Newby from South Africa

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Hi Everyone,

I have just joined this Forum, and hope to learn a lot from you friendly folks :D

Firstly, let me apologize in advance for my use of the English language, as it is not my native language :blush:

Now, to start, here is some background...

I have been running a Studer XP-Compact 2.2 kVA inverter, coupled to four CSB TPL121600, 160Ah VRLA (AGM) batteries (in series/parallel, to give my 320Ah at 24V), as an "emergency standby" system for some years now, as our national electricity supply is pretty unreliable. I've wired a separate "un-interruptible" circuit in my house, supplying all my house lights, my computer, and (most importantly to me) a fridge and my marine aquarium from the inverter (through proper circuit breakers and earth leakage protection). The inverter is normally powered by our municipal mains supply (i.e. grid) through a transfer switch, and trickle charges the batteries whilst running the above circuits on "mains" power. In the event of a power failure, the transfer switch decouples the mains supply, and switches the inverter to battery supply.

The batteries discharge at approximately 0.05C with only the aquarium drawing current (measured current of 14A @ 24V, at the battery), and at 0.14C with all appliances drawing current (46A @ 24V). If my calculations are correct, this gives me close to 20 hours backup with only the aquarium drawing current, and about 5 hours at full load (discharging to 20.8V, or approximately 60% depth of discharge).

I am now considering installing some PV panels to either take this circuit "off grid" completely (with additional batteries added as well), or to just expand the "window of backup power" with the panels charging the batteries during the day, whilst they are supplying the inverter with power . The reason that I'm considering the latter option very seriously, is that both PV panels and deep discharge batteries are VERY expensive here in South Africa, and that upgrading to a totally "off grid" system would be prohibitively expensive, even for such a small system.

Questions:

1. Would it be practical / possible to have some PV panels (say, supplying 10A at 24V) hooked up to the batteries whilst the system is in "normal" standby mode (being powered from the grid, and thus trickle charging the batteries from the inverter)? Would this not confuse the charge controllers of the inverter and the PV panels? Also, how would one limit the current from the PV panels to not over-charge the batteries (which are normally only "idling" at full charge)?

2. If not, would it be feasible to install a N.O. relay or contactor to disconnect the PV panels from the batteries whilst there is a supply of grid power? The inverter does have a "remote start" N.O. relay that closes when the battery voltage drops to a predetermined level. This relay could thus be used to switch a larger relay/contactor that could then switch on the circuit from the PV panels to the batteries, thus only charging the batteries when needed.

3. Would PV panels be harmed in any way if they are exposed to bright sunshine every day, whilst disconnected from any load?

4. Any other comments or advise about this system?

Thanks

HennieL

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Newby from South Africa

    Hello and welcome to the forum!
    I shall at least try to start answering your questions. Others may soon chime in with their own input.
    HennieL wrote: »

    Questions:

    1. Would it be practical / possible to have some PV panels (say, supplying 10A at 24V) hooked up to the batteries whilst the system is in "normal" standby mode (being powered from the grid, and thus trickle charging the batteries from the inverter)? Would this not confuse the charge controllers of the inverter and the PV panels? Also, how would one limit the current from the PV panels to not over-charge the batteries (which are normally only "idling" at full charge)?

    Entirely possible to add PV. Charge controllers don't get confused, really (except in certain rare circumstances). The controller will take care of limiting the current - that's its job.
    2. If not, would it be feasible to install a N.O. relay or contactor to disconnect the PV panels from the batteries whilst there is a supply of grid power? The inverter does have a "remote start" N.O. relay that closes when the battery voltage drops to a predetermined level. This relay could thus be used to switch a larger relay/contactor that could then switch on the circuit from the PV panels to the batteries, thus only charging the batteries when needed.

    Not actually necessary. I suspect your "remote start" relay is designed to start a generator in case of low battery Voltage. The PV's can remain connected at all times.
    3. Would PV panels be harmed in any way if they are exposed to bright sunshine every day, whilst disconnected from any load?

    No. PV's are perfectly capable of sitting in full sun and producing nothing if they're not hooked up to anything. In fact, much of the time they do this: once the batteries are fully charged they only need a small amount of current to maintain "Float" Voltage and keep up with loads. The full potential output of the PV's is not utilized.
    4. Any other comments or advise about this system?

