Extension Cord horror

[DeniseN]

Thanks again, GXMnow. This helps tremendously.

 

[SolarBro]

Hello. And thanks for all of the great information that you have made available. The pertinent instructions are on pages 7-8. I couldn't cut and paste the pdf.

I used a lv5048. Its been solid. I wouldnt put its output on an extension cord, you need to send the power to a panel.

 

[GXMnow]

I used a lv5048. Its been solid. I wouldnt put its output on an extension cord, you need to send the power to a panel.

I agree it is a rather large inverter to use for a portable rig, but I can see the use.

You can have a mobile system, bring it to a job site, throw out a few solar panels, and plug in a power distro box.
Now a crew can plug in power tools and with that size inverter, even fire up a table saw for a few cuts. It could replace a large noisy generator. If you only need high power for a few minutes at a time, it won't even take much solar to keep it charged up. But you have 5,000 watts when you need it. The other part is the battery bank that can also supply 5000 watts. That is about 100 amps on a 48 volt system. LiFePo4 cells like to stay under 1C so you need 100 amp hours of battery to keep up.

 

[jimjones26]

I also purchased the LV5048 after watching Will's video about 48v all in one systems. I also purchased 4 24V A123 LFP Battery Box w/ BMS batteries, wiring them up so I could have 2 48v batteries. My plan is to send the ac out to a box and then have an outlet that I can plug our camper into (50amp plug). I'm really confusing myself though, this is not as easy as I thought it was going to be!

 

[GXMnow]

Sounds like a decent plan. What is the rated capacity on the A123 cells? How much power do you need in the camper? I really do like the idea of a battery bank, solar panels, and an inverter instead of a generator running all night.

Be careful connecting 2 BMS units in series. Some do not like having double the voltage across the protection if it ever has to open. Maybe do the relay trick Will used one of his latest videos. The load is connected through a relay directly to the battery, bypassing the BMS. Then the BMS just powers the relay coil. It is a very slick solution. He actually had that relay then controlling a Victron Battery Protect, but a relay with a high enough current and voltage rating can do the job by itself. The coil will draw a bit of power though. I have found a few solid state relays that would take less power to activate, but not ones that will take 5,000 watts at 48 volts (100+ amps).

 

[RCinFLA]

I used an auxilary breaker panel for my backup loads. I selected the same manuf. panel as original main panel so I could use same type breakers for my main panel or aux panel.

Because my main panel is mounted on concrete wall I was able to mount aux panel next to it using a 2 inch diameter short conduit between boxes. You disconnect the backup branch lines from main breakers and add wires through short 2" diameter conduit to aux box breakers. It is code legal to use wire nut connections in main panel branch wires for extension wires to aux box breakers. You should balance the 120vac branches between L1 and L2 side of aux panel. They don't have to match their original L1 or L2 phase connecion that was on original main panel breaker placement.

Main and Aux box need ground wiring between boxes through 2" diameter conduit. Neutral from main need to be brought over to aux box neutral bus. I would use a single #6 white neutral connection although #8 would be legal. Inverter neutral goes to neutral bus in aux box.

You can get a box of plastic covers for your type of panel to cover the holes created by vacated breaker locations in main panel.

Aux panel L1, L2 backbone (main source power) comes from inverter output. It can be a 40 amp breaker mounted in top location of aux box. Inverter L1, L2 input goes to a 40 amp double pole (240vac) breaker in main breaker box for grid connection via separate added conduit between main box and inverter. Minimum #8 for 40 amp lines.

That inverter has only single AC source input so you need an additional transfer switch if you want to switch between grid and generator inputs. There are some 50A manual transfer switches around for about $150. Since you have a non-certified inverter (so already not legal) you could buy a 40 amp DPDT contact relay (about $20) and mount it is a standard 7x9" disconnect box. Should manually control it and never switch from a live gen to live grid immediately. The inverter needs time to release from one AC source phase before jumping on random phase of other source. A commercial transfer switch puts a time delay break-before-make to prevent this from happening.

If you are uncomfortable doing this yourself you could hire an electrician, either legally as an external generator hookup, or under the table. If done legally keep the inverter in the box, out of sight as a licensed electrician should not have any involvement hooking up an illegal inverter.

