Prius Battery rebalance thread

Does anyone have settings for the Thunder T6 charger? I can't seem to force my charger to push the 7250 mah of charger it just stops at whatever it feels like. I'm guessing because of the delta peak settings. (Which for mine is default)

 

I've tested quite a number of different chargers - those RC modellers use (1 channel and 4 channel - have 5 of different types).

Those RC chargers are not bad for testing power tools batteries, laptop and RC batteries testing, however have deficiencies:

• low discharge current,
• delta-v default settings - that is a killer for those to be used with traction batteries. I explain: it will stop as noted by Lam "at whatever it feels like". The box of old NHW-11 modules which were used for the last two years many times in my Lab for testing Analysers, Loads and Chargers - when charged by different RC chargers (1 channel or 4 channel) - showed no more than 2,4 - 2.7Ah.

I have designed and built quite a few High Voltage Chargers (SMPS, up to 240V DC, up to 2A, Constant Current).

Recently developed and build asymmetric pulse DC charger, microcontroller based (following claimed to be "Rocket Science “design) and tested 4 modules just to see whether those still can be used in electric byke - surprising results - those old modules (from 2003 NHW-11, previously showing no more than 2.7AH) took and release charge measured by Analyser as being 3.4 - 4 AH after 3 cycles (programmed charge @2A to stop @ 4.5AH in, 12 hours idle after charge, discharged at 3A) No build up heat - temperature rised during charge from 16 to 17 degrees Celsius only (Spring in New Zealand). Alarms were set up for over temperature and overvoltage - that appeared to be unnecessary.

The point I am making is: it is not reconditioning or rejuvenation (there are companies around who are making statements of them being able to recondition/rejuvenate to near new condition) - it is about using chargers which may do the job little bit better than others.

Last night 2006 Prius battery came in with two modules failing and showing 6.2V each - pulse charged those - two cycles - no indication of significant improvement yet. Will do more tests with the goal to bust the myth of "rejuvenation/reconditioning". That pack will undergo full testing on the 28 Channel Analyser to see whether remaining modules can be combined together with already tested modules from another 2008 pack to compile 38 pack for my friend's NHW-11.

• It is a fact that you should NOT fall into believing that you can just buy one or two modules on eBay and fix your pack.
• Modules must be of the same capacity.
• When you buy a rebuild pack from battery rebuilder - always ask for tested remaining capacity of the modules. Do not be fooled by warranty - as many just give warranty in hope you will never show up or they can blame battery failure on you, your car or something else and get away with it.
• Personal opinion: price of rebuild batteries must be dependent on their remaining capacity - as 4AH vs 5AH could mean few years difference in the remaining lifespan and it can die shortly after the warranty rebuilder gave you has expired.

 

Kiwi you make it sound utterly impossible to fix your battery with an RC battery charger and some good spare modules (yes, sometimes even from ebay) yet somehow I and many others have done it very successfully........maybe we're all just lucky right?!

Here's the settings you need.....

Mode: Program Save then use Program Load when cycling other modules
Battery type: NiMH
Nominal voltage: 7.2V
Charge current: 2A (lower is better to prevent excessive heat buildup at high SOC)
Discharge voltage: 6V
Discharge current: 1A (use highest setting available)
Charge capacity: 7000 mAh
DCHG>CHG: 3 (more cycles if modules continue to improve)

Also go into User Set Program and set:
NiMH Sensitivity: D. Peak Default
Capacity Cutoff: on, 7000 mAh
Safety Time: off, (time doesnt matter)
Temp Cutoff: 45C (if you are using temp probes)
Waste Time: 5mins

Make sure to load test them all too (very important!!!!!!) and then draw voltage down to around nominal (7.2-7.6v) before final balance and install or you may get a code thrown.

 

Test completed last night on 28 Ch Analyser - simultaneous discharge of 26 modules under 5A load. Results in brief:
4 Modules in the pack are dead and the rest 24 - showing different capacity between 2.8 and 3.5AH
Not recommended to be used for any battery re-build. Probably can only be used in electrik byke.
Just to save you guys time & money if you are looking to source "just a module or two" to fix your pack - do not waste your time....
Especially when fixing NHW-11 - finding the match - is too hard - you need dosenz of modules to choose from.

 

Thanks!

Thanks for this. did your cells charge up to 7000 mAH each and every time? What was your delta-peak settings?

 

These modules are rated at 6500 mAh and new ones will slightly exceed this capacity. My modules managed to approach this capacity (measured at 0.1C load which is the limit of these hobby chargers) when rebalanced after 193k miles of use (the 27 that did not have a bad cell), but I live in a cool climate. Modules that have been repeatedly overheated due to driving in a hot climate or mountainous terrain will often have a much lower capacity after rebalancing.

