Freezer and Charging in neutral

[ArtJ]

I have just purchased a CF-025 small Dometic freezer and a Coleman
TEC cooler.
I think the Dometic will draw 2 to 3 amps,possibly the same for the TEC
Cooler.

I have 2 die hard Deep cycle Marine wet cell batteries.

Questions are as follows:

1. How often does the Dometic need to be on and draining the battery when not running the engine?
2. How often in practice does the engine need to run to keep the
battery up and out of harm?

3. Don mentions that the Atomic 4 doesn't like to run in neutral.
How long should it be ran.

4. What exactly wears out in the transmission and how difficult is it
to replace?

Thanks very much

Art

[ArtJ]

I am not sure what happened to the long chain of responses that were
posted here?

At any rate, I have just purchased a Honda eu1000i 1000watt generator.

I will try and run the Dometic "25" on a fully charged die hard deep cycle
battery and see how long before the battery is discharged.

I assume that I will need to run the honda as a battery charger, not directly
running the freezer. I will also set the cooler for 29 degrees Farenheit.
This may take a week or so before i can do this.

[sastanley]

Art...no sense in ruining the battery...only discharge to 50%...that will be the real-world type test you are looking for anyway. Discharges past 50% of capacity greatly reduce battery life and their ability to hold a charge.

This is exactly why when people say they need 100Ah per day (assuming they will be recharging daily), they have 200Ah of capacity.

Please ignore me if you already know this..not trying to talk down to anyone.

[ArtJ]

Thanks for the great information.

So 100 ah means 10a for 10 hrs? Do you know what the ah rating of the
typical large marine r/v deep cycle battery is off hand?
otherwise would need to incorporate a ammeter or percent charge meter.
Also, I believe the Dometic 25 can be for " low med, or high" voltage
reading on the battery, which it uses to set limit for shutting itself down.




thanks again

Art

[sastanley]

Yes...a 10amp draw for 10 hours should consume 100Ah of battery capacity. (or the same ratio, 1amp for 100 hours)

"Typical" I think varies from manufacturer to manufacturer...I think the holy grail of batteries is being able to pack the most amphours into the smallest container with the least weight. Li-Ion, which are what most of us have in our cellphones and mp3 players is a more current example of available power to weight technology..I think it is still too expensive to be practical for the average consumer on a larger scale like 12v systems..although folks with money and sponsors (like the Mini 6.50m class for example) I think are now using Li-Ion (less weight) and solar recharging only (still less weight, no generator or fuel on board!) to power their boat's electrical systems across the Atlantic. I think one downfall of Li-Ion I remember reading though is moisture...I think these systems have to be sealed from getting flooded, leaking, etc..

Back to the real world, for reference, my cheapo 12v wet-cell Group27 battery is 85Ah I think.

One way to get more Ah for less money is to put two 6v batteries into series..they then act like a 12v battery and charge like one, but pack a lot more Ah for the dollar. You can also parallel 12 v batteries for more Ah too..I think this is what Neil is doing with his house bank setup.

You have just about tapped all of my useful knowledge on batteries at this point...I am sure others with more will jump in.

[ArtJ]

Thanks very much for the useful information.

I think my die hard deep cycle marine r/v batteries have around 100 amp hrs.
Therefore; if i am using a freezer which draws 10amps at 50% duty cycle
(equivalent to 5amps at 100% duty cycle?) I could run at:


100 amp hrs/ 5amps = 20 hrs /2 for safety factor = 10 hours running time
between charges.

This would be long enough to complete a days sailing or to sleep without
charger running or to go ashore for the day.

Next I wonder what the yamaha eu1000 would need for time to charge
battery again? I also wonder what actual charging voltage it puts out.
The Dometic 25 cautions against using fast chargers , assumably because
they put out too high of a voltage

I am assuming the boat alternator (60a ) could charge
it in 20 minutes or so?

Regards

Art

[Dave Neptune]

Art the charge goes in as it goes out IE 100AH battery half drained would take just under an hour IF you can get 60AH out of the alternator, probably more like 45AH due to RPM limitations.
I have 270AH house set up with a pair of 6-volt batteries with the stock alternator and cruising with my Indigo at 2000RPM i get about 25+Amps. It takes me 6+ hours to charge if they go dead and over 3 hours at half drained.
I can sit at the Island for 10 days with no refridgeration (a well insulated ice-box) using the DVD, stereo, electric head and lights and still start on the house batteries most of the time, unless my wife or daughter leave the light on in the head which they do too often.

Dave Neptune

[ndutton]

My understanding of the alternator's output is that it's on a sliding scale dependent on the level of discharge of the battery.