 

[jimjones26]

Sounds like a decent plan. What is the rated capacity on the A123 cells? How much power do you need in the camper? I really do like the idea of a battery bank, solar panels, and an inverter instead of a generator running all night.

Be careful connecting 2 BMS units in series. Some do not like having double the voltage across the protection if it ever has to open. Maybe do the relay trick Will used one of his latest videos. The load is connected through a relay directly to the battery, bypassing the BMS. Then the BMS just powers the relay coil. It is a very slick solution. He actually had that relay then controlling a Victron Battery Protect, but a relay with a high enough current and voltage rating can do the job by itself. The coil will draw a bit of power though. I have found a few solid state relays that would take less power to activate, but not ones that will take 5,000 watts at 48 volts (100+ amps).

We bought raw land and do not plan on bringing in electricity from the power company, as the costs are crazy expensive for where we are. So this will never be a grid tie type setup.

The manufacturer lists the Nominal Capacity of (1) 24v battery at 2.45kWh (92.8Ah). I am still learning about batteries so I am not sure how that changes when I wire 2 in series(?) to get to the required 48v for the LV5048.

As far as power in the camper, right now we are running a fridge and water heater on propane, a water pump, lighting and whatever power the fridge needs, on 1 12v battery. I have to run a generator around 3 hours everyday to keep the battery (lead acid deep cycle) from discharging too low.

Winter is coming, and I need enough power to run the heating system at night. Its a propane furnace but it will not turn on without having the camper plugged in to the grid. I need to figure out how much power it needs. Also, we charge 3 laptops, 3 phones, a camera battery, and really don't do much else.

Great news is, I live in Southern Colorado, and our property has great sun exposure. Bad news is, I have no idea what I am doing, really struggling to understand all of this. Want to make sure I don't burn out expensive equipment, or worse, start a fire.

I want to mount my LV5048 and batteries in an insulated 6x12 trailer, and then have an outlet in the trailer for a heater to keep temps above freezing, and then wire a 50amp outlet on the outside of the trailer that I can plug our camper into. If that can get us through winter I will be a happy camper, pun intended!

 

[RCinFLA]

Two 92 AH in series is twice the voltage same AH. Pretty feeble AH for 5kW inverter, 400 AH for 48v 5kW inverter would be more appropriate.

Not sure how the PV power is converted to AC on these 'tranformerless' inverters. If they use batteries as PV filter capacitors too little battery capacity may harm batteries if drawing high PV power to AC. It would take some massive capacitors to filter single phase AC ripple current from 5kW of PV power.

It can get by with less capacitance if allowing high ripple voltage at high voltage DC point that feeds PWM AC output sinewave synthesis. Issue with that is it puts high ripple current on the HV filter electrolytic capacitors causing them to fail early. GT inverters used to do this but they used large foil capacitors that can take the high ripple current.

My guess is they are using the battery to HV DC converter to fill in the ripple voltage at HV DC point. That means high battery ripple current.

 

[jimjones26]

So what would you suggest I do? Do I need to add 4 more of these batteries (2 in series, giving me two more 48v 92ah batteries) so I would have a total of 368ah?

 

[GXMnow]

In winter you will get fewer hours of sun, but the panels will get a bit more efficient. "Southern CO" is not precise, but we can assume it will average about 5.5 sunlight hours per day for a whole year, but it could be much lower in winter. You will want to set your panels up for best exposure in the winter. Here are two sites that can help. There are several more.

Solar Panels - Tilt Angle Effect | altE Solar Blog

altE's Solar Queen demonstrates the effect the tilt angle of your solar panels can have on performance and what factors you may want to consider.

www.altestore.com

Solar Panel Angle: how to calculate solar panel tilt angle? - Sinovoltaics - Zero Risk Solar™ - Quality Assurance for En

Discover how to calculate the optimum solar panel angle for your solar system according to your location and the season. Two calculation methods explained.

sinovoltaics.com

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Once you have a decent idea of how much energy you use in a typical day, you can work back and see how much solar panel you will need to produce that much energy in the sun hour available.

