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GlennWest

Chevy volt battery questions

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When I looked at a 48V system the issues where.

- Bigfoot hydraulics.

        - Using 115V Bigfoot pumps with a 12V control system.  At 115AC the pumps draw 4-6amps each.

        - Running two 12V motors tandem draws 140amps.  For this I was gong to use a 2-6V battery bank.  To supply enough power to keep the pumps running for 4-5 min I figured on 3 (2+1spare) DC-DC converters.

- To charge a 48V bank with a MPPT controller the input voltage needs to be +80V.  Running 2 panels that I have in Series =140V.  This meant that 250V controllers are needed.

-  12V to 48V vehicle charging

- 120VAC to 48V charging with 120VAC to 12V back up.

- Monitoring the 48V or the 12V as well

 

 

 

 

 

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You can eliminate the charging from tow vehicle while towing. The charge isn’t very much ar all. You have solar panels and they will charge while traveling as well as sitting still.

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A standard 12 volt converter, fed by a 120 volt inverter connected to the main battery bank should be able to run the slide motors and other 12 volt needs without a battery.

Back in 2000, I purchased an Artic Fox 26x trailer from a salvage yard and it didn't have a battery while I was evaluating it.  To test the slide operation I plugged the trailer into my Honda EU1000i generator and the PD 9145 converter easily handled running the 12 ft. slide in and out, including the stall current when the slide reached It's end of travel.

Progressive Dynamics converters work fine on Modified Sine Wave.  After I installed four GC2 golf cart batteries  I disconnected the standard 12 volt charging wire coming from the truck and replaced it with a 1000 watt truck stop MSW inverter mounted in the truck.  I ran 120 volts back to the trailer via a twist-lock connector at the hitch and the converter performed just like it did on shore power, delivering it's full 40 amp bulk charge to the trailer batteries.

Edited by Lou Schneider

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12 minutes ago, Lou Schneider said:

A standard 12 volt converter, fed by a 120 volt inverter connected to the main battery bank should be able to run the slide motors and other 12 volt needs without a battery.

When I first got my Artic Fox trailer from a salvage yard back in 2000, it did not have a battery.  I plugged the trailer into my Honda EU1000i generator and the PD 9145 converter easily handled running the 12 ft. slide, including the stall current when the slide was fully in.

Are you saying, as in my case, I have a factory converter/charger unused. I could use it for my 12v load and be fine without a 12v battery in the mix?

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Yes, with a couple of cautions.  It will work as long as the converter is a modern design and not something like the old non-regulated Magnetek 6300.  What kind of converter do you have?

Without a 12 volt battery, you'll have to supply 120 volts to the converter to have 12 volts in the RV.  This means shore power, generator or leaving the inverter on if you have something like a refrigerator that needs a continuous source of 12 volts for the control board.

Also, if you have 12 volt lighting, no lights will work until you either plug in or start the inverter.

Edited by Lou Schneider

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Glenn--Jack---Why????  What is the benefit of 48 volt? Why not just configure to 12 volt?

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Lou is correct as far as he took it. My experience is similar to his. However, if you have a larger diesel genset (or even a gas one) you may not be able to start it without a battery "bank" of some sort because of the start load. I have not tested this, but I know the start load on a diesel genset is pretty large. And you may have to try for a while under some circumstances. Comments???  Lou??

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8 minutes ago, Daveh said:

Glenn--Jack---Why????  What is the benefit of 48 volt? Why not just configure to 12 volt?

So much better/nicer goodies available.  

Edited by GlennWest

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2 minutes ago, Jack Mayer said:

Lou is correct as far as he took it. My experience is similar to his. However, if you have a larger diesel genset (or even a gas one) you may not be able to start it without a battery "bank" of some sort because of the start load. I have not tested this, but I know the start load on a diesel genset is pretty large. And you may have to try for a while under some circumstances. Comments???  Lou??

For me there will not be a large generator in our mix. Just not room for it. Now I could put one on truck. Cross that later if so. My thoughts now are a Honda or such for supplement charging. 

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2 hours ago, Ronbo said:

You can eliminate the charging from tow vehicle while towing. The charge isn’t very much ar all. You have solar panels and they will charge while traveling as well as sitting still.

Yes but.... : )   if Lipo are used the battery bank need to be kept warm. If it is snowing one can't depend on solar.

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But with the lithium battery voltage doesn't degrade like lead acid. Solar going in at later date. For now get this working and then solar. 

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44 minutes ago, J-T said:

Yes but.... : )   if Lipo are used the battery bank need to be kept warm. If it is snowing one can't depend on solar.

