mank1234:


They're two methods of connecting solar setup viz grounded and ungrounded system. Gounded is futher classified into positive and negative grounded systems as stated ealier. Grounded here is not same as bonding metal parts. Both methods have advantages and disadvantages.

In grounded system, (let assume the -ve terminal is grounded, touching the positive terminal of a high voltage string can result in tremendous shock since there's a return path through earth. However, such a system is less prone to damage by lightening since there's a ready path to earth to divert the charges. Grounded system is not suitable for transformer less inverter due to the nature of their internal circuitry.

Lightening current traveling through 1m length of wire induces a voltage of 1kV. For ungrounded systems therefore, surge arrester should be ideally installed close to the charge controller to protect it and additionally close to the panel (across the +be and -ve) to ensure that the lightening does not induce voltage above the limits the panels can withstand (most panels can withstand maximum of 1kV).

N/B 1) in grounded system, one terminal is connected to ground at just ONE point, while in ungrounded system no connection to ground is done - the voltage is floating with respect to ground.
2) the fact that your setup has not been hit by lightening since doesn't mean it cannot be hit tomorrow. Precaution is cheaper than replacement

Thanks bro for the input,

Thanks for the enlightenment.Hailings... CC: @ mank1234 @temizeee @bigrovar @life707

One love

durodee:
http://www.solarinsure.com/protect-your-solar-power-system-from-lightning

You can see from the above diagram that it is indicated that the negative from the battery should also be grounded. so I guess one has to research more into this to be sure.
that link is very enlightening (no puns intended) I grounded just the metal frame of my panels before, but I would proceed to get ground copper wire and ground each panel together and connect the output to my ground pole. Thanks

I have a 1.5kva inverter with 2 batteries rated at 200ah each. Presently my batteries are weak but still serves me for like 6 hours when fully charged. I intend buying two more batteries so that I can have two separate battery bank. Now this is my plan: I intend running the weak battery bank during the day time then run the new battery bank at nite. Now my problem is... Can I use one inverter to run the two battery banks separately? I'm trying to avoid a situation where the old battery will be acting as load to the new. Advice from kind hearted readers will be appreciated.

Are you powering a street?

durodee:


I have 2. One with pwm 50amp and another with 60amp mppt.
I have a total of 4.5kw panels of Mono 1.53kw, poly 1.04kw and thin films 2.0kw. Five inverters of one 5kw, two 2.4kw, one 1.4kva and one 800va (my backup ), all pure sine wave. Two 60amp 24v external chargers. Three mppt CCs that are alive and well- one 60amp and two 30amp minus the hybrids.

Still doesn't justifies the cost. How can you buy 1 battery of 12v 200ah for 700k? If you spend that money on buying more panels so that during the day ur ORDINARY deep cycle batteries is discharged 20% max...they will last for 6 years. Choosing what form of energy source to purchase also has cost consideration as a factor. You cannot use a tractor to clear a plot of land.

tivta:


It is a once in a lifetime expenditure, remember the cost of electricity will keep on increasing, I believe anyone who wants to be independent from public power will save to buy it instead of range Rover or parties...

DMerciful:
Still doesn't justifies the cost. How can you buy 1 battery of 12v 200ah for 700k? If you spend that money on buying more panels so that during the day ur ORDINARY deep cycle batteries is discharged 20% max...they will last for 6 years. Choosing what form of energy source to purchase also has cost consideration as a factor. You cannot use a tractor to clear a plot of land.

