Options for Charging batteries while away from the boat OR away from shore power

[Eustace Scrubb]

I'm asking for guidance on how to keep the batteries charged.

Background
We are preparing ourselves to own and maintain our first sailboat (26-28', pull-start outboard engine). I've been researching batteries and battery charging but haven't been able to find an answer to my most basic question: how do we charge our batteries while we are away from shore power OR when we've left the boat in its slip for the week?

Charging While Away From the Boat
I THINK I understand that, if we have shore power at our slip, we can simply plug in a "smart" 3-stage charger and leave it to charge and condition the batteries. If we select a marina that has shore power, that is what we would do during the week while we're gone. BUT, if we don't have have shore power at our slip, we would need to take the batteries home with us. (We used to do that when we owned a tiny travel trailer, using a PulseTech Xtreme XC100 charger at home) We'd rather not do that, as we hope to have two house batteries.

What do you do when you leave the boat for a few weeks at a time during sailing season?

Charging While Away Cruising
Can we bring our Honda eu2000i generator on board with us when we're away long enough to need to recharge the batteries?

Where would you suggest/recommend we store it while we're sailing?

If you would discourage us from doing that, what are our other options? I understand the need for a 3-stage smart charger to ensure the batteries are kept in good condition, but what power source would we use to power the charger itself?

I expect that this is a really, really basic set of questions --- so basic that I haven't found an answer yet! Thanks for any help you can offer.

Regards,
Eustace Scrubb

[btrayfors]

Eustace,

Good questions. There are a few options.

1. (probably the best) - get an appropriately sized solar panel and a good charge controller. These will maintain the battery(ies) automatically, with no intervention needed on your part.

2. get a good 3-stage battery charger and plug it in to shorepower when at dockside. This won't allow you to charge the battery(ies) when underway, however, and there's always the dilemma of whether to leave it plugged in while off the boat or to disconnect it.

3. depending on how you plan to use the boat, get batteries which have a lower self-discharge rate so they can be left for longer periods of time without recharging. AGMs or Gels. Probably, for you gels would be better.

The EU2000i is a great charger (I have a brand new one), but I wouldn't recommend it for this purpose. Takes too long, a lot of trouble to tote and store, etc.

I'm in the DC area, too, and if you wish to discuss give me a buzz. My email is bill at wdsg dot com

Bill
S/V Born Free
Capital Yacht Club

[djmarchand]

Eustace and Btrayfors:

The trick to using the Honda generator is having an appropriately sized shorepower charger to adequately load the Honda but not overload it.

A 40 amp charger (or maybe 50 if it is an efficient one) is about the largest that you can safely power with the 1,600 watt continuous rated EU200i.

David

[David M]

You have a number of options and you can use one or all of them if you wish.

Use your outboards charger. Your outboard can be used to charge your batteries although they generally do not have much charging power at all. It won't hurt to hook it up and put at least some charge on your batteries whenever your outboard is running. It may not keep up with your total energy demand but something is better than not connecting it.

Use a portable generator and connect it to your battery charger through your shore power connector. You can have whatever sized battery charger you want provided your charger comes with the ability to limit the charge rate so you do not exceed your generators maximum continuous power output. Otherwise, your chargers maximum power draw must be less than your generators maximum continuous power output. By how much less you will need to determine. I would give it a conservative 20% difference.

Use a solar charger. They of course don't work at night and their power output is minimal, unless you want to create a large array which on a 26-28 foot boat is not very practical. For day use and weekend use you really don't need one. They are also big, clunky and ugly.

You also have the option of adding larger or more batteries to your boat so that you do not need to charge your batteries as often. The downside is additional weight, additional cost and additional storage volume needed.

[Stu Jackson]

As part of this "decision exercise" you should do an Energy Budget. Energy Budget

While a larger battery bank will allow you stay out longer without recharging and extend the life of your batteries by reducing the daily discharge % (given the same daily load), you eventually have to put it all back.

You choices will in many cases depend on how you intend to use your boat.

Weekends only, one or two nights: size the bank properly to allow you to run for two days (keep the battery bank sized to avoid going below 50% SCO - state of charge; and a solar panel sized properly will get your bank back up during the week while you're away, no shorepower needed. Folks on moorings do this.

Heavy boat use of more than two nights a week regularly - a larger solar panel setup, or add the generator, or stop and plug in for a few hours. Previous suggestions to purchase a quality and good sized charger is very important.

You will, at best, get only 6 amps out of your outboard engine and only at full throttle.

