battery bank

robocop

hi guys

I have read through internet.

If I have 2 batt  12v/100ah connected in series and  connected 2 other batt same in series 12v/100ah

and then connect those 2 sets of  together in parallel  result in 24v/200ah.

Is that true?  

BB.

Yes. That is correct.

-Bill

robocop

ok BB  so to get  48v/ 400ah do I have to do the same  with other 4 batteries and then connect each four in parrallel?

robocop

BB  I meant  each group pf 4 batt

Raj174

Hi robocop,
The way to get a 48 volt battery bank with 12 volt 100 amp hour batteries is to wire them 4 in series to get 1 string at 48V 100AH. Parallel strings together to increase amp hours. However, putting more than 2 strings together should be avoided because it becomes difficult to keep the strings in balance. For larger battery banks we use lower voltage, higher amp hour batteries. Check out this website for general information on batteries.

http://batteryuniversity.com/

Rick

robocop

Hi Bill  plse leave you to your opinion about my 2nd questions appreciate thx

robocop

If I have 2 batt  12v/100ah connected in series and  connected 2 other batt same in series 12v/100ah

and then connect those 2 sets of  together in parallel  result in 24v/200ah.

Hi Rick why not like this?

robocop

This is one string or not?????

ramloui

4 x 12V in series is 48V 100Ah.

Take 4 of these strings and connect them parallel and you get 4 x 100Ah=400Ah at 48V.

Series connections: voltage adds up

Parallel connections: Amps add up

Cheers.

Louis R.

Raj174

robocop,
I agree with Louis R. above, and couldn't say it any better. This graphic may help:



Edit : As other members have pointed out, this diagram is only to exemplify series and parallel battery connections for basic understanding and not to be used as examples for cabling installations. 
  
Rick

mcgivor

From a graphical  standpoint of explanation is correct , however when connecting a load or charging system, the connections to the battery would be made diagonally opposite in a parallel situation, to better ballance  the charge and discharge thereof, after all batteries are not connected together to do nothing but provide a voltage, they are charged and discharged. Just some minor details should @robocop decide to go the parallel route.

BB.

Here is a link about connecting multiple strings of batteries for "even" discharge among the strings:

http://www.smartgauge.co.uk/batt_con.html

So, the above folks are correct about the basic electrical connections that add voltage (in series) and add Amps/Amp*Hours in parallel.

The details about choosing between parallel and series connections and larger Amp*Hour rated cells--There are lots of details.

The main reasons I do not "like" a bunch of 12 volt batteries for a 12 volt battery bank:

• First, wire like the Smartgauge link above, Rick's (Raj124) post is correct electrically, but physically you want to "balance" the wiring resistance.
• When measuring voltage of the battery bank, you cannot "see" the voltage (and health of each battery)--They are all paralleled together. With reasonably priced DC Current Clamp DMM (Sears), you can measure the current into/out of each battery--Makes things a bit easier.
• More cells to check water levels on. You can have 4x 6 cell (12 volt batteries) @ 100 AH, or 2x 3 cell (6 volt @ 400 AH) batteries in series.
• Fewer wiring connections.
  
• In theory, when you have ~3 or more parallel strings of batteries, you should have a breaker/fuse per string to lessen the chances of a short circuit on a large parallel battery bank causing the wiring to overheat and catch fire (somebody drops a wrench into the battery bank, shorted cell, etc.).
• Secondary issues--Each cell can fail/age/vary in capacity/voltage from the rest of the cells in the bank. Just more things to fail, if you have variations in temperature between cells, charging / ouptut voltages vary, etc.

Smaller cell (AH rating) batteries have less life (it seems). We have had people try to put a bunch of random 12 volt "car/marine" batteries in parallel, or a bunch of 35 AH @ 12 volt batteries into parallel/series banks.

When you have a lot of batteries in a bank, you will eventually have to find bad batteries and replace them. And after a couple of failed, then think about replacing the entire battery bank or chasing battery/cell failures for months/years into the future.

