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Can a weak 12v battery cause this much trouble?

Discussion in 'Gen 2 Prius Main Forum' started by Hx214, Oct 8, 2018.

  1. Hx214

    Hx214 New Member

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    Good Morning,

    I'm new around here. I'm a hobbyist mechanic and my hobby is to buy older cars, fix them, drive them for awhile and pass them on or just keep driving them. New to hybrids so sorry if some of my terms aren't correct.

    I have a friend that had a 2005 Prius for work, he calls me up one day on the road and said it just doesn't want to accelerate. I asked him what he saw on the dash and he said nothing..... He got it home and said he would look at it later. I dropped of my OBD scanner for him and about two weeks later he calls me and says he now has a red triangle with an exclamation point and the OBD throws a code that says "Replace Hybrid Battery"

    So..... he parks the car and says he is done with it (227,500 miles). Asks me to scrap it for him. I told him I'd take it off his hands for scrap price. I always wanted to learn more about the hybrid systems, so cheap education right?

    So I go over a week ago to check on the car. I wanted to make sure it would at least start and run to get it home (I only live 4 miles away) It turns on and starts up the ICE right away, hybrid battery on the screen shows one bar with no movement when I drive around the block. Very slow acceleration, but enough to get me home when I'm ready for it. I park the car, and tell him I'll be back that weekend to get it.

    I show up on Saturday to get it and the 12v battery is dead. So dead that it won't even unlock the door. I thought it was odd being that it was only a week ago and it showed no sign of weakness after sitting for a whole month..... didn't leave a light on or anything so.......I run home to get one of my slim honda batteries that I keep on the shelf in the shop for just this situation (those little batteries fit in everything to get just about any car home!...... but not the Prius!!) That's when I learned my first lesson with the Prius.... not a normal battery... So I try my best to get the back hatch open to get the battery out to take home and charge. No dice. That little lever to pop the back hatch under the back cover just doesn't want to pull out... So I get a set of cables and attach the honda battery to the yellow top Optima. I get enough power to at least get the back hatch open and notice that when I took the cables off the honda battery I still had a little bit of a dome light, so I tried to power on again and it worked..... The prius went to ready mode and then the ICE started and never turned off. So I decided to give it a shot at taking it home.

    I made it the whole way home. On the way it displayed what I have read to be a hybrid battery failure. VERY slow acceleration, the ICE revved pretty high, and got up to speed after a long time and would hold there but there was definitely something wrong. The dash had the red triangle on the whole time.

    I got it into the shop and took the battery out. I tested it with my old school tester (two battery clamps and a toggle switch to put a load on it with a dial) and it showed it was weak and needed a charge, but didn't go into the "Replace" section of the charger so I charged it up for a few hours thinking it was just weak from sitting.

    Put the battery back in and the car started up fine again. The ICE fired up right at start up and stayed running.... BUT I noticed on the screen the battery icon for the traction battery was showing 2 bars all of the sudden....

    I thought that was odd so I took off to go around the block. All of the sudden the hybrid battery started to charge up. Acceleration was back to normal and it was running great. I stopped at a few stop signs and noticed that the ICE was shutting off and showing that the electric motor was moving the car.

    The icon on the battery seemed to be getting up to the second to last tick before full and would go down a bar and then back up. Never seemed to get all the way to lowest tick.

    I kept driving and it seemed like everything was normal, but then all of the sudden a "problem" icon came up on the screen. Nothing changed in the driving though.

    Couple more stop signs. Kept driving as normal, electric motor working and moving car.

    But then I came to a stop at the fourth stop sign and the hybrid battery icon dropped to the first tick and the ICE started again and never shut off.

    However acceleration stayed normal. It never went back to the super slow acceleration I was getting before. It wasn't like the first time I drove it where it wouldn't get up to speed at all.

    When I pulled in the driveway and back to the shop I tried to turn the car off and it wouldn't. Just kept running. I tried about 4 times and then it finally turned off. (I read before that was sometimes a symptom of a bad 12v.)

    I pulled the battery back out and tested it. It was hovering right one the "Good" and "Weak" line.

    I should have tested it right after I charged it and put it back in but I just figured it need a good charge from sitting for so long.

