Battery maintainer...again.

oldmakooldmako Registered Users Posts: 27 ✭✭
A few years ago I dipped in here to ask a few Qs.   You guys were GREAT.   In short, I wanted info on placing a panel on the top of my boat for one purpose, to maintain my batteries year-round since I don't have an onboard battery charger and I don't have electricity to run one.

Fast forward to today...I just bought a newer boat.  It has two crankers (I think) and one deep-cycle house battery.  I want to maintain ALL of them.  And if that's not possible, the two crankers.

I used a Stellavolta https://www.stellavolta.com/Morningstar-SunSaver-Solar-Controller-SS-10-12V.htm controller based upon your recommendations.   I used two 10 AMP circuit breakers to control the flow of current.

I want to do it all over again for my new boat.

Any recommendation on what panel to use?  I am happy to reinstall the controller listed above.  It's been great.   My old was 100W.  It now looks as though the same panel puts out 200W.  Is that correct?

Thanks for all  your help way back when, and again.


Comments

  • mike95490mike95490 Solar Expert Posts: 8,978 ✭✭✭✭✭
    oldmako said:
    .......
    Any recommendation on what panel to use?  I am happy to reinstall the controller listed above.  It's been great.   My old was 100W.  It now looks as though the same panel puts out 200W.  Is that correct?
    Can't possibly be correct.   10 years ago PV panels ran around 20% efficient   Now the good ones are 25% efficient.  For the same size panel, only a small amount of wattage gain likley,  maybe 110W instead of the 100w
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    Do you have any loads (like a bilge pump)?

    In general, you would want around 1% to 2% rate (minimum) for float charging... The older/hotter the batteries are, the larger the array should be (new/cold batteries, less self discharge. Old and/or Hot batteries, more self discharge).

    For example, if you have a 100 AH @ 24 volt battery:
    • 100 AH capacity * 28 volts floating * 1/0.77 panel+controller derating * 0.01 rate of charge = 36 Watt panel/array minimum
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    No loads.  Boat lives on a trailer in a sunny spot.  No AC elec avail, so I want to keep those expensive batts charged up.   Especially in the winter months when the boat sits.

    Can anyone recommend a decent panel?   The rest I think  I can figure out.
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    edited September 5 #5
    https://www.amazon.com/Renogy-Monocrystalline-Solar-Compact-Design/dp/B07GF5JY35/ref=sxin_2_ac_d_rm?ac_md=0-0-c29sYXIgcGFuZWw%3D-ac_d_rm&cv_ct_cx=solar+panel&dchild=1&keywords=solar+panel&pd_rd_i=B07GF5JY35&pd_rd_r=b3f44948-67d6-463e-852e-35c9c050f3f0&pd_rd_w=JVSDy&pd_rd_wg=soJzk&pf_rd_p=c21000ce-3f0e-4b5a-be89-1520c0b89442&pf_rd_r=5GJBDJG5NGEKT4B9KVDZ&psc=1&qid=1599312362&sr=1-1-12d4272d-8adb-4121-8624-135149aa9081



    This is the same panel I used on my previous boat.   I used a Morningstar SS-10 12V Sun Saver Controller and two Marine 10A CB's for ease of switching.

    This system worked great.  But that was a few years ago.   I'm curious if Amazons price is good and or of there might be a better panel for my needs.    Thanks.

    The boat has 3 batts.   Two crankers and one house.  I am primarily interested in charging the two crankers and letting the alternators take care of the house once the engines are started.    Can I run two leads off the Morningstar's posts to the two batteries, one each POS and one each NEG?   I think they are parallel systems since I only have one ENGINE batter switch and one HOUSE switch.   Or will combining the two crankers mess things up?
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    Any silicon (mono or poly) crystalline solar panel with a glass front should be a good start.

    Don't get flexible or semi-flexible panels unless you have no other choice. Flex panels typically only last a few years (or even months sometimes).

