fjpod
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Re: 12 Volt battery is failing, I'm looking for replacement

Tue Feb 09, 2016 12:37 pm

I recently had to get a new 12 volt for my 6 year old prius. No local parts stores had it in stock. They all wanted to order me a Yellow top battery which was indicated on their computers. They wanted about $75 more than I was able to get it for online. The dealer wanted something like $400 for an OEM...and maybe that was installed, but still. I think I paid about $140 online.

Actually turned out that my old battery was probably still good, because after I installed the new one, I found the overhead dome light on...wife had been in the car the day before. Had I known, I probably would have charged it up and given it a whirl, but I had made that assumption that once a battery is over 5 years old, you might as well replace it.

Be wary of replacing the 12 volt batteries in cars like iMiev and Prius with "bigger" "better" batteries than they came with. This means the car has to supply more electrical charge to keep the 12 volt up to speed...taking away juice from the traction battery. You may not notice it at first, but when that bigger battery starts to decline in 5 years, it will hurt MPGs. (or eMPGs as the case may be).

So I guess what I am trying to say if the iMiev battery is a standard lead/acid battery, I would replace it with such, same size, same specs. The Prius had an AGM battery to start with.

tigger19687
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Re: 12 Volt battery is failing, I'm looking for replacement

Tue Feb 09, 2016 1:04 pm

It looks like the same size I had on my 1100 Motorcycle.

Still looking for a list of other manufacturers that make this battery size. All the other 'books' that cross reference never list the 'i' as a car {rolls eyes}
- Linda
- 2012 Black i-MiEV (the Black jellybean)
- 2006 F-350 Diesel (the Pig)
- 2002 Nissan Sentra (for son, since he killed the Yukon XL )"

kiev
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Re: 12 Volt battery is failing, I'm looking for replacement

Tue Feb 09, 2016 2:08 pm

BMW K-bikes use a big 12V battery, nearly the size of the jellybean's.

So if using a bigger battery puts extra load on the pack, then does using a tiny one put less load?
kiev = kenny's innovative electric vehicle

PV1
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Re: 12 Volt battery is failing, I'm looking for replacement

Tue Feb 09, 2016 2:29 pm

In a way, yes. There are less floating losses with a smaller lead acid battery. It takes less to bring a smaller battery up to system voltage and maintain it.
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Lic
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Re: 12 Volt battery is failing, I'm looking for replacement

Tue Feb 09, 2016 3:58 pm

Guys, dc-dc could provide about 80A current, so any big battery would be charged properly!
I don't see why bigger battery would take much more energy. It will take depends of how battery was discharged before. For battery 35Ah and 50Ah and I-miev consumption - it will be not so big difference, especially that dc-dc is taking all consumption in ready mode.
Better choose it's to use LiFePO4 battery because it shows almost same capacity in discharge and charge mode, so it will take less energy from HV battery.

Aerowhatt
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Re: 12 Volt battery is failing, I'm looking for replacement

Tue Feb 09, 2016 6:33 pm

PV1 wrote:In a way, yes. There are less floating losses with a smaller lead acid battery. It takes less to bring a smaller battery up to system voltage and maintain it.


Yes (mostly), and beyond this an AGM charges more efficiently and has lower standby losses than a standard type flooded battery. A number of AGM batteries will fit in the car but not without some changes here or there. For warranty purposes IMO it has to fit without alteration to the car. But I will definitely be replacing mine with an AGM when the time comes (I'll alter the battery not the car). I had to take the stock battery out to do a good job of filling and checking it when I got the car. Doing that twice a year is not on my preferred approach list!

Aerowhatt
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JoeS
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Re: 12 Volt battery is failing, I'm looking for replacement

Wed Feb 10, 2016 9:58 am

OK, time to beat this topic to death. Let's review our 12v battery - it lives a very benign and happy life, never has the stress of having to provide hundreds of amps starting current as for an ICE. Thermally, it is not sitting next to a high-temperature ICE; however, it is indeed exposed to brutally-cold northern climes.

The 12v battery is fed by a dc-dc converter which provides a constant voltage. I suspect (but have not measured) that this voltage is temperature-compensated. For example, I just measured 14.48vdc when I turned the car on in my 45degF (7.2degC) garage - I had left the door open overnight. Incidentally, our high yesterday was 75degF (23.9degC). 8-)

The 12v battery only provides three lightweight functions:

1) Provides the current to activate the car's systems when the key is turned on (Ready).

2) Provides current to run the various 12v accessories with the key turned to the first notch: radio, fan, dome lights, etc. I measured 9.6A current draw with the fan in the midway position on my SE Premium with nav unit and radio and hard drive running. YMMV.

3) Provides a tiny trickle current to keep the alarm system active when the car is Off. I couldn't measure this with my clamp-on ammeter, but suspect it's under 50ma. Let's see, 30 days idle at 50ma is 30*24*.05= 36Ah … oops, dead battery, so it must be much less than that. I'll measure power-off current draw when I go to replace mine.