    I can't find a date sticker on this optima so I don't know how old it actually is, and my buddy only had the car a year and never changed it, so I'm guessing its at least a couple years old.

    So anyway, after that word wall.... my main question is, has anybody observed a bad 12v to cause that much of an issue for the hybrid battery?

    Can't decide if I should just I replace the 12v or just charge it again and get set to working on the hybrid?

    I have a bluetooth OBD coming and got a cheap samsung phone to run the Torque program to check the voltage on the hybrid battery.

    If the 12v's for this car weren't so pricey I would just go get a new 12v without asking but I figure I would see what more knowledgeable people think.

    I think I'm going to charge the 12v one more time for a good solid time frame and try again and see if I get the same results.

    Thanks for any help!
     
  2. PriusCamper

    PriusCamper Senior Member

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    Greetings and welcome to Prius Geekery!

    Because the 12v in a Prius doesn't power the engine starter and the HV Battery does, the criminals who bought Optima and moved the manufacturing plant to Mexico turned one of the highest rated batteries of the 1990's into total garbage and they get away with it because in Prius' case the 12v system needs no cold-cranking amps rating and functions much like a back up power supply for your home computer.

    As such, the very best 12v battery you can buy for your Prius is the most common 12v AGM battery for wheelchairs and backup power supplies that they sell at Batteries Plus for ~$140, which is $100 less than auto store battery for Prius. You do have to stop by the hardware store to get some longer bolts and bushings to adapt the terminals to fit these batteries though. But at 55amp hour these batteries are way, way better than anything you'll get an auto parts store.

    As for a new 12v solving your problems, that is possible, but you usually get way more crazy on your dashboard and way more crazy on your OBD2-based apps or Toyota Techstream when that's the case.

    As for the car running ok for a little while, that's most likely the 12v being disconnected for 5 minutes, which clears the codes and resets/reboots the cars system. So it takes a bit of driving for the car to remember it has a bad HV pack, or in some cases it takes the HV battery getting up to 100' degrees before the bad HV symptoms are obvious to the sensors.

    What you're experiencing with the ECU running, or not, or losing power, etc is the computers gradually eliminate your access to HV pack as the pack's conditions worsen till you get to the point you lose use of HV battery entirely because the car is trying to protect itself from further damage. But then just disconnect the 12v battery again and let it all cool down and you can limp down the road a little bit again. But don't do that if you can avoid it. I overheated a pack doing that once.

    As for repairs, first step is eliminating the least expensive fixes for bad hybrid battery symptoms, which is replacing the 12v and making sure the HV battery cooling fan isn't clogged, which is primary cause of over heating in most cars, especially dog owners cause the air intake to the right of the back seat isn't very well filtered.

    Next step is to brush up on high voltage safety protocols and remove HV battery pack (see youtube for that), then pull off the bus bars, which leads to the next least expensive fix, which is the corrosion on the voltage sensors and bus bars.

    Then if that doesn't fix it it's time to do a voltage test on all 28 modules, with less than 0.3v being the most amount of difference between healthy modules. Of course even bad packs will show you positive results, which is why you need to then do a load test on each module, which means connecting the car's headlight bulb to one module for two minutes and record the amount of voltage drop, usually .4volts or less of a drop is common. And usually that's enough to identify a bad module.

    The next step is to buy a used module that's better performing than the existing modules(more on that when you get to that point) and install it. Then go thru a process of battery reconditioning which means using headlight bulb to discharge the battery down deeper and deeper amounts and then recharge with a NiMH smart charger, which are commonly used for charging RC cars and drones. Most of us prefer the Imax SkyRC B6AC V2. Or alternatively, you can do battery reconditioning on the whole pack at once with the pack still in the car via this much more expensive equipment: Prolong® Battery Systems FAQ – Hybrid Automotive

    The re-conditioning discharge numbers for each module by way of electrical engineers at Hybrid Automotive are:

    Stage 1 discharge: 4.8v
    Stage 2 discharge: 3.0v
    Stage 3 discharge: 0.6v

    The benefit of doing reconditioning on each individual module rather than the whole pack is that even the a perfectly matched set of modules will show noticeable variations during the charge and discharge process, which makes the hardest to find bad module identifiable. The concept behind all this is that Prius Batteries function between 60-80% capacity in the car and that lack of full range of use of battery power cause tiny well conducting crystals in the battery cell to grow much larger into crystals that don't conduct as well. Because of this Toyota designed an HV pack to continue to work normally even after it's lost 50% of its capacity. More info on that here:
    BU-807: How to Restore Nickel-based Batteries – Battery University

