MICROWAVE VS TOASTER OVEN

[RHC]

Purchased cheap 600w microwave fr K-mart (galanz). Spent a wk end fitting/wiring pair of new 117AH 12v fr costco for house battery bank. hooked up 2kw vector inverter. checked out mw by heating mug half full w/ water 1.5 min at medium. water got hot, but oven made funny sounds, turn table stopped turning intermittently and seems like power shut off couple of times (light stayed on though).

Now I'm not sure if it's safe to continue using. wondering if safer to swap mw w/ toaster type oven. usage is mostly for warming pre-cooked food. typical boat use is day sailing. 2 nights max. disadvantage is cannot heat water for instant coffee. i guess it's easy enough to stash a small coffee maker somewhere.

Any advice? Anyone using happy w/ large toaster oven in the galley?

RHC

[Québec 1]

I use the micro oven when on shore power or with the generator. I use the origo stove any other time. Using micro wave or fridge when on battery power has only meant trouble for me so thats what I do. when i go down to the Bahamas and Cuba I will get some kind of solar power installed.
Q1

p.s. My motives are simple . No other source of flame in the boat besides the origo stove. The generator sits on the cockpit floor or on the stern seat.

[tangentair]

I suspect that the invertor is putting out a wave form that the microwave doesn't like, but with out an o'scope I couldn't be sure, can you take the microwave ashore or use shore power to confirm that it works properly? If it works OK on regular shore power, then I would suspect it was the invertor, you might look into a generator if you are committed to having one on board.
I like toast (and toasted or melted sandwiches) so a toaster oven would be my preference over a microwave but a microwave would use less power to accomplish the same thing if you were trying to heat up TV dinners. But like previously mentioned I would not use battery power to run either one. A little alcohol or propane stove would be much better for heating water and if the boat is rocking so much you can not use it, you should not be handling hot liquids either IMHO.

[RHC]

Thanks for inputs. Microwave works fine on land-AC. returned in today, replaced w/ oster 1.5kw convection toaster oven (nice looking ss construction). just tested bake function set at 225F. worked fine, inverter indicating under 1kw. ran for under 5min, then I hooked up charger to batteries. seemed like it was charging hard (2 amp setting) considering the light use. now i'm surfing looking for automatic over discharge protection for the batteries.

based on both your inputs, i realize now i need a small gen. will need to wait though since it's not cheap. i prefer not to deal w/ the risk w/ propane. i can handle peace of mind w/ alcohol, but oven still seems more practical for warming pre-cooked food (not frozen) as opposed to stove. I'm hoping the battery power will handle the light usage for day sailing, especially if i recharge right away. coffee will need to be in thermos.

bon a petit,
RHC

[RickJ]

Your two 117AH 12V batteries hold a theoretical 2.8 kWh of energy, so if the oven is actually taking about 1 kW it will flatten the batteries in under 3 hrs use. In fact at that discharge rate it will probably flatten them within 2 hours.

So yes, light, infrequent use from the battery between charges is doable, but it's very easy with something like that to over-use it and end up with dead batteries. My boat's PO left one of those cheap thermo-electric fridge/warmer things on board, I tried using it to keep drinks cool and it ran my house battery flat within a day. I took it out and left it at home.

Cheers, Rick

[RHC]

OK, this is sounding more encouraging. 2 hr use per outing is way more than what I intend to use. I charge the batteries 1 at a time. the 1st one (right after use) was charging hard and took a while to top off. the 2nd one, I charged the following day charged much more quickly. seems like the batteries recover a bit by itself over time (now that i think about it, kinda makes sense). I'm beginning to like the set up. Will let you know how it performs when i take it out.

good winds to all,
RHC

[RickJ]

As you're discharging the batteries in parallel it's probably best to charge them the same way. Total charge time should be about the same, and it means they are both getting the same treatment during charge and discharge cycles. This should help them stay balanced and prolong overall life.

