View Full Version : First: 2008 Batteries are D-Y-I-N-G.
Tom Line
21-09-2008, 19:08
I haven't seen this communicated on Chief Delphi yet, so I wanted to get this out there.
I know of three teams this weekend that had a cell/cells in their batteries die.
The battery appears to be fully charged, but when you put it on the bot it drops to 6-7 volts (or lower) very quickly. It killed a match for us, and two other teams we talked to have also had issues with the 2008 batteries dying on them.
Let's get a record going - if these batteries are indeed an issue as I believe they are, we need to get word to First so they can rectify the issue. That is a lot of money to spend on batteries only to have them die in less than a year. We've still got 2006 batteries (from the old manufacturer) that are working!
We had this happen also, it says it is fully charged but as soon as you start the match it goes to 6-7 volts. Also we lost of our playoff matches that we could of won. BTW, the batteries are getting really hot, it melted the pneumatic tubing, there is no short on our whole board. We double checked.
Schnabel
21-09-2008, 19:13
I haven't seen this communicated on Chief Delphi yet, so I wanted to get this out there.
I know of three teams this weekend that had a cell/cells in their batteries die.
The battery appears to be fully charged, but when you put it on the bot it drops to 6-7 volts (or lower) very quickly. It killed a match for us, and two other teams we talked to have also had issues with the 2008 batteries dying on them.
Let's get a record going - if these batteries are indeed an issue as I believe they are, we need to get word to First so they can rectify the issue. That is a lot of money to spend on batteries only to have them die in less than a year. We've still got 2006 batteries (from the old manufacturer) that are working!
At the beginning of the build season, the TechnoKats tested everyone of our batteries from previous years and from this year, and the ones from this year had mid to low range on them. I found this weird as we have batteries dating back to 2001 and we have never had problems with them. Also when we did the test, last years were the strongest! That was shocking to me that 1 year old batteries were stronger than new batteries from the same manufacturer.
ATannahill
21-09-2008, 19:14
When were they charged? Usually always they will show 12 when doing nothing, no matter what the real voltage. If you try to do something they will jump to the right voltage.
Tom Line
21-09-2008, 19:41
They were charged. We're not using the somewhat...lacking... charger from first either - we're using a far better one. No - this is definitely something going on with the batteries. It's nice to see other folks reporting the same thing.
We know the standard rules - you don't put them on concrete, never overcharge them, don't let them sit with no charge on them at all, fully discharge them before charging them again...
... batteries ... We know the standard rules - you don't put them on concrete, ....Unless the cases are unusually conductive, or there is a significant thermal gradient between the top and bottom of the batteries when they are placed on said concrete (or whatever they might be resting upon), I think you can stop worrying about putting them down on concrete. See the page at this URL
http://www.thebatteryterminal.com/TechTalk_Batteries_on_Concrete.htm
Wow - glad you posted this.
1 of our 2008 batteries is doing very poorly. I figured we dropped it or something.
psyco_klown
21-09-2008, 21:26
well First did give us new chargers this year. We found that that there was a 6v charge or a 12v charge buttons and if u barely touched the button it changed the mode.
Our 2008 batteries aren't holding charge well either. One of them flat out doesn't work, and the other is pretty bad.
DonRotolo
21-09-2008, 22:12
fully discharge them before charging them again...NO! Absolutely never, ever do this!
Lead-acid batteries are not like NiCd or NiMH batteries - a full discharge to a lead-acid battery will significantly shorten the life of the battery.
DO keep them charged all the time, recharge them immediately, don't let them sit all summer discharged. A charge in a gel cell will last 60-90 days before it's a problem.
Don
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Joe Ross
21-09-2008, 22:31
Here's a thread from earlier in the year about this: http://www.chiefdelphi.com/forums/showthread.php?t=66541
we had problems at IRI, but it turns out our charger was broke, so before you get rid of your batteries check to see if it the charger. It cost us like three matches.