JeffD

 

JeffD, I apologise in advance for some people around being frustrated when I point out that your measurements are incorrect.
But you've just not comparing apples with apples - i.e. capacity measured by you @ 0.1A with design capacity rated @ 1C. Those are and should be different.

At the currents 60 times lower - you will be getting higher capacity than it actually is .

That works equally applicable to other chemistries - to get an idea - have a look for example at the datasheet of UPS Lead Acid 7.2Ah - that capacity is not rated at 7.2 Amperes but at 0.35A.
At about 4.3A discharge current brand new UPS battery according to the datasheet will not deliver more than 4.3Ah. I recently tested those for my industrial UPS (using our Analyser or course) and capacity is different at different loads as expected.
http://jaycar.co.nz/products_uploaded/SB2486.pdf

So with absence of sophisticated tools what prevents you from building simple (LM358 + Mosfet) constant current load, set it up at 6.5A (or at least in that range - 4 - 6 A) and measure time from fully charged to when it drops to 6 volts and publish your results?
I bet you will not have your 6.5AH with that set up, will be much less.

 

All my results are in this thread (starting around page 13):
Gen II Prius Individual Battery Module Replacement | PriusChat

Delta peak setting was left at default for NiMH on the charger (also edited in settings above).

Also as Jeff pointed out YMMV because both of us live in cool climates so people should temper their results accordingly. Now I know some people are stuck on "true" measurements (relative/repeatable readings are actually far more important in DIY), using alot of technical mumbo jumbo and tossing in some acronyms for good measure, but keep in mind the average DIY person will absolutely care less as long as the vehicle functions properly, gets decent fuel economy, doesn't throw a code and the necessary equipment is in the realm of reasonable (compared to a new battery pack from a dealer).

You have the settings we use on the quad chargers above, go ahead and test it yourself.........then like usual come back and argue about why we're all wrong and DIY rebuilding our battery packs at home doesn't work again.

 

Mtl_hihy said
"....keep in mind the average DIY person will absolutely care less as long as the vehicle functions properly, gets decent fuel economy, doesn't throw a code..."
This is what I have said in other threads as well. If you are doing it for yourself at home, the reality is you do not have the equipment to do it 100% correctly. So it makes sense to not fret over some of the "mumbo jumbo" details. Do the best that you can with a reasonable amount of effort.

But the guys who are doing it for a living and warrantying their batteries for several years, it's a whole different story. The devil is in the details and making sure every parameter is checked and double-checked.

 

I quoted 0.1C (about 650 mA) since that was the limit of my Supermate DC6 rebalancer. That is 10x less than the 6.5A rating (not 60x) and I stated that for completeness as I know that the amp-hour measurement drops as you increase the discharge rate (can easily change by a factor of two). I don't do this as a continuing business and all of my modules have been used to successfully refurbish Prius HV batteries for 6 different owners and I have none left for experiments.

 

Lead acid batteries have nothing to do with the Nimh batteries in the Prius and bringing there characteristics in to the conversation does nothing but cloud the situation.
There are many people that have successfully refurbished there batteries at little cost apart from the effort involved. No one is professing to to do this as a business, but more to help themselves and others to keep there cars on the road at reasonable cost in an effective manor. This is partly why people change there own oil, and do there own servicing, and maintenance. Repairing the battery is just an extension of this, and should be applauded as such. Constructive criticism is helpful negativity is not.

John (Britprius)

 

Kiwi,
How does anything you said help this individual on his endeavor? I see zero value in anything you said. Not only do you criticize his endeavor, you offer no alternative solution. Where I come from, that's not helpful.

 

Perhaps the alternative solution I proposed - you did not understand it, although it is very simple, I will try to rephrase in a layman terms and suggest two alternatives instead of just one:

Problem Statement:

RC chargers are mostly limited to 1A initial discharge rate. That gives you wrong impression that what you have measured is a true reflection of the remaining capacity. However the design capacity of 6.5A is rated at higher discharge rate. Suggest at 1C which is 6.5A – meaning that it will be less at higher discharge rate (e.g. 55A in Prius) and higher when measured at lower rates. That is why for example JeffD may be getting sometimes readings higher than 6.5AH when discharging at lower rates (e.g. @ 0,65A - 10 times lower). Hope you understand it now.

Is that a Problem for DIY rebuilding exercise? Yes and NO.

