View Full Version : MK Battery Problems
rees2001
03-04-2008, 09:29
Anyone that watched the Finals at Buckeye probably wondered what happened to 1126 in the last match. They had the same problem we faced this year. A bad Battery. Our Rookies (424) lost a match in the semi-finals that we thought was a wiring problem. It wasn't. As it turned out the wiring was fine it was a bad MK battery. We had 2 blow this year at competition and another 2 go down in the pre-season. I was a bit curious when we pulled the battery out of the robot & it gave a full voltage reading. We put it in a robot & tried to run, it drops down to a dead reading. When I was holding the battery I felt a warm spot about 2 inches wide that ran from bottom to top on one side. I talked with some of our electrical people I was told that it probably has a bad cell. We have checked out our chargers & they are not the problem. In the previous 7 years we have only had 1 bad battery out of dozens. (some do die over time)
What I want to know is, how many other teams have bad batteries? I would like to contact MK but I would love for some more Ammo before I do.
Al Skierkiewicz
03-04-2008, 09:42
Rees,
You are not the only team who has expeerienced this trouble this year. I invite all teams with battery problems to PM me with details please. I need to know the charger you were using for that battery prior to the defect. About how long it was in service (did you use it for practice and/or how many events), does it show any signs of being dropped (a ding in the side or a rounded corner) and how long does a normal battery last on your robot. Also is there any case deformation (swelling). Inspectors will also be interested in any failures you have at Champs. I will be inspecting and you should be able to find me on the pit floor if you have any problems you would like to show me then. Pictures are also helpful.
Alan Anderson
03-04-2008, 11:17
We have a battery that acts like that. It seems to charge fine, and seems to show a good voltage when not under load, but the voltage drops immediately when used.
We have a good idea of what went wrong with it. This particular battery once started to fall from a table, and was "saved" by someone catching it by the wires.
kborer22
03-04-2008, 12:01
125 experienced the same thing in boston, there werwe 2 matches that i remember that we could not winch our catapult back b/c the battery was toasted, there is nothing more frustrating than that, espctially when the batt has been charting for over an hour!
Mark McLeod
03-04-2008, 12:02
During finals the drive team got a battery from Spare Parts, but it was defective on the field. There's no telling though how it was treated beforehand.
One of our own MK batteries was bad in the finals as well. I'll get more details from the pit crew about when good batteries go bad...
We will also be bench testing our failed battery this evening.
fatjoe3833
03-04-2008, 12:20
During finals the drive team got a battery from Spare Parts, but it was defective on the field. But there's no telling how it was treated beforehand.
One of our own MK batteries was bad in the finals as well. I'll get more details from the pit crew about when good batteries go bad...
We will also be bench testing our failed battery this evening.
Mark, was the second battery from spare parts okay? Maybe there was a problem with the chargers at SBPLI. I saw the spare parts people charging the extra batteries troughout Saturday. Maybe the batteries were abused or mishandled at another regional.
-Joe (Elimnation Match Spare Battery Guy)
Wayne C.
03-04-2008, 12:27
Actually team 25 has found that two of our new MK batteries from this season have failed (in Hawaii). They seem to be taking a charge but they rapidly lose it and are spent well before the round is over. We were attributing it to the fact that for the first time we have the battery mounted sideways and I was assuming that the cells were being jarred from robot impacts.
Normally we mount the cells upright and a battery lasts past a single season. We are ordering a few replacements for the Championships later this month.
If this is a "bad batch" of batteries I would like more info. We charge with the exact same type of chargers the kit has included for the last few years (prior to 2008)
WC :cool:
Al Skierkiewicz
03-04-2008, 12:38
For those of you that measure the battery at full up no load and then it drops under load, what is the measured load terminal voltage? Does it fall by a multiple of 2 volts or does it go down to zero? Please give lot number/date code when you post.
milton1205
03-04-2008, 13:12
Here is a little more info on our battery failures:
1) The two batteries that failed were bought in 2007 and out of the same batch number. They did not come in the 2007 kit of parts.
2) We only used these batteries in competition. (During the build season we use 2006 or earlier batteries.)
3) We use previous years' chargers to charge all batteries.
