Prius – A charger for the prius

Hi everyone,
I am not the type of person that likes to give in easy, and I don’t like to be beaten by inanimate objects (including NHW10′s). So, in the beginning I studied all the documents I could lay my hands on and sorted out a few HV battery packs using the full strip down methords or S2000 EQ charging facility, only to find the improvements were on a percentage bases with the S2000. I.E a 30% delta SOC imbalance HV battery pack would improve to a 20% Delta SOC (making a reliable battery pack), but a 50% delta SOC HV battery pack would only improve to a 40% Delta SOC leaving it still unreliable (as a maintained 20% Delta SOC is the goal here). Generally giving a 10-15% improvement once the HV battery pack had re-settled back down.
I have further re-read the document in the file section labelled “code C2579″. Although quite vague, it indicates that, at the time of the pages being written, that carrying out an “EQ charge routine” was in fact an external charging operation with the S2000 being used to only monitor the operation. Were as all the S2000’s now have a built-in EQ charge routine program.
It is also my experience that an NHW10 that is well serviced and maintained, driven regularly, and taken on distant drives on weekly bases, have HV battery packs that fair better than those that come from NHW10′s that do not benefit from the former. This is something that I have now put down to the fact that the car is able to rely on the ICE much more on these distant drives (in a well maintained NHW10), whilst carrying out a slow trickle charge to the HV battery pack, which it seems to greatly benefit from. I also point out that i have help maintain NHW10’s that have never had the hybrid warnings come on, in what is now 5 years.
Having now talked to an electric vehicle charger manufacturer, and with the above experience, I can now say the following for the benefit of all,
(1) An equalization charge is a charge routine that is Voltage prioritised and not Amperage prioritised, I.E, on an NHW10 it would need to be 360DC Volt, variable decreasing Amperage causing minimal cell over heating as it goes.
(2) To recover/ rejuvenate (call it what you will) it is recommended by cell manufacturers to place a sustained low current supply (at full DC voltage), to the battery pack, over some time period. How low a current and how long for, seems to vary from cell manufacturer to manufacturer.
(3) That the NHW10 seems to have had 2 methods of EQ charging. The on-board S2000 “quick fix” routine which gives some noticeable improvement, and the slower external low current EQ charger, which the NHW11&20 seems to have continued on with, but not the former S2000 routine.
To this end, I have now had a “one off” external smart charger built for myself, and I have had what I think are the best aspects of well thought out EQ charge routine for an NHW10 HV battery pack, built into it. It first mimics the S2000 EQ charging by bringing the battery pack at a reasonable speed, to be fully and equally charged, by detecting the chemical changes in the cells through current absorption. Then it changes over to hold a low current, full voltage, trickle charge to aid with the recovery/ rejuvenation of the worst performing cells. How affective this will be is now down to the testing that I intend to carry out. No pain- No gain as the saying goes. I will publish what benefits/results (if any) I find from using this EQ charger as I get them.
kevin

My comments

I am sure he is right. This charger will work to keep the battery alive. However as the battery ages some cells will leak electrolyte, causing high voltage leakage, and some will just fail. These modules have to be identified and replaced. This is work for those who want to offer battery reconditioning as a service.

My thoughts are that a charger while useful for the technically savvy is not practical. It would be useful to the mechanic or technician who will be working on these batteries. However for the average Joe, the Power Jockey would be more practical. So my take is that both system are useful and as a business offering reconditioning service myself I would purchase one of these charger. ( It wont be cheap, as development cost would be quite high. You will also run into patent infringement problems with Toyota and Ford as your charger will be running parallel with their Battery Management System algorithms. There will be freedom to use issues with this charger if you decide to commercialize. )

As for the Power Jockey, once installed it is part of the vehicle and it performs the most important function of preventing the voltage dip under acceleration which causes weak cells to fail. By holding up the operating voltage the vehicle has more power and therefore better economy. The product is already developed and we are now looking at reducing the cost and improving the design. It now works very well as the unit is engaged when you start up the vehicle and disengaged when you kill the engine.

I have also used the Power Jockey as a charger for the HV battery. You do this by connecting to an external 12 Volt source or to the 240 volt outlet. As there is no BMS built in you will have to manually disconnect after 3 – 4 hours by which time there will be enough charge to start the vehicle.