Al Skierkiewicz
21-09-2008, 23:59
For you who have had battery problems, the absolute cause comes down to a variety of issues. I have been in contact with the manufacturer who is testing batteries using the same charger supplied by First. To date they have not reported anything out of the ordinary. Teams should not compare MK batteries with previous years as they are different in construction. There is a difference, between gell cell batteries and the MK AGM batteries. It would appear that the MK batteries are a little more sensitive to shock and mishandling. The hotspots in a battery case are likely the result of two or more plates in a cell being forced together by this rough handling. The result is a short in that cell. Heat is an indication of high current flow. AGM batteries are also sensitive to overcurrent charging. Charge currents higher than 6 amps cause the plate structure to deform also resulting in cell shorts. This is also true of batteries that are stored at high temperature or repeatedly put on charge without rest. Allow batteries to cool before returning to charge following a match. I have also noted many teams who lift and carry the battery by the leads. The battery is not designed for that and internal damage is the result. If you have team members who practice this method, suspect that as one of your causes.
Finally, all batteries have a finite life cycle. First batteries since 2001 all have been about 400 charge/discharge cycles max. Repeated high current discharge (i.e. full discharge in a single match) shortens this life by half or more.
=Martin=Taylor=
22-09-2008, 01:25
we had problems at IRI, but it turns out our charger was broke, so before you get rid of your batteries check to see if it the charger. It cost us like three matches.
Which charger? The new one ('08)?
How did you know it was broke? Lights but no charge?
Which charger? The new one ('08)?
How did you know it was broke? Lights but no charge?
We were experiencing problems every other match at IRI and we kept checking our electronics but could not find anything wrong...
we told Cory from 254 and he told us they had similar problems in the past... he told us to check the charger... we took the charger out of the rotation, and didnt have any more problems the rest of the competition. The charger had no visible signs of failure, or malfunction. Cory really helped us out!
I believe it was an 08 charger.
Keaton
Bomberofdoom
22-09-2008, 13:52
One of our games in the quals in Israel were affected by that dead cell battery.
The electroincs team-member swore to me 1000 times that he saw it full.
and it did say so later, but on the field it didn't show that way.
We had one bad battery this year, but that was due to the top of the battery coming loose and leaking somewhere. We disposed of it properly, but it took a few minutes to figure out why it wasn't working. I noticed that the top was lose, peeled it back, found a rubber cap missing and an empty cell.
Speaking of battery problems. Anyone know why the battery on my laptop will last for 30 minutes at 70+% then instantly (and I really many instantly) go to 7%. It's about a year old.
jawebste
23-09-2008, 08:22
Please add another team to the list of documented issues. We also competed at Kettering this weekend and had batteries go from 12V to 5 or 6 during the match. They were extremely hot when we took them off. We only have 07 and 08 batteries as we are a newer team. We will segregate and monitor. Is there anyway to absolutely check for a "dead" cell?
Thanks,
Jean-Ann Webster
Mentor HAZMATs - 2145
Al Skierkiewicz
23-09-2008, 08:55
Jean,
These batteries are made up of 6, 2 volt cells in series. A bad cell will be indicated by a two volt drop in terminal voltage. If the cell is truly dead, the battery will read 10 volts or slightly higher when removed from the charger but not higher than 12 volts. Each cell is made up of several plates, interleaved positive and negative, with a glass mat separating the plates. Should the electrical connection to any of the plates be broken then the cell will have reduced capacity. If any of the plates should be touching then the cell will self discharge causing high internal heat. There are two tests which will determine which defect is causing the problem.