    If glass panels cannot (or should not) be mounted permanently--Then temporary mounting when on trailer, and remove when in water is an option.

    How long can you go with out charging... At ~75F, about 1 month between charging is maximum for flooded cell lead acid batteries. If they were AGM or GEL type, about 6 months. If Li Ion, then no float charging really needed...

    That is assuming you have zero loads on batteries while dry docked. Generally a really good idea to turn off breakers/pull fuses for all DC loads to make sure batteries are not depleted (even small loads can kill a bank in storage pretty quickly).

    Note that "heat" is a battery killer. For every 10C/18F over ~25C/75F, the batteries will age 2x faster. If stored at 93F on average, they will also discharge ~2x faster (i.e., 2 weeks between charge for FLA, and ~3 months between charging for AGM).

    So, whether house or cranking batteries--You really need to keep them floating (if FLA and/or stored hot).

    You do have a bit of room to play--If you have PWM type charge controllers, you can use 1 panel and "share it" between the 2-3 charge controllers (as long as the panel has enough wattage to float all 3 battery banks).

    MPPT type charge controllers cannot share 1 array between 2 or more MPPT charge controllers.

    In theory, you can connect two (or three) battery banks in parallel to charge (assuming same or very similar battery types--Such as all FLA deep cycle batteries). If you do interconnect the battery banks for parallel float charging, have a fuse/circuit breaker between each bank in the positive wire just to make sure that a short circuit does not overheat the interconnect and start a fire.

    The downside with paralleling, a single fault (vampire load, etc.) on any one bank could kill all the batteries while you are gone.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    edited September 5 #7
    Thanks, Bill.   Let me try and clarify for you.   You're light years ahead of me so forgive me if I ask stupid questions.   I'll try and address your comments in order.

    I'm not getting a flexible panel.  I used the above mentioned (Renogy 100W Glass) panel last time and was planning on using one again unless someone had a better suggestion.  It will be permanently mounted on the top of the boat's T-Top.   I mounted it using cushioned feet since the motion of the boat smashing about in rough water would be a problem. 

    I also mounted one edge using casement window hinges so I could raise the panel in winter to more directly face the sun.     I live in Virginia and the boat is parked and lives on a trailer pointing south.    

    The boat has zero loads when parked.   

    I just got it this week and I am not intimately familiar with the battery set up other than as described above.     Namely two switches, one for the two crankers and one for the house.   This strikes me as odd and as you mentioned a recipe for disaster.   The manual suggests combining the 3 batts ONLY when you can't get the engine started.   If each engine only charges its respective batt than I don't understand the set up.   Once I pull the panel and peer behind it I might understand more.

    IF I wanted to charge them independently off the solar panel, would I need two controllers, one per battery or is there a controller available that is capable of charging two batts off a single panel?  

    My last boat had 2 switches and 2 batts.  I left both in ALL and wired it that way so the whole system just though it was one big battery.    
    Thank you for your time and info.
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    If you mount on on a hinge... Make sure that the rest of the panel is well supported (wind/vibration/pounding of boat on waves, etc.). There is the option of mounting the hinge directly the panel frame, or building a frame with hinge, and mounting the panel(s) to the frame. The subframe does not flex--Mounting hinge/support(s) to panels themselves, do run risk of flexing the panels.

    Ideally, panels should be mounted to a frame (with hinge) vs using the panel's aluminum frame itself (usually violates warranty).

    Solar Panels are much cheaper these days--And if the panels are stiff enough for you--The risk of panel damage vs simplicity may be worth it to you.

    I am not saying that paralleling all batteries is the worst thing in the world... And as long as you have zero loads on the battery bank--Chances of a single battery or other fault taking out all batteries is relatively low (risk does rise as batteries age/towards end of life and sometimes, batteries die from a shorted cell--Which discharges the rest of the bank(s)).

    Generally, the heavy cables are from the local battery to the local starter... If you combine other batteries, then you may have higher current draw from alternator charging both banks running on one engine, etc...

    My other guess--The idea is you have a pair of redundant systems (engines, batteries, alternators). If you run isolated--If one or the other engine does not start, battery goes dead, etc., you still have a spare. If you run combined all the time, at the point your batteries/altenrators fail, you have no clue until everything is dead--And you have no spare/backup.

    Connecting all two or three banks together (temporarily) with fuses/breakers--Can use one charge controller to charge all thee banks at once (assuming all batteries are same type, all charged or roughly same state of charge). There is a down side in that if one bank is well discharged (say your house battery) and you connect to the other fully charged batteries, you could have fairly high current flow from full to empty battery bank--Needing heavier cabling or popping the fuse during transfer.

    The reality, with float charging--All batteries should be near full when prepping for storage. You don't want try and charge a discharged battery bank at 1 or 2% rated current/capacity. To recharge low state of charge battery banks, you really need 5% to 10%+ rate of charge for proper charging.

    There is, at lease, one PWM solar controller that can charge two batteries at once (intended for vans and boats with both house and starting batteries):

    https://www.solar-electric.com/modubachco251.html

    There are two (major) types of solar charge controllers.

    PWM (pulse width modulation) controllers are "simple" on/off switches (power transistors) (between solar panel and battery). Nothing fancy. Usually more cost effective for smaller systems (and simplier/less expensive controllers). Also a single solar panel/small array can connect to 1/2/3 PWM controllers (one larger panel, splits charging power to all three controllers/battery banks). May be a good way of using one or several 140 Watt "12 volt" solar panel(s) for floating all 3x PWM controllers + 3x battery banks.

    MPPT (Maximum Power Point Tracking). A more expensive controller that is "buck mode switching power supply". Designed for larger (and cheaper) solar power systems and systems that are spread out (between solar array and battery charger/bank). The big advantage is you can use large format (200-350+ Watt, Vmp~3040+ volts) panels and efficiently down convert to your 12 volt battery bank. However, each controller must have its own panel. 3x battery banks, 3x panels/arrays, 3x MPPT charge controllers. May not be cost effective (and probably not needed) for your boat setup.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    Thanks for all the info, Bill.   

    The next step is for me to figure out how the three batts are wired.   I can't wrap my head around the two switches (ENGINES, HOUSE) with three batts.   The crankers must be wired in parallel but until I physically how things were done at the factory I won't know how to proceed.   It may be they use some high-end wizardry to protect the two batts from one another, but I don't know.   I bought a used boat and there's no telling what might be in the battery box.

    Last boat had one 100W panel, one controller running current to one of the two batts.   The charging current was shunted to the other battery through the 1-2-ALL-OFF switch position.  I just left both of the switches in ALL.

    As of this AM, I am leaning toward a larger panel (150W) and the dual controller you posted above.    One charging channel to the HOUSE batt and the other channel to the two crankers.




  • mcgivormcgivor Solar Expert Posts: 3,502 ✭✭✭✭✭
    An opinion, keep the two systems seperate, remember you can't get out and push start a boat.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    In looking at the Yamaha engine manual, they show two crankers and one house battery, just as my boat is equipped.   They do not however, show the batt switches.     The three batts are connected as follows:

    L engine POS to L Batt POS - Cranker
    R engine POS to R Batt POS - Cranker

    L engine NEG to L Batt NEG
    R engine NEG to R Batt NEG

    But then there is one lead from each engine to the House Batt POS terminal labeled "Isolator leads with circuit protection"

    I assume that this charges the House batt once certain conditions are met.  I think it will only provide charging once the two house batts reach a specific level of charge.

    But there is a provision in the BOAT manual that says the Batt switches have a combined setting and that is is only to be used when you're having trouble starting the engine.  By this, I assume that one or both engine batts are discharged to a level that the engine won't crank and start.

    It looks as though any attempt to charge the two engine batts from the solar panel will combine them, unless I use separate switches and manually shunt the current L and R.    Or, use the panel and dual-mode controller to just maintain the two crankers independently and let the house batt charge up during normal engine operation only.
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    It sounds like the house battery is charged using a battery isolator... You probably need to see what kind it is (relay, diode, etc.). And figure out under what conditions it does charge. For example you may see the battery isolators charge if the cranking batteries are >~13.8 volts... But if they are at 13.5 volts (float charging), the isolator(s) may not charge (guessing, an example).

    Also, probably do not want to "ignore" the house battery when in storage... There is a good chance that it will self discharge inside of 1 month or so and start to sulfate.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,502 ✭✭✭✭✭
    Each engine has its own starting battery and alternator by the description. The thing to avoid is providing a means for one battery circuit from dischargeing another, Yamaha has probably thought the out and wired accordingly using the isolator. 

    One means to avoid potential problems is to treat each battery as an independent by using 3 small panels of around 20W, this would be enough to maintain the charge and use a small controller on each such as this https://www.amazon.com/Battery-Tender-021-1162-Charger-Controller/dp/B004Q820UK/ref=pd_sim_nf_86_1/133-5496520-0446739?_encoding=UTF8&pd_rd_i=B004Q820UK&pd_rd_r=d3990bba-11bd-4ed4-8c65-1fbbec3eaf3e&pd_rd_w=USmx1&pd_rd_wg=wPAPb&pf_rd_p=10308ef8-ff5b-4c31-97a7-90e892c6cc39&pf_rd_r=9FXJ00M786KDYQ94BPBJ&psc=1&refRID=9FXJ00M786KDYQ94BPBJ
    This would leave the factory wiring intact, it may cost a little extra but it would be the simplest most reliable way in my opinion, Volkswagen used to, or still may do this with a 13W panel plugged into the cigarette lighter socket for when the cars were in storage lots, they didn't use a controller, just a diode as the small panel wasn't capable of overcharging the battery.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    Specification of a 2002 VW trickle charging solar panel (no charge controller, I believe--Just small enough that it does not damage the battery from "overcharging"):

    https://community.cartalk.com/t/solar-powered-vw-battery-charger/68591
    max power 3.2 watts
    voltage @ max = 18.8
    current @ max = 170mA
    sn ico915687
    1000 w/m2
    am1.5
    25 C cell temp
    Just enough to keep a car's battery "happy" while sitting in the storage yard before sales. (numbers seem reasonable)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,502 ✭✭✭✭✭
    BB. said:
    Specification of a 2002 VW trickle charging solar panel (no charge controller, I believe--Just small enough that it does not damage the battery from "overcharging"):

    https://community.cartalk.com/t/solar-powered-vw-battery-charger/68591
    max power 3.2 watts
    voltage @ max = 18.8
    current @ max = 170mA
    sn ico915687
    1000 w/m2
    am1.5
    25 C cell temp
    Just enough to keep a car's battery "happy" while sitting in the storage yard before sales. (numbers seem reasonable)

    -Bill
    The one I had, image below, was 13W if memory serves me correctly, that was over 15 years ago they probably found it was excessive ?  Someone is selling them on ebay https://www.ebay.com/itm/Car-Battery-Solar-Panel-Trickle-Charger-VW-Volkswagen-1CO915687/401933761188?hash=item5d951e7aa4:g:rQ8AAOSwqK1dsjpJ&redirect=mobile

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    Can you power two controllers from a single panel?   I could get the dual-channel controller for the 2 crankers and a single for the house.   Keep everybody happy.   Say a 150W panel?   And in this manner, all the batts would still be isolated from one another.

    I could just start with a larger panel and have fewer holes to drill in the top.  
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    With PWM controllers, yes you can share one array with multiple controllers. Even though, in theory, the 2 or 3 controllers would be taking 1/n faction of the panel current--In reality, you need dto make sure that each controller can manage the full 150 Watt panel by itself (one battery needing charging, and the other X batteries are full).

