Electrical Dilemma

[Jazzmanic]

So I've been running this over and over in my head and decided to ask the experts from the Pub.

Last summer while on the hook with our C-Brat buddies in Desolation Sound, I tried using my CPAP using the 12v plug after a few days without charging the batteries. Despite trying to reduce the power draw settings on the CPAP, I ended up fully discharging the House Battery. Since I installed the Blue Seas Add-a-Battery system which is an ACR (or VSR) system, the Start battery was isolated and was not discharged. However, since all my electronics were connected to the House Battery, none of my electronics (most importantly 2 GPS and the VHF Radio) were working as we traveled about 10 miles to Gorge Harbour. Luckily I had GPS on my phone but I started to lose my battery on that as well. We had nautical charts as well but no means of communication either by phone (out of range) or VHF.

I had never before run down a battery since owning C-Dancer and was a little worried that the Start Battery would go too but the ACR did its job of isolating the Start from the House battery and we made it to our destination and were able to charge the House Battery back. I received stern advice from the others saying that one should never compromise the GPS and VHF radio and that those at the very least should have been connected to the Start battery rather than the House Battery.

So I'm asking, what should I do? What do others do?

1) Connect the vital electronics to the Start Battery? That was my first plan of action and I have even purchased all the electrical supplies but am holding off to get more advice from boating experts here at the pub.

2) Buy an AGM battery and charger to be stored in the cabin and connecting the vital electronics instruments to that.

3) Skip the first two above since I'd never had a problem with the configuration prior and buy a generator/inverter to be used during the times we're on the hook (which is rare) and for use in either powering the CPAP or recharging the batteries.

4) Or do nothing, it was an aberration. To repeat, in 11 seasons I never ran down the batteries even once and this only occurred because I used a power hog CPAP for the first time. Meaning the current configuration has worked fine all these years.

I suppose I need to do something because I will be using the CPAP on the hook at one time or another in the future. What say you?

[ghone]

Hi Peter, you must have your electronics attached directly to your house battery, I know it's done. Better to have a Buss for your electronics and power it off your common post of the selector switch, this way no mater which battery you're using, you have power to the electronics.
I use a Buss bar up behind the helm for all electronics, powered off the main line coming from the selector switch in the lazaret
Hope it helps
George

[Pat Anderson]

Peter, another option you did not mention is one or more solar panels to keep your house battery charged. Maybe you should increase the amp hours on the house side, maybe two six volt golf cart batteries in series charged first by the alternator through the VSR, then solar, then a Honda 1000 watt generator as a final backup. You also should look into a Victron battery monitor - knowing the state of charge and when you need to do something about it - is very important to us. What you do ultimately depends on the power requirement of the CPAP, I know our freezer would drain the house batteries (two 12 volt batteries in parallel) if we stayed at anchor for an extended time if we did not have the solar panels. On your question, I am not an expert, but I do NOT want anything on the starting battery except the outboard engine. Address everything else by maintaining a good state of charge on your house batteries! Good luck!

[thataway]

I have had several questions about CPAP. You can cut the current down by turning off heater and dehumidifier. But they are going to use more power than the average battery can handle, over several days. You are now due a new battery.

First. Get a battery voltage monitor. They start at $3 on Amazon. You can even get one which shows amps watt hours etc for about #15. Best to get a Victron monitor (a bit more)> Do not discharge batteries to less than 12.2 volts resting state. When the voltage is down--run the engine to get them back up, buy a generator (EU 1000) and run it to charge the batteries--with a bigger charger than what is built in the boat.

At the very least buy a digital volt amp meter, and learn to use itl.

In the case you had, start the engine. Then wire the main wire to the panel to the engine starting battery. Most likely you can do this with the 1/2/0ff switch. If that battery was truly shot, then the VSR /ACR may not be able to put a charge into the house battery. That would take some investigation

Yes solar panels would help, but not as much as at Lake Powell, where there is a lot more sun!

Another option (basically what we do with the freezers) is to get a 3rd battery, just for the CPAP. Also is it worth while getting the lowest draw CPAP, if you don't already have one.

Innovation, and flexibility are also key.

Should the electronics be wired to the engine start battery? When I have 2 batteries, they are not. Because the low starting voltage and initial spikes from the higher charge output may be hard on them. I learned that lesson the hard way in the late 60's when the first wind instruments came out--fried them because of that.

After the engine is running-OK to connect--so a transfer switch to them would be fine. Notice that when you start the engine==many of electronics will stop, and have to be re-started.

