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Catalina/Capri 25/250 Sailor's Forums

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I need a cheap way to monitor my batteries

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deastburn
Captain

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USA
334 Posts

Initially Posted - 05/25/2002 : 00:02:11

I have two batteries, wired through an On/OFF/BOTH switch. "Wood Duck" lives on a mooring, so no shore power. I want to be able to monitor battery levels (other than through my GPS readout, which I don't believe is that accuracte. I have read here of people witing a voltmeter to the battery cables, but I have little or no knowledge of the complexities of electrical wiring. Can someone out there help me out be describing a way to add a cheap battery monitoring system to my boat. It will help me know when it is time to take the batteries ashore. Thanks

Dave E on "Wood Duck" (#2616)

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eric.werkowitz
Captain

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283 Posts

Response Posted - 05/25/2002 : 02:53:39

Dave,

Why don't you just invest in a cheap, digital Volt/Ohm Meter (VOM). Try Radio Shack. Whenever you leave the boat, just pull the covers off the batteries and check the voltages. Fully charged, each battery will be about 12.8 volts (although they can go over 13 volts when "over charged." If you look around, there are scales that show the % charge remaining as a function of battery voltage.

Eric Werkowitz
C25 #4969

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Arlyn Stewart
Master Marine Consultant

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2980 Posts

Response Posted - 05/26/2002 : 00:24:14

The cheapest way that I can think of is a Harbor Freight and Tool digital volt ohm meter. They run under $10 and with some velcro stuck on are easy to mount...and then removed for other electrical challenges. Be sure to turn them off however...the 9v batteries wont last long left on.

Mine is mounted near to the aux cig lighter power outlet. Leads could be hard wired to a plug for an easier test.

A reading of 12.7 means full charge...

Arlyn C-250 W/B #224

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Todd Frye
Navigator

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USA
222 Posts

Response Posted - 05/26/2002 : 22:36:51

I've looked into the same upgrade. Digital readout, dedicated voltmeter guage only...around $80-$100 ( West Marine, local electric shops, etc.). Plan 2 was hatched while cruising the aisles of Sears, I noticed a large faced digital voltmeter (testing instrument) for $19.99. Figured I could remove the guage and wire it to a "push to test" button adjacent to the guage for on demand battery condition.Let us know what you come up with. Todd Frye

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Ed Montague
Captain

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499 Posts

Response Posted - 05/28/2002 : 01:10:20

This is what my monitoring system looks like. You can make out the multi-meter just under the CD player.<img src="http://im1.shutterfly.com/procserv/47b2da34b3127cce9d3525ead3bf0000003410" border=0>

Ed Montague on 'Yahoo'
1978 #765 SK, Stnd, Dinette ~_/)~

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Ed Montague
Captain

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499 Posts

Response Posted - 05/28/2002 : 01:32:22

Here is how it is done.<img src="http://im1.shutterfly.com/procserv/47b2db06b3127cce9daaae7fd6030000001410" border=0> I got this from Sail magazine, Things That Work.

Ed Montague on 'Yahoo'
1978 #765 SK, Stnd, Dinette ~_/)~

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John Mason
Admiral

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USA
687 Posts

Response Posted - 05/28/2002 : 14:02:30

I did the cheap multimeter type project. Bought one on Ebay for about $6. Ran a wire from the positive "out" of the main "1-both-2" selector switch to a red female "banana" connector (same kind that fits into the multimeter) mounted on the bulkhead near the electrical panel. Did the same from the main negative bus to a black female "banana" connector.

Then made two leads with male connectors at both ends long enough to go from the multimeter to the connectors at the bulkhead. Plug 'em into the multimeter set at DC volts, other end into the bulkhead connectors and turn the main selector switch to position 1 or 2 to get a read on the battery level. Also put a piece of velcro on the back of the multimeter and one on the bulkhead. Works great.

John Mason - Ali Paroosa
1982 - FK/SR #3290

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RichardG
Admiral

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990 Posts

Response Posted - 05/28/2002 : 14:46:02

I got a small auto voltmeter from Pep Boys (auto parts store) for about $10. It doesn't have normal leads, but instead has a small digital readout which rotates about the back end of a cigarette lighter plug. The whole thing is about the size of a business card. Plug it in and use the A-B switch to check the two batteries -- then pull it out and toss it in the drawer when finished.

