Life Battery Discharge Question
#51
RE: Life Battery Discharge Question
ORIGINAL: mach2
I have a Common Sense RC charger. Im doing a discharge right now and im gonna charge it back up and see what happens.
Its pulled out 1100mah and its still hangin at 6.4v. 2 hours at .5A discharge
Jeremy
I have a Common Sense RC charger. Im doing a discharge right now and im gonna charge it back up and see what happens.
Its pulled out 1100mah and its still hangin at 6.4v. 2 hours at .5A discharge
Jeremy
I use a .7 or .8 discharge rate on planes equipped with digital high torque servos, to give me an average that I can use to determine in flight durations.
You already know that you'll get a good six 15 minute flights on your plane before you'll have to worry about recharging the pack, though for safety double check it after the fourth flight.
#52
RE: Life Battery Discharge Question
ORIGINAL: mach2
Looking back on it, was there anything I should have done to the battery since it was new? I charged it and then used it for set up during my build as well as a lot of ground checks. Then charged it and took note of how much power it took in each time. Could I have not set it up right before the first use? I went through the manual and still haven't seen any special instructions.
and how often do you guys balance?
Looking back on it, was there anything I should have done to the battery since it was new? I charged it and then used it for set up during my build as well as a lot of ground checks. Then charged it and took note of how much power it took in each time. Could I have not set it up right before the first use? I went through the manual and still haven't seen any special instructions.
and how often do you guys balance?
For NiCD and NiMH I've seen many recommendations to use a lower charging rate for a longer period of time, on the initial charge. After that up to 1C, though a lower rate tends to make the packs last longer.
If time is not a factor I use .6-.8C for safety.
-
Re: Balance.
I TRY to balance my packs each time I charge them using a balance charger.
If I have too many to do in preparation for the next day, I may skip the balancing.
Some people only balance their packs after an interval, e.g. 10 charges...
#53
Refering to an LiFe 2100mA accu. Selected LiFe balance for 2S and 1A current but the charger didn't raise it above 03A and it took about 4 hrs to put 1200mA in it until I got bored and turned it off. Tried to select again, this time 2A, same thing...current won't raise above 03A. And from start to finish the pack voltage staid at 7,2v on the chg display and the cells went from 3,33 to 3,38v/cell. Same with the other pack. Why ? Before charging I start tuning the 50cc engine on the ground, and burned about one tank. During this running on the ground it took 1200+mA from the pack?! Thank you.
#54
Strongly suggest you read this entire article it is in my opinion the best information out there regarding this type of battery. There could be any # of reasons why it will not take a charge or charge slowly. LiFe chargers will taper off in charge rate as the cells become full. If you are using the balance tap to charge with ( and you should each time you charge) it could be you have a cell that is way out of bal and the charger will detect that and stop charging the cell that is higher. http://hangtimes.com/a123_batteries_for_giants_faq.html
#55
The fact that you see a charge rate lower than .3a indicates that the battery was pretty full when you connected it.
You put back 1200mA after running the engine, according to the charger but that could be an erroneous figure ( but correct as far as the charger is concerned ).
As the current tapers off the charger is trying to see a certain degree of voltage stability from the battery pack. It will keep giving the pack a trickle type charge looking for the voltage variation to flatten.
If the latter does not happen or takes too long, the charger will seem to indicate far more current put back into the pack than was actually consumed by your electronics.
One way I quickly assess the charge state of any battery, is by looking at the initial charge rate once charging begins and a few minutes later.
If a 2200mA pack with a charging limit at 2.2A, displays a charge rate of 2A or so, a minute into the charge cycle, I KNOW the pack has been discharged beyond 10-20% of full.
If in the same situation I see a .5A or less charge rate, I know the battery is almost charged and the charger is going to try to get that last 10% in far more slowly.
So your packs may not be stabilizing quickly enough for the charger, or you may need to adjust the charger's tolerance limits for full charge state. Most computer controlled chargers permit you to fine tune the latter.
#56
So I discharged the pack, thinking that if it starts the charge from "empty" it will start with the selected voltage. Charger discharged 1.288mA in 77min at 1A. Charger display at the end of chg.: 4v whole pack, first cell - 1,95v second-2,70...pretty disastrous I think. cell meter display: 6,2v, cell1- 3,183v, cell2- 3.065v without load. Start to charge the pack, selected 1C(2100mA) it starts with 0,5...I think the trash can is the answer... Don't know what to do...
