Dumb alternator question

[KayZee]

My used boat didn't come with any diagrams for the upgrades made over the last 38 years. It does have a Xantrex 30 amp charger for about 100 ah of house and 55ah of starting battery. I, like so many am thinking about upgrading to Li-Po.

In thinking of what it may take to add lithium based amp hours got me to thinking of how they need to be charged and I realized that I don't know if the alternator output goes through the charger or not? If not, is there no "phases" to the charge (from the alternator) or is it only regulated by the rising resistance as the voltage rises in the cells?



TIA for your replies,

Kurt

[Spot]

Hi Kurt,
What other sources of electrical generation do you have:
-solar
-wind
-hydro
-generator
-shore power
-Mr Fusion (spring for the Flux Capacitor)
Knowing this/these may help guide people's responses.

[Off Trail]

I don't know your exact charger but generally speaking a Xantrex 30 amp charger is only for charging the batteries via shore power. Unless you have another external regulator, the alternator is probably directly wired to the batteries in terms of what current/voltage it will deliver.

[KayZee]

Originally Posted by Spot

Hi Kurt,
What other sources of electrical generation do you have:
-solar
-wind
-hydro
-generator
-shore power
-Mr Fusion (spring for the Flux Capacitor)
Knowing this/these may help guide people's responses.

Nothing besides the shore power charger already mentioned. Adding about 200 watts of solar is on the LONG list of maybe upgrades but will probably be about the end of it. It's a 30 footer and my biggest goal is to be able to leave the autopilot on for longer and maybe add a reefer to the ice box.



Kurt

[KayZee]

Originally Posted by Off Trail

I don't know your exact charger but generally speaking a Xantrex 30 amp charger is only for charging the batteries via shore power. Unless you have another external regulator, the alternator is probably directly wired to the batteries in terms of what current/voltage it will deliver.

Thanks for the reply. I don't think there's any other type of regulation or charge control since there's no other charge sources besides the SP and the alternator. Seriously, the boat's wiring is a hella mess. Most of it is neat as in well bundled together and of the right marine type of wire but the bundling is part of the problem. It makes it hard to trace with the shake the wire to see which one moves on the other end trick. Nothing is labled so it's all tracing end to end while wedged between a diesel tank and the sole of the cockpit. A space of about 9 inches.


Kurt



Kurt

[Wotname]

Originally Posted by KayZee

Nothing besides the shore power charger already mentioned. Adding about 200 watts of solar is on the LONG list of maybe upgrades but will probably be about the end of it. It's a 30 footer and my biggest goal is to be able to leave the autopilot on for longer and maybe add a reefer to the ice box.



Kurt

Given what you have posted, the easiest / cheapest / quickest to achieve your goal is to add another house battery (say about 100 ah) in parallel with your existing house battery. If your existing house battery is old and tired, replace it at the same time. Leaving all existing charging systems in place.

Add solar as soon as practical. Depending on your location, it could soon become your major charging source, working silently any time the sun is out.

[KayZee]

Originally Posted by Wotname

Given what you have posted, the easiest / cheapest / quickest to achieve your goal is to add another house battery (say about 100 ah) in parallel with your existing house battery. If your existing house battery is old and tired, replace it at the same time. Leaving all existing charging systems in place.

Add solar as soon as practical. Depending on your location, it could soon become your major charging source, working silently any time the sun is out.

30 foot boat. House is now two AGM group 24 case, 55 ah in parallel. The box they're in is ALMOST big enough for a third which got me thinking about 3 group 20 sized lihtiums at about 50 ah each which would give me 150 true amps to pull out instead of the 50 to 60 that I have now under the no more than 50 percent disharge rule.


Wife is a great and game boat rider. Never sea sick. She crawls into little spaces, is a great problem solver and loves a clean and organized boat. However, she has little patience nor enjoyment for steering. She finds the minutiae of tell tails, stalled and luffing and remembering which way is "up". bothersome and it takes away from her searching for sea life while underway. iOW, I need plenty of reserve amp hours for the AP. Me? I like steering but I also like the idea of having a cube of ice for my scotch when the hook is down or we are safely on the mooring ball.


Kurt




Kurt

[Wotname]

Originally Posted by KayZee

30 foot boat. House is now two AGM group 24 case, 55 ah in parallel. The box they're in is ALMOST big enough for a third which got me thinking about 3 group 20 sized lihtiums at about 50 ah each which would give me 150 true amps to pull out instead of the 50 to 60 that I have now under the no more than 50 percent disharge rule.


Wife is a great and game boat rider. Never sea sick. She crawls into little spaces, is a great problem solver and loves a clean and organized boat. However, she has little patience nor enjoyment for steering. She finds the minutiae of tell tails, stalled and luffing and remembering which way is "up". bothersome and it takes away from her searching for sea life while underway. iOW, I need plenty of reserve amp hours for the AP. Me? I like steering but I also like the idea of having a cube of ice for my scotch when the hook is down or we are safely on the mooring ball.


Kurt




Kurt

I get it. I get the lack of space on 30'. I have only owned small boats (30', 28' & 31'), all narrow beam to boot! I get the challenge of finding space for batteries. But my then wife loved hand steering; would stand at the helm all day if you passed food up the companion way. Exit wife and fitted autopilot!!

Nothing wrong with the lithium concept but you will have to upgrade charging sources.

Last boat I had a single 150 ah AGM for the house and kept sails well trimmed to reduce AP load.

FWIW, I found if I upgraded the scotch, I didn't need ice; just a few drops of water. YMMV.

[glenn.225]

If your batteries are on their way out and you need an interim solution go with a couple of golf cart batteries. Fairly cheap and no need to upgrade your alternator. Trojan are probably is best but there are cheaper ones. Two will give you 100 Ah plus usable and should be lots for steering and a little extra. Will need a charge each day though, maybe some solar.


If you plan on lithium I don't think there is a simple drop-in solution yet but the improvements are coming.

[AKA-None]

Golf cart batteries are going to be physically huge compared to what is there now. Cheapest option if they fit

[Paradox111]

I replaced four 6v lead acid batteries (400ah, 200pounds) only 200ah is usable(50%) with one DIY 200ah LifeP04 battery at 30 pounds.

Adding LITHIUM to your LEAD battery bank
https://youtu.be/tAuPfgZgXec

DIY solar power with Will Prowse

https://www.youtube.com/watch?v=3U4ZfQ_IToI&t=111s

[wholybee]

There is a strong chance that a Lithium upgrade will require replacement of your charger, and modifications or replacement of your alternator system. You really need to think about what you currently have. Get out some paper and start documenting it all. Unless you want to do all of that at once, you could start with those upgrades before you get the Batteries.

For your goal of running your autopilot longer or adding a fridge, solar is the best bang for the buck there. Run both the autopilot and Fridge all day off solar, and only rely on the battery at night. Is there enough room to go from 2 group 24s to two group 27s? I used two 115Ah group 27s before I upgraded to Lithium. At not much bigger, that would be a huge upgrade for you. I now have 300Ah of Lithium in the same spot.