Also, when picking batteries--You have to figure out how big a battery you can handle at your place. A 12 volt @ 100 AH is about the same size/weight as a 6 volt @ 200 AH (3x cell) or 2 volt @ 600 AH (1x cell). They each store the same amount of energy (E=V*AH rating). You just have to series them into the bank voltage you want (batteries are just cells put in series--12 volts--6x cells in series without the external wiring).

You can get heavier batteries (or even cells) that weigh >300 lbs. Or fork lift batteries that weigh >1,000 lbs. Then you need to figure out how to get it off the truck and into the battery shed (steps, concrete floor/driveway, crane, pallet jack, etc.).

In general, even for a small system, 2x 6 volt @ ~200 AH golf cart batteries make a really nice starter set. They are relatively cheap (~$80-$100). Will last 3-5 years, and if something happens (many people "murder" their first battery bank), you are not out much money.

2x series GC to 2 series x 2 parallel GC batteries make a really nice starter bank. 2s GG batteries are 12 volt @ 200 AH or 2sx2p is 12 volts @ 400 AH.

A 4 battery bank of GC batteries will give you (using our off grid system rules of thumbs):

• 12 volts * 400 AH * 0.85 AC inverter eff * 1/20 hour discharge = 204 Watt (120 VAC) average load
• 204 Watts * 5 hours a night * 2 nights = 2,040 WH for two nights (50% maximum battery discharge for longer life)
• 12 volts * 400 AH * 0.85 invt eff * 1/8 hour discharge rate = ~510 Watt maximum continuous AC load (~4 hours to 50% State of charge)
• 12 volts * 400 AH * 0.85 invt eff * 1/5 hour discharge rate = 816 Watt max AC load (minutes to 1 hour or so)
  
• 12 volts * 400 AH * 0.85 invt eff * 1/2.5 hour discharge rate = 1,632 Watt max AC surge (seconds to start well pump, etc.)
  

More or less, that makes a 300 watt (typical) to 800 Watt max AC inverter "cost effective" for this configuration. A 300 Watt Morningstar 12 volt TSW AC inverter is really nice for this bank (plus the Morningstar has remote on/off, and low power "search" mode).

To charge such a battery bank--Two sets of calculations. The first is sizing the solar array to the battery bank (larger battery bank needs more solar power for proper charging). 5% rate of charge is OK for weekend/seasonal usage. 10%-13% is better for full time off grid usage:

• 400 AH * 14.5 volts charging * 1/0.77 panel+charger derating * 0.05 rate of charge = 377 Watt array minimum
  
• 400 AH * 14.5 volts charging * 1/0.77 panel+charger derating * 0.10 rate of charge = 753 Watt array nominal
  
• 400 AH * 14.5 volts charging * 1/0.77 panel+charger derating * 0.13 rate of charge = 979 Watt array "cost effective" maximum

And then there is sizing the array based on your daily loads and average hours of sun per day.

• 400 AH * 12 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 1,020 WH per day

Say installed fixed array near Palm Beach Florida:
http://www.solarelectricityhandbook.com/solar-irradiance.html

West Palm Beach
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 63° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
4.46	5.14	5.53	5.82	5.63	4.87
Jul	Aug	Sep	Oct	Nov	Dec
4.92	4.91	4.71	4.98	4.52	4.30

If you want to run the system during bad weather--The minimum average sun is December--Lets say 4.0 hours of sun (average) per day (still a lot of sun for most people):

• 1,020 WH per day * 1/0.52 AC off grid system eff * 1/4.0 hours of sun per day = 490 Watt "break even" solar array

So, I would suggest a 490 Watt to 753 Watt array for a nice/capable system to learn on. The system is a bit small for running a standard full size Energy Star rated refrigerator (need ~1,200 Watt inverter minimum, and 6-8 GC batteries in series/parallel). Or a larger 24 volt system with 4sx3p GC batteries (24 volt at ~600 AH) would give you ~3,300 WH per day (fridge, lighting, radio, small water pump, laptop computer) and a ~3.3x larger solar array.

Anyway--Suggesting to not focus on the battery bank until you have a good handle on the loads and what you want/need the system to do.

-Bill

robocop

hi guy this difficult but can Iet 48v/400ah with 4 batteries I think with 8 batteries I can.

Or it is better with 24v/400ah? 

BB.

