Ammeter/battery brain fog

[sbrin]

My brain totally fogs up when reading about electricity. All these volts, amps and electrons. I think I have a massive resistor wired in up there (crimped or soldered?) preventing me from really understanding all of this.

So, I have 10 year old rolls/surrette batteries in 2 banks: 2 group 27's in parallel and 2 - 6 volt in series. Cruise for 1 week at a time and no solar/etc, just engine alternator recharging. Both banks seem to read about 12.55 - 12.63 after the surface charge has dissapated. When cruising, the 6 volt bank runs my lights, fridge, etc for a full day before it goes down to 12.3 - 12.4, after which I run the motor (Balmar 90 or 100A dual bank alternator) for 3/4 - 1 hour. The 12 volt bank runs all of my instruments, plotter, fridge, autopilot (not used much under sail), etc while sailing and reads about 12.4 - 12.45 at the end of the day.

My maintenance has been to fill electrolyte in the spring and fall, keep a small flexable solar panel going through a cig lighter adapter while at the mooring, and keep the charger on through winter layup on the hard (ends up in float mode with minimal electrolyte evaporation.

Regards,

Steven

But because of their age, I suspect I should get new batteries. Which has led me to read all about batteries and monitoring systems.

So I realize I should add an ammeter to my system (on top of the digital v-meter I already have). The Victron unit looks pretty good to me and I think even electrically challenged me could install this.

Question for all: If I install the neg/pos terminals of the ammeter in the breaker panel terminals rather than at the actual batteries, would I need to re calibrate the ammeter every time I turn the battery switch to "on" after being off? It would seem to me that the advantage of connecting the positive at the breaker panel is that I will get readings of whichever battery bank is being used at the time and avoid the need to get the 2 bank model (Simpler is better for me).

Appreciate any electrical guru advice out there (keep it simple, if possible!!).

Regards,

Steven

[Badsanta]

Sounds complacated with 4 battery banks. Does your solar charge them all? I would go with a battery monitor insted of an amp meter but wiring it all to a common ground would take some figuring. If it works just leave it but if I had to replace the batteries I would change to one bank with a start battery charged with an ecocharger it would bo so much easer to keep it charged

[CaptainMurph]

The first thing is to understand the difference between an ammeter and a voltmeter.

An ammeter measures the current passing through a certain portion of a circuit and is connected in series - positive to a source, negative to contine to the rest of the circuit. So, an ammeter wired to monitor the current flowing from the battery (or battery bank switch output) to the distribution panel would be installed in the existing feed wire.

A voltmeter measures the voltage or potential across a circuit and is connected in parallel - positive to positive and negative to negative (ground). A voltmeter wired to monitor the voltage from the battery (or battery bank switch output) would be connected to the positive source (which is also connected to your "load" or distribution panel) and the negative to ground.

If you have a feed from your battery output switch (the common terminal for output - not #1 or #2) to your distribution panel, you would cut that wire and install the ammeter "in-line" with + to one side and - to the other side of the "cut". An internal bypass (shunt) in the meter takes the actual current flow and reflects the value on the meter.

The difference between the two meters and their connection is simple: The connection from the source to the distribution is made by the ammeter. No other positive connection! This means that the wire from the source to the distibution carries all of the current and must be sized appropriately (usually #8 or even #6).

Murph'
S/V Amalia
1965 Cal 30
Muskegon, MI

[sbrin]

Sorry for the mis-understanding - I have 2 banks: 2 6 volts and 2 12 volts.

I am aware of the difference between volts and amps - that is why I I have decided to add the ammeter (I have a voltmeter already)

Originally Posted by CaptainMurph

If you have a feed from your battery output switch (the common terminal for output - not #1 or #2) to your distribution panel, you would cut that wire and install the ammeter "in-line" with + to one side and - to the other side of the "cut". An internal bypass (shunt) in the meter takes the actual current flow and reflects the value on the meter.