4) We measured all of our 2007/2008 batteries' impedance under load and found that they were mostly <10 mOhms ( which meets the current spec). The exceptions were the two that failed (about 5 Ohms) and one 2007 battery that was 12 mOhms. Testing was done on fully charged batteries. All of the batteries read >13V after charging and recovered to at least 12.5V after the load test (except one of the failed batteries which read 10.83V).
5) We removed the plastic cover to expose each cell's rubber cap. In the failed batteries these were "dimpled" indicating the battery was probably over heated at some point. The failed batteries also exhibited either a reddish residue or a trace of yellow liquid.
6) The batteries show no indications of heavy impact, and none were dropped or handled by the cables. Also in both of our on-field failures there were no impacts that caused the failure.
7) Our current robot does not draw significantly more current than any previous year's electrical system, and battery voltage after a match is >12.5V. We can probably run two or three matches on a battery before seeing a performance drop, but we have not tried this with any of the 2007/2008 batteries.
Summarizing:
One of the failures was a single cell failure as indicated by the voltage ( and the red discharge near one of the cells). The second failure is probably related to a loss of electrolyte.
At this point we are investigating the chargers, specifically, the charged voltage threshold and the trickle current over long periods. We are also (re)-implementing the battery tracking records ( time in, time out, match used etc.) as we were a little lax this year.
One more note:
In buying replacement batteries, the country of (manufacturing) origin has changed from Vietnam to China. We intend to characterize the new batteries this weekend.
We would appreciate any thoughts you have.
Thanks
Mitch Milton
Team 1126 - Electrical sub-team
sanddrag
03-04-2008, 13:25
We have found that some of our batteries will not charge on the new Schumacher charger. It acts like it is starting the charge cycle them quickly goes to a red fault light. They charge just fine on the old ChargeXpress chargers.
DGrohnke1023
03-04-2008, 13:46
1023 had a battery go bad this year. We charge our competition batteries on the old style chargers (2007 and earlier). We got down to the field and when the match started it read 10.8 volts not under load. It would drop to 5 under load. We attempted to recharge the battery and after the light was solid green we checked the voltage and it only read 10.7 volts. The battery was from 2007 and was used in 2007 build and 2 events, offseason, 2008 build and went bad in the middle of our first event. The battery will no longer hold a charge.
We had a battery act wierd like this on us this year and we marked it bad. I'm not sure when it came from... we aren't really too good about cataloging batteries and all...
However, we didn't catch in on the field, we caught it in the pit. I highly suggest teams own a Load Tester for their batteries... basically it's a box of ceramic resistors with a built-in volt meter and a switch to apply/remove the load from the battery. We briefly test each of our batteries this way before they go to the field to make sure that they perform.
You should be able to get one at most auto parts stores.
-q
Engineer
03-04-2008, 14:33
I like to use a Vector Smart charger (AKA Power on board, AKA Craftsman). It gives a digital display of the charage rate, full charge and error messages if a battery fails to take a charge properly. It performs a three stage charge on the battery too. It identified a bad battery before we had an issue with it. The 2/4/6amp charger is also about the same price as the Speed Charger that comes in the KoP.
MrForbes
03-04-2008, 14:37
Just to keep things interesting, I'll mention that we discovered that the Andersen connectors this year are made differently from past years, and that we could get the power to the robot to go on and off by merely wiggling the Andersen connector with the new batteries, but it would stay working with the old batteries (which have the old connectors).
Jeff Rodriguez
03-04-2008, 14:57
Two of our batteries have issues similar to this.
We put the battery in the robot, switched it on, and nothing happened. The robot didn't go on at all. We disconnected the Anderson connector and connected a different battery without actually moving the first one, switched it on and it was fine.
I think it was the battery, but after reading the thread I now suspect the Anderson connector as well. It has happened to us only a few times and each time, we haven't done a thorough investigation of the problem.
I believe we have a mix of new and old Anderson connectors on the batteries (we taken them off old, dead ones).
