prv
Well-Known Member
I know, usually we're concerned to get maximum juice into the batteries. But the AGMs I have in mind come with a strict warning not to apply more than 13.8v to them once fully charged, or damage will result. My alternator is specced at 14.2v +/-0.15 (or +/-0.3 without the sense wire), so if I simply connected the alternator to the batteries and then motored to France on a calm day, I'd be doing them no good at all. Given the price of the things, this is not a situation I'm prepared to risk.
For a while it looked like the solution was a Sterling alternator-to-battery charger; Sterling ignored my last email but someone on here told me that the ABC floats at 13.8v regardless of what you put into it.
I phoned Sterling today, to learn that this is incorrect. The ABC is basically a conventional diode splitter plus a "boost" circuit on the domestic leg, after the diode. Once the "boost" program is finished, the clever circuitry switches off and the whole ABC reverts to being a dumb diode splitter. Obviously this will drop some voltage, but the guy on the phone (even after consulting with "the designer", presumably Mr Sterling himself) didn't seem to know exactly how much. He cheerfully opined that it would drop "enough" to keep below the 13.8 even if the alternator's putting in 14.4 - but earlier in the conversation (when he'd mistakenly thought my concern was getting higher voltages, not lower) he'd claimed it "only dropped 0.2 or 0.3", so it sounds like he was telling me whatever he thought I wanted to hear and I don't have much confidence in him.
I've emailed Sterling again, recapping our conversation, clearly setting out the facts, and asking them to confirm their recommendation. So far no reply. I don't know whether they're wary of promising in writing not to boil my batteries, or if they just fail at the 21st century. I suppose I could dig out the quill pen and parchment and send them an actual letter, but I usually only do that with companies with which I am already in dispute, and it seems an ill omen to set out on.
I know I asked about this some weeks ago, but I didn't end up with a workable solution then and I still don't have one now. But the commissioning date is approaching and I need to get something in place.
Maybe I could fit a "smart" regulator which will drop the alternator itself down to 13.8 when charging is complete. But again, the thinking normally seems to be solely about boosting, and it's not clear that these products will reduce the output below what the built-in regulator is calling for. I also have very little space for new boxes in the engine bay. And I would still need some solution to the problem of overcharging the engine starter battery, which is where the ABC originally came into the picture. Trouble is, the ABC doesn't actually seem to be as sophisticated as people like to imagine.
Pete
For a while it looked like the solution was a Sterling alternator-to-battery charger; Sterling ignored my last email but someone on here told me that the ABC floats at 13.8v regardless of what you put into it.
I phoned Sterling today, to learn that this is incorrect. The ABC is basically a conventional diode splitter plus a "boost" circuit on the domestic leg, after the diode. Once the "boost" program is finished, the clever circuitry switches off and the whole ABC reverts to being a dumb diode splitter. Obviously this will drop some voltage, but the guy on the phone (even after consulting with "the designer", presumably Mr Sterling himself) didn't seem to know exactly how much. He cheerfully opined that it would drop "enough" to keep below the 13.8 even if the alternator's putting in 14.4 - but earlier in the conversation (when he'd mistakenly thought my concern was getting higher voltages, not lower) he'd claimed it "only dropped 0.2 or 0.3", so it sounds like he was telling me whatever he thought I wanted to hear and I don't have much confidence in him.
I've emailed Sterling again, recapping our conversation, clearly setting out the facts, and asking them to confirm their recommendation. So far no reply. I don't know whether they're wary of promising in writing not to boil my batteries, or if they just fail at the 21st century. I suppose I could dig out the quill pen and parchment and send them an actual letter, but I usually only do that with companies with which I am already in dispute, and it seems an ill omen to set out on.
I know I asked about this some weeks ago, but I didn't end up with a workable solution then and I still don't have one now. But the commissioning date is approaching and I need to get something in place.
Maybe I could fit a "smart" regulator which will drop the alternator itself down to 13.8 when charging is complete. But again, the thinking normally seems to be solely about boosting, and it's not clear that these products will reduce the output below what the built-in regulator is calling for. I also have very little space for new boxes in the engine bay. And I would still need some solution to the problem of overcharging the engine starter battery, which is where the ABC originally came into the picture. Trouble is, the ABC doesn't actually seem to be as sophisticated as people like to imagine.
Pete
