ToubleShooting Suzanne's Balancer

[HELModels]

I built two of Suzanne's balancers and put them side-by-side on a copper clad board. Hacked my way through the initial electronic learning curve and then fiddled and fiddled and got them adjusted using some trial and error. Fantastic. Worked as designed.

Then disaster struck. The + and - Bat wires of my charger started to fray and wire fragments started touching until enough of them shorted (moved the charger from its usual location)and completely puffed out my lipo. This also affected one of the balancers because it wont come on regardless of setting unless the + wire is connected last. This is definately not normal, but where is the problem? When the + wire is connected last, the LED stays lit regardless of voltage applied. The other balancer does not act this way.

This balancer uses a MAX921 and an enhancement(normally off?) MOSFET. I realize MOSFETS are delicate and easily damaged by ESD, but if it is damaged would it turn on at all? Could the shorted out charger Bat leads have caused overvoltage in the MAX921? One cell of the damaged lipo was severely bloated, while the other still holds some juice.

[HELModels]

Well, now both balancers are fritzed:confused: :mad:

One worked last night, this morning neither works.

Who is this phantom? Is it the feral cat sticking her ESD charged nose in the circuit?

[Chippie]

ES,

I share your disappointment, but dont despair.......for a complete novice you have really made achievements in building such a project.


Now my advice would be a complete rebuild from scratch assuming the pcbs are ok....there's no point in taking chances re-using components from a suspect project, especially one where it involves Lipo's....besides using new components should guarantee success, after all it did work before the wire incident.


Take stock from your mistakes, learn and move on, thats what its all about...if its any consolation, I fried my Super nova charger and a 4 cell AA receiver pack when they were conected to my newly built pc based 8 amp power supply, I caught a whisker of wire against the case (from the +ve side of the output!) shorting the output briefly and.....pooooffff it was no more...:D

I put it down to experience ordered new fets for the S-N and repaired it.

good luck :D

[HELModels]

Right you are, chippie! The feral beast is no longer a suspect. She enjoyed the LED's.

I replaced the comparator/MAX921 and the one that was working right last night works again. I knew the 2 extras would come in handy. I'll have to wait for the FETs. The balancer that acted strangely, still acts strange, but different now. The LED stays On and doesnt need any unusual tricks or prodding to go on - that is still not how it should work, but I think new FETs should do it.

I also built the voltage regulator(uses slightly different Regulator and different capacitor values) she suggested as a voltage source. I completed that Just in Time to short the charger and the lipo.

[HELModels]

Well, the cats are definately not to blame, feral or tame.

The frayed wires on the charger? That still could be The Phantom.
Is most likely a manufacturing/design defect. Of course, I will move the charger around. who would expect less from a field charger?

Replaced both the comparators and one balancer worked. The other also worked, but oddly. Checked for shorts. Checked for shorts. Checked for shorts. didnt find any, but found an Open.

The 3.3M resistor to the FET was not connected to the comparator output, causing the LED to turn on continuously - I think 3.3M biases the FET.
This explains the shift in circuit behaviour from strange to almost right when the MAX921 was swapped out.

I'd move on to another project, but it seems The Phantom is what I'm troubleshooting and will be present in any project.:mad: