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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Battery combiner and charging

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sterngucker
Navigator

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USA
169 Posts

Initially Posted - 07/12/2004 : 16:57:28

Last night I was perusing though boat catalogs trying to wire up a two battery system in my head (no jokes here!

Charlie
"C Angel" 250WB #799

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 07/12/2004 : 18:55:21

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by sterngucker
 Last night I was perusing though boat catalogs trying to wire up a two battery system in my head (no jokes here!

) and thought I would follow West Marine's system of separate starting and house batteries detailed in their annual catalog. It seemed like a good idea to use a "combiner" to charge each battery from the outboard's alternator and from the solar panel. I was also looking at upgrading my built-in AC battery charger to a dedicated two battery unit. Then it occurred to me to keep my present "one battery" charger and let the combiner apply it to both batteries. Is my logic flawed? Will the battery charger be confused as to the "state of charge" or will it see both batteries as one unit because of the combiner?
<hr height="1" noshade id="quote"></blockquote id="quote">

I sail on a lake and use two car batteries with a Guest charger (mine handles two batteries). No issues, do not expect any. Johnson 9.9 charges while it runs, I leave my dual battery switch on "both" 24-7. All summer at the dock I am plugged into shore power, all winter at home I am plugged into driveway power. After sitting on the charger from September to April I checked my water level and it had not changed. I guess I'll check it tonight to see if there is any difference. I am sure all this hoorah about batteries matters for some reason but... I cannot figure out why everyone makes such a big thing out of this for our little boats. What is the worst thing that can happen to a lake sailor? We pull start our motor and go to Sears for new batteries!

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Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 07/12/2004 : 19:37:18

the worst thing that I have heard happen to someone in a little boat like ours was that the battery got overcharged, outgassed hydrogen, and there was an explosion on board.
I read this story recently in one of the many sailing mags I get, I'm not sure which one.

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oldsalt
Admiral

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USA
578 Posts

Response Posted - 07/12/2004 : 20:33:45

Due to the low voltages involved in 12 volt marine systems and their attendent inability to deliver an electric shock, many tend to dismiss them as harmless and will treat them with little regard for safety and employ haphazard, homespun charging and wiring methods.

In fact, there is a lot of energy stored in a 12 volt marine battery system, both chemical as well as electrical. The release of hydrogen into a confined space can be more hazardous than propane or natural gas however, being that hydrogen is the lightest element, it will normally escape upward through any available vent, especially through open hatchboards, but if it does become trapped and ignited, it has the highest specific impulse of any fuel and will cause quite an explosion.

The high amperage electrical energy will manifest itself as heat in the event of a short circuit in the main battery cables; enough heat to burn your boat to the waterline in no time at all and/or cause a directly shorted battery to explode. Improperly fused, or unfused branch circuit wiring will go from cold to almost white hot in a matter of seconds in the event of a short, and will start a fire throughout the length of the wiring. I always fuse anything that comes directly off the battery terminals and use a Guest main disconnect selector switch with "1", "both", "2", and "off" positions. Wiring can unexpectedly chafe and cause a fire so I turn my main switch to the off position whenever my boat is unattended and additionally, the starting wires from my outboard are fused and connected to the batteries through this switch. I would hate to have these wires chafe while I was away and lose my boat.

My ancient Ray Jefferson automatic 15 amp 2 batttery charger is connected directly to the battery terminals, bypassing the main switch but is fused so I feel comfortable leaving the unit on charge 24/7.

I suggest using a fused, purpose designed, 2 battery automatic marine charger rather than trying to design something from scratch.

Edited by - oldsalt on 07/12/2004 20:38:33

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 07/12/2004 : 21:40:33

Charlie,

There are many ways to wire a boat. Much depends on your intended pattern of use. As Frank Hopper pointed out, a boat with a rope start outboard that is only used for daysailing on a small lake doesn't need as elaborate an electrical system as one used for coastal cruising with an electric-start-only motor. I agree with Old Salt about the importance of safety. Not every boat needs an electrical system. But every boat with an electrical system needs a safe one.

