Connecting a Battery alarm?

[nzfisher]

Aqualarm makes a battery alarm unit. I believe it is activated when voltage falls to 11.7 volts. My question is does this make sense to install for the house battery? Or is your battery toast if you let it get this low. Want to have some kind of warning to prevent draining battery when on the hook. Advice appreciated from those spending lots of time on the hook with no other charging system. Planning a trip to west coast of Vancouver Island in July. Thanks

 

[Levitation]

mmmm, how bout bending over and looking at the voltmeter :mrgreen:
OK, fun stuff aside - yes, 11.7 will do damage to your battery set.
And monitoring your power draw will do far more to prompt you to control power use as opposed to draining the batteries willy-nilly until you hear the final dying gasps from the alarm.

I would suggest spending the money for the alarm on an additional battery (or two) in the starboard locker (what I did)
And you can replace all internal lights and the anchor light with LED units (if not already done)
And a heavily insulated ice chest on the swim platform with dry ice bricks in it will hold food for x days without using battery juice.
And you run the engine as necessary to protect your battery set.
And lastly, add solar panels.

 

[Hydraulicjump]

I have one suggestion that has worked very well for me. The Balmar Smartgage

http://www.balmar.net/?page_id=15245

has been talked about in earlier posts on this site. It is an alternative to the traditional amp monitor. It is simple to install (no shunt) and does a really good job of monitoring the capacity of your battery. Along with being useful for monitoring battery use/remaining capacity, it also has alarm settings to let you know when voltage gets too low. I really like it because the voltage you are reading on your panel is in most cases not the actual voltage of the battery, especially if there is either a load or a charge on the battery (which is most of the time when you are in the boat).

Hope this helps.

 

[Osprey]

I like the suggestion regarding the Balmer Smartgauge. If you click on the link above, note that the circuit diagram shows 3 house batteries. What I have done is tie the thruster/anchor windlass battery, via an added battery switch located in the battery compartment, into the house bank. This gives a 50% increase in the house bank capacity. I always have the engine running when using the thruster or windlass so I not concerned that the thruster battery might get somewhat discharged contributing to house duty while at anchor.
About 90% of "overnight" time on my tug I am anchored out, so I am concerned regarding house battery capacity. LED lights are good energy savers. After about 3 nights it is time to recharge the house bank . To accomplish this I run a 1000 W Honda generator. I have upgraded the factory 20A battery charger with a 30A model. This winter I installed the original 20A charger at the back of the cave, so running both I can have 50A total charging capacity. I will not know what effect this addition of charging capacity will have until the system is put to the test this coming cruising season. One can get up to 150A charging running the engine, which is the norm when underway, but I consider engine running while at anchor a bad idea.

 

[Levitation]

I suspect that having two smart chargers attempting to charge the same set of batteries will result in
the controllers bucking each other. If one charger is a tenth of a volt stronger than the other then one could just go into float mode and let the other do all the work. Or they could oscillate wildly back and forth and possibly overheat. Or they may both go into shut down and sulk. Hard to predict.

 

[Osprey]

On boats with high capacity battery banks it not uncommon to use more than one charger to achieve sufficient charging current. I have tested both chargers working together and noted that they share the load. What I have not been able to test yet is will I get both chargers pumping out full rating current into significantly discharged batteries. So far I have only been able to test when the single charger, working alone, was producing less than the design maximum. I have installed the second charger with AC power as a plug-in to the AC outlet located in the inner back sidewall of the cave. With this arrangement I can use either charger alone or use both at the same time.
My boat does have a "smart" solar panel controller and the single smart battery charger and the solar system work together without problems. Perhaps not an exact comparison but an indication, I think.
I initially had some concerns expressed above by Levitation but I have taken the view (hope?) that with a single charger there are 3 charging outputs working together and with 2 chargers there are now 6 charging outputs working together. Note that as supplied from the factory, our boats have 3 charging lines outputting to 3 banks but once the ACRs close all the batteries and therefore the charger outputs become a single system. The 3 output lines carry about equal current to the battery group with the sum current being the amperage displayed on the charger panel.

 

[JeffE]

My CB31 has Universal Battery UB121100 AGM batteries, which are documented as being limited to 15A maximum charging current (much lower than, say a Lifeline AGM, which can absorb up to 5X the Ah capacity in current during bulk charging).

So if you are charging 3 UB121100 batteries in parallel, the current shouldn't exceed 45A. I don't know what will happen if you provide the opportunity for higher current -- my guess is the internal resistance of the battery will either limit the charge current (good) or raise the battery temperature (bad). Or both (probably not good).

That said, with Lifeline AGMs, I've had very good experiences with multiple, parallel, charging sources. But with these UB AGM batteries, it looks like they can't accept high charge currents.