Just as an example, using easy numbers, but probably more than you need.

If you fall to just 4 sun hours in the dead of winter, and you need 8 KWH's a day, your panels would need to total 2 KW out of the inverter. Figure 10% of loss by the time you charge the batteries and then invert it for use. So about 2,200 DC watts of panels. Then you want a full day of energy to be less than 50% of your battery capacity. This way if you do have one bad sun day due to clouds or show on the panels, you can get by to get the generator going etc. So this hypothetical system would need 16 KWH's of battery. At 24 volts, that works out to 666 Amp Hours. When you series 2 batteries, the voltage doubles, but the Amp Hours stays the same, but you still get double the Watt Hours from the doubled voltage. When you parallel batteries, the voltage stays the same, but you get double the amp hours, again, doubling the watt hours. So to make this large battery array out of 12 volt 100 amp hour batteries, you would need 14 of them. Yes, this was based on a large amount of power at 8 KWH per day, but it gives you an idea how to calculate it when you do know your real power draw. If I exclude my air conditioner, my full size house uses about 28 KWH's per day, and my solar is making about 25 KWH's per day. I am typically buying 3 KWH's per day when I don't run my A/C. When I do need the A/C on 100 degree days, I have to buy up to 30 KWH's per day. Obviously this is way more than you should be using in a little camper.

Maybe you should buy one of those plug in watt meters and check what all your loads really need. Estimate how long each device runs to get the watt hours, but then you need an inverter that can run the peak load of the worst case of all items that might be on at the same time. And always figure in at least 20% more for those unexpected loads. Make sure to test the PC power draw while gaming etc.

 

[RCinFLA]

For 48v lead acid batteries should use no more then 1.5-2 kW of PV power per 100 AH's of battery capacity. You can have more PV panel power to make up for hazey days just don't use more then 1.5-2kW on clear sunny days.

Besides the high battery ripple current caused by using high PV power there is also the case of passing cloud causing much of AC load to be pushed over to short term battery support. Too great battery discharge rate can also damage batteries. For 48v 100 AH battery, 1.5kW to 2 kW is 32 to 43 amps of current drawn on battery. Drawing that much current for more then a few minutes is hard on a 100 AH lead-acid battery.

Drawing 25 amps on a 100 AH lead-acid with capacity rating based on 5 amps continuous discharge rate degrades available battery capacity down to 65-70 AH's. Need to check the fine print to see what discharge rate the advertised battery AH rating is based on. Typical is 5% to 15% of battery capacity rating in amps of discharge.

Also do not charge lead acid battery at greater then 15% AH rate in amps,

 

[Prefersdirt]

After many months of viewing and reviewing Will's videos, I convinced myself that I could build a system.

LOL. This is me too! Thank you for starting this greatly informative thread as when my batteries arrive, I will be in the same situation. I can start planning NOW. My head hurts. This project just keeps asking for $$. Better to cry once doing it right than cry many times fixing things.

 

[GXMnow]

Batteries tend to be one of the most expensive parts of an off grid setup. And even a load shave and time shift like my system, they can be a chunk of the cost. But having enough battery is key to making it all work. I got lucky with the deal from Battery Hookup. They frequently have some package that come out to about $100 per Kilowatt Hour. My 17 KWH's came in just under $2,000 for the LG Chevy Bolt packs, shipping and all. But to make use of things like that, we need to DIY a fair bit and working with raw lithium batteries does require a lot of care and there is some risk. Getting a package LFP like a Battle Born is very safe and will certainly give you many years of service, but there is a cost involved. A 100 AH 12 volt battery costs about $950. 12 of those would still fall short of my battery bank, and cost over $11,000. That is well over 5 times the price. My Schneider XW-Pro inverter ended up costing about $4,000 with the Gateway and other items needed to get it connected. Once you figure out the power needs, you can plan out the amount of storage you need and the power needed for the inverter and solar to keep it charged.