[BrentB]

Would a low voltage alarm help?
see

http://www.boatingmag.com/gear/boat-battery-monitor-and-alarm

https://sirenmarine.com/features/dont-get-stranded-battery-monitoring/


http://aqualarm.net/?zenid=4e73572cd0c0501b6c13b8063f3097d1

[gulfcoast john]

Peter,
Bob has great advice as always...a simple cheap voltage check can save your bacon. An expensive instrument with complex installation and lots of buttons is even more fun.
I learned the hard way in the late 90's EXACTLY what he learned in the 60's.
Some things don't change much.
I don't quite understand why after you got your engine started, you didn't just rev it up to 2k-2500 RPM for a while in neutral to charge the House battery enough to run the helm (10 min?), or manually Combine them or let the ACR do it for the run back.
If the battery is good, a one-time discharge for a known reason is not enough to spend a lot of money on this issue. On the other hand, spending a lot of money on your boat for a not real good reason is perfectly reasonable, if like me you like to do that sort of thing and don't have competing expensive hobbies, like flying antique jet aircraft or golf.
A Honda 1000 is a cool boy toy even if you don't quite need one often.
I have 2 Honda 2000iu's which I haven't needed since Katrina, but boy they sure were worth it then. You would not believe it how all the neighbors will will give you their gas in exchange for frozen Margaritas and ice when you can't get either one from FEMA.
Plus, the ATF agent next door guarded them with his AK-47 and let me use his gov't sat phone to call Mom since I kept it charged for him.
Whatever floats your C-Dory.
Cheers!
John

[colbysmith]

Not sure what brand Cpap you use, but I have the Resmed S9. There is no 12 vt adapter. However, with the humidifier removed, I run it off a 100 watt inverter plugged into my cabin accessory outlet. Running it all night (8 hours), along with using 2 of my LED cabin lights for several hours, and even an LED Anchor light, I have yet had any problem starting up the next day. I just recently installed a webasto heater, and waiting to see how well the battery holds up running that over night as well. (I have two batteries, one I think a group 24 the other 27. (I THINK). At night, I normally run off the larger battery. So I still have the smaller one to start from, but routinely just leave my battery switch where it is when I start up the next day. This probably doesn't answer your question, but have you thought about getting a newer cpap? (And if you are using a humidifier, I'd definitely turn that off while running on the boat.) Colby

[thataway]

Roger, There certainly advantages to low battery alarms--in fact I just got back in the house--a neighbor's boat has an alarm going off. I have no idea what it is, except is is not on fire, and not sinking (no wanter in the bilge). It could be a low voltage alarm--We will find out, when the owner gets back to me--IM, cell phone and computer don't get to him...

The Siren system is a complete boat monitoring system, and works very well. Expensive..

The Aqua Alarm (I have a complete inboard system for sale after the garage clean up). has a set voltage of 11.7 volts--a dead battery.

The first one, does have adjustable alarms. I prefer to look at the voltage every few hours. An alarm may go off during s sudden voltage drop. The monitoring systems do draw a small amount of current, but eventually can draw the battery down, if you don't have a charger on. But a good idea, if you don't want to watch your batteries.

[Aurelia]

Hi Peter, I love battery puzzles.

A few questions come to mind here.

What is the age and size of your house battery??

Were you ever able to power up the chartplotter and radio? Perhaps after the first few minutes or a bit later?

What is the age/condition of your starting battery?

What other power saps do you have on the boat?

Don't connect accessories directly to the start battery unless you don't have other choices Consider the bus bar setup mentioned above if you do have direct accessory connections to the house. Monitoring is a good idea whether you go simple and watch voltage, or go fancy and watch amp hours.

Greg

[Casey]

For what it's worth here's my CPAP / battery experience.

We are preparing for a summer of truck camping to Nova Scotia and Newfoundland. I plan to take my CPAP (Resmed Airsense 10, 24V) device but I was concerned at how much power it might consume.

The device runs on 24V, and by the time I tried to calculate the electrical consumption but after factoring-in everything (converting 12V to 24V, amps consumed, and all that jazz), I was totally confused. I even asked Dr. Bob for help, and although his response was great; I was STILL confused.

I figured there MUST be an easier way....

The boat batteries are both sitting in the garage. My theory was to take one of the fully charged batteries (Duracell AGM - SL34MAGM) and perform a "test." I took a battery to the bedroom and hooked-up the Resmed DC Converter to see how much battery power was ACTUALLY consumed. That worked like a charm. Here are my test results:

MON (1600 hours) 12.69V [possible erroneous voltage reading]
MON (2030 hours) 12.88V [CPAP connected, voltage check]
[sleeping]
MON (2130 hours) 12.67V [CPAP connected, voltage check]
[sleeping]
TUES. (0415 hours) 12.58V [CPAP connected, voltage check]
TUES (12Noon). 12.55V [CPAP connected, voltage check]
TUES (2100 hours) 12.49V [CPAP connected, voltage check]
[sleeping]
WED (0800 hours) 12.23V [CPAP connected, voltage check]
WED (1500 hours) 12.20V [CPAP connected, voltage check]
WED (2100 hours). 12.17V [CPAP connected, woot age check]
[sleeping]
THURS (0700 hours) 11.90V [CPAP connected, voltage check]
THURS (1345 hours) 11.86V [CPAP connected, voltage check]

As you can see, I kept the CPAP "connected" thru the entire period, including four nights of sleep. As far as I know the humidifier(warmer) feature was turned "on" but I seldom use it (there is an automatic feature that turns-off the humidifier if there is no water in the reservoir).

All-in-all the Resmed CPAP seems to use much less power (even at 24V) than I was expecting. With this info in mind I am pretty comfortable taking power directly from the truck battery for overnight CPAP use and rely on the running each day to recharge the battery. (But I still may take and emergency 'start battery.)

