Induction/Frig/460Ahr ??

[Time2Go]

Hi Friends
Here's the scenario
460 Ahr bank (4 230 GC)
Frig, and the usual other bits found on a 44 footer
No electric winches or thruster
The boat has a 5kw generator, & an inverter/charger
2 Balmar alternators on the engine ( one for start batteries the other for the house)
We are thinking of ditching the propane system (needs rebuild)
and going with Induction cooking only

Interested in any comments, do's and dont's and opinions
on if a 460ahr bank is big enough??
Thanx all in advance
Cheers
Neil

[phorvati]

I have the same setup. I fire northern lights generator to cook or even just to make coffee. I'm mostly on the dock and plugged in with 50a service. If you are to live on the hook or cruise, you need a larger bank in order to use inverter and induction cooktop otherwise you are cycling 460ah too much daily.

[Adventuresail]

I have the same set up with a 450 ah Firefly battery bank with an induction stove and an electric convection oven. It works but there are some limitations. The voltage sag is significant when you are pulling almost 200 amps @12v. Enough that i can notice the cabin lights dim. We want to be able to use the galley without worrying about power usage too much so our solution is to use a separate 450ah battery bank to supply the galley.

[Adelie]

I’ve done quite a bit of analysis on this.

Needed bank size is going to depend on 2 things:
Total daily draw
Max instantaneous load.

Total draw includes all house uses.
To figure other house draws I assume:
50Ahr/d auto pilot varies some with specific unit, size of vessel and how well you balance the sails.
50Ahr/d per fridge or freezer. Varies depending on size, insulation thickness and unit efficiency. Let’s assume 1 unit.
The rest of the house loads you’ll need to figure out yourself, too much variability.
For purposes of argument let’s assume 50Ahr/d.
So total non-cooking draw is about 150Ahr/d.
Daily draw for cooking will vary depending on how much you cook and how much you eat out and how many efficiency measures you are willing to implement.
As a starting point you can estimate your electrical draw based on how much propane you are currently using to cook with. I have a table that uses propane tank size and average days to empty to estimate what you average daily electrical draw would be. I’ll post that table in a later post.
As a starting point if you cook most meals and eat out rarely you will draw about 125Ahr/d. This is based on the propane use by another mod who was cruising.
If you cook a fair bit but not most meals then we can assume 100Ahr/d.
So total daily house draws would be about 250Ahr/d.
I would be OK with a bank 2.5 times my average daily draw. Since my preferences are to rely on solar as much as possible I should be able to get thru 2 or a bit more days of low solar output before I get to 50% and needed to use a secondary source like a generator.
That means a bank of about 625Ahr. 750 would be better. If you are using a generator for all charging then you want to think about how low you are comfortable letting your batteries get.

Instantaneous load is easier. Most house loads are continuous over the whole day. So 150Ahr / 24hr = 6.25A.
Let’s assume 8A just in case the fridge kicks on at the same time the autopilot is dealing with heavy seas and at the same time you are cooking.

Cooking load is going to depend on how many burners/hobs you have and if you have a convection oven.
In the US plug-in appliances max out at 1800W, that’s what household wiring is designed to handle.
So If you get a 2 burner countertop plug-in unit and an 1800W convection oven that’s 3600W. Inverter efficiency varies, let’s assume 90% so 3960W, call it 4,000W even.
4000W @ 12v is about 333A plus 8A for other house loads is 341A instantaneous load.
How long will this load last. Let’s say you put a large pot of water on to boil, at the same time start a sauté pan for some veggies or whatever and start the convection oven to roast a chicken or whatever. That’s everything all at once.
The water will run with full draw until it boils. Let’s assume you put it on the big burner that pulls 1200W, it’s a bit pot of water so 30min or more.
On my gas stove at home I toss some oil in pan and turn it on full and in 2min I chop the heat to medium and add the items I’m cooking. Let’s say 2min then it goes to half power for the second induction burner even though induction tends to be faster than gas even. Half power on the second burner is 300W
A countertop convection oven being much smaller than a regular oven will heat up faster than a regular oven. So when you turn it on it goes full power heating the air in it, the walls of the oven and starts to heat the item being cooked. Once the walls of the oven come to terminal temp the air will catch up and the oven will drop to a lower load for heating. The power used will depend on how fast heat escapes thru the walls and how fast the item being cooked absorbs the heat and what the temp chosen is. Let’s assume power drops to half after 10min.
So for the first 2min you will be drawing 4,000W or 333A+8A=341A.
After 2min the pan goes to half power so
(1200 + 300 +1800) / 90% = 3,666W —> 306A + 8A = 314A.
At the 10min mark the oven goes to half power so:
(1200+300+900)/90%=2,666W —> 230A +8A=238A.
I would size the wiring for the highest instantaneous load all the way from the batteries thru the main fuse, main power switch to the inverter.
I would split off the other house loads at the main switch and run them thru a smaller fuse to the main panel. Size that appropriately.
The reason to size the wires to the inverter so large is because if they start to get warm their conductivity goes down and they get warmer still; any high resistance points in the circuit could get hot enough to start a fire.
For sizing the battery bank I would want to keep medium term draws 30min or so to C/3 or less. In this example that means 714Ahr bank size.
If you are never going to boil a large pot of water at the same time as the other two are going then it could be as low as C/2. Let’s say you put on 2qt of water for pasta or potatoes and run the other 2 as above. They’re going to be boiled and done in 20min max. So that’s a 476Ahr bank.
Will your voltage drop while running at full, yes. It will be more noticeable the smaller the bank, the older the batteries are, the more discharged they are and the cooler the batteries are.

