Which 12v battery is the best?

I need to replace the 12v battery in my '01 but not sure what is the best battery. Should I go with the Exide, Optima or the Toyota? Are there any advantages or dis-advantages to them besides having to use a kit to make the non Toyota batteries fit?
Thanks

I do not think that the Toyota dealer parts counters carry the Classic original equipment GS battery any longer. You'll most likely have to buy the replacement Panasonic battery as well as the battery conversion kit that contains a new battery bracket and cable connectors.

I had installed the Panasonic when I owned my 2001. It is a tight fit into the available space. The trunk trim cover goes over the new battery bracket and bulged out a little.

I think the Optima is a reasonable choice, as long as you are aware of the need to install new battery cable connectors and adjust the battery bracket to fit.

I'm not aware that you can purchase an Exide which is AGM and will fit the available space. Good luck with your choice.

I don't have an Optima in my Prius yet but I use them on other vehicles and they are excellent batteries. The beating they can take is astounding and they last longer than a conventional floodie. Having a deep cycle there would be extra insurance against a door left ajar and the like. It will probably outlast your car.

Gels like the Hawkers are best suited where high current flow is needed which does not apply to the Prius.

There are regular aftermarket batteries that don't need the kit so that's the cheap way to go. That's what is in mine now.

What did you use for an aftermarket battery? The local dealer has an orginal style for $138.

If you are using the word "carry" to mean "keep in stock", then that will be dependent on each dealer's inventory level.

However, the original spec battery is indeed available, although I don't remember whether or not GS Yuasa is the supplier these days.

Some dealers won't know whether or not the battery they are selling is the larger one, and I've seen dealers mistakenly sell the original spec battery as the "upgrade".

Last I checked, the larger battery went for about $200.

Hi,






Installed January, 2009, no problems.



Bob Wilson

The one in mine was installed by the last owner. Brand is Battery direct. part numbers and everything on attached photo.

It is a normal maintenance free flooded lead acid. No kit needed. Don't know the cost.

Group B20L. Ask for this type at your local parts store.

From the last photograph of bwilson4web's modification, it appears that the battery terminals are positioned in such a way that they could both short against the right rear frame rail if the vehicle takes a hard hit to that corner. Vehicle manufacturers normally design battery mounting locations so as to avoid such issues.

In my opinion, that flaw—in addition to the tie wraps, the wooden blocks, the need to fabricate adaptors for the cable connections, and the lack of any significant advantage to this installation—render it undesirable. Unless, of course, it's a temporary fix, and the only choice between walking and driving.

Not everything in the world needs to be redesigned. I'd recommend a Toyota battery.

Yea! You got it right! We'll call the Odyssey battery "temporary". <GRINS>

Bob Wilson

Regarding your handiwork, I didn't say that it was a temporary fix. I only recommended to readers of this forum that such an installation be considered only as a temporary solution. I'm sure you are happy with your work. Proud, even.

And not to put too fine a point on it, but I posted only because I saw multiple problems with your installation, and because I believe the readers of this forum deserve to know about those problems. Remember that the original poster asked for the best solution to 12V battery replacement. In my opinion, your "solution" falls short. If you disagree, please tell the forum why you disagree.

While I have no doubt that you mean well when you post, many of your recent posts have been riddled with misinformation. That in itself is not your fatal flaw; to err is human. And please know that I have not pointed out every error that you have posted; I simply don't have the time to do so.

The problem, as I see it, is that you now seek to impede corrections to those errors. At first, you raised objections to my observations. Yet you have not successfully countered a single one. And lately, rather than acknowledge the misinformation that you have posted, you have resorted to sarcasm and condescension. Not exactly the hallmarks of someone who is seeking knowledge.

With regret, I am forced to conclude that when faced with a choice between (1) providing accurate information to readers of this forum and (2) protecting your ego, ego trumps information.

Why is that?

I ordered the Optima and the install kit last night. My theory was, with the warm weather not to far away, the Prius may sit a few weeks at a time since I ride a motorcycle when it's warm enough and not raining. The Optima sounds like it has the most capacity for when the car sits.

