Quote from: saurabhhsrivastavaa on March 03, 2010, 03:25:36 PM
Also, I do not see charging the lipo only to 11.1 V as a solution as you never know when the lipo may konck off (unless you are much experienced)

At 11.1 volts, the Lipo has only 15% of the charge left in it and is useless. In fact you should not use Lipos below 11.2 Volts at no load voltage.

Everyone knows that Lipos have almost constant discharge voltage (but only upto a certain voltage) (Compared to NiMH / NiCd)  . A 3 cell Lipo will loose its power rapidly after falling below 9V which is dangerous. Deep discharge will cause the Lipo cells to swell and possibly catch fire.

A regulater can be disgned to take 12.6v as an input with 11.0v as output and ensuring that it gives warning signal, the moment INPUT voltage falls below 9v. I am sure Susheel can do some research and come up with some regulator of this nature.

Over charging a Lipo is as dangerous as deep discharging a lipo.

Quote from: saurabhhsrivastavaa on March 03, 2010, 03:32:38 PM
Everyone knows that Lipos have a constant discharge voltage (but only upto a certain voltage).

A lipo will not have a constant discharge voltage!

A lipo if fully charged at 4.25 V per cell and almost empty at 3.7. That cannot be called constant.

Quote from: vinay on March 03, 2010, 03:41:06 PM
A lipo will not have a constant discharge voltage!

A lipo if fully charged at 4.25 V per cell and almost empty at 3.7. That cannot be called constant.

Boss !!! By constant I mean almost constant discharge curve. I am comparing it with NiMh/NiCd discharge curves.

saurabh, Now I get it.

But a cut off of 11.0 volts is not very good for lipos, it can actually reduce your charge-discharge cycles by 30%.

In modern Lipo world, a voltage less than -load voltage of 3.3 or a no load voltage 3.7/cell are bad for Lipos. at 11.0 volts a Lipo has literally 5 % charge left and some Lipos unbalace very much right below 3.72 volts/cell. This may over discharge one of the cells if the low cutoff is kept at 11.0 as the monitor will be monitoring the total voltage.

EDIT: Sorry didn't read the thread completely. A cut of of 3V/cell or 9V for 3 cell is further worse.

Hi Vinay,

I certainly see your point.

But as far as my understanding goes, Lipos dead low voltage is 2.85v / cell. Anything below this will surely damage the cell. A brand new Lipo will be stored at 3.8v / cell which meas that there is no load on the cell. This is the ideal storage voltage for a Lipo. 

Most of the Lipo Voltage monitors are designed to monitor individual cells through the balancing port and sound alarm at 3.4 V /cell. This means that you may (though not recommended) discharge your cells to a min of 3.0 v/cell without damage.

http://cgi.ebay.in/Lipo-Monitor-4S-A-must-have-for-all-lipo-users-pm-4-c_W0QQitemZ150368071429QQcmdZViewItemQQptZLH_DefaultDomain_203?hash=item2302a2af05

I leave it to the experts for comment. 

Cheers!!!

Saurabh,

The modern Lipo monitors are designed to monitor and sound alarm at 3.3 to 3.4 V per cell. This is the Load voltage. When the lipo is disconnected from the ESC/motor, it may immidiately show >3.7 volts per cell.

It is always a good idea to discharge a lipo by 85% charge / in other words stop using it at when there is 15% charge left.

As you pointed out, discharging a lipo near to 3 V will NOT destroy it. But it will GREATLY reduce the available charge-discharge cycles by more than 50%, they start to puff sooner if always discharged to 3.0 V

I agree that a lipo is stored at 3.8V, at this voltage a lipo has only about 25 to 30% charge, which is though ideal for storing for long term when not used, but not ideal for using. A fully charged lipo will be atleast above 4.15 V per cell.

Hope this helps.

Thanks,
Vinay.

Thanks Vinay. I am in agreement with you

Cheers !!!

I found that the whole issue of over-discharging TX lipos a non-issue, as it takes a month or more for the voltage to drop from 12.6 to around 10.5v.  So just recharge it  once a month of so (without worrying too much about whether you have some charge left in the lipo). And make sure the TX is powered off when not in use. That's all

Our own LHS links where you get 8 cell Ni Mh battery packs and battery cases are here

http://www.funnhobby.com/showdetails.aspx?id=988

http://www.funnhobby.com/showdetails.aspx?id=602

http://www.rotor.co.in/show-detail.asp?prodid={32877513-9877-49BD-BFE9-19B90131AEE4}&pn=1

http://www.rotor.co.in/show-detail.asp?prodid={DAF4585B-194F-4229-B9C1-A42A76AE8296}&pn=5

http://www.rotor.co.in/show-detail.asp?prodid={021FAD8B-DC58-49CC-A4DC-1839CB3E36EC}&pn=1

Ya thats what I was talking about. But already having a 1100mAh Nicd, 1600mAh was not a big leap. If you are choosing between LiPo and NiMH, the capacity should be in the range of 2200-2600mAh and preferably a Low Self Discharge (Sanyo Anelope type). one

Great that we at least have some options from LHS.

