2018 Prius C 12V Battery

there have been a lot of problems replacing prius 12 volts over the years. they are always a proprietary size, limiting aftermarket options andoften scarce even at dealers.

definitely one of those issues toyota turns a blind eye to

 

I am sure that it is NOT.
And you are doing all of us a dis-service by cluttering up their system with your personal gripe.

 

No it isn't.....on either count.
As long as a "plug and play" battery is available anywhere, they have met their obligation.
Your unwillingness to USE the right battery is 100% personal.
And if there is any safety concern, YOU are creating it.

 

So.....please refresh my memory with what makes the batteries that ARE available "not correct"?

Taken at face value, I would be pissed too........and would like not to have this problem when my '17 C and my daughters '18 C needs a new 12 V battery.

But having said that, stories like this almost ALWAYS are missing a critical detail.......like "Oh yes, THAT battery will work but I don't like how it fits." or something similar. After all, some people are using wheelchair and lawn mower batteries.

Please keep us updated.

 

The S34B24R battery with date code 140414W on the Prius C failed this past January 20th. The car reached a parking lot, stayed there for about one hour. When wife tried to unlock the doors the car did not respond to the remote. Unlocked the door with the key, tried to start and nada. A while later we jump started the car and drove home. Once the battery was removed, it had a bulge near the negative terminal and the negative post was hot but bearable to my hand. Measuring the S34B20R width at the top and the base, I saw 128mm and 124mm respectively. The height is 199mm.

The Powersoninc website has a tool that allows you to select batteries by dimensions, using 130mm at the width filter on the website selector the PG-12V35 came up. It is a 35Ah 20h rate battery, 10-12 year design life span. I asked several sellers the question: "If I order now, what would be the birth-on date/manufacturing date for the PG12V35 battery I would get at my doorstep?". In my case only one answer was straight forward: 2022-12-28 and I ordered that one. I received one stamped with 2022-12-18, The battery arrived Jan 30th, I am quite happy with how all this is going. The battery has bronze like terminals. The washers and screws are stainless steel, the washers are relatively ticker in comparison to others I have seen. I paid $193.86 including S&H.

The documentation about the battery sprinkles everywhere as much as possible the phrase or equivalent to "Limit initial current to 0.3C", for the 12V35 that's 10.5A, and that's also stamped on the side. After doing a bit of math it sounded like a 0.2 Ohm resistor would be right. I already had a 056777-0840 0.1936 Ohm resistor left over after replacing my auxiliary brake pump on a Gen2. BTW the dealership insisted that it was an updated resistor and I purchased the darn resistor along with new the pump. Since the ABS pump was a package deal the dealership could not check the resistor part number either. And ... nope, what I had was just the same, learned that after breaking an AC grill and removing the dashboard. I am glad I was able to use that money now. Note: With patience you can find the 056777-0840 resistor in eBay for about $10.00 including S&H

Almost everything in the box that the battery came with can be reused: Styrofoam pieces and cardboard. A small thin sheet of Styrofoam was placed in the Prius C metal bottom to lift up the battery a bit. A white Styrofoam piece about 38mm thick was placed on top of the battery and makes the entire "assembly" fit perfectly underneath the seat. The thick Styrofoam piece already has the corners cut out where the posts are. A thin cardboard sheet jackets the battery inside the box, I placed the cardboard shield around the battery when it was placed in the car. I cut out the connector for the 0.1963Ohm resistor, crimped blue ring terminals and with that replaced the negative cable assembly. The battery can be placed in any direction, so considering that the length is 195mm, you could stand it up so now the "new" height is 195mm and the length is now 164mm. In the future I may just go that way, first I need to get to "know" the battery and see if any liquid comes out. I hope the Styrofoam is not going to be a fire hazard in the future lol. From this point of view re-orienting the battery to eliminate the Styrofoam is quite appealing.

For the positive side I decided to simply shave a bit of plastic from the 82164-52160 L shaped 140A fuse holder's bottom side where the pencil terminal used to be. After that the L shape fuse/connector rests perfectly on top the positive terminal. The M6 screw that came with the battery was used. I could have directly connected the aluminum cable terminal and do away with the L-shape fuse/terminal assembly but a fuse may be badly needed in the future, it's just better to leave that fuse in place. Another path is to take out the pencil terminal from the L-shape terminal, add a 5mm metal spacer on top of the positive battery, use a M6 maybe 10mm long and that should work. I did not have 5mm metal spacer, just a grinder =).
BTW, this is the first time that I have seen a battery cable made out of aluminum, the cable is spot welded to the copper ring terminal. I am also tempted to replace the 140A assembly with maybe a 60A fuse. The Gen2 wire has a wire to sense voltage at the positive terminal, that provision is not implemented in the Prius C.

