Lexus Gs450h (2006) Re-hydrating Hybrid Battery Cells

Darklore3003 · August 13, 2015

Really just a quick question, has anybody attempted a re-hydration of HV Battery cells on a GS450h?

I have recently bought a faulty GS450h needing some HV Battery work for a very good price.

I have been doing some research to the Prius Gen2 over on the Prius forums. They use an almost identical NIMH Battery module, made up of 6 cells. I know that strictly speaking from what I have read that you definitely shouldn't use Gen2 modules in the GS450h but I am wondering the actual reason for this? Both NIMH modules are rated at 7.2V and 6.5ah, so surely it would work all the same???

The reason I ask this, is I am going to attempt to re-hydrate faulty modules within my Battery pack. Techstream is on order to find out where. Obviously I will be stripping the rails and a good corrosive clean up will take place.

Before anybody screams danger, I am very comfortable with Hybrid systems, having worked for Lexus for a number of years and understand the importance of safety. I am simply asking if anybody has attempted something similar and not to encourage those that haven't.

Thanks

Mihanicos · August 14, 2015

I would certainly attempt the same.

The only think to consider, is the maximum charging current to be the same and the ampere hours [capacity ] of the replacement batteries to be the same.

The internal resistance of the replacement batteries should be the same or lower.

Darklore3003 · August 14, 2015

My thoughts exactly.

I will be using the same principles as the guys over at the other forums and using a 20% mix potassium hydroxide (KOH) to build my electrolyte.

A bone dry cell should take around 10ml, so i will weigh each module as i go. I will be doing 3 charge/discharge cycles on them and rating the mah for balancing.

I think this will be time consuming but worth it in the end.

Thanks

Darklore3003 · September 15, 2015

OK, well I ended up attempting it but didn't rehydrate the cells. Instead I triple cycled (0-100%) each module, typical capacity before was 2500mah but after the cycle, over 4000mah. Vast improvement!

I couldn't bring back one module, looks like a cell had reversed and couldn't get over 6.7V, although capacity was good. I assume this was across the remaining good cells.

I bought Prius Gen 2 modules and fully tested (cost of £30). I can report that it fits the Lexus module specs EXACTLY. Don't be fooled into thinking the modules are different, they are not!

New module fitted and put the car back together, drives absolutely spot on! Averaging 33-34mpg and I am quite generous with my right foot :)

Now to improve handling using Tanabe NF210 springs!

cruisermark · September 18, 2015

hi darklore

you appear to know alot about the hybrid system in these cars

i have been considering one of these for a while but when i read about hybrid cells starting to fail on as low as 70k miles it scares - but i still want one lol

when buying what should one look out for apart from the abvious service history and hybrid health check. Are there any tell tales signs of imminent hybrid battery/component failure

is it best to go for a low mileage car or a higher mileage one i.e what prolongs the life of the Battery - more use or less use

what is the worst case scenario - say the hybrid system fails or things like the inverter fail which are expensive can the car still be run on the petrol engine only? i drive a 430 at the moment

thanks for your input

Darklore3003 · January 28, 2016

Hi CruiseMark,

Haven't been on this for a while but will post a reply anyway, even though you probably won't see this!

It is extremely difficult to check whether the HV Battery is any good or not on an inspection without use of a techstream and testing each paired cells (i.e. module pack). Best thing to do is take it on a test and drive it like you stole it. Make sure the Battery discharges and charges without any hitch and that you have plenty of power in the process! I tend to go for higher mileage car's as I am fortunate to have 12 years experience in diagnostics and vehicle repairs, largely in the hybrid world, not only that but all of the recall work (if any) and any warranty TSB's should have already been captured/fixed in the first 3 years or 60k of it's life.

You mention the inverter, very very rare for one of these to fail. The vehicle would probably not run on petrol only due to the toyota synergy style systems and there being no physical connection between the engine and driven road wheels. If the HV Battery was knackered, it would run on petrol alone.

cruisermark · January 28, 2016

thanks for posting up- very helpful

OldTrout · January 28, 2016

15 hours ago, Darklore3003 said:

Hi CruiseMark,

Haven't been on this for a while but will post a reply anyway, even though you probably won't see this!