Charge the battery and remove from the charger. Attach a voltmeter and monitor the terminal voltage. A good battery will show slightly higher than 12 volts for several minutes and then fall to 12 volts. If it begins to fall below 12 volts in the first 30-60 minutes and then remains at 10 volts (or a multiple of 2 volts), you have a battery with damaged plates touching in an individual cell. One area of the case should be warmer than the rest of the case. If the battery remains at 12 volts, then you must load test it. We use the Mountain Radio CBA-II. With this computer based tester, you can draw a steady 7 amps and chart the terminal voltage and it will calculate the amp-hour rating. A cell with a few broken plates will be indicated by an drop in terminal voltage of 2 volts before the battery becomes discharged. The following picture compares three bad batteries with a good battery using the CBA. You will see in this graph the normal discharge curve in black, two highly reduced capacity cells in blue, a single reduced capacity cell in green and a internittant cell in red. The "green" battery was reported to be suspect during practice at home where the robot was run for 15 minutes at a time. The "red" and "blue" batteries were also discoveered during practice but the intermittant nature of the red battery confused everyone until this test. Without the constant discharge, all of the batteries showed as 12 volts at the OI, when the robot was not moving except the "red" which showed a varying voltage.
It is likely, all of you have batteries that have one or more cells that are diminished capacity without knowing it. This is particularly true of batteries that are from 2006 or earlier due to the number of charge/discharge cycles they have been put through.
33 has had issues with a couple batteries, but we determined it was due to really hard impacts. This years game lended itself to some rather spectacular crashes. 1 battery had a visible deformation, and the other had a noticeable hot spot right after the match. As Al said we suspect internal damage on both of those batteries (the bulged one was rather obvious.
As pointed out by others, make sure you read up on your batteries, Lead acid, NiCD, NiMH, and Li-Ion all have unique peculiarities to them. Some like to be deep cycled, others will get destroyed doing this. Some have memory, some don't. Some give off a superficial full-charge when really they aren't full. Assuming whats good for one type is good for another can be very dangerous and at a minimum, costly.
1075 was also at Kettering this weekend (Thanks 910, 67, and 2619), and we too had battery issues. In the week leading up, we had a battery that showed full charge and dropped immediately under any load (even the RC was enough to instantly kill it). We've had a couple of them go bad with swelling on chargers, including 1 this weekend that wasnt even ours, we had borrowed it from another local team and brought it with us since we knew ours suck. I gotta say, i'm not a big fan of the MK batteries. The Exides took a much harsher beating and were fine. We still have at least one of the old Exides in active service for practice and off-season events. Its the best battery of all the ones in active service and based on its case is no less than 4-5 years old (I think it was a 2004 kit battery).
That being said, we've swelled a few of the old exides too, but I think we only have 1 good MK now, and we've had 6 of them.
Sounds like you have too powerful of a charger.
EricVanWyk
23-09-2008, 11:10
Sounds like you have too powerful of a charger.
Using a lower current charger will extend the life of your batteries. However, I think Al has shown that this is a separate, more painful problem.
Al Skierkiewicz
23-09-2008, 11:39
If you check the MK battery site you will find that the team battery specifies charging at 5.4 amps. That is why the robot rules have stipulated a smart charger of 6 amps or less as the only charger allowed for batteries on an FRC robot.
Speaking of battery problems. Anyone know why the battery on my laptop will last for 30 minutes at 70+% then instantly (and I really many instantly) go to 7%. It's about a year old.
If it has a Li based battery, I have heard that if they are deeply discharged, they will show an artificially high charge level right after being pulled off of a charge cycle. I know this is tru of my cell phone. If it dies, it takes a really long time to get a full charge in, however it says full after only a short while, it will completely discharge in a short while.
At competition (where the borrowed robot swelled) we ONLY use the kit chargers (this year and previous years). At home we have occasionally used our bigass charger designed for car batteries (Motomaster 2A/35A/200A), but we only use it when time is of the essence and we dont have any charged batteries because we know its bad for the batteries.
In any case, I think the Exides were built to a much more robust standard, which is why we're able to put them through so much more abuse. The MKs just don't have the durability required to stand up to a full lifespan in an FRC bot.
Obviously, we don't leave batteries on a charger like that for more than a couple minutes at a time, that would just be stupid.
EricVanWyk
23-09-2008, 19:30
At competition (where the borrowed robot swelled) we ONLY use the kit chargers (this year and previous years). At home we have occasionally used our bigass charger designed for car batteries (Motomaster 2A/35A/200A), but we only use it when time is of the essence and we dont have any charged batteries because we know its bad for the batteries.