Like I said, this is a lifetime investment, what guarantee do you have that you would be able to afford changing the battery in 6 years? Remember the battery has 80 percent dod with 11000 recharge cycle. I understand if there is no money to buy it but as long as when can buy range Rover, throw parties etc we should be able to save for a pproduct that will guarantee power for at least 30 years. You even forgot to add the extra cost of charge controllers for the solar panels

Connect the old batteries in 1 string of 24v. Connect the new batteries in another string of 24v. Then parallel these 2 strings to have 24v, 400ah. Then connect to the inverter. This way the inverter charges them same time and saves you the extra work of manually switch to charge. Also because the new ones are stronger, they bear much of the load as it is more difficult for their terminal potential to drop due to load hence they do more work. They old ones won't load the new ones. Its just like a trailer with many tyres, the ones that are more inflated will carry more of the load. Only disadvantage is that it gives you false belief that you have 4 batteries when you have 2.7 batteries per se

obimind:
I have a 1.5kva inverter with 2 batteries rated at 200ah each. Presently my batteries are weak but still serves me for like 6 hours when fully charged. I intend buying two more batteries so that I can have two separate battery bank. Now this is my plan: I intend running the weak battery bank during the day time then run the new battery bank at nite. Now my problem is... Can I use one inverter to run the two battery banks separately? I'm trying to avoid a situation where the old battery will be acting as load to the new. Advice from kind hearted readers will be appreciated.

tivta:

Like I said, this is a lifetime investment, what guarantee do you have that you would be able to afford changing the battery in 6 years? Remember the battery has 80 percent dod with 11000 recharge cycle. I understand if there is no money to buy it but as long as when can buy range Rover, throw parties etc we should be able to save for a pproduct that will guarantee power for at least 30 years. You even forgot to add the extra cost of charge controllers for the solar panels

NAAAH, STILL DOESNT ADD UP...THE TROJAN BATTS ARE RATED FOR 15 TO 20YRS, ....and cost abt 16% of the nickel iron batts.
comparing 120k......20yrs ------------------------------ trojans/us batts
700k.........30yrs and above..................... nickel iron
u can see that trojans carry the day, 2ndly i things change, in 30yrs newer and better batts wud hv been produced/developed, look at the 504/505 of the 70;s
anyway to each his own, this is just an academic exercise, i doubt any1 on this thread would go and buy such batts,,,,considering the price

DMerciful:
Connect the old batteries in 1 string of 24v. Connect the new batteries in another string of 24v. Then parallel these 2 strings to have 24v, 400ah. Then connect to the inverter. This way the inverter charges them same time and saves you the extra work of manually switch to charge. Also because the new ones are stronger, they bear much of the load as it is more difficult for their terminal potential to drop due to load hence they do more work. They old ones won't load the new ones. Its just like a trailer with many tyres, the ones that are more inflated will carry more of the load. Only disadvantage is that it gives you false belief that you have 4 batteries when you have 2.7 batteries per se

with all due respect oga Dmerciful, nothing will kill is battery more. Mixing old (weak) batteries with new one is never advisable not with any connection string.. especially when it is a parallel connection. that is just a no no.

1- Parallel connection are to be avoiding even in the best of conditions its always better to thrive for higher voltage than then to achieve greater current via parallel connection. The problems lies with how hard it is to get the batteries in a parallel setup to having equal charge where you use a bus bar (more money) and ensure the wiring to the batteries are equal, since you can not determine internal resistance of each batteries.. one battery would still get more charge than the other. This would allow

1 the battery with least charge become a load on the stronger battery thus bringing the whole battery setup down.
2. Stronger battery gets over charged during the charging process has it gets full before the other battery in the setup. It will get over charged and over worked while the other batteries get undercharged. In the end the whole bank will fail in less time than estimated.

2. You are mixing strong battery with old one. and putting it in a parallel connection. It is just not the optimal and efficient way to go.

My advise would be that OP first do an audit of his consumption and load. The first thing u do before throwing money at a problem is find out actually what the problem is. In this case the problem is you want regular power. First thing is to do an energy audit. You will find out energy audit is the cheapest activity required when you take the step to solar or inverter.. it is the cheapest and the one that is most likely to save you the most money.