Those NIMH packs are not LSDs.  , you use it or not they needs to be charged once in 2 months.

Quote from: vinay on March 04, 2010, 05:41:20 PM
Those NIMH packs are not LSDs.  , you use it or not they needs to be charged once in 2 months.

Are you referring to the ones  offered by funhobby/Rotor as posted by Sundaram, or the ones I got ? The pack I got has  Vapex 'Instant' LDS Nimh cells, same as Sanyo 'Eneloop' technology

http://www.component-shop.co.uk/html/instant.html

Not your cells dude, I have seen your cells. they are good.

This is from Wikipedia

Brand names for LSD NiMH batteries include:

Prolife from Fujicell
Ready2Use Accu from Varta
AccuEvolution from AccuPower
Hybrid from Rayovac
eneloop from Sanyo
eniTime from Yuasa
Infinium from Panasonic
ReCyko from Gold Peak
Instant from Vapex
Hybrio from Uniross
Cycle Energy from Sony
MaxE and MaxE Plus from Ansmann
EnergyOn from NexCell
ActiveCharge/StayCharged/Pre-Charged from Duracell
Pre-Charged from Kodak
Always Ready from Camellion

The Sony Cycle energy Ni Mh cells are one of the most comonly available LSD Cells

When Pros and cons of LSD Ni MH batteries versus normal Ni MH batteries are as under: -

Ni Mh available at 2.7 to 2.8 AH whereas LSD Ni MH available at 1.9 AH to 2.1 AH only and only sanyo is having 2.3 AH LSD Ni MH.

2.7 AH Ni Mh available for Approx Rs 185 to 210 (Uniross, Sony) and 2.5 AH available for Rs 120 to 150 (Kodak, Uniross, Sony) Whereas a 2.0 to 2.1 AH LSD is available for Rs 200 to 250 a cell ( Sony, Uniross, sanyo) and 2.3 AH is available with only sanyo but at prohibitively high cost but with www.20north.com at Rs 100 a piece only( Pack of 24 pieces @ Rs 2400/- I don't know how)

Normal Ni Mh looses about 5% of its charge on the first day after charge and continues to loose 1% of their residual charge, every day at cool room temp. Loss rate is higher if the ambient temp is higher. Can be reduced if stored in refrigerator (However has to be brought to room temp before use). In other words a fully charged 2.7 AH will become 2.6 AH in the first day and in about 20 days time will become 2.1 AH. I will take longer if stores in cool place.

On the contrary a charged 2.1 AH LSD Ni MH is only 2.05 AH after the first day Since it is loosing on reducing balance 20% of charge in first year) it will loose its 2% charge in the same 20 days time and will be 2.0 AH. Further all the cheaper LSD Ni Mh of less known brands are available with much lower AH capacity.

For an electric flyer who is required to charge his LIPO at least once in every month and surely before flying every time, Month is the max interval I am looking at before the next charge of Tx Cell which any case I would have to do in case of a Lipo. Why there is such indispensible requirement of LSD cells for Tx battery pack.

I would surely go for a easily available, cheaper, higher AH Normal NiMh which stores much higher AH in comparison to the LSD in the first month after the recharge.

Non LSD NiMh cells of Sony and Uniross are also known for thier excellent performance.

OK, here is the answers, Its all about personal preference again.

1)There is no meaning in comparing a 2.1 Ah LSD to 2.7 non LSD. As we stay in Inida and for the temp, I have personally measured that non LSD reach 2.1 AH in less than 2 weeks. and you know what happens in less than a month.

2)Since LSDs dont discharge faster on the shelf, you will get more charge cycles.

3) LSDs are not all that expensive. Its not necessary that you have to buy eneloops, buy turnigy, they cost 100 Rs for 2.2 Ah shipped from hobbycity (you dont even have to leave home if you have a credit card), and the performance comes close to eneloops. I have both eneloops and turnigy.

4)My point is, when you can invest in LSDs easily, then why buy non-LSDs?

5)With the investment on LSDs, rare fliers(who flies for 1 hrs, say alternate weeks) dont have to think about charging every month. They can charge once in 2 months also.

6)Also for people like you, who would want to carry extra set of batteries, just in case the existing batteries go down, then you dont have to keep charging those extra set every month. Just charge them once a year.

7)LSDs truely discharge to their rated capacity, no doubt about it.

8)I have lots of LSDs at home, And randomly when ever I suddenly feel the need for batteries for heavy usage (say 2 months after they have been charged), then I dont have to think of charging them then (when I need it urgently). I just put them in the equipment, be it a radio control Chinese car, camera, wall clock, ANYTHING! ANd they work for hours, as if they were charged just before using.

9)For low consumption device like wall clocks, LSDs are the best, for obvious reasons. Obviously this is just an example. I dont use them in wall clocks.