    With MPPT controllers, they cannot sure a single panel/array. Each controller assumes it has full control of the array Vmp/Imp, and multiple controllers would just "confuse" each other as they try to figure out the array's Vmp/Imp operating point.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    Wow.  Great input.  Thanks.
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    There may be another "hidden" gotcha.

    With PWM contorllers, there are those with a common negative connection (switching is in the positive side of the controller). And there are others that have a common positive connection, and switch in the negative lead.

    To be honest, I don't really know if there is a issue with mixing positive and negative common PWM controllers... But I would suggest staying with the same or similar brands and models.

    In general, I would suggest that you use a negative common connected PWM controller (most common), and connect all of the battery negative buses together. That should help protect the PWM charge controllers from passing high current through the negative ground when starting the engine.

    Even if you do not purchase the Morningstar dual battery solar charger--Reading the manual should be helpful in avoiding any "trip hazards".

    https://www.solar-electric.com/lib/wind-sun/SSD-manual.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,502 ✭✭✭✭✭
    Morningstar support will answer questions about their products, they respond promptly and are extremely helpful.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    edited September 14 #21
    Thank you!  The first thing I need to do is determine a pathway for the wires from the panel.   Suffice it to say, it won't be easy and I don't what it to look like hell.  I'll need to drill some holes through heavy gauge piping under the T Top.   It's a nice boat and I want to keep it nice.   Once I am sure that I can get this critical step done, I'll start shopping.

    My current thinking is to find one big powerful panel.   Or two, one large (for the crankers) and one smaller, for the house.   If one panel, I'd like to run one wire to the two controllers.  One controller will be a dual-channel for the two crankers and the second a single for the house.

    Would anyone care to opine on the size (watts) that I should consider as a minimum or anything else I have overlooked or are just to stupid to realize?   Type slowly.  I'm that guy.
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    Minimum panel sizing for float applications would be in the 1% to 2% range of battery capacity.

    For example, say you have 110 AH @ 12 volt cranking batteries. Since you are using a dual battery charge controller, then 2x batteries in parallel for array sizing:
    • Assume panels are Vmp~17.5 volts
    • 2 * 110 AH = 220 AH for "both cranking batteries" combined
    • 220 AH * 1% (0.01) = 2.2 Amps minimum
    • 220 AH * 2% = 4.4 Amps sort of max needed for floating
    • 2.2 amps * 17.5 volts Vmp = 38.5 Watt panel suggested minimum (1% float)
    • 4.4 amps * 17.5 volts Vmp = 77 Watt panel suggested "nominal float (2% float)
    Similar for house battery... Say you use 2x 6 volt @ 200 AH batteries in series for 12 volts @ 200 AH
    • 200 AH * 1% = 2 amps min float
    • 200 AH * 2% = 4 amps nominal float
    • 2 amps * 17.5 volts Vmp =  35 Watts suggested minimum Float panel
    • 4 amps * 17.5 volts Vmp = 70 Watts suggested nominal Float panel
    Numbers are approximate (as all solar numbers are--within 10% is pretty much "the same" in solar).

    For example, based on my "fictional" battery banks, your house battery is ~2x larger than a single starting battery. And there for, you could use "pairs of panels" in the ~40-80 Watt range very nicely (and matched panels will probably look better on your boat).

    There is really no "maximum" panel size (other than the maximum Array rating for the various PWM solar chargers you will be using). When you are in the 5%+ rate of charge--You are entering standard solar charging rates for a weekend cabin (and maybe too large of panels/arrays for your boat?).

    If you have lightning in the area--You may want to look at surge suppressors for your array wiring... Don't want to bring lightning into your boat's electrical system (lightning and surge suppressors are a science with boats needing lots of research--Not a trivial subject).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    Thanks Bill.   I'll go through all this and come up with a plan.   As mentioned, the panel and controller set up on my last boat worked great.   All from advice on this forum, 4 years ago.   Great forum!
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    I am very happy to read your kind comments.