Oversimplified, the alternator tries its best to maintain 13.8 volts (I know, that's an old school figure but it's good enough for our example). If the battery is pretty well discharged it might read 11 volts so the alternator will pump out just enough juice (amperage) to bring the combination (alt output + battery) up to 13.8. A deeply discharged battery will require more amperage from the alt than a slightly discharged batt. As the batt approaches a full charge, the alt output lessens, ultimately to a trickle.

If you have multiple batteries with one discharged and the other charged, recharging only the discharged batt (as opposed to both simultaneously) will require dramatically less time. If you recharge both, the voltage will average between the two (higher than the discharged batt alone) and the alt will adjust its output to the average.

I have a 100 amp alternator. If the condition of my battery bank requires 20 amps to maintain 13.8 volts, then that's all the alt will put out, any more will damage the batt. In this case the original 35A alt would perform the same and I wasted my money on the mondo alt. On the other hand, if the batt bank requires 60 amps to maintain 13.8 volts, the mondo is up to the task.

OK, before you sparkys jump all over me about 3 stage charging and the like, remember I qualified this as oversimplified.

[ArtJ]

I believe you mentioned in another posting having 4 batteries to use for
refrig and 1 for starting. I am curious- how do you have them connected?
i.e. Are they tied in parallel pairs of 2 with a transfer switch between
pairs? Or do you have some other scheme that maybe automatically
switches banks.

Thanks for all the information appreciated.

Art

[ArtJ]

Originally Posted by Dave Neptune

Art the charge goes in as it goes out IE 100AH battery half drained would take just under an hour IF you can get 60AH out of the alternator, probably more like 45AH due to RPM limitations.
I have 270AH house set up with a pair of 6-volt batteries with the stock alternator and cruising with my Indigo at 2000RPM i get about 25+Amps. It takes me 6+ hours to charge if they go dead and over 3 hours at half drained.
I can sit at the Island for 10 days with no refridgeration (a well insulated ice-box) using the DVD, stereo, electric head and lights and still start on the house batteries most of the time, unless my wife or daughter leave the light on in the head which they do too often.

Dave Neptune

Hi Dave

while I have 2 die hard marine rv batteries I have never
really discharged them because I have drawn very little power from
them when at anchor only a couple of nights and maybe a small tv
for 3 hrs at most, then running under power daily between ports.
Adding refrigeration and /or small freezer ups the draw considerably.
thanks for the input

Art

[ndutton]

Art,

Shawn's mention of my battery system was right on. I have 2 house banks of 2 batteries each and a single engine starting battery, all controlled by 2 manual battery switches. I've attached a drawing of the system. I haven't figured out how to create a pdf in landscape format so you'll have to rotate the pic to read it.

I've read on this site how many members love their automatic battery combiners but as I've said before, I'm really old school. The manual switches work for me, I think it's a repressed control issue.

I believe you mentioned in another posting having 4 batteries to use for
refrig and 1 for starting

I should clarify your comment slightly. I have no battery specifically dedicated to refrigeration but rather an increased general house capacity due to the refrigeration load.

[ArtJ]

Thank you Neil

I appreciate the drawing.

[ArtJ]

I am considering adding an addition bank of 2 batteries, similar to Neil's installation. The area I have available is quite close to the flux gate compass
for the autopilot. I know that steel affects the flux gate negatively, but am
not sure whether the lead in the batteries would adversely affect the
flux gate compass.

[ndutton]

Art,

The lead by itself shouldn't affect the fluxgate. I'm more concerned about the resultant gauss field around the battery cables when current is flowing. You can minimize this by twisting the cables together as they leave the battery area (the positive cable field is equal and opposite the negative cable field thereby canceling each other out) and also with the addition of a non-ferrous grounded metallic shield around the cable bundle.

Relocating the fluxgate may be the easiest way to go.

[ArtJ]

Thanks again Neil

Relocating the fluxgate may be a little problematic as the manufacturer
recomended it being close to the centroid of the boat.

By a shield, are you referring to mu- metal? I am not sure where to get
that, its cost ( I believe it to be very expensive ) or corrosion rate.
Possibly a aluminum faraday shield would work?.

Isn't it EMI Electro- magnetic interference that mostly would be affecting the compass?

I know that twisting the cables ( not commonly seen on boats) is great
for reducing noise RFI radio frequency interference.

Regards and thanks

[ndutton]

Either way, we're talking magnetic influences wherever they originate.

Boats, maybe even more so than everyday life, are a compromise. I'd go ahead and put in the batteries and then see if there's a change in autopilot performance. If so, I'd experiment with different fluxgate locations at that time. The mfr's recommendation of an optimum location doesn't mean it won't work elsewhere.

Whatd'ya want, a straight course or cold beer? Enough of the latter and you won't notice the former.

