Changing from 12v battery bank(8 Batteries) to 24v. How to wire them?

[SunEagle]

I hoped you're not taking that as the wrong way...I would be dammed proud to be called a "Fanatic." The fact that you folks stick around long enough and stacked up all them posts to help others (or not) is commendable and ought to get paid for or some kinda bonuses.

Well thank you for the kind words. I spend my time here with the intentions of helping others not make the same costly mistakes I made and to better understand solar technology.

My comments are totally free of charge and hopefully helpful.

But as J.P.M. states, take what you want and scrap the rest.

[lkruper]

Well thank you for the kind words. I spend my time here with the intentions of helping others not make the same costly mistakes I made and to better understand solar technology.

My comments are totally free of charge and hopefully helpful.

But as J.P.M. states, take what you want and scrap the rest.

I thought we got an automatic 10% discount from the sponsors site!

[Uli]

Hi there. I need a bit of help here i have 8 batteries at 12v 130amp each i need a 24v system so i connected 2 batteries in series so i have 4 groups in series of 24v 130amp and then i connected the 4 groups of batteries in series which it gives me a 24v 520amp battery bank. But the question is:
if i make to group of batteries at 12v 520amp by connect 4 batteries in paralel first and then connect them in series so it should give me 24v 1040amps. So the question is which is the best connection to do?
thanks for any suggestions.

[Uli]

ay, 02:12 PM
Hi there. I need a bit of help here i have 8 batteries at 12v 130amp each i need a 24v system so i connected 2 batteries in series so i have 4 groups in series of 24v 130amp and then i connected the 4 groups of batteries in series which it gives me a 24v 520amp battery bank. But the question is:
if i make to group of batteries at 12v 520amp by connect 4 batteries in paralel first and then connect them in series so it should give me 24v 1040amps. So the question is which is the best connection to do?
thanks for any suggestions.

[Sunking]

Uli it does not work like that. You wire the batteries 2S4P which will give you 24 volts @ 520 AH.

Series Law: Voltage and Power adds, Current remains equal
Parallel Law: Current and Power adds, Voltage remains equal.

2 in series = 24 volts, 4 x 130 AH in parallel = 520 AH

Proof: Each battery is 12 volts x 130 AH = 1560 Watt Hours. You have 8 batteries and power adds. 8 x 1560 AH = 12480 Watt Hours.

12 volts x 1040 AH = 12480 Watt Hours. All 8 batteries in in parallel or 8P
24 volts x 520 AH = 12480 Watt Hours. 2 in series and 4 in parallel or 2S4P
48 volts x 260 AH = 12480 Wat Hours. 4 in series and 2 in parallel or 4S2P
96 volts x 130 AH = 12480 Watt Hours, 8 in series 8S

No matter how you spin your 8 batteries you have 12480 Watt Hours. Simple math. Like having $100. Does not matter if it is a single $100 bill, stack of 5 x $20 bills, stack of 100 x $1 bills, or a stack of 10,000 pennies, it is still $100.

No where is the hard lesson you will soon learn. If those were 6-volt 520 AH batteries wired 4S for 24 volts @ 520 AH would last 2 to 3 times longer than your 8 x 12 volt batteries. Ouch! Hard lesson to learn. Remember that when replacement time comes. That is when it is like counting money.

[Uli]

Hi Sunking.
thanks for your tips. Ill make a treasure of it. And yes next time will get a low voltage of batteties. I just hope they will last me at least 3 to 4 years these ones??

[hankuru5ki]