That limitation as above does not prevent you from coming to a conclusion (assuming the tests on all modules are all done at the same temperature) that the tested modules are of the similar remaining capacity (although numbers will be wrong). But it takes much longer and because you can’t control the temperature during the day and evening hours – most probably results will vary as measured capacity is also temperature dependent.

Solution:

Suggest applying higher current – 6.5A and run your tests quickly with more realistic results.
a) Constant current circuit build in 5 minutes from parts you most probably have at home - giving you 6.5A constant current load.
b) Less accurate but almost no efforts involved – 2 halogen 12V 48W bulbs wired in parallel will give you approximately the same initial discharge current (about 7A, dropping during discharge) when discharging one 7.2V module. (I use this to discharge weak modules to zero before they go into rubbish)

End result: you will do one module in ½ hour as your old modules will likely show about 3AH at that discharge rate.
You will be able to do all 28modules in about 20 hours including rewiring time – so you can measure the whole pack with your DIY approach in couple of days at day temperatures.

End results – you’ll do your DIY test quicker and will get better understanding of the real remaining capacity in your modules.

 

John,
That link was for the illustrative purposes as perfect online one-page pdf datasheet summarising battery discharge behaviour at different currents and dependency of the capacity with current and temperature (does not matter it was SLA and not NiMH – you should be looking at a graphs).

People who deal with electrical/electronic stuff must be able to read, understand and comprehend the datasheets. If that “clouds” the situation – do not hesitate to ask and it will be given to you...

It is a fact that discharge rate and temperature affects battery capacity.

Here is another very straightforward illustration via the fast google image search in relation to NiMH batteries (Prius NHW-10 and Honda have Cylindrical NiMH. This graph is not for Prius or Honda though) 1C- here means battery was discharged at it's rated current:

If you still having difficulties to read, understand and comprehend that – do not worry – it could be dyslexia (not bad as many talented people have it) and if your GP confirms that – please stay away from Prius – as you may kill yourself by not being able to interpret the high voltage readings on the multimeter.
“Dyslexia - a general term for disorders that involve difficulty in learning to read or interpret words, letters, and other symbols, but that do not affect general intelligence.”

 

I am a retired electronics engineer so need no instructions thank you.

John (Britprius)

 

Just when you thought it couldn't get any better.........it's the gift that keeps on giving.

 

Perhaps I can rephrase this for you in laymens terms;
1) his charger does not have a 6.5A setting
2) he doesn't have the parts to build a constant current ciruit lying around his house
3) I want to see a video of you building one, in five minutes, from parts that most people have at home
4) Are you for real?

 

Note that 6.5A - was about discharge current - i.e. load not the charger.

re: 2) - you are welcome to inspect - I can arrange that for you as a "special honour" private ..... if I am getting you nick decifered correctly - could be wrong about the rank though....
re: 3) - If you pay - can be done..

Instead of video - here are your guidelines for free:

Take in-car 12-to 5v charger for your phone and dismantle it - 99% chances are there is a chip inside which is a IC which does 12V DC-5VDC 1A conversion but can do it in a wider range. Take your time - go to Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view and figure out how it works – a person who claims can fix everything should be able to figure it out.
Hint: put variable resistor, preferably 10-turn pot (you can use any 10k pot) instead of the one which provides reference voltage. Buy now if you are quick with your soldering iron - you've just created variable output voltage regulator. That would be driving the n-p-n Mosfet. ATX power supply from PC can be a donor for that little thing. You can also get Mosfets from Washing Machines, Plasma, LCD TV sets etc.

Driving the gate of Mosfet with the variable power supply made of Phone Car charger and putting the Halogen Bulb in series with the Mosfet's Drive gives you regulated current mini-lab to load-test stuff. Power the whole thing from the PC ATX 12V power supply.
Wish that be a constant current? Instead of that IC from the charger, use OP Amp and put a shunt in series with the Mosfet Source. You can get a shunt from - numerous power supplies, PC Mother Boards and various control boards (PC ATX, Convection Type Microwave Oven, Old TV etc)
I sourced dozens of Op-Amps from old Set Top boxes to play with.
Drive the non-inverting input of the Op-Amp from the 5V of that PC power supply & inverting input from the shunt. Use the 10K pot I mentioned before as a voltage divider on the non-inverting input.
Hope that helps. Enjoy

I am using that simple tool to load test power sourse if I need a quick set up and not bothered with setting up one of the High Voltage Analysers.

 

Fun stuff kiwi!
Probably not something the general public would think about doing, but good to remind them that it is possible.
Makes me think of 80's TV shows like MacGyver or The A-Team, where they could make anything out of parts that were lying around.