RichardG 81 C25 SR/FK "Sanity"

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LOREN SOUERS
Navigator

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USA
100 Posts

Response Posted - 05/28/2002 : 15:24:48

Call me lazy. I know about the other types of battery testing, and own a multimeter, but my depth sounder stops working at about 9.5 volts. So I use one battery til it malfunctions, then switch to battery 2 and take the one battery home for recharging. (I,too, have no shore power and no charger on my motor, etc.) Now, if I could just remember to turn off the battery when I leave the boat...

Loren Souers, aboard
Nimue,
The Lady of the Lake

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John Mason
Admiral

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USA
687 Posts

Response Posted - 05/28/2002 : 16:58:59

Oh, sure RichardG, you're just trying to make things easier than they have to be <img src=icon_smile_wink.gif border=0 align=middle>.

John Mason - Ali Paroosa
1982 - FK/SR #3290

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Sam Nelson
1st Mate

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64 Posts

Response Posted - 05/28/2002 : 19:00:48

RichardG has the perfect solution!
The KISS principal at work.

Sam Nelson
C25 "Stratos" #3811

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 05/28/2002 : 20:14:51

I love RighardG's solution, too--but I ain't got no Pep Boys round these parts. Gotta start visiting the auto parts stores...

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette "Passage" in SW CT

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deastburn
Captain

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334 Posts

Response Posted - 05/28/2002 : 21:05:50

Many thanks to you all. BTW, I have been checking in on and contributing to this forum for six years. I love Richard G's solution for its simplicity. But I will soon install Ed Montague's solution just because it is permanent, always there (I guess that is another definition of permanent!). I have zero electrical knowledge (although I wired my own home, and it is still there fifteen years later); try me on amps, ohms and volts and you'll likely see smoke coming out of my ears. So Ed's extrememly clear diagram is what I was looking for. Now, on to the asymmetrical spin-job... and the cockpit based main traveller...

Dave Eastburn
Wood Duck #2616

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LeighMarie
Navigator

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188 Posts

Response Posted - 05/28/2002 : 21:31:47

RichardG: I know very little about electrical wiring, etc., so this may be a dumb question. But, when you say "The whole thing is about the size of a business card. Plug it in and use the A-B switch to check the two batteries...", where exactly do you plug it in? And what type of leads are there to plug in?

I have 2 batteries aboard, and out on Muskegon Lake this past Sunday, when suddenly my depthmeter read 2.1 feet in the middle of the channel heading out to Lake Michigan. I fixed the problem by switching it to the 2nd battery and we were all set. But, if I had something that I could easily know where the charge is, it would be great.

Dave & Sharon on "Leigh-Marie"
Hull #5128

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Ed Montague
Captain

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499 Posts

Response Posted - 05/29/2002 : 02:05:25

Another thing to do to help understand the charge on your battery (as soon as you install the multi-meter) is to keep a small chart or lable next to the read out. Most 12 volt batteries are considered fully charged at 12.8 volts and discharged at 11.7 volts. In between those levels, the battery's charge can be measured as a percentage of fully charged voltage. In other words, 12.25 volts means your battery is down to 50%. So is your battery half empty or half full? <img src=icon_smile_wink.gif border=0 align=middle>

Also remember that running your battery down and then not completely recharging will shorten the life span. I have a solar panel charging my two batteries. I must check the water level on a regular basis or the batteries will boil away. Charging completely dead batteries can create a great deal of heat and on occasion a battery will "run away" as one cell fails. This can cause a fire which is not a good thing at any time, especially when unattended.

Ed Montague on 'Yahoo'
1978 #765 SK, Stnd, Dinette ~_/)~

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RichardG
Admiral

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990 Posts

Response Posted - 05/29/2002 : 17:38:40

Dave & Sharon:

I'm not very good in the electricity department either. I refuse to deal with AC stuff around the house -- but I can sort of conceptualize the DC stuff on the boat (i.e. my electrons only go one way).