It is best to plan to use less than 1/2 the battery capacity, even with Lithium as that gives you a reserve, and will also make those expensive batteries last much longer. AltEStore has a video explaining that with Lead Acid, it actually reduced the system cost to only use 1/4 of the battery capacity by doubling the battery bank. It does cost more up front, but since the batteries are only using 25% capacity each day, they last far more than double the number of cycles. My hope here is that by the time my Chevy Bolt packs give up, there will be better batteries available for a decent price. With all the new EV's coming out, we may have a great source of batteries coming down the line.

 

[jimjones26]

Thanks for the info guys. I am even more confused now, but I will keep reading through the posts until it becomes clear.

Did I make a mistake buying the lv5048 and the 24V A123 LFP Battery Box w/ BMS batteries to pair with it? All I really need to make sure of is the battery bank can power the RV heater through the night. We do have a generator we can run to supplement things if we have a few cloudy days, but I really don't want a generator running all night all the time.

I need to figure out how my energy the rv heating system uses and go from there.

We moved to just outside Pagosa Springs, CO. From what I can tell online, it looks like we average 6 hours of sun a day.

I should have known it was not as easy as the video made it seem!

 

[SolarQueen]

As much as I love Will, he tends to yada yada yada over some very important parts of the install.

 

[KBurns]

Thanks for the info guys. I am even more confused now, but I will keep reading through the posts until it becomes clear.

Did I make a mistake buying the lv5048 and the 24V A123 LFP Battery Box w/ BMS batteries to pair with it? All I really need to make sure of is the battery bank can power the RV heater through the night. We do have a generator we can run to supplement things if we have a few cloudy days, but I really don't want a generator running all night all the time.

I need to figure out how my energy the rv heating system uses and go from there.

We moved to just outside Pagosa Springs, CO. From what I can tell online, it looks like we average 6 hours of sun a day.

I should have known it was not as easy as the video made it seem!

That's my problem too. I didn't realize the importance of the 92 AH on those batteries until I came to this forum asking 'how to' with those batteries with the lv5048. And I only bought two of the batteries. I understand that we shouldn't mix and match batteries. It's almost as if we're stuck buying batteries from the same vendor.

 

[GXMnow]

Yes, in a perfect world, all of the batteries should match. But we all know this is no perfect world.

So here are the important rules.

Any string of batteries running in series must be well matched. As the string is charged and discharged, you really need to voltage across each cell in the string to stay the same. Any difference in capacity will effect this. A cell balancer will take care of a small difference, but a that should not be depended on.

As long as you use the same chemistry, you can parallel different cells to a point. When a system of parallel packs are charged together, the current will flow in the path of least resistance. So if you have a 200 AH group in parallel with a 50 AH group, most of the current is going to flow in the 200 AH group. And if one bank starts to drop charge a little more, it's internal voltage will dip and then the other pack will take more of the load, so it does become very self equalizing and each cell in parallel should reach full charge and discharge states at very close to the same time. Just think of a Tesla pack with all those 18650's in parallel. Think of it like one pack is 80% of the cells, and the other pack is just 20% of the cells, a four to one difference. They all work together just fine. Even if they age different, as a cell get's weaker, it will just take less of the current.

Using different chemistries....
This is a bit trickier, but still possible, but with some caveats.
Let's try a 16S LFP pack in parallel with a 14S NMC pack. Obviously the two packs must have independant BMS systems and fuses.
The fully charged voltages are 3.65 volts per cell for the LFP for a total of 58.4 volts.
The Fully charged voltage for NMC is 4.2 volts per cell for a total of 58.8 volts.

That end is pretty close. If you set the Absorbtion voltage under 58.4 volts, it will be safe on both and the NCM will still hit over 90% charged, but you couldn't fully top them out.

On the low side, the LFP can go down to 2.5 per cell without damage. For 16 cells, that is only 40 volts.
The MCN should not go below 3.0 volts per cell. 14S comes out to 42 volts.

This not as close, but it is still workable. Make sure to set the low voltage cut out higher than 42 volts and you won't hurt any of the cells.
You won't be able to get all of the energy out of the LFP cells, but you can still get over 80% out.

