Batteries & Extended Cruising

[Catigale]

Extended Cruising - 26X or M?
Hi all! New to this forum and have never owned a sailboat before. I have been looking at a 26X or M and was wondering how appropriate this vessel would be for spending a week or two aboard with the family for vacations? Would it need to be heavily modified?

How long can the batteries last with common electrical items attached, and if I add more, how much do I need to upgrade the batteries? Do they recharge by plugging in to shore power?

. . . When plugged into shorepower both batteries (if that's how the battery switch is set) trickle charge. WITH THE ENGINE ON, batteries charge MUCH FASTER and actually VERY QUICKLY! If battery power is running low under sail for whatever reason (stereo, gauges, etc), just run the engine for 20 minutes and you'll have batteries again. Of course you'll need enough battery left to start the engine (see threads on how tough it can be to pull start these engines). I'm sure more information will follow quickly to you on this subject.

Just to put some numbers on the shore power recharger...I have a 10 amp (5 amp to each battery) charger for my 2 Group 24 wet cell batteries.

If I get a slip on an extended cruise, that means I can recharge about 5 amps * 24 hours = 120 amps hours or my whole battery in one day. Given you should only discharge your battery 50% for longest life you would only need about 8 hours to replenish half the battery capacity with this setup. If you think you will cycle your batteries hard, get the three stage charger Moe refers to above rather than single stage like mine.

Duane's website pretty much describes the full capability of the Mac for cruising imho, he has packed an incredible amount of stuff onto his Mac for his family.


ModEdit: Battery-related vector split from pTom's orig thread: ~fc
Extended Cruising - 26X or M?

[Moe]

Relative to cruising . . . Electricity use is hugely variable. With a single Group 24 deep-cycle used for both house use and outboard starting (on a Mac, not on our C-18's 4HP kicker), you have about 35-40 amp-hours (half the battery capacity) to play with. Discharge below 50% and you won't get much life from the battery(s). If you use the battery(s) for both house and starting, carrying a jump start pack.

The Mac cabin lights each draw 1.5 amps, so if you use 2 for 3 hours each evening, that's 1.5 x 2 x 3 = 9 amp-hours per evening. We used them as little as possible and now have LED cabin lights in the C-18. Not nearly as effective as incandescent, but adequate in the smaller C-18, especially the red ones.

The Mac navigation lights are about 0.75 amps each, so if you sail for two hours after dark, that's 3 amp-hours. If you motor, you need to add the steaming light to that usage, but of course the outboard alternator, not the batteries, is powering it and the nav lights.

The Mac doesn't come with an anchor light, but if you add a 10 watt one, that's about 0.75A x 10 hours or 7.5 amp-hours per evening. An LED one uses about 1/4 that much. Just make sure it's certified to comply with USCG 2 nautical mile visibility standards.

A stereo can use 1-2 amps, so 6 hours of music can use 6-12 amp-hours per day. A fixed VHF radio typically uses 0.5 amps on standby, 1.0 amps on receive, and 5 amps when transmitting. A handheld uses much less. IIRC, our fixed GPS/Sounder used 0.25 amps. Not sure about handheld. [edit to add] A cooler-sized 3.5 cubic foot dual-voltage Engel refrigerator can use 17-20 amp-hours every 24 hours.

Macs do not come with a shorepower battery charger. Previous owners may have added one, or you can. You can also recharge the battery(s) by motoring (with a large enough motor), but not as quickly as with a good 3-stage shorepower charger.

Hope this helps,
--
Moe

Also, a 3-stage charger is always better in that it has a float stage that doesn't overcharge the battery(s) once they're fully charged. You don't have to worry about disconnecting it then.

You're right about the bulk stage not being an advantage once the battery is at or over about 80% charge. At that point, the battery(s) acceptance rate is much lower (about amp-hour capacity divided by 10 at 80%) and a 5-7 amp or less per battery charger is plenty. However, at 50% charge, flooded cell batteries can accept up to 20% or so of their amp-hour rating, and AGM batteries will accept about double that... if the charger has that capability. Acceptance goes down as charge level goes up. It can take as long to charge the 20% between 80 and 100% as it does the 60% between 20 and 80%, even with a big charger.

[edit to add] Another consideration for charger size is to allow some extra capacity for using 12V items at the dock while charging.
--
Moe

Note: This thead was split off by the mods from Extended Cruising - 26X or M? . . . just for future reference. -- Moe

[Catigale]

Moe's experience with batteries and chargers (boats and RVs) far outstrips mine - my point was in sailing and then one overnight slip mode I believe a 5 amp charge capacity per group 24 battery will easily let you bring your batteries back to full charge.

If you want to run in a mode where you might stop for gas and charge for an hour, then the multistate charger and AGMS probably are worth looking at......$$$$$ though.

My electrical needs on the boat are fairly light - we barely use the lights at my latitude because we are all in bed once the sun goes down anyway in the summer months...

A good reason to maintain your charger carefully...- my charger leads have fuses in them - if you were to blow a fuse you would turn your charger on and faithfully think you were topping off you batteries until you found them dead...this isnt an easy thing to detect unless you invest in the full up Charge control panel to monitor your batteries....dont take your fuses out of course

[Duane Dunn, Allegro]

Yet another great example of why I feel an amp hour meter is far better money spent than any other fancy marine style electrical stuff.

My system is simple in keeping with the Mac itself. One bank, now two GC-2 6v golf cart batteries in series (previously two group 24 dual purpose 12v batteries in parallel). A simple master on/off switch feeding main and sub fuse panels, then on through the lamp cord to the lights and loads.