The leads are contained in the cigarette lighter plug (like on the cigarette lighter adapter of your cell phone). You plug the voltmeter directly into the cigarette lighter receptacle, which on my boat is right behind the galley sink. I've seen some of these voltmeters which have only light indicators which limit the readings to "charged", "half-charged" and "dead". I prefer the kind which gives an actual voltage readout (+/- 0.1 volts).

Due to my limited understanding of electric systems, I tend to avoid "hard-wiring" (permanent install) new things on my boat. While this may cause a little clutter around the 3-way splitter plugged into my cigarette lighter receptacle, it allows me to easily follow the wires in case of problems operating my portable stereo, TV/VCR, GPS, cell phone, coffee maker, etc. It also allows me to take those items with me when I leave the boat.

Call me lazy, but with two young kids often onboard on overnight trips, I never want to run low of electricity and children's videos.

RichardG 81 C25 SR/FK "Sanity"

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John Mason
Admiral

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687 Posts

Response Posted - 05/29/2002 : 18:57:20

Not trying to make waves <img src=icon_smile_big.gif border=0 align=middle>, but is the cigarette lighter plug a factory item or an add on? My boat has one. It's on the port side, about mid settee, hidden up behind a ridge near the deck/hull joint. Looks like a PO wired it in.

John Mason - Ali Paroosa
1982 - FK/SR #3290

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LeighMarie
Navigator

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USA
188 Posts

Response Posted - 05/31/2002 : 08:24:31

RichardG: That may the difference between your boat (and others?) and mine: I don't have a cigarette lighter adapter anywhere on my boat. I should clarify that in that when I bought it the guy before me had wired such an adapter into the back of the terminals on the knotmeter unit, but it wasn't successful as the wires were all melted. I took it off for fear of a fire. He was trying to jump it off another working unit rather than having it wired in. Maybe I should get one wired in.

Dave & Sharon on "Leigh-Marie"
Hull #5128

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RichardG
Admiral

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990 Posts

Response Posted - 05/31/2002 : 14:00:23

Dave & Sharon:

That doesn't sound good (the way the previous owner did it).

Mine is wired directly to the A/B switch terminals. This way, I get power to the cigarette lighter using only the A/B switch without having to turn on the "Master" or any other switch. Someone less electron-challenged than me may offer a better setup.

John brought up a good question -- how many have a cigarette lighter receptacle installed?

RichardG 81 C25 SR/FK "Sanity"

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pbarr
1st Mate

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54 Posts

Response Posted - 06/01/2002 : 03:14:29

In the same vein... Are there inexpensive battery chargers available that I can leave on all the time that will not overcharge my battery?

I currently have only one battery, but I do have shore power.

Phil

pbarr@umich.edu

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John Mason
Admiral

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687 Posts

Response Posted - 06/03/2002 : 15:31:27

Phil,
I don't know how inexpensive they are, but you definitely want a multi-stage charger built for marine conditions. Check Sailnet.com or Westmarine.com

John Mason - Ali Paroosa
1982 - FK/SR #3290

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Champipple
Master Marine Consultant

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6855 Posts

Response Posted - 06/03/2002 : 16:18:09

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
In the same vein... Are there inexpensive battery chargers available that I can leave on all the time that will not overcharge my battery?

I currently have only one battery, but I do have shore power.

Phil

pbarr@umich.edu

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

We picked up an inexpensive Guest (brandname) charger that is on constantly whenever we are plugged in at the dock. It is a small unit...6amp with trickle charge and auto cut off. But it does the job to keep the batteries topped of, and, it can be fully immersed in water and still operate. I won't go into all the specifics, but it is hardwired to the boat's AC system, runs through a battery isolator, then directly to the batteries.

One other note, according to code, there needs to be an inline fuse going from the battery charger to the batter(y)(ies). If the run is more than x feet you should have an inline fuse at both ends... I can't remember what the x equals, but our run is about 6 feet from the isolator to the battery. We have inline fuses on either side of the isolator. (3 in total) Probably overkill but it works...

dw

Duane Wolff
"The Flying Wasp"
C-25, #401 std,sk
Chief Measurer C-25/250 National Assn.
<img src="http://im1.shutterfly.com/procserv/47b2dc20b3127cce9cd2f45b211a0000004010" border=0>

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