12v Battery Is Discharging, Re-Charge Now !

Thanks, yeah I’ve had quite a bit of experience with chargers and understand the different levels and prices. Sorry, I should have indicated I was looking at trickle/maintenance chargers. It’s just that I haven’t bought or needed a charger for several years and am not familiar with the current brands. I have seen these 3 brands discussed in some of the threads on here and was just looking for feedback from those with more knowledge of them. Thanks again!

 

I used a CTEK 3300 for years, then switched to CTEK 4.3. They've both seen a lot of use, still using the 4.3 mostly. One thing, the uni-button on the 3300 seems to be getting flakey. But yeah, that's just what I've used. Like them, used to them. Strange though, prices on Amazon seem to have gone through the roof. I got my 4.3 for maybe $89 (CDN), but now they're around $130. Maybe due to COVID, sellers taking advantage??

Even before COVID, our charger is connected to the car more than not, for maybe a couple of years now. No problems.

 

Thanks!

 

I like the “battery tender” brand. It’s been dependable for over 20 years now and it’s still working. I’ve used it on motorhomes, cars, motorbikes and boats over the years.

 

Now on 4th day after a full charge. It is now at 12.60v or 98%. In 24 hour period, it discharged from 12.73v to12.64v, or 0.09v/day. Fairly consistent ~0.1v discharge/day for the first three days. The spike you see on the graph yesterday is from software error when I switched the app version. With this app version, I can export the data to Excel if I want to.

 

does toyota have a spec for quiescent drain?

 

IDK... but if I turn off the smart key, it may limit the drain. For now, I have not switched off anything. The car is just parked not driven, doors not open, no aftermarket electronics other than the Battery Monitor I installed. After this initial 7 days, testing is over, I am going to check to see if I remove the battery monitor, the drain would be substantially less? The spec on the Bluetooth Battery Monitor says the average current is 1mA, but I am not sure what that translates into 12v battery drain.

 

is that an aftermarket product? if so, you definitely want the car stock for these testing purposes

 

Thanks very much!

 

Yeah, I bought it last year thinking to use it on my previous 2017 PRIME after reading so many PRIME 12v battery early demise threads here. But never installed it on 2017 PRIME. I was driving ~30miles daily and I never had any 12v battery problem. Although I did not even take a single measurement on the 12v battery in that car to asses the battery health status.

Now with COVID-19 stay home order, I felt it is a good time to install it on my new 2020 PRIME. There are other battery monitor that use cigarette lighter socket, but that can be seen only after the car starts. With this Battery Monitor II, the voltage can be monitored 24/7. The data for every 2min is kept for 31 days on the unit, and you can access and sync the current and historical data with the phone app.

Bluetooth 4.0 12V Battery Monitor II | MPJA.COM

 

Thanks very much!

One other question. As I believe has been mentioned in either this thread or others in the forum, in the Owner's Manual it says to disconnect the ground cable if the battery is to be recharged while it is installed in the car. I'm not sure of the logic behind this unless there is a chance of some kind of surge from the charger zapping some of the car's electronics. (I'm old school, all of the car repair experience I've had was with non computerized cars and I routinely charged batteries without removing them or disconnecting any cables.)

I really don't want to disconnect the ground cable if it isn't necessary and I know others on here have posted that they routinely charge their 12 volt battery without disconnecting the cable. What is your take on this?

Thanks again!

 

But isn't this 'BT Battery Monitor' just one more thing that draws down the 12V battery while the car is inactive?
The BT receiver and the data gathering and storage function is constantly using 12V power, correct?
It's only going to discharge the battery quicker. Math.

So you walk out to BT distance from the car, connect and download all these 12V data points. Then what?
If it's getting low you either: connect a proper battery charger, or what, go for a pointless drive?

Now wait just a minute,,,, Are you saying that when a Prime is plugged in, L1 or L2, it does not top up the 12V battery at all?

Side note:
I've been using a 2A BatteryMinder with the 'desulfating' routine. It's not cheap. Just connect it and forget about it.

This is anecdotal, (like weird profiteering drug recommendations by,, you know) but, I have been getting great 12 V battery life with all the batteries around the ranch since I've been routinely hanging this charger on each battery for maybe a week at a time, all through the year.

 

Yap, that's the concern. That's why I am going to test how much difference it makes without having BT Battery Monitor as I wrote in my previous comment.

If I am driving every day and plugging in the car everyday, I don't think all of this monitoring is necessary. I never checked on my car before, but I read here that PRIME does charge 12v battery when the car is plugged in. I can check that next time I plug in my car. Right now, I am driving only once a week ~30miles. Then car sit parked for 7 days. I am only charging the traction battery once a week and keeping the SOC at 35%-45% during the week of park.

 

I'm testing it every day. On day 2 it dropped 0.12 volts. I will be taking it for a short drive today so I will test afterward. I will then check tomorrow morning. Once my traction battery needs recharging I'll do a before and after on the 12V to get an idea of the impact on the 12V.
I'm nervous about how low to let the 12V get before connecting my Battery Tender, was considering 11.7. In any case once I have more numbers I will be able to guesstimate how many days I can go without driving before I need to charge. Will probably take a month to figure all this out although I do think the answers will be of value

My Battery Tender is the 1.25 version and has worked well on my Prius V and our Acura TLX, RDX

After looking at Rob's chart I'll stop at 12

 

I can tell you from experience on my 2010 that anything in the 11 volt range won't get it done and causes a TON of weird hard to diagnose nonsensical issues. Tore my hair out for two hours only to discover an 11 something volt 12V battery. No codes were thrown either. Don't go there if you can avoid it. I'll bet the Prime is not much different than my 2010 was in regard to the 12V battery.

 

OK, here is another thing I can check. I could let the 12v battery go down into 11ish volts and see if it starts PRIME or not. At the rate of 0.1v/day, I will be right around 12.0v in 6 days, I can skip using my car this week and let go 14 straight days without driving and charging. That should bring the battery down to 11ish volt.

 

Mmmmmmm, it's my understanding that deep discharge is a no no for these battery's long term health. I'm not sure I'd personally risk it on a new battery just to answer that question.

Now what level is considered deep discharge? I'd have to dig up the research again. I looked all of that up years ago when I was using the 4Runner in high Rockies to power stuff with it not running for short lengths of time.