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Maximum watts inverter in 12V outlet
My wife and I have Lectric ebikes, and we want to charge the bikes while boondocking.  With out batteries being 48V & 9.6A, we think we need an inverter that is at least 500W.  Can we safely plug a 500W inverter into a 12V outlet without causing a fuse to blow or starting a fire?

Thank you,
Eric

Re: Maximum watts inverter in 12V outlet
Reply #1
My wife and I have Lectric ebikes, and we want to charge the bikes while boondocking.  With out batteries being 48V & 9.6A, we think we need an inverter that is at least 500W.  Can we safely plug a 500W inverter into a 12V outlet without causing a fuse to blow or starting a fire?

Thank you,
Eric

I am pretty sure that is way too much load for a 12v socket. Does your generator work? You may want to purchase a small generator to bring along if not
Joe B.
2008 26ft  grey/white Rear Bath
Family of 5 hitting the open road as much as we can.

Re: Maximum watts inverter in 12V outlet
Reply #2
Yes, our generator works, but we only need it for about 15 minutes per day while boondocking.  To charge the ebike batteries, it takes about 5 hours (for each ebike).

Re: Maximum watts inverter in 12V outlet
Reply #3
A 500-watt inverter can pull over 40-amps, way too much for a 12-volt outlet's 10-amp capability.
It will need a fused, hardwired connection to the battery.

What is the wattage rating of the chargers? It should be listed on the device.
Will you charge one or both batteries at the same time?

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze

Re: Maximum watts inverter in 12V outlet
Reply #4
Hmm...Maybe I don't need as big of an inverter as I thought.  Here's the sticker on the ebike charger.
I already tried charging using a 120W charger, but it didn't work.
Any further thoughts on how I can most easily use this charger?
We'd like to charge both bikes simultaneously, but if we can't, we'll do one at a time.

Re: Maximum watts inverter in 12V outlet
Reply #5
With out batteries being 48V & 9.6A, we think we need an inverter that is at least 500W

Yes, our generator works, but we only need it for about 15 minutes per day while boondocking.  To charge the ebike batteries, it takes about 5 hours (for each ebike).

Your battery figures indicate a storage capacity of about 461 Watt-hrs. Over 5 hrs, that is about 93 W-hrs each hour, a rate of about 8 Amps at 12V. A good 150W inverter should handle this from a cigarette lighter plug, doing only one battery at a time. For 2 batteries, this is over 920 W-hrs, or almost 80 Ahr of charge from your 12V coach batteries, so you will have to have solar or generator to replace that.

Steve
2004 FL
2013 Honda Fit

Re: Maximum watts inverter in 12V outlet
Reply #6
The sticker you showed says the charger draws about two amps at 100-240 VAC. Assuming 120 V, that's 240 watts. (That's for charging one battery at a time.) So you'll need an inverter with at least that much capacity--300 watts should suffice, and it will need to be hardwired to the house batteries, with an appropriate fuse at the battery end.

Steve is right in pointing out that taking 80 amp-hours out of your house batteries is a hefty chunk of power, since the standard pair of 6V batteries holds 225 amp-hours, and the rule of thumb is that it's wise not to use more than half of that (110 Ah) if you want those batteries to last. If you don't already have several hundred watts of solar panels, you may want to consider a major upgrade on the roof, unless you want to run your generator for hours each time you need to replace the power you took out of your batteries to charge up the bikes.

Understand, you wouldn't have to run it all the time you were charging the bikes; just long enough to replace the power that operation took. So if you go that route, the question is: how long does it take your converter (which is the limiting factor in charging your house batteries from the generator) to put 80 amp-hours into the house batteries? If you have one of the older converters that can only put out 30 amps or so, it may be worth considering a replacement--one of the Progressive Dynamics or similar converters that can put out 60+ amps. That could shorten your generator run time quite a bit.

