Bruce, My boatyard says it puts a very heavy load on the alternator to charge both house and starter batteries at the same time using the diesel. Same if you have two house batteries hooked up in parallel. If you've installed a high output alternator on your diesel or have alternate charging methods (shore power battery charger, solar panel, etc.) there's less issue, although I'm of the understanding that batteries being charged together should be the same capacity and relative age.
On my "new boat", it came with 2 group 31 (house) and one group 24 starter. It has a Promarine charger that runs off 110 current. The PO spent most of the time hooked up to shore power and even had a Tenma 12v power source that he could run the 12v circuit when he had access to 110v shore power. I'm going to be on a mooring and I'm being told that unless I can somehow upgrade my charging system, It is a bad idea for me to have two Group 31 batteries in parallel as it will burn out the stock 35A alternator on the Yanmar 3HM. I'm buying new batteries so now is the time for a decision. Will probably go with one Group 31 for the house and one Group 24 for the starter. There's a two battery switch on the bulkhead so I can assume the second Group 31 was wired in parallel on the same switch. I'm trying to avoid turning my lovely Landfall 35 into a Beverly Hillbillies looking stern (my wife insisted we buy davits) by adding wind generators, solar panels along with all the other "essential" debris that clutters up a cruising boat. The boat has 12V refrigeration (OEM Waaco Cold Machine) that would be wonderful to turn on occasionally to keep a few things cold while cruising. Does anyone out there charge a pair of Group 31 batteries using the lower output alternator? Chuck Gilchrest Half Magic 1983 LF 35 Padanaram, MA From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Bruce Pope via CnC-List Sent: Wednesday, April 6, 2016 3:44 PM To: cnc-list@cnc-list.com Cc: Bruce Pope <brucep...@live.ca> Subject: Re: Stus-List Automatic Charging Relay Is it safe to switch between 1-BOTH-2 while the engine is running? I have gotten mixed messages about that. Haven't tried and am starting/charging in the BOTH position assuming therefore that banks are in parallel and both are charging. But, read somewhere that it is bad form to charge different types of batteries (starter/deep cycle house) this way. _____ From: CnC-List <cnc-list-boun...@cnc-list.com <mailto:cnc-list-boun...@cnc-list.com> > on behalf of Josh Muckley via CnC-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > Sent: Tuesday, April 5, 2016 7:58 PM To: C&C List Cc: Josh Muckley Subject: Re: Stus-List Automatic Charging Relay It's not "smart" it always starts charging the "primary" bank first. Once the primary battery is full (ish) it combines the second battery. Josh On Apr 5, 2016 9:50 PM, "John Pennie via CnC-List" <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote: Thanks Gary. I get that and I suppose it certainly simplifies the wiring - you essentially have one bank for charging purposes. No opinion at this point although I do feel silly having spent the last year dutifully switching between 1-both -2. I assume it's just a relay that connects the circuit at a set voltage. Not sure how it can be smart enough to determine which bank to charge first but perhaps they are more than just a relay. John On Apr 5, 2016, at 9:13 PM, Gary Russell via CnC-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote: Hi John, I've had ACRs on my boats for the last 15 years and I think they are one of the best upgrades you can do. When I bought "Kaylarah" (formerly "High Maintenance",adding and ACR was one of my first upgrades. They are usually wired to charge the house bank first, then the start bank. If your start bank was very low, you could could still use a combine switch to get the engine started. I have never had a problem with the ACRs and I can't say the same about a 1-BOTH-2 switch. All you have to do is forget to switch to 1 or 2 after you shut the engine off and you can kill both batteries while sitting on a hook. That won't happen with and ACR. I think you will come to like them. Fair winds, Gary S/V Kaylarah '90 C&C 37+ East Greenwich, RI, USA ~~~~~~~_/)~~~~~~ On Tue, Apr 5, 2016 at 8:38 PM, John Pennie via CnC-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote: So while connecting batteries today i discovered, to my surprise, that Paws has an automatic charging relay between the two battery banks. Yes, I'm still learning this boat. So as I understand it, once voltage hits 13.6 volts (or 13.0 for 2 minutes) the relay will automatically combine the two banks to share the changing source. Not sure how I feel about that. On the plus side, I guess it's great that I don't have to worry about moving a battery selector switch while the engine is running. On the down side - How does a battery charger monitoring two banks handle this? I just seems it has to screw up the logic on the charger. Essentially there is no way to isolate charging? So if I know I only have limited time to charge and want to concentrate on one bank I have no choice? What I missing? John _______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated! _______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated! _______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated!
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