[ArtJ]

Agreed!!! how could one determine the root cause of a sinusoidal course?

[ArtJ]

Neil

I just noticed that your home port is San Pedro. I spend close to 4 years
on a tin can homeported on the Destroyer Moleback in the mid 60's . Currently live in NH.

Maybe you could have bid on the Spruce Goose a while back!!
Just think 8 engines to work on!

Regards Art

[ArtJ]

I noticed in the West Marine catalog a caviat that if batteries are used
in pairs, they should be replaced at the same time to prevent a weak, older
battery dragging down a new battery to it's charge level

Regards

[sastanley]

Yes...if you build a bank, you should get them all at the same time, and all the same type.

[ArtJ]

Originally Posted by ndutton

Art,

Shawn's mention of my battery system was right on. I have 2 house banks of 2 batteries each and a single engine starting battery, all controlled by 2 manual battery switches. I've attached a drawing of the system. I haven't figured out how to create a pdf in landscape format so you'll have to rotate the pic to read it.

I've read on this site how many members love their automatic battery combiners but as I've said before, I'm really old school. The manual switches work for me, I think it's a repressed control issue.



I should clarify your comment slightly. I have no battery specifically dedicated to refrigeration but rather an increased general house capacity due to the refrigeration load.

Hi Neil

A question on your wiring diagram. I notice that you have a second A/B
switch for your shore power charger. I also notice that the charger itself
seems to have 2 banks that are selectable as well?

In my case, I am thinking of only having 2 banks of paralleled batteries
for 4 total. I was considering connecting my honda generator directly
to the common terminal on a single A/B switch .

Are there any issues with doing this? Would the boat's alternator and other accessories in the main panel be happy with this?

I was considering using a cigarette
lighter socket, via a breaker ,to both power the +12V refrigerator and( when removed)
using the same lighter socket to provide charging, via Honda generator,to the A/B selected battery bank.

This would be done so as to not connect the refrig/ freezer while subjected
to higher charging voltage of the generator.

One thing I can think of immediately would be that this proposed system
might not able to be used while running the engine - possible
conflict with the alternator and Honda generator?

Any comments would be appreciated.

Thanks

Art

[ArtJ]

Just realized that I should have a second A/B switch connected similar
to the existing A/B except that the common terminal only would go to a socket
for the Honda generator, In this way, the generator could be charging
one bank while the other is powering the Refrig. The only caviat would
be making sure that the generator is not connected to a bank at the
same time as the refrig, so as to not present harmful voltage to the
refrig.

[sastanley]

Art,
If I understand what I think you are proposing, I do not think there is any safe way to get the amps coming from a generator thru a 12v lighter socket into your 12v system...the socket was simply is not designed to handle that many amps.

I see 12v sockets for things like charging my handheld VHF, cell phone, & maybe powering my laptop (more details below), if the wiring and fuse behind the socket is up to the task, but regardless, I would not use a 12v lighter socket system for charging, except maybe a small solar panel for trickle charging. However, to me that also seems to have its drawbacks.

I have a 400 watt inverter. (I used this to power a 75 watt 110v power supply for the laptop until I bought a smaller DC/DC 12v to 17v power supply) This 400w inverter came with a 12v lighter plug, but I would never use it that way unless I rewired (beefier) the rest of the system to match the wires coming between the plug & inverter. In my case, I always clipped it directly to the battery posts, because I knew the 12v socket wires installed in the boat were not large enough.

I am curious - what type of amperage draw does a reefer have with a 12v cigarette lighter plug?

My $0.02...your mileage may vary..

[ArtJ]

Shawn the refrig (dometic 25) draws 10a peak. it comes with a cigarette lighter adapter. I have also bought a coleman thermoelectric cooler which
also draws 10a peak. I have not decided to use both together or not.
THE Honda eu1000 generator provides 10a dc unregulated for charging
batteries.

I will possibly stick with the second a/b switch for the generator, but
will consider a beefier plug for it along with a ckt breaker.

thanks

art

[ndutton]

Art,

My battery charger has 2 output circuits for 2 banks. Output 1 is connected to terminal 1 of the engine battery Off-1-Both-2 battery switch, the same terminal as the engine start battery is connected. When the battery charger is on, the engine start battery is charged regardless of battery switch position.

Charger output 2 is connected to the battery 2 terminal of the engine Off-1-Both-2 battery switch, the same terminal as the house bank battery switch common is connected, essentially connecting output 2 to the house bank switch common. Output 2 can then be directed to either house bank or both depending on the position of the house bank battery switch. Connected to engine battery switch terminal 2 is also the main DC distribution panel. The house bank in use for DC distribution is simultaneously charged by the battery charger.

The drawing should be helpful in digesting all this.