    Thanks

    HennieL

    I'll just give you an example of what you might need for PV charging. You've got 320 Amp hours of 12 Volt battery, so the formula goes something like this:

    320 @ 5% = 16 Amps charging current @ 14.2 Volts = 227 Watts @ 77% efficiency = 295 Watts.

    That's a rough calculation for fully charging at the minimum recommended rate. It is not necessarily exactly what you need. For instance, temps in South Africa can be very high indeed, and that reduces PV output. You might have better/worse than typical insolation so the efficiency factor might be higher/lower. But it gives you some idea.

    You might get by with 2 135 Watt panels (slightly more would be better) like this: http://www.solar-electric.com/kyso130wa12v.html and a simple charge controller like this: http://www.solar-electric.com/ss-20l.html (Since you are not expecting full charging ability from your panels.)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Newby from South Africa

    Welcome to the Forum HennieL.

    Your English looks better than my "American". :blush:

    Your numbers all look reasonable--I assume you have accounted for Inverter Losses (85% efficient or so).

    Battery wise, you if can avoid cycling deeper than 50%, you will have longer battery life.

    And avoid taking the battery any deeper than 20% state of charge to avoid permanent battery damage (taking one or more cells dead and them "reverse charging" by the other cells).

    Have you looked at a Battery Monitor (like here, here, or here)... It can make battery management (and avoiding damage) much easier.
    HennieL wrote: »
    I am now considering installing some PV panels to either take this circuit "off grid" completely (with additional batteries added as well), or to just expand the "window of backup power" with the panels charging the batteries during the day, whilst they are supplying the inverter with power . The reason that I'm considering the latter option very seriously, is that both PV panels and deep discharge batteries are VERY expensive here in South Africa, and that upgrading to a totally "off grid" system would be prohibitively expensive, even for such a small system.

    Questions:

    1. Would it be practical / possible to have some PV panels (say, supplying 10A at 24V) hooked up to the batteries whilst the system is in "normal" standby mode (being powered from the grid, and thus trickle charging the batteries from the inverter)? Would this not confuse the charge controllers of the inverter and the PV panels? Also, how would one limit the current from the PV panels to not over-charge the batteries (which are normally only "idling" at full charge)?

    You can parallel battery chargers on your battery bank without any issues (usually). They will not coordinate their state of charge (Bulk, Absorb, Float)--but it will not matter too much.

    In general, it is very difficult to compete with power grid vs off-grid power in terms of costs... You can do your own calculations pretty easily. Cost of hardware + cost of battery replacement + hardware replacement / kWH generated per year * 20 year life = Cost/kWH

    In the US, every time I have "run the numbers" I have come up with ~$0.45 per kWH just to run an AC battery charger + battery bank + AC inverter (not including the AC power needed to charge the battery bank).

    For pure off-grid power, it works out to ~$1-$2+ per kWH...

    The major costs being that Off-Grid power from Solar panels to charge controllers to battery bank to AC inverter is around 50% efficient (each energy conversion step costs 10-20% losses--so it all adds up). Plus replacing batteries every 5-10 years and new electronics ~10 years.

    So, your best bet (in my humble opinion) is:
    1. Conservation--It is almost always cheaper to conserve than to generate power (laptop vs desktop computer, new/efficient fridge, turn off standby loads, lighting, etc.). For aquariums, if you have lights for reefs--Turning them off/reducing lighting when there are occasional grid disruptions can save a lot of energy--Obviously not an option if losing power is common every afternoon.
    2. Create a UPS system--like you have and power it from grid power (assuming 8 hour a day or less in blackouts).
    3. Battery Monitor to allow you to measure/manage loads/charging/current state of charge on battery bank.
    4. Setup a Generator (petrol, diesel, whatever fuel source makes sense for your region) that is just big enough for your "emergency" loads (oversizing generators costs a whole bunch extra in fuel costs).
    5. Solar PV--Add solar panels with a good charge controller as your finances permit to the battery bank.
    Again, in my opinion, Off-Grid Solar PV does not make a lot of economic sense unless you are using the power over 9 months of the year (emergency use during outages is hard to justify vs a small fuel efficient genset).

    Off-Grid does can make sense where fuel is difficult to come by and/or electric power is very expensive (over $1 per kWH using US pricing). Your floor costs will be different (battery/hardware costs are probably more in your region).

