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Old 01-24-2017, 10:49 AM   #261
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Unfortunately there is no setting to control the current. I went with the 120 because I measured the system as it was and I was getting in excess of 100 amps into the lead acid batteries. So didn't want to go backward. In mine, the wire leading to the front battery is quite beefy. I forget now but it is something like 2/0 and such. And with 220 amp alternator that was the right strategy.

BTW the 120 amp is the *input* rating for the battery to battery charger. Its output is some 10 to 20% lower. It was low enough to not cause SBMS to shut down.

SBMS actually handled more current than spec'ed. I had both by AC charger and alternator running with average current now shooting up to 120 amps or so and it was still happy. I asked Dacian and he didn't think that was possible.

For me, having maximum charge from the engine was very important. It would allow us to quickly charge the batteries back up with a short drive or idling in the morning. So if at all possible, I would opt for the 120. But you have a lot of constraints to worry about from having to run another wire, to your alternator capacity, over current of SBMS due to your higher solar charge, etc. So not sure what to recommend .
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Old 01-24-2017, 10:55 AM   #262
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One other thing: I was able to run the AC off that Xantrex inverter *but only when outside temps were around 60 to 65 or so*. Anything above would cause it to shut down as soon as the compressor wanted to turn on. It was very cool, pun intended , to be able to run the AC without any hook up! So at some point I am going to get a soft-start for the AC as to be able to do that.

The usage would be to be able to run the AC for short whiles and then having the engine quickly recharge them. Alternatively you can run the engine concurrently while running the AC if you had the 120 amp battery to battery charger. This would eliminate running the noisy generator.

Again, this hinges on putting a soft start circuit in the AC.
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Old 01-24-2017, 10:58 AM   #263
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I don't yet have a feel for whether or not that would be possible, or if it is, within what operational limitations. Living off the sun alone with only one Lifeline was easily done as long as the usage was casual - we had buckets of juice to spare as long as we were just engaging regular 12 volt draws from lights, refrigerator, maybe the furnace fan, water pump, Fantastic, device charging, etc. but no major energy sucks such as a 17" Dell mobile workstation which is plated as drawing up to 240 watts.

It's an important question because my ultimate goal is maybe to spend a week off-grid at a time, much of it working. Even if the upgraded alternator is there, I foresee intervals of minimal driving.
With existing batteries I have heavily relied on engine charging. It was the only way we could recover from night-time usage.

Right now with lithium, when we wake up, i power the engine to charge the batteries and at the same time do our high-energy things like using the microwave. We also take frozen meat for our dogs dinner and thaw them out in the microwave with engine running no matter where we are. Hate to run the noisy generator in the middle of city, etc. Actually I hate running the generator period.
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Old 01-24-2017, 01:28 PM   #264
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Our refrigerator is propane so we don't consume a lot of electricity overnight. I've worked up some power budgets but it's TBD to see how much juice the computers actually use or how much we actually use the microwave but to date we have rarely used more than 25-30Ah after sundown.
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Old 01-25-2017, 06:10 AM   #265
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I had my first boondocking overnight with the new system last night. Batteries are down to 95% this morning and the system is behaving as expected. We had a cold front come through central Texas, but I did not need to turn on the furnace. That will change tonight as I think we're going down into the 40's.

One wild card with respect to my computer is the lithium battery system that is within it. Of course, there's the lithium system in the van but there's a separate one in the computer itself. This particular business machine is a brand new Dell mobile workstation, and right now it's telling me it has 5 hours 47 minutes of battery left in it (91% full). I suspect it's lying like a dog, because I think I should be expecting something closer to 3 hours. But the question I have is, where will be the sweet spot of running off the computer's battery and then using the van system to charge it back up for another usage cycle, vs. directly running off the inverter? I have no feel for that yet.
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Old 01-25-2017, 06:54 AM   #266
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The key is to charge your energy hog of a computer (or use any major intermittent loads) when the sun is shining.
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Old 01-25-2017, 07:37 AM   #267
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I can get 7-9 hours on my dell computer. The big hog is the display. Turn the brightness down and use power saver mode. I do this on Long flights. When in normal power mode the battery may last three hours. Big difference. All depends on how bright you need it.
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Old 01-25-2017, 10:39 PM   #268
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If you can run the computer off DC that would be best. Even a step-up is generally more efficient than an inverter (well, from my experience).