Calculate the load you want to put on your inverter, and how many hours you want them on per day.
e.g I want to have my tv on my inverter. My tv is 70w (you can read the tv power rating or better still buy a watt meter - less than 10k on konga -) and I need it to run for 10 hours

70 * 10 = 700wh

Fan 50w, runs for 10 hours = 500w

in total 700+500 = 1200wh.

in this example 1200wh is what you require from your system (this is just an example) from this figure you will determine how much battery you need.

if you are running a 24v system (which is more efficient.. higher the voltage more efficient) you will divide 1200 by 24

1200/24= 50

50AH is the amount u need. if that is all the load you require, then you can buy a 100 or 150AH battery. this would ensure that you daily use is between the recommended 50% or less depth of discharge to ensure your battery last long and allows you recoup your investment.

Doing an audit also allows you know how much panel u would require to keep your battery at full charge daily because it would make you know how much energy you need to produce to replace what is used everyday.

my 2 cents

Presently I have 4 pieces of 150 watts panel. It has been of so much help to me for the past three months I got it. Thanks to this thread which motivated me to toll this line. There is no regret going solar. In fact I ordered for 2 more panels rated at 150 watts each. It arrived yesterday. By the time it will be mounted I will be having 900 watts of panels above my roof which is very impressive I must say. Thanks to George D, Earthrealm, Abunafiu, Akannaide, Pheleix etc... U guys have been a source of inspiration to me. May God keep blessing u guys.

This is not mixing old and new batteries together and that's d beauty of the string connection. In a series connection, u get higher voltage n higher efficiency from reduced loses due to low current flow however, a weak cell adversely affects the output of the bank. Parallel connection involves higher current n lower voltage hence more loses but the charging is better as each battery is exposed to same charging voltage. The series-parallel combine these unique advantages to give better overall performance. Even if you open the laptop battery, u'll see same series-parallel arrangement. In summary, the analogy I gave with d trailer tyres explains it all. He just need to make sure the old ones are in one string n d new ones in another string.

bigrovar:


with all due respect oga Dmerciful, nothing will kill is battery more. Mixing old (weak) batteries with new one is never advisable not with any connection string.. especially when it is a parallel connection. that is just a no no.

1- Parallel connection are to be avoiding even in the best of conditions its always better to thrive for higher voltage than then to achieve greater current via parallel connection. The problems lies with how hard it is to get the batteries in a parallel setup to having equal charge where you use a bus bar (more money) and ensure the wiring to the batteries are equal, since you can not determine internal resistance of each batteries.. one battery would still get more charge than the other. This would allow

1 the battery with least charge become a load on the stronger battery thus bringing the whole battery setup down.
2. Stronger battery gets over charged during the charging process has it gets full before the other battery in the setup. It will get over charged and over worked while the other batteries get undercharged. In the end the whole bank will fail in less time than estimated.

2. You are mixing strong battery with old one. and putting it in a parallel connection. It is just not the optimal and efficient way to go.

My advise would be that OP first do an audit of his consumption and load. The first thing u do before throwing money at a problem is find out actually what the problem is. In this case the problem is you want regular power. First thing is to do an energy audit. You will find out energy audit is the cheapest activity required when you take the step to solar or inverter.. it is the cheapest and the one that is most likely to save you the most money.

Calculate the load you want to put on your inverter, and how many hours you want them on per day.
e.g I want to have my tv on my inverter. My tv is 70w (you can read the tv power rating or better still buy a watt meter - less than 10k on konga -) and I need it to run for 10 hours

70 * 10 = 700wh

Fan 50w, runs for 10 hours = 500w

in total 700+500 = 1200wh.

in this example 1200wh is what you require from your system (this is just an example) from this figure you will determine how much battery you need.

if you are running a 24v system (which is more efficient.. higher the voltage more efficient) you will divide 1200 by 24

1200/24= 50

50AH is the amount u need. if that is all the load you require, then you can buy a 100 or 150AH battery. this would ensure that you daily use is between the recommended 50% or less depth of discharge to ensure your battery last long and allows you recoup your investment.

