Battery Monitors

[BALANCE]

Preface: I know very little (nothing) about this.

I have 3 Group 27 gel cell batteries that are about 4 years old. One is stand alone, the other two are banked. I have a Bluesea panel which has all the bells and whistles including a guage that shows how much juice is being used at any given time.

I have come to find out that this is unreliable and that one should have a battery monitor. Having just returned from a cruise where the tiller pilot and the chartplotter were constantly used, I discovered that I was perhaps too content with my (what seemed to me low usage) of juice. The gauge registering maybe 2 out of 20.

Not knowing how the batteries were set up (which was starter, which was house). Assumedly the stand alone was the starter... In my wisdom, to cover all bases, when the batteries are in use or the engine is in use I always turn the the battery thng to ALL. I have since heard that this is not a good idea.

How involved is adding a monitor, could a piker like me do it myself?

[Ceasar Choppy]

As Lindsey Lohan would say, "It's not rock science."

You will need to have a place close to the batteries to mount the shunt and then you'll run the wires (lots of small wires in a bundle) between the monitor, the shunt and the batteries.

You will, however, have to decide how you will configure your batteries. Either you keep it as is and hook up the monitor to your "house" bank, or you connect all three of your batteries together into one bank (which is what you are doing with the battery switch anyway), and hook up the monitor to this "bank."

There is nothing inherently "bad" about how you have it now, except you might confuse the monitor since it would be configured for the two battery bank and not three and would give weird readings when you flip the switch to "both"... perhaps this is the problem now? You might think about either isolating your third battery, or maybe adding another isolated starting battery that would only be cross connected in an emergency.

[Rachel]

Now here is another electronics piker chipping in...

If you have an engine, and you only have three batteries, isn't it a bit "dangerous" to use them with the switch on both (while you are not running the engine) because if you drain them down you wouldn't have a battery for engine starting? I thought that was why people usually kept one battery separate.

BALANCE mentions using the "both" position while using the batteries or running the engine, is why I ask (referring to the former).

I'm not a gadget person, but I have used a simple battery monitor (the old Link 1), and it was really handy.

Rachel

[BALANCE]

This is why I ask, cockpit conversations have gone like:

'We used to keep our batteries on 'all' or 'both' and we got into trouble once'.

Fortunately this has not happened to me, I do not have a lot of juice eaters, use lanterns more often than cabin lights and lantern for anchor light as well, no hot water and no pressurized water. The two things I mentioned before are the two biggest drainers, I have hesitated to use either if the engine is not running. Tthe single battery is supposed to be the starter and the banked two for the house?

If I get a monitor, I would want it to monitor both the single and the double. (Q, forgive me but I will have to read your post about 6 more times for it to sink in).

[Ryan]

Balance

The Victron BMV-602 would be a good monitor to take a look at for what you seem to need.

Ryan

[Tim]

I think you'll find that whatever monitor you choose, it will be fairly easy to install with the included directions/schematic and some basic wiring knowledge.

[Chris Campbell]

I installed a Xantrex XBM in my last boat, and loved it. It completely took the guess work out of knowing the state of the battery, and eliminated my worry that I was running it down. Well worth it.

I also had two banks - a group 27 start battery and an 8D house battery. I put the monitor on the house bank and ignored the start battery since I didn't use the start battery at all - it was my emergency backup to get the motor running should the house battery get too run down, which it never did. I would put the switch on "Both", or "All" for a short period of time while motoring to keep the start battery topped up, but for the most part I just used the one 8D.

The battery monitor doesn't get confused by having the switch on All or Both since it measures current right at the negative post of the battery bank you're monitoring - so it only measures what comes and goes from the one bank, regardless of what position the switch is in. The instructions that come with it for installation are quite easily understood - and quite explicit on this.

As for how to use your battery banks, you should avoid using the start battery for anything but starting - the whole point of having separate banks is to avoid running all the batteries down and not being able to start the motor to charge - by keeping the start battery in reserve you avoid this possibility.

From the sounds of your usage of the batteries, you're not running them down very much anyway. Unless they're in bad shape, chartplotter and tillerpilot should run for at least 24 hours off of a pair of group 27 gel batteries. You can always tell what the state of charge (roughly) of your batteries is by checking the voltage at rest. This means you turn everything off for a couple of hours and then check the voltage. In rough terms, 12.7V is full, 12.2V is about 50%, and you don't want to go below 50% if you can avoid it. Here's a page that talks about it - there are plenty more resources like that if you search for them.

Sorry about the lengthy babble! The main thing is that you're easily capable of installing a monitor, and you probably aren't running your batteries down as much as you might think you are, based on your stated usage.

