I addressed this with a 25a dc:dc charger, works great with my 50a hitachi alternator And despite the nominal rating difference it wouldn’t surprise me if I was actually charging more quickly and efficiently than before. I do believe that the alternator will see less short term heat rise and may see less triggering of its thermal protective circuit. (Which limits its ability to charge a deep cycle bank, well documented on marinehowto.com) I never confirmed this but maybe one day I will, provided I have absolutely nothing better to do. (Lol) The “sacrifice” is that I don’t take full advantage of the 200ah lithium bank’s rapid charge potential, but this is academic in my case.
Dave Sent from my iPhone > On May 28, 2022, at 8:41 AM, Joe Della Barba via CnC-List > <cnc-list@cnc-list.com> wrote: > > > Yes there is. > If you connect an alternator straight to a lithium bank and the BMS opens, > you are likely to blow the diodes at best or do a lot of damage with a > voltage spike at worst. Besides for that, since lithium batteries can accept > a high rate of charge for a long time, they look like a dead short more or > less to a small alternator. > Since the charging profile for lithium is different than any lead battery > including the fact all lead batteries should have temperature compensated > charging parameters and lithium does not do this, to correctly charge lead > batteries and lithium batteries from the same alternator, there is going to > have to be a DC-DC charger in there somewhere that uses the correct > parameters for the bank it is charging, either lead>lithium or lithium>lead. > In my case with a 60 amp alternator on an Atomic 4, I believe my best plan is > to charge the start battery and use DC-DC for the lithium bank. > See > https://www.moyermarineforum.com/forums/attachment.php?attachmentid=16228&stc=1&d=1651155864 > > * the A4 is a special case for charging. The pulley that drives the > alternator is small, so the alternator spins slower than on almost any other > engine. Max current at low RPMs is hell on alternators, that makes them run > hot with less cooling air from the slower turning fan. Even with a 120 amp > alternator on the engine and loading up with a hair dryer that sucks 90 amps, > I have never seen more than 45-50 amps from any alternator. > > I could mess around with my regulator and set it up for lithium, the temp > sensor on the alternator should cause it to back off when very hot, but that > still doesn’t solve the BMS issue and I still need to charge the start bank > somehow. > > > Joe Della Barba > Coquina C&C 35 MK I > Kent Island MD USA > > > From: David Risch via CnC-List <cnc-list@cnc-list.com> > Sent: Friday, May 27, 2022 1:46 PM > To: Stus-List <cnc-list@cnc-list.com> > Cc: David Risch <davidrisc...@msn.com> > Subject: Stus-List Re: [EXTERNAL] Re: Batteries again > > Joe, > > We charge house then, a via “Digital Duo”, the start battery. That seems to > be the norm DC to DC. Any reason you are doing it otherwise? > > From: Della Barba, Joe via CnC-List <cnc-list@cnc-list.com> > Sent: Friday, May 27, 2022 11:14 AM > To: Stus-List <cnc-list@cnc-list.com> > Cc: Della Barba, Joe <joe.della.ba...@ssa.gov> > Subject: Stus-List Re: [EXTERNAL] Re: Batteries again > > My batteries are pretty well shot, so this is all good info for me as well. I > always liked gels myself, but they are getting pretty hard to find now. > I have been getting pretty tempted to go for a 300ah lithium, it will fit > right in and give me a TON more amp-hours. If I go that way I am going to > swap the alternator cable to the start battery and use a DC-DC charger for > the house bank. One perhaps not appreciated feature of lithium batteries is > that they are “stiff”, you maintain around 12.8 volts most of the way to > being dead. Wednesday morning I went to check into the Waterway Net and the > SSB wasn’t real happy to be seeing 12.4 volts, this would not be an issue > with a lithium bank unless it was down to its very last bit of juice. > > Joe > Coquina > > From: Korbey Hunt via CnC-List <cnc-list@cnc-list.com> > Sent: Thursday, May 26, 2022 11:12 PM > To: Stus-List <cnc-list@cnc-list.com> > Cc: j...@dellabarba.com; Korbey Hunt <kampf2...@hotmail.com> > Subject: [EXTERNAL] Stus-List Re: Batteries again > > I highly recommend Lifeline group 31 > > Get Outlook for Android > From: Joe Della Barba via CnC-List <cnc-list@cnc-list.com> > Sent: Thursday, May 26, 2022 9:40:31 AM > To: 'Stus-List' <cnc-list@cnc-list.com> > Cc: j...@dellabarba.com <j...@dellabarba.com> > Subject: Stus-List Re: Batteries again > > There is a lot of reason to be concerned about off brands. Pretty much all > cycling batteries of the same size will be about the same AH rating. There is > no magic in lead batteries, the AH per pound is pretty consistent. What > matters *hugely* is the number of cycles that they can endure before being > trashed. The various cheap Chinese imports are highly variable to say the > least, their reviews are all over the place. Lifeline is usually considered > the best AGM maker. > FYI – Deka makes all the West Marine AGMs, you might call around your local > battery shop and see what they charge. They are worse than Lifelines, but if > they crap out after a week at least you can return them to the store 😉 > Joe Della Barba > Coquina C&C 35 MK I > Kent Island MD USA > > > > From: David Knecht via CnC-List <cnc-list@cnc-list.com> > Sent: Thursday, May 26, 2022 11:25 AM > To: CnC CnC discussion list <CnC-List@cnc-list.com> > Cc: David Knecht <davidakne...@gmail.com> > Subject: Stus-List Batteries again > > I have been following the battery discussion and have a question. I need to > replace my two 9 year old AGM batteries this season. I have separate start > and house batteries which can be combined if needed. I don’t have large > power needs (electronics, autopilot and fridge when cruising). I have been > reading and researching this and I am unsure of what to purchase. From what > I have read, AH is the important number to focus on. Last time, I got > Lifeline AGM group 27 from Defender. Defender has 3 different group 27 > batteries > Powertech rated at 92AH which cost about $330 > Lifeline rated at 100AH for 432 > Northstar rated at 92AH for 457 > > From Amazon, I can get a VMAX group 27 with 100AH for $289 or a Universal > with 110 AH for $239. Is there any reason to be concerned about less known > (to me) brands from Amazon or does it make sense to just focus on the > numbers? Thanks- Dave > > S/V Aries > 1990 C&C 34+ > New London, CT > > >