Doing an audit also allows you know how much panel u would require to keep your battery at full charge daily because it would make you know how much energy you need to produce to replace what is used everyday.

my 2 cents

Its not as if the battery will charge itself...abi na perpetual motion machine?

tivta:

Like I said, this is a lifetime investment, what guarantee do you have that you would be able to afford changing the battery in 6 years? Remember the battery has 80 percent dod with 11000 recharge cycle. I understand if there is no money to buy it but as long as when can buy range Rover, throw parties etc we should be able to save for a pproduct that will guarantee power for at least 30 years. You even forgot to add the extra cost of charge controllers for the solar panels

DMerciful:
This is not mixing old and new batteries together and that's d beauty of the string connection. In a series connection, u get higher voltage n higher efficiency from reduced loses due to low current flow however, a weak cell adversely affects the output of the bank. Parallel connection involves higher current n lower voltage hence more loses but the charging is better as each battery is exposed to same charging voltage. The series-parallel combine these unique advantages to give better overall performance. Even if you open the laptop battery, u'll see same series-parallel arrangement. In summary, the analogy I gave with d trailer tyres explains it all. He just need to make sure the old ones are in one string n d new ones in another string.

Battery charging process is a function of many parameters whether connected in parallel or series: voltage, current, time and temperature.

In series, same current pass through the old and new batteries and is limited by the old battery due to its higher internal resistance. (The new battery will likely not be affected)

In parallel, the old battery drags the voltage of the newer battery down: this processs involves a sudden discharge of high current (from new bat to old bat) which if done repeatedly tends to reduce the strength of the new battery.

In bank of series and prallel setup, it is more complicated. While some may be undercharging or overcharging. Remember electricity always flows through path of least resistance and in this case newer battery.

It's advisable not to mix batteries of different charge level(ditto old and new batteries)

When you connect the old and new battery together in parallel, the pulling down of the new battery by the old one is just an initial occurrence only and it depends on the state of charge of the old one..there may be no pulling down if they are at same potential. When they say don't mix old and new batteries, its for series arrangement cos the strength of a chain is its weakest link but not in parallel per se. This is not rocket science.

mank1234:


Battery charging process is a function of many parameters whether connected in parallel or series: voltage, current, time and temperature.

In series, same current pass through the old and new batteries and is limited by the old battery due to its higher internal resistance. (The new battery will likely not be affected)

In parallel, the old battery drags the voltage of the newer battery down: this processs involves a sudden discharge of high current (from new bat to old bat) which if done repeatedly tends to reduce the strength of the new battery.

In bank of series and prallel setup, it is more complicated. While some may be undercharging or overcharging. Remember electricity always flows through path of least resistance and in this case newer battery.

It's advisable not to mix batteries of different charge level(ditto old and new batteries)

earthrealm:


NAAAH, STILL DOESNT ADD UP...THE TROJAN BATTS ARE RATED FOR 15 TO 20YRS, ....and cost abt 16% of the nickel iron batts.
comparing 120k......20yrs ------------------------------ trojans/us batts
700k.........30yrs and above..................... nickel iron
u can see that trojans carry the day, 2ndly i things change, in 30yrs newer and better batts wud hv been produced/developed, look at the 504/505 of the 70;s
anyway to each his own, this is just an academic exercise, i doubt any1 on this thread would go and buy such batts,,,,considering the price

A little point of correction: trojan deep cycle flooded cells are rated to 15 to 20 yrs float service and not for regular cycle service. The best cycle service you can get is from the industrial brands at about 2800 cycles at 50% DOD. Float service is like UPS type application where the battery is cycled a few times in a year.

Nickel iron 2 major drawbacks are: One, excessive gassing during charging, which means you will have to be topping up regularly with special alkaline electrolyte. And two, it has an inherent high internal resistance. This causes voltage sags whenever high current is being drawn from it. The voltage sags can be cushioned with super capacitors connected in parallel to them.

DMerciful:
When you connect the old and new battery together in parallel, the pulling down of the new battery by the old one is just an initial occurrence only and it depends on the state of charge of the old one..there may be no pulling down if they are at same potential. When they say don't mix old and new batteries, its for series arrangement cos the strength of a chain is its weakest link but not in parallel per se. This is not rocket science.