Before I connected the battery for the first time I started to measured voltage drop across the resistor with a Fluke 87 V, it has a very handy function to record Max and Min values. Note: When I say current values from this point on, it's an indirect measure from voltage drop across the 0.1936 Ohm resistor. Anyway, as I connected the positive side a 26+A spike happened!. The ambient temperature was around 10C. A few instants later the auxiliary brake pump came to life and current draw was about 5~6A. From there about 1A was being used. The doors where open, etc, so that seems OK.

Started the car and the initial charging current value was 4.13A. The car was reading 14.43V (excluding resistor) and it jumps around about 0.1 volts. In about 20 minutes the charging current dropped to 0.35A. Powersonic says that at a "cycle voltage" of 14.5~14.8, a C/100 charge current signals a fully charged battery. The "standby-voltage" of 13.5~13.8 should cause the battery to draw only C/1000 once charged according to PS. Called it the day, The recommended charger for this battery keeps a steady 4A charge current, once 14.7 is reached, switches to 13.2 float. This is the first time the battery was charged, when I got it I simply put it aside for a few days.

Next morning decided to drive and see if the usual "HEB trip" was enough to charge the battery. Had to pick groceries so it was just perfect. This time the charging peak current was around 5.1A. About one minute or so after driving I noticed that the current values where jumping from negative to positive every 10 counts or 20 counts. Negative for about 10 counts, positive for about 20 counts. Stopped the car and started to measure voltages while excluding the resistor. The 2014 Prius C starts to cycle the charging voltage as you drive, from ~13.51 for about 10 counts, to ~14.43 for about 20 counts, wash, rinse, repeat. Sometimes braking or accelerating will cause the car to stay a bit longer in either one. Put in park and it definitely stays at 14.43. Got home and simply decided to wait until next morning. Next morning started the car and left it at park, a charging current spike of 4.8A was picked by the 87V max function, in about ~20 minutes it reached the C/100 value. In a month or so will measure once more charging currents & time first thing in the morning.

At this point all seems OK. I think it may be wise to place something that can measure the Ah and keep totals. If anybody has a suggestion, please me know. The budget is 30.00 or less lol.

I do see a need to place a NC relay in series with a Schottky diode to bypass the resistor while the car is off. The aux. break pump does take longer to finish pressuring it's chamber. In the past, unlocking the doors (10A spike) then opening door, getting seated, etc. was enough time for the ABS aux, pump to finish before you even inserted the key (yes, the S34B20R kept powering the pump just fine until it simply failed. The car never signaled a weak battery. I find that just interesting). Now the pump takes about 10~15 seconds to finish. If you start the car while the pump is working, in one or two seconds it finishes. I need to find a good signal source to control the relay. Either the ON or ACC would work, the READY signal would be the holy grail!

I guess one of these days will get the electric diagrams from techinfo. If anybody knows of a nearby connector that can be tapped to get any of those states please share the info! A diode needs be in series with the NC relay contacts to ensure that charging currents only flow trough the resistor. One final note: The resistor feels cold all the time. One way you can feel that there is a temperature difference is by touching anything else metal in the battery compartment and then touch the resistor,

Yup, nothing in this post is endorsed in any way by Toyota =). I am just sharing info related to a bet made, hoping that the PG-12V35 battery has the same value or better as the original YUASA battery.

 

Could you explain what the 0.2 Ohm resistor is for?

In addition, I don't see a fuse holder at the battery terminal of my 2012 Prius C.

 

Purpose of 0.2 Ohm resistor is to ".... limit initial current ..... to less than 10.5A ..... "

Look up part 82164-52160 in eBay. The fuse is part of the assembly and the entire terminal must be replaced if the fuse ever opens. Now that I think about it that part is not a fuse holder in the sense that the fuse is not separate. Your regular fuse holder allows for the removal and insertion of a new fuse as needed. If you just do not have anything like that in your 2012 C it may be a good idea to find a way to add a fuse to the positive terminal.