Al Skierkiewicz
03-04-2008, 15:08
Mitch,
The spec is 11mOhm nominal so I wouldn't be too worried even up to 15 or 20 mOhm. However 5 ohms is way too high. I know the construction of this battery does make it possible to damage the terminal inside the red/black coating at each terminal. Picking up by the wire is a guaranteed failure.
Brandon Holley
03-04-2008, 15:42
Just to reiterate, team 125 had 2 bad batteries go down on us at the boston regional.
One was from 2007 KOP the other from 2008 KOP. Other than that I dont have the exact details from them, however when put under load (with a load tester) we got a reading around 9 V for both of them.
Brandon, when you use the load tester on an "in working order" battery, what is the "regular" reading you would get?
Tom Bishop
03-04-2008, 17:14
Our 2 batteries from the 2007 KOP act like they have take a charge then when you put them on the robot the voltage immediately drops. I haven't load tested them, but we just don't use them now. They went dead while we were using them on our 2007 bot to practice in the fall. They've been charged on both a NAPA charger and the new Schumaker.
To test the theory of a bad batch of batteries, here is the lot number for the bad batteries that SparX had.
Lot Number: 061009D
We dropped one of our batteries from last year. The little plastic strip on the top of the battery came loose, giving access to the cells. Later, that battery tipped over somewhere, and the acid poured out of it. When this happened, it still has 12V on the posts, but when we tried to move, it would reset the controller. Obviously, if there is a problem with a battery, then its either the posts or one or more of the cells.
EricVanWyk
03-04-2008, 19:51
We dropped one of our batteries from last year. The little plastic strip on the top of the battery came loose, giving access to the cells. Later, that battery tipped over somewhere, and the acid poured out of it. When this happened, it still has 12V on the posts, but when we tried to move, it would reset the controller. Obviously, if there is a problem with a battery, then its either the posts or one or more of the cells.
Please do not continue to use a battery that has leaked. Please.
Team 104 had battery problems at the NJ regional. The 2 2008 and 1 2007 batteries failed on Thurs. They would charge but would be down half way through a match. Any battery that was charged on the 2008 charger failed. We made it through the regional on a 2006, 2007 battery and the 2006 and 2007 chargers. We are sure the common mode of failure was the 2008 charger.
Please do not continue to use a battery that has leaked. Please.
We didn't realize that it leaked until we pulled it off the robot and I tried to figure out why it wasn't working. I knew the plastic plate on the top was loose, but I did not know the black rubber plug had come lose. I'm not sure if it leaked or it evaporated while charging. We disposed of the battery properly, and it is now in the battery graveyard.
At the boston regional we had some trouble with our charger. We would plug in one of the batts to charge, and come back later and the red "Check" light would be on. Unplugging the battery from the charger and charger from the wall solved the problem, but it did this at least twice. This caused trouble when we thought the batteries were charging, but were just sitting instead. We have the 2008 KOP charger and batteries.
Team 104 had battery problems at the NJ regional. The 2 2008 and 1 2007 batteries failed on Thurs. They would charge but would be down half way through a match. Any battery that was charged on the 2008 charger failed. We made it through the regional on a 2006, 2007 battery and the 2006 and 2007 chargers. We are sure the common mode of failure was the 2008 charger.
We had 2 of our 2007's fail. We did not use the 2008 charger, our batter cart has 6 of the old style chargers on it.
BTW 2006 batteries were illegal for competition this year.
MrForbes
03-04-2008, 21:29
Team 104 had battery problems at the NJ regional. The 2 2008 and 1 2007 batteries failed on Thurs. They would charge but would be down half way through a match. Any battery that was charged on the 2008 charger failed. We made it through the regional on a 2006, 2007 battery and the 2006 and 2007 chargers. We are sure the common mode of failure was the 2008 charger.
THe new chargers are a bit tricky, you have to make sure the voltage is set correctly, and current is set correctly after you connect the battery.
Chris Fortmeyer
03-04-2008, 21:50
Mark, was the second battery from spare parts okay? Maybe there was a problem with the chargers at SBPLI. I saw the spare parts people charging the extra batteries troughout Saturday. Maybe the batteries were abused or mishandled at another regional.
