Inverter Duty Limits

[CaspersCruiser]

I bought an ePropulsion Spirit 1.0 Plus battery electric outboard for the dinghy on my 2012 R27. An AC power battery charger was supplied to charge the outboard’s 48V lithium battery. When away from a marina and AC shore power, to charge the battery will require using the Promariner 1500W modified sine wave inverter or the generator for AC power.

My plan is to charge the outboard battery using shore power as much as possible. When away from a marina, my next choice is to use the inverter while the engine is running and the boat is underway. The AC battery charger uses 320 watts of AC power during operation so it will not tax the inverter.

My questions are these: 1) Is there a duty limitation on inverter operation? The Promariner manual does not list one. Is there a limitation on how long the alternator should be loaded keeping the house batteries charged during inverter operation? 2) The Promariner is a modified sine wave inverter. Any idea if that has any effect on something like a battery charger? The Promariner manual says motors, pumps, and fans will use about 20% more power because of the modified modified sine wave and that appliances with digital clocks or timers may not operate correctly.

 

[knotflying]

An alternative is to buy one of those plug in 12V inverters large enough to carry the 110V charger load and use that. The Promariner will work fine, but is not as efficient since just having it on uses battery power. I would use this setup and charge while under way to top off my Torqeedo. Also, not bad to have one in case the inverter goes on the bum. I also used it to run my C-pap.

 

[BB marine]

Is there a limitation on how long the alternator should be loaded keeping the house batteries charged during inverter operation?

Ball park number for battery amperage needed using an inverter to power a 120V devise is 1 amp of DC input to power 10W of 120V AC output. 320W 120V AC would use 32amps DC to power the charger. Your battery bank for the house is a minimum of 200 AH with 100 AH usable and if you have bigger or more batteries this number would be greater. The Yanmar alternator I believe has a output of over 100 amps to Charge all batteries on board, Engine bank,Thruster bank and house. So if all batteries are rated the same and fully charged the alternator will still be working most of the time while the engine is running to maintain the demands of electrical devises running but rarely at full capacity. If you were to start cruising and turn the inverter on maybe the first hour or so the alternator would be operating at a higher output fully charging the battery banks, and maintaining the demands of the 12V devises that are on, refrigerator,chart plotter, radio, engine electronics and the electric outboard charger. You need to add up what DC amps are required to operate all components to help maintain the integrity of the alternator. If it is operating at max output for an extended period of time it will get hot. Excessive or extended heat can damage an alternator.

To answer your question. The alternator can operate all the time under a load while keeping the batteries charged. Using a little bit of power management will reduce the chanced of the alternator being fully loaded and over heating. I used my inverter 2000W frequently, sometimes all day while operating the engine. 650 hours and no alternator issues. I did find it to be operating at over 200 F when checked with an IR gun. This is acceptable but marginal to over heating it. Because of the poor ventilation in the compartment I added blower directly in front of the alternator to help it heat sink and lower its operating temperature. I know my charging demands were high but still not at the full operating capacity of the alternator.

Remember the alternator has about 100 amp output +/-. @ 2000 rpm engine speed. When you first plug in the charger and start charging electric motor battery the highest power demand will be present about 32 amps 12V DC. I assume the batteries are fast charging so as the batteries charge the power demand decreases. This will fluctuate the alternator output demands. When the batteries are charged fully the demand small. If all your batteries are in good condition and 80% + charged with normal 12VDC demands plus the inverter used to charge you electric motor battery. You will not be operating the alternator at full capacity load.

I don't know if using a modified sine wave inverter to power the charger is an issue or not. I have read that smart chargers do not tolerate modified sine wave power very well especially when used to charge NiMH or lithium chargers for power tools. I don't Know! If I was going to use the inverter I would call or email the charger manufacture and see what their thoughts are on this.

 

[Brian 27 OB]

https://www.epropulsion.com/product-pag ... r-12v-24v/

 

[CaspersCruiser]

Ball park number for battery amperage needed using an inverter to power a 120V devise is 1 amp of DC input to power 10W of 120V AC output. 320W 120V AC would use 32amps DC to power the charger……… The alternator can operate all the time under a load while keeping the batteries charged. Using a little bit of power management will reduce the chanced of the alternator being fully loaded and over heating….

Great info, Brian. When getting underway after being at anchor and using the house batteries, I will certainly have to let the alternator charge the house batteries a while before bringing the inverter on line to charge the outboard battery, if it’s needed. I don’t anticipate long dinghy trips and the ePropulsion battery has a pretty good run time if full throttle is not demanded. I may not need on-boat charging between marina stays where AC power will be available.

I have read that smart chargers do not tolerate modified sine wave power very well especially when used to charge NiMH or lithium chargers for power tools. I don't Know! If I was going to use the inverter I would call or email the charger manufacture and see what their thoughts are on this.

I will do that because I don’t want to ruin the AC charger. It may be tough to find a source who understands the issue.

 

[CaspersCruiser]

https://www.epropulsion.com/product-page/spirit-1-0-dc-charger-12v-24v/

I looked into that charger. According to the specs, it takes 19 hours to charge the battery from 20% to full charge. That will be my last resort for onboard charging.

 

[gswearin]

I have the same motor and even less knowledge of inverters! Would using the DC ports (cigarette lighter thingy’s) be a better choice?

 

[CaspersCruiser]

I have the same motor and even less knowledge of inverters! Would using the DC ports (cigarette lighter thingy’s) be a better choice?

The 12V DC charger is what takes so long. I will go that route only if it’s the only way to charge on board.

 

[Martin610]

As noted the alternator has a duty cycle, but so does the inverter itself. Actually, every electrical and electronic device has a duty cycle. The challenge is getting the manufacturer to tell you what it is. Can be hard to get in touch with someone associated with the product who actually knows.

The inverter has a duty cycle in the sense that as it runs it will generate heat. The ProMariner is an MSW that is less efficient than a GOOD pure sine wave. What can happen is that the output voltage can drift over time. You are talking about long charging times with the Spirit. If the Sprit charger has circuity to sense that, and the drift is too large, the Spirit charger will shut down to protect itself. The Spirit is a good unit so I suspect that to be a likely scenario.

You would have to speak with whoever owns Pro Mariner now and hope there are technical people there who can help describe the duty cycle in context to what you want to do. Spirit is new enough that their detailed AC charging specifications would still be available. In both cases the engineering may have been farmed out so it could take time to get an answer. Worth a shot though, but you have to be patient.

The ProMariner loses about 20% in the conversion of DC to AC. A PSW inverter is better but there is still loss. The 12 volt solution may be the best if you don't have a generator available.

Not criticizing the ProMariner, I have one on my boat and it's been working away for years now.

 

[CaspersCruiser]

Thanks. Good info.

I looked into pure sine wave inverters and Promariner makes one. If it has the same footprint as the existing Promariner modified sine wave inverter, I will likely replace it.

I sent a message to eProplusion and asked about powering their AC charger with a MSW inverter, but they haven’t replied.

This discussion may be moot because of my style of cruising. Marina stays likely will be often enough that I’ll keep the battery charged with shore power.