Inverter/battery advice for a newbie
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tegdesign
Senior Member
Hi, It seems you know some stuff about batteries and inverters. I'm also a newbie, but have a different, but related question.
I have no generator, but a 2000w inverter. My Norcold refrigerator currently runs only on 12v dc power. It's something on my list to figure out. I've only had the boat for a few weeks.
My concern is this is going to be hard on my batteries even though I'm usually plugged into shore power. It seems that a constant drain on the batteries to fun the fridge and consequently inverter/charger constantly topping up the batteries seems bad to me. Am I right?
High Wire
Guru
No problem for an inverter/charger. Once the bank is charged, it will switch over to "float" charge which maintains the bank charged and supplies enough current to carry normal house loads as needed such as your refer.
Mule
Guru
You are right...you should not let your batteries drop below 60% of their rated capacity. With no generator and I assume no solar you are tied to the dock or spoiling your food. Inverters have their place, and a very limited place in most cases. The accepted penalty is 10% for invertred power. You have been hit with that before it gets to the appliance.
I have 10 golf cart batteries and I have to keep an eye on things. I have a 1.5 kW inverter. The only thing it is used for is TV, cable sat box. I could go on, but go get Nigel Calders book, do your math and pick a path.
When you know what you have, what you want to do, have a plan to get there then run it by us....new eyes never hurt a thing.
I have 10 golf cart batteries and I have to keep an eye on things. I have a 1.5 kW inverter. The only thing it is used for is TV, cable sat box. I could go on, but go get Nigel Calders book, do your math and pick a path.
When you know what you have, what you want to do, have a plan to get there then run it by us....new eyes never hurt a thing.
Edelweiss
Guru
Not really. . . as long as you are plugged into shore power, you aren't taxing your batteries. The battery charger is supplying whatever DC power your boats devices require. As long as no one disconnects your shore power you are golden. What shortens the life of your batteries are significant discharge cycles followed by a recharge cycle, no recharge cycle or poor maintenance. Most people will tell you to stay well above a 50% discharge level. Otherwise your battery life will be greatly reduced. Is your Norcold not AC/DC? It should run on your shorepower when at the dock.
Since you have no generator you have no choice. If you anchor out or otherwise have no shore power, then you begin a discharge cycle, until you restart your engines and begin a charging cycle. How far you discharge your batteries and how many cycles you put your battery system through, will have a lot to do with how often you replace your batteries. With no generator you're looking at probably 4 or 5 years if you're using more expensive deep cycle batteries and are careful and limit your discharge cycles.
Mine are off the shelf 4D lead acid batteries (bus batteries) which handles the engine starting and short term DC power needs such as my cabin lights and refrigeration, until the generator is started after anchoring. So any battery discharge is very small and immediately replenished. My four batteries have an average life of 8 - 10 years and cost about $200 each.
So either way, you pay for batteries or you pay for diesel, just pick your poison. . .
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FF
Guru
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>as long as you are plugged into shore power, you aren't taxing your batteries.<
True , but the dumb chargers may go to a high charge rate every time IF the voltage when the fridge switches on drops enough..
Doing this constantly does not harm the batt set , but it requires the battery water be checked far more often.
Operating batts with the plates showing does shorten their life.
True , but the dumb chargers may go to a high charge rate every time IF the voltage when the fridge switches on drops enough..
Doing this constantly does not harm the batt set , but it requires the battery water be checked far more often.
Operating batts with the plates showing does shorten their life.
Mule
Guru
=========================================
nailed it again FF
If you continue to operate without an alternative charging system it might be wise to go with AGM batteries insofar they are more forgiving and be sure o have a good, smart charger . Aside from no maintance, higher voltage float they also take a charge fast. Ya might look into the small, quite Honda gasoline generators.
Edelweiss
Guru
tegdesign
This is the manual for your Norcold. You are correct, this is probably your boats original fridge as it's model dates back to Sept 1985.