#57
I suppose it has nothing to do with the fact that I'm charging them in the plane through the deluxe switch harness from Spectrum and not directly? Stupid question...but firs time I've charged them directly hooked up to the charged and I don't remember doing this low v charging...
#58
...when I start charging the pack, charger display shows: 0,5A chg rate, 7,20v (2SLiFe) cell1- 3,14v, cell2- 3,14v. Cell meter display: 6,445 v/pack. Any thoughts from all of this. Thank you
#59
ok, so I've decided to unplug the pack from the switch harness and the 2 meter cables one for chg other for balance plug as the plane was 2m from the charger. And guess what...now it charges at the established current. Go figure...
#60
Yup.
Reserve charging via the switch harness to top off the battery while you are at the field.
When you get home charge the pack directly. Ideally you should balance charge the pack every few charges if possible, though you need not do it every single time.
After a day of flying take the pack and charge it directly, then note how much current you put back in.
We fly some trainer planes very hard with about 20 flights per MORNING and the ignition LiFe packs usually only need around 1000mA put back in.
On the same planes I use 3S LiFe's with a regulator ( down to 5v ) and during the same time we burn about 1200mA pushing 7 cheap high torque digital servos on Giant Big Stiks.
Reserve charging via the switch harness to top off the battery while you are at the field.
When you get home charge the pack directly. Ideally you should balance charge the pack every few charges if possible, though you need not do it every single time.
After a day of flying take the pack and charge it directly, then note how much current you put back in.
We fly some trainer planes very hard with about 20 flights per MORNING and the ignition LiFe packs usually only need around 1000mA put back in.
On the same planes I use 3S LiFe's with a regulator ( down to 5v ) and during the same time we burn about 1200mA pushing 7 cheap high torque digital servos on Giant Big Stiks.
#62
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Youd have to ask Ed Alt (since he is the one that makes them) that question for a detailed answer. But Im sure its due to the safety feature in the unit. It prevents the back flow of power to a bad battery. That way (in the redundant system) if one battery goes bad, the good battery will not be drained by trying to charge the bad battery. The unit will not let the power go TO the battery. It only allows energy to flow FROM it. Also, when you recharge the batteries, you will be more likely to notice that one battery is taking a larger charge, making it possible to identify the junk battery. If the good battery is waisting energy trying to charge the bad one during the flights, they will be pretty much balanced out. If that happens, you may just think that you are using more power from flying style changes, and will not be able to identify which battery is bad (if you do realize one of them is bad)...
I think the inconvenience of of unplugging a wire to charge the batteries out weighs the safety that the unit provides. Plus, I wouldn't charge lipo's or life's through a charge jack anyway. Especially lipos. They shouldn't be charged in the plane. Unless someone is willing to take the chance of their plane catching fire for a little convenience. Its not worth it in my opinion. They should actually be charged out of the plane in one of those fire resistant lipo charging bags, in a safe area away from anything that could possibly catch fire. And not left unattended.
I think the inconvenience of of unplugging a wire to charge the batteries out weighs the safety that the unit provides. Plus, I wouldn't charge lipo's or life's through a charge jack anyway. Especially lipos. They shouldn't be charged in the plane. Unless someone is willing to take the chance of their plane catching fire for a little convenience. Its not worth it in my opinion. They should actually be charged out of the plane in one of those fire resistant lipo charging bags, in a safe area away from anything that could possibly catch fire. And not left unattended.
Last edited by mach2; 12-29-2013 at 12:42 PM.
#63
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Hey guys, sorry about if the above post didn't make sense in this thread. I got it mixed up with another thread that got on the subject of reduntant systems. But Im going to leave it and post the units from tech-aero since this a a semi related topic. I think everyone can benefit from considering using a reduntant system for safety.
Here is the unit, http://www.tech-aero.net/plr5, and here is the instructions on building a redundant system, http://d7kx18lgvr3p4.cloudfront.net/Tech-Tip%200601.pdf
The reason I thought this was a different post was because of the question about not charging through the charge jack since you cannot charge through the Tech-aero plr5 unit.
Hope this is helpful to someone.
Here is the unit, http://www.tech-aero.net/plr5, and here is the instructions on building a redundant system, http://d7kx18lgvr3p4.cloudfront.net/Tech-Tip%200601.pdf
The reason I thought this was a different post was because of the question about not charging through the charge jack since you cannot charge through the Tech-aero plr5 unit.