    Model out your system in a spread sheet and figure out your total cost of ownership vs grid/generator power.

    Obviously, the loss of a large aquarium population/reef population due to power outages will factor into your decision.
    2. If not, would it be feasible to install a N.O. relay or contactor to disconnect the PV panels from the batteries whilst there is a supply of grid power? The inverter does have a "remote start" N.O. relay that closes when the battery voltage drops to a predetermined level. This relay could thus be used to switch a larger relay/contactor that could then switch on the circuit from the PV panels to the batteries, thus only charging the batteries when needed.
    At least in terms of battery charging--A good "solar" charge controller will charge the batteries when needed and cut back on current/voltage when the batteries are full (or the Grid Charger is charging too). Which ever charger has the higher voltage setpoint will be the one doing most of the charging (within capabilities).
    3. Would PV panels be harmed in any way if they are exposed to bright sunshine every day, whilst disconnected from any load?
    No, they are fine. They do not need loads to limit their maximum voltage.
    4. Any other comments or advise about this system?

    In the end, use a sharp pencil to figure out the total costs of your system (including replacement parts over time).

    It sounds like you have defined your loads well... Next, design the battery bank to meet your needs, then lastly the charging sources to keep the batteries "happy".

    Conservation is always the first stop on this journey.

    I think you are doing it correctly--Start with a "UPS" type system with generator backup (if needed), then add solar panels as finances allow.

    Probably, I have mostly just confirmed your thoughts and direction... There is probably not a lot that I can add.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Newby from South Africa

    henniel,
    here's the bad news. you have loads that are about .2c total or 20% of the ah capacity. this means that it is a high discharge rate and at that rate it may last about 2 hours or so before reaching the 50% dod point for you don't want to go beyond that point seeing as you want the batteries to last for a reasonable number of years. this means to go 20hrs you would need a battery bank that could deliver 60a at 24v for 20hrs and equates to a battery bank of 1200ah at 24v. being you don't want to deplete the batteries below 50% dod then you can do that 60a for 10hrs using a 1200ah battery bank so to go 20hrs at 60a you need a 2400ah battery bank!. you may not need quite that much for backup, but you are quite low in capacity for the loads that are presented and more ah capacity would be warranted. if the batteries are fairly new and haven't been abused yet then go ahead and add more batteries.

    now the charge aspect for batteries is generally a range of 5-13% of the ah capacity. agm batteries can take more than 13% and it is good to get an idea of the maximum the battery manufacturer would say is good to charge with just so you know you won't ever charge them too hard. solar can very well be added and it can get to be a very large array given your needs in the case of a prolonged outage or you would need to conserve what you have until it runs out.
  • System2
    System2 Posts: 6,290 admin
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    Re: Newby from South Africa
    Hello and welcome to the forum!
    I shall at least try to start answering your questions. Others may soon chime in with their own input.

    Thanks for the warm welcome, everyone :D
    Charge controllers don't get confused, really (except in certain rare circumstances). The controller will take care of limiting the current - that's its job...

    ...You can parallel battery chargers on your battery bank without any issues (usually). They will not coordinate their state of charge (Bulk, Absorb, Float)--but it will not matter too much.

    THAT's good news. The battery charger is built-in to the inverter, and is an "intelligent" charger, which monitors the battery voltage to set "bulk", "absorption", "floating" and "equalization" charges according to a built-in algorithm (with the equalization charge currently disabled, because of the VRLA batteries being used).
    I suspect your "remote start" relay is designed to start a generator in case of low battery Voltage. The PV's can remain connected at all times.

    Correct - it is actually meant to start a generator, but it would be pretty simple to wire it to rather start/stop the PV's, if that is necessary (or beneficial).
    I'll just give you an example of what you might need for PV charging. You've got 320 Amp hours of 12 Volt battery, so the formula goes something like this:

    320 @ 5% = 16 Amps charging current @ 14.2 Volts = 227 Watts @ 77% efficiency = 295 Watts.

    Perhaps you misread (I do it all the time :roll: ) but I have 4 x 160Ah batteries, hooked up to give me 320Ah at 24V - in other words, two sets of two batteries in serial, hooked up in parallel, so the wattage would be approximately double, and I assume that I would then need at least four panels?
    Again, in my opinion, Off-Grid Solar PV does not make a lot of economic sense unless you are using the power over 9 months of the year (emergency use during outages is hard to justify vs a small fuel efficient genset).