I'm not familiar with that particular machine (we used Dells at work for most stuff- but tried to stay with one type of laptop and one type of desktop for generation. Saved loads of setup--of course, that was before I retired)
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Old 01-26-2017, 07:15 AM   #269
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The new bee in my bonnet this morning is whether a 12-volt electric blanket might be practical now that the lithium is in place. I had assumed it was out of the question back when we were operating on one Lifeline - I didn't even look into it. Resistance heating is soooo much less efficient than combustion... normally. But with big lithium batteries and a little propane tank, the equation potentially changes.

It got down to 40 degrees last night, and I set the furnace at 60 (which means it's about 50 to 55 at bed level because the thermostat is only a foot below the ceiling and stratification becomes more pronounced the colder it gets). I can survive with it being colder than that, but I wasn't in the mood. I had all the Reflectix in the windows, but the interval between successive furnace cycles was still only 9 minutes. What little propane our Interstate can carry is being chewed up at a fast clip - that's the bad news. The good news is that the furnace only increased the overnight battery consumption by an additional 2% of total capacity.

I don't need to heat the whole Interstate, though - I just need to heat myself. OTR truckers use these blankets; in fact one of their websites provided this example calculation that I've reproduced below. So, when I get free of work obligations this week, I'll have to look into possible blanket vendors. I'm headed to south Texas for another business meeting tomorrow morning, and the overnight low there is about 10 degrees warmer than here, so this will be less of an issue tonight.
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Old 01-26-2017, 04:36 PM   #270
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The new bee in my bonnet this morning is whether a 12-volt electric blanket might be practical now that the lithium is in place. I had assumed it was out of the question back when we were operating on one Lifeline - I didn't even look into it. Resistance heating is soooo much less efficient than combustion... normally. But with big lithium batteries and a little propane tank, the equation potentially changes.

It got down to 40 degrees last night, and I set the furnace at 60 (which means it's about 50 to 55 at bed level because the thermostat is only a foot below the ceiling and stratification becomes more pronounced the colder it gets). I can survive with it being colder than that, but I wasn't in the mood. I had all the Reflectix in the windows, but the interval between successive furnace cycles was still only 9 minutes. What little propane our Interstate can carry is being chewed up at a fast clip - that's the bad news. The good news is that the furnace only increased the overnight battery consumption by an additional 2% of total capacity.

I don't need to heat the whole Interstate, though - I just need to heat myself. OTR truckers use these blankets; in fact one of their websites provided this example calculation that I've reproduced below. So, when I get free of work obligations this week, I'll have to look into possible blanket vendors. I'm headed to south Texas for another business meeting tomorrow morning, and the overnight low there is about 10 degrees warmer than here, so this will be less of an issue tonight.
Did you notice the fall in their logic and math? You don't have 100 usable amp/hours in a 100 Ah battery.... Lead based batteries have 50% and lithiums 80%.
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Old 01-26-2017, 08:07 PM   #271
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Did you notice the fall in their logic and math? You don't have 100 usable amp/hours in a 100 Ah battery.... Lead based batteries have 50% and lithiums 80%.
And truckers keep their engines running all night!
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Old 01-26-2017, 09:32 PM   #272
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Did you notice the fall in their logic and math? You don't have 100 usable amp/hours in a 100 Ah battery.... Lead based batteries have 50% and lithiums 80%.
CORRECTION!

They slid in a factor of 2 times the amp/hour rating of the heating element draw. this would account for a 50% usable amp/hour battery capacity. Sorry for the confusion!
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Old 01-26-2017, 10:16 PM   #273
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If you can run the computer off DC that would be best. Even a step-up is generally more efficient than an inverter (well, from my experience).