I can't even begin to describe how bad an idea this is: This practice is a liability.
Al Skierkiewicz
24-09-2008, 07:38
I can't even begin to describe how bad an idea this is: This practice is a liability.
When charging any battery, some of the charge current is given up as heat within the battery. When you try to ram a lot of current, the internal heat does not have time to migrate to the outside of the battery case. So you may think by checking the case that the battery is doing fine at the higher current. However the internal (spot) heat may have exceeded the boiling point for the electrolyte causing excess gas pressure and spot heating of the plates. If the electrolyte actually boils enough, the plate becomes coated with residue which reduces the available plate area and therefore reduces the amount of current density in the battery. At some point, the pressure relief valve may also open releasing some moisture. The max current specification on the battery is dependent on the amount of electrolyte in contact with the plates. If you reduce the plate area, the amount of available electrolyte or raise the temperature of the battery, the output current is affected.
I've been doing FRC for 8 years, and without a doubt, the Exides we used 01-06, we're so much more reliable. Last year, by the time we got to Atlanta, our batteries (unknown to me at the time) were so unreliable. I know I'm not a battery expert, but I thought I knew enough about keeping them charged, marked, and tested to know that we can use them on our robot. Unfortunately we lost two matches due to a low battery problem. We all blamed our battery crew - they swore it was a well charged battery - and later we determined that two of the batteries will reading 13+ Volts and then drop to 6-8 Volts within seconds of the start of a match. Very frustrating. The problem definitely got worse as time went on - most likely to violent robot action/crashing (or a student dropping/rough handling).
I'm glad to know I'm not the only one unhappy with the MK batteries from last year.
DonRotolo
24-09-2008, 20:54
Anyone know why the battery on my laptop will last for 30 minutes at 70+% then instantly (and I really many instantly) go to 7%. It's about a year old.That can also be an artifact of the way battery charge level is calculated by the computer.
with a glass mat separating the platesThink of pink fiberglass insulation, but squished a bit to make them somewhat stiff (but not rigid). Some call AGM (Absorbed Glass Mat) batteries by the name "Fleece" batteries, the fiberglass sheets look like wool fleece.
we had a battery that showed full charge and dropped immediately under any load
That indicates a broken electrical connection inside the battery, either between cells or from cell to terminal. Usually caused by mishandling. The connection can handle the microamps of the voltmeter, but not the milliamps (or more0 of a real load.
Don
.
http://www.batteryuniversity.com/index.htm
very cool battery link.
Seth Mallory
08-10-2008, 23:29
I would like to know what people are using to test their batteries and what standard they are using. Thank you.
Seth
Eugene Fang
08-10-2008, 23:36
We had quite a few batteries die on us. We think it is because, during a demo, we drained them very low, like 5 volts on the OI low, causing the plates inside to corrode.
When "charged," the voltmeter says the battery's voltage is fine, but it cannot deliver enough current to run the robot. So as advice to all teams, NEVER discharge your battery to the point where, on the OI, it reads a very low voltage.
We wasted a few practice rounds at SVR last year because we were putting batteries that said 13+ volts on the voltmeter on them, but couldn't deliver current, so the robot couldn't move.
Al Skierkiewicz
09-10-2008, 01:15
Seth,
We use the CBA II battery analyzer from West Mountain Radio. If you look earlier in this thread you will see actual curves from actual batteries.
Pikat,
I know that this will sound weird but teams who draw lot's of current during driving can easily draw the battery below 5 volts during those high current demands. The internal resistance of the battery is 11 mOhm so a 400 amp draw will drop the terminal voltage of a fresh battery by 4.4 volts. At the end of a match where the internal resistance rises, this resistance will cause a further voltage drop.
