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Old 02-25-2014, 05:49 AM   #1
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Boat is seriously under-charged

We are about to do more on the hook cruising and I need to upgrade my charging capacity. I currently have
  • (5) 105 AH AGM house batteries connected in parallel to form the house bank
  • (1) 105 AH AGM start battery that is the start bank
  • (2) 100 amp alternators, one on each engine
  • (1) Battery switch that isolates or combines the house and start banks.
  • (1) 30 amp Charles 3 bank battery charger
  • (1) Westerbeke 7.6 KW generator. AC power is divided into (2) 30 amp circuits. One circuit power 2 air conditioning units, the other circuit powers all other AC powered items.
I've estimated my daily power usage while anchored at 300 amps. My older Norcold refrig is the primary power user. It still works fine and I won't replace it until it dies.



Some considerations:
  • I don't want to use the engine alternators as a primary way to charge the batteries
  • My current 30 amp charger would require I run the genny 10 hrs a day to replace the 300 amps used. Actually much longer when you consider the charger goes to a float charger at 80% charge. 10 hrs of run time per day is not reasonable.
So this is my plan:
Add a new battery charger. In my notes I came across the following formula to determine the required amp out put of a battery charger; 25% of the total amp hours of the largest battery bank. In my case; (5) 105 AH batteries = 525 amps. 525 * 25% = 130 amps.

So if I can find a 130 amp battery charger I will connect it to my house bank and leave my current 30 amp charger connected to the engine start bank and genny start battery.

This would require a genny run time of 3 hours per day to replace the 300 amps used each day. I would probably run an hour and a half twice a day.


Please comment on my plans.


Questions:
Do I need an ACR? I am pretty good about selecting the Battery switch to the house bank when we anchor. This of course keeps the engine start bank isolated and unused. After engine start I reselect Both on the battery switch which then allows the engine alternators to charge both the engine start bank and house bank.



Battery monitor/SOC meter. Is this necessary?



I don't need an inverter, so where can I get a 130 amp or something close battery charger. One bank is sufficient and does the battery charger need to have a selection to charge AGM batteries?
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Old 02-25-2014, 06:13 AM   #2
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I think you're in the ball park. First, you mixed up Amps and Amp-Hours, but I know what you meant. If you're using 300AH a day, and your house bank is 525AH, and you really shouldn't let it get below 50%, then you'll want to recharge by the time you've used about 263 AH. Or, as you say, twice a day. If you have an electric stove and water heater, do this while cooking breakfast and dinner, and heat your water at the same time. You'll need that extra margin because you won't charge back up to 100% in just an hour or two. As you point out, that last bit of the charging takes the longest.

There are probably a hundred opinions on ways to solve this, but I think a 100A charger (or a little bigger if you want) will get you where YOU want to be.
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Old 02-25-2014, 07:45 AM   #3
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Most batt chargers do not hold their rating , charge ability with small, under 10KW noisemakers.

So you may be running a very long time.at 70A not 130A.

I would install a big truck alt (135-150A) on the noisemaker , two if there is room and the units assembler will allow 3-5 hp taken off the front.

The AGM can absorb a good deal better than wet batts , so a smart V reg with a temp control would work best.

In the long run it will be far cheaper to toss the Norcold antique and cut your power draw in half.

As always the FIRST item installed should be a SOC meter to actually allow you to understand and keep track whats happening.

If you will spend weeks or months on the hook , plan on and size the batts to cycle between 50% and 85% , to reduce noisemaker ON time.
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Old 02-25-2014, 07:52 AM   #4
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I would install a big truck alt (135-150A) on the noisemaker , two if there is room and the units assembler will allow 3-5 hp taken off the front.
I've given that some thought but came to the conclusion after reading several posts on TF that a higher amp alternator on the genny would require expensive retooling, ie two belt drives and associated pulleys and I'm not sure I've got the room for such a modification. Besides would my 7.6 KV genny be able to handle air conditioning too?

I probably should contact Westerbeke and find out.

Anybody know?
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Old 02-25-2014, 08:27 AM   #5
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IOTA makes efficient but inexpensive chargers. Two 75 amp units in parallel with a common 3 step regulator would be your best bet. AGMs can charge at 50% of AH capacity.