Once committed to a separate cranking battery, I prefer the [url="http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorDisplayView?storeId=10001&langId=-1&catalogId=10001&advisor=creatingabatterysystem.htm"]two-bank isolated system[/url] advocated by [url="http://www.westmarine.com/"]West Marine[/url].

As for using a one-bank charger on a multi-bank system equipped with battery combiner(s), yeah...that could work... If! All batteries were of the same technology (flooded cell, gell cell, or absorbed glass mat), and all in about the same condition (on a scale from new to worn out).

I think the biggest objections some people have to this design are: switching over to it involves removing still-working parts and spending money, it's not what they're used to, they're insulted by the implication that they can't be counted on to operate the traditional [OFF/1/BOTH/2] switch correctly, and working with electricity is a mystery to lots of folks.

-- Leon Sisson

Edited by - on

Bill Holcomb
Admiral

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USA
769 Posts

Response Posted - 07/13/2004 : 08:31:27

Hi Charlie,

Listen to Leon.

Especially with regard to having all batteries of the same type (gell cell, flooded cell, etc.). The different technologies involved REQUIRE that different charging voltages are needed. ie, flooded cells need more charging voltage than gell cells. If you try to charge a gell cell with the "hotter" voltage, you'll ruin the battery in a hurry.

Bill Holcomb - C25 Snickerdoodle #4839

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 07/13/2004 : 13:47:02

Keep it simple, Charlie. A lot of the advice in West Marine is focused on dedicated long range cruisers and is intended to, of course, sell you stuff.

I don't recall, does you really cool new Tohatsu 9.8 4 stroke have a pull start?

If you are coming to Catalina with us, you'll need 2 batteries. They should be the same kind. A deep cycle battery will start your puny outboard just fine. (Big starting batteries may be needed for big marine diesels). If they are the same kind, they can be wired together or connected to your C250 electrical system through a simple 1,2, Both switch. Wire your existing shore power charger to the 1,2, Both switch. Leave the switch on Both all the time (unless there is some kind of problem with battery 1 or 2 like a shorted cell).

Your engine, shore power, and solar panels are all charging sources and should not be used at the same time. These things only put out a few amps. I have a 10 amp 3 way switch I wired to choose between charging source, combined with a test plug, and a volt meter in a little wooden box I made. Simple and only cost a few $.

If you come to Catalina, you'll need solar panels. I use 2 United Solar Flex 11s. You can just lay these on deck or tie them to the boom. They are flexible, can roll up, and tough enough that you can walk on them. I tie them to tbe boom, run a wire down from the boom and it plugs into my test plug on the wooden box mentioned above. I got a $35 voltage regulator because I have Gell batteries. The regulator or Gells are not really needed. But I like not having battery acid to spill.

The US Flex 11 puts out 0.75 amps. They cost $95 each. There is a great place in San Diego to get them cheap. You can also get a US Flex 33 which is 3 of the 11s in one long piece (2 amps). It costs under $200. I would get that combo. However 2 Flex 11s will charge my batteries back to full charge by noon on a sunny day - but I greatly limit electrical use and have candles and an oil lamp at night. Here's the place, it's right by my office on the way to Mission Bay

http://www.solarelectricinc.com/

Edited by - JimB517 on 07/13/2004 13:48:30

oldsalt
Admiral

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USA
578 Posts

Response Posted - 07/13/2004 : 22:29:07

I wouldn't leave the battery selector on "both" all the time since there can always be an undetected problem with one of them such as shorted cell, low water condition, lower sulfuric acid concentration, or other cell unbalance. It's unlikely that any two like batteries, even those purchased together, will have exactly the same charactoristics.

It's not the best practice, in my opinion, to parallel batteries when it isn't absolutely necessary due to the need to draw on the current of both simultaneously. I also recommend that the fused output of the automatic shore power charger be connected directly to the batteries, bypassing the main disconnect/selector switch. That's how I do it in the co-generation power plants I design which utilize large stationary diesel generator sets. You'll probably be best served by using two deep discharge batteries since they will easily start your outboard and can be used for the house system whereas a system using a starting battery and a deep discharge will not offer this flexibility.

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