Inverter, batteries and a Solar panel or 2

[The_Traveller]

The devil is in the detail....

Oops...

 

[gifs]

That's a good inverter, but $$$ ... anyways to answer your question ...

you're right, to add voltage, you need to wire in series.

The advantage of a 48v over a 24 is that you will have extended backup time ... for example ...
If your load is 1000w ...
on a 24v system - 1000/24 = 41.66Ah
on a 48v system - 1000/48 = 20.83Ah

So if you using 12v100ah batteries, then on a 24v system .... 100/41.66 = 2.4 hours
on a 48v system ... 100/20.83 = 4.8 hours

ALL OF THE ABOVE IS NOT TAKING INTO ACCOUNT INVERTER EFFICIENCY, BATTERY DC CURVES ETC. JUST A QUICK LOOK AT WHY A 48V IS BETTER THAN A 24V , BECAUSE YOU HAVE MORE BATTERY.

To get a 48V system, you need 4 x 12V batteries in series. For a 24V system you need 2 x 12V batteries in series. So in order to get double the capacity, you still need double the amount of batteries, so there is no extended run-time benefit.

Whether you configure 4 batteries in series for 48V or in series/parallel to get 24V, you will end up with the same run-time.

 

[Mypro-D]

I ordered this from AC Digital in Cape Town
I know its a bit pricy but we have a 50kva inverter and batteries from them at work and it has worked beautifully for the last 7 years.

The 2,2 Kva Riello Aros sentinel Pro ER true on line UPS with VRLA type batteries (batteries designed for use with UPS that cannot gas or leak) housed on a covered battery stand to support a 1250 watt load for +-3 hours.
Price R 19545, 00 excluding VAT.

Optional SNMP card for network monitoring - R 2315, 00 excluding VAT.

Availability - currently 3 - 4 weeks when our next shipment arrives.

For your information, please find attached the brochure for the Riello Aros Sentinel Pro range of UPS. 2 year carry in warrantee on the UPS. 1 year warrantee on the batteries.

Please feel free to give me a call if you have any queries. If you wish to place an order, we recommend that you do so sooner rather than later as customers are already placing orders for units on incoming shipments. It is also important that we place the order on the battery importer to ensure battery stocks are available when the UPS arrive as they are experiencing large volumes of orders as well.

Prices are current for the UPS and batteries but may change for UPS and batteries drawn from future shipments.
Recharge time after a full discharge is 8 hours making this UPS ideal for repetitive load shedding applications.

 

[The_Traveller]

The devil is in the detail....

To get a 48V system, you need 4 x 12V batteries in series. For a 24V system you need 2 x 12V batteries in series. So in order to get double the capacity, you still need double the amount of batteries, so there is no extended run-time benefit.

Whether you configure 4 batteries in series for 48V or in series/parallel to get 24V, you will end up with the same run-time.

Yes you're right. My bad ... forgot I am using just one string on my 24v system and had 2 strings on my 48v system.

 

[akescpt]

Bloody insane...

 

[BigEars]

The whole idea with using more batteries in Series is that your battery cables can be thinner and generally less current flowing and therefore less loss. Good for big installations etc...

Not for Mickey Mouse installations like we are talking about here.

In fact....for example...a cheap 12V system comprising one 100Ah battery might set you back R1200.00 for the battery, say R800.00 for the UPS (simulated Sine Wave), and another R1200.00 for a proper charger to treat the huge battery well.
With that you can run 1X lappie, Telkom internet modem, a CRT 51CM, and a few LED lights well through blackouts lasting 3 Hours.

All you do by going the 24V route at this level is adding expense. To do the same job you now need 2X 50Ah batteries...

I hope I am making sense

 

[KleinBoontjie]

Check this post of mine, with pics
This is one my brother in law did. ATM, or that was back in March, he only had the 2 batteries, 2 panels and only pulled his TV and lights with it. I must add, he has an old CRT 51cm TV.
He is going to add batteries and panels, like one item per month. His goal is to put everything in his house on this, except geyser and oven.

 

[Niner]

To get a 48V system, you need 4 x 12V batteries in series. For a 24V system you need 2 x 12V batteries in series. So in order to get double the capacity, you still need double the amount of batteries, so there is no extended run-time benefit.

Whether you configure 4 batteries in series for 48V or in series/parallel to get 24V, you will end up with the same run-time.

Thanks, that's how I had it. I disagree with you on parallel, though, based on what I've read. Parallel doubles your amperage, for a given wattage.

Also, Traveler, I was aware that the system adds resistance etc. I'll allow for that when doing my final budgeting.

The whole idea with going for a very good inverter is having the option of converting to solar later on. There's definitely cheaper options out there. Also, the 3kw inverter has a pretty great 6kw surge rating, so if my (soon to be) new baby needs its milk heated now, I can use the microwave, instead of slowly heating it on gas.

Or I can get a proper genny, running at R25,00/hour, noisy and costs R18k.

 

[The_Traveller]

Thanks, that's how I had it. I disagree with you on parallel, though, based on what I've read. Parallel doubles your amperage, for a given wattage.

Also, Traveler, I was aware that the system adds resistance etc. I'll allow for that when doing my final budgeting.