Jeff

 

[stwendl]

I think the acrs will not close under normal charging conditions and only kick in when consuming or when a single charger ( alternator under motor power) is active

 

[HRowland]

The Smart Gauge looks very nice and is simple to install. A nice feature is that it adapts as your batteries age. A good review is here:

http://www.pbase.com/mainecruising/smart_gauge

I installed a Victron battery monitor in my R27. Several parameters need to be entered so it understands your battery bank. You can also configure alarm levels based on voltage, state of charge, etc. It is more difficult to install because it monitors current (via a shunt in the ground lead) in addition to voltage. An advantage is the display of current into (charge) or out of (discharge) the house bank. I combined the thruster/house banks into a single 3 battery bank. This has worked very well. I installed 600A bus bars, one on ground and the other on +12V, to improve the balance between the batteries and allow easy connection of the current sense shunt for the monitor.

ACRs sense voltage on both batteries that they are connected to and use this to decide when to connect or disconnect the batteries. During charge they will be connected, so all of your batteries end out in parallel during charging. If you want the details you can visit the Blue Sea web site to see the specific voltage thresholds and time delays to connect (combine) and disconnect. There are also conditions where it will not connect the batteries even if one is being charged, such as if one battery is very dead, it will not combine to protect from a possible battery fault, such as a shorted cell. The LED indicates the status, again the Blue Sea site has details. I installed a remote LED that I can see from the helm to monitor the ACR status.

An AGM limited to 15A charge current is very strange, normally AGMs accept very high charge rates. When charging from the engine alternator the current can be much higher than even 45A for 3 in parallel, when my house/thruster bank is partially discharged I see over 100A charge current at idle when the engine is first started.

Paralleling multiple smart chargers works well. They will not oscillate or burn out. I added a 45A charger to supplement the factory 20A charger. I run both in parallel when using the genset. I do initially see over 65A total charge for partially discharged batteries during bulk charge phase. The Mase genset has a 10A or so charge output, this gets added to the two battery chargers, if the current drawn by the boat is low I will see 70A or so. During bulk phase when the battery voltage is below the absorption voltage settings for both chargers you will get maximum current from both chargers. As the battery charges and the voltage climbs the current will begin to taper when the voltage reaches the lower of the absorption settings between the two chargers. This normal, eventually one of the chargers will be delivering most of the charge current which is not a problem, the battery charge acceptance rate is much lower at this point anyway.
Many of you parallel charge sources routinely anyway! If you have solar and are also running your battery charger from shore power or genset you have two chargers in parallel.

Howard

 

[Osprey]

Jeffe, we seem to have different data on the maximum charging current for UB12100 AGM batteries. The data sheets I have state that the maximum initial current should be 33A or less, per battery. The R-27 has a total of 4 batteries in the circuit. Well, 4 when the ACRs are closed. Excess current would overheat the battery with the possible loss of electrolyte. One wonders what happens when underway with an alternator capable of producing up to 150A is doing the charging. The alternator output on my tug, as wired by the factory, initially feeds into the house batteries.

Stwendl, you are mistaken as to when the ACRs close. They will close if the terminal voltage reaches 13.6 V for 30 seconds or more and will close at less voltage, 13.0 V, if present for 90 seconds or more. Such closing voltages can be achieved via a battery charger, or the alternator ,or even a solar panel. When charging using the battery charger, I routinely check ACR operation. When the ACR is closed one can see a green LED glowing on the ACR cover.

 

[CAPTCRUNCH]

With due respect to the late Alessandro Volta and his disciples, my tug and I have done well for the last two years by applying my rocket scientist uncle's maxim "If it ain't broke, don't fix it." In practical effect, this means my involvement with the ship's electrical system has been limited to switching things on or off as appropriate. Tempting fate, I suppose.

 

[knotflying]

I kind of concur.The old adage KISS seems the way to go for me. The electrical system is quite sophisticated as is. I monitor my voltage and correlate it to state of charge. If during the night my c-pap turns off my voltage is too low. That has never happened though. I replace my flooded batteries every three years and so far, knock wood, life on the hook is good.

 

[CAPTCRUNCH]

I kind of concur.The old adage KISS seems the way to go for me. The electrical system is quite sophisticated as is. I monitor my voltage and correlate it to state of charge. If during the night my c-pap turns off my voltage is too low. That has never happened though. I replace my flooded batteries every three years and so far, knock wood, life on the hook is good.

Elegant alarm device...skipper stops breathing = low battery :lol:

 

[knotflying]

I kind of concur.The old adage KISS seems the way to go for me. The electrical system is quite sophisticated as is. I monitor my voltage and correlate it to state of charge. If during the night my c-pap turns off my voltage is too low. That has never happened though. I replace my flooded batteries every three years and so far, knock wood, life on the hook is good.

Elegant alarm device...skipper stops breathing = low battery :lol:

You'd be surprised. As soon as that c-pap turns off I wake right up. Actually, if the power gets low the CO detector starts to beep as well. So the question is, are my batteries low or am I dying from CO poisoning? another :lol:

 

[nzfisher]

Thanks for all the responses from the simple to the elegantly engineered. I am leaning toward Levitation's solution of adding 2 extra batteries (AGM's to match existing) and having someone else make up the cables. I think cables will be around 8ft long so I will be going with #2. Hopefully I am not underestimating what is needed here. I like the idea of putting money into more capacity rather than into gauges. I can't imagine spending more than one night on the hook without checking crab traps, fishing or tooling around the next day. I like the CO2 alarm failsafe although it reminds me a little too much of Schrodinger's cat.