The importance of good information.

[RossW]

How many of us have a battery bank that we kinda ignore? We know we shouldn't, but it's been too much of a hassle, or I'll do it next weekend, or any of a hundred other excuses?

Then along came the midnite classic, and various code to watch it. And to graph it. And wow, what a bonus it was. We could monitor our battery banks and convince ourselves that things were going along just fine - because we could see it.

Well, here's a thing...   exhibit (A).


From around 14:30 to 16:30 the batteries were in float. 55.6V, rock solid. Looks perfect! That's exactly what I set the float volts to, they've charged, held float, then the sun has faded...

You could be forgiven for smiling and going off to do something more important.


But wait. There's more.
And it's ugly.
Here's my new, expensive, LiFePO4 cells. The ones that I can KILL by being horrible to. The ones I made some extra monitoring for, just because I could. And what a different story IT told me...


When I got home and was able to attend to the alarm I got, I immediately slapped a load across cell 15, but in the process discovered one of the "cell equalizer" modules cable had not been crimped properly!

I think it's now fixed... but I'll be watching it! It just goes to show, whatever you have, whatever you THINK you know, don't get complacent. You quite likely DON'T know the full story.

RossW

[TomW]

Hah.

Addicts can justify their addiction in many ways.

This is one way logging addicts do it!

Just because you are paranoid does not mean they ain't out to get you.

Tom

[ClassicCrazy]

What caused V04 to go up to 3.6v ? 
How did the cell equalizer bad connector cause it to go high ?  Isn't the equalizer to make sure the low cells get an equal amount of current by bypassing the other cells that are already hitting their setpoint ?

[Westbranch]

I believe Ross' issue is that all the cells are new and the Hi V one should have been the same , problem was caused by a poor connection.... resulting in an over charge...??

[RossW]

How did the cell equalizer bad connector cause it to go high ?  Isn't the equalizer to make sure the low cells get an equal amount of current by bypassing the other cells that are already hitting their setpoint ?

The cell equalizers/balancers that I use are far from your normal wasteful "top-of-charge" balancers, which simply dump power as heat once the cell volts get to a setpoint.

Mine are a bidirectional device that will attempt to hold all cells equal regardless if they are charging, discharging or just sitting. The highest cells will export power to the lowest cells.

So the one that went high (for whatever reason) *SHOULD* have been exporting power to the other cells to help bring them up. With a crook connection, it wasn't. Worse yet, because of the constant-VOLTAGE charge, when one cell went high, it by necessity, meant the other cells had to receive less!

[boB]

This also shows that no product is 100% reliable.  Quality control is essential in reducing the problems
but you just can't  fix them entirely... Just reduce them.

In this case, a bad crimp.   This is also why LifePo's or whatever style of Li batteries need to have
a BMS.

[zoneblue]

We assumed because of your absence, that you had been busy with the new bank (and other things , er possibly). Now time for some photos!

[RossW]

We assumed because of your absence, that you had been busy with the new bank (and other things , er possibly).

Yeah, I accepted a bunch of work I shouldn't have, and I'm about 170% overcommitted for a while...

Now time for some photos!

To save replicating the same effort, does this satisfy the need? http://www.anotherpower.com/board/index.php/topic,931.0.html (if not, ask and I'll supplement as required!)