...did I forget anything?

Best,
Casey&Mary

[Bill K]

I have a inline switch in my AC line and will have one in my 12v line as well.
The Resmed does run at a very slow speed when not being used. ( at least mine does )

Bill Kelleher

[Aurelia]

Casey's example (thanks Casey!) is using a relatively small group 34 AGM battery rated for 55amp hours at the 20 hour rate. Many of you have group 27 or larger units with capacities in the 70-100amp hour range. It looks like he got two solid nights worth of use with no other draws so that is a starting point of reference for that CPAP unit.

Reminds me we have too much power, Bring on the freezer!

Greg

[Will-C]

We used two group 27 batteries on our previous boat. One was start and the other was the house both deep cycle. A simple manual battery switch 1 2 or both. When away from power we just set the switch on one battery. We used a 400 watt inverter that plugged into a 12vdc socket. Then a six way power strip plugged into the inverter. If the battery got low the inverter would go on overload and screech out an alarm you would not be able to ignore. We use a Res Med C-Pap machine also and never had any problems. We usually only spent a night at a time off the grid. Like Bob recommended a solar panel or a Honda generator might be in your future if you want to stay out more extensively than a night off the grid. We always carried a Honda 2000 for backup. That way we just plugging our shore power cord via adapter to the generator and let the boats battery charger do it's thing.
Our new boat has a two house battery bank another battery for the thrusters and a start battery all the same size and a switch to combine all if need be. Each bank has it's own separate on off switch The solar panel seems be able to keep up with things including a refrigerator freezer although some combine the two house batteries with the thruster battery giving them more power for multiple days on the hook. Even though I have a 1500 watt inverter that came with the boat I still use the little 400 watt inverter for my sleep machine and our charging phones, Ipads and camera batteries etc. when not connected to shore power. I don't want too start using the microwave etc. off the bigger inverter as I believe the bigger inverters are battery killers. Plus the ever present generator makes us feel like we have all the bases covered.
D.D.

[Marco Flamingo]

I was just looking into how I will monitor my batteries. I don't need anything very complex on a CD 16 and was looking for the tiniest monitor available. I just ordered one of these.

http://www.ebay.com/itm/171898210875?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It could be permanently mounted, or put one on each battery, or, using alligator clips, to diagnose voltage drop issues around the boat. You could even put one in the V berth, or even in parallel with the CPAP, so that you can see the state of charge during the night. All for $1.43 including shipping from China.

Some day we (or the next generation) will pay a very high price for this "free" stuff from China.

Mark

[Jazzmanic]

Wow, all great answers! I'll try to provide the details and recreate the scenario I was facing when the battery failed.

3rd day on the hook, no battery charging before the trip as the boat is stored at Twin Bridges (indoor stack with no outlets)

Deep Cycle Battery - Interstate SRM-24 installed May 2013
Start Battery - Interstate XHD-24M - installed May 2013

I did have a DVM installed in 12v plug in - I'm sure I checked the voltage prior to using the CPAP on that 3rd night but can't remember what it showed.

CPAP - ResMed Air 10 - DC 24v - 3.75 amps
ResMed 90w DC converter - DC output 24v -3.75 amps

Switch system - Blue Seas Add-a-Battery - installed exactly to specs
No direct connections to batteries except to switch and battery cable to positive and negative bus bars for each battery

I did turnoff the humidifier before hand, no other power draws during the evening except Perko Anchor light

When I took off the next day, no problem starting. About 5 minutes into the trip, noticed the GPS kept turning off and wouldn't stay on. After a few more minutes no power from GPS and VHF, concluded discharged battery. Plugged in DVM and noticed very low reading but don't remember exact number.

So to conclude, I'm assuming after three days on the hook and no prior recharging, the house battery was already discharged quite a bit, probably less than 50%. So the power drain wasn't entirely due to the CPAP but more likely due to the state of the battery voltage after several days on the hook.

The Blue Seas ACR is set to charge both batteries while underway, EXCEPT if one of the batteries drops below 9.5v at which time the ACR closes. I take that to mean it will not try to charge the discharged battery.
Add-a-Battery diagram
Click on the different scenarios in the middle of the page. Am I reading that correctly?
I did not try to combine the batteries while underway as I was afraid of discharging the start battery.

So.... here's what I think I should do after all your great advice.

You all confirmed my intuition that I shouldn't be connecting additional devices to the Start Battery, so I will probably buy an AGM battery to be stored in the cabin and connect a 12v outlet to it for use with the CPAP and probably a couple of other electrical items that don't get used much (seems a waste to use the battery only once a year for once device) but not the VHF or GPS. I will buy a hand held VHF so I won't have to worry about that going out. And if I anticipate staying out on the hook for days at a time, I will purchase a generator/inverter. I've been looking at the Ryobi RYI2200 2200 watt digital inverter generator. They're available for a great price on Amazon and seem to compare favorably to the Honda 2000. I will probably wait on the solar panels Pat. And obviously I'll do a better job of monitoring the battery voltage while on the hook and calculating the amperage draw of the devices in use.

Thanks all! Peter