after a serious read, I'm glad I break out the old Romondes charger & use that bad-boy once a month. Also glad I de-sulfated @ 18 mo.s One thing I'm curious about is how often one would de-sulfate one's batt. ?

 

Fair question. I was actually wondering the same. I suspect the internal resistance reading you're getting on the Romondes is at least a partial thing to watch as a guide. My most recent is 3.51 megohms. Mid-July it was at 3.46. Late May, readings of 3.47/3.57. My takeaway is that it hovers around that number (in my specific case), usually lower before an in-car charge and higher after, but not "creeping up slowly" or anything. Yet.

My biggest worry about doing the desulfate thing on the regular actually has nothing to do with the Romondes. I'm more concerned about issues with more-routine-than-usual battery reconnection. On the R56 models, arc/spark at the negative battery terminal when reconnecting stood a good chance of blowing out the footwell module aka FRM (I went through that, lots of others went through that, there is finally a recall but no resolution yet, blah blah). The F56 counterpart would be the BDC. Though the BDC is not the same electronics as the R-series FRM, I don't want to find out that if I disconnect and reconnect the battery enough I might tick it off like an R-series FRM. Those things are WAY WAY expensive. I have no proof that I should bother worrying about this, but anyone who blew an FRM will know what I mean about being spooked.

That said, I dunno, maybe once every 6 - 12 months. I installed my current battery in November 2022. Have never desulfated. Internal resistance when brand spanking new was 2.67 megohms.

 

new batt. 9/9/21 on 4/27/23 IBR was 3.6, desulfated recent charge 7/27/23 IBR = 3.41 I look & see & wait

 

Interesting. Looking a bit to me like that 3.4-ish value may be a floor of sorts for us both right now.

I have some work planned on the car where I have to yank the battery to get it out of the way, so I guess I'll plan to do a desulfate cycle. Don't know exactly when I'm going to do that, may be a few weeks, but I will report back before/after values when I do.

 

Good Man, your brand-new IBR was 2.67, was that installed or uninstalled ?

 

That was uninstalled. Took that measurement before the battery saw the inside of the engine bay even once.