I have a simple 10 amp three stage dual bank charger out of which I only get 5 amps as I only have one bank. It's fed by a simple 15 amp shore power circuit allowing me to use a standard extension cord. The transom 15 amp plug feeds a dual pole 15 amp breaker and then the charger and GFCI outlets. It easily brings up back up to full over night at a dock while also providing 12v power directly to the loads when there.

All this is monitored by my Link 10 amp hour meter. At any time I know exactly how much is in the electrical tank. I can tell if the load is high when too much is on and turn things off. I can tell if the shore power or motor are charging or not. I can see how much power just got put back in over night or during that 2 hours of motoring. None of this can be done precisely while actively using the electrical system with a simple voltmeter.

The amp hour meter takes all the stress about electrical power out of cruising. That's the whole point of cruising isn't it? With the meter for piece of mind, and a jump starter, the sails, and the ability to hand start both my 50 hp and my backup 6 hp motors I have no worries at all that we will ever be stranded by a flat battery.

[Frank C]

A 3-stage charger is always better in that it has a float stage that doesn't overcharge the battery(s) once they're fully charged. You don't have to worry about disconnecting it then . . .

Since renting a slip this year I have 110 volts available at all times. That means I COULD leave my twin Group 29 deep-cycles on maintenance charge, but unfortunately I have only a home garage style 10-amp charger. I've been leaving it aboard, but not attached . . . don't want it cooking 'em, so I just plug it in during weekly cabin-keeping chores. I guess I could also buy one of those little battery maintainers (thx KMC) but they seem a bit dear at 40 bucks.

I was surprised to recently notice that Minn Kota offers a 6-amp 3-stage charger for only $60 (model MK-106). Since I only used one battery at a time (linked through WstMar's combiner), it seemed to me that might be a great, cost-effective choice.

Kinda wondering . . . if it was attached to one battery, would the Combiner permit it to float both batteries? Otherwise, Minn Kota's 2-bank charger is only $90 (model MK-210). They all seem a lot more reasonably priced than the Xantrex stuff we see in WstMar, as evident at the link below.

Minn Kota's On-Board Chargers

[Duane Dunn, Allegro]

For my money I think my next charger is one of these

Pro Sport Charger

I would go with the 12 amp 2 bank charger for $129. What set's these apart is they can give either bank the amount of power it needs up to the max output rather than just topping out at 6 amps per battery. Your starting battery probably isn't very discharged at all but your house battery may need lots of amps. The charger will give a amp or two to the starting battery and send the ballance, 10 - 11 amps to the house battery.

For my use I'd just hook up one bank and end up with all 12 amps available for my large golf cart batteries which can easily accept the higher current flow.

I also gives me more 12v power to dip into when plugged in before the batteries start to augment the power coming from the charger.

[Catigale]

Also fits perfectly if you use the odd even strategy for battery use - the charger will favour the battery that needs it.

[walt]

Duane or any one else with a charge monitor, since you are able to see how much charge is going into the batteries, do you see a difference in charge rate from your outboard at different throttle/rpm settings?

[James V]

Your engin specs should have amp output by RPM. Also this is the most it will put out, when the batter is getting closer to full charge the motor will produce less amps. Per my understanding there is no way to change this with an outboard.

[Catigale]

The Merc BF develops full alternator output at 2000 rpm and above. This is 200 Watts for my model (about 18 amps)...you have to deduct the amperage needed to run the fuel pump and EFi - Ive been promising to measure this and still havent gotten a ROUNDTUIT

[Ivan Awfulitch]

For my money I think my next charger is one of these

Pro Sport Charger

I just purchased this unit for $99 at Gander Mountain. Haven't had time to install it, but plan to get it on the boat by early next year. Check your local store for stock and pricing, but this is the price in Twinsburg Oh.

[kmclemore]

Speaking of chargers, does anybody have an installed charger that does a proper job of equalizing their 12v batteries? I have one with a pulse desulfating feature, but that's not quite the same thing.

[Greg]

Last spring I took a USPS Marine Electronics class and by no means am I an expert on the subject but I thought I’d mention this paragraph from the book . . .

Beware of auto/home chargers. They will often be provided with an auto-transformer, in which a single induction coil is tapped to provide a low-voltage secondary potential. This permits continuity between the AC source and the negative terminal of the battery and is a cause of stray-current corrosion. Chargers for marine use should have transformers that are dual-wound to provide isolated input and output windings.

If you want to charge the batteries from shore power while the boat is in the water, they said the additional cost of the marine charger is justified for the health of the battery and to possibly prevent stray-current corrosion.

Other tidbits from the class:
If a boat is wired for shore power, there should be either a galvanic isolator or an isolation transformer installed to help prevent stray-current corrosion.

Also, never swim in a marina because of the possibility of being electrocuted. If the marina and/or a boat are wired incorrectly or if a piece of equipment fails, enough AC can flow to paralyze a swimmer.

[Retcoastie]

We have a Xantrex +40 and it appears to equalize our AGMs properly, althought I don't run it for 8 hrs.

Edit: equalize our WET CELLS properly. AGMs don't get equalized according to Xantrex. Sorry.

[jeffz]

I am a newbie, but have an M on order with the 6v Golf cart batteries. For safety sake I plan on packing my portable 12v jump start/power supply for emergencies to get the motor running.

You can buy them at Costco or Sams Club for about $50. It has jumped my v10 ford on several occasions.