Gen II Prius Individual Battery Module Replacement

@2k1Toaster and @TMR-JWAP are two of the battery experts here

 

Prodigy, thanks for the confidence vote. I don't know that my experience makes me an expert, perhaps just a confident DIYer !!

Igoryan,

One thing you can do is use the initial discharge number as a gauge for the modules. Since you've already started cycling all the modules, go ahead and complete what you are doing. Then take a look at the very first discharge value you had for each module. Do any stand out as being significantly weaker than the rest. Those are probably good candidates for replacement. Although I see many of the initially weak modules appear to recover, I don't know that I would trust them for a long term repair. They became weak for a reason, typically an internal discharge issue, which most likely would lead to them becoming weak again.

If you're just looking to get your car back on the road, a 4500-5500 spread is not going to cause you any problems. Your overall battery capacity will be limited by the lowest capacity module, but your car should work fine. Problems happen when you have a bunch at 4500-5500 and one or two at 500-1500.

 

I would keep cycling them to see if they continue to improve and if they don't recover back to near your midpoint (4500) then I would consider replacements (you'll need to choose a cutoff point when rebuilding). I would probably even cycle any below 4500 again to see if you see improvements. Real key is still the load testing but when you rebuild I would always put the weaker modules toward the outsides and the strongest ones in the middle of the pack.

 

Thanks guys,
I'll see what the final results are.
This module is definitely bad, not improving anymore - 2) 2443->3559->4069->4091
Other two, i'll try to cycle more.

I am also planning to load test when i finish with all the modules.

Would that be fine, if i bring them all to similar voltages during load test, instead of connecting all + and all - at the end?
I don't have enough cable at the moment to connect all + and all - for balancing the voltage.

 

Would be best to build a basic charger for charging the whole pack. (cost $50-$100?) and charge pack. You could use the charger later for ongoing preventive maintenance.

You could use your existing charger to one-by-one charge them to a target voltage.

But really, doing anything to get them closer would help increase your chances of success.

 

Interesting, could you direct me to where to learn more about that?

 

Basically put together power supplies in series until you reach your desired voltage.
A high quality maker is Meanwell. But there are cheap knockoffs too.
Does not need to be more than 300 milliamp. Anything higher and you risk making cells burst.

Say if you want a total of 250 volts dc, you could use a 50v supply + a 100v supply + 100v supply
Or a 50v+ 50v+ 50v + 50v+ 50v.
Depends on what you find easy cheaper I suppose.

You can add in additional safeties to try to slightly reduce the possibility of you killing yourself. Like a fuse in case you cross the wires. Or an on/off switch.

 

Would something like this work?

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F331463153324

 

This is not what I meant but it is another option if you do not want to build something yourself. Building it yourself would be less than this.

What you linked is a $215 Buchler Instruments 250vdc power supply. Model number 4333700. Plate on the back says 11amp(?). Usually used for electropherisis applications.

If we assume the voltage and amperage is variable, then you should be able to dial in from 0 to the maximum for v or a.

It is likely that you will need to fuss with it to make it work since it may not expect to have a load on it (like a battery) before startup. Depends on how intelligent it is.

 

I know there are cheaper alternatives but HA put together a slick solution that works great, it's compact and super easy to use.

Online Store – Hybrid Automotive

I would test everything separately and don't worry about what voltages they are at when you're done. Then put everything back together and install the prolong charger and grid charge it until the voltage levels off and then take it for a test drive.

 

Making it yourself us much more dangerous than buying something ready made like Hybrid Automotive's products.

You pay for the convenience and safety.

With homemade setups, I have seen people short out their pack, burn up wires, burn up their power supplies, blow out fuses, and more. No deaths, that I know of. But then again, it'd be hard for them to post that outcome, I suppose.

Be safe out there.

 

Michael, at this point, how did you know bad cells the first time discharging 8,16, 19, 22, and 25?

 

I am new to this board.
I am planning on rebuilding my pack.
I have started testing individual cells as per notes in this forum.
I have access to a few 36volt isolated lead acid chargers from ebikes.
I have used 2 in parallel to charge a 72 volt NIMH pack using ford escape NIMH cells(similiar to honda cells except 6v instead of 7.2).
I have manually watched the voltage.

