I have a 1985 H31 with the standard set of two deep cycle batteries. While sailing or at anchor, the admiral has often wanted to be able to use the microwave and/or toaster oven which are on board to cook up some crab legs or popcorn, or pizza rolls, or toast a bagel or whatever. The appliances are all 110 volt. I recently purchased a 1500 watt power inverter to be able to do this. I will install it after it is delivered. I am a bit worried about how badly this is going to drain the batteries. The usage we are talking about is pretty light. Maybe five minutes of Microwave use or 10 minutes of toaster oven use. Can I run the motor to offset the power drain while using the inverter for this purpose? Do you foresee any problems with the alternator while doing so? Am I worrying too much? I do not want to get caught away from port with a dead bank of batteries.
advise on power inverter use
- Thread starter pimerese
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that's a typical use
A 1000 w microwave operating for 5 minutes will use approx. 10 ampH @ 110VAC or approx. 100 ampH at 12VDC through the inverter - in 5 minutes, that equates to a around 10 amps from the batteries. Same usage could be expected from a blow dryer or toaster unless one uses either for substantially more than 5 minutes. No problem regardless of what you do with the alternator which likley if it's a stock piece, will only produce 35 amps per hr charge at a resonably high rpm. If you're still concerned, simply wire in a separate start battery which is uneffected by the house draw.
A 1000 w microwave operating for 5 minutes will use approx. 10 ampH @ 110VAC or approx. 100 ampH at 12VDC through the inverter - in 5 minutes, that equates to a around 10 amps from the batteries. Same usage could be expected from a blow dryer or toaster unless one uses either for substantially more than 5 minutes. No problem regardless of what you do with the alternator which likley if it's a stock piece, will only produce 35 amps per hr charge at a resonably high rpm. If you're still concerned, simply wire in a separate start battery which is uneffected by the house draw.
SImple answers
One of my favorite upgrades to my boat was adding in an inverter. Since we live on a mooring my microwave had never been used previously. First, I would set up a starting battery with a selector switch and only use the house battery for house purposes and the starting battery for starting purposes. All will be well and you will always be capable of starting you engine should you follow that simple rule. Aside from that brief periods of using the inverter is what it is for. You size your house battery bank to match your usage patterns (long topic, better explained in the archives) and run your engine, solar panels, wind generator to charge your bank. Running any of those charging sources while also running your inverter would be fine. Running them before or after is also fine. Just keep in mind that five minutes of engine running time does not equal five minutes of drain while you run your toaster oven. Again a long topic covered previously in the archives. Finally, 1500 watts may not be enough for a toaster oven or microwave. You should check your oven's specs (which you may have already done).
One of my favorite upgrades to my boat was adding in an inverter. Since we live on a mooring my microwave had never been used previously. First, I would set up a starting battery with a selector switch and only use the house battery for house purposes and the starting battery for starting purposes. All will be well and you will always be capable of starting you engine should you follow that simple rule. Aside from that brief periods of using the inverter is what it is for. You size your house battery bank to match your usage patterns (long topic, better explained in the archives) and run your engine, solar panels, wind generator to charge your bank. Running any of those charging sources while also running your inverter would be fine. Running them before or after is also fine. Just keep in mind that five minutes of engine running time does not equal five minutes of drain while you run your toaster oven. Again a long topic covered previously in the archives. Finally, 1500 watts may not be enough for a toaster oven or microwave. You should check your oven's specs (which you may have already done).
Take care with your installation....
Follow the instructions that come with the inverter carefully. Two particular items: 1. Install the inverter as close to your battery bank as possible, and use large wire - it's not the current draw as much as voltage drop that you're concerned with. 2. Make absolutely sure that the inverter CANNOT be on at the same time as shore power. That would be messy. In fact, you might consider not wiring the AC output into the boat's AC system at all. I've got mine separate, so I'm never depending on my memory. Installing a separate starter battery (or another non-dedicated bank) is a good idea. If you want to monitor your battery, but don't want to spend the money on a Link monitor, just get a plug for your utility outlet and splice leads to your multi-meter into it. See the link below for a correlation table between voltage and battery state. Cheers, Bob s/y X SAIL R 8
Follow the instructions that come with the inverter carefully. Two particular items: 1. Install the inverter as close to your battery bank as possible, and use large wire - it's not the current draw as much as voltage drop that you're concerned with. 2. Make absolutely sure that the inverter CANNOT be on at the same time as shore power. That would be messy. In fact, you might consider not wiring the AC output into the boat's AC system at all. I've got mine separate, so I'm never depending on my memory. Installing a separate starter battery (or another non-dedicated bank) is a good idea. If you want to monitor your battery, but don't want to spend the money on a Link monitor, just get a plug for your utility outlet and splice leads to your multi-meter into it. See the link below for a correlation table between voltage and battery state. Cheers, Bob s/y X SAIL R 8
and how much battery reserve do you have?
