Batteries

[Der Sichelmann]

Our team did a 16 amp battery test. A 2005 battery went down to 10 volts in 21 minutes. The other batteries we tested took at least 40 minutes. One of our 2005 batteries is of poor quality.

[kjohnson]

Originally Posted by Der Sichelmann

Our team did a 16 amp battery test. A 2005 battery went down to 10 volts in 21 minutes. The other batteries we tested took at least 40 minutes. One of our 2005 batteries is of poor quality.

Were you just stating this for everyone to know or did you have questions about what was happening?

[Elgin Clock]

I'm a little confused. That does not look like an Exide-18-12 official FIRST approved (re: only Brand and Model number battery you can use in 2005) in your picture.

Explanation?

[Der Sichelmann]

Originally Posted by Elgin Clock

I'm a little confused. That does not look like an Exide-18-12 official FIRST approved (re: only Brand and Model number battery you can use in 2005) in your picture.

Explanation?

That is a practice battery we tested today. The Exide batteries were tested last night and are currently on charge.

[Der Sichelmann]

Originally Posted by nukemknight

Were you just stating this for everyone to know or did you have questions about what was happening?

Just an observation. It might be a good idea to test batteries. This started as a comparison between 2004 batteris and 2005 ones and we found a bad 2005.

[Elgin Clock]

Originally Posted by Der Sichelmann

That is a practice battery. The approved Exide batteries are currently charging.

Ok, gotcha.. lol I thought you were referring to the pic as "this is the one we tested".

Sorry about that.. Didn't mean anything by it. Forgive me?

[Der Sichelmann]

yea. Someone said to switch batteries but we took the pic anyway.

[DarkJedi613]

If anyone is curious what we did to test them - we built a circuit that had a load on it and was connected to the battery (and two large muffin fans to cool it all off) then timed how long it took the battery to drop to 10v.

[Max Lobovsky]

It looks like you used some sort of large resistor. In that case, you were not drawing exactly 16 amps the whole time. Because you only measured down to 10V, it is probably close enough, but I just wanted to point it out.

[DarkJedi613]

Yeah it was a resister, not sure what its rating was though. Why wouldn't it be pulling 16 amps all the time though?

And we actually timed it a little past 10v, but the only time amount we cared for was 10v.

[Edit: Hmm...I didn't really mean to make it sound "snappy", I just don't understand why it wouldn't do that.]

[Max Lobovsky]

V=IR. If V goes down, and R is constant, I must go down.

[DarkJedi613]

Originally Posted by Max Lobovsky

V=IR. If V goes down, and R is constant, I must go down.

Oh, that clears it up. Thanks.

[Al Skierkiewicz]

Originally Posted by Der Sichelmann

Our team did a 16 amp battery test. A 2005 battery went down to 10 volts in 21 minutes. The other batteries we tested took at least 40 minutes. One of our 2005 batteries is of poor quality.

This is pretty unusual for batteries to be bad out of the box. Although I can't open the file (I will try from work tomorrow) it would appear that the battery might not have fully charged. This can occur when there is a high resistance connection to the charger. I would double check all electrical connections, charge it up and try it again.
It is interesting to note here that an 18 AH battery cannot supply 18 amps for one hour. The spec sheet lists the test parameters and the final test voltage vs. time but it should be noted that the battery changes output with temperature as well.

[DarkJedi613]

Originally Posted by Al Skierkiewicz

This is pretty unusual for batteries to be bad out of the box. Although I can't open the file (I will try from work tomorrow) it would appear that the battery might not have fully charged. This can occur when there is a high resistance connection to the charger. I would double check all electrical connections, charge it up and try it again.
It is interesting to note here that an 18 AH battery cannot supply 18 amps for one hour. The spec sheet lists the test parameters and the final test voltage vs. time but it should be noted that the battery changes output with temperature as well.

We're charging it up again and will check tomorrow night. It was definitly fully charged (left over night), I'm not sure about the connections though. I'll check it tomorrow before we test it.

[eugenebrooks]

Originally Posted by Al Skierkiewicz

This is pretty unusual for batteries to be bad out of the box. Although I can't open the file (I will try from work tomorrow) it would appear that the battery might not have fully charged. This can occur when there is a high resistance connection to the charger. I would double check all electrical connections, charge it up and try it again.
It is interesting to note here that an 18 AH battery cannot supply 18 amps for one hour. The spec sheet lists the test parameters and the final test voltage vs. time but it should be noted that the battery changes output with temperature as well.

We finally got our current regulated capacity tester running, and have tested two ES-18 batteries from 2004, and the two EX-18 batteries that arrived in the KOP for 2005. Given a constant load current of 20 amps, and a cutoff voltage of 11 volts, the two 2004 batteries lasted 32 minutes, while the two 2005 batteries lasted 22 minutes.

The capacity of the EX-18 batteries does appear to be 50% lower.
If your robot will have high current draw you need to pay careful
attention to this issue...