    Yes, having done some homework this certainly looks to be true. On the other hand, my work (Civil Engineering) takes me away from home for rather extended periods, and there are often periods of 10-12 hours when there are nobody at home - and the "auto-starting" inverter is the only thing that will keep my aquarium alive, and my beers cold ;)
    So, your best bet (in my humble opinion) is:
    1. Conservation--It is almost always cheaper to conserve than to generate power (laptop vs desktop computer, new/efficient fridge, turn off standby loads, lighting, etc.). For aquariums, if you have lights for reefs--Turning them off/reducing lighting when there are occasional grid disruptions can save a lot of energy--Obviously not an option if losing power is common every afternoon.
    2. Create a UPS system--like you have and power it from grid power (assuming 8 hour a day or less in blackouts).
    3. Battery Monitor to allow you to measure/manage loads/charging/current state of charge on battery bank.
    4. Setup a Generator (petrol, diesel, whatever fuel source makes sense for your region) that is just big enough for your "emergency" loads (oversizing generators costs a whole bunch extra in fuel costs).
    5. Solar PV--Add solar panels with a good charge controller as your finances permit to the battery bank.

    I agree, conservation is very important. I already have a solar hot-water system, a LP gas stove, and compact fluorescent "energy saver" lamps throughout the house.

    I also do have a 6.5kVA petrol generator, but it needs to be started manually (and the petrol is pretty expensive). On the infrequent occasions where the power outage exceeds the batteries' runtime, I (or more likely my wife) have/will start the generator, but it would be more convenient (and a lot greater peace of mind) if I could extend the inverter run-time by another few hours - and THAT's the main reason why I'm thinking of installing a few PV panels.
    here's the bad news. you have loads that are about .2c total or 20% of the ah capacity. this means that it is a high discharge rate and at that rate it may last about 2 hours or so before reaching the 50% dod point for you don't want to go beyond that point seeing as you want the batteries to last for a reasonable number of years

    The maximum load is a pretty theoretical "worst case scenario", and in practice is not really half that bad... The maximum load was measured with ALL the lights in the house burning at the same time, AND with my computer on as well. We never keep all the lights on at the same time, and if we are at home when the mains power fail, we can switch most of the lights and the computer off. When we are away from home, the lights and computer are routinely switched off as well, and it's only the aquarium and the fridge that pulls load. In practice the load would not exceed about 20A @ 24V (measured between the batteries and the inverter).

    According to the battery manufacturer's data sheet, each (12V) battery can supply 7.4A for 20 hours, to a terminal voltage of 1.9V/cell. Their recommended maximum charging current is 0.3C, which equates to 96A for the battery bank. The inverter has a maximum charge current of 37A (at 28.8V maximum), but I have it set at 33A as the batteries are meant for standby, and not for cyclic, use.
    if the batteries are fairly new and haven't been abused yet then go ahead and add more batteries.

    The batteries are about two years old (or perhaps another 6 months older, allowing for shipping from China...), and have only once been discharged to 60% DOD (13.5 hours at 14A@24V). I could add another two batteries in parallel, taking the total capacity to 480Ah, if you still think that is necessary.

    Thanks again for everyone's input thus far - please feel free to add more 8)

    HennieL
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Newby from South Africa

    :blush: Yes I misread 24 as 12. It happens.
    But the principal is the same and your assumption of 2X the panels is correct. Let me stress that in this case it would be 540 Watts, and that would be very marginal. Ideally for 320 Amp hours @ 24 Volts you'd want:

    32 Amps charge current @ 28.4 Volts = 908 Watts derated, or about 1200 Watts total.

    Of course then you'll need a bigger charge controller, and at that level its worth considering the (more expensive) MPPT type. It is not necessary to "turn on/off" the PV's; they can stay connected to the batteries all the time.

    I wonder if it wouldn't be more practical to make use of the inverter's gen start and hook up a generator instead of solar panels? That would of course depend on price and availability of all components in your area.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Newby from South Africa

    How many panels is always an open question... You size the battery bank for your loads, and size the panels to both run the loads and properly charge the battery bank (if solar is your main source of charging current).

    Large battery bank and small loads is many people's thoughts for making a better system...