    Some things to keep in mind is that Toyota and most mechanics won't replace individual modules in an HV because it's too problematic when it comes to having a set of modules match each other well enough when the pack gets up above 100' temp and there's 90+ amps pumping through it. The good news is that, while this is definitely true for early Honda Hybrid packs, there's a high enough of a success rate with Prius packs that just about every major city has a Craig's list mobile service entrepreneur making money rebuilding & swapping out packs, some doing a much more thorough job than others.
     
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  3. Al Bundy

    Al Bundy Member

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    the battery pack is 13 years old and over 200,000 miles.. so that would be the cause of your problems..
    BUT when you first start the car dont try to drive it until the ICE comes on and goes off on its own, if you drive the car before it cycles the charge will drop like a rock also keep the ac/heat off when starting out.. your battery is weak not point in killing it.
    as mentioned you need the correct code scanner to find out whats going on, odds are you have 2 or more weak or leaking module inside the battery pack... if you open it and see "rust" its actually the acid leaking..
    watch a few youtube videos on rebuilding the packs and follow all the safety steps..
    as for the 12 volt take it to a auto parts store and get it load tested..
     
  4. PriusCamper

    PriusCamper Senior Member

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    Oh yeah, I forgot to mention, you can force charge battery by putting car in drive and put foot on the brake while flooring it. But you problems probably won't be fixed by that.
     
  5. sam spade 2

    sam spade 2 Senior Member

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    Maybe. Maybe not.
    Odds are that BOTH batteries are bad.

    But it would be rather foolish to chase any other leads without first replacing the 12 V battery.
    And any AGM battery can be used......as long as it will physically fit in the space, has a similar capacity, and you can "adapt" the posts to what the Prius has on the cables.
     
  6. PriusCamper

    PriusCamper Senior Member

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    Exactly... But Prius doesn't need a battery designed to pump alot of amps to start an engine, it just needs alot of amp hours to last as long as possible, which is why standard wheelchair/backup power supply batteries at 55amp hour or higher is the true geek way to go! :)
     
  7. Skibob

    Skibob Senior Member

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    What you are is a flipper. The bane of every hobby. At least be honest about what you are.
     
  8. Al Bundy

    Al Bundy Member

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    how has the wheel chair battery been working? any issues? thinking of going that route when this yellow top dies
     
  9. sam spade 2

    sam spade 2 Senior Member

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    TOTALLY unnecessary, useless and uncalled for nasty remark.
    Oh, and with no quote, we don't really know WHO it was directed to.

    Not me who has done that.
    Maybe someone who has will respond.
     
    #9 sam spade 2, Oct 9, 2018
    Last edited by a moderator: Oct 11, 2018
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  10. Hx214

    Hx214 New Member

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    Thanks for all the info guys.

    PriusCamper that run down helps.

    I actually watched all the youtube videos prior to picking the car up. I wanted to make sure it was something I could handle. Looks like fun, so I'll be pulling the pack after I make sure I have a strong 12v. I'm going to get that Torque app figured out to get the prius info on the pack to show me the info.

    Is there anything special about the prius headlight? Is it like a Xenox light? If I make the battery drain tool out of one of the old headlights I have laying around that should work right?

    I think that honda battery I have is almost the same dimensions as the Optima I pulled out. I may try to retro fit that in there.

    If I can't has anybody used the BOSCH battery that pep boys sells? I can get one of those for about $140 out the door.
     
  11. Hx214

    Hx214 New Member

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    I take cars nobody wants that are on the way to the smasher and get them back on the road.

    You know what the value of this 13 year old Prius with over 220k miles is here in the salt belt even after I get it running is? Not enough. I have a 05 Scion XB with 330k I saved last month. Put new front bearings in it because I wanted to use my bearing press and welded in new rockers so I could practice. Have about 700 bucks in it. I'd be lucky to sell it for 500. Man what a deal!! I'll drive it for a few months and someone I know will need a work car and it will go to them for peanuts. (BTW..... those little XB's are way cool cars! That little 1.5 liter is about as bulletproof as they come and it feels like you are driving a mini bus!)