    That is what we all try for here.

    Let us know what you end up doing, and how it all works out.

    Bill "closing the loop" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    edited September 19 #25
    One last question before I proceed...Sorry.  I am as smart as used coffee grounds.

    Do you recommend using one high-power panel and splitting the output to two controllers or using two, lower-power panels, one for each controller?   If I am going to go through all this, I may as well take care of all three batts.  The boat sits a LOT from October to April and batts are expensive these days.

    I have the room on the top.   As of now, I think I'm best off using two controllers.  One dual-mode for the crankers and one for the single house battery.   But from an installation standpoint, one panel would be easier than two.   The last one was 100W and took care of two crankers which were wired in parallel using a single controller.
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    It is difficult to find "12 volt panels" (Vmp~18 volts) that are much over 140 Watts--There can be a couple, but you have to look around and have a bit of luck.

    All things being equal--I probably would go with 2x ~100-140 Watt panels. One panel to the starting batteries (with a dual output controller), and a second panel+controller to the house battery. That way, if something fails, you still have a backup.

    And, it works well if, for example, your house battery is ~2x the AH rating of the starting batteries (2x larger battery bank, 2x larger panel for float charging).

    You could do it another way... One starting battery + one house battery. And the second panel+controller charging the 2nd starting battery--If you are looking for true redundancy (two engines, two independent charging sources).

    But in this case, since this is pretty much for float charging in storage--It is not like a dual failure will leave you floating in the ocean.

    I would not over think this... Keep it simple is generally a good starting point. Easier to maintain and easier to debug if something happens.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2littleharbor2 Solar Expert Posts: 1,547 ✭✭✭✭
    There's one USA mfg. who produces up to 210 watt, high quality 12 volt panels. He can be found on eBay Seller name is fred480v

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • oldmakooldmako Registered Users Posts: 27 ✭✭
    Thanks to everyone who opined and helped.   I can't wait to dig into this.  I'll sleep well at night knowing that it's taking care of the batts and ensuring that when I want to head offshore that the Batts will be up to the task after sitting.   
  • BB.BB. Super Moderators, Administrators Posts: 30,964 admin
    And use a voltmeter once in a while on the battery buses to ensure that all is working as expected (holding float voltage during the day, or not dropping much below 12.7 volts at night, etc.).

    More or less, since you have "matched" systems (at least on the engine sides), you are looking for something different. Could be too low of voltage, or even too high of voltage--Anything that indicated further debugging is needed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oldmakooldmako Registered Users Posts: 27 ✭✭
    edited September 20 #30
    I always like to keep tabs with a VM reading at the battery.   For example, my engine panel at the helm reads Volts, as do the electronics once they are up and running (The GPS, the Sonar, etc).   The difference between the V at the battery and at the helm prior to starting has been significant on each of my last two boats.   Once I figured out that 12.2 / 12.3 at the helm actually meant 12.5 / 12.6 at the batteries I could relax a bit.   Of course, the V available at the starter motor is what really matters.    Since this boat is brand new (to me anyway) and since the batteries are somewhat difficult to access, it behooves me to figure out what type of a baseline voltage I will enjoy after sitting a week or three.    With luck (and proper planning and installation), this ought to end any charging issues I have until the batteries have reached the natural end of their lives.  

    Oddly enough, a lot of the boaters around here replace their batts every TWO years and seem to subscribe to that idiotic routine.  I have never gotten less than 5 years out of a boat battery and I don't plan on lowering my expectations when a decent deep cycle battery is over 150 bucks.  I will happily throw a few hundred bucks into a reasonably fail-safe solar battery maintainer set up.   Especially since I do not have AC power available to keep them charged.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,547 ✭✭✭✭
    "oldmako said:
    .  Oddly enough, a lot of the boaters around here replace their batts every TWO years and seem to subscribe to that idiotic routine.
    Goes to show that some people have more dollars than cents ( sense)

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

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