Hope this is helpful to someone.
Last edited by mach2; 12-29-2013 at 01:03 PM.
#64
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I have been doing this for near forty years and have never had a battery failure in flight, even back in the Ni-Cd days. But then again I am very anal about how things are done and checking everything often, which is how I have found a bad battery, a time or two, prior to flight.
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Hi guys, this is an old thread but wanted to give it a try since I am having a concern about LIFE batteries at the moment.
I am flying a gasser 35cc with HV Rx and Servos (Hitecs)...I am using Life 2100mah (6.6v) from Hobbico and I bought it new less than a month ago. The other day I told the plane to the field and the battery fully charged. When I measured the charge %, it was indicating 96%.
We did one turn and the muffler went lose so we landed. This was literally after 2 mins flight. While we fix the muffler back, I decided to check the battery and it was indicating 65% (!). 100% sure we measured correctly and we used two different testers. I was shocked and went back to Lipo.
However, I bought 3 LIFE and understood that they were good alternatives to LIPOS.
Anyhow, here my questions:
1. Is it safe to fly 35cc or 50cc using LIFE batteries?
2. How many flights (or time) should I be getting with a full battery?
3. Is the % curve flat on 65 until it drops and I should stick to the voltage coming out of the Jr plug they have?
I appreciate any help. Safe and joyful flying.
Mariano
I am flying a gasser 35cc with HV Rx and Servos (Hitecs)...I am using Life 2100mah (6.6v) from Hobbico and I bought it new less than a month ago. The other day I told the plane to the field and the battery fully charged. When I measured the charge %, it was indicating 96%.
We did one turn and the muffler went lose so we landed. This was literally after 2 mins flight. While we fix the muffler back, I decided to check the battery and it was indicating 65% (!). 100% sure we measured correctly and we used two different testers. I was shocked and went back to Lipo.
However, I bought 3 LIFE and understood that they were good alternatives to LIPOS.
Anyhow, here my questions:
1. Is it safe to fly 35cc or 50cc using LIFE batteries?
2. How many flights (or time) should I be getting with a full battery?
3. Is the % curve flat on 65 until it drops and I should stick to the voltage coming out of the Jr plug they have?
I appreciate any help. Safe and joyful flying.
Mariano
#66
Your battery checker is probably using voltage levels to check capacity, which is not very accurate and can give poor results.
e.g. you may believe the pack is fully charged using the checker when it may not be.
I advise putting a watt meter between the battery and your plane and moving all the servos to their extremes while putting a load on the surfaces.
I'll bet that your servos are pulling down far more current than your battery is capable of handling.
I use LiFe's for my 50cc planes and larger but I never use a single 2200mAh pack as I know this is far too small for the current draw.
e.g. you may believe the pack is fully charged using the checker when it may not be.
I advise putting a watt meter between the battery and your plane and moving all the servos to their extremes while putting a load on the surfaces.
I'll bet that your servos are pulling down far more current than your battery is capable of handling.
I use LiFe's for my 50cc planes and larger but I never use a single 2200mAh pack as I know this is far too small for the current draw.
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Hi,
Following up on this subject, I wanted to share some discoveries.
I have LIFE HOBBICO 6.6v 2100mah. I fully charged at 1AMP and then flew my 35cc for 5 minutes. Before take off the battery was 97% and when landed it was 65%. Same as my first post in this Thread.
However, someone recommended me to do a proper measurement of the MAH consumed per flight to have a better indication of how many flight I can safely do with that battery.
So, when I charged it again, the capacity charged was 115mah...Now, here is my question:
Does it necessarily mean that each 5 minute flight will consume 115mah and with 2100mah battery, I could put 4-5 flight without risking the aircraft?
Is it reasonable to assume that 10mins flight with same level of inputs will be around 300-350mah?
How are the mah related to the voltage? I understand that LIFE should go under 2.5v per cell. So, how can I also calculate the voltage discharge rate and the mah?
Thank you for your experience and will to share knowledge.
Mariano
Following up on this subject, I wanted to share some discoveries.
I have LIFE HOBBICO 6.6v 2100mah. I fully charged at 1AMP and then flew my 35cc for 5 minutes. Before take off the battery was 97% and when landed it was 65%. Same as my first post in this Thread.