Everyone,
A voltmeter only tells you the "open circuit" voltage of the battery. A voltmeter does not draw current (not enough to change the reading) to cause a drop across the internal resistance of the battery and therefore is not a good indicator of battery health. A current tester will show what the battery is capable of delivering under a load. The CBA II will draw up to 7.5 amps and West Mountain makes a high current device as well. However, one must know what the data tells them. It is possible that the battery has reduced capacity in that it can only deliver current for a fraction of the time a good battery can, the battery cannot supply current at full voltage or a combination of the two. A battery that cannot supply current for a normal length of time has some internal condition that prevents correct operation. I know that this is a foreign concept, but the data sheet specifies these batteries to have a 400 charge/discharge cycle life. It is very easy for a team who only keeps a few batteries in their inventory to run 400 cycles in a season between practice,demos and events. Charge when the battery is hot, store at temperatures near or below freezing, or deplete a battery in just one two minute match will shorten that 400 cycle life by half or more.
Eugene Fang
09-10-2008, 01:21
Pikat,
I know that this will sound weird but teams who draw lot's of current during driving can easily draw the battery below 5 volts during those high current demands. The internal resistance of the battery is 11 mOhm so a 400 amp draw will drop the terminal voltage of a fresh battery by 4.4 volts. At the end of a match where the internal resistance rises, this resistance will cause a further voltage drop.
Good point. I was referring to the fact that we were running our robots for hours at a time (not high load, just driving it around) without changing the battery. In other words, these lead-acid batteries don't like to be fully discharged.
eugenebrooks
09-10-2008, 01:54
I would like to know what people are using to test their batteries and what standard they are using. Thank you.
Seth
We load our batteries at 20 amps, and measure the time that
it takes to drop to 11 volts. We don't go all the way to 10.5 volts
because deep discharge is not good for the battery. We load
using a constant current device, but you can do a reasonable
job with high power resistors from digikey. We qualify our
batteries every season, tracking their performance year to year.
You can make yourself a tester with high power resistors,
a fan to keep them cool, and a spike. It is not a constant
current load, but it is close enough. You can measure the
voltage using a voltage divider hooked to an analog input.
The old EDU RC is very good for this. It is a great project
for your robot team to do, producing a load tester that will
get used every year.
Eugene
Kims Robot
10-10-2008, 14:55
Teams should not compare MK batteries with previous years as they are different in construction. There is a difference, between gell cell batteries and the MK AGM batteries. It would appear that the MK batteries are a little more sensitive to shock and mishandling.
I would like to disagree with the bold in this statement. It is taken a touch out of context, but I will explain why. In the world of engineering, we buy parts to meet a specification...
Semi-Tangent:I happen to work in the military engineering world where the standards are extremely high - could you imagine dropping a cellphone off a 3 story building and have it work when you pick it up? Our radios are required to do this. Could you imagine leaving your car stereo underwater for 3 days, expect to pull it out, let it dry for an hour and have it work? One of our radios DID that during Katrina & saved lives... Could you imagine exposing your robot to -30degreesF or +120degreesF and expect the electronics to still work? Our radios have to. They have to and we design them to meet that. We cant use parts in them that dont allow us to meet our -30degree requirement. We cant use a battery that will only last in our product for an hour, or our soldiers wouldnt be able to carry enough batteries to last a mission.
Yes, these are extreme examples, so whats my point? My point is that FIRST is FORCING us to use this vendor and this battery, they have lain the specifications for us. We dont really know why MK... did they get a better discount/donation or a sponsorship donation from MK? did the old battery vendor not want to donate anymore? did they think that these batteries were actually better? Who knows. But the reality is that these batteries ARENT as good as the old ones, and teams SHOULD be comparing them. If there is something better out there, that meets the specification of a FIRST event better, we should be allowed to use it. Teams are right to raise an eyebrow because they are spending a lot of money on batteries. Some try to keep up to 10 at a time alive, and thats a BIG expense. At bare minimum you need 4 if you are going to end up in the finals (unless you beg & borrow), and having to buy new ones put us all on edge. Now it appears that there is evidence that they arent as robust and dont hold up to the riggors of a FIRST team's usage as well as the old ones. So maybe we/they should revisit the options...
My point being that Cellphone & Radio designers alike, we all design/engineer FOR our users. We are using motocycle batteries... they are not designed to be taken in and out, dropped, handled incorrectly, charged and discharged over and over again... so if we are using something NOT for its intended use, we need to find the part that most closely matches our specifications and will last the longest so teams dont have to take on that expense over and over again.
