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Old 02-18-2014, 02:46 PM   #1
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Daily Power Requirements...

I will need to replace my 10 year old house and starter banks prior to the boating season this year. In an earlier post (Electrical Systems 101) I received a lot of good information and cautions from people and as per advice, I have read through Calder's book on the subject. Being a bit dense, I have read and re-read the battery and electrical systems several times and I think I have a much better feel for electrical systems and stuff I have done wrong!

My house bank consists of 10 Trojan 105's wired as a 12 volt system. The starter bank consists of 2 Trojan 105's, also wired as a 12 volt system. I am thinking of replacing the starter batteries with two D31's. I haven't yet made up my mind if I stay with the T-105's or to a cheaper 6 volt deep cycle alternative.

The alternator is a Amptech S125E. I tested it yesterday and it is putting out at 14.5 volts when charging. I have a Balmar Max Charge MC612 multi-stage marine regulator which charges the house bank. The starter bank charging process is regulated with the Balmar Digital Duo Charge, which puts out a DC-DC charge, i.e. the starter bank is charged from the house bank when voltages on the house bank exceed 13 volts, and provides up to 30 amps charging. Below 13V, the Max Charge is in sleep mode.

As per Calder's recommendation, I have determined the power consumption of the following electrical loads and the estimated daily power requirements of each. I did this by going off grid and shutting off the charger and turning on the individual loads one by one and monitoring the amperage of these load from the Heart Interface Link 2000 monitor. I presume that the "Background" power draw includes loads from monitor itself as well as various background LEDs about the boat....

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The background draw is calculated first. This must subtracted off in order to calculate each load uniquely, otherwise these loads would be overestimated.

A couple of things jump right out. The fridge and freezer are real pigs on power. I still have to make these more efficient (venting the warm air from under the watch berth, where these units are situated). I also have something called a "Circumvent" which I have left on all the time. The PO installed this to replace the air in the bilge in order to control humidity on the boat and condensation in the bilge, but it seems that I should review whether this needs to be on all the time. It might be more important in the winter.

So I'm looking at the total requirement of 187 amp-hours and estimate that I need about a 1250 amp-hour bank for two days of use. This assumes the bank is cycled from 80% SOC to 50% SOC. The current bank is 1,125 amp-hours. If I stay with the current size of bank, it would be prudent to fire up the generator after 36 hour or so.

Note that I have not yet estimated the consumption of the Webasto Hydronic system. This would be additive to requirements in cold weather. Also I need to follow up on how the Thruster bank is charged. The Thruster unit is a Wesmar 24VDC with a Victron Centaur 12-40 charger. The thruster batteries are AGM. I am not sure how charging of these is regulated when the alternator is charging the other banks.

Comments?

Jim
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Old 02-18-2014, 03:31 PM   #2
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Jim: Is your daily consumption calculated or via a SOC meter?

How about living at the dock for a week or so un plugged? That will tell what your 24 hour true usage is and also how long you need to run the generator. I always seem to underestimate my power usage on paper.

Most people would be real happy to have the pig of refrigeration/freezer you have that draws ~81 amps/24hours.
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Old 02-18-2014, 03:47 PM   #3
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Hi Larry: Calculated. The link monitor shows the real-time amps drawn. The first column shows the Amps indicated on the link monitor. This value includes the background draw that remains when all known loads are off. So in the case of the engine room blower, daily power requirement Pd,

Pd = (9.1-0.7 amps)*0.5 hour = 4.2 amp-hours

This is the best I have been able to calculate for now. But I`m pretty sure it is important to deduct the background amps from all the other draws and calculate it separately for the 24 hour period, otherwise you will significantly over-estimate the draws of all the other loads.

You are correct that the loads unattended would be important. Based on these figures, I estimate 131 amp-hours. However, typically power-offs occur in the winter where I live, and the fridge and freezer are turned "up" to a higher temperature and the cabin space would be colder. As a result, these would cycle on-and-off less frequently. I would probably have the circumvent on during those times.

Jim

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Old 02-18-2014, 04:08 PM   #4
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I see no complaints from you about the existing battery system that has provided you very long battery life. When I was faced with battery change out time, I asked myself if anything had changed or wasn't working right. No was the answer, so in went a set of 8 new Trojans 105s for the house bank. I see nothing in your list that would spell trouble for 10 new of the same.