Relax dude, it is only 'temporary.' <GRINS>

After I got the Odessy battery, the first problem was connecting to the existing wires:

The solution was to go to Lowes and buy terminal lugs and #6 gauge wire. Checking the dimensions, the terminals fit well within the recessed gap. But I didn't want to modify the existing battery terminal clamps. Fortunately, I didn't have to.

You'll notice the OEM ground clamp exactly fits the other end of the ground lug:

There is a similar bolt on the 12V terminal so no mods to the existing cables. Just a quick visit to Lowes.

So I'm pretty happy with the installation. The price was right and best of all ... it has worked for over year. <GRINS>

Bob Wilson

So magnanimous of you. From the length of your posts one might assume you do.

Gotta agree there - the exposed terminals are kind of a deal-killer.

Welcome "gray Prius," I didn't know you had an interest in NHW11 Prius:

You'll be happy to learn that it is not forsale. <grins> But let's take a closer look at the shadows of the terminals:

You'll notice the light is such that the near-side of the battery, just under the terminals, the shadows show the terminal bolts have a distinct gap ... an air gap. Although not clear in the photo, the battery case is exceptionally solid.

The risk of 'air gap' insulation is something like a tool falling into the gap. So let's first agree that the near side, ground terminal is not at risk. It is only the far side, B+ terminal that potentially is at risk:

I decided the risks were minimal but folks with a stock installation might be 'concerned.'

This is a stock battery installation:

You'll notice the battery terminals have a shield that protects the terminals. This makes sense because the battery area is separated from trunk cargo by a felt-like, cloth material. This terminal shield prevents cargo shifting from potentially shorting the terminals but my NHW11 is different.

My first modification was to install a 1 kW interverter:

The two-part, mounting consists of a base board shown on the right with a notch for the battery clamp. The baseboard attaches to hinges holding the inverter mounting board and covers the left side of the trunk. It is quite substantial. The whole, left side of the trunk is fully protected from cargo shift:

Compared to the felt-cloth, this mount is very solid and should provide 'life of the vehicle' service.

Not shown, the Odyssey bottom mount although this photo gives a clue:

The bottom width of the Odyssey PC925 battery is all but identical to the width of the OEM battery. This fits exactly in the existing bottom tray so there is no side-to-side 'slop'. This avoids the problem Hobbit had mounting an Odyssey yellow top in his NHW20.

When choosing to replace the OEM battery, several options were considered:
model| $ | criteria
OEM | $200 | First example lasted 6 years
Miata | $200 | Requires adapter and same life as OEM
tractor | $30 | Short design life, 2-3 years
Optima spiral | $200 | Rugged design, larger case, 10 years, heaviest weight
Odyssey | $200 | Rugged, smallest case, 10 years, lightest weight Based upon manufacturer specs and inspection

Both the Optima and Odyssey batteries use a better constructed, dense plate structure. But the Optima uses a cylinder design with empty space between each cell whereas the Odyssey uses prismatic design with no air space. The net effect is the Odyssey will always have the smaller physical package ... and space is important.

One thing I wanted to avoid was making a permanent modification to the vehicle wiring. If I ever decide to sell the car, the buyer could provide an OEM battery and I would keep the Odyssey. So this is why building my adapter from common parts found at Lowes worked so well:


No doubt it could be improved:

• rotate the battery 90 degrees towards the rear - this will raise the height so the 12V terminal has a larger air gap. This orientation will mask the ground terminal but there is no problem with taking the battery in and out with the ground wire attached to the battery. I may have to fabricate longer jumper to the battery terminal block to route around the battery clamp. The longitudal shims will have to changed but Lowes is close. But this can also provides a mount for the 80A circuit breaker I've wanted and space for a stiffener cap.

This 'temporary' installation has worked well since January 2009 and it can be improved. With a higher surge capacity inverter and stiffening cap, this should also improve handling of in-rush loads. But let me point out, it is not forsale ... there is no 'deal' to break.