One of the questions is how much battery reserve to you have. These boats came equiped with two batteries (I think that they were Grp 27's) so that would only give you about 85 amps for housekeeping. You will want a lot more than that depending on what else you have running (refrigeration, stereo, lights etc). You may want to think about a larger battery bank to use with this inverter if she really wants to start burning the amps.
One of the questions is how much battery reserve to you have. These boats came equiped with two batteries (I think that they were Grp 27's) so that would only give you about 85 amps for housekeeping. You will want a lot more than that depending on what else you have running (refrigeration, stereo, lights etc). You may want to think about a larger battery bank to use with this inverter if she really wants to start burning the amps.
110 volt inverter wiring
The cheapest way to meet the regs for inverter wiring (110 volt side) is to install two sets of breakers, one for the shore and one for the inverter/generator. Then have a mechanical lockout on the breaker switches so you can't have both on at the same time. You need to have a breaker on both the hot an neutral lines on both systems, There are duel breakers for this or you can use two regular ones. The most expensive way is with an auto switching circuit box. I've had one and unless you can seal it with caulk, wrap it with plastic fill it with nitrogen and then put it in a little shrine where rust is prayed about continuously they only work for one season at best. My math on the batter draw is 1500 watts / 12 volts = 125 amps continuous as a miximum so size the cables accordingly Typical draws I've see from my inverter hairdryer 1500 Watt draws (GASP) 137 amps. 15 min use is 35 AH 1000 Watt (back panel number) microwave 80 amps 2000 watt toaster draws 170 amps (we don't use ours any more and toast with gas) Now if I could only get the admiral to use a gas hairdryer..... ;-)
The cheapest way to meet the regs for inverter wiring (110 volt side) is to install two sets of breakers, one for the shore and one for the inverter/generator. Then have a mechanical lockout on the breaker switches so you can't have both on at the same time. You need to have a breaker on both the hot an neutral lines on both systems, There are duel breakers for this or you can use two regular ones. The most expensive way is with an auto switching circuit box. I've had one and unless you can seal it with caulk, wrap it with plastic fill it with nitrogen and then put it in a little shrine where rust is prayed about continuously they only work for one season at best. My math on the batter draw is 1500 watts / 12 volts = 125 amps continuous as a miximum so size the cables accordingly Typical draws I've see from my inverter hairdryer 1500 Watt draws (GASP) 137 amps. 15 min use is 35 AH 1000 Watt (back panel number) microwave 80 amps 2000 watt toaster draws 170 amps (we don't use ours any more and toast with gas) Now if I could only get the admiral to use a gas hairdryer..... ;-)
Alternator may be undersized.
Your alternator is rated for continuous output so if you have a 30 amp alternator, it will put out 30 amps all day long.(As long as your battery accepts 30 amps that is!) The question you have to answer based on your inverter/battery usage is: Will your alternator be able to keep up with your usage? It's basically a Amp*Hour issue. If you draw 100 amps for 15 minutes, you could run your engine for about an hour to make up for that draw. Figure out your amp hour draw by multiplying (amps used)*(hours). Example = 1/4Hour*100Amps = 25 AmpHours. Then figure out how long your alternator will take to charge your batteries back up. As your battery voltage comes back up, your current output from the alternator will drop so, this is just an approximation. You'll probably need an extra 25 percent to get back up to full state of charge.
Your alternator is rated for continuous output so if you have a 30 amp alternator, it will put out 30 amps all day long.(As long as your battery accepts 30 amps that is!) The question you have to answer based on your inverter/battery usage is: Will your alternator be able to keep up with your usage? It's basically a Amp*Hour issue. If you draw 100 amps for 15 minutes, you could run your engine for about an hour to make up for that draw. Figure out your amp hour draw by multiplying (amps used)*(hours). Example = 1/4Hour*100Amps = 25 AmpHours. Then figure out how long your alternator will take to charge your batteries back up. As your battery voltage comes back up, your current output from the alternator will drop so, this is just an approximation. You'll probably need an extra 25 percent to get back up to full state of charge.
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