    Problem is batteries need around 5-13% of Capacity (we use 20 hour rate) to properly charge--and tall flooded cell batteries should really have 10%+ rate of charge.

    In your case, you can add solar panels in any amount you wish (from 1 watt to even 20 or 30% of AH capacity) since you have the utility power to charge.

    Regarding the genset... A 320 AH 24 volt bank--the "optimum" (is in quotes--there is a lot of engineering to delve into if you have the interest to tweak that number) sizing calculations would look like:
    • 320 AH * 29 volts charging * 1/0.80 charging efficiency * 0.13 charge current * 1/0.50 generator loading = 3,015 watt rated genset
    • 320 AH * 0.13 = 41.6 amp charger
    So, you could use 1/2 the size of genset (or even less genset/more charge current if the charger has a power factor corrected AC input) and charge your battery bank exactly the same as today.

    On the other, with your 6.5 kVA genest, you could run a charger:
    • 6,500 VA * 0.5 derating * 0.8 charger efficiency * 1/29 volts charging = 89.7 amps
    Since your battery vendor has already said 0.3C / 96 amps is acceptable... You could put a large battery charger on your current genset and use probably 1/2 the amount of fuel to recharge the battery bank (assuming you have no other use for the generator)...

    If you can keep your generator at 50% or more of capacity, your kWH/liter of fuel efficiency will be much higher.

    Regarding solar panels, look at larger panels--Generally the >100 watt panels are less expensive when compared on a $$$/Watt basis...

    Another issue is >100 watt panels don't standardize on Vmp/Imp ratings... So it can be really difficult to mix/match panels purchased at different times and trying to put them all on one solar charge controller (for parallel connections, Vmp's should match within 10% or better; for series connections, Imp's should match within 10%--The farther the mismatch, the poor energy collection you will have).

    Anyway, that is how I would look at the issue of sizing...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Newby from South Africa

    for backups purposes,
    then you can go with a smaller charge % and do this considering only getting 77% out of the pvs so 5% of 320a= 16a/.77=20.78a in pv. it has to provide a high enough vmp to accommodate the 24v battery bank so you don't want to feed it 29v or so and expect the batteries to stay fully charged for you'd need at least about 33 to 35v for the vmp. if the pv or series combo of pvs is much higher in vmp it is good to use an mppt type controller for better efficiency. i like the mppt controllers even if the vmp is good enough for pwm type controllers.

    to go off grid altogether,
    you'll need to get a better handle on your average loads per day to know your requirements for an off grid system. you also wouldn't want the pvs to be marginally sufficient in supplying your power either unless you intend to supplement with a generator occasionally. if possible keep the grid power as it is more apt to be cheaper than solar, but supplementation of power with solar is very viable. i don't know if gt systems are allowed where you are, but if they are you can do this in addition to the backups for the power the pvs make could be used to either charge your batteries through the inverter charger and when full the power is sent to the grid to offset your electric bill, providing the grid is there of course.
  • System2
    System2 Posts: 6,290 admin
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    Re: Newby from South Africa
    I wonder if it wouldn't be more practical to make use of the inverter's gen start and hook up a generator instead of solar panels? That would of course depend on price and availability of all components in your area.
    I have been looking for a cost effective "auto start" (for want of a better word...) system, but the only components available are expensive industrial units, costing the same (or more) than the generator. I have also considered building my own unit (a few relays and 555 timers should suffice), but I would prefer to have a unit with some guarantee, seeing as reliability and safety would be crucial, and I'm only an amateur when it comes to electronics & electricity). Switching the PV panels on and off would only require one contactor, and would thus be much simpler for me to install (but you guys have convinced me that it won't be necessary to disconnect the PV's, so that won't be necessary...)
    Regarding the genset... A 320 AH 24 volt bank--the "optimum" (is in quotes--there is a lot of engineering to delve into if you have the interest to tweak that number) sizing calculations would look like:
    • 320 AH * 29 volts charging * 1/0.80 charging efficiency * 0.13 charge current * 1/0.50 generator loading = 3,015 watt rated genset
    • 320 AH * 0.13 = 41.6 amp charger
    So, you could use 1/2 the size of genset (or even less genset/more charge current if the charger has a power factor corrected AC input) and charge your battery bank exactly the same as today.

