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Wiring & Installing A Battery Monitor

Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH
Thanks Maine. One thing about this lousy weather, time to read and study. I saved this thread until I reread my Link 2000 manual. I installed mine in 2003 and it has worked fine, first with Gels and now with AGMs. Your thread reinforces my understanding and also makes me wonder if my bilge pump ground is on the right side of the shunt. Something I have never done is equalized my AGMs. It never occurred to me because I had remembered NOT to equalize the Gels. I guess that I thought you shouldn't equalize sealed batteries.
 
Feb 6, 1998
11,118
Canadian Sailcraft 36T Casco Bay, ME
Something I have never done is equalized my AGMs. It never occurred to me because I had remembered NOT to equalize the Gels. I guess that I thought you shouldn't equalize sealed batteries.
Ed,

The ONLY brand of AGM's that I know of that can actually can be equalized are Lifelines. Trojan for example specifically states NOT to equalize their AGM's as does Deka. Deka/East Penn is who makes the WM AGM batts. Check with the manufacturer before equalizing your AGM's.
 
Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH
Thanks for that heads up Maine. I think that they are Lifelines but would love to get to the boat to check. The ten day forecast is for snow and never out of the 20's. :(

Did your post include the reasoning for fuses at the battery? I'll reread.
And I still don't understand how you post the great pictures.
 
Feb 6, 1998
11,118
Canadian Sailcraft 36T Casco Bay, ME
Did your post include the reasoning for fuses at the battery? I'll reread.
And I still don't understand how you post the great pictures.
Safety!! The fuses at the battery are to protect any wiring that directly connects to the battery and could potentially chafe or otherwise short out somewhere. House banks can deliver massive amount of current, many banks are easily in excess of 3000 amps. In a dead short situation this is very likely a boat fire.

I had this happen on my 2005 Catalina due to sloppy factory wiring. ABYC E-11 requires fuses for a "house" bank but there is no requirement for a battery fuse on a start bank. With the typical 1/2/BOTH/OFF switch wired directly to the starter this is a rather odd omission for start batteries on small boats with small motors. This is made even more ridiculous with Catalina shipping the vessel with two IDENTICAL 4D batteries were either bank could the the house bank and either bank could be connected to the starter but just one bank is fused.

I have gone around and around with John Adey at ABYC regarding this, and even he agrees personally & ideally that all banks should be fused, but it has been to hard to craft language to meet all scenarios. At some point you hit engines where fusing start banks becomes so expensive and difficult that it' not feasible and a sheath or conduit protection is a better solution.

On small AUX diesels this fusing is however is a non-issue. Due to the E-11 requirement Catalina uses just one ANL fuse. When I bought the boat I simply added one for the "start/reserve" bank as well.

Long story short the wire from the common post of the batt switch to the starter shorted and chafed on the diesel motor as it came out of its conduit chase. Luckily I had a 250 amp ANL battery protection fuse on that circuit. The short literally took a chunk of metal out of the motor like a welder could. Without a fuse it is likely our brand new vessel would have burned to the waterline.

That is why I fuse banks...
 
Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH
So Maine, you write that "Long story short the wire from the common post of the batt switch to the starter shorted and chafed on the diesel motor as it came out of its conduit chase. Luckily I had a 250 amp ANL battery protection fuse on that circuit."

On my boat with four 100aH AGMs that fuse would be on the positive post that is connected to the #2 position of the battery switch? But if I happened to be on the starter battery and the common shorted then that fuse is no help.
 
Feb 6, 1998
11,118
Canadian Sailcraft 36T Casco Bay, ME
On my boat with four 100aH AGMs that fuse would be on the positive post that is connected to the #2 position of the battery switch? But if I happened to be on the starter battery and the common shorted then that fuse is no help.
Correct, which is why I always fuse the house and start/reserve batteries on small sailboat aux motors and why I added the second fuse to my Catalina 310's "starting" battery...
 
Feb 8, 2009
117
Sabre 34 MK-1 Annapolis, MD
To add a bit to Main's post. Some people say a fuse on the Start battery is risky. I put an ammeter on my starter wire, and cranked my Volvo MD11C on a cold morning -- the current bounced around 100A. Yeah, it's a small engine, but that is a FAR cry from 250A. And a 250A fuse will even carry 300A or more for a few moments. Fuse all batteries, within 7" of the battery (if you can -- it's not easy!), and before the switch.

Harry

Correct, which is why I always fuse the house and start/reserve batteries on small sailboat aux motors and why I added the second fuse to my Catalina 310's "starting" battery...
 
