[Rain100]

well, I built it yesterday, did all the checks(although my meter doesn't read dc ma) and everything checked out. I had the battery fully charged when I started using it.

I used it for about 4 hours, then charged it overnight. when I started using it this morning, I noticed the battery was dead, so I opened it up, and the battery was much expanded, and acid had leaked.

I really don't know what to do

 

[cobaltmute]

What type of battery? The Mini^3 needs a NiMH.

 

[Rain100]

It was a 250mah tenergy nimh

 

[Rain100]

does the mini^3 have a charging cut-off at all?

 

[cobaltmute]

From amb's site:

Quote:

The charging circuit, utilizing a LM317L voltage regulator wired as a constant current source, safely charges the battery at 16mA without risk of damage. A depleted battery can be charged back to capacity overnight.

 

[Rain100]

so I built it wrong?

 

[m1abrams]

What was your measured charging current?

 

[Rain100]

i don't know

I said in the op that my meter doesn't read dc ma

 

[m1abrams]

Quote:

Originally Posted by Rain100 /img/forum/go_quote.gif i don't know I said in the op that my meter doesn't read dc ma

Oh well then I would recommend you get a meter that can read dc ma. They can be had for not much money at all. Check your local radioshack, or possible borrow one.

 

[Rain100]

and what would that tell me? so you're telling me that a multimeter with exact dc ma readings would lead me directly to my problem?

The charging system isn't that complex, if someone could just tell me some things to check.

 

[m1abrams]

Well having a proper meter would make things a lot easier to debug. It would quickly tell us if the problem is with the charging circuit or not. The problem could very well be something else. Can you check to see if the zener diode D4 has failed? If this diode has failed short then that would short circuit the battery causing it to fail in the manner you describe. However overcharging the battery via too much current by having the wrong value for R8 could cause issues too, or have a short in a solder connection.

Measuring the charging current helps pin point where the problem lies.

However I had a somewhat similiar issue with my first Mini3 with the battery melting. In my case I noticed the problem very fast because the battery starting showing case issues and smelling bad right away. My problem was a failed D4 due to me accidentally trying to install the battery backwards for just a short second. This type of accident is probably fairly common so maybe something you did too.

 

[Rain100]

so to test a diode you should get infinity ohms one way and ~0 ohms the other right?

because i used schottky diodes on d2 and d3 and I get infinity for both testing one, and ~0 both ways for the other.

 

[Lifthanger]

could you measure R8 directly in circuit?

edit: did you also test D4? this is the reference diode for the battery charging circuit.

 

[m1abrams]

Also make sure D4 is not installed backwards

 

[Rain100]

r8 is 75 ohms, which should be correct.

d4 tests infinity one way, and changes ohms when I read it the other? It is installed correctly