The discharge curves are not the same. At the top of the charge, most of the discharge current will probably be coming from the NMC cells. They will start dropping SOC faster, but as their internal voltage starts to fall, the LFP will pull more and more of the load current and it works. The total usable KWH's will be about 90% of the NCM + 80% of the LFP but the peak power you can pull from the system should be limited to what the weaker pack can take on it's own. So no matter how bad the imbalance get's during the charge or discharge cycle, no battery string is ever overloaded. So you can increase your system capacity for a longer run time, but don't expect to be able to take any more peak current. Obviously you will get some, but just don't depend on that for the system to work and be safe.

For my system, I am using 360 AH of 14S NCM cells. That could take a peak power of over 18,000 watts at just 1C. I am only running a 6,800 watt inverter. So if I wanted more run time, I could add a 280 AH LFP pack that can take 0.5C or 140 amps and run that in parallel with my existing batteries. My usable capacity would go from 17 KWH to about 15.3 (90%) + (80% of 14.3 =) 11.4 = 26.7 usable KWH's. Both strings can run the inverter on their own, and they will share the load fairly well. It would be better to use more of the same type of cells, but this is not impossible to make work. With a "Smart" BMS on both packs, you can easily monitor how well the current is being shared.

With those 92 AH packs that you have, what are their charge and discharge C rates? Can a single set put out over 5,000 watts to run the inverter? If not, you really should parallel more of the same to make that possible. I have not pushed my inverter past 4,000 watts yet, but I am sure the system will take the full 6,800 without a problem. Even the 12,000 watt surge should not hurt anything. Over building will add cost, but it makes for a much safer as well as longer lasting system.

 

[jimjones26]

Here are the specs for the battery. I'm not sure what calculations will give me the answers you seek. I did buy 4 of these packs. I really appreciate you all taking the time to answer my questions.

---

This battery box includes the following:

(1) 24V A123 LFP Battery

(1) 130A 8S BMS

(1) 24V A123 LFP Battery to 8S BMS Adapter

(1) 24V A123 LFP Battery Box

YES – you can connect Parallel for increased capacity. (Up to 8)

YES – you can connect in Series for 48 volts. (Up to 4)

Electrical Specifications

Nominal Voltage: 26.4V

Voltage Range: 20V – 28.8V

Nominal Capacity: 2.45kWh (92.8Ah)

Configuration: 8S5P

Energy – 100% DOD, Nominal: 2.6 kWh

EV Energy – 80% DOD, Nominal: 2.1 kWh

Chemistry: LiFePO4 (LFP)

Cell Type: 20Ah Nanophosphate Cells

Cell Count: 40

BMS Specifications

Single cell overcharge protection voltage:

• Min: 3.72V
• Standard: 3.75V
• Max: 3.78V

Single cell overcharge protection delay time:

• Min: 0.6S
• Standard: 1S
• Max: 1.5S

Single cell overcharge recovery amperage:

• Min: 3.5A
• Standard: 3.6A
• Max: 3.6A

Recharge current:

• Max: 130A

Single-section equalization voltage:

• Min: 3.55V
• Standard: 3.6V
• Max: 3.65V

Single-section equalization current:

• Min: 35mA
• Standard: 40mA
• Max: 45mA

Single cell over-discharge protection voltage:

• Min: 2.15V
• Standard: 2.7V
• Max: 2.8V

Single cell over-discharge protection delay time:

• Min: .6S
• Standard: 1S
• Max:1.5S

Single cell over-discharge release amperage:

• Max: 130A

Discharge protection current:

• Min: 350A
• Standard: 370A
• Max: 390A

Charging high temperature protection:

• Min: 85℃
• Standard: 90℃
• Max: 95℃

Physical Specifications

Length: 18in

Width: 10in

Height: 8.5in

Weight: 60lbs

Operational Specifications

Operational Temp Range: -30℃ ~ 55℃

Storage Temp Range: -40℃ ~ 60℃

 

[jimjones26]

I bought Will's book and I am reading through it now, hopefully I will understand how to answer your questions here soon.

 

[jimjones26]

So I bought 4 of these 24V 92.8 aH batteries. If I put two in series, that will give me two 48v 92.8 aH packs. Parallel those packs and I now have 48V 185.6 aH battery bank.