However, someone recommended me to do a proper measurement of the MAH consumed per flight to have a better indication of how many flight I can safely do with that battery.
So, when I charged it again, the capacity charged was 115mah...Now, here is my question:
Does it necessarily mean that each 5 minute flight will consume 115mah and with 2100mah battery, I could put 4-5 flight without risking the aircraft?
Is it reasonable to assume that 10mins flight with same level of inputs will be around 300-350mah?
How are the mah related to the voltage? I understand that LIFE should go under 2.5v per cell. So, how can I also calculate the voltage discharge rate and the mah?
Thank you for your experience and will to share knowledge.
Mariano
Last edited by mbosaz; 04-11-2016 at 07:51 AM.
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Your battery checker is probably using voltage levels to check capacity, which is not very accurate and can give poor results.
e.g. you may believe the pack is fully charged using the checker when it may not be.
I advise putting a watt meter between the battery and your plane and moving all the servos to their extremes while putting a load on the surfaces.
I'll bet that your servos are pulling down far more current than your battery is capable of handling.
I use LiFe's for my 50cc planes and larger but I never use a single 2200mAh pack as I know this is far too small for the current draw.
e.g. you may believe the pack is fully charged using the checker when it may not be.
I advise putting a watt meter between the battery and your plane and moving all the servos to their extremes while putting a load on the surfaces.
I'll bet that your servos are pulling down far more current than your battery is capable of handling.
I use LiFe's for my 50cc planes and larger but I never use a single 2200mAh pack as I know this is far too small for the current draw.
So you put redundant batteries or just bigger mah?
#71
So your reading depends in large part in how that meter works. Many look at the last peak voltage and compare that against the current voltage to give you a percentage reading.
This can be very inaccurate, especially if the battery experiences a high initial drop off voltage rate, then levels out during normal discharge.
Think of a graph with a high initial peak, that drops to a fairly level plateau. The meter should only check the voltage across that plateau, but ends up including the peak in the calculation.
So, when I charged it again, the capacity charged was 115mah...Now, here is my question:
Does it necessarily mean that each 5 minute flight will consume 115mah and with 2100mah battery, I could put 4-5 flight without risking the aircraft?
Is it reasonable to assume that 10mins flight with same level of inputs will be around 300-350mah?
How are the mah related to the voltage? I understand that LIFE should go under 2.5v per cell. So, how can I also calculate the voltage discharge rate and the mah?
Thank you for your experience and will to share knowledge.
Mariano
Your best bet is to get a WATT meter and place that between your battery and electronics.
Then move all your servos to their extremes while putting a bit of a load on one or more (e.g. put pressure on the surface to resist the movement ). Check what the peak draw is on the watt meter as you do this and as you quickly reverse servo direction.
When the servos see movement resistance or change direction quickly they exert a quick but very high draw on the supply. This draw can be as short as 10-20ms, but if your packs cannot keep up, it will be enough to cause a receiver brownout or cause the servos to react strangely.
Any good WATT meter will show peak AMP draw amounts and maximum voltage drops or peaks.
If you find that the total instantaneous draw is less than the 80% of the stated max draw of the battery, your assumptions about time and the number of flights should be safe.
2100mAh packs are so light that on I always use two receiver packs hooked up via a “Y” cable on 20cc or larger planes.
This gives me an effective 4200mAh pack, with the safety that the packs will certainly meet the power draw demands.
I periodically check each pack separately to assure that neither has gone bad.
I just finished building a couple of .60 Stiks to use as club trainers. After I found that the peak draw never exceeded 700mA instantaneous, I went with one 2100mAh LiFE pack for the electronics and one 2000mAh pack for the gas electronic ignition. I expect three SOLID hours of flying before I have to start to worry about charging.
Initial ground tests bear this out… 186mAh put back into the pack receiver after one hour of engine break in “on” time.
#72
Also a WATT meter is a "must have" in my book, even if you are not flying electrics.
It is great at showing you exactly what is happening with your electronics. It can help you balance servos, spot binding issues, set travel maximums, etc. etc. etc.
It is great at showing you exactly what is happening with your electronics. It can help you balance servos, spot binding issues, set travel maximums, etc. etc. etc.
#73
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It sounds like you used a VOLTAGE meter to check the batteries.