One thing to keep in mind are Peukert effects, that is the higher the load the less total power the battery will actually deliver. A very high load spread around a bunch of batteries winds up being a moderate load. And the shorter the duration of the high load the less that effect will. If you stagger your loads so they are not as high at a given tim then your batteries will deliver more total power even though you have used the same amount of power for cooking or whatever.

I would go with a 650-750Ahr bank, all in one house and cooking. That should minimize voltage drop and the Peukert effects.

Regarding the inverter. You are going to be drawing 3600W at the appliances, that argues for a 4500W inverter. And induction doesn’t play well with modified sine waves so it needs to be a true sine wave model. Some induction models may work with a modified sine wave but be less efficient and may damage the burner, most won’t work at all. My research is not real clear about how bad modified sine is, I just wouldn’t even go there.

I have researched the efficiency of butane (50%) vs induction (75%) vs microwave (45%).
I am gearing up to compare the efficiency of a propane oven vs convection. Because of the high ventilation requirements for propane I’m assuming convection has at least as good an efficiency advantage over propane as induction burners has over butane. That research will be in 6-12mo and I’ll let folks on CF know in some thread or other.

I have tested a bread maker. I made a 2lb loaf using 330Whr @ 120v. That works out to about 30Ahr @12v after accounting for inverter efficiency.

If you are willing to use energy saving measures you can reduce daily draw.

Bring a pot of water to boiling with potatoes or pasta in it then remove from heat and cover with a pot cozy or Wonderbag. Cooking times may increase slightly but not excessively so.

Because the “burner” is not really that hot, you can add insulation to a pot while it is heating.

Preheat water using a solar cooker like a GoSun. I just got one, I’ll report back after testing.

For folks that want a 3 or 4 burner induction stove, you are on your own, I haven’t found any countertop models and all the permanent install models use 240v or use oversized wiring like for a household stove or dryer. In any case you wind up needing a stupid big inverter, a much bigger battery bank and really need to go with a 24v or 48v bank or cabling sizes get really outrageous.

For folks in Europe, with 240v mains standard appliance wattages will be significantly higher than US appliances and these calcs won’t work. My suggestion is to get wattage limited appliances or you will need a huge inverter, huge cabling and a bigger bank and maybe a high voltage bank.

If you aren’t getting an oven ever then a 450Ahr bank is probably fine. If you might get the oven or plan to the you can up grade cabling, main fuse, main switch and inverter in a staggered manner and increase bank size at the time you install the oven.

[Adelie]

I just found a 3 burner induction countertop model. It draws 3600W at 110v AC. $560. I don’t know how it would be powered without popping a breaker on normal household service.
True Induction TI-3B.

[RaymondR]

Microwave.

[Adelie]

Originally Posted by Adelie

I just found a 3 burner induction countertop model. It draws 3600W at 110v AC. $560. I don’t know how it would be powered without popping a breaker on normal household service.
True Induction TI-3B.

Unit has 2 plugs and per the instructions need to be plugged not just into different sockets but different circuits on different breakers.

Manual says 2 small burners can draw 1800W and the big burner on the 2nd cord can draw 1500W so 33ooW total.

https://www.trueinduction.com/pdf/Tr...ner_Manual.pdf

[carlosproa]

Have you check the YouTube channel of the TX couple who switch to induction?
I think their channel is Gone with the Winns? They bought a single burner for like $100 and I think they did a piece on choose installing etc

[noelex 77]

The biggest problem is producing the power you use, rather than the ability to store power (ie battery bank size).

With only a generator and alternator as power sources when at anchor you will be running your generator for reasonably long run times, which may or may not be a problem.

My advice would be try a cheap portable unit as a trial. If successful, this can be thrown away or kept as a back up.

[phorvati]

Generators are meant to run 24/7. They barely use any fuel. they are a PITA but until you add up solars to put back the AH you used during microwaving/cooking, and until you size the bank probably (1000AH or so), to me it seems induction cooking will have to rely on generator or shore power. Otherwise you are cycling your bank too deep every day.

The key is how deep (50% down, 75%down or 25%down) you want to cycle your house so you don't damage it before you put everything back in. And you better know where AHs stand and put everything back including loss factors etc, so you know you are cycling them properly. Otherwise you can drop serious $$$ on large house bank and screw up cycling and damage them/run them dry prematurely.

For me, because the boat came with 5k northern lights, I keep that baby ship-shape and work on adding solars before spending the money on large bank. My setup is even more dependent on AC power. I have large refrigeration (1.5HP 110V compressor) and a MarineAir air conditioner/heater.