BTW, do you an inverter/charger or just inverter?
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Old 02-18-2014, 04:17 PM   #5
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The unit is a Freedom Marine 20 Inverter/Charger (100 amp charger and 2,000 watt inverter).

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Old 02-18-2014, 04:24 PM   #6
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Some comments:

Two T105s as a starting battery isn't a good choice. They will work but if you have to crank more than 10 seconds then a real starting battery will work better. A single Grp 31 will probably work fine.

I think that you probably overestimate the number of hours running some things and maybe underestimate others, like the fridge and freezer. But if you have two separate, air cooled condenser systems, I can see 187 amphours a day.

You Webasto system will use a lot of power, but in cold OATs then your fridge and freezer use should be less.

Figuring your battery useage from 80 to 50% only makes sense long term on the hook and even then I would figure that you will start at 85%. If you leave from a marina with shore power then you should be figuring discharging from 100 to 50% before recharging.

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Old 02-18-2014, 04:40 PM   #7
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Thanks David. The fridge and freezer are separate side-by-side units. They were on very frequently last summer during the warmer days. A springtime project will be to turn the existing muffin fans around to pipe out the hot air from the enclosed space under the watch berth seat where these units are located. Currently the muffin fans only blow the air around in there. I also hope to re-insulate the doors of these units. I've been on the phone with Novacool and they agree with this approach.

I agree with the group 31's as a starter bank. I'm leaning that way and apparently they will fit in the existing batter box.

Currently my alternator only has one belt. Several people have pointed out this should be a double pulley/belt set-up. Also on the springtime to-do list.

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Old 02-18-2014, 07:25 PM   #8
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Jim, that looks like a great summary of your power use, but you might be underestimating the refrigerator/freezer loads a bit. The start-up power is significantly higher than the running power. The more the units cycle on and off, the greater its effect on the total. Same with macerators, water pumps and other large motor devices.

I have the SOC meter, but it's like a photo of what's happening now or requires that I keep the other power devices off while monitoring long-term. I bought an inexpensive ($20) Kill-a-Watt meter that allows me to monitor a single 110V appliance at a time for as long as I need. If you can plug the fridge in through the meter for 24 hrs then note the AH consumed, you might get a more accurate feel for the demands. If the weather warms, expect the fridge/freezer loads to increase.

BTW, I don't see an ice maker on your list. Is it broken? If you listen to sailboaters, you wouldn't think power boaters left the dock without an icemaker.
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Old 02-18-2014, 07:57 PM   #9
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I'm a little confused with the inverter line item. 1.4 amps for 4 hours? Do you power down the inverter every day? Is your inverter used for anything like a microwave or coffee pot? If so, I dont see those loads listed.
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Old 02-18-2014, 08:04 PM   #10
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Flywright: the Fridge and Freezer are entirely DC powers so I don't think the 110V Kill-a-Watt will work in this instance. A bit of a pain to wire something in on line.

Highwire: I generally only turn on the inverter when I need to use an AC appliance, such as the saloon lamps or the coffee mill. I have the saloon lamps listed together with the inverter, but not the coffee Mill. That only runs for a minute or two and I don't know what it draws. Everything else AC (Microwave, Vacuum, Washer/Dryer) is run with the Genny on.

I think I need one of those SOC meters. My monitor does not have an output for SOC.

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Old 02-18-2014, 09:22 PM   #11
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A store chain called Batteries+Bulbs carries all type LED lites plus great batteries. Their AGM 31 is worth looking at. Over 1000 CCA and carries a 4 year FULL replacement warrantee. Buy two and cost is $303 each. 2 31 Batts will crank 500 CID $00 HP with no problem.
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Old 02-19-2014, 06:32 AM   #12
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I generally only turn on the inverter when I need to use an AC appliance, such as the saloon lamps

Sounds like 12v LED for the saloon lamps will be high on the to do list.
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Old 02-19-2014, 09:06 AM   #13
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You've certainly gone to a lot of trouble to figure everything out, but I have a suggestion:

If your current system has served you for ten years, why not just replace it with the same number and types of batteries and go another ten years? If you want to upgrade and cost is not an issue, AGM batteries of the same size are an improvement and are maintenance free.