You might want to wander around and read some of the links here:

Electrical Systems 101

Good luck, enjoy your new boat.

[btrayfors]

Originally Posted by djmarchand

Eustace and Btrayfors:

The trick to using the Honda generator is having an appropriately sized shorepower charger to adequately load the Honda but not overload it.

A 40 amp charger (or maybe 50 if it is an efficient one) is about the largest that you can safely power with the 1,600 watt continuous rated EU200i.

David

David,

Yes, you have to size the charger appropriately.

The Honda EU2000i will handle a 75A charger (like the Iota DLS-75 or other), but the size and type of battery bank will determine how fast it will soak up available amperage.

However, IMHO using a generator/battery charger as a primary charging method is not a great idea, because it takes a very long time to reach full charge no matter the size of the charger, and with some batteries reaching a full charge often is important to longevity (expecially AGMs).

With a generator/charger setup -- even a big one -- you're still going to be operating between about 50%-80 or 85% state-of-charge unless you run the generator for many hours.

Bill

[The Garbone]

Solar should do you well.

On our 27 we have 310ah of batteries and a 30watt panel with a charge controller. We recently went for a 2 week cruise and did not need shore power.

We put in all LED bulbs (existing fixtures) and use a handheld VHF to monitor 16/9 and turn on the big VHF only to xmit or if something interesting is going on. We use a oil lamp for ambiance and to save electricity. We used the depth finder and gps as needed, we just did not turn on the stereo, that sucks power.

[David M]

Originally Posted by btrayfors

David,

Yes, you have to size the charger appropriately.

The Honda EU2000i will handle a 75A charger (like the Iota DLS-75 or other), but the size and type of battery bank will determine how fast it will soak up available amperage.

However, IMHO using a generator/battery charger as a primary charging method is not a great idea, because it takes a very long time to reach full charge no matter the size of the charger, and with some batteries reaching a full charge often is important to longevity (expecially AGMs).

With a generator/charger setup -- even a big one -- you're still going to be operating between about 50%-80 or 85% state-of-charge unless you run the generator for many hours.

Bill

Yes, within reason. You don't buy a 100 amp charger for a single Group 24 battery. It is not always necessary to charge batteries up 100% either. In a perfect world yes, but it is not always practical to run your charging source for hours on end to get that last little but of stored energy.

I understand that there is a time element to fully charging a battery.

Most people won't care if your batteries don't last quite as long if this means you have to listen to a generator for hours on end.

If someone wants to run their generator for a half hour and get what stored power they can into their battery in that amount of time then there is no harm in that other than maybe having to buy new batteries a little sooner.

[btrayfors]

Originally Posted by David M

....................
If someone wants to run their generator for a half hour and get what stored power they can into their battery in that amount of time then there is no harm in that.

No, no harm....except for helping to shorten the life of your batteries.

Take this example:

400 amp hour (AH) house bank down to 50% state-of-charge (SOC) after a night's rest.

You have a generator driving a 500 amp charger....essentially an unlimited charging capability.

You run that generator/charger for 1/2 hour.

What's the result?

A flooded battery in good condition will take a maximum of 20-25% of its AH capacity when beginning at 50% SOC. That's 100 amps maximum acceptance by the batteries.

So....you use your 500 amp capacity charger to recharge this battery bank for 1/2 hour.

You will replace 100 amps x 0.5 hours charging = 50AH. Minus the inefficiencies....say 45AH to be generous.

But, your battery is now only at a 60% SOC.

Well, that's something alright. If you're happy with that, then as they say Down Under, "good on ya" :-)

Bill

[Eustace Scrubb]

Thank you all for your input! We certainly had not realized the complexity of using our generator to charge our marine battery (with our travel trailer, it was easy: we plugged the trailer into the generator, ran it for an hour, and the on-board converter re-charged the battery. And of course we took the battery home at the end of each trip).

As we are considering the purchase of a Catalina or an O'Day 27 The Garbone's solution, solar, seems to be a good fit.

Would you give me more information about your system and --- big question! --- about the cost we could expect to incur if we went the solar route? Also, do you worry about theft of your solar panel while the boat is moored at it's slip? If not, why not?

You are an amazingly helpful group! Thanks very much.

[Sailmonkey]

Solar panels are one of the best ways to charge your batteries, and they're relatively cheap!!
In this photo you can see our panels, We've got less than the cost of a decent charger in these plus the controller, and they supplied 99% of our power when cruising. We have a fridge and a watermaker, without either one of these you should have no problem keeping up a battery. Theft has never even crossed my mind, they're bolted down to the dodger frame, so wouldn't be the theft of opportunity sort of things.