As RobertC identified, the battery is BCI Group Size 151R. Mitsubishi calls it a 34B19L(S). From the Yuasa website, this is shown as 33Ah at the standard 20-hour rate (i.e., a constant 33/20=1.65A) before it drops to 10.5vdc, whereas all the BCI ratings use CCA and Reserve Capacity about which we don't care.

For completeness, for the 34B19L(S), Yuasa shows L = 185mm (7.3"), W = 125mm(4.9"), H = 202mm(8"), Overall H = 224mm(8.8")

All right, so what does all this mean? The stock battery size is already excessively-large, IMO, but your usage determines the battery capacity you need. For example, you may wish a higher capacity -

1. If you go away for weeks at a time not using the car and don't plug in a float charger.

2. If you spend a fair amount of time sitting in the car listening to music or with your laptop or other gadgetry plugged into the accessory socket.

I consider the most stressful thing you can do to our 12v battery is to simply leave the car sitting untouched for a few weeks - the gradual battery depletion results in sulphation of the plates which, in turn, never get a chance to recover because the battery never gets an "equalizing" (higher-voltage) charge to clean the plates. Auto dealers murder 12v batteries when the cars sit on their lots untouched for weeks at a time.

Choices -

The car comes with a flooded-lead-acid (FLA) battery. It's advantage is that it is cheap, but the fluid level should be periodically checked and eventually it will result in terminal corrosion and maybe a bit of rust around it due to the acid fumes. Alternative is a 'maintenance free' FLA - I don't even know if one is available in this size range. I personally will not replace my FLA battery with another FLA.

AGM (Absorbed Glass Mat) - this is a sealed battery that is very suitable for this application. Usually, AGMs don't like to see more than 14.4v at room ambient (exceptions being Optima and Odyssey AGMs), but it seems that our dc-dc puts out voltage right at this limit so I don't see a problem.

Gel - also a sealed battery and actually would be very good in this application as Gels do well in deep-cycling which would be the case if the car was left unused for weeks at a time; unfortunately, the traditional Gels don't like to see a voltage much over 13.8v, so I wouldn't put one there. Don't even know if there's anything available in that form factor.

Lithium - sure, you could stick four LiFePO4 cells in there - for example, four Headways strapped together or even higher capacity like the 3P4S configuration LOWRACER did (http://myimiev.com/forum/viewtopic.php?p=4035#p4035), and it would work BUT I wouldn't put those in there without an individual-cell BMS. Lead-acid is very abuse-tolerant, whereas Lithium is not. Also, 14.4v from the dc-dc results in 3.6v per cell, which is close to the LiFePO4 upper limit of 3.65v - not good for longevity to keep it that high continuously.

For myself, since I usually put a float charger on my i-MiEV's 12v battery when we go away for a few weeks and I can't recall ever sitting in the car for any amount of time while not charging (the dc-dc is activated when the car charges, so you can run the accessories indefinitely while charging), I'll install a small (much less than 33Ah) inexpensive motorcycle AGM when the time comes. I did that on my Honda Insight a decade ago and it's still going strong.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
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jray3
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Re: 12 Volt battery is failing, I'm looking for replacement

Wed Feb 10, 2016 2:33 pm

Before dropping two Benjamins on an Optima, I'd experiment with a Lithium battery, especially since 18650 and 18500 cells are pretty ubiquitous and affordable. I found 66 new LiFePo4 18500 cells for $33 last week simply because they has a 2012 mfg date. So far, they're testing out good.
2012 i-SE "MR BEAN" 70,000 miles
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2000 Honda Odyssey
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JoeS
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Re: 12 Volt battery is failing, I'm looking for replacement

Wed Feb 10, 2016 3:35 pm

jray3 wrote:Before dropping two Benjamins on an Optima,
I was thinking more along the line of a $25 12Ah battery...
jray3 wrote:I'd experiment with a Lithium battery, especially since 18650 and 18500 cells are pretty ubiquitous and affordable. I found 66 new LiFePo4 18500 cells for $33 last week simply because they has a 2012 mfg date. So far, they're testing out good.
Oooh, at that price worth experimenting. Strap them all in parallel and top balance them (for a few days?) and then put together a 16P4S 20+Ah pack and you're in business with no BMS, at least for a while.:geek:
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

tigger19687
Posts: 535
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Location: Bedford/Concord MA

Re: 12 Volt battery is failing, I'm looking for replacement

Thu Feb 11, 2016 12:34 pm

JoeS wrote:
jray3 wrote:Before dropping two Benjamins on an Optima,
I was thinking more along the line of a $25 12Ah battery...


Yes I was thinking the same.
Or a Motorcycle battery, I just don't know where to find one that will match.... ok ok I am just too lazy to look that hard
- Linda
- 2012 Black i-MiEV (the Black jellybean)
- 2006 F-350 Diesel (the Pig)
- 2002 Nissan Sentra (for son, since he killed the Yukon XL )"

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