Can you post another thread with the info and findings on this?

 

It's buried in this thread starting on this page:

https://www.greenhybrid.com/forums/f...tml#post254115

I tend to ramble. Once I've wrapped things up, I'll post a summary of all my experiences between grid charging/discharging and stick-level refurb.

How did your stick-level refurb go?

Steve

 

I will find out in a month or two. I should have gotten more chargers ahead of time.

 

I used a single B6 as a charger and a CBA III as a discharger. It can discharge a subpack at 5.5A or a single stick at 11.5A... so it's 5 to 11X faster than the B6 at discharging.

took me a couple weeks to get 3 cycles on everything, and I wasn't very efficient during the weekdays.

 

I'm out of the loop on this stuff - for you guys using these chargers and what not, what exactly are you doing? Hooking trickle chargers up to the battery packs or the car or something? I'm the first to admit I'm not an electrical engineer, so if you can keep it at the layman level, I'd appreciate it

 

First, these packs are elaborate assemblies of high quality NiMH "D" cell batteries. On the 00-09 Insight and 03-05 Civic Hybrid, there are 120 and on our 06-11 Civic Hybrids, there are 132. These are not your "standard" D cell batteries. they are rated for very high discharge and charge rates; however, due to the fact that they are all in series, a single bad or marginal cell can make the whole pack perform poorly.

The 120 cell packs consist of 20 6-cell welded "sticks". The 132 cell packs use the same sticks but are joined in pairs with one end welded together.

In order to maximize the life, the car keeps the battery between 20% and 80% of the maximum charge. When NiMH batteries are operated in this range, they can be charged and discharged indefinitely with very little degradation. If you were to cycle them from 0 to 100% repeatedly, you would get on the order of 500 cycles. When you consider that every accel is a partial discharge and every coast or brake is a partial charge, you can see how quickly you would hit 500 cycles if these used the entire capacity.

We're talking two different things when discussing charging... GRID charging is a home-built or commercial charger connected to the power grid that's used to "trickle" charge a complete pack over 20+ hours to take all the cells to max capacity. These packs are rated for 6000mAh, and these grid chargers typically charge at a 350mA rate. Divide 6000 by 350, and you get 17 hours charge time for an empty battery; however, charging past 70% capacity isn't 100% efficient, so multiplying by 1.5 gives you 25.5 hours to insure the pack is fully charged. At this charge rate and for these times, the cells will dissipate surplus charge as heat. It is safest to use active cooling.

Many of the commercial grid chargers available provide a means to run the car's battery cooling fan to keep it cool. If you've removed the pack, a simple box fan blowing through it provides enough air flow to keep the cells from getting too warm. At 140°F, the cells will vent the magic smoke and lose capacity. This grid charge pushes ALL the cells to 100% capacity and helps to balance all the cells so they are operating at or near the same state of charge.

When possible, discharging a whole pack via light bulbs or shop lamps to 120 or 132V (1V/cell depending on cells in pack) can help to restore capacity to weak or marginal cells. It is speculated that discharge below 0.78V/cell can potentially unlock lost capacity. The danger in this situation is that while the average Voltage will be 1V, strong cells will be higher and weak cells will be lower. If a low voltage cell is driven to zero, the adjacent cells will drive current in the reverse direction and potentially damage the cell if not recharged immediately.

I recently did this grid charge/lightbulb discharge exercise with my original pack, and it is performing substantially better than before (3-5 recals/trip with almost no IMA assist vs. 1 recal per trip with very good IMA function).

When we talk "stick" level or refurb, we're talking about disassembling the packs to access the "sticks." This is generally accomplished using chargers developed for the hobby market. These chargers often have a "balancing" or "cycling" function where they can charge and discharge automatically according to supplied parameters. This can frequently restore significant function to a stick or stick pair. It can also identify sticks or stick pairs that are significantly different from one another.

Ultimately, you want all of your sticks to be matched in the following parameters:

1) total capacity - weaker sticks define the total capacity of the pack as they will limit the 20-80% range the car uses.
2) state of charge - you want all sticks to be at the same % of charge during use.
3) rate of self-discharge - All NiMH self-discharge. Sticks that self-discharge faster than others will get out-of-sync faster and be at a different state of charge (#2).
4) internal resistance - this governs how fast cells charge and discharge and the amount of heat generated. You want sticks capable of discharging at the rated 100A and charged at the rated 50A rates.

