We are looking for any information on best practices for a new battery. We discovered that our batteries were not up to par, and ordered some new ones. Is there a “best” procedure to get new batteries for competition. I have seen information on hooking battery up discharge and timing how long it takes to discharge.
We have seen some advice which states we should cycle the batteries a few times before competition usage, but haven’t seen any documentation that this really helps.
My search on CD hasn’t revealed a best practices for new batteries, and we requesting guidance for some more experienced teams.
Is there something about your robot that makes you think there will be a competitive advantage to maximizing battery performance?
We generally build robots that don’t really seem to care too much about it…and we just treat our batteries as well as we can, but don’t do anything special. We keep them in order, and use the next in sequence. We have 6 batteries, and can charge 3 at a time. We also try to not let them drop below about 12. 3 v when in the robot with the robot turned on, but not doing anything, while practicing/testing/programming. When they get below that, it’s time to take it out and charge it. And we do our best to charge them all fully after use. A real battery killer with Lead Acid batteries, is to let them sit discharged for a long time (summer is the big problem, of course).
I suppose there are some teams who need the best battery performance they can get, but ours doesn’t seem to be one of those teams–we haven’t been able to blame battery problems for losing a match, for quite a while.
We really have no experience in this area and don’t know if anything special is required. Just trying to learn.
We did notice in our practice sessions that if our batteries were low that the NEO’s on our elevator didn’t perform as well. We are using NEO’s on our climbing mechanism, and want to make sure tha our batteries are in good condition at end of match.
I think you probably want to pay the most attention to not discharging the batteries too far, and to not letting them sit discharged. Those two things seem to be what causes the most problems with shortening battery life.
Again, don’t let them get below 12v with the robot on and sitting idle, and don’t let them sit for any length of time while discharged–charge them right away after use, and also every month, if possible.
I guess that’s what I was referring to in my first reply. No, you don’t need to do anything special, just charge them fully and use them.
Taken care of, you should be able to get 3-4 years of use from your new batteries. Top teams get all new competition batteries every year, but most of us don’t need that little extra edge. What we do need, is to take good care of our batteries, to get the most out of the money we spent for them. Train students to change the battery often during practice, and to always charge after use, and you should be fine.
“Cycling” a battery - discharging it and recharging it - is what causes batteries to “wear out”, as there are a finite number of cycles any lead-acid battery can withstand. So NO, don’t cycle them unnecessarily. As Mr. Forbes said.
Also as Mr. Forbes said, allowing your battery to remain in a discharged state is a major cause of failure. A fully-charged battery will self-discharge enough to hurt itself in less than 90 days. How long do they sit unattended over summer break?
Why is this so? The chemical reaction Pb+H2SO4 > PbSO4 + H2O is not 100% reversible, something like 99.9%, so every cycle cuts a little. If you let it stay discharged, that PbSO4 crystallizes a bit more effectively, meaning charging can no longer reverse the reaction, and eventually the battery loses capacity.
One last thing: Treat them gently. Dropping, carrying by the wires, excessive vibration, shock, deep and/or fast discharge (unnecessarily) and other abuse also hurts batteries.
There seems to be quite a bit of conflicting information on batteries depending on who you ask. I would suggest that you look at the post “Battery Warning” here on CD that has quite a few good points on not only batteries in general, but in particular, this years batteries.
I had similar questions and after doing testing with our local Interstate Battery Service Center and they confirmed my suspicions that last years batteries were better than this years batteries (as far as useable AH availability). When talking to their lead Engineer in Texas, he told me that the reason for this finding is that a battery will not reach its rated capacity until its been cycled 20 to 30 times.
We normally try to build our bots to maximize effectiveness with minimum battery drain, but the game sometimes dictates something different. We have found that playing defense in this years game causes brownouts. Although there are many ways to minimize these brownouts like creating a larger drop in center wheels when using pneumatic tires or to put duct tape on either front or back tires to minimize drag when turning helps, but battery capacity is still important.