Now tell me once reason to buy non-LSDs other than saying that you would charge and use all the capacity on the same day, which is a very less probability unless you are a heavy camera user or day night RC flier!

It is all about purely personnel preference as you said. LSD and non LSD all are going to discharge rapidly in the first few month and then it reduces slowly since it is reducing balance only the rate is different for LSD and Non LSD. LSD survives with 75% to 85% at the end of year. Like it is convenient for me to recharge once in month plus similarly you are choosing to recharge once in two months plus.

For a person who flies only for one hour, two to three times in two month what difference it makes if you carry a battery with residual life of 10 hours or 15 hours in that period.

If you are going for LSD, if you can source it, have the finances for it, if surely do not want to charge the Tx and use all your charging time on LIPO than TX battery, then you should surely go in for LSD may be for the cool factor   as you said earlier.

Then why at all settle for cheaper LSD of lower AH, you should go for the best brand available, preferably the one with 2.1 Amps charging capacity to reduce your rare charging time to about an hour (your cool factor is important ), why charge for 7 to 8 hour.

Why leave at that you should surely use for your wall clock which is the only device where you change your battery once in a year it is the ideal device for usage of LSD.

Horizon Singapore has already introduced fuel cell with 300 times energy density than any other power source which can be used in flying platforms. In year plus they will surely introduce a pack small enough to be used in Tx also.

If at all any one can invent an aero model engine which requires refilling once in a year, Lipo which requires recharging once in a year, Life would have been lot simpler.

When availability of LSD becomes common as High AH Ni MH now, I can easily and will surely switch to LSD with the modification I have in my TX.

For my cool factor now I use a Citizen Eco Drive wrist watch which does not require battery change at all.    

My case in point here is, there is lot of prudence in going for an upgrade only when it is absolutely neccessary, which is easily available and which is economical in addition to keeping room for updating further when the availability of next higher technology becomes common.

There is no point in upgrading just because it has just been launched and you have the money for it. It is like computer RAM, In addition to the commonlly available just about latest RAM at cheaper rate, you will always have a newer 'The latest RAM' with higher GB and bus speed available for any one who can afford it. It is only that The latest will become half the cost in next six months and you will be surprised with next available "The latest technology".

When LSD becomes more common it will be available for 2.8 to 3.0 AH with More than 'C' charging rate. Then there is prudence in going for it and using the more commonly available Ni Mh for now.

I am not asking you to upgrade my friend, I am saying that people who are investing now on rechargeable Nimh can directly invest on LSDs. There is no problem with availability. HK always has it in stock!

And the price from HK is cheaper for LSDs even compared to local electronics shop Non LSD -NimH!

Also if you are charging once a month(even in case you/others don't use it) you reduce the charge cycles.

Also Using Turnigy LSDs does not reduce the Cool factor. They are in fact higher capacity then the eneloops. Eneloops = 2100 and Turnigy = 2200(but they store 2300). And its easily available, and its not like you need to invest in heaps in fact you invest less. Only thing is you need to wait for 20 days for it to get shipped


My final point is if you are investing/upgrading then it is best to use LSD as they are cheaper(from HK) and better than the non LSD nimh!

Even still if you insists that Ordinary Nimh are the way to go/ LSD are non available/ LSD are Costly / Still feel like charging every month for your satisfaction - Then Non LSDs are the way to Go.

Amen!

Wow!! thats a hell of a debate!! Keep on fellas!!

Even in Mumbai, the cost difference between regular and LSD is not that much to warrant the use of "regular" NiMh cells.

QuoteLSD are non LSD all are going to discharge rapidly in the first few month

Not true. Regular cells can lose as much as 10-15% in the first day itself and be down by 50% or more in a month. In contrast, good LSD cells will have 85% capacity after 6 months! That IS quite a difference.

I agree completely with Vinay on moving to LSD cells when replacing or making new packs. More so as they are now available locally at not unreasonable prices.

Change for the sake of change, certainly unnecessary.

I will go home and install Lipo today on the TX   

Quote from: sundaramvelar on March 05, 2010, 08:41:27 AM
When availability of LSD becomes common as high AH Ni MH now, I can easily and will surely switch to LSD with the modification I have in my TX.

I believe you missed my total case in point there.

But please at least charge your LIPO every month so that you do not end up with a Tx like the photographs posted by me earlier.   

The reason I got Lipo is due to the loose connect problems of the Nimh AND so that I don't have to change battery again and again

Quote from: sundaramvelar on March 05, 2010, 03:40:20 PM
But please at least charge your LIPO every month so that you do not end up with a Tx like the photographs posted by me earlier.   

Charging Lipo once a month is no way connected to those photographs.
Someone might have overcharged it, or used a crap charger or probably charged a puffed Lipo, or charged it every month with a crap charger thinking charging once in a month is good w/o even using the TX. 

I would charge my lipos when the voltage falls below 11.4 Volts not once a month unnecessarily. 

Lipos are LSD!