Re: [Cal_Boats] Serious battery question

Fin, Did you get my first response? I never saw it come out of the group. Reacting to your "...only concerned about the alternator...." comment, I don't think you are going to be able to get a meaningful answer without examining the specifications for your specific alternator. Early alternators with external electromechanical regulators are very different from newer alternators with built-in regulators and automotive units are very different from marine. Some are rated for continuous duty and some are not. On the other hand, if you don't change your consumption significantly, just want some more margin, then you would be generating the same amount of energy (WH) with two batteries as with one, just putting it back into two batteries rather than one. If you suddenly started taking week-long trips and only recharging at the same voltage level, then you would be replacing twice the energy and the alternator specifications would come into play. Sorry to not be of much help, but I think you are asking a pretty specific question without enough data to generate an answer. Al --- On Fri, 9/24/10, Fin Beven <fi… [at] msn.com> wrote: From: Fin Beven <fi… [at] msn.com> Subject: Re: [Cal_Boats] Serious battery question To: Ca… [at] yahoogroups.com Date: Friday, September 24, 2010, 11:03 PM The only "weak link" I'm concerned about is the alternator. Does anyone know, with certainty, what could happen with a 60 amp alternator confronted with two (or three or four) 4-D batteries, with an initial voltage at 11.8 volts, when the alternator starts charging. Should this be a problem ? Could this be a problem ? Can this scenario "over extend" what the alternator should be able to do, and potentially causing the alternator to over-heat and possibly fail. The real questions is: Is there "science" on this ?? Fin. From: Allen Edwards To: Ca… [at] yahoogroups.com Sent: Friday, September 24, 2010 2:59 PM Subject: Re: [Cal_Boats] Serious battery question It won't hurt the batteries to charge them slowly and they will get to full charge as long as you have more than the self drain current into the battery. I also doubt you will hurt the alternator. You are unlikely to run your engine for the many hours required to charge them up anyway. Have you considered an ice chest instead of a refrigerator? A block of ice will last longer than what you need. then you won't need any more batteries. Allen On Fri, Sep 24, 2010 at 10:07 AM, Fin Beven <fi… [at] msn.com> wrote: On Radiant, I have the following: 1. Group 31 starting battery 2. 4-D house battery (160 Ah) 3. 60 Amp alternator 4. 20 Amp shore-power charger My primary power consumption goes to the refrigeration and stereo, but I like to feel free to leave lights on when I want to, and I don't like LED lights except for navigation lights. My typical summer trip is 2 - 3 days at Catalina. 4 days sometimes. Because I keep my boat in a slip, I have virtually unlimited charging capacity prior to leaving. My goal is to go as long as possible without having to start the engine to charge batteries. Obviously, the more battery storage capacity you have, the longer you can go without recharging. I could easily add another 4-D battery, in my bilge, so the weight would not be particularly detrimental. (2 batteries, 320 Ah) Here's my question: given the 60 amp alternator, is there a known limit to the number of batteries (or total amperage) it can re-charge SAFELY, assuming I would let the voltage of both house batteries drop to 11.8 volts before re-charging, or simply starting the engine to go home after a weekend. Any wisdom on this would be appreciated. Fin Beven Cal-40 #24 Radiant San Pedro, CA

My preference is to monitor battery charging and load state with a voltmeter. I replaced the ammeter and associated problematic wiring. Lots of IR losses. When charging Vb is typ 13,6-13,9v. Note automotive systems typically rum 14-14.5v. The voltmeter also serves as a great batt 2 monitor when under sail. Bob Virgalla Cell:203.733.5006 On Sep 25, 2010, at 18:53, roline <ro… [at] charter.net> wrote: I was lucky to find a used 80 amp alternator for the 2GM20 on Silverswan, it was a fleebay gamble, but was as advertied. The original was a 35 amp and it was quickly replaced with a 50 that is now the spare. The 80 amp will put out 80 amps for over a couple hrs as the batteries take a charge. I have 2 110amphr agm's for the house and a agm for the starting batt. When we have overnighters we spare no power, refrigerator, blender, lights and loud music.... need to run the engine 2-3hrs over 1500rpm to charge her back up.. Rule of thumb is no more than 100amps per single belt.. ti… [at] ch2m.com wrote: Fin, Here are a couple of tools I use. The Excel File calculates your loading, and gives data as to how to size your battery bank and charging regimen. The link below gives a rule of thumb on alternator sizing, and info on installing alternator and support systems.

