I get new batt. 9/9/21 I test with Romondes 510 12/6/22 down to 83%.15 mo.s old) I charge to 100% in an hr.. THEN I test again 4 mo.s later and it's back down to 84%. again.(19 mo.s old) I didn't recharge. had I known at the time I would have checked with Romondes 510 fresh after install.. it seems to have settled to it's median point of charge. makes me wonder about testing New Battery, makes me wonder about REGISTERING NEW BATT. ! makes me curious

 

"makes me wonder about REGISTERING NEW BATT" -- was the new battery registered at install?

What's the Romondes telling you for SoH (not SoC)?

 

my new batt.(existing batt.) was installed by Mini , I'm sure they know how. SOH was 87% 4 mo.s ago, I didn't look this time , I used my Dongle & Bimmerlink.

 

Then what does your "wonder about REGISTERING NEW BATT. ! makes me curious" mean -- what are you wondering about/asking?

SoH (State of Health) is the measure of your battery's health. In the most relevant terms, SoH is your battery's ability to retain a charge.

SoC (State of Charge) is the measurement shown in Bimmerlink. SoH is pretty much nothing more than "what % of total V is the battery charged up to right now."

Once your battery's SoH is too low, you can still get SoC up pretty high but under load the SoC will drop like a stone. As SoH gets worse, the SoC's baseline will drift lower and lower until there isn't enough retention for the battery to properly do its job.

By my observation on my own car (2017 F56 S) prior to replacing the battery, 84% SoC when all you've been doing is normal use of the car is a sign that things aren't great and you need to test SoH. As you've noted, BimmerLink won't show you SoH. But your Romondes will.

As an example, my old battery (which I still have) can get up to 98% SoC using the Romondes. But its SoH is down below 33% and it won't hold enough of a charge, for long enough, to be used properly by the car. All kinds of electrical weird. I mostly keep that old battery around as a just-in-case-who-knows-maybe-I-can-learn-something-from-it.

 

as of 4/12 my SOC = 81%, SOH = 86%, IBR = 3.6 - I wonder why it dropped charge from 100% to 81% in 4 mo.s ? should I charge or not ? I lap the neighborhood daily to charge. 4mo.s ago SOH = 87% IBR = 3.54

 

Personally, I have some doubts about the car's "braininess" in maintaining the battery charge, and I would put it through a battery charge cycle using the Romondes.

Related "whys" / info in no particular order:

• If you measure with the car off and after surface charge from charging by the alternator has cleared away, (call it 10 minutes sitting after charging has stopped) an AGM battery (which the MINI's is) that is in good condition will have a "normal" voltage at 12.6 - 12.7 volts.
• In my case, this seems to hold -- but at the same time, my SoC on new battery installed in Nov 2022 has been drifting downward (under charging by the alternator). No fancy use, no weird stuff, all past electrical issues chased out of the car.
• I have been checking SoH since I bought the battery (before install). At its highest it was at 99%. Nowadays it doesn't seem to even hit 90%.

The F series MINIs seem to be known to chew batteries in about 3 years and based on the above I can kind of see why. The alternator doesn't charge the battery 100% of the time -- it is controlled by the DME, and there is all sorts of logic being applied to whether/when to charge. Pretty sophisticated stuff and if you monitor certain values real-time using BimmerLink you can actually see it in action. Still, it looks to me -- over the long haul -- like long-term undercharging is a result of whatever logic is being applied.

So at this point my take is to do an actual full charge cycle with the Romondes once in a while, once a month if possible, and at least once a quarter (I know we kicked the "how often" question around once before -- didn't have enough info then for a firm opinion -- now I have a firm opinion). By "full charge cycle" I mean you connect it up and you don't use the car until the Romondes has decided it's done charging (based on observation I think it runs for 12 hours if you let it, and then stops).

Reminders for using the Romondes (or probably any other charger/tester):

- For testing, connect the charger to the starting assist terminals. Those are literally connected directly to the battery. This is critical to get accurate test results.