-Joe (Elimnation Match Spare Battery Guy)
Joe,
I am actually the member of the drive team that noticed the bad battery from Spare Parts. The robot was continually resetting and not staying on long enough to even get a voltage reading on it. The second battery from Spare Parts seemed to work fine, even though it was not fully charged at the beginning of the match.
We were not the only team having battery problems. Yes we were aware of the need to set the battery charger. I can't prove the 2008 charger was the problem. All I can say is that the batteries that were cycled on the 2008 charger failed. The ones which were not worked fine. As to the 2006 battery legality. We used what we had. We were not the only ones.
Just to keep things interesting, I'll mention that we discovered that the Andersen connectors this year are made differently from past years, and that we could get the power to the robot to go on and off by merely wiggling the Andersen connector with the new batteries, but it would stay working with the old batteries (which have the old connectors).
What was different about the connector ? Were the pins inserted into the shell correctly ? I'd like to see this thing ? Going to Atlanta ?
fatjoe3833
03-04-2008, 22:28
This battery issue seems to be pretty common. Maybe FIRST received a bad batch for the KOP? Has anyone informed FIRST?
MrForbes
03-04-2008, 22:59
What was different about the connector ? Were the pins inserted into the shell correctly ? I'd like to see this thing ? Going to Atlanta ?
We're not going to Atlanta, but when you get a chance, look at the contacts in the connectors, see for yourself. As far as I know they were all pre-terminated connectors. I don't have access to the batteries and chargers and robots right now, or I'd take some pictures.
I think Al S. is looking into this. I doubt it's the cause of all the battery problems, but we did notice a definite difference between the performance of the older and newer connectors when we were wiggling wires around at the AZ regional (when we also had another serious wiring problem).
We have 8 of the new style battery's. This year 2 of them went bad with the same symptoms as everyone else has, the voltage drops to nothing when a load is applied. We have 2 other that are down about 20% when load tested and we won't use them unless we absolutely have to. We are using the Excide chargers from prior years. The new charger is still sitting in the box.
i remember in Vegas team 4 asked me if i could check out there batts. for the sam reason they had a full charge but the battery would not work for more than a minute maybe that could have been why.....
We have not had any voltage problems with the new batteries, but have lost 6 batteries due to swelling this season. We believe that the swelling problem is due to our bank charger which we have now discontinued use with, prior to the swelling we had noticed that it was charging hot.
We did have a voltage problem in 2006. The battery in question read 13.5+ volts off the charger where it had been for an hour. But once the match started it failed to even move the robot and read something like 7 volts.
Al Skierkiewicz
04-04-2008, 17:37
We have not had any voltage problems with the new batteries, but have lost 6 batteries due to swelling this season. We believe that the swelling problem is due to our bank charger which we have now discontinued use with, prior to the swelling we had noticed that it was charging hot.
We did have a voltage problem in 2006. The battery in question read 13.5+ volts off the charger where it had been for an hour. But once the match started it failed to even move the robot and read something like 7 volts.
Colin,
Can you give me manufacturer and model number or a link to the charger? Yes I am still working toget a handle on these issues and I need hard data on battery, charger used, approximate life span (#of matches).
For all, remember that these batteries have a specified life span of about 400 charge/discharge cycles. When high current in charge or discharge is used, then that life is severely decreased. Repeated 80% discharge can lower this to almost 200 cycles. This is also affected by charging a warm/hot battery.
MrForbes
04-04-2008, 19:33
How is battery life affected by sitting for a long period, discharged? I know this kills car batteries....
How is battery life affected by sitting for a long period, discharged? I know this kills car batteries....
Kill these batteries too. They need charging periodically. I think it is at least every three months.
Everyone,
Please remember to recycle these dead batteries !!
Colin,
Can you give me manufacturer and model number or a link to the charger? Yes I am still working toget a handle on these issues and I need hard data on battery, charger used, approximate life span (#of matches).
The charger is an AutoMeter Professional BusPro-600S (http://www.batterystuff.com/battery-chargers/12-volt/multi-bank/BusPro-600s.html). 6 station, 5 amp per station smart charger.
The 6 in question probably had 40 or so charge cycles, tops, on them.
