I’m basically a day sailor but we’re contemplating a cruise around Lake Michigan this summer. I have two batteries on the boat connected to a selector switch and when I go out I alternate batteries daily. Batteries are fully charged overnight in the slip. I don’t use much electricity, an autopilot and multifunction display for chart, and GPS info. Last year I discovered that after a day of autopilot use occasionally and the other items all day, the battery I was on wouldn’t turn over the engine. I replaced both batteries and I’m thinking I need a battery monitor. I’m wondering though, do I need a separate battery monitor for each battery or will one monitor work. I’ve searched for wiring diagrams but can’t find what I think I’m looking for. Thinking about a Victron or Balmar but don’t really know what I need.
Battery monitor
- Thread starter wing15601
- Start date
Ditto to what Stu said. Here are some additional thoughts.
What do you want a battery monitor to tell you?
Are you looking for total amp hours used to help you to decide how large a battery bank you need or do you want to monitor how full your batteries are?
The Balmar SG200 will do the latter but won’t tell how total Ah used. The Victron will tell tell you how many amp hours going out and how many you put back in when charging.
It all can get quite complicated.
You should probably start here https://marinehowto.com/installing-a-battery-monitor/
to learn how to install a battery monitor.
Then read the sister article on how to program a battery monitor.
Here’s a thread on the new Balmar SG200
https://forums.sailboatowners.com/index.php?threads/balmars-new-battery-monitor.193524/
That section of the forum, Musings with Maine Sail, has several good threads to read about battery monitors.
The thread about the 1/2/both/Off switches is very good.
That thread will help you realize that you probably need what most people have, a multi battery bank for house loads and 1 battery for either starting or emergency reserve when you do as you did, run the house battery too low.
Those threads should help you get started in figuring out what you need.
What do you want a battery monitor to tell you?
Are you looking for total amp hours used to help you to decide how large a battery bank you need or do you want to monitor how full your batteries are?
The Balmar SG200 will do the latter but won’t tell how total Ah used. The Victron will tell tell you how many amp hours going out and how many you put back in when charging.
It all can get quite complicated.
You should probably start here https://marinehowto.com/installing-a-battery-monitor/
to learn how to install a battery monitor.
Then read the sister article on how to program a battery monitor.
Here’s a thread on the new Balmar SG200
https://forums.sailboatowners.com/index.php?threads/balmars-new-battery-monitor.193524/
That section of the forum, Musings with Maine Sail, has several good threads to read about battery monitors.
The thread about the 1/2/both/Off switches is very good.
That thread will help you realize that you probably need what most people have, a multi battery bank for house loads and 1 battery for either starting or emergency reserve when you do as you did, run the house battery too low.
Those threads should help you get started in figuring out what you need.
I sail an O’Day 322 on Lake Michigan, and also mostly day-sail. I have done a few nights on the hook and find my battery/ power supply insufficient for anything more than a night or 2 on the hook. Here are the things I am working on to make my boat more “self-sufficient”:from a power standpoint:
1) power usage - I have changed all interior lighting to LED. It is amazing how much juice you lose from older incandescent lighting. Same for my anchor light. I have a refrigerated icebox, and have added insulation to try and keep the compressor from cycling. I SHOULD have the compressor checked for refrigerant, etc.
2) battery capacity - I only have 2) group 27 “deep cycle” batteries. They are not set up in a single bank. This is not enough capacity. I am still contemplating the solution... adding 2 more group 27’s and having 2 groups of 2 (about 200 AH in each bank), or moving to 6-volt GC batteries and having a separate starting battery. Definitely need more capacity.
3) power generation- I have no way to charge the batts other than my alternator (unless I am on shore power). I need to add solar panels,wind generator or something to recharge the batts. Another idea is just but a Honda E2000 and a cable to power the built-in battery charger.
Since I am still mostly day sailing, I am not moving too quickly on my projects, but this past summer, I spent a few days on the hook, and my batt (I was using them separately and keeping 1 in reserve) was pretty depleted the second day.
I can’t find my video from this (2018) season, but here is one from 2017...
Good luck!
