12V battery plays big role in mpg

Glad you found the problem. I see you bought the Bosch S4 good choice with a four year guarantee, and less than half the price of the OEM and a quarter of the price of the Optima.

In the US they seem to be the only two choices strangely while here we have a wide choice.

How many miles on your Prius? That service sounds steep or is it London prices. The Toyota web site says £118 for an intermediate service and £180 for the full service, both include materials.

John.

 

John, is Bosch considered a good company? just to try something new I just bought 3 distance plus oil filters from them for my prius, corolla and forester, its pretty expensive but they protect such an expensive component I don't mind paying a little more for more capacity and better product. Is this Bosch battery just a regular one like OEM or is it a deep cycle Marine battery like the optima?

 

OEM 12volt toyota went bad on you?I used a 12volt yellow top optima 51 spiral agm 100 us dollar

 

Bosch products are considered to be of very high quality hear in the UK and the rest of Europe.

The Bosch battery is like the OEM only dependant on model chosen given by the S number, S4 is 4year guarantee with S5 5 year full replacement guarantee.

John.

 

Here in the UK the Optima is way over priced at £184 or over $300. The Bosch is £45 or $75 and the Bosch is 45amp/hr the Optima is I believe 38amp/hr.

 

I couldn't agree more about the importance of a fully function 12v battery, but I see at the site of the battery manufacturer you chose(Bosch, excellent company) that they also sell the optima battery which they describe as an AGM battery which is the most useful thing about the optimas, (they can go in the cabin of an automobile because they don't emit gasses which non AGM, batteries do), but they don't list the S4 as an AGM, nor do they mention that it's a deep cycle battery, which is the other reason to use the Optima, correct me if the info on their web page is incorrect, anyway, just sayin.

 

Yes they are pricy

 

AGM batteries do emit gasses that's why the OEM and Optima for the Prius have a breather vent on the side of the battery. The battery the OP fitted (Bosch) also has this breather vent.

Sealed lead acid and this includes AGM batteries that are sealed, under normal operating conditions do not gas or vent, but may gas if the charge rate is to high.

In the UK there are quite a number of AGM sealed and vented batteries that ARE deep cycle, and have much higher capacity than the Optima at 1/3THRD of the price that fit the Prius.

 

I believe anyone can now copy the Optima design. I believe I once read that the creator was a real genius and patented the idea in the 80's, his patent lasted 25 years but it took him over two decades to perfect and bring his idea to fruition.

Long story short, all his time and efforts and he was only able to corner the market for a few years, now anyone can use that design.

 

I'm not convinced that deep cycle fits the description of the duty cycle of the 12V Prius battery. There's no deep cycling happening at all.

Just saying.

- Chris

 

I disagree. Maybe you have not been around long enough to read about all the deep cycling people put their 12v through.

 

Yeah. Like running electric coolers off the accessory outlet, letting the car turn on and off as it needs to.

And cranking the tunes while parked, waiting for their buddy to finish his shopping.

 

Those tune can be heard inside the store which causes the buddy to hurry thus reducing the depth of discharge.

 

Not so much when the Prius is being driven, but the battery may well see deep cycling if not driven for a week or more with all the "always powered" electronics the car has, slowly discharging the battery.

Because of work load and weather, I have not driven my gen 3 Prius for over 3 weeks. A few days ago, I connected a small (1.3 amp) charger/ maintainer / desulfator to it to top up the battery.
The fact that this little charger took 18 hours to switch from charge to maintain / desulfate, tells me that the 12V battery was more than 50% discharged. Not good, leads to battery plate sulfation.
Fortunatly, the charger has a desulfation feature that can reverse the sulfation damage, although it will do nothing for the deep cycling wear.

 

It is not considered a good idea to use a desulfation type of charger on a Prius unless the battery is disconnected. This is because this type of charger can put out short duration high voltage spikes that may damage the Prius electronic systems.

I have checked two different makes of this type of charger with a scope and found voltage spikes of over 60volts.

 

There are other spiral wound batteries on the market, but one of the drawbacks of this type of construction with multiple cells is it, waste of space between cells. AGM batteries with the same footprint and hight can have nearly twice the capacity in amp/hrs.

I am using a battery that has 55amp/hr capacity at a 10hr rate 60amp/hr at 20hr rate of the same size as the OEM battery, and is a deep cycle battery. It follows that if the Optima was fully discharged (38amps) the battery I am using in the same position would still have 22amp/hr in reserve and would not have been as deeply discharged.

Or put another way take 10amp/hrs out of the two batteries. The Optima would have been cycled 26.3% the battery I am using would be cycled 16.5%, and the less a battery is cycled the longer it's life.

 

Good to know