The charger had one station in question which had been charging slightly warm since Atlanta 07. About a month and a half ago we noticed that it was charging extremely hot, saw one very swelled battery, and 5 more that had minor swelling.
We immediately discontinued use of the banked charger and went back to the vintage kit chargers (Xenotronix HPX-60) and have not noticed anymore issues.
Leaving Lead Acids discharged leads to a process called
Sulfation effectively messing up the Batteries ability to charge
fully the next time.
We have been wondering about our performance lateley also.
Haven't had any burn up or lose a cell yet.
Al Skierkiewicz
04-04-2008, 21:56
The battery brochure for this battery can be found here...http://www.mkbattery.com/images/ss.pdf
It implies that float charging can keep these batteries going for a while. With IRI we end up charging batteries during the summer for practice. Then we don't really start using them for several months and do not leave them on float. Over the years, we have not noticed any serious deterioration. We use a CBA-II from West Mountain Radio to track batteries and compare them from one year to another. We have generally been getting usable service life for practice of three years or more.
The new charger is a little wierd.
If you pull the charger off a battery that has reached full charge and immediately connect to a battery that needs charging the charger goes stupid and does nothing.
If you reboot disconnect and reconnect and/or reboot the charger then you will be back in business.
You really have to pay attention to see if it is really charging.
eugenebrooks
05-04-2008, 00:01
You might want to check each bank of the charger to confirm
that it is executing its three stage program properly, and that
the parameters are reasonably close to what MK specifies.
The suggested charge rate is C/5 amps, about 3.6 amps.
Yes, FIRST specifies the limit at 6 amps and this is reasonable
for our usage of the batteries.
The suggested absorption voltage is 2.40 to 2.45 volts per cell.
The suggested float voltage is 2.25 to 2.35 volts per cell.
There are 6 cells in the battery we use.
The last parameter is the length of time the charger sits
at the absorption voltage before kicking down to float.
The typical standard for this is 4 hours, and this is fine
for a deeply cycled battery, but is not good for a battery
that has been shallow discharged.
The Interacter charger, www.batteryweb.com,
implements timing on the absorption cycle that is proportional
to the length of time spent bulk charging. This is desired
behavior for batteries that are shallow discharged and
rotated to the charger every match, as they should be.
There is no need to trickle charge these batteries for long
periods, and if you do, the survival of the battery depends
critically on the charge voltage. The self discharge rate is
3% per month. All you need to do is store them fully charged
in a cool dry place for the summer, and then give them an
overnight charge when school starts again.
Below is a link to MK's technical manual for their GEL and AGM
batteries, the one we use is an AGM battery.
http://www.mkbattery.com/images/VRLA_TechManual.pdf
Eugene
The charger is an AutoMeter Professional BusPro-600S (http://www.batterystuff.com/battery-chargers/12-volt/multi-bank/BusPro-600s.html). 6 station, 5 amp per station smart charger.
The 6 in question probably had 40 or so charge cycles, tops, on them.
The charger had one station in question which had been charging slightly warm since Atlanta 07. About a month and a half ago we noticed that it was charging extremely hot, saw one very swelled battery, and 5 more that had minor swelling.
We immediately discontinued use of the banked charger and went back to the vintage kit chargers (Xenotronix HPX-60) and have not noticed anymore issues.
We think we had one battery fail this year as well. We will be testing this again in a couple weeks. We left this battery at home so as not to get it confused and put in the robot.
Please see the attached battery testing we did between the 2006-2007 seasons. Please keep in mind the data presented is based on the old Exide batteries; however, I imagine the new MK batteries will respond in a similar way. We use this in the pit to estimate when a battery will be fully charged based on the charging voltage. If you have any questions, we are happy to answer them.
About the two chargers teams are using: The old charger with the single LED was a pain to use until we understood them. When we tested the batteries we had a current meter in series with the charger and battery to see what the charger was doing during the change in color from amber, to green, to blinking. Amber means the battery is charging. As you can see from the graph as the voltage goes up, the charging current goes down. A solid green light means the battery is charged. This occurs at 14.2 vdc like clockwork. The blinking light back to amber to green means the charger has entered a trickle charge mode. You can see this happen on the current meter as the meter will momentarily show current then go back to zero. The blinking coincides with the momentary current shown on the meter.
