At what point during cruising do you decide it's time to turn on the engine and recharge your batteries? (where in the battery life) - and what do you typically charge them up to?
Battery 'Care and Feeding'
- Thread starter JeffThompson
- Start date
There are books written about this subject.
The consensus is to recharge as fully as practicable whenever approaching 50% capacity. Simple answers like this are often misleading given engine alternators can take a very long time to fully recharge so don't goby simple answers if you desire a full understanding of battery care. Buy the book(s).
The consensus is to recharge as fully as practicable whenever approaching 50% capacity. Simple answers like this are often misleading given engine alternators can take a very long time to fully recharge so don't goby simple answers if you desire a full understanding of battery care. Buy the book(s).
My answer to that question is, at every reasonable opportunity. I'm opposed to running the engine at anchor so I will utilize opportunities to motor sail and have the engine help propel the boat as well as charge the batteries. These opportunities show themselves up whenever the boat speed might drop from our target of around 5 knots. Periodically running the engine for a few hours during the day allows us to run refrigeration and maintain adequate state of charge while helping maintain boat speed. Never liked running the engine at anchor without a load besides the waste of fuel.
Why? I get the fuel issue, although there are plenty of arguments about the dollars per kilowatt not being all that different for running a diesel engine with a decent alternator vs. running an electric or diesel generator.
The "don't run your diesel at anchor" theory is much more of an old wives tale than actual fact. I started a conversation about this here a couple years ago. This is what Maine Sail had to add to that discussion:
Just passing along some info.
Good luck and fair winds,
Jesse
If you are worried about charge add a solar panel into the mix. I did a 100 watt solar panel upgrade this year. It will cost about $350 but it is so worth it for the panel and the MPPT charge controller.
As others have said, don't discharge below 50% of the battery's capacity. Good advice if you know the battery's capacity and if you know how much current you have drawn.
The current (pun intended) state of the art in battery current measurement is a Balmar Smart Gauge. You can read about it here: http://www.pbase.com/mainecruising/smart_gauge
Whether or not running a diesel (or generator) in an anchorage is damaging to your diesel, sitting downwind in an anchorage when someone is running their diesel to simply charge the batteries is annoying, both because of the noise and the exhaust gas. The easy solution is to use less energy. Other solutions include reducing energy consumption (use LEDs), increase battery capacity, or add additional charging options such as solar or wind.
Don't be a noisy smelly neighbor in an anchorage.
The current (pun intended) state of the art in battery current measurement is a Balmar Smart Gauge. You can read about it here: http://www.pbase.com/mainecruising/smart_gauge
Whether or not running a diesel (or generator) in an anchorage is damaging to your diesel, sitting downwind in an anchorage when someone is running their diesel to simply charge the batteries is annoying, both because of the noise and the exhaust gas. The easy solution is to use less energy. Other solutions include reducing energy consumption (use LEDs), increase battery capacity, or add additional charging options such as solar or wind.
Don't be a noisy smelly neighbor in an anchorage.
If you are using a known accurate volt meter then you will want to start charging when your batteries, at your average house loads, dip to 12.2V - 12.1V. (this is a very broad generalization and depends upon many factors but 12.1V - 12.2V will keep you safe.
You will want to charge as long as you can, within good reason, especially if using the engine or genset because you hit a point of diminishing returns.
To fully charge a lead acid battery takes 8-10+ hours and this is with a healthy charge current.. To get from 50% SOC to 80-85% SOC can be done in a few hours and this is often called the "cruisers rule" of battery cycling. It is fine for a few days at a time but do get back to 100% as often as you can.
Ideally you want to charge the batteries to full as often as is humanly possible. Partial state of charge use is very abusive for batteries. The sooner you charge back to 100% SOC, after deep discharges, the longer your batteries will last.
Without knowing what type of batteries you have, or what you usage is, or what your charge sources consist of, it is tough to lay out a best course of action other than to say get them as full as you can as often as you can.
Best Practices
- Use smart chargers (not all "smart chargers" are actually "smart")
- Use temp compensated charging
- Wire the batteries properly
- Do not install batteries in an engine space or other area that can regularly get hot.
- Do not regularly discharge below 50% SOC.
- The shallower you discharge the longer the batteries will last
- Use one big house bank not two split banks
- Get the batteries full as often as possible
- Use the highest allowable charge voltage setting from your battery manufacturer
- If you have flooded batteries check electrolyte & specific gravity
- If you have flooded batteries equalize them when needed
- Know your correct state of charge at all times, even if this means investing in a battery-monitoring device. It will help in overall cycle life.
- If you are using voltage to determine state of charge, be sure you are getting it as accurate as possible. (this is not easy for most boat owners to do)
A small maintenance item that can help prolong
battery life is to keep the top of the battery free of dust build up. This practice comes from car care which is more critical due to cars being in a dustier environment but it applies to any battery. Accumulated dust can sometimes be enough to create a circuit and slowly discharge a battery. I clean the tops of my batteries as part of a periodic maintenance with a damp paper towel followed by a dry one. Handle paper towels carefully and wash hands afterward as there could possibly be residual acid from seepage.
battery life is to keep the top of the battery free of dust build up. This practice comes from car care which is more critical due to cars being in a dustier environment but it applies to any battery. Accumulated dust can sometimes be enough to create a circuit and slowly discharge a battery. I clean the tops of my batteries as part of a periodic maintenance with a damp paper towel followed by a dry one. Handle paper towels carefully and wash hands afterward as there could possibly be residual acid from seepage.