[The Garbone]

Originally Posted by Eustace Scrubb

Thank you all for your input! We certainly had not realized the complexity of using our generator to charge our marine battery (with our travel trailer, it was easy: we plugged the trailer into the generator, ran it for an hour, and the on-board converter re-charged the battery. And of course we took the battery home at the end of each trip).

As we are considering the purchase of a Catalina or an O'Day 27 The Garbone's solution, solar, seems to be a good fit.

Would you give me more information about your system and --- big question! --- about the cost we could expect to incur if we went the solar route? Also, do you worry about theft of your solar panel while the boat is moored at it's slip? If not, why not?

You are an amazingly helpful group! Thanks very much.

My mistake. Our panel is only 15watt. I bought it on Amazon since I have Prime (free shipping).

Sunforce 50033 15-Watt Solar Charging Kit : Amazon.com : Automotive

I fabricated the brackets out of some pieces of teak and Magma grill brackets. Actually paid more for the Magma brackets than the panel.

Costs in addition to the panel and brackets would depend on the boat. That particular panel supplies 24vdc to the controller with a 10 foot wire (came in the box) and from the controller the wire is about a 2 foot long (also supplied) and I tied it to the main 12Vdc bus bars.

On my boat I did additional work to balance the draw on the batteries, moved them to help with a listing issue as well as replacing a bad cell, all cost me money. However the panel keeps the batteries topped and does not overcharge them even when we don't make it to the boat for a few weeks. Since we have not paid for shore power since we bought them except for a few nights to run a space heater they have already paid for themselves.

I never really worry about theft. I guess they could be stolen but then again so could the boat. There are padlocks on the cabin and lockers but that only keeps honest people out. 10 seconds with a bolt cutters and they would have a boat.

Our boat also came with a nice big DC to AC converter for running power tools, good for small jobs and cheaper than paying for a hookup.

[David M]

Originally Posted by btrayfors

No, no harm....except for helping to shorten the life of your batteries.

Take this example:

400 amp hour (AH) house bank down to 50% state-of-charge (SOC) after a night's rest.

You have a generator driving a 500 amp charger....essentially an unlimited charging capability.

You run that generator/charger for 1/2 hour.

What's the result?

A flooded battery in good condition will take a maximum of 20-25% of its AH capacity when beginning at 50% SOC. That's 100 amps maximum acceptance by the batteries.

So....you use your 500 amp capacity charger to recharge this battery bank for 1/2 hour.

You will replace 100 amps x 0.5 hours charging = 50AH. Minus the inefficiencies....say 45AH to be generous.

But, your battery is now only at a 60% SOC.

Well, that's something alright. If you're happy with that, then as they say Down Under, "good on ya" :-)

Bill

I already said that.

If nothing else matters but charging your batteries perfectly then go for it. Sometimes though reality gets in the way of doing something perfectly and you just have to be pragmatic about things.

[Zil]

It is hard to understand so many answers that don't answer the question. Solar will work well to maintain your lead acid battery bank while you are away from your vessel. The Honda will work to give your battery bank a topping charge as needed when you are aboard, it just takes time. Just be sure to maintain the liquid level in the batteries, and keep the tops clean. If your panels are bolted to the vessel it is no different than any other rigging you leave while you are home. There are very inexpensive solar set-ups available to handle your problem.

[Eustace Scrubb]

Zil,

Thank you! You're quite right --- I did have some difficulties understanding all the responses.

I believe that our best option right now is to limit ourselves to a single battery which we can take home at the end of the weekend, to charge on our existing 3-stage "smart" charger .

If we need more battery power, for a 5 or 6 day cruise, we can:
a) add a second, fully charged battery in parallel with the first, extending the duration and taking both home to charge at the end of the cruise; or,
b) invest in solar combined with an inverter-charger; or,
c) bring along our generator and our 3-stage charger, disconnect the battery from the boat, place it in cockpit, and charge it while we're at anchor or at a mooring. If we're tied to a dock, we can do it ashore. In our experience, it takes only a few hours to fully charge a marine 90-amp marine battery.

Option c) presents the question of where, on the boat, we could safely keep the generator while we're sailing. At home, we keep it on our balcony. Given that the cockpit already has a gas tank in it, it seems to me that storing a small generator there, too, would be safe. Or perhaps we could lash it to the deck?