Aux battery caharging

Both Optimate units (3 and 4) will do the job for a Prius as they are smart chargers with desulfation functions. Stay away from their higher current models as our little 12v batteries will not handle higher charging currents (stay well below 3 amps).

JeffD

 

Put a digital voltmeter across the Aux battery about 6 hours after you've used the car / charged the battery. 12.6 volts is a perfect battery. 11.4v is one that is about to fail.
Lock the car using the key and not the remote 'blipper'. The alarm won't be set and you won't drain the battery so much.

 

My 06 Prius doesn't get driven much (in terms of time per trip) so I'm looking to get a batter maintainer for my Optima Yellow Top. At least now I have a source of constant AC and park inside a garage, unlike when I lived in WA. (I've been disabling SKS to reduce the parasitic drain.)

I'm looking for something relatively cheap and preferably available on Amazon.

I'm hearing about these from this thread, so far:
Batteryminders Specials | BatteryMinders.com
CTEK MXS 4003 (not sure I can buy this in the US, anymore (?))
CTEK 3300
Optimate 3+ and 4

I stumbled across OPTIMA® Chargers Digital 1200 12V Performance Battery Charger and Maintainer :: OPTIMA® Batteries but it's WAY more than I want to spend.

Anything else I should consider?

Some of the warnings at Batteryminders Specials | BatteryMinders.com worry me a little. I'd be charging inside an enclosed 2 car garage. There is a natural gas water heater in the garage in the front and the Prius will be parked so that the 12 volt in the hatch is furthest away from the water heater.

 

Not sure where to start with my series of aux. battery related questions, but.....I recently replaced the original aging 12v battery in my newly acquired 2005 Prius with an Optima yellow top from elearnaid in CA. New battery tested 12.4v outside car, then 12.0 via the monitor. I understand this difference is to be expected, but from what I read/see on youtube the numbers are still a little low esp. when on ACC and IG.
My question really boils down to a couple ok maybe 3 things: 1. does driving the car fairly regularly charge up the battery sufficiently to maintain it or even to desulfonate it (if that applies to the glass mat type battery)? 2. How do you disable the smart key for when it's not driven for a spell, and 3. I live in an off the grid, low power situation at the end of a dirt road, so how else besides a battery tender can I preserve my battery's charge when I may not be able to use it for say 2 months or more (during winter/mud season in Vermont)?

Thanks in advance for any and all advice,
Jon

 

What did your MFD (monitor) show for the voltage when Prius is in ready? If that’s low as well then probably it is just off by that 0.4V.

1. If you drive long enough battery will charge and even desulfate a slightest bit. For Prius it doesn’t really matter if you driving or just standing still 12V battery will charge at same speed anyway.

Maybe something around 1hour of driving for 4 days of sitting is enough to keep the battery charged if smart key system is on and doors are locked. If car sits outside, more in the winter, and less in the summer (battery charging speed depends on battery temperature). If smart key system is off or door aren’t locked then it’s probably more like 1hour of driving for 12 days of sitting.

2. There is a switch under the steering wheel to turn the system off.

3. Only other option is disconnecting the battery. You can disconnect it from the trunk (but then you need to open the hatch from inside to get access to it when connecting it back. Or you can disconnect the battery from the under the hood.

 

12.4 volts for a brand new battery, especially an Optima Yellow Top, seems really low, like you were sold very stale stock. I would try a smart charger session (no more than 3 amp rating), see what the charger comes up with.

For extended idle times, removing the battery (or at least disconnecting the negative cable), coupled with a charge at the outset, and it should be ok for a few months.

I recently replaced a battery, and put the old "dead" one under my workbench. It's been sitting there maybe 3 months now, and when I checked it recently it was reading 12.5 something. My take from this: a connected battery in a car is constantly being taxed by slight voltage drain.

 

Thanks this helps a lot. I am sure I need to do some charging on this battery, because now the sequence on the MFD goes: 11.7, down to 11.4 on ACC, then up to 14.2 on READY. And I've been driving it a good amount. I'll see if it gets any better after the 5 hour drive I'm about to make to see the family, but I might have to fire up the generator when I get home.

Update: After the long trip, the next morning it reads 12.4v, down to 12.1 on ACC. Much better anyway!

 

Thanks. Will do the smart charger thing, and may have to get my $180 back if it doesn't hold the charge.

 

A perfect AGM battery should be over 13 volts. In fact as high as 13.2 volts.
Ordinary flooded lead acid batteries in good condition fully charged should be at 12.8 volts.

John.