If it were me, though, I'd cover the roof with solar panels (assuming you haven't already)--at least 400 watts, 600 if you can fit them.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"

Re: Maximum watts inverter in 12V outlet
Reply #7

Thanks Everyone.  FYI:  My coach batteries are two LifeLine 6V batteries with 220 AH each, and I have 200W of solar panels installed by Lazy Daze during manufacture.
With all of the information generously provided, here's what I'm looking to do:  Hardwire a 600W inverter (so I can use two AC outlets on the inverter to charge both ebike batteries simultaneously.  I would like to install the inverter behind the driver seat in my 2007 MB; however, it appears that the provided wires that run from the batteries to the inverter are only 2 feet.  I'm guessing that I'll need to replace these wires with longer ones that are lower guage (thicker) wires, but how thick???  This is the inverter I'm considering (unless someone provides another recommendation):  Amazon.com: VOLTWORKS 600 Watts Pure Sine Wave Power Inverter 600w DC 12V to...

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Re: Maximum watts inverter in 12V outlet
Reply #8
A 600-watt inverter can draw in excess of 50-amps. I would recommend either 6 or 8-gauge wiring, along with a 60-amp inline fuse. Wiring size is determined by the potential amperage draw and the length of the round trip wiring run.
http://4.bp.blogspot.com/-_VRM_ZGUKdc/ViOeH4m70tI/AAAAAAABdd8/tp6hj68cVTg/s1600/DC%2Bwire%2Bselection%2Bchart.jpgies have more range than we do

Our experience with e-bike is that they do not need to be charged often, and our batteries have more range than we do. This might mean you do not need to charge both at the same time, allowing a smaller inverter to be used.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze

Re: Maximum watts inverter in 12V outlet
Reply #9

Hi Eric.  I used a Novopal TSW inverter 2 kw(4kw surge). I liked it a lot, so I'll recommend a 1kw (2kw surge) one. A bit more expensive. The one you picked looks OK but I have no experience with Voltworks.
   Welding cable is more flexible and easier to work with. The EPDM insulation is tougher than vinyl.  You want to make sure it is real solid copper strands, not CCA!  Copper clad aluminum wiring.  Windy Nation says it is made in the USA.  4 Gauge 4 AWG 5 Feet Red + 5 Feet Black (10 Feet Total) Welding Battery Pure.... If you are near the battery box I'd recommend #4 gauge.  I used #2 gauge for everything. #4 should be OK for your needs.
   These terminals are tinned, and have a slight funnel at the end so all of the fine strands go in easily. I found that my #2 welding cable fit in #4 terminals fine. You might test some #6 terminals to see if they fit that #4 flexible cable.  TKDMR 10pcs 4 AWG - 5/16" Tinned Copper Wire Lugs Ring Terminals, Marine...   The stud number 5/16" is to fit the posts on the inverter, your over current protection and battery terminals.
    Use a good crimper. I used this one.   HKS Battery Cable Crimping Tool for AWG 10-1 Copper Ring Terminals, Heavy...   Borrow one if you can, for as few crimps as you need. Avoid the hammer one. Harder than it looks. Not very good crimps.
    Over current protection:  Amazon.com: 60 Amp 12V-48V DC Inline Waterproof Circuit Breaker Manual Reset...  No exposed metal conducting parts.  Set/reset, so you can hit a button to turn it off or back on. No ring terminals. Up to #4, spacer rings for smaller wire.   RonB

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RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB

Re: Maximum watts inverter in 12V outlet
Reply #10
Eric to give you our experience using a smaller inverter…

We use starlink which uses anywhere from 4-8+ amps 12v (more at startup) including the amps used by our 300w inverter.  
Specs say it pulls up to 50w on 120v.
 Many people use a 300w inverter plugged into a 12v outlet for starlink.

Many devices that run on 12v have a shut off low voltage level - and the inverters seem to have this also.

If you have a load on lead acid batteries  it pulls the voltage down.  Distance from the battery pulls voltage down more.  Other things using electricity on the same circuit pull the voltage down.  If it gets too low the device turns itself off.

Our LD dc12 circuits are 20 amp, Larry said 15 amp, so check your fuses.