Brownout reports are a great indication of how your robot interacts with your batteries. If they aren’t causing you massive headaches, maybe you shouldn’t worry unless they cause you issues toward the end of a match. It only takes 1 or 2 matches to ruin a season, so I don’t think that it should be taken lightly.
I am hoping to post results after my test equipment arrives on this years Interstate Batteries. I will be doing a baseline and then will do a second graph once we cycle them another 10 to 20 times to see if his explanation is correct. I will also post internal resistance figures as well but on a new battery, I don’t expect many surprises.
I think that one other thing that hasn’t been mentioned, is to get a good charger that will charge your batteries sufficiently without over charging. I think that this would be more of a contributor of premature battery failure other than a manufacturing defect.
I think that one thing is a given, this years Kit Of Parts battery shouldn’t be trusted in competition. I am also hoping to cycle that battery if time permits before we head to Detroit, though I doubt if we’ll bring it with no matter the results.
Did he give you any numbers regarding how much the capacity would change? ie. 5%, 20%, or ???
For most robots built by most teams, my guess is this number is not large enough to be a concern. For some teams it might be, but those teams probably plan to buy all new batteries every year, anyways. For those with limited budgets, we could expect the batteries to perform slightly better the second season, and then fall off the third season, but still provide acceptable performance for several years.
After chatting with Al during the Central Illinois Regional, I took his recommendation and went to West Mountain Radio and a product called a CBA IV. I also have an older Alexander Battery cycler that I am running a few batteries through but it takes quite a bit of time.
For testing internal resistance, I ordered a battery beak from AndyMark. It’s a shame that I couldn’t order it from battery Beak directly but their shipping, in my opinion, is pretty unreasonable.
MrForbes, After your questions, I just called Interstate Battery back and asked him those additional questions… The engineer that I spoke with indicated that the typical increase after 20-30 cycles would go up between 10% to15% depending on the unit. Typical full output current at rated levels, as stamped on the battery, would be somewhere in the range of 250-300 cycles per battery but could go as high as 500 to 600 cycles of “usable power”. I think “usable power” is a rating that would have to be determine by the application and by the individual user.
For team 5690, our theory until this year, was to buy 6 new batteries per year and to use the KOP battery used as a 7th. With our 6 match semi final “Tie-a-thon” at the Iowa regional 2 years ago, we now also bring a few batteries from the previous year. (Although through gracious professionalism), many teams offered their batteries for us to use. Our charger bank will handle 6 batteries at once and with that turn-around, it was tough for the charger to keep up.
We used last years as our build and practice batteries. Depending on our results of the tests, this may alter or change our approach.
Pretty much everything that’s been said here is on track.
On our team, we have a routine we go through with new batteries.
Inspect for any damage, and check the voltage. So far we’ve been lucky, no initial damage, and the voltage has always been above 12.6 as it should be for a new battery.
Next we connectorize them with the SB-50 powerpole connectors.
Then, name them (to keep track of them, and the students like doing that), and put them on a charger.
After charging, and letting them rest for a time we check the Internal resistance with the Beak, all of them were around .015 Ohms, and test on the CBA IV to get a discharge curve at 1.0A. This year with a crop of new Duracells they were all about 17.5 AH +/- .5
We then rinse and repeat so that each is checked twice to verify no problems.
After that, we use them as needed, using new batteries only for competition, and using the 2 year old batteries (we refresh every other year) for practice, etc…
We also check the batteries now and then, or if suspect and not uncommonly find ones that are down to as little as 8 AH of capacity. At that point they are recycled.
General practices we follow are to
Avoid using the battery for practice if it’s below 12.0 VDC at rest (as opposed to driving it around),
Charge after any significant use. We figure that 200-300 cycles is way more than we will ever use so charging often isn’t an issue.
As people have said, treat them kindly, don’t drop, don’t pick up by the wires, don’t charge or use when really hot, let them cool off.