The list isn't conclusive, but it covers the big ones. The stick level refurb only provides information concerning #1 and #3. The stick cycling gives you a direct measure of the stick's total capacity, i.e., how much of the rated 6000mAh is still usable. Anything over 4800mAh is considered good (80% of new capacity) provided they can still accommodate the charge and discharge rates (some can't). You still want them reasonably matched. In my head, 5-10% is good. #3 is confirmed at the end when you've let your fully charged sticks sit for a week and then re-test them to see how far they've self-discharged. Again, in my head they should still be within 5-50% of each other.

#2 is assumed to be good when these tests are successful.

#4 is beyond the ability of most to test. Loading a stick with 100A and charging at 50A is beyond the capability of most. The shops that provide refurbed or new batteries have at least some capacity to test at these levels. Maybe not 100/50A but maybe 80/40A or something well higher than what these hobby chargers can do.

I'm using a CBA III to test my sticks. It's capable of 100W discharge power where your typical hobby charger is limited to 5W (typically 1A load). It applies a fixed load and keeps it applied until a prescribed voltage is met (1V/cell). It reports the actual capacity used. I use the hobby charger only for charging. In my mind, the 11.5A discharge rate is more aggressive and provides more accurate results than a 1A discharge rate; however, the 1A discharge rate is likely more beneficial for restoring capacity as you can extract more total electrons at that rate. At the higher discharge rate, the voltage can drop off pretty quick, and the voltage will rebound back above the cut-off voltage by a significant amount.

The downside of the CBAIII is the higher load isn't as effective at restoring capacity unless deliberately set at a lower load.

The downside of most hobby chargers is a 1A discharge rate can take several hours to complete a cycle... 1-2hr to charge and as much as 7-8 hours to discharge. In most cases, while it's rated for 1A, it's also limited to 5W, which means you can only do 1A at 5V. Most of these sticks start at 8-9V when fully charged, so you're well under 1A load at that voltage.

There are higher end chargers costing north of $150 that can also discharge up to 10A or 50W. They tend to be higher quality and provide better results. They also tend to have the ability to chart your results on a PC. A very popular charger was the MRC Superbrain 989 when stick refurbishment started to be a thing. It is no longer made, but there are still some floating around for $150.

That's a brain dump for me. I hope it sheds some light on it for you. It's mostly accurate, and I welcome any corrections.

Steve

 

I have 2006 Civic Hybrid, the original battery failed at 66k miles in Dec 2010 (car lost complete power and engine lights came on), it was replaced under warranty, the second battery failed last week (Jan 2015) at 104k miles. Honda is helping with replacement cost, I am paying ~10% and they are paying the rest.

I was supposed to get the car back the same day, but they forgot to order some parts (other than IMA battery itself) and gave me rental for 1 week as they couldn't put the car back together for me to bring it back next week.

I always used some parts of the hypermiling techniques, and only went above 4k RPM twice to avoid accidents, I don't think I would recommend buying hybrid's to anyone after this experience.

 

Yah it seem (I'm guessing your area is hot), batteries just don't last too long in the heat.

 

Sorry for your bad experience. I've had battery problems as well. However, other hybrid designs haven't had as many battery problems. And Honda started water cooling the batteries in subsequent Civics.

I'd probably still get a hybrid next time

 

Yep.

Toyota seems to do a pretty good job, at least w/the HV batteries on Gen 2 (04-09) Priuses and beyond. See http://prius.wikia.com/wiki/Lifespan/Operating_costs and what are supposedly Honda's weaknesses at http://priuschat.com/threads/salvage.../#post-1252078.

http://www.consumerreports.org/cro/n...orse/index.htm was shockingly bad to me, much worse than even I expected.

I wouldn't recommend anyone buy a Honda hybrid since it seems they couldn't get NiMH right after over a decade... so them getting li-ion (they've switched over to it now) right w/much less experience doesn't sound that likely.