Hi there Uli,
Batteries connected in SERIES = increased the voltage but amperage remain the same, as in, 2X12Volts 130Amp in series = 24Volts 130Amp.
So 4 (groups of 12V 130Amp in series) X 24 volts 130Amp in PARALLEL = 24V 520Amp (as in 130Amp X 4 = 520Amps). But 520Amp is different from amperage-hour (Ah @ C20) which may yield ONLY 60% usable power is 7488Watts before auto-shutoff/charging.
You have to be sure what is the rating of the batteries in Amperage-hour (Ah).
You can help yourself to reconsider 6Volts batteries with a better capacity storage handling as well as three maximum (in my opinion) groups in parallel instead of 4X groups in parallel. The 6V batteries is bulkier so they will require a two to three times larger than you would need for 12V deep cycle batteries. Personally, I have Trojan L16RE-B group of 4 in SERIES to yield 24V 370Ah = 8880Watts, BUT usable wattage is ONLY 60% which is 5328Watts before my Samlex Inverter/Charger EVO-4024 switched from being the inverter to the charger and charge the batteries and supply the load at the same time. Trojan L16RE-B has a warranty of 60 months instead of some the 12V batteries ranging from 24--36 months which can be troublesome in replacement every 2-3 years.
Batteries connected in PARALLEL = increased the Amperage but the Voltage remain the same, as in, THREE (ONLY) of 12V 130Amp in PARALLEL = 12V 390Amp with a 60% usable of 234Watts before require recharging.
It would be helpful to figure out what you NEED to supply your load.
12Volt batteries is the LEAST DESIRABLE power storage to be considered, perhaps you should look into the Trojan J200-RE = 12V 200Ah @ C20 to make simpler connection, as in, THREE in PARALLEL to yield 12V 600Ah compare to TWO groups of TWO L16RE-B in SERIES to yield 12V 740Ah. However THREE J200-RE will costs more than FOUR L16RE-B, so something to be considered.
Your system is based on your INVERTER's capability as in 12V (only), or self-sensing 12V & 24V (only), or 48V (only), or so on and so on. Which means everything must be built according to the INVERTER's based voltage.
IF THE LOAD REQUIRES MORE THAN 1000W PLEASE CONSIDER TO USE 4-0 (welding cable for easy installation) TO MAKE YOUR CONNECTIONS FROM BATTERIES TO INVERTER. "DON'T BE CHEAP" you will pay for that guarantee.
Lastly, your charge controller and the solar panels must be balanced and well within their handling capabilities.
Happy trail my friend!

[Uli]

Hi Hankuru5ki.
thank you for your suggestions and ill def. Keep in mind for next time when my batteries will abandon me. So i am giving you a quick list of what i have.
4 monocrystalline 250w 60 cells a 40amp mppt 8 batteries 12v 130amps and a 2500watt 24v inverter plus 20amps charger and i would like to run all my LED lights at 5watts each which are about 25 of them but obviously not at the same time. 2 tv of 40 inches a kettle a toster a ridge freezer and any other small appliences. The only item that is constantly on is the fridge but its rated A+++ of energy. Do you think i can manage to make it work without frying the batteries or any other compones of my DIY solar system?

many thanks
again
ulisse

[hankuru5ki]

Assuming 4panelsX250W is producing a nominal 1000W (remember not at constantly, they are depending on the sun conditions), however at ludicrous super clear sun condition it could yield 10% extra so the high spike of power can be as high as 1100W divide that into 24V MPPT charger controller yields 45.83 Amps which is pretty much out of tolerance for your 40amp MPPT (I am also assuming that this is a self-sensing voltage upto 150VDC? If it is NOT you need to work this problem out, MidNite Classics 150 is what I have and it can handle 92Amps at 12VDC; MidNite solar website also has a wonderful calculator to aid you in choosing the right charge controller and how many solar panels for each cc).
Inverter comes in all sizes and types, especially, when it deals with TVs & Radios = it is best to go with PURE SINE and not "modified", otherwise they will HUM.
Kettle and toaster are power sucking devices and must be dealt gingerly because they are are ranging from 1500W to 1800W with your 2500W 24V inverter of LOW or HIGH Frequency? It is best with LOW frequency type of inverter because it consumes less operating power especially with the internal cooling fan runs only as necessary, whereas the high freq constantly running whether the load applied or not which will drain your power.
The fridge is a serious concern of starting power, meaning it starts at very high power 1 1/2 times the nominal power consumption, which could cause an overload condition to the 2500W inverter with other lighting items running. 2500W inverter meaning everything must be within 2500Watt and preferrably total load at any given time of not more than 2000Watts. You can start with the total power consumption of the fridge over the period of 24 hours to see if you have enough power in the batteries to run it and then with the extra power you can calculate which other appliances can be used. 2500W is workable but not ideally.
Solar power is to size it 2.5 times extra, and for kettle or toaster would be best to be used during peak sun hours instead of on demand say at night (kinda defeat the purpose of using solar power in the first place). We do all of our laundry, baking, vacuum cleaning, and other chores from 10am through 1pm and that also depends greatly on sun conditions. From 1pm to sunset reserve for fridge and normal batteries charging for the night through the morning. Samlex EVO-4024 is a wonderful device which it will switch to grid-charging to the batteries during the early morning hours whenever the battery power depleted (meaning when it drops below 40%), take a look into that for the "next time".
Using two chargers at the same time to charge the single battery-bank (8 x 12v130A in SERIES-PARALLEL) is tricky BECAUSE it deals with balancing the charging load as well as to each individual battery and it is something out of my league.
If you ask McGyver he would say yes! But for the long run, I don't think I can jam this paper clip "to make it work without frying the batteries or any other components of your DIY solar system."

[Uli]

Hi hankuru5ki.
thanks again for your tips i guess i will try out and adjust things how im going along until wil find the right balance.

thank you very much
for sharing your knowledge
ulisse