Mostly, keep an eye on them. Mark ones that are suspect. Get a Battery Beak so you can check them often.
Good luck and have fun,
Mike9966, You brought up a point or two that I forgot. It is a great point to mark them with the year that you purchased them and we also label them 1-XX. We have a checklist that we go through religiously to check for loose bolts, damage, belts, wiring connections etc. One important box is the number of the battery last used. This almost always insures a new battery is in for the next match.
In being a robot inspector this year, I would also note that I saw quite a few batteries with loose connectors or bad crimps on the SB-50 Power Pole connectors on the battery side. The lugs are not easily crimped because of the AWG 6 wire and the size of the connector. Yesterday I went to Harbor Freight and purchased a new hydraulic wire crimper (Model 66150) that I plan to try with our team later this week. Once crimped, I plan on soldering them as well to provide an optimal connection. Though it may be overkill, I think that it may be worth the extra few minutes of time.
I had also noticed that we had issues with some of the terminals corroding on last years batteries. With the battery terminals taped, it’s hard to see the health of these connections. Most of the corrosion was found using the hardware that we received when we bought the batteries. We now use 10-32 hex head screws on all of these connections and it allows for better tightening. We also use star washers to provide a better connection.
A lot of “little” things can lead to a big problem. Finding those “Weakest Links” can either insure or eliminate you from having a successful year.
Forgive me if I’m wrong, but doesn’t soldering crimped connections stiffen them to the point where they are more likely to break after repeated bending and fatigue? I think it is mentioned it in this thread:
We bought one this season, it’s excellent.
Do make sure the release valve is fully seated, to get full compression on the crimp.
Don’t be afraid to file off the flashing (flanges) to help it fit into the SB50 connectors better.
Do section the first contact you crimp on a bandsaw. It should look like a solid block of copper. If it’s not, your release valve isn’t fully closed, you don’t have the right jaw, or you need to exchange the tool (happens sometimes at harbor freight).
Don’t worry about soldering afterwards, with a hydraulic tool there are no voids left for solder to fill:
The issue is that the solder wicks up into the wire causing that section of the wire to be very stiff. When the wire is flexed, the strands are bent sharply where the solder ends causing them to fatigue and break. Sometimes, this leads to an intermitent connection that will drive you crazy because the break is not right at the crimp lug but up to an inch away. With smaller wire sizes, I have been able to pull on the wire and cause the two sections of wire to totally separate.
The 6AWG wire will conduct heat away from the lug if you try to solder it. It will be very difficult to get a good solder joint with most irons.
I agree with philso that any time you have braided wire, wicking action takes place. As you solder, it will follow the wire up past the connector and into the pigtail and that’s where problems with bending and breaking occur. There are 2 things that I like to insure when putting the connectors on.
When stripping the insulation back from the wire, measure accurately. Make sure that the insulation hits the top of the connector and also make sure that there isn’t a bunch of wire that protrudes from the bottom or connection side which can interfere with the lug being tightly attached to the battery.
If you do solder the connection, don’t over solder.
I try to solder the very tip of the connector near the ring so that it just attaches the wire to the connector. This assures a good connection and also seals the end of copper wire. I’ve found that there is a lesser chance that the connector will corrode. Too much solder at this connection again will wick up into the wire and give a greater chance of becoming brittle or break as indicated in Al’s annual inspection thread.
As philso indicates, it is very difficult to get this heated because of the shear mass of the connector with the wire attached. I have a larger soldering gun, and as an alternative, have also attached a soldering tip attached to a propane torch which I find works the best. Again, less solder is better than more. We also try to use heat shrink to strengthen the connector and then always insulate the connection of the battery with either heat shrink or tape after connecting it to the battery. (R45)
The bottom line is that everyone has their favorite way, or a way that they are familiar with. What ever works for you, especially if it gives you good results, is fine. The key is that the connection is tight and secure. These are just practices that I have used after being in the utility industry for 35 years and have worked for me in the long run.