48v/400ah has 2x the energy capacity of a 24v/400ah battery bank.

Finding 48 volt rated breakers & inverters is a little bit more difficult. But sizing the battery bank voltage+ah is based on your needs. 48 volt systems tend to be bigger (more powerful).

Solar systems are not cheap. You want to design+build one that is the right size for your needs. Too small or oversized, each has their downsides.

-Bill

robocop

for you guys I wish i could be that far in knowledge of this solar matter

I begin to catch it     I cannot get 48v/400ah with four batteries

or it should be batteries of 400ah each

shold be like this : 4x 12v/200ah  in series gives  48v/200ah take 2  strings of them connected  as parrallel will give me 48v/400ah. so 8 batteries total

ok plse just make calculation for me  , if i do have airco working that take 3000w.

How many hours of energy can I get from the batteries ?

I think that at last I begin to catch  this matter. so v xA  = watts (48x400 =19200 wh)

So I do have more than 6 hrs of energy?  

blessing for you all

mcgivor

robocop said:

for you guys I wish i could be that far in knowledge of this solar matter

I begin to catch it     I cannot get 48v/400ah with four batteries

or it should be batteries of 400ah each

shold be like this : 4x 12v/200ah  in series gives  48v/200ah take 2  strings of them connected  as parrallel will give me 48v/400ah. so 8 batteries total

ok plse just make calculation for me  , if i do have airco working that take 3000w.

How many hours of energy can I get from the batteries ?

I think that at last I begin to catch  this matter. so v xA  = watts (48x400 =19200 wh)

So I do have more than 6 hrs of energy?  

blessing for you all

You got the battery calculations correct, in reality you would look at the capacity as 9600 Wh, so as not to discharge below 50% on a regular basis. Air conditioning is not a simple calculation, it depends on various factors including setpoint, ambient outdoor temperature, insulation of the cooled space and location of the unit, so almost impossible to predict with any degree of accuracy. Assuming a 100% duty cycle three would be approximately 3 hours of battery capacity, beyond that it is speculation.

BB.

You can get larger 12 volt batteries... Here is a fork lift battery:

https://www.solar-electric.com/crinba6.html

• 12 Volts
• 530 Amp-hours at the 20 hour rate
• Dimensions: 18.88"L x 8.88"W x 23.25"H
• Weight: 465 pounds
• Warranty: 1500 cycles to 80% DOD for five years full replacement.
• $1,840
  

What is possible vs what is practicable for you is always the question.

-Bill

robocop

  Hi BB and Rick and others

Was thinking , Is not better instead of the 8 batteries 12v/200ah  to get 48v/400ah to buy  24 pcs of 2v/200ah  toget same 48v/400ah , first 12 pcs string in series and then parrallel .

I think I need more batt about 48 batt ?

Better of 24 pcs inseries thus 24 x2v/800ah batteries  maybe it will be cheaper.

next if one cel fail in the 12v batteries has to rteplace whole 12v battey but in the 2 v case only one portions thus one 2v batt.

dont you see guys I am beginning to catch up  

BB.

Note that a 12 volt @ 100 AH is about the same size/weight as a 6 volt @ 200 AH or a 2 volt @ 600 AH cell. They all store the same amount of energy. Obviously, you have to put the lower voltage cells in series to match 12 volts... But you would have a "larger AH" rated 12 volt battery bank if you did that.

Costs--You have to do a paper design and see what works best for you. Some batteries (types, brands) are more expensive than others. Also, high volume batteries (like 6 volt @ 200 AH Golf Cart batteries) are cheaper than lower volume (and perhaps better quality 6 volt @ 200 AH batteries from other vendors).

And, you have to add the cost of cabling, moving batteries to site (heavy batteries, you may need a mechanical lift/crane to pick and place).

I am still confused... What are your basic energy and power requirements for the battery bank? Do you have limits on size/weight of cells/batteries/battery bank? Would you want a bank that lasts 3-5 years or pay 2x as much for a bank that would last 5-7 years, or what?

Any temperature issues (hot/cold)?