Cheers,

Chris

[David VanDenburgh]

I can recommend the Xantrex Link 20. I installed one on Ariel a couple years ago and have been very happy with its capabilities. It was easy to install (really, routing the wires was the "hardest" part), and it monitors our two six-volts, wired in series, and a single 12v starting battery. Just this summer the monitor helped us catch and diagnose a battery problem.

[Maine Sail]

You really need to think of this a system. You'll also want two banks, and by using the "BOTH" function you leave yourself with only one bank. This is a very simple concept but will require a basic understanding of function.

1) House Bank: This will consist of two, three or four batteries purchased at the same time and wired in parallel if 12v or series/parallel if using 6v batteries and can be wired to position #1 on the batt switch.

2) Emergency/Start/Reserve Bank: This will consist of one battery with ample marine cranking amps to start your motor. This will get wired to position #2, or second position for the second or back up bank.

You do not need or want to be switching back and forth between house and emergency banks with the battery switch as this can leave room for human error. Any sufficiently sized deep cycle house bank will and should re-start your motor at 50% depletion with zero issues. I have even once re-started at roughly 15% capacity. I have been starting on the house banks on my boats for well over 20+ years and I've never understood why anyone would need or want to switch back and forth on a small aux engine. Sure if you have a huge Caterpillar diesel then a dedicated start bank might be necessary but they generally are not necessary on small sailboat aux engines. When we get to our boat we simply flip to bank 1 (house) and when we leave we switch it off. It's that simple..

3) Charging: You'll want to add a battery combining relay or "ACR" or an Echo charger to keep the emergency bank topped off. I personally prefer the Echo Charger but either would work fine. This allows you to only use position #1 yet still charge the emergency bank.

One more upgrade you'll want to do while in there is to run your alternator output wire directly to the house bank. By doing this you will no longer run the risk of frying the alternators diodes by passing through the off position on the battery switch or having a guest flip the battery switch off, at the end of a sail, with the motor still running, thinking they are doing you a favor. If you run the alt directly to the house bank you should really add a automatic charging relay or an Echo Charger.

4) Battery Monitor: You'll definitely want a monitor for at least the house bank. It is not really necessary to monitor the emergency bank as it will rarely if ever get used and a quick look at resting volts and yearly load tests will confirm it is up to snuff. I use a Xantrex XBM, which was actually made by Victron. If I were to buy a new monitor today it would most certainly be a Victron BMV-601. I have a dead link 10 in my barn and many unproductive hours trying to deal with Xantrex (they stink at customer support) on a fix for the bugs plaguing it. The Victron is also a much simpler installation with simple plug and play Molex type connectors..

So in summary

House & emergency banks, you could re-use one of your old batteries as the emergency bank battery, ACR or Echo charger and direct wire the alt to the house bank. This is about as fool proof a system as you can get on a small budget. Oh and you NEVER want to "combine" banks 1&2 in a situation where one bank is dead!!!

It sounds like you have room for four total batteries? So I'd suggest three 12V deep cycle group 29 or 31 batteries, wired in parallel as one big bank, and one single deep cycle or starting grade battery with sufficient MCA's for your engine as the emergency bank.

[BALANCE]

Thanks all for the comments and advice.

A rudimentary understanding of wiring is clearly a necessity, of which I have none. Time to start.

A few of you have commented how the bank would be the starter and the stand alone would be the house. I would have (and did) guessed the opposite. I would have thought that two batteries are better than one for all the typical uses and save the single for just starting the engine.

It appears that my logic is wrong... And so it goes.

[Chris Campbell]

Oops - giving wrong impressions already! A battery bank can be a single battery or more than one - the concept is just that a single bank of batteries are all wired together (so a single battery, not wired to any others, is also a bank). So you have two banks - one with two batteries (probably the house bank, as you have said) and one with a single battery (probably the start bank, or as mainesail put it better, the emergency start bank).

Don Casey's books are pretty simple to understand, Nigel Calders are better, but require a deeper understanding. I'm sure there are others that other people are familiar with that are good also...

Good luck, and don't hesitate to ask questions - the sum total of the wisdom of this board is quite vast.

Cheers,

Chris

[BALANCE]

Yes but the patience....

Thanks for the clarification! I'm not totally illogical.

I have both of those books AND the 12V bible (she says with crossed eyes)

[Chris Campbell]

While browsing first Xantrex and then Defender, I discovered the Battery Bug. It is a battery monitor but also a battery condition analyzer - it determines the batteries remaining capacity by using a test of the battery's actual state, vs. keeping track of amps in and out. I haven't read enough yet to know that it works properly - but if it does, I think this'll be my next battery monitor - it'll tell me about the state of charge of the battery as well as it's condition - bonus!