Murph'
S/V Amalia
1965 Cal 30
Muskegon, MI

Yup, I think I get this - but would this mean that every time I turned my battery switch on, I need to recalibrate the ammeter?

Regards,

Steven

[CaptainMurph]

I assume you have two banks of multiple batteries in parallel connected to an "AB" switch.

If that is the case, my original post stands: The output from the switch to the panel - with an ammeter installed as noted - shows the current draw from either bank 1, bank 2 or both banks if switch is in both position.

I don't know why you are concerned with calibration since the meter will return to zero when the switch is turned to off and then indicate current flow to the bus when turned on. In reality, the ammeter (internally) reads the voltage across the shunt and translates the indication into current flow as the result of the corresponding voltage drop. When off, there is no current flow or voltage.

[Badsanta]

I'm sure the 2 -6 volts are wired as 1 large 12 volt. I still dont see the advantage of the two banks of 6 and 12 volts batteries. 6 volts batteries are great but I would still have one bank of the same type of batteries. If I had to buy new batteries thats what I would do. I would also install a Link type battery monitor instead of just a amp meter. But thats me.

[cal40john]

He said he was looking at Victron. It doesn't look like Victron offers an ammeter at all, only battery monitors.

Battery monitors - Victron Energy

So yes he will have problems switching and turning things on and off. You need a monitor for each bank. Or a 2 bank battery monitor (I didn't find one).

Victron and Xantrex makes something that computes amp hours on one bank and only monitors voltage on a start bank.


Battery monitors - Victron Energy

[Badsanta]

Yes and he also stated that he may need new batteries but does not say why. I suspect undercharging. I was just tring to start some thought in a broader way. It is hard to concider what your use is, how much you need, how to make it and how to store it. Lots put on a huge alternater but add no storage batteries you make lots of power and no were to put it. Or add batteries and no better way to charge. Its just more than one thing .

[sbrin]

Originally Posted by Badsanta

I'm sure the 2 -6 volts are wired as 1 large 12 volt. I still dont see the advantage of the two banks of 6 and 12 volts batteries. 6 volts batteries are great but I would still have one bank of the same type of batteries. If I had to buy new batteries thats what I would do. I would also install a Link type battery monitor instead of just a amp meter. But thats me.

Poor articulation on my part:

2 6V in series= 12V for one bank. 2 12V in parallel=12V for second bank. If I go ahead and replace the batteries this spring, I will buy 4 6V units, 2 for each bank.

Yes, I was looking at both the Victron 600S and 602S monitor systems.

Comments?

Regards,

Steven

[Zil]

Your "question for all" is a little confused for me. What do you want to learn with your amp-meter. You can wire it to just show charge-discharge of which ever bank you chose. Charge-discharge of the whole system. But the amp-meter will only show what is going on at the moment you look at it. I think you want a battery monitor to show the accumulated charge state of the batteries?

[sbrin]

Originally Posted by Zil

Your "question for all" is a little confused for me. What do you want to learn with your amp-meter. You can wire it to just show charge-discharge of which ever bank you chose. Charge-discharge of the whole system. But the amp-meter will only show what is going on at the moment you look at it. I think you want a battery monitor to show the accumulated charge state of the batteries?

Yes, a Battery Monitor is what I meant when I have said ammeter above which is why I am looking at the Vitron 600 and 602.

[Zil]

Both good choice. If you keep the banks separate, you may want two monitors. You will be well served when you replace your batteries to keep one large house bank and one small starter battery.

[donradcliffe]

Originally Posted by sbrin

My brain totally fogs up when reading about electricity. All these volts, amps and electrons. I think I have a massive resistor wired in up there (crimped or soldered?) preventing me from really understanding all of this.