That's not entirely true. If you've a 12V battery of which say 2 cell are dead, it will be never charge up to 12V. If connected in parallel with healthy battery, the setup will appear to be optimmaly charged at full charge but as soon as the charging source is removed, the voltage of the setup will reduce to below 12V. The dead cells will slowly convert the excess energy of the other batteries to heat till it reaches it settling voltage. It will pull it down all the time.

Try this with a dead battery/ new battery and you'll agree to my proposition. Charge them fully, remove the charging source and load and watch what happens within 1hr.

Rocket science!

Let's not go to the extreme here. The op said he can get up to 6hours currently from the batteries but wants to buy more meaning the batteries are not that bad! You make it seems as if we are talking about a battery that is behaving like a capacitor .

mank1234:


That's not entirely true. If you've a 12V battery of which say 2 cell are dead, it will be never charge up to 12V. If connected in parallel with healthy battery, the setup will appear to be optimmaly charged at full charge but as soon as the charging source is removed, the voltage of the setup will reduce to below 12V. The dead cells will slowly convert the excess energy of the other batteries to heat till it reaches it settling voltage. It will pull it down all the time.

Try this with a dead battery/ new battery and you'll agree to my proposition. Charge them fully, remove the charging source and load and watch what happens within 1hr.

Rocket science!

@bigrover, I do appreciate u for the detailed explanation.

Lively thread.. just passing through. Una well done o

DMerciful:
Let's not go to the extreme here. The op said he can get up to 6hours currently from the batteries but wants to buy more meaning the batteries are not that bad! You make it seems as if we are talking about a battery that is behaving like a capacitor .

Brother, u to do more research on this. You don't mix weak batteries with stronger ones. Don't matter is the battery ain't dead has long has the internal resistance are not the same don't mix them. In fact it is not recommended to mix new batteries in parallel (unless you have no choice ) parallel connection can already be inefficient as is than to then be mixing old and new batteries together. Making it series parallel won't solve the problem of the weaker batteries dragging down the healthier ones.

The op needs to do his load audit. Other wise what became of the old batteries will after the new. Batteries that can't serve you for 3 years defeats the cost savings of using inverter or going solar.

@bigrover, d merciful & mank1234...u guys are wonderful. Sincerely I've learnt a lot from u guys. Now that it been made clear to me to avoid mixing the old and new batteries in parallel, what do u advice me to do with my weak batteries which can last for 6 hours when fully charged?

I am looking forward to getting two new 200ah batteries which will be a sperate battery bank of 24v. I intend running the weak battery during the day time which will be powered by my panel which is 600watts presently...then switch to the new batteries at nite which will also be charged by solar during the day. I want to go off grid and also avoid turning my generator which runs between 3 to 4 hours every evening on a daily basis. Note when I add my 2 pieces of 150 watts on my roof I'll be having 900 watts of panels. Can I use one inverter to switch between the old and new battery bank conveniently?

gentlemen, it is right to connect my inverter DC inlet to the Load connection point of my MPPT charge controller ?
a colleague in the Office (a certified EE) has insisted that is the correct method of connecting both the inverter, solar and Disco power as it would enable the charge controller serve as a switch and as well regulate the current at which i charge my batteries.

that this : Solar PV to the solar PV input on the CC as usual, Batteries would be connected to the Battery input on the CC as usual, inverter DC cables would be connected to the Loads outlet of the CC .while the AC inlet of the inverter for charging would be connected and powered on.
His point been that the CC would switch between DC sources for charging the batteries as well regulate the SOC of the batteries to my preferred cut off point.
(solar to cc, battery to cc, inverter dc to cc loads, inverter AC input to AC mains for charging, inverter AC outlet to my desired inverter powered devices) vs ( solar pv to cc, battery to cc, Inverter DC to batteries, and the inverter AC IO would be same). Can the CC load point also serve as a DC input to the CC to charge the batteries as well ? the Charge controller here is an EPsolar 40 A.

please comment.