The value of an ACR or equivalent depends on how good you are at remembering to turn the 1,2,all switch to protect the start battery.

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Old 02-25-2014, 08:34 AM   #6
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Quote:
Originally Posted by timjet View Post
We are about to do more on the hook cruising and I need to upgrade my charging capacity. I currently have
  • (5) 105 AH AGM house batteries connected in parallel to form the house bank

Sort of an OT/oblique comment... I think I've figured out that I can replace the 3x Group 31 AGMs in one of our banks with 4x 6v golf cart batteries... increasing available AH on that bank from 300-315 to approx. 450. I think I'll likely do that, whenever the 8-seasonold AGMs go south.

Perhaps you could eventually fit 6x GCs in the same space as your 5x G31... and that would increase your available AHs from 500-525 to approx. 675.

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Old 02-25-2014, 08:38 AM   #7
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Perhaps you could eventually fit 6x GCs in the same space as your 5x G31... and that would increase your available AHs from 500-525 to approx. 675.
-Chris
I assume the golf cart batteries are wet cell. My battery compartment is extremely difficult to get to. I wouldn't/can't check fluid levels on a consistent basis, so I'll stick with AGM's.

Thanks though, good thought.
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Old 02-25-2014, 08:41 AM   #8
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I assume the golf cart batteries are wet cell. My battery compartment is extremely difficult to get to. I wouldn't/can't check fluid levels on a consistent basis, so I'll stick with AGM's.

Thanks though, good thought.

Lifeline makes some AGM gold cart batteries.

I'm in sorta the same boat in that I can't reach all our batteries easily; I know what you mean about the conveniences of AGMs.

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Old 02-25-2014, 08:48 AM   #9
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Installing a big alt on the Westerbeke will be difficult to engineer.

Getting a more efficient fridge is key in the whole matter. Consider a separate cooler/fridge for drinks and keep food in the fridge. Opening the door everytime someone wants a drink drains the cold air and unit has to run another half hour to catch up.

I have resorted to using a high dollar cooler to store ice and using it to feed ice to a smaller drink cooler. Ice lasts about 4days and is cheaper to replenish than all the diesel it would take to cool drinks otherwise. System is still imperfect, and evolving.
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Old 02-25-2014, 10:34 AM   #10
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Solar panels? Looks like you may have a hardtop, the perfect place. I am about to install around 500 watts on our boat. The price has really dropped in the last few years, below $1.00 per watt. I am thinking 2 - 250w panels in series w/ a mppt controller. Around $1000 for parts. No moving parts.
Check emarine.com.

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Old 02-25-2014, 10:43 AM   #11
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Bear in mind that the rated output of a charger is its max, typically at 20C. It isn't smart to run these things at max output for hours and modern quality chargers often provide a de-rate feature. So getting 130A out may require a charger with a rating of more like 150-160A.

Not sure why you wouldn't want an inverter? Saves starting the genny for brief AC uses. If you are in the market for a new charger, why not consider a Victron or MasterVolt inverter/charger? Both make models that would give you your 130A.

I agree with your idea of keeping your current charger: it will help to properly load your genset as well as speeding up overall charging times/reducing genset run times.

The idea of putting really big alternators on a genset already properly sized for its AC end plus small (20A?) charging alternator has been discussed elsewhere: not a good idea.

SOC essential in my view. If you go Victron or MasterVolt, get one from them...there are models which give you remote control/monitoring of the charger (or charger/inverter) as well as SOC.

If you want to keep your Norcold but have concerns about its efficiency (and it will be your biggest pwr user when on the hook), consider putting a computer fan (small, brushless, quiet, negligible amp draw & literally only a few $) beside the Norcold's compressor to improve air circ/ventilation. You could get a 10-15% reduction in running amp draw from this alone.
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Old 02-25-2014, 10:45 AM   #12
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Quote:
Originally Posted by Cat Daddy View Post
Solar panels? Looks like you may have a hardtop, the perfect place. I am about to install around 500 watts on our boat. The price has really dropped in the last few years, below $1.00 per watt. I am thinking 2 - 250w panels in series w/ a mppt controller. Around $1000 for parts. No moving parts.
Check emarine.com.

