[font size="3"]Here are results of three different methods of charging the camper batteries in the field: Direct connection to a vehicle battery, [/font][font size="3"]running the built in converter from 120V shore power, and[/font][font size="3"] running the built in converter from a vehicle mounted inverter.
1) Discharged two 6V GC2 batteries to 12.1V unloaded (approx. 50% SOC). Residual camper current 0.150 Amps.
2) Connected to Tacoma battery, engine running, with 20 Ft. #2AWG copper jumper cables. Measured 55+ Amps charging. Disconnected.
3) Tacoma gas consumption while idling was 0.5 GPH.
4) [/font][font size="3"]Plugged in CL shore power cord into 120V 30A house circuit. Measured 39 Amps charging. Disconnected.
[/font][font size="3"]5) [/font][font size="3"]Plugged in CL shore power cord into 400 Watt Tacoma inverter. Measured 20 Amps charging. [/font]
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This test was run on a 21RBS with two 6 volt GC2 batteries in series and a 2013 Tacoma, but results should be similar on other rigs. The best method is the jumper to the truck battery with heavy cables. The second best was the built in converter running on good shore power and should be similar to a good generator. The third best method was using the 400 watt converter built into the Tacoma ($30,000 generator). I didn't measure the AC voltage, but it was probably sagging due to being close to its limit. The 0.5 GPH gas consumption of the truck while idling makes it a good and quiet generator for CG use with no mess or extra gas cans. Just fill 'er up before you set up.
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Quote from: @charliem" timestamp="1419802672" source="/post/5679/thread[font size="3"]Here are results of three different methods of charging the camper batteries in the field: Direct connection to a vehicle battery, [/font][font size="3"]running the built in converter from 120V shore power, and[/font][font size="3"] running the built in converter from a vehicle mounted inverter.
1) Discharged two 6V GC2 batteries to 12.1V unloaded (approx. 50% SOC). Residual camper current 0.150 Amps.
2) Connected to Tacoma battery, engine running, with 20 Ft. #2AWG copper jumper cables. Measured 55+ Amps charging. Disconnected.
3) Tacoma gas consumption while idling was 0.5 GPH.
4) [/font][font size="3"]Plugged in CL shore power cord into 120V 30A house circuit. Measured 39 Amps charging. Disconnected.
[/font][font size="3"]5) [/font][font size="3"]Plugged in CL shore power cord into 400 Watt Tacoma inverter. Measured 20 Amps charging. [/font]
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This test was run on a 21RBS with two 6 volt GC2 batteries in series and a 2013 Tacoma, but results should be similar on other rigs. The best method is the jumper to the truck battery with heavy cables. The second best was the built in converter running on good shore power and should be similar to a good generator. The third best method was using the 400 watt converter built into the Tacoma ($30,000 generator). I didn't measure the AC voltage, but it was probably sagging due to being close to its limit. The 0.5 GPH gas consumption of the truck while idling makes it a good and quiet generator for CG use with no mess or extra gas cans. Just fill 'er up before you set up.
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Thanks for doing these tests. The jumper cable result is actually quite reassuring as we can all use that method in an emergency. #5 worries me a little though. The converter design shouldn't allow it to change charging current based on the input. The 120V side of the converter should be constant voltage and up to 10 or 15 amps (I forget what breaker they use for the converter), so I would have expected it to actually blow the fuse on the inverter before it would reduce the charging current. I wonder if the reduced output is because the inverter output isn't as clean as shore power. I know that some inverters make weird approximations of sine waves that can reduce efficiency and sometimes even damage certain devices.
Interesting results and a couple of questions/observations:
1. It would be interesting to report on a sixth (or is it fourth?) method- connection from the TV to the trailer through the trailer connector with the Tacoma's engine running (should be zero with it shut down due to a protective relay). I remember from years ago measuring something like 15-20 amps under similar conditions.
2. How long did you run the inverter test? Inverters can supply more than rated output for seconds to minutes depending on how much. If you ran it long enough the inverter may have tripped. The low charging current could be a result of the wave form, the lower AC voltage, or both.
3. Recognize that all of these values, particularly those measured while connected to the Tacoma directly will drop as the batteries get recharged. The Tacoma while running typically puts out about 13.5 V and as the batteries charge up, the charging voltage required to push that much current increases to the point that 13.5 isn't enough.
But I was interested in the direct connection results in any case. It beats a Honda 2000 external generator powering the converter, at least initially. I may need it some day!!!
David
I've successfully used jumper cables to bump up the battery charge a bit, but I'm not a fan of idling cars/trucks for a long time so I've only used them when absolutely necessary.
Any idea what vehicle manufactures say about engine idling?
Unless you're running dual 4 barrel Holley carburetors on a '67 Ford 409 with hi-lift cams, you're good to go with idling. Modern fuel management and engine design can easily handle extended idling. You just have to be very careful with carbon monoxide and make sure the exhaust isn't getting into the TV or camper. The charge tests Charlie ran are pretty telling. Looks like not much gas/time to charge those big batteries with TV jumper cables if shore power isn't available. I'm now in the market for some long jumper cables!
For the ease and convenience of not having a generator this seems like a viable alternative. I wonder at what point there would be a concern about the alternator being able to keep up in the long run.
.5 GPH seems excessive considering a decent 2000w inverter generator can go upwards of 4 hours on a single gallon. I know the generac is rated at 4.7 hours at 50% load on a single gallon.