2100mAh packs are so light that on I always use two receiver packs hooked up via a “Y” cable on 20cc or larger planes.
This gives me an effective 4200mAh pack, with the safety that the packs will certainly meet the power draw demands.
I periodically check each pack separately to assure that neither has gone bad.
2100mAh packs are so light that on I always use two receiver packs hooked up via a “Y” cable on 20cc or larger planes.
This gives me an effective 4200mAh pack, with the safety that the packs will certainly meet the power draw demands.
I periodically check each pack separately to assure that neither has gone bad.
I was also reading about redundancy.
I understood that if you simple plug two batteries through a Y cable then the batteries will not be redundant and will discharge together (instead
of backup).
the two alternatives I was offered were: plug in different channels to the receiver (Futaba) or buy accesories to make batteries resundant. I found Emcotec selling one.
do you agree?
#74
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A lot has been answered above, but I'll just say that for figuring out how much time a certain sized battery will give is done easiest by flying and charging. Whenever I've got a new plane I'll do a 5 min maiden and charge. This will give a baseline of what the plane uses in about 5 minutes. If all looks good I'll put two more 5 minute flights on it, then charge. Obviously it should take about twice as many mah to top them off this time.
I pretty much never fly longer than ten minutes per flight. So, doing the math I'll make sure I can put in 5-6 ten minute flights with the battery/batteries I'm using and I'll fly three ten minute flights. Then I charge to make sure the mah usage is still staying consistent to what I found with my initial tests.
Now to my rule of battery size. I'm not one who likes to put huge batteries in my planes, but I also have a 50% rule. I don't have a problem with charging after 5 flights because I typically fly each plane 3-4 times per outing anyway. So if a particular plane uses 1,000mah over 5 flights, I'll need a 2,000mah battery. I would be okay with using slightly more than 50% of the batt capacity, but not much and I try not to make it a habit.
On "larger" aircraft I'll use redundant systems. Take the example above (using 1,000mah in 5 flights) I'll usually use something like two 1,500 mah packs just for a little extra to give me a buffer in the situation that one battery fails and the other needs to take up the slack. Also, make sure that each battery has a high enough C rating to handle the extra draw if it needs to be the sole workhorse.
I've been using a Powerbox from Redwing for a while for a redundant system on a 50cc plane and it makes it pretty easy. Or you can use some of Ed's nifty products to make a redundant system. Here's where you can find his products. I love his IBEC and I use it on all my gas planes to safely power the ignition without having to add another battery. http://www.tech-aero.net/
Here's pretty much everything you need to know about making a truly redundant system from Ed Alt of Tech-Aero. If you ever have any questions for him just give him a call. A super nice and helpful man.
http://d7kx18lgvr3p4.cloudfront.net/Tech-Tip%200601.pdf
I pretty much never fly longer than ten minutes per flight. So, doing the math I'll make sure I can put in 5-6 ten minute flights with the battery/batteries I'm using and I'll fly three ten minute flights. Then I charge to make sure the mah usage is still staying consistent to what I found with my initial tests.
Now to my rule of battery size. I'm not one who likes to put huge batteries in my planes, but I also have a 50% rule. I don't have a problem with charging after 5 flights because I typically fly each plane 3-4 times per outing anyway. So if a particular plane uses 1,000mah over 5 flights, I'll need a 2,000mah battery. I would be okay with using slightly more than 50% of the batt capacity, but not much and I try not to make it a habit.
On "larger" aircraft I'll use redundant systems. Take the example above (using 1,000mah in 5 flights) I'll usually use something like two 1,500 mah packs just for a little extra to give me a buffer in the situation that one battery fails and the other needs to take up the slack. Also, make sure that each battery has a high enough C rating to handle the extra draw if it needs to be the sole workhorse.
I've been using a Powerbox from Redwing for a while for a redundant system on a 50cc plane and it makes it pretty easy. Or you can use some of Ed's nifty products to make a redundant system. Here's where you can find his products. I love his IBEC and I use it on all my gas planes to safely power the ignition without having to add another battery. http://www.tech-aero.net/
Here's pretty much everything you need to know about making a truly redundant system from Ed Alt of Tech-Aero. If you ever have any questions for him just give him a call. A super nice and helpful man.
http://d7kx18lgvr3p4.cloudfront.net/Tech-Tip%200601.pdf
Last edited by mach2; 04-12-2016 at 11:25 PM.