above, u r damaging u pack, and one day u will loose ur plane. Now, in the recent past, nimh and nicad fast charge have entered the marked, and they will have fast charge positivey printed on it, cause if u fast charge a standard battery, and it catches fire and burns ur house down, u cannot take the manufacturer to court. that is the legal implication. for the rc guys, if fast charge not printed, follow standard charge settings.
happy charging
Ramesh Tahlan

But dosent High Discharge nicd generally means they can be fast charged? I have never come across any nicds/nimh that mentions fast charge printed on the battery(probably I havent bothered to find one), But I have fast charged them(1/3 C charge basically) w/o problems and used them till I got hold of LSD Nimhs.

May be I Am wrong. Lets see what others who have used NICDs have to comment on this...

The problem Iam aware of is that one should not Over Charge Nicd or especially NIMH. which will hamper the life severely.

Vinay,
nimh and nicad batteries that can be fast charged have it written on it specifically, to keep the user safe from explosin and fire. So take care and be safe. i have nimh pack Hydramax ultra, 4200, high discharge, and specifically written STANDARD CHARGE 11 HOURS ST 420 MAH. So high discharge does not automatically mean high charge, now look at DuraTrax 9.6V 5000mAh, it has specifically printed on it that u can charge it at 4,000 mah. So please be careful. if fast charge figure no written, the default it 1/10 of the capacity at is universally understood, not required to be written.
Ramesh Tahlan

Quote from: iamahuman on July 15, 2010, 06:11:36 AM
I will be getting a 3000Mah battery with my e revo 1/16.Any idea on how I should charge it?IT says that it will take approximately 6 hours to charge it.ANd I don't think that the stock charger is adjustable.How can I do six hours of watching over the battery when I go to school at 9 and come back at 4???

Unfortunately this discussion is not for your charger, If you are using the Traxxas included charger. You cannot select the charge rate. Best to get a basic charger like a Hobbycity or something

I always use 1C current rate.

I follow the recommendations on the battery.  Many/most NiMH and NiCD cells specify the rate and time, and it is usually in the 1/10C range as Ramesh sir mentioned.

Fast charging is OK every once in a while, but following the recommendations would keep the battery in top shape for much longer.

Quote from: rameshtahlan on July 15, 2010, 10:01:02 AM
hi everyone.
Any nicad or nimh battery has a standard charge rate of 1/10 of the capacity, so if u have a pack which is 2,000 mah, u can charge it at 200mah for 10 to 12 hours, this is standard, If any pack does not have "FAST CHARGE"  stamped on it, u cannot exceed that standard charge rate mentioned above, u r damaging u pack, and one day u will loose ur plane. Now, in the recent past, nimh and nicad fast charge have entered the marked, and they will have fast charge positivey printed on it, cause if u fast charge a standard battery, and it catches fire and burns ur house down, u cannot take the manufacturer to court. that is the legal implication. for the rc guys, if fast charge not printed, follow standard charge settings.
happy charging
Ramesh Tahlan

Sorry, but NiMh or NiCds do not - normally -catch fire if charged at an excessive rate for too long. They have vents which will release the internal pressure when the cells become very hot due to the high rate. This will at least reduce battery capacity/life, but thats about it.

The 0.1 C rates is a "safe" figure that will not cause problems even if left to charge indefinitely. Maximim rates vary significantly with different manufacturers. Also, I have found that the SANYO "Eneloop" cells do not take kindly to even a 1C rate. Their "normal" ones ar OK.

I had a pack that i forgot to remove from slow charge and it melted its shrink tube around it and there were black deposits around that place

Then you had something wrong with the charger or battery.

Would you give details of the charger and battery? (Current rating of both).

It was a chinese battery 6v 700mAh and the charger came with it (It was from a nitro buggy)