That said, anything you can do to reduce power needs can't hurt. LED lighting is the place to start.
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Old 02-19-2014, 09:30 AM   #14
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Al, do they make a kill-a-watt for DC applications. If not since my refrig is AC/DC can I use a kill-a-watt to measure watts when on shore power and convert the AC watts consumed to DC amps using the formula: A=WV.

It's my understanding that a SOC meter measures the SOC of a battery bank. Of what value ia a SOC meter if a battery in a bank is partially or totally dead?
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Old 02-19-2014, 08:22 PM   #15
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FF said...Sounds like 12v LED for the saloon lamps will be high on the to do list.

Yes. I've already approached this topic....
LED retrofit for a 120 volt 100 Watt halogen lamp?

...just not sure when I will get to it yet. We really like the brightness of the current halogen ones, but I still want to investigate how to change them over to bright LEDs.

WesK said...If your current system has served you for ten years, why not just replace it with the same number and types of batteries and go another ten years?
I think that's what I'm going to do. I've investigated options for T-105's and have found some for $148 cdn, with no core charge. I will get $10 back on the core charge. Probably couldn't do much better south of the border, with the exchange rate.

However, I'm still leaning towards using the Group 31 for the starter bank. I've lined up two (same source for the T-105's) for $130. These are for Semi trailer trucks.

If there is anyone on the forum from Vancouver BC (or anyone else for that matter) that has another suggestion, I'm all ears.

Jim
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Old 02-19-2014, 08:43 PM   #16
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Quote:
Originally Posted by JDCAVE View Post
Flywright: the Fridge and Freezer are entirely DC powers so I don't think the 110V Kill-a-Watt will work in this instance. A bit of a pain to wire something in on line.



Jim
I put an ammeter in line with the DC circuit so that I can see what the DC draw is. For our two Isotherm units this varies between 3 and 9 amps per hour.
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Old 02-19-2014, 08:55 PM   #17
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Quote:
Originally Posted by JDCAVE View Post

If there is anyone on the forum from Vancouver BC (or anyone else for that matter) that has another suggestion, I'm all ears.

Jim
Yes, to confirm prices you may want to call North Harbor Diesel in Anacortes. They will install too. Great guys
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Old 02-19-2014, 09:15 PM   #18
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Bay Pelican: I believe I did confirm the amperage draw on the system through the Link 2000 monitor. However this does not indicate the cumulative draw, only the instantaneous draw.

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Old 02-19-2014, 09:22 PM   #19
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Quote:
Originally Posted by timjet View Post
Al, do they make a kill-a-watt for DC applications. If not since my refrig is AC/DC can I use a kill-a-watt to measure watts when on shore power and convert the AC watts consumed to DC amps using the formula: A=WV.

It's my understanding that a SOC meter measures the SOC of a battery bank. Of what value ia a SOC meter if a battery in a bank is partially or totally dead?
Tim, I've never seen a DC Kill-a-watt meter, but my Xantrex LinkPro SOC meter pretty much does that. The thing with the SOC is that it looks at the entire system and tallies anything that is on and drawing power or charging the battery. It's tough to look at one item over a day to see what it consumes unless you leave only that one item operating and nothing else.

Take a look at the SOC page. It provides a lot of info like:

% of battery charge
AH consumed (corrected for intermediate charging)
current amp draw on battery bank
current house voltage
current start voltage
hours remaining until depleted (based upon current charge and demand). It's like the miles-to-empty in your car. If your fuel consumption rises, your miles to empty decreases, and vice versa.

If a single battery in your bank dies, you'll see a noticeable drop in battery bank voltage which does not correspond with the AH consumed or remaining readings. After a bit of use, you get used to what your 'normal readings' are. Deviations would probably jump out at you if you're paying attention.
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Old 02-19-2014, 10:25 PM   #20
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http://www.xantrex.com/documents/Dis...-1(Vendor).pdf

According to the manual the cumulative amp hr draw should be presented. I thought I remembered the Link 2000 was capable of that other wise a large part of its attraction would be gone. It was a replacement of the lInk 10.

Maybe something is not setup correctly with yours.
Of course I could be wrong.
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