Right Questions to Ask when buying 'All-in-one' Battery

geekgonewild

My project is to install Solar Power System on my trailer, which could handle 3,000-3,500 Watt continuously, with 3,500-4,000 peak wattage – essentially mirroring 30 AMP shore connection.

Core items in my future setup, specs of which match:
- Six 300 Watt solar panels Nom Voltage: 30V, VOC: 40V, 9.8A. (Already purchased)
- All-in-one 48V battery system with about 10kwh capacity & 80amps of continuous current. (Will be purchasing)
- Off-grid All-in-one Charger+Inverter (48V to 110AC + 12V DC) and (150VOC, 80A & MPPT). (Will be purchasing)

Weather conditions: -5F to +110F, 20%-80% humidity, up to 80mph winds (including while driving).

What I need is help on all-in-one battery system I’m buying from China. Specifically, what are the right (or all) questions I need to ask?

So far, questions from my lists are (I enumerated them for easier reference):

1. Low & High Voltage Protection?

2. Low & High Current Protection?

3. Low & High Temperature Protection?

4. Does it have passive and active cell balancing?

5. Customization: Option to install heating pad (film or plate)? And, how easy to install without voiding warranty.

6. Installation: min space needed on Sides, Top & Bottom.

7. Connections, Monitoring or Communications? (including for applying changes): Bluetooth, Wifi, Wired? What software available?

8. Does it talk other components, like Off-grid All-in-one Charger+Inverter - I'm looking for.

9. Shipping, handling within/outside of the US.

10. Inspection (at the port of entry and elsewhere)

I would love to hear from everyone to expand on these questions and topics and share their list(s).

Again, thank you for sharing your thoughts from your past experiences to help others, like me.

BB.

Can you tell us a bit more about your loads and where the system will be used (near what major cities for hours of sun per day), what seasons, full time off grid, etc.?

It sounds like you are looking at Li Ion batteries? Do you have some way to keep them warm (>~40F) in cold weather?

How large of solar array can you mount--If you are out in the US South West--Mounting panels flat to roof can work pretty well... If you are going up north, in winter, etc. then being able to tilt the array into the winter sun is a big help.

Will you have a backup genset? If you don't have any sun (shading, bad weather, winter, etc.), solar just does not cut it alone.

Your expectations from your battery bank/solar array is a lot. Generally, for an RV, a smaller inverter+battery bank is a better fit (roof space, and battery space/weight). Use the small system for "quiet times", and a genset for larger loads (saws, pumps, compressor, etc.)????

-Bill

Photowhit

In this case it appears 'trailer' means camper/RV. Since NEC isn't involved, I'd suggest moving this to RV's @BB.

@"geekgonewild" Figure out what you need before buying anything more! 

A system that "...mirroring 30 AMP shore connection" will be very hard to put on a RV, even with auto start generator!

Consider 30amps at 120 volts is 3600 watt hours or over 1/3rd of your proposed battery storage.

BB.

Photo white,

Thank you, I have moved.

Bill

geekgonewild

BB. said:

Can you tell us a bit more about your loads and where the system will be used (near what major cities for hours of sun per day), what seasons, full time off grid, etc.?

It sounds like you are looking at Li Ion batteries? Do you have some way to keep them warm (>~40F) in cold weather?

How large of solar array can you mount--If you are out in the US South West--Mounting panels flat to roof can work pretty well... If you are going up north, in winter, etc. then being able to tilt the array into the winter sun is a big help.

Will you have a backup genset? If you don't have any sun (shading, bad weather, winter, etc.), solar just does not cut it alone.

Your expectations from your battery bank/solar array is a lot. Generally, for an RV, a smaller inverter+battery bank is a better fit (roof space, and battery space/weight). Use the small system for "quiet times", and a genset for larger loads (saws, pumps, compressor, etc.)????

-Bill

Responses to :

Paragraph 1: Loads need to satisfy 3,000-3,500 Watt continuously, with 3,500-4,000 peak wattage. This is only when Air conditioning (2.3-2.9kW continuous, 3.5kw starting) is on for up to 4 hours a day. 

Paragraph 2: lishen Lifepo4. -5F to +110F. Point #5. heating pad etc.

Paragraph 3: - Six 300 Watt solar panels Nom Voltage: 30V, VOC: 40V, 9.8A. (Already purchased). Mostly will be moving with weather in the continental US but will venture to higher elevations. I am building slide out system for panels on the suv & travel trailer.

Paragraph 4: Yes, will be picking up a small genset for just in case. 10kwh+ battery bank is provisioned for off-grid + 5 days cloudy days.

Paragraph 5: Never needed a generator since i installed DYI 2kwh EVE lifepo4 battery w/1k inverter & 600W (300w on suv, 300w on trailer) panels & can run everything but Air Conditioning and suffer when 3+ days of cloudy days - essentially cannot both cook (instant pot) & have a hot coffee or tea because no juice left to run my office. But, this time around i want all-in-one battery since they are cheaper then DYI when considering tools, materials, time, etc. Measured spaces on suv & trailer's roofs. And, weighted a loaded setup on CAT scale & will be within 200lb limit for the trailer. But, with added weight, i will need to get a wider tires on the suv to decrease probability to get stuck.

Is it reasonable to ask for cell specs from the manufacturer of all-in-one battery?
Any reputable companies that help with inspection and/or delivery.

Thank you for your feedback!

geekgonewild

Photowhit said:

In this case it appears 'trailer' means camper/RV. Since NEC isn't involved, I'd suggest moving this to RV's @BB.