- For charging, do NOT connect the charger's negative cable to the starting assist terminal. Connect it to the engine block or some other engine or chassis ground. Why? Well, this is some old-school wisdom, but I inadvertently tested this wisdom on my F56 S. I started a charging cycle at night with the Romondes and left the negative cable on the negative starting assist terminal because "duh, forgot." Came back in the morning and found that the car had lost its time/date. Checked Info and Error codes in Bimmerlink and found all these complaints about shutting things down, protecting from overcurrent, you get the idea. Takeaways: (1) My F56 S is ok with the Romondes as charger if following the old school wisdom of having the negative charger cable attached to engine/chassis ground. (2) If I decide to put the negative on the battery/negative starter assist terminal, it's going to trigger a lot of safety shutdowns. (3) I don't want to have to replace anything that a safety shutdown failed to protect, so the rule I follow is "Don't make the car mad. Just connect the negative charger cable to the engine block (for charging) and call it good."

 

I think charging once a 1/4 is a good idea & yes I move the neg. cable to something other than the convenient batt. neg. when charging. for testing o.k. for charging nah, nah, nah ! I wonder why the DME is screwing us ?

 

Dunno. May be some kind of balancing act that is intended to preserve a real-time performance angle, but sacrificing battery longevity as a tradeoff.

Here's an angle, for example, that I really can't quantify: as you increase alternator output (to charge, to power your giant subwoofer, whatever -- it's the total electrical load that counts), you strengthen the magnetic field within the alternator; that in turn causes mechanical resistance to turning the rotor inside the alternator. Since the engine is turning the rotor, that means mechanical resistance (drag) on the engine. Now, how much resistance? Does it matter? The most interesting answer is: I found out about this question by reading BMW-authored documents about its intelligent charging system. So apparently THEY thought it mattered enough to build logic around it to minimize that drag and impact (of whatever amount) on engine performance. That logic is in BMWs (including our MINIs) whose alternators have DME-controlled charging (which is probably BMW manufactured within the last 10 years, if not more).

I wish I could summarize everything I read, there is a LOT going on in these systems. And it really does make a certain amount of basic sense in principle to try to manage the whole thing dynamically. But the upshot in practice in the field is probably that it's like the rest of dealing with the engine on the MINI -- it's cool off the assembly line, but just waiting to be tuned more optimally to make better use of all that mechanical/electrical under the hood, in better ways (towards specific outcomes). Never thought I would crack a joke about an "alternator tune" or a "charging tune" but hey, yino...

 

Unless you live next door to the Nürburgring a lap around the neighborhood is probably not sufficient. When I had a car that didn't like to sit unused for very long I'd drive it 30 miles to work. Mostly at freeway speeds. So the engine ran a good 30 minutes. And the battery was topped up. The 30 mile drive home in the evening was just added insurance...

 

Yeah, I know someone with a 2019 F56S who uses the car for short drives -- about 90% -- and his battery is suffering from lack of charge issues all the time (always shows up when it gets cold, year over year).

In fact, the dealership told them point-blank to "drive the car more" to avoid having the car scream "battery too low" at them every time winter rolls in.

Appreciate your data point there@RockC.

 

So a fully charged battery is about 12.7 volts (2.12 volts/cell) without a load.
When a battery is put on a smart charger, it will top off the battery at about 14.6 volts and hold the "charge" float voltage at around 13.25 ~ 13.33.
A battery at 80% SOC when not charging by either a charger or the vehicle's alternator and without a load will read about 12.42 volts
A healthy battery at 12.42 volts should be sufficiently charged to start a car in all conditions.

I recently purchased a new battery for an older Jag that has fairly heavy parasitic loads from the ancient electrical systems, including stereo memory and the trip computer, and a relay or two that remain engaged when the car is at rest. After installing the battery the voltage read 12.4 volts. I put it on a smart charge at 3 amps for a couple of hours and then started the car and drove it for about half an hour. The next day the battery was at 82% SOC. I put it back on charge and, after 5 hours at the 3 amp setting, the battery showed fully charged. Once the float charger was removed, the voltage on the battery dropped to 12.5 within a few hours.

Battery management is a Dark Art, for sure.

 

on Mimi's it is The Dark Art ! I drive more than around the block.& I don't just putter around. I DRIVE. it only takes an hour to run my Romondes 510, I don't see how it could take a long time but I've only used it a couple times. THAT will increase.I am learning the way.