    How is a guy with a mechanic hobby suppose to learn anything new if you stick to working on the same 6-8 cars he owns over a lifetime?
     
  12. PriusCamper

    PriusCamper Senior Member

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    Put one in back in 2013, haven't once had an issue, even with headlights or dome light accidentally left on a couple times... Might put it on a trickle charger for the first time soon when I do maintenance on the hybrid battery that has 232K miles. So far no battery problems, just little loss of capacity of HV battery.
     
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  13. Hx214

    Hx214 New Member

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    So I may have located 3 or 4 prius' in a local pull a part type yard.

    My buddy was there the other day and took a picture of a hybrid pack still in one of them (he didn't look at the others). Database for the place says the one with the pack has been there since April. No info on the miles. I can get the pack for under $100.

    Do you think its worth a shot picking up the whole pack and testing it out? Was thinking even if the whole pack tested poorly, do you think after sitting a long time I could still get a few good modules out of it?
     
  14. Hx214

    Hx214 New Member

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    Meh... got skunked... my buddy took a picture of a Gen 1 pack, he thought they were the same. The two gen 2’s they had were both gone.

    Swing and a miss!
     
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  15. Skibob

    Skibob Senior Member

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    Gen 1 packs still use the same type of battery’s inside the pack I think. In case you were thinking of repairing the pack you have.

    Gen II Prius Individual Battery Module Replacement | PriusChat
     
  16. Skibob

    Skibob Senior Member

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    Point taken. My apologies.
     
  17. PriusCamper

    PriusCamper Senior Member

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    You can actually fit a much, much larger battery in that spot if you pull out the battery mounting hardware and replace it with something that holds it in place from up top... As for Torque app, I haven't got it to work and it hasn't been supported/updated since last Spring. And if you're focusing on a the HV pack you'd be better off with Hybrid assistant and Dr. Prius apps... Of course there's like a 5 to 1 ratio of OBD2 readers out there that don't work and myself and many friends have bought several in order to find one that actually has good enough hardware, not to mention free of manufacturing flaws, which seems to be way too common with these things. Here's the best article I've seen on buying one that works: Hybrid battery diagnostic and repair tool for Toyota and Lexus

    As for Bosch, they make some of the best home gardening power tools, but they all run on EU 220V and because of lawsuit happy US folks, they don't even sell the battery powered garden stuff in the US. They make one electric wood chipper that works really well for small projects. If I lived in Europe I'd own a ton of their quality gear!
     
  18. Hx214

    Hx214 New Member

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    Hmm..... I wasn't aware of that. I might give it a shot. I can buy the whole pack for $85 dollars......

    I think repairing my pack is going to be the route I go. At least of the bat just to get it back on the road to check the other systems before I dump to much money into it. If I think I can get 50-70k more out of the car I might spring for all the reconditioning equipment.
     
  19. jerrymildred

    jerrymildred Senior Member

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    Gen 1 cells are the same voltage and there are more of them in the pack than a Gen 2, but they are also much older. For best reliability, get the newest un-rebuilt battery you can get and use all the cells so they are matched.
     
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  20. TMR-JWAP

    TMR-JWAP Senior Member

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    The Gen 1 modules ARE NOT identical to the Gen 2 you need. They are identical in capacity, but not physical dimensions. Nor do they match in how they interlock together.

    Did your friend send you a photo of the serial number sticker from the battery? Sometimes you run into a recently manufactured Gen 1 style battery. The manufacture date can be decoded from the serial number.

    If this is the case, since Gen 1's have 38 modules, you could use 28 to do a complete swap out in your Gen 2. Not the ideal scenario, but it would be a cheap way to freshen it. Also, a full swap out semi-negates the interlock tab difference, except for the outside modules where they meet the clamp end caps. The module mounting holes still align correctly with the base plate, just the module length of a Gen 1 is a bit shorter. The wiring may have a weird little wiggle in it due to the difference in module size but should still work.
     
    #20 TMR-JWAP, Oct 10, 2018
    Last edited: Oct 10, 2018
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