    On the other, with your 6.5 kVA genest, you could run a charger:
    • 6,500 VA * 0.5 derating * 0.8 charger efficiency * 1/29 volts charging = 89.7 amps
    Since your battery vendor has already said 0.3C / 96 amps is acceptable... You could put a large battery charger on your current genset and use probably 1/2 the amount of fuel to recharge the battery bank (assuming you have no other use for the generator)...

    If you can keep your generator at 50% or more of capacity, your kWH/liter of fuel efficiency will be much higher.
    Thanks - some good info here :)

    The Generator is, of course, also meant to run the other appliances in and around the house - there is a microwave oven, a deep freezer, washing machine, fans... not to mention various electrical tools in the workshop. It is also quite handy to power the welder when welding is required away from the workshop, and a smaller unit just won't do. I never considered the option of using a larger charger for a shorter time, though, and will definitely have to give this some thought...
    i don't know if gt systems are allowed where you are, but if they are you can do this in addition to the backups for the power the pvs make could be used to either charge your batteries through the inverter charger and when full the power is sent to the grid to offset your electric bill, providing the grid is there of course.
    Unfortunately no - we don't have any grid-tie options in South Africa (although there has been some talk about this, but with the efficiency of our third-world government I don't expect anything concrete for another 10 - 20 years, if ever...)

    So - It looks like I will do the following:

    At this point in time
    • Install 4 x 135W, or 2 x 200W panels
    • Install a MPPT controller capable of controlling at least 30A at 24V (would it be wise to double the capacity, to allow for future expansion?)
    When finances allow:
    • Add two more batteries (of the same make & model).
    These batteries are predicted to have a 12 year service life if operated at 25°C, and around 10 years at 30°C. They are kept in a room where the temperature rarely rises above 30°C, and given that they are not frequently deep discharged, I expect at least another 5-6 years of service from them.

    Should I still add another two batteries to the bank during the next year or so (as finances allow), to increase capacity? I'm prepared to live with the shortened life span of the new batteries in exchange for the increased capacity, if they also only last 5-6 years, but would the new batteries not somehow shorten the remaining life of the old batteries?
    Again, THANK YOU very much for the wisdom shared so far :D

    HennieL
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Newby from South Africa

    "Install a MPPT controller capable of controlling at least 30A at 24V (would it be wise to double the capacity, to allow for future expansion?)"

    that will be your call as you could buy another controller later along with more pvs. make sure the only thing shared is the battery bank as no pv should be connected to more than 1 cc.

    "Should I still add another two batteries to the bank during the next year or so (as finances allow), to increase capacity?"

    if you are going to add batteries it should be asap for the worst battery of the bunch will drag down the rest of them to its level and even the new ones will be dragged down too.

    "I'm prepared to live with the shortened life span of the new batteries in exchange for the increased capacity, if they also only last 5-6 years, but would the new batteries not somehow shorten the remaining life of the old batteries?"

    you could do that, but they may not last as long as you figure them to.
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Newby from South Africa

    Hallo daar boet!

    Would you believe that I grew up in Bloemfontein, small world :D
    To add to the other comments, if you're going to add solar panels with a solar charge controller, why not make use of all that spare energy once the batteries are charged? E.g. Since your studer has a relay for low battery, you could switch the grid in using that relay, and then configure the low battery voltage setting quite high so that you only use solar power when it's available and don't draw down your batteries too much. Then you could run off solar most of the day, and the weather in Bloem is very good for solar: high altitude and clear winter skies.

    As for the generator auto-start, I configured my diesel gen using a 50 GBP unit from Deepsea, was quite easy to fit once I worked out what all the wiring in the gen was for, some pics here: http://www.casanogaldelasbrujas.com/blog/2009/05/25/new-control-unit-for-volvox-generator/
  • System2
    System2 Posts: 6,290 admin
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    Re: Newby from South Africa
    Since your studer has a relay for low battery, you could switch the grid in using that relay, and then configure the low battery voltage setting quite high so that you only use solar power when it's available and don't draw down your batteries too much. Then you could run off solar most of the day

    Wow - this is a good idea! I will certainly give it some thought :)
    ...the weather in Bloem is very good for solar: high altitude and clear winter skies.

    Yup - if solar was not so prohibitively expensive, we would all have been using it long ago - was just quoted the equivalent of between $3.00 and $5.00 per Watt for just the supply of the PV panels (excluding transport, frames and installation, which about doubles that...)

    HennieL