You have two different load requirements. First and most important is when the boat is on the mooring. You'll want the bilge pump to work automatically. That's all. You're not running any other loads when you're not there. 50w is sufficient to keep the batteries topped up and handle the occasional bilge pump. Be aware that 50w panels make ~4.2amps at 12v under perfect conditions. Aim the panel, clean, no shade, high noon, at the equator, no atmospheric blockages. My 100w panels rarely make more than 6amps but are not meeting hardly any of the perfect conditions. If we assume that your 50w will produce 3amps and the batteries are in good condition and the bilge only needs occasionally pumped (no major mast, deck, or shaft seal leaks) then 3 amps will keep up... with little margin. The solar may create current for more than 8 hours and it may exceed 3amps, but for estimating sake lets assume 24 Ah and then round down to 20Ah per day.
Your second load requirement is while sailing/cruising. That's all the rest of the electronics and navigation lights. 50w is a completely insufficient. But... While you're "using" the boat you are also running the engine to get in and out of port (or on and off the hook). The alternator is making up for the used energy at a minimum of 30amps. This is usually very sufficient. Your house battery is ~100Ah and you'll want to avoid discharging it more than 50% (50Ah). Less than 80% full is the only condition in which the alternator will charge at full current so basically 30Ah (50% to 80%) or 1 hour of engine operation, which between coming in and going out is not hard to imagine. The controller you've selected is larger than necessary. Your 50w panel is NEVER going to produce more than 5 amps. The BlueSolar is 3x larger than needed. I would suggest looking a Genasun gv-4. It is appropriately sized for your panel. https://genasun.com/all-products/solar-charge-control lers/for-lead/gv-4-pb-4a-solar-charge-controller/ Genasun has a design heritage from MIT's solar car competition. The gv-4 doesn't use electrolitic capacitors and is built to be marine grade. This makes it ultra reliable. Many of the listers like the echo-charge. I'm sure it is a fine product but I prefer an ACR. The echo-charge is only capable of charging at 15amps max. An ACR will charge at full charge current. The solar, ACR, alternator, and battery charger should all be attached to the starting battery. Once the starting battery has reached its 80% full or greater voltage (~13.3v) the ACR will CONNECT the house battery in parallel with the start battery and continue to charge. This ensures that the most important battery gets charged first and then they both get topped up and maintained equally. The only caveat to the ACR being a "better" option is if you are using different battery chemistries for start and house. But if that was the case then you'd also have to have special charge controllers for your alternator, solar and battery charger. Based on your description I have assumed that you are using standard lead-acid batteries. All of this leaves the DC system vulnerable to a failure of the starting battery. Under this setup there is no way to charge the house without the starting battery and there is probably not already a good way of cross connecting the house and start. The "All" position of Off,1,All,2 switches just connects both batteries together. In a failed battery situation this will draw down and possibly drain the house battery. Don Casey makes a good argument for eliminating the Off,1,All,2 switches which are so popular. He suggests single pole, single throw disconnect switches arranged to separate each battery from their "bus" individually. Then you would use another disconnect switch to cross-tie the busses. https://www.amazon.com/dp/B00445KFZ2/ref=cm_sw_r_cp_apa_eoQ0ybTYDYCR2 In the event of a failure of either your house or starting battery you could use the switches to align your batteries to the appropriate loads. IMO, In this setup you would want your ACR, alternator, charger, and solar all attached to the starting battery BUS instead of the battery itself. Because of the switch setup when/if your start battery failed you would open the start battery disconnect and close the cross tie. All of the charging circuits would now be connected to the house battery with no need to consider how it would be charged. There is some disagreement about which battery should be the "primary" and which should be "secondary". Primary being where all the charging sources come in, secondary being the battery which gets charged by the echo-charge or ACR. Above all, I want my starting battery to get charged. In my mind it is always first. In the attached picture, Don Casey has drawn what I described. The picture I attached shows the starting battery as the secondary and the alternator being directly tied to the house battery - not on a switch. This avoids blowing the alternator diodes should a switch be inadvertently opened during engine operation but doesn't solve the reliability problem in the case of a primary battery failure. I'm not sure that it significantly matters but hopefully someone will chime in on the merits of having the house battery as the "primary" and hopefully also the merits of having the alternator directly connected. Good luck, Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Mar 22, 2017 11:23 AM, "Bruce Whitmore via CnC-List" < [email protected]> wrote: > On our 27 MKIII we mounted a semi flexible pane that could be walked on to > the sliding hatch and tied in a small charge controller and battery > combiner. We kept 2 series 24s and a series 27 charged on a mooring in > Chicago for 10 years this way. It kept the panel out of the way and we > just tied the boom off to one side when we left the boat. > > Kindest Regards, > > Bruce > 847.404.5092 <(847)%20404-5092> > > Please forgive any typos as this was sent from my iPhone. > > On Mar 22, 2017, at 10:37 AM, Edd Schillay via CnC-List < > [email protected]> wrote: > > Tom, > > Sounds like a good system. The only different thing I have in my setup is > a Blue Seas ACR instead of the Echo charger. See: https://www.bluesea.com/ > products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A > > Works VERY well. > > Another factor is the placement of the solar panel. A shadow from a boom > will give you a significant drop in volts. > > Smith sailing to Snow Goose! Rest in Peace Artie Karpf. > > All the best, > > Edd > > > Edd M. Schillay > Starship Enterprise > C&C 37+ | Sail No: NCC-1701-B > City Island, NY > Starship Enterprise's Captain's Log <http://enterpriseb.blogspot.com/> > > > > > > > > > On Mar 22, 2017, at 10:27 AM, Thomas Delaney via CnC-List < > [email protected]> wrote: > > Hi Listers, > > Snow Goose spent the last 20 years docked in a slip with shore power, and > I'm moving her to a mooring. I plan on adding a solar system to recharge my > batteries during the week. > > The boat will primarily be raced/daysailed, and occasionally overnighted, > on the weekends. My power draws are an automatic bilge pump, sailing > instruments, a chart plotter, and the freshwater tank pressure pump. I have > two 79AH Group 24 AGM batteries onboard, one in each bank, wired to a 4 way > selector switch. > > My plan is to install a 50W 12V Monocrystalline Solar Panel connected to a > BlueSolar MPPT 75/15 controller, and connect them to the house battery. I > am planning on installing a Xantrex Echo Charger between the house battery > and the starter battery. > > Does this system make sense? I've read mixed reviews about the Echo > Charger, but I can't find a better way of charging two batteries from a > single panel/MPPT controller. Is there a different setup that makes more > sense? > > Thanks and best, > Tom > > --- > Snow Goose > C&C 35 Mk I > City Island, NY > > _______________________________________________ > > This list is supported by the generous donations of our members. If you > wish to make a contribution to offset our costs, please go to: > https://www.paypal.me/stumurray > > All Contributions are greatly appreciated! > > > _______________________________________________ > > This list is supported by the generous donations of our members. If you > wish to make a contribution to offset our costs, please go to: > https://www.paypal.me/stumurray > > All Contributions are greatly appreciated! > > > _______________________________________________ > > This list is supported by the generous donations of our members. If you > wish to make a contribution to offset our costs, please go to: > https://www.paypal.me/stumurray > > All Contributions are greatly appreciated! > >
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