The whole idea with going for a very good inverter is having the option of converting to solar later on. There's definitely cheaper options out there. Also, the 3kw inverter has a pretty great 6kw surge rating, so if my (soon to be) new baby needs its milk heated now, I can use the microwave, instead of slowly heating it on gas.

Or I can get a proper genny, running at R25,00/hour, noisy and costs R18k.

Surge rating is for a few seconds AFAIK , but I might be wrong.

 

[Niner]

Surge rating is for a few seconds AFAIK , but I might be wrong.

Thank you - I'll investigate further. Someone would really make a killing if they made proper 'kits' you could just buy. The ones 1 found are damn expensive, though.

 

[MrGray]

Surge rating is for a few seconds AFAIK , but I might be wrong.

Yes, but my understanding is that's all you need to get certain appliances to run? Simplistically something like a microwave may run at a sustained draw of say, 2000w, but need 4000w to start?

 

[itareanlnotani]

1'st question - 24v or 48v? And if I calculate that I need 250Ah of battery life(already accounting for dod), do I need 2 12v batteries in series for 24v(and 4 for 48v), to get the same amperage? What exactly would be the benefit of going 48v over 24v then?

Lead Acid droops quite a bit under load - voltage dips quite a bit under heavy loads.
So traditionally you'd go with a larger voltage if you have heavier loads so that you can supply whats needed, as more batteries will equal less current draw across each battery, and hence less droop.

Thats the main reason, cabling is secondary (cheaper to run higher voltage / lower amps than higher amps / lower voltage)

Other battery technologies are better, and don't have that issue (eg Lithium)

 

[Alton Turner Blackwood]

The whole idea with using more batteries in Series is that your battery cables can be thinner and generally less current flowing and therefore less loss. Good for big installations etc...

Not for Mickey Mouse installations like we are talking about here.

All you do by going the 24V route at this level is adding expense. To do the same job you now need 2X 50Ah batteries...

I hope I am making sense

You did see that OP wants to expand as time goes on, right?

There's a reason why people don't use 12 volts for solar installs and that is because of safety and efficiency.

If he starts off with 12v now he will have to buy a new 24v or 48v inverter when he goes bigger.

Good luck trying to not burn down your house with a 12v system :twisted:

 

[mwill]

You did see that OP wants to expand as time goes on, right?

There's a reason why people don't use 12 volts for solar installs and that is because of safety and efficiency.

If he starts off with 12v now he will have to buy a new 24v or 48v inverter when he goes bigger.

Good luck trying to not burn down your house with a 12v system :twisted:

Hi YingYang. I'm very interested why 24 or 48 volt systems are preferable for solar systems and 12 volts could be dangerous. Could you please explain as I am thinking of using solar panels in the future. Many thanks

 

[Alton Turner Blackwood]

Hi YingYang. I'm very interested why 24 or 48 volt systems are preferable for solar systems and 12 volts could be dangerous. Could you please explain as I am thinking of using solar panels in the future. Many thanks

its fairly simple

Example: 60 amps at 12 volts will melt wires and perhaps kill you under certain conditions. 30 amps at 24v will tickle you perhaps. 15 amps at 48v you won't even feel!

All three of the above will give you 720w. However 12v=thickass wires which can burn schit down. 48v=thin wires and you don't have to worry about a thing.

Ask these guys @Arthur @lsheed_cn

 

[mwill]

Thanks YingYang. I will have to absorb what you said....

 

[BigEars]

its fairly simple

Example: 60 amps at 12 volts will melt wires and perhaps kill you under certain conditions. 30 amps at 24v will tickle you perhaps. 15 amps at 48v you won't even feel!

All three of the above will give you 720w. However 12v=thickass wires which can burn schit down. 48v=thin wires and you don't have to worry about a thing.

Ask these guys @Arthur @lsheed_cn

Wise one you forgot to mention that 100 Ma through your body is enough to kill you.
You know like a nice shock...and the Mains won't let you release and let go. Kinda keeps you there.

 

[StellenboschStudent]

its fairly simple

Example: 60 amps at 12 volts will melt wires and perhaps kill you under certain conditions. 30 amps at 24v will tickle you perhaps. 15 amps at 48v you won't even feel!

All three of the above will give you 720w. However 12v=thickass wires which can burn schit down. 48v=thin wires and you don't have to worry about a thing.

Ask these guys @Arthur @lsheed_cn

15 Amps will definitely kill you.

 

[itareanlnotani]

Lead Acid droops quite a bit under load - voltage dips quite a bit under heavy loads.
So traditionally you'd go with a larger voltage if you have heavier loads so that you can supply whats needed, as more batteries will equal less current draw across each battery, and hence less droop.

Thats the main reason, cabling is secondary (cheaper to run higher voltage / lower amps than higher amps / lower voltage)

Other battery technologies are better, and don't have that issue (eg Lithium)

I did answer it above. Its less the cable, and more the voltage droop to be honest.

 

[treeman]

I found this forum post which points out what system voltage (12,24,48) vs max inverter power can be expected.

http://www.solarpaneltalk.com/showthread.php?10450-Inverter-Size-vs-Battery-Size-Tutorial