It is extremely difficult to check whether the HV battery is any good or not on an inspection without use of a techstream and testing each paired cells (i.e. module pack). Best thing to do is take it on a test and drive it like you stole it. Make sure the battery discharges and charges without any hitch and that you have plenty of power in the process! I tend to go for higher mileage car's as I am fortunate to have 12 years experience in diagnostics and vehicle repairs, largely in the hybrid world, not only that but all of the recall work (if any) and any warranty TSB's should have already been captured/fixed in the first 3 years or 60k of it's life.

You mention the inverter, very very rare for one of these to fail. The vehicle would probably not run on petrol only due to the toyota synergy style systems and there being no physical connection between the engine and driven road wheels. If the HV battery was knackered, it would run on petrol alone.

This is very useful information Darklore3003.

Can I be sure I understand your last paragraph please?

You are saying an inverter failure immobilises the car but that even with a dead HV Battery the car will run on the petrol engine alone?

John

carnut1980 · February 12, 2016

@darklore. Are these the prius cells you refer to?

http://www.ebay.co.uk/itm/2006-TOYOTA-PRIUS-HYBRID-PANASONIC-SINGLE-BATTERY-CELL-NIMH-MODULE-2004-ONWARDS-/271883579620?hash=item3f4d8630e4:g:HtkAAOSw7ThUgbgp

Darklore3003 · February 12, 2016

@OldTrout - Yes, exactly that.

@carnut1980 - Yes that is correct, these are the Gen2 modules and will fit the GS HV Battery pack.

A quick update, Battery still operating as it should with about 6 months of use now. I did briefly have an engine warning lamp but this was due to crank position sensor, a common fault. I cleared the codes and it hasn't come back since. Tanabe NF210 springs have been fitted and handling has been vastly improved! I have done the DVD mod for passengers and will also be fitting an AUX/USB kit when it arrives. My plan is to flush mount the aux port in the centre armrest compartment.

carnut1980 · February 12, 2016

Thanks for quick reply.

Can the techstream setup check each of the 40 hybrid Battery cells for voltage? IE without having to visually inspect them?

There are a lot of techstream cables and software for sale. Are they all as good as the reviews?

Any bugs? Cheers

hybridbatterysolutions · February 12, 2016

No I am afraid it can't - it checks blocks which consist of 2 modules each.

A note :- voltage does not equal capacity

tomostrio · February 14, 2016

On 12/02/2016 at 0:28 PM, Darklore3003 said:

@OldTrout - Yes, exactly that.

@carnut1980 - Yes that is correct, these are the Gen2 modules and will fit the GS HV battery pack.

A quick update, battery still operating as it should with about 6 months of use now. I did briefly have an engine warning lamp but this was due to crank position sensor, a common fault. I cleared the codes and it hasn't come back since. Tanabe NF210 springs have been fitted and handling has been vastly improved! I have done the DVD mod for passengers and will also be fitting an AUX/USB kit when it arrives. My plan is to flush mount the aux port in the centre armrest compartment.

Hi, excellent write up. Thank you. Very informative. You mention about the crank position sensor, does this have a code of p0017, by any chance ? Only asking as I have the same and you state it's a common problem. What causes it, is it as people say the timing chain has stretched? Does this issue cause any major issue to worry about? Because I am thinking of selling mine because of this issue.

carnut1980 · February 18, 2016

Re: my techstream issue, its all sorted now. The driver that came with the cable wasn't working. I downloaded the 2.0 version , as advised by others on here. Thanks guys. Awesome software!

Britprius · February 29, 2016

The Prius modules are 6 cell nominal 7.2 volts. The RX400/450450H modules are 8 cell nominal 9.6 volts. Both rated at 6.5 amp hrs. This means the modules are not interchangeable without considerable fudging of voltage returns to the Battery ECU. The GS450H module are the same as the Prius. (Above edited to clarify wrong information)

I did a considerable amount of work on methods of re-hydrating Prius modules "documented on Prius Chat" that would work just as well on the longer, and higher voltage Lexus versions. The method requires drilling two small holes in a module "about 1mm" to enable the topping up of all 8 cells equally. Distilled water can be used but I used a solution of water, and sodium hydroxide. Potassium hydroxide can also be used. In manufacture a mixture of both is used.

Results on old gen1 (2002) modules bought them back to full capacity in fact over 6.5 amp hrs.

Darklore3003 · February 29, 2016

Sorry to correct you Britprius, but GS450h is indeed 6 cell with nominal 7.2V and there are a total of 40 modules. You might be thinking of the RX400h modules which are indeed 8 cell with nominal 9.6V.