BlackBird11891
06-02-2009, 00:05
so were all in the shop the other day with the batteries on the chargers i leaned back on the table and burned my arm (not really bad, but it left a mark) i quickly turned around to notice that one whole cell of the battery had bulged out and the battery had gotten up to 165 degrees and was leaking out the top
For all those who are thinking this the battery was fully dead when we put it on and hadn't been on the charger for 2 long before this happened
so were all in the shop the other day with the batteries on the chargers i leaned back on the table and burned my arm (not really bad, but it left a mark) i quickly turned around to notice that one whole cell of the battery had bulged out and the battery had gotten up to 165 degrees and was leaking out the top
For all those who are thinking this the battery was fully dead when we put it on and hadn't been on the charger for 2 long before this happened
It sounds like the charger is messed up... I bet Thomas broke it. Tell him Ryan Nazaretian sent you.
Just remember to dispose of the battery properly, and also keep a close eye on that charger. Is it one of the new smart chargers, or one of the older chargers?
I'm not too fond of 'Smart' chargers after one almost burnt down my work shop. Mine had an automatic trickle charge cycle that was meant to keep on a battery. Unfortunately, it failed with a deep cycle marine battery and burnt through the large charging cable (designed to carry 70AMPS). I was very fortunate that it was lying on the concrete instead of on top of my workbench.
redbarron
06-02-2009, 02:06
We have also had a problem with the newer batteries. I have been in FIRST since 2002 and have had TWO Exide batteries go bad,(not including the oldest ones which have been retired when they lost the ability to hold a good charge) and to date We have had FOUR MK Batteries go bad on us. Just the other day I had one start to heat up and leak out of the top while charging. We order 10 every year and over the years we have a large stock of Exide batteries that still work. I understand that FIRST is probably getting them discounted and all but if the batteries are not holding up as well as the old ones.... Maybe one solution would be to still supply and offer MK batteries, but lift the restriction of using other batteries so those of us that want to pay a little more for batteries that last longer can do so. I do not think that the MK batteries are a bad product, but I do think we are using these batteries in a way they are not designed to hold up to as well as the batteries of the past have proven to.
My team has never really had many batteries to our name, but from my experience, the exides DID hold up better.
Engineer
06-02-2009, 12:50
Reading through all these posts, Al and Don make some excellent points here. I want to add a little information for those that don’t go to the battery university website or want to spend hours researching battery characteristics.
If you discharge a lead acid battery too far, you hurt the battery and its amp hour capacity will be reduced.
Typical discharge to levels for batteries, or don’t go below this charge level.
Automotive batteries 80%
Marine batteries 50%
Deep cycle batteries 20%
Automotive batteries should not be discharged below an 80% charge level or you’ll hurt the battery. There is only 20% of the charge that is usable but the automotive battery will deliver more amps for the same physical size when compared to Marine or Deep cycle battery. In an automotive application the battery is discharge a small amount very shortly starting the engine and then is recharged by the alternator.
The FIRST battery seems to fall into the Marine category as the cycle life is greatly reduce if the charge drops below 50%.The information below is from the MK Battery website.
Life expectancy:
Cycle Use: 100% depth of discharge 250 cycles
80% depth of discharge 350 cycles
50% depth of discharge 550 cycles
What this means is that if you continually run your batteries down to low charge levels, you WILL significantly reduce the capacity of the battery.
On a side note, I don't like the battery charger FIRST supplies but they are better than the older non-smart chargers. I've seen these not sense properly and over charge batteries. This was probably due to a defective battery. I prefer the Black and Decker (used to be Vector) Smart Chargers. They use a three stage charging technology that helps extend battery life. I've given away or thrown away all my old battery charges for these new chargers, they are that much better.
FYI Some AGM batteries have platinum on the glass mat. This helps as a catalyst to recombine the oxygen and hydrogen bubbles if the battery is over charged or charged at too high of a current.
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