We are talking fifth wheels, I think. The only time cold temp is a factor for lipo is when they are charging. Don't charge them if they get  below 32 degrees. The batteries are fine in the cold you can use them---just don't charge them. I have my batteries located in a bay where they get some residual furnace heat so I doubt they have ever see 32 degrees. I am more worried about very hot temps .    I am talking about LiFePo4 batteries. I think the chevy volt has a slightly different chemistry. 

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5 minutes ago, Daveh said:

I think the chevy volt has a slightly different chemistry. 

Correct. They are NMC's.

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Using a 12V battery is perfectly legit.  In fact that is how 48V automotive is done.  The 3KW 48-12 converter is in its infancy so far.  Everybody has designed one but few make em yet.  They will be everywhere by this time next year.  So the Sensata is probably the only off the shelf unit for now.  48V is pretty cutting edge so it isn't cheap.  Once the 2019 Audi R8 comes out this fall you can probably just go down to your Audi dealer and get a 3KW converter.

2019-audi-a8-48-volt-electrical-system.j

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Scrap, what do you think of the idea of the three 60 amp buck converters on a load surge? These are the 48/12.  I have no idea what starting surge they will supply, but my guess is "not a lot". The Chinese are not talking. 

I have them, so I suppose I should get around to testing them sometime.

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From what I could figure out it will depend on the % of the capacity used and the duty cycle of the converter.

Plan a was 3 (2+1 spare) Victron converters. 

Plan b  was  1 (+ 1 spare) buck converter enough to power the lite trailer loads and a Blue Sea electric battery switch to disconnect the converters from the 12V battery bank under peak (Bigfoot) loads.    

Edit : We are elec/hyd on the brakes so a 12V battery is a requirement.

Edited by J-T

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Regarding DC motor loads, full field voltage and use a current limiter on the armature.    I have DC drives on a couple of machines, at full field 120 VDC and a car battery I can run my 5 HP 240 VDC lathe.

Here is a good start for current limiters 

https://www.ametherm.com/blog/inrush-current/dc-motor-inrush-current    

 

Steve

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We've done it with a couple of Sevcon's on the bench for an hour long demo Jack but not in real life on a transient truck, so I'm not too sure.  But hey if you got em already might as well try them!  It was also for three PWM controlled scavenge pumps for the cooling oil for a traction motor and they did have to make some inrush limiter and software ramp up like Steve posted.  In reality as soon as they spun it up for the first time it shot ATF across the shop from a hose screwup so I had to tend to that while they figured out their motors and converters and I missed most of what they did.  So I might not be too relevant.  Those three pumps were the bain of the electrical guys for a good long time so you are in good company! ;)

The new automotive converters go both ways as buck & boost, which is another benefit they have.  Barring being able to get one of those for the next year we'd probably attempt a 12V ultracap where you can charge at 25A for 10 min and then hope it has enough oomph to make it through a jack cycle (well, don't hope but do the math).  They started making large 48V ones now too that might be useful as a big buffer when the heavy users go 48V too.  You don't want to burn through half your battery charge just to make a trailer level!

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Thanks, Scrap. I'm going to do some testing in the next couple of months...I'll report back on "real life" use. I suspect they will fail the test, though. 

That leaves me in the position of using a 12-volt battery dedicated to the genset and Bigfoot. That is not a terrible thing....but I'd avoid it if I could.

BTW, are you going to MATS this year? I may swing down there for a look-see.

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Sorry, I’m slow on the uptake in electrical matters. To simplify the discussion in my mind, What we are talking about is battery supply for what size converter(s) are needed to push the entire coach load via batts/inverter at all times? I assume this is why running multiple inverters and the 48v batt bank? Two ACs and normal everything else in 40 ft Teton. Are we talking two 3000 watts? Two 4000 watt inverters? And is a single volt battery enough? Or are you creating the 48v banks from multiple volt batteries? 

And if I am also understanding correctly, still need a couple of 12v batts to run the jacks and slides? Are you making a 12v bank from the Chevy volt batt? Or just a couple of agm’s?

 

I’m in similar situation of Mr. Glenn. Adding solar later.

Granted, most of my knowledge on this subject is from reading the forum and Mr. Steve’s video walkthrough of his new coach. So trying to learn as I want to do this in spring. 

Edited by lockmup68

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 I will have all mini split for cooling and heating soon. Very satisfied with our current mini split just need more. This is the limit with lead acid batteries, ac. My mini split pulls on high side 6amps. This is the most I have recorded so far. All summer and now into 20's and 30' temps. My thoughts now is a 220 unit and 2 heads. 30,000 btu. 220 not an issues with 48 volts. I intend to sorta copy Steve Dixion set up. Teton will operate off of the chevy Volt battery pak and supplied inverters. We all sorta figuring out best way to handle high DC loads. Separate 12v battery is simple and need separate charger also with this route. Been suggested just converter will work.

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