Re: Better Battaries for Driver Pratice
 

Float charging and trickle charging are not the same thing.

You can leave a lead-acid battery on a float charger.

Re: Better Battaries for Driver Pratice
 

There are deep discharge gell cell batteries in the typical lawn tractor size that will give allot more power for a little larger case. Long run times can be dangerous with thermal issues. Sears sells a wheel chair battery that is not bad. I use the same case size but much more power battery for my power lift equipment. I'm paying 160$ for the good ones.

Re: Better Battaries for Driver Pratice
 

Oh wow. I never knew that there was a difference between the two. The difference is very minimal.
So basically a float charger is the "smart" version of a "dumb" trickle charger. Cool.

Re: Better Battaries for Driver Pratice
 

akoscielski3, how many batteries have you blown? While charging them at 15A may increase the risk of blowing them out if you haven't blown any it's probably a negligible risk. Getting new chargers is so far my favorite solution.

True, however while we can work around the problem I'd rather find a fix.

The only reason I would hesitate to do that is the first 2-3 minutes of battery life are noticeably the best. The robot moves faster and it's closer to competition settings (2.25 minutes of a fresh battery). I don't like loosing that cream of the crop battery time but it's better then nothing.

Re: Better Battaries for Driver Pratice
 

Taking 3 hours to recharge a battery seems way too long. Also, what voltage are you running your batteries down to?

We practice 5 days a week for an average of 4 hours a day. When we practice we try to never let the battery drop below 12.0V at idle. This is usually 1-3 matches depending on the robot and how much power draw their is during a match. By the time we've gone through all 6 batteries, the first battery is ready to go again. We've also found that by doing this we can actually recondition the battery and keep all of the batteries between 12.8 and 13.1V at idle.

Re: Better Battaries for Driver Pratice
 

Depends on the perspective I guess. To a lead-acid battery it's not minimal, it can be the difference between life and death.

Re: Better Battaries for Driver Pratice
 

A lot of the damage to these batteries comes from charging them at high temperature. More current makes a battery hotter. If you're force-feeding a FRC-legal battery with 15 amps for more than a few seconds, you're abusing it. It'll most likely treat you badly in return.

Re: Better Battaries for Driver Pratice
 

We have never blown a battery. I dont believe that we have charged on 15A before. :P

Re: Better Batteries for Driver Practice
 

He's a liar, I wouldn't believe a word he says!
The batteries remain competition-legal regardless of the charge rate. The chargers are not competition-legal, and are bad for the batteries (see Alan Anderson's comment above)

OK, so the problem is that the batteries are going dead.

The solution is the same as with my laptop computer: When the battery's dead, I plug it in and run off the wall outlet. (Translation: Find a 100A 12 V power supply and run heavy cables to the robot during practice). :p

(Oh, and Max: Battaries? Sheesh!)

Re: Better Battaries for Driver Pratice
 

There is another thread on this elsewhere, but the MFRs recommended maximum charger rate is a little under 6 amps for these batteries. You can do higher at your own peril.

Re: Better Batteries for Driver Practice
 

How are the chargers not competition legal ??

Re: Better Battaries for Driver Pratice
 

you might want to reduce your driving time a bit to allow all of the motors to cool and be sure you don't damage anything. Depending on which motors you are using and what kind of loads they are seeing, you may be generating a lot of heat.

we are using window motors for our lift arm, and even with a gas assist on the lift we limit ourselves to about 8 - 10 minutes of practice time before letting everything cool.

Re: Better Batteries for Driver Practice
 

I do not want to be near a battery that is being over-charged, and I am glad they do not allow this unsafe practice at competition.

Re: Better Battaries for Driver Pratice
 

haha. I keep telling everyone on our drive team and anyone who is with us that we need to allow the motors and other electronics to cool. But unsurprisingly no one listens. When we did our driver practice last Saturday, after about 6 batteries i smelled something weird. it almost smelled like burning electronics. But there was no magic smoke. so i went to feel the motors to see how warm they were, and almost burned my fingers. i told everyone that we needed a 15 min break to let everything cool. (which we did) After the break i could see a noticeable increase in performance.
Also we run super shifters with 2 Cims. We drive our robot around in high gear and when we hit the shift button we shift into the lower gear for more precise maneuvering.

If anyone with a good amount of knowledge in electric R/C's knows that when you start heating up your motor(s) they will degrade in performance. Also high mAh batteries will start to heat up they will start provide less voltage and your truck/car will start to go (slightly) slower.

Re: Better Battaries for Driver Pratice
 

OK,
Let's get some info straight here and in one place.
1. Our batteries are specified by the manufacturer to be charged at 6 amps or less. Battery life can be significantly increased when charged at 1/10 C or about 2 amps.
2. Life is significantly reduced by heavy loads like an FRC robot drawing currents in excess of 200 amps over a two minute match.
3. Charging at high current on our batteries causes internal heating and the possibility of out-gassing and case failure if the vents do not operate.
4. Our batteries are AGM types and the plates within the cells are not as robust as older technology lead-acid batteries.
5. Excessive heat within the battery causes the plates to deform, leading to internal shorts and a variety of other issues leading to lower battery life.
6. Hot batteries during charge can fool many/most smart chargers into producing damaging voltage/current during the charge cycle.
7. AGM batteries are nothing like NiMH, NiCd, LiPO, Li ION or other types and each requires a specific type of charger. Do not mix chargers and battery types.

Now on to the problem...
You can use a larger battery, the marine type for example. It must be a 12 volt battery of course. The motor heating encountered should be relatively the same with any size battery you choose. If you are interested more in practice then in demo, I would suggest that you stick with the FRC robot batteries for a variety of reasons. One is that the larger battery will be much heavier and while practicing, you will be over compensating for the added weight. Also, the larger battery will be able to better supply current to your motors giving you performance that will not exist in competition. If your robot draws a lot of current then the larger battery will also lure you into a false confidence that the battery will continue to supply enough voltage to prevent the systems from shutting down. Remember that the Crio monitors the battery voltage and inhibits all output when the battery falls below 5.5 volts at terminal voltage. The regulated supplies in the PD fail at about 4.5 volts which cause both Crio and radio reboots. If you want real world practice you need to keep real world conditions.