The new charger is better since it shows the percentage of charge. It is a little quirky on startup and you do have to make sure to hit the current button twice to get to 6 amps and if the red light is lit unplug the charger and plug it back in. By the way, you can also see from the graphs, no charger is actually applying 6 amps to any battery.
Other tips we have learned the hard way:
1. Put Anderson connectors on your battery charger leads. This prevents arc welding in the pits and gets you a 100% good connection every time. Think we have post on this through my handle.
2. Make your own battery cables. We have a post on this you can find, too. This tip has eliminated battery cable problems for us.
3. Carry batteries by the battery, not the cables. Take care of the cables, also.
4. Be nice to batteries and treat them like a laptop or your favorite tool.
5. Check to make sure the spring that clicks onto the pin in the Anderson connector is engaged. We found one had slid off the spring and not making full contact with its mate on the robot end of the Anderson connector. To fix this, simply push or poll the cable until you hear or feel the click of the pin snapping back onto the flat spring.
6. Clean any corrosion from the battery posts or cables and make sure everything is tight.
7. Buy a load tester. We got a cheap one at Harbor Freight Tools for about $20. Don't forget to use a DMM to measure battery voltage.
Feel free to use our battery information or share with other teams as you wish.
Al Skierkiewicz
05-04-2008, 09:47
Tom,
I looked over your data and it is pretty much what you should expect to see. There are a few issues in the data. Your calculated battery resistance is flawed since it does not take into account the output impedance of the charger. The actual resistance goes down as the battery charges and is normally around 11 mOhms. It is normal for the current to go down as the voltage goes up simply because of the difference in charge voltage compared to battery terminal voltage. It is quite common for lead acid batteries to be charged with a constant voltage style charger. With that type of charger, the terminal voltage is low when the charge current is high. It rises as the battery becomes charged because lead acid battery terminal voltage rises with charging. As that is the case the only way to get the battery to take any current during charge is to force the charger to a higher voltage than the battery. Another charachteristic of lead acid cells is that when they reach full charge, any additional current forced into the battery is given up as heat. Since the charger is capable of a higher voltage than the battery, this will be the case unless the charger is smart enough to turn off when it senses the battery is at full charge. I am guessing the time scale is reversed in your graphs as the graphs represent typical charge and terminal voltage for these batteries. Nice work and it represents quite a bit of time commitment to bring this data to the group. Note that there is also a difference in starting current and this likely due to the different discharge conditions on the batteries you were testing. If I can figure a way to include this in my electrical presentation, can I use some of your data?
What may be at issue here is the difference between gel cell technology and AGM which is slightly different construction but uses the same chemistry. The suggested max charge current on the MK sheet for our battery 5.4 amps. The supplied charger is designed to output up to 6 amps. I wouldn't think that would be a problem but time will tell. I have given the MK rep all the data on the chargers teams were given over the past few years. He has not indicated a problem yet but others are still investigating the issue.
Thanks, Al
You are right; I did not take into account the impedance of the charger. We were simply looking for a way to understand what the battery and charger were doing and be able to explain to the kids how to use the chargers. Yes, the time base is reversed because we wanted to know based on the charging voltage how long it might be until a battery would be charged enough to use in a match if we got into a situation like the championship rounds, where batteries may be needed quickly.
Here is how we tested each battery:
1. We put together 5, 200 mA, 12 vdc bulbs in parallel to equal a 1 amp load.
2. Attached the load to a battery until the load voltage dropped to 10 vdc.
3. Attached the battery charger to a battery with 1 DMM in series to measure the charging current and 1 DMM across the battery to measure the charging voltage.
4. We recorded the voltage and current readings every 10 minutes.
5. Enter the data into Excel. Each test took about 4 hours, so be patient.
Why I thought this was a valid test is the repeatability of the data. Look at the last graph where all 6 batteries just about end up right on top of one another. This validated for me, anyway, we had a new tool to use, share, and learn something from. Best part is it seems to work close enough as we have used this at three regional’s now and the kids are using it and are successful with it!