Our plug in inverter (standard one many starlink users use), would not work on lead acid batteries at all (shortest wire length at that time was about 30’, nothing else on it). 

We switched to lithium because we were ready for this change anyway.

On lithium, even with a drop on long wires, our starlink worked most of the time plugged into any of our 12v outlets, even ones closer to 50’ long with other things running on the circuit (charging devices).    But occasionally the inverter would alarm and turn off even without other things working.  We put in an additional 12v outlet close to the battery (about 10’ long wire) that only has a few led lights on it and have had no problems since then.

I met someone at a caravan that bought a solar generator just to charge their e-bikes. 

Jane

Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.

Re: Maximum watts inverter in 12V outlet
Reply #11
Guessing at wire gauges is like guessing at tire pressures. Rather than guess, you can make certain by using a voltage drop calculator.

That one has a number of choices, and may look confusing at first, but here's how to use it. Start with these basic settings, which will be the same for most 12V RV wiring (other than in the engine compartment):

Voltage: 14V
System type: DC
Conductor type: copper conductor
Conductor temperature: 60C (for indoor wiring)
Conduit type: no conduit
Parallel runs: single set of conductors

Now just fill in the cable size, load current, and length of cable in feet (one way), and click the Calculate button to see the voltage drop in percent.

Bear in mind that what seems like a small percentage can be a substantial voltage drop. For example, a 3% voltage drop doesn't sound like much, but it will take you from 12 V to 11.6 V, which can be marginal for some appliances.

This is even more important if you're wiring up a battery charger or solar power system. Let's say your batteries need to be charged up to 14.3 V, and that's what your solar charge controller is putting out. But if you have a 3% voltage drop between the controller and your batteries, they will only see 13.9 V. At that rate, they may never be fully charged! So while a few percent of voltage drop may be tolerated by appliances, when it comes to charging batteries, it's best to keep voltage drop under 1%.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"

Re: Maximum watts inverter in 12V outlet
Reply #12
You should consider calling Voltworks and ask if they will honor the warranty if the battery cables are extended.  Also they may be able to confirm size of new extended cables. 

I like the portable solar charger idea.  It always for flexibility to find the sun for charging and doesn’t expose your energy operating system to potential issues. 

RonS
Ron and Linda
Ada Michigan

Re: Maximum watts inverter in 12V outlet
Reply #13
Lets see. The 12v outlets are fused at 10amps. That would mean 135 watts is the max the circuit could handle - no matter how many watts the inverter is rated for. And that ignores the drop as the distance to the batteries increase.

Direct connect to the batteries would be a way to go. Of course, your batteries may get drained to a level I would not be comfortable with.

E-bikes and dry camping don't seem to be all that feasible.
Don & Dorothy
Sold our LD in June of 2023

Our boring always non-PC travel blog
Traveling Dorothy

Re: Maximum watts inverter in 12V outlet
Reply #14

"I like the portable solar charger idea.  It always for flexibility to find the sun for charging..."

Yes, depending upon the wattage of portable solar panels you have attached to the charger/powerpack. But a less expensive way to accomplish the same thing is to simply add portable solar panels to your rig's built-in 12V system.

A 1,000 watt-hour powerpack with 200 watts of portable solar panels will run you around $1,500 to $2,000. On the other hand, you could buy a 200 watt "solar suitcase" for $300 to $400, or build your own for less than $200 by hinging two 100 watt panels together, as I did. I use a 25 foot 6 gauge cable to connect it to my rig, which gives me plenty of flexibility in placing the panels where they'll get sunshine.

I'm using that suitcase right now, as a matter of fact. I'm in a campground where my rig is shaded by large trees (for which I'm grateful), so the 400 watts of solar panels on my roof are only providing about 300 watt-hours a day--a small fraction of their capacity in full sun. But my 200 watt solar suitcase, even though it's a little bit shaded, is putting out 350 watt-hours a day, so adding it all up, I'm doing fine.