If I wanted to charge the full prius pack, what voltage would be best?
28 x 7.2 = 201.6 nominal
201.6 / 36 = 5.6 so as I see it I would need 5.6 36v power supplies.
That isn't really doable though, so if I use 6 36v supplies, I would have 216 nominal.

at this I beleive I would see approx 41.4 x 6 = 248.4v during constant current charge stage.
The supplies have a rated output of 1.7a.

would the over voltage and 1.7a be too much to charge the pack?
I would like to charge the pack as a set and then apply a load to the whole pack for a while to see how well my cells stay balanced, before I put it back in the car.
I am not sure what would be a good load to test the whole pack as well.

I kind of like the display that Kiwi had, but feel that just using a load on the pack and recording the voltage per cell with a multimeter would be good enough for me.

If I ran a load for maybe 5 minutes and recorded the voltages under load, I would think I would see weak cells.

Thanks for any ideas.

I have also considered testing the cells in packs of 5 underload.
5 x 7.2 = 36. This would take longer, but does lineup with the voltage of my power supply.

Mark

 

The best way to charge the pack is with something called a grid charger. Many people here use the Prolong charger from Hybrid Automotive. @jeff652 is a trusted member here. They also have a couple of dischargers that can be paired with the charger to form a battery reconditioning system. The older less expensive discharger uses various light bulbs for different loads. The process must be closely monitored so the loaf is changed at the proper times. The newer intelligent discharger uses an automatic process.
@Raytheeagle and @jerrymildred are a couple of people who have used these systems.

 

Lots of others use the Prolong system, too. You need over 240 volts and you need to limit current to about 1/3 of an amp and keep the fan on high speed or you'll cook the battery.

The Prolong system makes it a piece of cake, especially after you install the permanent cable. If you have an aging battery or if you have replaced a cell, it's the best tool out there.

 

Thanks, Jerry.
Hybrid Automotive now sells modules too, matched to the mileage of your battery.

 

To add onto what @jerrymildred said, I have helped a member out here rebuild his pack with the Prolong setup.

His attempt was to do individual module reconditioning, but this would take a long time (probably about a month). He got the Gen2 harness and we loaned him the charger and Discharger and he’s back in the road.

Having access to this equipment and seeing his results so far after about a month, this will be the route I go if faced with a P0A80 decision .

Good luck with your rebuild and hope this helps.

 

I saw that! Cools stuff. It popped up on my Facebook news feed the other day, iirc.

Good on ya, Ray! Short of a new or near new battery, I think that that's the best fix.

 

Hi
Thanks for the input on the grid charger idea.
I will definately consider it when I have the car on the road and am confident I want to keep it long term.

I had picked up a used pack a while back and found 4 modules at 0 volts(obviously bad and were all at one end of the pack)
The others had varying voltages.
I discharged all the modules to 6 volts with a hobbie charger.
I have connected 20 of them in series for a nominal 168 volts.
I have used 3 36volt ebike chargers -(lead acid), wired in series and then connected my bench top power supply. 0-60 Volt 0-5 amp.
The chargers and the bench top supply are all isolated in design.
The ebike chargers revert to Constant Voltage with low current draw at 41.2 Volts.
So I have been setting the benchtop at a constant current setting and watching it charge the modules at a CC of .24 amps.
As the modules charge, I see the bench top voltage increase.
I have a meter set across the pack as well to monitor the overall voltage.
I also have a temperature probe and have been monitoring the cell temp.

I plan to charge to 168 volts (8.4V per module, 1.4 per cell)
Then I will document the voltages and let them sit for 24 hrs and document the voltages again.
The I plan to place a 60 watt load on them for a period of time and see how well they all hold a charge.

I will then keep track of the strongest modules and use the best as replacements in my pack in the car when I have it removed.

I hope this sounds like a good process.

Thanks

 

The only addition I would recommend is to have a fan blowing across the pack as you go.

While you are measuring temp, there still will be thermal expansion which could cause the modules to distort even though you have the pack clamped.

But I’m sure you have a fan lying around somewhere .

Good luck and keep us posted .