The schematic gives you an idea of how they convert and invert the AC/DC power to compressor voltage. Unfortunately, there are no indicated component values on the schematic. I'm sure a Norcold technician could trouble shoot this for you, if you're unable to correct the problem.
The rattling you hear may be loose sheet metal, but in my experience that can also be a sign of an impending compressor failure in the older slug style compressor. They get noisy when they fail. Norcold switched to a Danfoss compressor on the new model two door fridges, much quieter and more reliable. I would start putting money aside for a replacement, just in case!
Good luck
Larry B
This is the manual for your Norcold. You are correct, this is probably your boats original fridge as it's model dates back to Sept 1985.
The schematic gives you an idea of how they convert and invert the AC/DC power to compressor voltage. Unfortunately, there are no indicated component values on the schematic. I'm sure a Norcold technician could trouble shoot this for you, if you're unable to correct the problem.
The rattling you hear may be loose sheet metal, but in my experience that can also be a sign of an impending compressor failure in the older slug style compressor. They get noisy when they fail. Norcold switched to a Danfoss compressor on the new model two door fridges, much quieter and more reliable. I would start putting money aside for a replacement, just in case!
Good luck
Larry B
Billylll
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My understanding is at least from a 1984 Norcold frig you are actually internally inverting 12VDC to 23VAC. There is a relay that is no longer available to handle the conversion but a replacement can be found. It all depends on if you have an "A" or "B" type power supply. Either way the older models run off of 23VAC when using either voltage. Using AC it's a step down circuit when using 12VDC you use a inverting supply. Typically the relay's failure mode is a set of contacts welded together or get real noisy. I hope this helps and doesn't confuse.
Bill
Bill
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Billylll
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Unless you have the real estate for a large solar array and a smart MPPT charger to replenish power to the house bank 2 8D's will never cut it. Excess solar can be used to heat water with a special DC load element. We all know you can't recharge batteries from the inverter unless it's an inverter/ charger and you are running a generator or plugged into shore power. Forget about running a single 16,000BTU AC unit from an inverter if it will stand the surge the batteries won't last long enough to even mildly cool the boat.
Bill
Bill
BlueYonder
Senior Member
The real question is what are the total power requirements and how long will you operate with DC battery power running the fridge, lights, pumps, etc., and the inverter powering a freezer and misc ac loads, you may find that the amp hours available from 2 8D batteries may not be sufficient for more than an overnight (if even that).
Don't even consider connecting the water heater to the inverter (or the air conditioner). The power draw will be too high. You should be able to maintain hot water by running the main engine if you have a coolant loop installed.
Many websites that sell top quality inverters (Magnum, Victron, Mastervolt, Outback) have information on how to determine your power requirements in order to properly size your battery bank and inverter.
As the other posters have recommended, fixing the generator may be a better solution. Adding a quality inverter, battery cabling, additional batteries, AC wiring, adds up in cost rapidly. Adding one of the new quiet Honda generators is also an option. I would be paranoid about CO poisoning and be careful about where it is mounted. It makes me cringe when I see sailboats anchored near me with one of those generators mounted on the cabin top and running.
Good luck, I'm curious as to which way you decide to proceed.
Don't even consider connecting the water heater to the inverter (or the air conditioner). The power draw will be too high. You should be able to maintain hot water by running the main engine if you have a coolant loop installed.
Many websites that sell top quality inverters (Magnum, Victron, Mastervolt, Outback) have information on how to determine your power requirements in order to properly size your battery bank and inverter.
As the other posters have recommended, fixing the generator may be a better solution. Adding a quality inverter, battery cabling, additional batteries, AC wiring, adds up in cost rapidly. Adding one of the new quiet Honda generators is also an option. I would be paranoid about CO poisoning and be careful about where it is mounted. It makes me cringe when I see sailboats anchored near me with one of those generators mounted on the cabin top and running.
Good luck, I'm curious as to which way you decide to proceed.
