DIY Solutions to Honda Hybrid Battery Problems (Insight, Civic, IMA)

[Ecky]

"Cell 1" appears to have more capacity, but it isn't a good idea to put a particularly good cell with a bunch of weaker ones, as it will tend to get out of balance with the others.

[S Keith]

Originally Posted by Ecky

"Cell 1" appears to have more capacity, but it isn't a good idea to put a particularly good cell with a bunch of weaker ones, as it will tend to get out of balance with the others.

So, it's your position that "Cell 1" with a capacity of 6058mAh is a ballance risk compared to "Cell 2" with a capacity of 5873mAh?

You realize that's a 3.2% difference?

While your statement in a broad sense is mostly true, it certainly doesn't apply in this situation.

[mvrroking]

Originally Posted by S Keith

So, it's your position that "Cell 1" with a capacity of 6058mAh is a ballance risk compared to "Cell 2" with a capacity of 5873mAh?

You realize that's a 3.2% difference?

While your statement in a broad sense is mostly true, it certainly doesn't apply in this situation.

Excuse my language I meant the sticks, the battery sticks is what I've been cycling in order to find the faulty/low capacity one. What percentage diff would cause an imbalance if there is such a thing in these packs. I am aware that the center sticks tend to not dissipate heat well damaging their longevity, so I'm looking forward to replacing those.

[Ecky]

I may be ignorant, but I would imagine the ratio of charge to discharge is probably the most important factor (as an indicator of internal resistance?), not necessarily the capacity difference itself. As for picking a percent, I'm also interested in S Keith's opinion.

[S Keith]

Originally Posted by mvrroking

Excuse my language I meant the sticks, the battery sticks is what I've been cycling in order to find the faulty/low capacity one. What percentage diff would cause an imbalance if there is such a thing in these packs. I am aware that the center sticks tend to not dissipate heat well damaging their longevity, so I'm looking forward to replacing those.

There isn't a simple answer to your question. Too many variables. In some cases, a very large deviation can be tolerated. In other cases, a very small deviation is unacceptable.

You have yet to provide any meaningful data upon which a decision can be based. You have provided capacity values under very low current (5W or 10W max power, meaning about 0.8 or 1.4A, respectively. For sticks that will be called upon to charge at 50A and discharge at 100A, your tests have no meaning.

There's also the issue of DECREASING capacities with cycling. That indicates one or more of the following:

1. Sticks are bad
2. Stick capacity will not benefit from cycling
3. You are not cooling the sticks, and each cycle is terminating early because the stick is getting hotter.

Since I suspect you're going to insist on hammering your scrotum with a pickaxe, here's some guidance:

1. Start a google sheet or something to record your data.
2. Conduct ONE charge/discharge cycle with 20 minute wait. Charge at the highest current available to you up to 6.5A (5A is typical of most B6 type chargers; 2A is too low). Discharge to 6.0V at the maximum current available. ALWAYS CHARGE WITH COOLING.
3. Record the Charge and discharge capacities reported.
4. Conduct ONE CHARGE of the stick at up to 6.5A.
5. Let the stick rest for 7 days.
6. Record resting voltage.
7. Record internal resistance if the charger supports it (connection quality must be very good - no alligator clips).
8. Conduct ONE DISCHARGE of the stick at maximum current available.
9. Record discharge capacity.
10. Repeat for all 20 sticks.

The above might give some meaningful data.

Honda sticks fail primarily in self-discharge, i.e., one or more more cells in a stick just lose their ability to hold charge. This creates an imbalance at the cell level that quickly causes the pack to code. NOTE that it's not at all uncommon for ALL cells in a stick to suffer from excessive self-discharge.

The misleading thing is that almost all Honda sticks will cycle up to what appears to be a very good capacity; however, their inability to retain a charge means they're useless.

[S Keith]

Originally Posted by Ecky

I may be ignorant, but I would imagine the ratio of charge to discharge is probably the most important factor (as an indicator of internal resistance?), not necessarily the capacity difference itself. As for picking a percent, I'm also interested in S Keith's opinion.

Your speculation is incorrect. The ratio of the two has almost nothing to do with internal resistance and is more dependent on connection quality and the charging algorithm. While one can argue since the same charger is being used on the same sticks, then that shouldn't matter. That's not correct. The connection quality of these chargers is terrible. Most 4mm bullet connectors and all alligator clips are completely unreliable when looking for consistency in a -dV charge cut off.

This all comes back around to the fact that he's using a toy that's essentially worthless for this exercise.

If one has consistent and reliable connections, then the ratio of the two can be meaningful in identifying outliers. With his setup, it's more likely to mean, he's using alligator clips and/or the stock garbage 4mm bullets.

B6 is GREAT for recharging RC batteries. It's a waste of money and a massive waste of time in testing HV battery modules. Not talking out my a$$. I have about 40 of them and learned the hard way.