I'm not familiar with that particular machine (we used Dells at work for most stuff- but tried to stay with one type of laptop and one type of desktop for generation. Saved loads of setup--of course, that was before I retired)
Nobody makes a 12->19v power supply in the same wattage as her computer brick so I purchased a 200+ watt DC/DC converter a while back. But the trick with the current Dell computers is that they must receive a verification signal from the power supply before they will charge. I ordered the proper chip almost a year ago but I'm not aware of any affordable chip programmers to encode them. One day I hope to build the proper circuit and serial computer interface but that's a bit beyond my current knowledge base so it will be a while yet.
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Old 01-27-2017, 05:39 AM   #274
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Nobody makes a 12->19v power supply in the same wattage as her computer brick so I purchased a 200+ watt DC/DC converter a while back. But the trick with the current Dell computers is that they must receive a verification signal from the power supply before they will charge. I ordered the proper chip almost a year ago but I'm not aware of any affordable chip programmers to encode them. One day I hope to build the proper circuit and serial computer interface but that's a bit beyond my current knowledge base so it will be a while yet.
Interesting! I used to have a Panasonic lap top that also has an aux. DC charger. It plugged into the 12VDC 'cigarette lighter' port and IIRC, it provided the 19VDC for the unit's operation.

Of course, that was many moons ago...................
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Old 01-27-2017, 05:48 AM   #275
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Lew, we looked into it in detail and I spoke with Dell's technical support at length (I buy the pro-support package because it's a business machine and they are VERY good at giving you as much attention as you need... it's the deal of the century and it's what keeps me buying Dells).

There are laptops that will do what you say, but not this one. And I didn't want to choose my main business machine based on the Interstate's current limitations when I'm only using it in the Interstate for maybe 4 or 6 weeks of the year. The rest of the time I'm at my desk or I'm an embedded contractor and those are the conditions that dictate which machine I choose.
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Old 01-27-2017, 05:56 AM   #276
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And truckers keep their engines running all night!


This was supposed to be an illustration for truckers of what would have to happen such that they could stop running their engines all night. Because that's a more expensive option than running a 12 V system, if one can get the battery power.
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Old 01-27-2017, 07:04 AM   #277
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Seems like I have purchased a computer charger that plugs into the cigarette lighter before. You did mention that wattage was an issue so maybe that's the problem.

I am still working on my 480 aH lithium conversion using victron components. One of the questions I have is what limits the amount of current coming from the alternator to the house batteries? There is a 150 amp fuse on The Wire coming back from the alternator so does the alternator somehow limit itself to roughly that amount of current or with a big lithium battery Bank do I have the potential of drawing more than that and blowing the fuse?
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Old 01-27-2017, 07:25 AM   #278
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Mineralframe, is it the wire size that limits the current?
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Old 01-27-2017, 08:01 AM   #279
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Airstream uses a 1/0 cable to connect the alternator (start battery) with the house battery via the Precision Circuits BIM device. Certainly 1/0 is capable of far more amperage transmission than 60 amps, which is about the highest that I have seen.

When using Victron lithium batteries and other components, The Victron battery monitor system requires that the chassis ground be isolated from the house battery ground as a difference in potential (2 separate battery systems) can present problems for the BMS system.

The recommended device to isolate these systems is the Orion DC to DC converter, but they are limited to 30 amps. In the last full Victron AI installation that I did, I used 2 Orions in parallel for a potential 60 amp alternator charger for the lithiums.

If your lithiums are low and need a charge, 60 amps per hour would easily bring the lithiums back up to full charge (even though it is not required) during a normal driving day of 4-6 hours. The problem is knowing when to remove the alternator charge after the lithiums are full. The BMV-702 with blue tooth dongle lets you monitor the charge progress from your phone.
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Old 01-27-2017, 09:54 AM   #280
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The T1N interstates never had an inverter so the peak loads are very different when compared to the newer Interstates. As a result, Airstream used a 4 awg wire between the converter, house battery, and alternator and I wasn't ready to push that to 120 Amps. I would love to be able to charge them in 2 hours instead of 4 but I don't like big high amp cables under the chassis where a tire tread could damage them and cause a fire, not to mention the limited availability of alternators than can output well over 200A for hours on end.
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