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Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"

Re: Maximum watts inverter in 12V outlet
Reply #15
"I like the portable solar charger idea.  It always for flexibility to find the sun for charging..."

Yes, depending upon the wattage of portable solar panels you have attached to the charger/powerpack. But a less expensive way to accomplish the same thing is to simply add portable solar panels to your rig's built-in 12V system.

A 1,000 watt-hour powerpack with 200 watts of portable solar panels will run you around $1,500 to $2,000. On the other hand, you could buy a 200 watt "solar suitcase" for $300 to $400, or build your own for less than $200 by hinging two 100 watt panels together, as I did. I use a 25 foot 6 gauge cable to connect it to my rig, which gives me plenty of flexibility in placing the panels where they'll get sunshine.

I'm using that suitcase right now, as a matter of fact. I'm in a campground where my rig is shaded by large trees (for which I'm grateful), so the 400 watts of solar panels on my roof are only providing about 300 watt-hours a day--a small fraction of their capacity in full sun. But my 200 watt solar suitcase, even though it's a little bit shaded, is putting out 350 watt-hours a day, so adding it all up, I'm doing fine.
Option A is most flexible standalone option as it can be placed and moved to sunny areas but is the expensive option.  Option B is less expensive and flexible but requires one to build it. Once again great suggestions and options that allow the owner to choice what is best for them. With either the inverter still must be installed to battery. 

RonS
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Ron and Linda
Ada Michigan

Re: Maximum watts inverter in 12V outlet
Reply #16
Guessing at wire gauges is like guessing at tire pressures. Rather than guess, you can make certain by using a voltage drop calculator.

That one has a number of choices, and may look confusing at first, but here's how to us
This is even more important if you're wiring up a battery charger or solar power system. Let's say your batteries need to be bulk charged at 14.3 V, and that's what your solar charge controller is putting out. But if you have a 3% voltage drop between the controller and your batteries, they will only see 13.9 V. At that rate, they may never be fully charged! So while a few percent of voltage drop may be tolerated by appliances, when it comes to charging batteries, it's best to keep voltage drop under 1%.

The voltage drop calculator is easy to use and gives an exact number, I like it.

Voltage drop is tough for many to understand and why knowing the size and length of the wire runs is so important when setting up charging systems and adding high-power usage devices such as large inverters. Keeping the voltage drop low is a prime design concern, thanks for the explanation.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze

 
Re: Maximum watts inverter in 12V outlet
Reply #17

"Option B is twice as heavy as option A at over 70 lbs (trying moving that several times an day)and still needs the inverter installed to battery."

If by "option B" you mean a solar suitcase, I'm not sure where you got that weight. My homemade solar suitcase used two of these $75 100 watt panels (plus two small hinges and two drawer handles). The panels weigh 14.67 pounds apiece and the hardware weighs only a few ounces, so that's 30 pounds total. They're not hard to move around. A typical 200 watt commercial solar suitcase that includes its own solar controller weighs 36 pounds, but if you go for lightweight plastic panels (not as durable), a pair of 100 watt Jackery SolarSaga panels would weigh 11 pounds.

"... and still needs the inverter installed to battery."

Yes, this discussion started with a question about using an inverter to power e-bike chargers. That's going to be the case regardless of how Eric replenishes the power taken from his house batteries.

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Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"

Re: Maximum watts inverter in 12V outlet
Reply #18
"Option B is twice as heavy as option A at over 70 lbs (trying moving that several times an day)and still needs the inverter installed to battery."

If by "option B" you mean a solar suitcase, I'm not sure where you got that weight. My homemade solar suitcase used two of these $75 100 watt panels (plus two small hinges and two drawer handles). The panels weigh 14.67 pounds apiece and the hardware weighs only a few ounces, so that's 30 pounds total. They're not hard to move around. A typical 200 watt commercial solar suitcase that includes its own solar controller weighs 36 pounds, but if you go for lightweight plastic panels (not as durable), a pair of 100 watt Jackery SolarSaga panels would weigh 11 pounds.