Feb 6, 1998
11,118
Canadian Sailcraft 36T Casco Bay, ME
To add a bit to Main's post. Some people say a fuse on the Start battery is risky. I put an ammeter on my starter wire, and cranked my Volvo MD11C on a cold morning -- the current bounced around 100A. Yeah, it's a small engine, but that is a FAR cry from 250A. And a 250A fuse will even carry 300A or more for a few moments. Fuse all batteries, within 7" of the battery (if you can -- it's not easy!), and before the switch.

Harry
Your starter likely draws a lot more on in-rush but there are very few meters that can read high amperage DC in-rush. That being said what you saw is very reasonable and an ANL, Class T or MRBF will not blow on the .1 - .25 second in-rush current. Our 44Hp draws well under 200 amps.
 

Salty

.
Dec 2, 2008
143
Oday 322 Mount Sinai, NY
Maine Sail, another great informative post. After reading this, I have to take a look at my entire power setup and would definitely add a battery meter.

Thanks

Salty
 

Tim R.

.
May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
I have used the xantrex, victron and my current Ample Power energy monitor. The Xantrex was a PITA(in comparison) to install and the Victron was very simple. Ranking them based on usability and functionality I would favor the Ample Power, then the Xantrex and then the Victron. No experience installing the Ample Power but I have had a good look at how it is installed and seems fairly straight forward.
 
Mar 25, 2010
152
Hunter 34 Godspeed Rose Haven MD
Nice post MS - Batt Mon is on my list of upgrades for early spring so was very glad to get any additional info. And thanks for doing the install on the boards - made it really easy to follow.
 
Jan 21, 2011
1
Westsail 32 Lake Barkley
The AH portion of the meter uses the shunt as the sole data input. The power wire provides power to run the unit, as well as an input for the V display. There is no real requirement that the power come from the same battery that you are monitoring.
Harry
Based on the above I assume it is not necessary to connect the power feed directly to the battery. Is there any problem with connecting it to the boats positive bus?
 
Jun 6, 2006
6,982
Hunter 40.5 Harrington Harbor North, MD
Connecting the unit

It does need to be left on all the time like the bilge pump. I suspect when you leave the boat and turn everything off the unit would loose its "battery status/state" information. when you restarted it it would then not know how charged the batteries were. This would defeat the purpose of having the unit so hooking it to the switched power buss would not be the answer.
 
Feb 6, 1998
11,118
Canadian Sailcraft 36T Casco Bay, ME
Based on the above I assume it is not necessary to connect the power feed directly to the battery. Is there any problem with connecting it to the boats positive bus?
Bill is correct the power sense wire should be led directly to the positive post of the battery being monitored and not switched. This device draws 4 mA or .004. This is less than the self discharge rate of most batteries over a month so power consumption is really a non-issue.
 
Apr 29, 2010
209
MacGregor m25 Erieau, Ontario, Canada
Thanks for a great electrical primer Maine Sail.

When connecting the charger for a multiple battery system (say, 2 house batteries), can the positive of the charger connect to the first battery post to charge both batteries? If not, how are multiple batteries charged?

Frank
 
Jan 7, 2011
7
Bristol 35.5 Edgewater, MD
Thanks Maine for your great help. I am adding BlueSeas MRBFs to our 1983 Bristol 35.5 at your suggestion. We have the original Universal 5424 (24hp) diesel with 55amp alternator. We have a 3-battery house bank (Trojan deepcycles Grp27 @ 115amp) and a 1-battery Grp 27 @ 115amp starter/reserve. The house bank is wired in parellel. Am I following you correctly that I need to install battery fuses on each battery(3 total) on the house side? What size MRBF are you suggesting?
 
Feb 6, 1998
11,118
Canadian Sailcraft 36T Casco Bay, ME
Am I following you correctly that I need to install battery fuses on each battery(3 total) on the house side? What size MRBF are you suggesting?
No just one fuse for each bank on + battery post where the power cable goes to the batt switch.. If your house bank is separated by a distance then another MRBF can be a good idea at the second location to protect the parallel cable run.
 
Feb 6, 1998
11,118
Canadian Sailcraft 36T Casco Bay, ME
House bank is about 40" from the battery switch. Thanks.
Sounds like all batts are in the same compartment and close to one another but 40" from the switch. You just need one MRBF per bank on the output cable going to the switch then.
 

JMM

.
Feb 9, 2011
34
Hughes H40 Semiahmoo,WA
Sounds like all batts are in the same compartment and close to one another but 40" from the switch. You just need one MRBF per bank on the output cable going to the switch then.
Maine Sail - I am in the process of adding all this missing fuse protection to our boat this season -- I have a question related to adequately protecting the battery terminal with covers when these are added -- they extend the coverage area needed (especially with the double ) and the standard terminal covers seem to be too small. Do you have another source or suggestion?
Thanks, Jim