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if I have to add additional batteries to prolong the back-up time should I stick with the same configuration of batteries as I have in the battery bank currently (4x6vx225 ah) or can I go for 12v cells (2x 12v x 200Ah)?
When adding batteries in parallel, you must use the same make and model of battery and if at all possible from the same batch of manufacture. This is to ensure that all batteries get charged and discharged simultaneously.
ensure that the charger can handle the extra load, or else, the charge time doubles
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
Although i originally planned to go with 6 volt cells for my 24 volt inverter, now I am considering to go with 12 volt cells instead of 6 volt cells due to space issues. Both 225Ah. Are there any advantages or disadvantages in this regard?
Draining a battery to 50 % on ever cycle would be going to extreme if the battery is a proper deep cycle battery and designed for that application. Not all batteries are capable of being drained to 50 %.
It is in fact better to monitor the voltage of the battery. Once a battery drops below 10.4 volts you can start filling the cookie jar for funds to replace it.
It is not a good idea to work on rule of thumb for these applications. It could be an expensive learning curve.
There are the few who know what they are doing and the masses who have learnt a few technical phrases and use it to baffle the public.
Dont believe read on the internet and make sure the person selling you stuff has a little more than the six months of shedding experience.
People are burnt sore with generators and backup power supplies and incapable chargers for these huge battery packs.
Draining a battery to 50 % on ever cycle would be going to extreme if the battery is a proper deep cycle battery and designed for that application. Not all batteries are capable of being drained to 50 %.
It is in fact better to monitor the voltage of the battery. Once a battery drops below 10.4 volts you can start filling the cooking for funds to replace it.
It is not a good idea to work on rule of thumb for these applications. It could be an expensive learning curve.
There are the few who know what they are doing and the masses who have learnt a few technical phrases and use it to baffle the public.
Dont believe read on the internet and make sure the person selling you stuff has a little more than the six months of shedding experience.
People are burnt sore with generators and backup power supplies and incapable chargers for these huge battery packs.[/QUOTE]
Ja I'd recommend reading the manufacturer's specification sheet for whatever batteries you are looking at. E.g. a general purpose battery may only last 260 cycles at 100% discharge but more than 500 cycles at 50%. You could reach 1200 cycles if you only discharged by 30%. Note I've just read this from a spec sheet so I'd appreciate if there aren't any arguments on this point. ;-)
I bought some batteries (yes I read the spec sheet first) and stuck them in a UPS I already had. Discharging to 50% means I should get around 500 cycles from the batteries. It tends to get used every second day if there is stage two load shedding. Assuming stage two load shedding every day then I should get about two and half years from it. With a less pessimistic view on load shedding I should get more than that them. Outlay was less then R450.
If load shedding gets worse then I probably won't be using the UPS for a bit of light. Will have moved on to bigger and more expensive things by that point.
I am comparing Trojan 6 volt batteries and 12 volt batteries (both 225Ah) I read that 6 volt is superior due to thicker plates resulting in longevity. How true is this information? Comments appreciated
Currently I have 500W modified sine running off a 12V Battery. If you are interested I can supply at R 945.00 excluding VAT.
I have used this model for about a year now and have not had any comebacks to date.
The electronics are fairly simple, and I have and can get spare components to be able to repair it at board level in case of a component failure.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
Somewhere I am understanding something drastically wrong.
I measured my equipment's amps using a clamp amp meter.
All together they pull 1,8 amp.
My understanding is that 1.8A x 230v = 414 watts
Yet, my 2000va UPS can not handle this. It starts moaning at 1.2A and more than that, it just switches off. Why is that? 2000va x 60% is 1200watt. So it should find 414 watt a breeze?
I checked my amm meter against the kettle now, kettle rated at 1850-2200 watt. It measures 8.5 A to 8.3 A. Which is just under 2000 watt. So meter seems fine.
aha - that is the difference between an expensive inverter and a low cost one. You probably need to verify the phase angle, or Power Factor. The more inductive load there is the more the low cost units struggle to maintain themselves in operation.
The overload trip is on the primary side, or low voltage side. When you have a high inductive load, you need a lot more amps to make the load work, because of the phase angle.
Most inverters are what we call 'unipolar' driven, in which only one side of the H bridge is switched at a variable high speed to create the sine wave, unfortunately when an inductive load is connected, this unbalanced switching causes the bridge to fire incorrectly due to the current being out of sync with the voltage, causing the bridge to over shoot when switching. This over shoot is what causes the primary side driver to use more current to work. Over shoot simply means that the two series power components are active simultaneously causing the link supply to be short circuited.
A bipolar switching process, has all 4 elements of the bridge switching a complex variable process to generate the sine wave. Since all the power components are active in the full quadrant, there is no overshooting, as the bridge elements now control the load with the supply.
The bipolar switching process is more complex and requires a higher quality switching devices and a few more inductive filters to ensure a pure sine wave. These extra characteristics makes the inverter more costly.
That is why there is usually a huge difference between the China Mall inverters and the well known brands, which apply the bipolar switching process.
If you want to measure the phase angle, then you may need a power meter instrument I manufacture for R1650.00 excluding VAT.
Something else that I have come across, not all UPS's are sine wave, and the unit you have may be a modified sine wave, which is more sensitive to inductive loads.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
Somewhere I am understanding something drastically wrong.
I measured my equipment's amps using a clamp amp meter.
All together they pull 1,8 amp.
My understanding is that 1.8A x 230v = 414 watts
Yet, my 2000va UPS can not handle this. It starts moaning at 1.2A and more than that, it just switches off. Why is that? 2000va x 60% is 1200watt. So it should find 414 watt a breeze?
I checked my amm meter against the kettle now, kettle rated at 1850-2200 watt. It measures 8.5 A to 8.3 A. Which is just under 2000 watt. So meter seems fine.
What Justloadit says is true but I'm puzzled about the size of the discrepency between the load and the UPS ability.
Are you using an RMS clamp meter to measure the load current? If not your readings might not be accurate.
Was your load being supplied by the UPS when you measured it? If so then a modified sine UPS could give a false current reading on some instruments.
Is your load something like a fridge where there's going to be a start current that could be five times the normal run current just momentarily. If so your clamp meter might not have a high enough sample rate to see this current spike.
It does sound like there might be some other problem, I've not encountered a 2kva UPS that can't drive a load that's just over 400 watts even if the power factor is poor.
Thanks guys. I will duplicate the exercise later, no time now, SARS is screaming for VAT.
I have some other 2000kva UPS's so will check them out as well. Just a bit pissed with myself, as I bought 3 x 12 volt batts, whereas the others only use 2.
Is R77K a good price for a 3KWA solar system "including batteries, inverter/components and solar panels" It feels a bit pricy to me...
That's kind of a 'how long is a piece of string' type question without lots more details. Is that price for a completely off-grid installation? What inverter, what batteries and what panels are they quoting for (make and model numbers please) also how many of each? Did they include an MPPT charger or is this built into the inverter. Does the price include installation and any alterations to your existing DB and electrical installation (and CoC obviously)?
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
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