[quote source="/post/5681/thread" timestamp="1419804405" author="@tinkeringtechie"] #5 worries me a little though. The converter design shouldn't allow it to change charging current based on the input. The 120V side of the converter should be constant voltage and up to 10 or 15 amps (I forget what breaker they use for the converter), so I would have expected it to actually blow the fuse on the inverter before it would reduce the charging current. I wonder if the reduced output is because the inverter output isn't as clean as shore power. I know that some inverters make weird approximations of sine waves that can reduce efficiency and sometimes even damage certain devices.[/quote][font size="3"]I had the same thoughts and questions, but I didn't feel like digging into it much. I'd seen this effect before but didn't want to get the O'scope out to chase it. I'm sure the truck inverter is just good enough to run lights and small tools. I've not looked at the on board converter in depth. If it's a true switcher you'd be right, but if it uses a transformer to get part of the way to 12V it might act strangely on weird waveforms. My main goal was to prove the #2AWG jumpers were worth the cost and effort over the truck inverter. I didn't really want the inverter, but it came with the off road package.
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[quote source="/post/5696/thread" timestamp="1419819009" author="@charliem"]My main goal was to prove the #2AWG jumpers were worth the cost and effort over the truck inverter. I didn't really want the inverter, but it came with the off road package.
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Well then you were successful. Don't worry about investigating the inverter further... I'd avoid running it that way since it has the potential to damage the inverter or converter (or both). Plus it just seems silly to convert 12VDC to 120VAC and back to 12VDC.
[quote source="/post/5682/thread" timestamp="1419806688" author="@david"]Interesting results and a couple of questions/observations:
1. It would be interesting to report on a sixth (or is it fourth?) method- connection from the TV to the trailer through the trailer connector with the Tacoma's engine running (should be zero with it shut down due to a protective relay). I remember from years ago measuring something like 15-20 amps under similar conditions.
[font color="e6193a"][font size="3"]Would be interesting info, but no way will it come close to the [font color="e6193a"]2AWG jumpers. Just too much #10 or less[font color="e6193a"] in the truck.[/font][/font][/font][/font]
2. How long did you run the inverter test? Inverters can supply more than rated output for seconds to minutes depending on how much. If you ran it long enough the inverter may have tripped. The low charging current could be a result of the wave form, the lower AC voltage, or both. [font color="e6193a"][font size="3"]I ran it for just long enough to get the current readings. The inverter was still running, but I didn't measure the voltages either at the battery or the AC input [/font][font size="3"]to the CL. The results were immediately evident.
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3. Recognize that all of these values, particularly those measured while connected to the Tacoma directly will drop as the batteries get recharged. The Tacoma while running typically puts out about 13.5 V and as the batteries charge up, the charging voltage required to push that much current increases to the point that 13.5 isn't enough. [font color="e6193a"][font size="3"]I recogniz[font color="e6193a"]ed this. [font color="e6193a"]I kept the run times short so I wouldn't significantly charge between setups, but the current drop was immediate[font color="e6193a"]ly evident, especially at the higher currents. And the 13.5 or so limit will prevent a complete recharge in any reasonable time, bu[font color="e6193a"]t the technique can pump a lot of energy[font color="e6193a"] [/font][/font][/font][/font][/font][/font][font size="3"]in a short time. Good for getting back to 90% SOC[/font][font size="3"], which is good enough while on the road.[/font][/font]
But I was interested in the direct connection results in any case. It beats a Honda 2000 external generator powering the converter, at least initially. I may need it some day!!! [font color="e6193a"][font size="3"]That was really my main interest. I don't want a gen or [font color="e6193a"]more GC2s. Every time I start thinking about adding [font color="e6193a"]heavy batteries I have to wake myself up and remember that carrying 20 gallons of gas is lots easier and cleaner if it's in the truck gas tank [/font][/font][/font][/font] :P.
David[/quote]
[quote timestamp="1419810646" source="/post/5685/thread" author="@michael"]I've successfully used jumper cables to bump up the battery charge a bit, but I'm not a fan of idling cars/trucks for a long time so I've only used them when absolutely necessary.
Any idea what vehicle manufactures say about engine idling? [/quote][font size="3"]No clue, but i wouldn't expect much trouble even for several hours at a time. Might have some crud build up, but that would be gone on the way home.[/font]
[quote source="/post/5691/thread" timestamp="1419813838" author="@sandroad"]I'm now in the market for some long jumper cables!
[/quote][font size="3"]I got mine a Sears Auto. Twenty feet long, #4 AWG pure copper. Watch out for cheap aluminum cables. NFG![/font]
Quote from: @admin" timestamp="1419818636" source="/post/5695/threadFor the ease and convenience of not having a generator this seems like a viable alternative. I wonder at what point there would be a concern about the alternator being able to keep up in the long run.
.5 GPH seems excessive considering a decent 2000w inverter generator can go upwards of 4 hours on a single gallon. I know the generac is rated at 4.7 hours at 50% load on a single gallon.
[font size="3"]The alternator is not a problem. Mine is rated at 130 Amps, but even a more standard 65 Amp alternator can handle the 50A or less charging current. And it's self regulating. The truck charger doesn't know the difference between it's own battery and the TT battery. Just might take longer if the alternator is smaller.
Re the gas consumption, remember the Tacoma is turning over a lot of metal and producing a lot of heat. There's a reason why Detroit puts tiny engines in cars to meet fuel economy regulations. All fine and good until you actually want to move something :D. If you really need to minimize fuel consumption use a small 1KW generator, but what a pain.
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