The battery is showing low bars so we checked the voltage at each cell. 7.94 to 7.99 voltage. We cleaned the connecting bars and reassembled the car. The gauge showed 3/4 when the car was driven around the block, but dropped down to low again later. Any ideas? Thanks
It’s time to start shopping for a remanufactured battery.
You may want to try this post over at the Facebook Toyota Prius Owners club. There are many stories posted there on this topic and some of the members actually own battery refurb businesses.
Another good place is Priuschat
Since you DIY-ed battery removal/disassembly/reassembly, you can finish what you started off in DIY too.
Voltage is only one part of the story, it is also about capacity (of each individual cell) and about internal resistance of these cells.
Get your battery out again, get the connecting link-bars off so you can work with individual cells.
- Get internal resistance test done first:
For each cell-pack: connect some load like a couple of old headlight bulbs and let it draw the current for around 30 seconds, watch for voltage drop, then remove the load and measure voltage immediately after that, record that voltage delta for every cell pack you have.
Once you have all 28 cell-pack measurements, you have to REPLACE cell-packs showing substantially higher voltage jump, as these are getting your battery “out of balance”.
- Capacitance test is unfortunately much more involved and requires special equipment to be done properly.
If you happen to have a “balance charger”, it will allow measuring both discharge and recharge cycles.
I used these:
It is a time consuming process, took me a full week with TWO such chargers to get all cellpacks measured/trained.
You will want to REPLACE all cellpacks with capacity substantially lower than the rated 6500 mAh.
I used 5500 mAh as a threshold and had to replace almost half of the pack.
Most likely, even 4000 mAh would work just fine, but in my particular case, I had a lot of cells measuring in 2500-3500 mAh range…
note: that Prius ran to the end and what made it fail was once cellpack with shorted cell inside.
Toyota hybrid technology has a lot of room for battery to degrade before it fails them
You can procure replacement cellpacks from eBay, but pay attention to sellers advertising that they perform “load test” (that’s internal resistance) and “capacity test” on the cells they sell and would give a return/replace warranty. Both sellers I used there (who perform these tests) sent me 100% usable cellpacks, which passed my retesting with flying colors.
So far, my Prius works just fine, the budget was $330, including buying 2 balance chargers, from which I returned one since it has one of channels working unstable, so final tally is $250 or so
one more thing: if you charge individual cell-packs, NEVER do that on the packs taken out of compressed block - they will bloat and can even explode (depending on current)
for the proper repair, you have to do both #1 and #2, but if you are OK with less certain results, you can go with #1 only and get good replacement cells only for what fails internal resistance test, most likely you will get it running fine
Wow, @thegreendrag0n - quite the rebuild job. How many miles/years were on the pack before you started this work?
I needed a “starter car” for my kid, and everything I’ve seen around in “under $2K” budget was really of “dead meat” sort.
I spoke to few friends, if they had any older cars they want to dump, and one said that his has a friend of his who’s wife’s Prius just got torque battery failing, after she let it sit idle for something like 3 months, but the rest was fine, they owned the car from 30K, up to 117K miles when I bough it.
car could be driven, but with no torque battery and with 86HP engine, I could barely make it to go 55 MPH with gas pedal on the floor as I was driving it to my garage
obviously, I had more than enough time on my hands to make any repairs I wanted, as it was not a daily driver
currently car is on 119,500+ miles and ticking
Thanks for the info. Leaving a hybrid sit for 3 months is bad for the battery (as you know, and made use of). I wonder how many folks park one when going south/north for the winter/summer.
user manuals for both Toyota and Honda have it… somewhere between paged 300 and 500… but who reads these stinky manuals ?!?
At the very least, Toyota recommends re-charging battery every 2 months or so, and they do have a procedure to make it happen: just start the car, press the gas pedal and it will run and charge.
In Honda, it is like many things in Honda: they have similar provisions, but nowhere in manual they describe HOW to charge and “gas pedal trick” does not work, so go figure
Another annoying thing in my 2019 Accord is that it’s easy to add a radio channel to “saved”, but their ingenious programmers did not implement any way to remove it… oh, well…
Might not work but if button 3 is set for 87.5 can’t you manually tune to 97.5 , press 3 and hold to over ride the setting ?
Honda’s new audio system does not have “numbered presets”, it has a touch-screen with “+” button you use to create as many “presets” as you want, then you simply swipe the list with your finger and select what you want.
So far I have 20+ “presets” of that type.
You can reuse “the preset” by long-press as you described, but you can not remove anything from the list.
The closest I’ve found was “reset to factory defaults”
OK , I see what you mean . Of course I am one of those that only use 4 presets .
This is where I want my 20 down to 10, but my only option is to wipe clean and start over
Mr. Dragon , since I still have not had enough coffee before I go to the garage to finish the display case I am making . Why not just put the 10 at the top of your list and not worry about the rest.
I ended up doing just that, Mr. Volvo
Now I have some garbage popping up as I use “left” / “right” on my steering wheel when I’m past first 10.
I do not know my position, they are not numbered.
Anyway, it is annoyance, not a deal-breaker