Given that you see a partial recovery effect, which could well be due to the batteries getting hot during heavy discharge, the best plan would be to let both rest, then charge them in parallel. They will each be getting a slower charge, but that's no bad thing - slow, gentle charging never hurt a lead-acid battery. Too much fast charging OTOH can seriously shorten their life.

Cheers, Rick

[RHC]

rick,
that's interesting input. it's actually simpler for me to charge them in parallel. The reason I charge them separately is because of stuff i read about isolators & how 1 battery could drain the other w/o it. as you can see, i'm not a sparkie & haven't paid close attention to what i was reading.

anyway, charging them in parallel w/ charger set at 2 amps, i assume each battery will draw approx 1 amp each?? & if 1 battery gets topped off sooner, the current will simply be diverted to the other?? my schumacher charger claims to be "automatic", so i assume it will not overcharge.

thanks for inputs,
RHC

[Hardcrab]

RHC,
Your thinking is mostly correct, in that 1 amp will be dropped into each six cell battery.
But because the batteries are wired in parallel, they become "one" 12 cell battery.
(If this is to basic, I apologize, but a 12 volt battery is simply six individual 2 volt cells wired in series and stuffed into one box).

Assuming equally "good" batteries, all 12 cells will both come up to charge equally, with no differences in state of charge.
If one cell is (in fact) in better condition, as soon as it tries to gets ahead, the other cells will take that extra voltage gain.
(Very undemocratic and left leaning, politically speaking).

2 amps seems to me to be sorta small to be "refilling" the batteries after doing heavy duty on the toaster oven.
It will certainly work, but the time needed will extend out somewhat.
While charging, the battery takes current from the supply only what it "wants".
Heavy demand at first, then lighter demand as the state of charge (voltage level) comes up.
The whole charging deal is somewhat self-regulated, so it can't and won't overcharge unless the supply's voltage is to high.

[RHC]

my charger settings are 2, 12 & 75 amps. i generally use 2 amps, esp for single battery & in no hurry, mostly because of popular notion that lead acid batteries like slow trickle charge. sounds like w/ 2 batteries in parallel, there's no risk when running the charger at 12 amps (ie: 6amps per battery, or 1 amp per cell).

thanks all,
RHC

[dutchwinter]

the reason your microwave was acting funny was because of inductive load. most inverters cant handle it. but if you want, you can ebay your current inverter and get one that can deal with it. here's one http://powerbright.com/pw2300-12.html That's the one on my list, and I'm designing my electrical system to handle just about whatever I can throw at it.

[Wind Chime]

We have a railmount BBQ that does everything we need a toaster-oven to do. Makes good toast, heats leftovers, bakes potatoes, steams corn in the husk, bakes pizza and fish, etc.

As for coffee, we have a Coleman unit that works on the stove. No A/C or D/C.

Darry

[kmclemore]

We have a railmount BBQ that does everything we need a toaster-oven to do. Makes good toast, heats leftovers, bakes potatoes, steams corn in the husk, bakes pizza and fish, etc.

Pizza in the BBQ... ohh... good idea... never thought of that! And hey, our BBQ is round, too.... perfect!

[dutchwinter]

my wife keeps on asking about the BBQ, so my guess is that that is going to end up being our first cooking tool. I think i have a grilled food cookbook out in my garage somewhere. Im sure it will be enough for a year or 2 at least. you can throw a skillet on just about any BBQ as well, so there's some versatility in that. between a microwave and toaster oven though, I think I'd have to go with a convection microwave if i could find one small enough. i was thinking of building a proper removable kitchen block to replace the m galley. it wont be permanent untill i get it right, but you could install a microwave like its a built in oven. you could also install an induction cooktop too. http://www.compactappliance.com/IHP1500 ... lt,pd.html i don't know. just a thought. such energy hungry appliances would be best suited for those who are slipped alot or opt for large battery banks. i plan on being the latter. when i do build the galley, I'd be surprised if it ends up looking like i plan for it to look, but the design stage is half the fun in mods. I'd never install a toaster oven because they are just too inefficient.