@ all, deep cycle batteries and gel batteries which one is better in terms of being rugged and surviving deep discharge over time? Pls opinions are highly welcome. Thanks!

@blazeup: may I ask what is 'CC'? Do you have a drawing of your setup? Can you share with us?

iLoveTheSun:
@blazeup: may I ask what is 'CC'? Do you have a drawing of your setup? Can you share with us?

'CC' is charge controller. cant draw it now and i have not seen any drawing on the net yet.

ah, thanks! I call it the 'solar charge controller';-)

Back to your question:
Yes, for small off-grid solar installation, the solar charge controller will pass through all current.

See the pic. below of a low-cost Chinese product.

blazeup:
gentlemen, it is right to connect my inverter DC inlet to the Load connection point of my MPPT charge controller ?
a colleague in the Office (a certified EE) has insisted that is the correct method of connecting both the inverter, solar and Disco power as it would enable the charge controller serve as a switch and as well regulate the current at which i charge my batteries.

that this : Solar PV to the solar PV input on the CC as usual, Batteries would be connected to the Battery input on the CC as usual, inverter DC cables would be connected to the Loads outlet of the CC .while the AC inlet of the inverter for charging would be connected and powered on.
His point been that the CC would switch between DC sources for charging the batteries as well regulate the SOC of the batteries to my preferred cut off point.
(solar to cc, battery to cc, inverter dc to cc loads, inverter AC input to AC mains for charging, inverter AC outlet to my desired inverter powered devices) vs ( solar pv to cc, battery to cc, Inverter DC to batteries, and the inverter AC IO would be same). Can the CC load point also serve as a DC input to the CC to charge the batteries as well ? the Charge controller here is an EPsolar 40 A.

please comment.

You will damage the charge controller. Do not connect the inverter to the load section of your controller. You can connect small load there ( like a 3w led bulb). Run from your panel to charge controller, charge controller to battery and battery to inverter.

@obimind:
Obviously 'deep cycle' describes the purpose of the battery: typical applications are UPS (in a stable grid environment where there is always light) or fisher boat (normally the engines powers a generator when on sea), so there are only view failures per year. Normally current of discharge is high. Let's say, it is used for 15 minutes, when a genset kicks in in a UPS application. It shortens the life cycle anyway, but the number of cycles is little in this case. => not suitable for every day charging and discharging!

'Gel' battery describe the built of the battery. Normally gel is put in glass matt in VRLA (closed Valve Regulated Lead Acid) battery. It is for "slow" charging and discharging without producing too much gas. It is more "gentle" to the materials inside the battery.

In general, to boost life cycle you should charge or discharge over a long time period, like 10hours (=c 10) or better 20 hours (=c 20).
I will look for a chart and post it here. The faster you charge/discharge, the shorter the life cycle is.

What I have read here, many people charge during the day and discharge the same evening.

One more factor is the depth of discharge (DOD). A battery that is only discharged to 80% of its capacity has a much longer life than a battery with DOD=50%.

So I have the feeling that people undersize their battery capacity.

My recommendation: when you have the feeling you have the right battery capacity, simply double it, then you will be on the right side.

sunny regards,

@anochusk08:
I agree, for big loads, different set up is required. I don't know the brand of the solar charge controller or the inverter.

But definitely, you should take the ambient temperature into consideration. Often tests for the name/type plate is done in a lab.

Let's say, the solar charge controller can manage up to 30 Amps, then I would run with -20% of Amps, e.g. max. 24 Amps.
If it is a quality product, then I wouldn't mind. But with low-budget products I would be careful. Otherwise you will burn it.

Beyond 40 Amps, load is connected directly to the battery, and an additional battery management product with a shunt is deployed.
At least in commercial applications. So that the state of battery is well monitored.

Oh, and don't forget to put breakers and the right fuses. With 40 Amps you could weld metal!