Thanks for the feedback. Yes, feel free to use the data for any purpose. We like to help where we can.
Please remember the data is based on the former Exide batteries, not the new MK brand.
Hate to bring up an old thread but...
Last year we had nothing but trouble with the batteries. One by one they all failed until we were left with one good battery and that was from 2007.
I just got done running the six new batteries we purchased this year with our CBAII in preparation for IRI and they all still check out as good as they were new.
What are other teams experiences? Was the low friction less hard contact game responsible for not shorting out batteries or are these just a better batch.
Thoughts?
ATannahill
30-07-2009, 13:05
We only had problems with one battery all season. A battery leaked acid during the minnesota regional. We had no problem with batteries shorting out or dropping charge.
gorrilla
30-07-2009, 13:57
we dropped one of our 08' batteries during a demo this year, It dident crack or leak or anything, But it no longer holds a charge...
eugenebrooks
02-08-2009, 12:37
We load test our batteries at 20A, with a cutoff voltage of 11 volts. It is easy to build a load tester using some high power resistors, a fan, some relays, a resistor divider for voltage sense, and that aging EDU controller you probably have laying around. The cutoff voltage is high to avoid wear and tear on the battery from the load testing. We record the number of seconds that the battery remains above 11 volts with the load applied. We also use a 5 bank three stage charger and don't fall into a situation where a battery is used for two matches before charging. We do note good years, and bad years, for batteries from the load testing performance. The capacity can vary by 20% or more, but we have never had a battery fail during a competition event.
Eugene
Al Skierkiewicz
03-08-2009, 07:53
Sam,
I didn't see this post until this morning or we could have talked at IRI. We set the CBA for 7.5 amps and 8 volts terminal voltage (end) to simulate the manufacturer's specs and get a good amp hour calculation. Are you keeping your sweeps so you can compare the same battery over a period of time and overlay them? I have many teams that claim bad batteries, but most when they show them to me, have obvious external damage, indicating rough handling.
I cannot stress enough, do not lift or carry by the wires, do not carry with one hand and do not drop into the robot or onto to the floor in the heat of battle. The terminals are soldered internally (no other mechanical connection) and are not designed to handle the full weight of the battery. Lifting or carrying by the wires is a death sentence and it may cause injury if the terminal fails while you are carrying the battery. A battery that has been handled by the wires will show some opening between the terminal and the red or black sealant due to the movement of the terminal. Two hands please for safety sake. These batteries are smooth and heavy, one hand is not enough even for a big guy like me. Dropping the battery can force two plates together causing a short or will cause fractures in the plates and connecting bars causing reduced capacity or failure with temperature.
Al Skierkiewicz
03-08-2009, 08:00
I just received word from West Mountain Radio that they have a new tester, the CBA III available in August for $149. It will do up to 40 amp testing.
http://www.westmountainradio.com/CBA.htm
Sam,
I didn't see this post until this morning or we could have talked at IRI. We set the CBA for 7.5 amps and 8 volts terminal voltage (end) to simulate the manufacturer's specs and get a good amp hour calculation. Are you keeping your sweeps so you can compare the same battery over a period of time and overlay them? I have many teams that claim bad batteries, but most when they show them to me, have obvious external damage, indicating rough handling.
I cannot stress enough, do not lift or carry by the wires, do not carry with one hand and do not drop into the robot or onto to the floor in the heat of battle. The terminals are soldered internally (no other mechanical connection) and are not designed to handle the full weight of the battery. Lifting or carrying by the wires is a death sentence and it may cause injury if the terminal fails while you are carrying the battery. A battery that has been handled by the wires will show some opening between the terminal and the red or black sealant due to the movement of the terminal. Two hands please for safety sake. These batteries are smooth and heavy, one hand is not enough even for a big guy like me. Dropping the battery can force two plates together causing a short or will cause fractures in the plates and connecting bars causing reduced capacity or failure with temperature.
I should have asked you when we talked Saturday. We are very careful when handling the batteries and I do save the tests from our batteries.
It just seamed like last year was a bad year for batteries. We never had problems like we did last year. Of the six from this year 5 are just as good, or better than when they were new and the 6th is only slightly weaker and still very usable.
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