Grid Charge HV Battery to Balance?

If one had the charger that Toyota uses, they could probably do it that way. Problem though is you still need to pull out the bad cells, otherwise the Prius will develop the DTC like P0A80 and so forth.

 

That is one aspect that would need to be considered carefully, as heat is the thing that one wants to avoid as much as possible. Keeping the individual cells below 50C at the highest, and hopefully lower, is a good idea.

Doing an equalization charge is pretty standard practice in series strings of flooded lead acid batteries, for example, but those cells can be topped off with extra water if needed. Strong cells are not damaged unless they run dry, and currents are moderate.

I would probably use the series charge method myself, as a possible life extension method. But as you say, this is equivalent to the battery being on life support. My own driving pattern sees the battery topped off each trip, to the point where I get the full battery temperature rise and the system folds back on charging current. In that case, I suspect the battery is getting equalized well, but also experiencing extra stress as well. So equalization charges would be more applicable to those who rarely see such conditions, such as mostly flat land driving situations.

 

If you get a good prototype working and running properly, you should patent it and sell it to Toyota or it's competitors. Or at least the schematics of it. A lot of vehicle builders today are now offering "Hybrids". As pointed out, the drawbacks will be heat management. I do agree it would/should lengthen the life of a dying battery but one also has to consider the investment versus the payback on such a project.

No harm in trying, that is one thing for certain. I still haven't decided what I will do if and or when the traction battery gives us trouble. Maybe be lucky and still be under warranty. Have several options that are available if needed though. At this stage in my life, it would probably end up being done by someone else as my capability is not what it was when I was younger/stronger. Still got a pretty sharp mind, but the body is getting used up...

FWIW, I think "hybrid" is simply a stepping stone to what ever the next source of fuel will be. It is obvious that at some point mankind is going to have to change from fossil fuel as it is not limitless. But it is a good thing for what it is today in this day and age. 50 or 100 years from now chances are it will be something totally different from what we see and use today. Think "The Jetsons"

 

I take the crude but effective approach to experiments such as this, to get an idea of worthiness before investing a lot of time in something fancy. If one were keeping an eye on the system to see how it was progressing, the charger could be as simple as a Variac, a voltage doubler rectifier, filter caps, and a series light bulb of proper volts/watts that would limit current to the desired level. Those with 220VAC available would not need the voltage doubler. A simple bridge would do. Adjust the variac to dimly light the bulb, and slowly keep adjusting as the bulb dims. This would take minutes to assemble.

This makes sense to me as I am very experienced with high voltage, but I can imagine some will not be happy with such methods.

 

This is something I posted on about 12 months ago. I am lucky that in the UK we have a 230 volt AC supply. This can easily be rectified and then used to charge the Prius battery through a light bulb. This would limit the current to the battery. Since we have bulbs rated from 10 watts to 150 watts readily available the charging current could be closely controlled.
I suggested doing this at 100,000 miles to bring back any under charged cells back into line before they get to a point where they my become reverse charged. Charging the battery at 100 ma would only give a maximum heating capability of about 25 watts spread over the complete battery, and charging it in situ would allow a supply to be put on the cooling fan.
Charging could also be accomplished in the same way as the original Japanese Prius by using an inverter off a 12 volt battery. The output of a 300 watt inverter could be rectified and fed through a bulb or resistor to limit current. A standard 60 AH car battery will run the inverter and would be capable of adding "allowing for losses" 600 watts to the HV battery. If the 12volt battery was on charge while charging the HV battery this would extend the amount of charge put into the HV battery.

John (Britprius)

 

I've done balance charges as needed on hybrids for some time now.
I agree that preventive balance is a good idea, but it is hard to convince most people of that fact.
Also, from a shop standpoint it's hard to find a price that is equitable for this service. At the least it is a few hundred dollars.

Some shops are offering this kind of service for $1,300-$1,800.
I let you make you own conclusion about that.

The big battery refurbishing companies have high end, automated systems that do charge/discharge/rebalancing.
Think $15,000 - $20,000. Of course they are regularly using it every day.

So what about the little guy whose labor is free and has plenty of time (weeks/months) to do it themselves.
Lowest cost solution is to buy some power supplies and wiring them together in series with some wire nuts. Not safe, but would electrically work. Throw in a volt meter and an electrical load for discharging (some lightbulbs?) and you are good to go. (Just be careful! That high of voltage DC is lethal. Don't let your kids or pets near this setup.) I've helped people who have no other financial solution do this.

But that's rare. For most people, they are not going to goof around with 230V DC power.
They'd rather buy a pre-made solution.

I can sell you a safe charger that will do a whole Prius Pack.
(Side benefit: It's also nice to have around in case you ever drain your big pack when out of gas.)
For rebalancing, I would still encourage the use of a discharger if you really want to get any benefit out of it.
And before even doing the whole process you should weed out the obvious bad cells if you can.

If you do several cylces the process will take a few days at minimum.
It isn't going to "fix" you battery, but you might get a bit more use out of it.

 

A common approach with various automotive components is to pull your failing part and exchange it for one that's been pulled from someone else's car, carefully assessed and rebuilt, complete with replacement parts as required.