 

I bought this 2015 F-56 S 5 yr.s old w/ 40.5 K miles on it for $16.6, the first owner leased it for 3 yr.s & put 25K mi. on it. the second owner had it 2yr.s, put 15K mi. on it & threw $20K into Perf. Parts, Lowering Kit,, heavy anti-sway bars, ***** TO THE WALL & sent it to Renn Haus for JCW Brakes & Hot-Tune - water-methanol inj. EVERYTHING ! I Dyno'd at 300 flhp & 247 hp @ wheel . it's a $50+K car w/40K mi. There Is Nothing To Do EXCEPT work out 1 bug. exhaust sys. throwing CELs, I know what to do now, it's just getting it done. That's why #2 owner sold car. Go to Renn Haus of Sarasota website . they do all the Italian Jobbers.

 

The Romondes will definitely get a charge into the battery quickly, but if you let it be it will do its best to actually maximize the charge that gets into and stays in the battery. That takes more time — not because of the charger’s power/whatever or lack thereof, but because as a battery gets closer to full it accepts less charge, more slowly.

If you watch the Romondes you’ll notice that as the battery gets more full, it lowers its amperage output. It will keep changing the output to get as much as it can into the battery, until it hits the end of a predetermined run time, which I believe (based on observation) is 12 hours.

So yep, it’ll definitely do you some good to let it “do its thing” to the extent possible when you do hook it up. 1 hour isn’t worthless, but a longer session definitely has its own value. May also be better for the long term health of the battery, but that’s more dark arts stuff

 

I have noticed the lower amperage output but I think it says DONE ! or I wouldn't disconnect. I will check next time in 2 mo.s ( I'm on the every 1/4 schedule now) do you think I should go to the monthly schedule ?

 

In your shoes I would consider the following two-step approach:

(1) Have the Romondes attempt a repair on the battery -- note that this requires that the battery be *completely* disconnected from the car. 100% should not be attempted with the car attached. This is a pain in the backside, of course, but the point in doing so is to get that SoH up into the 90s rather than at the 86% (and apparently falling, since your SoH prior to that was 87%) level. Why do this? Your battery isn't borderline -- yet -- but it's working its way there. Probably on track for that "MINIs eat batteries in 3 years." Important notes: don't interrupt a repair, and know that it can take a LONG time (I'll do a test run on my old battery and report back how long it took).

(2) With or without item (1), yeah, I would switch to once a month, and again, just let the charging cycle "run until done" each time.

Side note: if the Romondes itself is declaring itself done after only an hour, then you are charging to capacity -- which points at the capacity having been lowered, which points back at item (1).

 

Remember that most wet and agm batteries are rated at 77 or 80 degree F ambient temp. This means, as ambient temp drops, capacity drops as well.

So a 100AH battery that can theoretically provide 100 amps at 77 degrees ambient temperature over a 20 hour period -- meaning if 5 amps/hour are drawn, the battery will theoretically provide 20 continuous hours @ 5 amps/hour until reaching 100% depth of discharge. (100% DoD on a battery reads about 10.6 volts across the terminals with no load.)

It is the rare battery that will ever attain and hold 100% of charge. 100% is the peak charge and diminishes rapidly from there.

Also, desulfating an agm battery is different than doing it to an old school wet cell lead acid battery. Wet lead acid stratification is a different physical and chemical process than the trapped electrolyte in a glass mat battery.

 

Reserve Capacity is another common measure of a battery. Reserve capacity is a number like 120 or 85 or 150 or more.
A battery rated at 120 minutes of reserve capacity, when fully charged and healthy, is, theoretically, able to provide 25 amps of continuous power for 120 minutes before being totally exhausted.

This DOES NOT mean that a 120 minute RC rated battery can deliver 12 volts @ 25 amps for 120 minutes. As discharge time passes, the voltage with drop in a non-linear fashion.

Also, a healthy battery rated at 120 minutes reserve will provide higher amps for a much shorter time period. That's where cold cranking amps come in. A battery that can provide 25 amps continuously for 120 minutes may only be able to provide 600 cranking amps for 30 seconds before the voltage falls off a cliff.

Wheels within wheels.

 

Ah, the dark arts have arrived...

So to contextualize some of the stuff in this thread, the Romondes 510 that OP and I have been back-forthing about is an AGM (and other) battery type-aware charger, and its repair function is a desulfator which, at least according to the product info, is aware of / tuned to these various battery types. In order to test, "repair," or charge, you have to tell the unit what kind of battery it is (better do that accurately, of course) as well as CCA and/or other information -- all in order to make the unit apply the correct approach.