-Bill

robocop

thnks BB  will have airco of about nominal 2900w working for about 4 hrs at least per day . live time of battery 7-10 yrs is ok

temperature is tropics 30-36 C  inverter 48vdc output 220v 4000w constant  21A output.

I am concerned about how many panels to charge the batteries thonking about or 290w -300w or 325w each panel

awating thx   Robert

Raj174

What is the make and model number of the air conditioner you are considering? 2900 watts is a lot of power. Running wattage on  a 24000 BTU unit would be around 3000 watts and a 4000 watt inverter would not be able to start it unless it was an inverter type A/C unit. 

Rick

BB.

Robert, where (roughly, nearest major city) will the system be installed? (figuring out how much sun you get)

Also, running at battery bank at ~35C, the batteries will last about 1/2 as long as batteries running at 25C... The only batteries (I think) that would last that long would be fork lift batteries or some other Lithium chemistry battery (and that chemistry is still a bit "cutting edge" also known as "bleeding edge" for a first time off grid).

• 2,900 Watts * 5 hours per day * 1/0.85 inverter eff * 1/48 volt battery bank * 2 days storage * 1/0.50 max discharge = 1,422 AH @ 48 volt battery bank

Typical 10% rate of charge for an off grid power system:

• 1,422 AH * 59 volts charging * 1/0.77 solar panel + charger deratings * 0.10 rate of charge = 10,896 Watt solar array "nominal"

Minimum average hours of sun needed to keep system "happy":

• 2,900 Watts * 5 hours * 1/0.52 off grid system eff * 1/10,896 Watt array = 2.6 Hours of sun minimum per day

Conceivably, if you run the AC system only during the middle of the day and not at night/during bad weather, you could possibly get away with a 1/2 size battery bank (711 AH @ 48 volts) and a ~5,500 Watt solar array (depending on where the system will be installed).

That is a lot of solar power (large load). And a fair amount of risks--You need to have "free cash" available--There may be some mistakes along the way. Do not spend all of your savings on such a system.

One thing you could do--Run a genset + your AC system for a few days with a Watt*Hour meter and measure how much energy you really will be using.

-Bill

robocop

for RICK.  it is for a 9000 btu inverter and a 24000btu inverter air conditioner for 3-4 hrs a day.

so then charge the batt up for the next day for another 4 hrs and so on.

inverter is  pure sine solar hybrid inverter input 48vdc continuous 500va/4000w continioius out about 21ampere and 220v  both will take about 2900 w

robocop

sorry Rick this is Curacao   at the coast of venezuela

Raj174

Hi Robert,
What is the manufacturer and model of the 4000 watt hybrid inverter and will it be connected to the grid. If so is the grid dependable. Probably getting expensive. I know things are difficult economically in Venezuela these days, I hope not so much where you are.  BB should be along to help with the numbers, quite amazing, isn't he.
Thanks,
Rick

robocop

Hi Rick  no we are part of Netherlands not venezuela lucky for us , it is very sad what is going on there.

robocop

PH1800 MPK Plus MPPT Series (1-5KVA)     4000w  so it will easy handle about 3000w. I can use grid too with this inverter.Sure  BB is amazing with numbers .You are helping me a lot too . Trying to understand this field,God Bless you all 

Raj174

Thanks for the information Robert,

Bill, this is the spec sheet on the hybrid inverter charger/MPPT charge controller the OP will be using. It is the 5000VA/4000 watt model. Looks like it will handle the load, however the spec sheet states "Battery over charge protection 60 volts". This may be a problem for FLA batteries. 

robocop

thnks for your info but what should the overcharge be having a 48v battery bank?

Raj174

Flooded Lead Acid batteries (FLA) require an Equalizing charge (EQ) periodically at voltages up to 64 volts. The battery over charge protection of your all in one inverter is 60 volts and does not appear to be adjustable. You might check that out if you have the manual. AGM batteries might be the only choice in a lead acid battery. These batteries are sealed and a bit more difficult to determine battery state of charge (SOC) and health. They have advantages also. 

Rick

robocop

So with this inverter I can use AGM batteries but what about the gel batteries? Ok then but in 48v in panels  how many solar panels do I need to charge these batteries let say 8batteries of 250ah forming a bank of 500ah batt 12v .