Bob Wilson

Reworking my Odyssey battery looks very practical with several advantages:


The extra space adds to where I have shim blocks today:


So this means I can add a stiffening capacitor and mount it in the space to the left. A stiffening capacitor will provide

• inverter inrush power - the cap will soften inrush current for the inverter without being limited by either the battery or vehicle inverter supply.
• longer 12V life - by dampening the current draw from every power-on start, the battery won't be as stressed. This should extend the Odyssey battery life.

I'll probably fabricate:

• bottom shim - larger than the current block, it prevents the Odyssey battery from shifting forward and backwards.
• side mount - attached to the bottom shim, it will hold the stiffening capacitor
• top cover - clear plastic, it will have a channel to bring the 12V bus forward to the 12V battery block. The battery block will be mechanically attached to the top cover. It will also mount a 100 A. circuit breaker.

I'll probably put the 100 A circuit breaker between the 12 VDC B+ and the stiffening cap. This will provide short-circuit protection while still letting the stiffening cap provide limited, over voltage to the inverter. Murphy's law says the 100 fusible link will protect the circuit breaker by blowing first.

One thing we'd discussed in the past is a blocking diode so reverse polarity jumps can not blow the rest of the electronics. The usual problem is mounting. This becomes entirely practical with the 12VDC power busses protected.

One other option is mounting a smaller inverter in the new space on the side. My 1 kW, 1.2 kW surge, inverter is bulky but newer inverters might fit in this space. . . . Hummmmm.

Bob Wilson

I dislike long posts myself. Unfortunately, it is often difficult if not impossible to adequately explain why technical information is incorrect, without posting to some length.

But why the attitude? Why the sarcasm? Are you trying to discourage folks from posting accurate information?

EDIT: Honestly, the thread showed up under Prius II main forum (and I think need to replace my 12V since the door doesn't seem to unlock so easily as it used to in terms of sensing the key fob). I saw the pictures and I basically had the visceral reaction of "that can not be safe if someone runs into you"

The design of this battery hookup is inherently more dangerous than stock in the case of a side impact collision due to reliance of air-gap insulation. From my point of view, that disqualifies ('deal breaker') the rig solution from really being as good a solution as a OEM battery from a crash safety standpoint. It has nothing to do with whether you're selling anything or not. A modification to the design by adapting some sort of insulator over the terminals would be a significant improvement. Is it possible to re-use the stock rubber 'mat' so that you aren't so reliant on the air gap that may or may not be there when someone runs into your car?

Yeah, that one was a bit beyond the pale. I wouldn't be surprised to see the photo end up in a "what not to do" presentation.

To bwilson4web's credit, he seems to have backed off from his original presentation of the hack as a solution to the original post: "what's the best 12V battery for a Gen 1 Prius?", and is now singing a different tune.

However, the damage is done: the person asking the question has now purchased a similar battery prior to realizing its inherent drawbacks. Hopefully, that person will read the rest of the thread, and can then decide what to do.

Rotating the battery 90 degrees will increase the air gap. Still, if an accident causes that battery to short out, there will be more severe problems.

I thought about that but the problem is the risk of adding a compression load to the terminal by putting a solid in the air gap. I don't have any problem with stressing the case but the only load I want on the terminals are the connectors and the less the better.

After the battery is rotated, with more clearance, there will be plenty of space for a plastic cover. In sketching out the new orientation, the dimensions for the OEM and Odyssey battery are:
width|length|height|battery
5"|7.5"|8.05" (w/o posts)| OEM battery
4.875"|6.469"|6.875"| PC925L Odyssey
0.125"|1.031"|1.175"| free space* after rotation 90 degrees

So it looks like the B+ will be raised about 0.4", more than enough to clear the frame. I just checked and Odyssey sells Japanese style posts so a battery top Japanese style post(s) will mount the battery terminal block in the original location. Next to find a stiffing cap.

Bob Wilson