@"geekgonewild" Figure out what you need before buying anything more! 

A system that "...mirroring 30 AMP shore connection" will be very hard to put on a RV, even with auto start generator!

Consider 30amps at 120 volts is 3600 watt hours or over 1/3rd of your proposed battery storage.

Bill, Photowhit - thank you for moving the post to the correct forum.

Planning to use full 30amps for Air Conditioning only several hours per day with 2k panels. But, i will review the math just in case. Thank you!

Is it reasonable to ask for cell specs from the manufacturer of all-in-one battery?
Any reputable companies that help with port inspection and/or delivery?

mike95490

The battery company "should" build a battery out of matched cells.   Most do not. Then your warranty is in china, and there is no reason for them to honor it. 
 You should find one with a USA distributor.

  This reminds me so much of the listeroid engines, all the bad parts got put into engines and shipped to the states. 
Sorry - you broke it, it was working when it left here. (with a lb of casting sand in the crankcase)

Photowhit

geekgonewild said:

Is it reasonable to ask for cell specs from the manufacturer of all-in-one battery?

Remember air conditioning on a Solar RV is tricky, because it needs to be in the sun to charge, but with the sun you get solar gain.

It would certainly be correct to ask for the battery bank capacity and specs. 

Please note, many of the inexpensive lithium batteries are intended for stationary use.  I'm not current on design, but a former ot repurposed auto battery might be the way to go, but that pretty much means building the system ground up.

geekgonewild

mike95490 said:

The battery company "should" build a battery out of matched cells.   Most do not. Then your warranty is in china, and there is no reason for them to honor it. 
 You should find one with a USA distributor.

  This reminds me so much of the listeroid engines, all the bad parts got put into engines and shipped to the states. 
Sorry - you broke it, it was working when it left here. (with a lb of casting sand in the crankcase)

Any local, fairly prices distributors you can share or PM me about? Thank you in advance.

geekgonewild

Photowhit said:

geekgonewild said:

Is it reasonable to ask for cell specs from the manufacturer of all-in-one battery?

Remember air conditioning on a Solar RV is tricky, because it needs to be in the sun to charge, but with the sun you get solar gain.

It would certainly be correct to ask for the battery bank capacity and specs. 

Please note, many of the inexpensive lithium batteries are intended for stationary use.  I'm not current on design, but a former ot repurposed auto battery might be the way to go, but that pretty much means building the system ground up.

I agree, i will use air conditioning only when it is sunny.
I will research on how vibrations may affect the lifepo4 batteries performance.
Thank you and kudos for being off-grid solar for 16 years!

mike95490

I've got no pricing or preferences for Li batteries, I'm a NiFe man.

BB.

Are you looking at the 272 AH @ 3.2 volt cell?

If you want 4,000 Watt max:

• 4,000 Watts / 12.4 volts nominal (4x cells in series) = 322 Amps $ 12 volts (>272 amps for 60 seconds max)

So you would need 2x parallel strings of those cells for 4+ kWatts at 12 volts, or at least 24 Volt x 1 string at the higher voltage....

You are looking at 10 kWH @ 48 volt battery bank (LiFePO4):

• 10,000 WH / 49.6 volts nominal = 200 AH battery bank (?)
• 4,000 Watts * 1/0.85 AC inverter eff * 1/42 volts inverter battery cutoff = 112 amps (less than 200 Amp max discharge)

The max current at 10.5 volt @ 12 volt inverter cutoff voltage:

• 4,000 Watts / 10.5 volts = 381 Amps

Your charging current will typically be a maximum of @ 16x3.65=58.4 volts charging (note: No charging below 0C):

• 1,800 Watt array * 0.77 panel+controller derating * 1/(58.4 volts charging) = 23.7 amps typical max (well under 200 Amps)

Say you are in Phoenix AZ in summer, array flat to roof:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Phoenix
Average Solar Insolation figures

Measured in kWh/m2/day onto a horizontal surface:

Jan	Feb	Mar	Apr	May	Jun
3.20	4.07	5.45	6.62	7.37	7.52
Jul	Aug	Sep	Oct	Nov	Dec
6.78	5.97	5.45	4.48	3.50	2.95

The average solar harvest would be:

• 1,800 Watt array * 0.61 off grid AC System eff * 7.0 hours of average sun per summer day = 7,686 WH per day (summer)
• 7,686 WH per day / 3,000 Watt load = 2.6 hours of runtime from solar
• Assuming  using 10kWH battery bank, and 90% to 20% = 70% capacity
• 10,000 WH battery capacity * 0.70 useful capacity * 1/3,000 Watt load = 2.3 Hours of runtime (battery only)

You might revisit the A/C power needs... Modern Mini-splits (inverter-compressor based) can get down below 500 Watts if run at low power (start in morning and keep cool all day long). Actually measuring the A/C load and getting an inverter-compressor based unit (inverter/vfd variable frequency drive) which allows the compressor to run at low(er) speeds and power continuously vs the 100% on / 0% off cycling of the standard A/C units.

RVs are starting to use induction (electric) cook tops on LiFePO4 batteries--But those are usually run at less than 100% power, and for a 1/4 hour--Not like an A/C running >2,000 Watts for hours at a time...

-Bill

geekgonewild

BB. said:

Are you looking at the 272 AH @ 3.2 volt cell?

...

Thank you for that useful information.
I'm building a separate 28.5kwh DIY off-grid system for our cabin based on grade B 280ah lishen cells. But for the travel trailer, I want all-in-one battery since they are cheaper than DYI at that scale when considering tools, materials, time, etc.