Rafe
I wish we had a hard top. A 500 watt install would go a long way to matching that 300 amp-hrs daily consumption rate. It would also prevent deep cycling the battery bank.
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Old 02-25-2014, 11:16 AM   #13
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IOTA makes efficient but inexpensive chargers. Two 75 amp units in parallel with a common 3 step regulator would be your best bet. AGMs can charge at 50% of AH capacity.
David
This looks like a cost effective plan. About $600 + installation costs. However please explain the 3 step regulator, I thought they were built into the charger.

Another thing, this was posted by Aquabelle on 7/1/2012:
Problem with 2 independent chargers both connected to same battery/bank is that their voltage sensors will confuse each other: each will 'see' the charge voltage being applied by the other charger and not the real charge of the battery and so will step back their charge delivery, wrongly sensing a charged battery. You can gang together chargers of the same type often, but then you only connect one voltage sensing wire (and one battery temp wire) not two.

I would need further explanation on how to wire two chargers to avoid the sensing problem.

Quote:
Originally Posted by Ski in NC View Post
Installing a big alt on the Westerbeke will be difficult to engineer. Actually I've gone through and will no longer consider it.

Getting a more efficient fridge is key in the whole matter. Consider a separate cooler/fridge for drinks and keep food in the fridge. Opening the door everytime someone wants a drink drains the cold air and unit has to run another half hour to catch up.

When my current fridge craps out, I will replace it with a more efficient one. If I can get enough charge now with the current refrig, I'll be way ahead of the game when I replace it.

I have resorted to using a high dollar cooler to store ice and using it to feed ice to a smaller drink cooler. Ice lasts about 4days and is cheaper to replenish than all the diesel it would take to cool drinks otherwise. System is still imperfect, and evolving.
Yes something to think about.
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Old 02-25-2014, 11:43 AM   #14
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How about fold-down panels? Sailboats use 'em.
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Old 02-25-2014, 12:01 PM   #15
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How about fold-down panels? Sailboats use 'em.
Nah, for me it has to be pretty.
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Old 02-25-2014, 01:10 PM   #16
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timjet:

It has been a while since I looked at IOTA chargers, but they used to sell a simple charger, presumably with just a preset float voltage, that you could hook up to their IQ three step controller that would make it a full 3 step charger. One controller could handle several chargers and the chargers were designed to be paralleled.

Almost all are sold now with an integral 3 step controller.

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Old 02-25-2014, 01:27 PM   #17
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A 100 amp Charles will cost you $1400 plus cabling (I don't know your setup) plus the SOC unit.

One start battery for three engines doesn't work for me for redundancy so I would install 2 more, a standalone genset start plus another for the main engines. Don't forget cabling. Most marine stores will lend you a crimper, so make your own to fit.

Use your old Charles for the start banks to keep the floats correct. Start batteries are recharged in 5 minutes or so after being used so they are no problem, but they are the ones directly involved in safety issues, like anchor raising...

I would keep one alternator dedicated to charge the start bank and add a larger one for the house bank.

You need a new fridge system, so sell your old Notcold and get a more efficient method to keep things cool.

I agree that solar panels should be in your future.
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Old 02-26-2014, 07:10 AM   #18
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If you wish to drop your fridge power load to ZERO, simply properly install a propane fridge.

WE have a full sized Dometic , that uses a 20# bottle a month.
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Old 02-26-2014, 08:23 AM   #19
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A 100 amp Charles will cost you $1400 plus cabling (I don't know your setup) plus the SOC unit.

I agree that solar panels should be in your future.
A IOTA 75 amp charger costs $225. I can't see why the Charles are so expensive. IOTA has a paralleling controller they sell with their chargers, seems to fit my need and well below some competitors.

I don't see solar panels as being a viable solution. A couple of rainy days and you're searching for a plug or worse, drinking warm beer.
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Old 02-26-2014, 08:39 AM   #20
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If you wish to drop your fridge power load to ZERO, simply properly install a propane fridge.

WE have a full sized Dometic , that uses a 20# bottle a month.
That would solve the re-charging issue but create other problems. I really don't like propane plumbed throughout the boat and constantly pressurized. It's probably just me and probably why I choose diesel as a power plant.
Plus re-filling propane once a month at $18 and installing a propane locker with monitoring devices will soon cost more than going the electrical re-charge direction.
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