Greg
1) power usage - I have changed all interior lighting to LED. It is amazing how much juice you lose from older incandescent lighting. Same for my anchor light. I have a refrigerated icebox, and have added insulation to try and keep the compressor from cycling. I SHOULD have the compressor checked for refrigerant, etc.
2) battery capacity - I only have 2) group 27 “deep cycle” batteries. They are not set up in a single bank. This is not enough capacity. I am still contemplating the solution... adding 2 more group 27’s and having 2 groups of 2 (about 200 AH in each bank), or moving to 6-volt GC batteries and having a separate starting battery. Definitely need more capacity.
3) power generation- I have no way to charge the batts other than my alternator (unless I am on shore power). I need to add solar panels,wind generator or something to recharge the batts. Another idea is just but a Honda E2000 and a cable to power the built-in battery charger.
Since I am still mostly day sailing, I am not moving too quickly on my projects, but this past summer, I spent a few days on the hook, and my batt (I was using them separately and keeping 1 in reserve) was pretty depleted the second day.
I can’t find my video from this (2018) season, but here is one from 2017...
Good luck!
Greg
The simple solution is to parallel your two existing batteries then buy a small "reserve/start" battery as your "bank 2". If you are killing one battery, to the point it can't start a motor, you're grossly over-discharging it and life will be short. Once you do that one battery monitor will work. As has been said previously you really need to do an energy budget so you know how many Ah's you use..
The easiest and most simple battery monitor is still the original Balmar Smartgauge. This is because it is a simple three wire hook up and it remains accurate even as your bank ages, where a traditional Ah counter will not.
The newer Balmar SG200 is a step up from that, despite it costing less, and it too can remain accurate and track your bank even as it ages but the installation is a bit more involved.
All that said you can install an accurate digital volt meter, that reads to the hundredths position, and then don't discharge below 12.20V.
Thank you all for your replies. I have not done an energy budget but that should probably be first. I would like to add another battery, Stu, but I don’t know where I could put it. Thank you, Ward, for the links, they seem to be very helpful. The LED conversion is an excellent idea, Greg. I too have considered the Honda generator hung off the transom just for charging for extended trips as I don’t have the room for enough solar panels to really replace many AH’s used. I didn’t actually kill the battery by drawing too much, Maine Sail, the battery was obviously weak starting out and that’s what sparked the idea to monitor the batteries capacity and AH’s used. I’ve studied some and now realize that a 100 AH battery new last year is not a 100 AH battery this year. Guess I’ll investigate the Balmar offerings as it seems they take the reduced battery capacity into consideration. Hey, Greg, great video.
I found a cigar lighter outlet volt meter at a Sears auto store. I'm sure other places sell them. In use, it is about as acurate as the Victron 600 system. It is enough to read your voltage - a starting step for what you need.
My sailing club does an overnighter (and up to 9 days) cruises every other weekend. When motoring around to wait to get into the raft, I turn the fridge to it's coldest setting. Of course on anchor we are in and out of the fridge for drinks and dinner, so sometimes leave it on the coldest. Before bedtime I just shut off the circuit breaker till morning (when the sun hits the solar panels). Saves a bunch of battery amps. Motoring out helps restore the batteries further. By the way, with the fridge compressor under the sink, it can heat the fridge box, so I put in two vents on the fore and aft sides of the sink cabinet. I have seen boats with ducts from the compressor fan out into the cabin.
My sailing club does an overnighter (and up to 9 days) cruises every other weekend. When motoring around to wait to get into the raft, I turn the fridge to it's coldest setting. Of course on anchor we are in and out of the fridge for drinks and dinner, so sometimes leave it on the coldest. Before bedtime I just shut off the circuit breaker till morning (when the sun hits the solar panels). Saves a bunch of battery amps. Motoring out helps restore the batteries further. By the way, with the fridge compressor under the sink, it can heat the fridge box, so I put in two vents on the fore and aft sides of the sink cabinet. I have seen boats with ducts from the compressor fan out into the cabin.
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In addition to the links Ward provided to Maine Sail's material, you can find lots more here:
Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html
Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html