My friend with the 2019 F56S that complains "your battery is toast" every winter -- the first time this happened, he took it to a MINI dealer that somehow resurrected some capacity of the battery, avoiding (at least temporarily) the need to replace. At the time he didn't know what the dealer used and neither did I, but I later deduced that it was probably a desulfator. As the only service he ever does is with the dealer and he bought the car new, safe to assume it was the original battery, which is definitely AGM.

My own experience with my original battery -- which is a genuine BMW installed in my 2017 by my prior owner in 2019 -- was watching the electrical weird kick in in real terms around the following observations made in parallel:

SoC: bottoming out around 84%, able to get it up to 98%, but clearly discharging fast each time
SoH: 29% - 33%, with the top reading after a Romondes repair operation

My friend with the 2019 -- don't know what his SoH was, but his SoC was similarly bottoming out around the 84% mark. My sense is that that's a low-water threshold for "you have trouble brewing or coming" in the F56S -- but in fairness, that's anecdotal rather than something I can prove. I'd bet a slice of pizza on it, but I wouldn't bet the full pizza shop.

A wrinkle in my case, discovered later, was that I had a serious parasitic draw problem in the car, to the point where we almost concluded the alternator needed replacement due to not being able to keep up. By the time I identified that, the battery had already been replaced -- but I still have possession of it.

I've started a repair cycle on the old battery with the Romondes -- have it running right now. It had been been sitting disconnected from everything since November. At repair cycle start, SoH was at 25% and SoC at 98% -- interesting set of readings considering the history.

 

you guys loaded me up, I'm gonna skin it back today & get it ready for early-morning clean tomorrow & let 'er run all day. after that I'll put 'er back together & get ir ready for an early morning start on charge. 3-4 days to do it right & see what happens.

 

Being a retired old man I've got plenty of time & patience to try to work the bugs out. I'M Curious ? How long can you get outa these batt.s over the 3 years & done ?

 

Honestly, don't know. The 3 year thing is anecdotal, but I haven't had my F56S/its battery long enough to tell yet firsthand. Turning off the auto stop/start feature would presumably yield some battery longevity, as starts are the harshest demand placed on the battery by far. But how much and blah blah blah... no idea.

FWIW I put my old battery through some more Romondes repair cycles over the last week or so. That battery's SoH still isn't budging any higher than 29%. Rated CCA * SoH = how much actual CCA you're going to get, so you can see the problem there (and also why the DME will, on its own, effectively disable auto stop/start based on its own monitoring of SoH). So again, while SoC is cool to watch, it's SoH that you're going to care about the most (which periodic full-charging with the Romondes or a similar brainy-about-AGM charger will help).

 

I bought a new battery for another one of my old cars yesterday. Paid $200 for a Die Hard Gold 800CCA with 3 year replacement. The battery I replaced was also a 3 year, and it lasted 40 months, but had a hard life because the car is used infrequently and about a year ago it sat at an upholstery shop for several weeks without a charger on it, which is brutal for sulfating and deterioration. The battery never really came back after that and it limped along for about 15 months more and, this week, it finally would not hold a charge or provide decent cranking amps.

My late neighbor had a battery philosophy that I have decided to adopt. He "rented" his batteries for his vehicles, in that he replaced them every 3 years, whether they were still cranking or not, and he amortized the cost over 36 months, so a $100 battery (the price for a good battery back in the day) cost him about $2.75/month to rent. He never got stuck with a dead battery. Some wisdom there, I think.

 

*Waves magic wand to create confusion in the universe by necroing old thread*

I stumbled into this rather interesting thread off in BMW-land whose opening post is mostly about the different terminals in the BMW (and thereby, MINI) -- but which also has some stuff about how the battery is managed by the DME. Worth keeping, I think.

From that opening post, circa September 2019:

 

Too Much ! I am just a simple man trying to remain that way ! I AM on monthly schedule of chargin' the ol' batt. Takes about 1/2 hr. everthin seems o.k. my IBR seems to be slowly numbering up a little every month but I have reached from 9/21 to 3/24 so far after ignoring batt. for about 1 & 1/2 yr.s. & then de-sulfating & going on mo.ly schedule I FEEL GOOD right now, what can you cast my way in opinion/knowledge ?