I use a 500 amp shunt to prevent the voltage drop issue, no problem with the wiring....and use a volt meter on each battery bank to keep an eye on the charge... Bob Virgalla wrote: > > My preference is to monitor battery charging and load state with a > voltmeter. I replaced the ammeter and associated problematic wiring. > Lots of IR losses. > > When charging Vb is typ 13,6-13,9v. Note automotive systems typically > rum 14-14.5v. The voltmeter also serves as a great batt 2 monitor when > under sail. > > Bob Virgalla > Cell:203.733.5006 > Sent from my iPhone > > On Sep 25, 2010, at 18:53, roline <ro… [at] charter.net > <mailto:ro… [at] charter.net>> wrote: > >> I was lucky to find a used 80 amp alternator for the 2GM20 on >> Silverswan, it was a fleebay gamble, but was as advertied. The >> original was a 35 amp and it was quickly replaced with a 50 that is >> now the spare. The 80 amp will put out 80 amps for over a couple hrs >> as the batteries take a charge. I have 2 110amphr agm's for the >> house and a agm for the starting batt. When we have overnighters we >> spare no power, refrigerator, blender, lights and loud music.... >> need to run the engine 2-3hrs over 1500rpm to charge her back up.. >> Rule of thumb is no more than 100amps per single belt.. >> >> >> >> ti… [at] ch2m.com <mailto:ti… [at] ch2m.com> wrote: >> >>> >>> >>> Fin, >>> >>> >>> >>> Here are a couple of tools I use. >>> >>> >>> >>> The Excel File calculates your loading, and gives data as to how to >>> size your battery bank and charging regimen. >>> >>> >>> >>> The link below gives a rule of thumb on alternator sizing, and info >>> on installing alternator and support systems. >>> >>> >>> >>> From my experience, >>> >>> >>> >>> · expect an alternator to output @ 2/3rds OF ITs RATED >>> OUTPUT for the first 10-20 minutes, then it will taper off after that. >>> >>> >>> >>> · Once the amount of discharge amp hours is within the rated >>> amp output of your alternator, the alternator will output ½ of the >>> remaining charge to allow for plate absorption. >>> >>> >>> >>> · Alternators hold their higher charging output longer if >>> you put a load on it beyond charging batteries, like running a water >>> maker, possibly a refrigerator. >>> >>> >>> >>> >>> >>> http://www.pkys.com/alternator_installation.htm >>> >>> From Peter Kennedy’s web site”When considering an alternator size >>> you can apply a simple rule: the alternator output in amps >>> multiplied by 4 should match the size of the battery banks in amp >>> hours. So a 70 amp alternator would work well with a 280 amp hour >>> battery bank. This is a very general rule so don’t worry if you >>> bank rating exactly. If your alternator is too big it won’t hurt >>> anything but it may not be able to work at its full potential. If >>> your alternator is too small it will just take a bit longer to >>> charge the bank fully. “ >>> >>> >>> >>> From: Ca… [at] yahoogroups.com <mailto:Ca… [at] yahoogroups.com> >>> [mailto:Ca… [at] yahoogroups.com] On Behalf Of Fin Beven >>> Sent: Friday, September 24, 2010 10:07 AM >>> To: Ca… [at] yahoogroups.com <mailto:Ca… [at] yahoogroups.com> >>> Subject: [Cal_Boats] Serious battery question >>> >>> >>> >>> >>> >>> On Radiant, I have the following: >>> >>> >>> >>> 1. Group 31 starting battery >>> >>> 2. 4-D house battery (160 Ah) >>> >>> 3. 60 Amp alternator >>> >>> 4. 20 Amp shore-power charger >>> >>> >>> >>> My primary power consumption goes to the refrigeration and stereo, >>> but I like to feel free to leave lights on when I want to, and I >>> don't like LED lights except for navigation lights. >>> >>> >>> >>> My typical summer trip is 2 - 3 days at Catalina. 4 days sometimes. >>> >>> >>> >>> Because I keep my boat in a slip, I have virtually unlimited >>> charging capacity prior to leaving. >>> >>> >>> >>> My goal is to go as long as possible without having to start the >>> engine to charge batteries. >>> >>> >>> >>> Obviously, the more battery storage capacity you have, the longer >>> you can go without recharging. >>> >>> >>> >>> I could easily add another 4-D battery, in my bilge, so the weight >>> would not be particularly detrimental. (2 batteries, 320 Ah) >>> >>> >>> >>> Here's my question: given the 60 amp alternator, is there a known >>> limit to the number of batteries (or total amperage) it can >>> re-charge SAFELY, assuming I would let the voltage of both house >>> batteries drop to 11.8 volts before re-charging, or simply starting >>> the engine to go home after a weekend. >>> >>> >>> >>> Any wisdom on this would be appreciated. >>> >>> >>> >>> Fin Beven >>> >>> Cal-40 #24 >>> >>> Radiant >>> >>> San Pedro, CA >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >> > >