2nd Gen 12 Volt Battery Charging Issue

Lou,

Personally, I see nothing in your posts that "alarm" me about the way the battery and car are performing, but I do wonder about why so many batteries. I actually replace the battery in my parents car every three years just to have 'peace of mind' that they won't end up broken down somewhere because their car wouldn't start. So, in that instance, I have no criteria for battery replacement other than just age. For my own vehicles, I have an electronic battery load tester that I can use to measure actual capacity of the battery. I can use that value to compare to it's 'when new' rating to determine if it warrants replacement.

Do you spend much time in accessory mode (not in "READY')? What criteria are you using to determine the battery needs replacement? What model battery are you using? What's the part number? Is your car an SKS version? Are you using the SKS size battery (larger) or the non-sks battery (smaller)? I've seen SKS equipped cars with the small battery installed for two different reasons. Because it saved a few bucks or it was the only battery available at the time.

 

Ahh, OK that answers two possible concerns (hot temps=no and short trips=probably not).

I drive under both of those conditions and don't get long battery life (3-4 years). The original owner of my gen2 only drove 4-6k miles per year and had three 12v battery replacements at the Toyota dealer. My wife's 2015 Outback does 90 miles per day so no shortage of charge time yet the 12v battery was dead last week during our spring break after sitting unused for 4 straight days. So, I started price shopping now.

I think some of these issues might be vampire power drains that somehow go undetected (no fault codes). Do you have dashcam, GPS, USB device, or similar installed?

 

prius charging takes about 4 hours of driving to charge the 12v. it's more of a maintainer.

 

do my test. lets see what it does under a small load.

 

agree with ed, post #11.

 

Hi Lou,

I'll chip in one more time and refer you back to my post #7 in this thread.

In addition, I'll add a couple more points.

The Optima battery (and I don't understand why it is so popular, other than it is cheaper), is a sub-optimal battery in terms of its capacity. It is rated at 38 Ah vs the OEM Yuasa battery (for SKS) that is rated at 45 Ah (the OEM Yuasa for non-SKS is rated at 35 Ah.) It would seem, from the data when people can be bothered responding, that the Optima battery is often less then fully charged and when (even less often) people do do a charge before installing, these batteries seem to have a higher frequency of not obtaining a full charge voltage of 13.2 V which is what is to be expected of a good quality AGM battery.

The information you have supplied in regards to your charger would indicate your charger is a regular lead/acid (Pb/A) charger as the charged voltage only seems to raised to normal flooded Pb/A batteries, that being 12.9 V. If that is the case, your charger is never going to fully charge your battery, and this fact will and of itself shorten the life span of any Pb/A battery. One significant property of Pb/A batteries is that they do not like being anything other than fully charged. Any length of time in a less than fully charged state will shorten their life, more significantly in proportion to the depth of discharge. Further, after any full discharge event, a Pb/A battery should be immediately charged back to full to lessen the impact of damage. Most people seem to have the attitude that they *might* get onto that in the next month or two. Duh! Then go on to complain their battery doesn't last. Duh! again.

The charging system in the Prius seems to me, from my observations and data I have collected, to be more of a trickle charger. So again, any full discharge event, should be mitigated ASAP by placing the battery on an external charger designed to charge AGM batteries. Relying on the car to charge it will not do, in this circumstance, as it just is too gentle. It would take the car to be in READY (not necessarily being driven) for 16-20 hours to raise the SoC back to full.

Just as some background (I have a volt meter permanently wired and sits on my dash), I never noticed anything other than 14.4 V coming from the DC/DC converter while driving when I still had the original 12 V battery installed some 2.5 years ago (making it some 10 yo) when I first started having 12 V battery issues. When I replaced it (as daily charging showed the old battery was toast, in that it was not holding a charge) with a good quality AGM battery and for the first time I observed something other than 14.4 V. Usually 13.5 V +/- 0.1, and occasionally 13.2 V if I do a long run after a full external charge. I then started to use the volt meter to gauge when to do an external charge (when it stayed on 14.4 V for almost all the time), but got to the point where I just started a routine charge every 2 weeks.

I use a CTEK MX5, which is a fully automatic smart charger with an AGM setting and reverts to a maintenance charger once the battery is fully charged. I don't particularly advocate this brand charger, but they also make a 3.3 A and a 3.5 A model that are cheaper. Further, it comes with a pigtail which I have permanently installed to the battery, which allows quick and easy connect/disconnect to make the charging process easy and hassle free.

My current battery, some 2.5 years on, still is able to achieve 13.2 V+ when fully charged that settles to 12.9 V once the surface charge bleeds off within about 5+ mins.

As a reference point, if I do edthefox's test, car off 12.9 V; headlight on full 12.4 V; and holds 12.4 V for more than 30 min (I was going to see how long it took to drop from 12.4 V, but got bored at 30 mins.) After this 30 min turned the lights off, the voltage bounced back and after 5 mins was at 12.8 V.

In conclusion, I don't see anything particularly of interest, except maybe that 13.8 V is the highest you see the car charging, but then again, if your SoC is 60% or higher this could be reasonable.

I hope something in this post proves to be useful to you.

 

hey lou, my battery was 12.6 this morning, how was yours?

 

I don't know how you are hearing that, 3 years is a short life span IMO, and I don't know how people just accept that as normal. You obviously don't as you are questioning it.

It is good to hear you did charge up the battery before installing and that this battery has never been run flat.

I hope your new charger gives better results. Let us know how you get on.

BTW, nice looking charger with great features.