So, I have 10 year old rolls/surrette batteries in 2 banks: 2 group 27's in parallel and 2 - 6 volt in series. Cruise for 1 week at a time and no solar/etc, just engine alternator recharging. Both banks seem to read about 12.55 - 12.63 after the surface charge has dissapated. When cruising, the 6 volt bank runs my lights, fridge, etc for a full day before it goes down to 12.3 - 12.4, after which I run the motor (Balmar 90 or 100A dual bank alternator) for 3/4 - 1 hour. The 12 volt bank runs all of my instruments, plotter, fridge, autopilot (not used much under sail), etc while sailing and reads about 12.4 - 12.45 at the end of the day.

My maintenance has been to fill electrolyte in the spring and fall, keep a small flexable solar panel going through a cig lighter adapter while at the mooring, and keep the charger on through winter layup on the hard (ends up in float mode with minimal electrolyte evaporation.

Regards,

Steven

But because of their age, I suspect I should get new batteries. Which has led me to read all about batteries and monitoring systems.

So I realize I should add an ammeter to my system (on top of the digital v-meter I already have). The Victron unit looks pretty good to me and I think even electrically challenged me could install this.

Question for all: If I install the neg/pos terminals of the ammeter in the breaker panel terminals rather than at the actual batteries, would I need to re calibrate the ammeter every time I turn the battery switch to "on" after being off? It would seem to me that the advantage of connecting the positive at the breaker panel is that I will get readings of whichever battery bank is being used at the time and avoid the need to get the 2 bank model (Simpler is better for me).

Appreciate any electrical guru advice out there (keep it simple, if possible!!).

Regards,

Steven

1. If it ain't broke, don't fix it. Putting in a monitor will not make your batteries stronger; they are very good batteries and they seem to be meeting your needs.

2. It's not quite clear how you use your batteries--do you use one bank during the day and one bank at night,and when you say a full day do you mean 24 hours?? In your situation it would be more efficient to either leave the batteries paralleled or to drain equal amounts out of each bank before your start to charge.

3. How do you start your engine?? On a separate battery? On the bank you have been using? On both banks?? As you have no other charging source, its very important to start the engine before the batteries are too dead to start it. The common practice today is to have one large bank for the house loads and one separate starting battery, which is nearly idiot-proof.

4. The shunt on a battery monitor is put on the negative (ground) side of the batteries. If you want to measure total energy taken out of both batteries, you would connect the negative wires from both batteries to one side of the shunt, and the other side of the shunt to the boat's ground bus. If you want to measure the energy taken out of each battery, you would need a shunt from each battery's negative cable to the ground bus, and a dual battery monitor.

5. Your batteries have a nominal new capacity of about 200 amp-hours for each bank, which should be plenty for your mode of use. A resting voltage of 12.3 is indicative of a half-charged battery, so may have taken about 100 amp hours out of one of your banks if it was new, or maybe 70 amp-hours out of an old bank. That is consistent with your described loads for 12 hours, which are maybe an average 3 amps for the fridge, 3 amps for the autopilot, and 2 amps for the instruments and VHF.

6. Your 90 amp alternator is really good for about 75 amps once it warms up. It is hooked to both batteries, and will put 35-40 amps in each if they are both discharged, or 70 amps into the discharged battery if the other one hasn't been used. After an hour, the charging rate will be down to maybe 60 amps if both batteries were heavily discharged, or 30 amps if only one was.

7. You need to put back about 1.2 times the energy you took out of your batteries, and I seriously doubt that an hour a day is going to get them back to a full charge. That's OK for a week's cruise, because you have a fair bit of excess capacity. However batteries HATE sitting around not fully charged, and if you put the boat back on the mooring after your cruise without running the engine for at least 4 hours or plugging into a dock charger for 24 hours you are going to need new batteries a lot sooner.

[Zil]

Don, all good advice and true. The monitor may help for a understanding of his state of charge and lead to better management.

[sbrin]

I appreciate all of the above and agree with all of Don's post. I will be installing the Victron 600 this fall so as to get a better idea of how my energy use is affecting my reserve in each bank.

I am leaning towards keeping these 10 year old batteries as they appear to be doing pretty well (although I am aware that they are living on borrowed time.