This is happening with hybrid batteries as well. You give them your failing battery, and get someone else's battery, that's possibly had some cells replaced, and been carefully rebalanced, on a bench somewhere. The same people will often offer an all-new cell battery (still in a recycled case) and/or all-new and higher capacity.

Another approach is to go to the car company, see what they can do for you. Even if you're out off warranty, they may make a good will offer.

We went the latter route with an 06 Civic Hybrid lately, but I was researching all the options. GreenTechAuto is one outfit to check out.

 

Yes, I have grid charged Prius battery. In my opinion the prismatic cells of the Prius respond better than the cylindrical cells of the Hondas.

Again, I would make sure to weed out the really bad modules first using some active load tests.
(As opposed to static bench tests.)
Sometimes it's pretty obvious which ones are not going to be worth trying to save.
Once those are out of the mix, then go through with balancing.

The high-end chargers I use have the ability to return the battery a starting reference voltage.
That way the battery going in is similar in voltage to the battery that came out.
Sometimes cars don't like it if you jam in a new pack that is too far off voltage-wise from the old pack.

I'm pretty lucky. I get to drive hybrids that have new packs, refurbished packs, or re-balanced packs in them all the time. There is nothing like a healthy pack. Especially if you have been driving an unbalanced or failing pack around for a while.

I enjoy seeing the smiles on my customers faces when I return their hybrid to the performance they love.

That's why they call me the Hybrid Battery Hero.

 

Eric is sharing a lot of good information. Not only does the grid charging seriously help the Honda and Toyota cells, a sub-$400 complete 'Grid Charging' system for the 04-09 Prius will be on the market and available in only a few weeks very soon. 99-03 systems will be available as well for a little more. Here is a sneak peek at some final testing we are performing on a larger 1st generation Prius 38 module pack:



These systems have been proven to add years to the life of the Honda IMA batteries. Constant current power supplies, isolated HV fan operation, and many more features are standard. We will also have a very advanced variable load discharger for those who want to deep discharge their packs to restore lost capacity. In the thermal test above, we are seeing a steady 5-7 deg F temp increase across the pack after 24+ hours of charging. Very acceptable.

Interestingly, this specific pack (which is at 335v) had sat for years and was less than 10v 24 hours ago . . . It's going into a car tomorrow for some post-grid charge real world testing

 

The above system if it comes at around the suggested price is a very realistic alternative to using chargers for individual modules. I am sure there will be more than a few people here that will be awaiting the specification, and final price.

John (Britprius)

 

I have been watching Jeff's progress on his business for many years now. Great guy. Great products.

I have been waiting for the day he would come out with a charger I could share with the Prius community.
While I'm sure many people think they want a dirt-cheap sub-$100 model, the reality is paying for a product that has more features and safety is going to be worth it.

Once these come out I am certain that my shop will be a distributor immediately and I'll have them available through my web site or by contacting me directly.

Gen1 system should cost more simply because it will likely need to use more internal component because it operates at a higher voltage than a Gen 2 system.

Not every pack is going to be able to be saved this way, but at the very least, using a grid charger as part preventive maintenance it may help extend the life of many packs.

 

Unfortunately the likely cost in the UK will be close to double that in the US, but lets wait and see. I am fortunate that I can build a system, but it would be nice to have a purpose built unit off the shelf.

John (Britprius)

 

Thanks everyone for the kind words. I ship the Honda systems all over the world. I have even sent one to Pakistan and one to Iraq. Shipping is $60 USD, but otherwise the system cost is the same (in USD of course).

The 1st & 2nd generation Prius charger designs are already finished. I estimate late-March April for the formal release. Pre-production units are already in the field balancing Prius HV batteries for a few select customers on both coasts. The 1st generation unit can be seen in the photo above. The 2nd generation Prius Grid Charger will have the same package as our Honda systems, which can be seen below and on our website.



We are still finalizing the PCB and firmware for the Prius car harness to drive the HV battery fan while grid charging. We understand how critical it is to not use the cars 12v aux battery, so we will provide our own power for the HV fan.

The Advanced Discharger is currently in internal beta testing and is currently estimated at around 8 weeks behind the Prius charger systems.

Eric is a valuable resource for all of us and a trusted retailer of our products. When the Prius kits are released he will be one of the first to carry them

 

Jeff, great stuff here and I'm a bit of an oddball because I'm looking to charge a 288V (30x 9.6V modules) highlander battery back.

Would the 1st gen Prius setup work on my setup as well? Any possible issues?

 

First of all, it can be done but may be done as a one-ff since there is not many requests for it from Highlander owners.

Since it is a bit unique maybe there would need to be some tweaking of the voltage.
Another issue would be running fans to cool things while grid charging.
And of course the actual mounting point are different that Prius.

Are you having battery/drive-ability issues right now?
Or are you just trying to be proactive?

 

No, I currently have a p3011 (Battery Block 1 Becomes Weak) and I will be rebalancing it myself soon (same basic method as Prius), but it would be nice to keep the battery in top shape after the repair too. Unfortunately there areńt as many highlander and Lexus RX400h on the road as there are prius, but I am sure this will become a better option for hybrid SUV owners as time goes on since the value of the cars will continue to drop in comparison to the replacement cost of a new battery.

Look forward to anything you might be able to develop for my application.