"... and still needs the inverter installed to battery."

Yes, this discussion started with a question about using an inverter to power e-bike chargers. That's going to be the case regardless of how Eric replenishes the power taken from his house batteries.

My bad I was wrong with the weight.  I edited my entry.  Thanks for giving your options.  They give clear choices. 

RonS
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Ron and Linda
Ada Michigan

Re: Maximum watts inverter in 12V outlet
Reply #19
Let's say your batteries need to be bulk charged at 14.3 V, and that's what your solar charge controller is putting out. But if you have a 3% voltage drop between the controller and your batteries, they will only see 13.9 V. At that rate, they may never be fully charged!
It's not quite so grim: The batteries will "bulk charge" up to 13.9 volts, then taper charge all the way up to 14.3 volts (at 14.3 volts, the charging current has dropped to zero). It takes longer, but if you are using lead acid batteries, the time difference might be unnoticeable, as lead acid batteries begin taper charging (all by themselves - it's the way they operate) more slowly above 13.9 volts anyway.
2005 Jayco 24SS

Re: Maximum watts inverter in 12V outlet
Reply #20
"The batteries will 'bulk charge' up to 13.9 volts, then taper charge all the way up to 14.3 volts"

But in the example I gave (3% voltage drop in the wiring, resulting in 13.9 V at the batteries), the batteries will never see 14.3 V--so they will never get a full charge.

"It takes longer, but if you are using lead acid batteries, the time difference might be unnoticeable"

It's not a question of time difference; it's whether the batteries can get the voltage they need to be fully charged. In the example I gave, the solar charging controller thinks it's doing its job by putting out 14.3 V, but the batteries never see that voltage, so they cannot reach full charge.

Bottom line: if there's significant voltage drop in the wires leading to your batteries, they will never fully charge. That's why it pays to use a voltage drop calculator to determine what size wire you need.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"

Re: Maximum watts inverter in 12V outlet
Reply #21

We have Juiced eBikes which have a 52V 19.2 AH Battery.  The battery charger that came with it is 52V - 2 amps.  We bought a 300W  12V to 110V pure sine wave inverter which works in our car or in our 98~MB.  We have a direct wired connection to our house batteries maybe 12-GA wire and we have not had any problems.  Typically we use the batteries to halfway and then they take overnight to charge.  There are higher amperage charging fast chargers for these bikes but then you need more inverter for them?


         Karen~Liam
           98 ~ MB
             NinA

Amazon.com: BESTEK 300Watt Pure Sine Wave Power Inverter Car Adapter DC 12V...

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1998 ~ MB  WanderDaze
previously a 1984 Winnebago itaska- The Road Warrior, before that several VW Buses and before that a 1965 Chrysler Convertible Newport or our 1969 Chrysler La Barron with an ice box and a couple sleeping bags

Re: Maximum watts inverter in 12V outlet
Reply #22
Bottom line: if there's significant voltage drop in the wires leading to your batteries, they will never fully charge. That's why it pays to use a voltage drop calculator to determine what size wire you need.
The key here is "if", but that requires the charging current to remain at the same amps "forever". But it won't, because the battery will continue to charge in "taper mode", and the more it charges, the lower it's charge rate. That lower amperage means the voltage drop on the wires is lower, so it's now charging (more slowly) at 14.0 volts. And so on: more charging, lower current, higher voltage, and after a few hours, it's fully charged, drawing very little current. No current, no voltage drop, and you have 14.3 volts on a fully charged battery. It's not an ideal situation, but it does allow for a full charge.
2005 Jayco 24SS

Re: Maximum watts inverter in 12V outlet
Reply #23
I'm using and recommend something like a Bluetti AC200 Max solar generator.  It has a 30 amp receptacle so you can plug-in like using shore power when boondocking and you can charge your e-bikes without disturbing/using your house or engine batteries.  With roof and or portable solar panels this gives you some redundancy that is important when RV'ing.  You can get them cheaper on Ebay vs the company website.
1998 31' IB