UPS or quiet generator

midnightcaller said:
Batteries are about 2 years old. So maybe I need to replace both batteries.

In June the alarm company installed a new transmitter that sends sms to control room when alarm triggers.
I suspect that this transmitter is drawing more amps than the previous transmitter that worked on radio frequencies.

The transformer is a 48va.
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No, its the other way around. An SMS device needs 25mA on standby and 60mA when transmitting (about 2 seconds). A radio transmitter is a 15 or 25 watt device and needs 3 amps for 4 of the 5 second transmission bursts

I suspect that your batteries might not have been new when fitted. I find that 1 out of 20 alarm batteries do not last or provide the performance you expect

I have a 9 a/h battery that powers my alarm (170 mA), the intercom (200 mA when in use) and the CCTV monitor (300mA when in use). Yesterday morning the power was off from 06h00 until 12h50 and the battery was 12.4 V at the end of it.

Prior to fitting the 9 a/h battery, I had a 18 a/h one and this was rubbish - it lasted less than 18 months and probably was in the supplier's warehouse for 3 years before that. There is often a way to determine the manufacture date. Batteries sold by Regal Eltro have a year and date letter, ie a battery stamped K4 would have been made in April 2014
 
chrisc4290 said:
No, its the other way around. An SMS device needs 25mA on standby and 60mA when transmitting (about 2 seconds). A radio transmitter is a 15 or 25 watt device and needs 3 amps for 4 of the 5 second transmission bursts

I suspect that your batteries might not have been new when fitted. I find that 1 out of 20 alarm batteries do not last or provide the performance you expect

I have a 9 a/h battery that powers my alarm (170 mA), the intercom (200 mA when in use) and the CCTV monitor (300mA when in use). Yesterday morning the power was off from 06h00 until 12h50 and the battery was 12.4 V at the end of it.

Prior to fitting the 9 a/h battery, I had a 18 a/h one and this was rubbish - it lasted less than 18 months and probably was in the supplier's warehouse for 3 years before that. There is often a way to determine the manufacture date. Batteries sold by Regal Eltro have a year and date letter, ie a battery stamped K4 would have been made in April 2014
Click to expand...

Didn't realise that the sms transmitter uses less current.

It is possible that the batteries were old.
 
Ive found a local guy that will create a rental unit for me. Ill be paying R500 a month for a fully serviced unit that can supply all my needs for up to 4 hours.

So you think R500 a month is fair? They take responsibility for servicing the unit.
 
ghoti said:
Ive found a local guy that will create a rental unit for me. Ill be paying R500 a month for a fully serviced unit that can supply all my needs for up to 4 hours.

So you think R500 a month is fair? They take responsibility for servicing the unit.
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What doe the R500 include? Seeing that some of my fish cost more than R500 to replace, it doesnt sound like a bad option at all.
 
bekdik said:
The APC is a professionally designed piece of equipment designed to allow up to 10 battery packs.
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Want photos of up to 10 melted battery packs? I'm talking from experience here, but the theory backs me up.
 
Drunkard #1 said:
Want photos of up to 10 melted battery packs? I'm talking from experience here, but the theory backs me up.
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Photos... or it didn't happen :)

Would love to hear more -- what's the issue with the batteries in parallel? Just the internal resistance being multiplied up or something?
 
I remember when I used to work in a factory making up UPS's etc. in KZN how some guys would make a battery explode / cause it to meltdown for fun...

...until one of them go injured.
 
Drunkard #1 said:
Beware of battery strings in parallel. They don't fail, they melt down.
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IMG_5572.jpg

APC puts fuses between each individual battery, so a complete "melt down" seems less likely.

However, things can get desperate if the batteries aren't maintained:

bt_dead_battery_lg.jpg
 
People, I'm lazy, and a few melted, bloated batteries aren't that exciting.

DSC00022.JPGDSC00019.JPGDSC00018.JPG

I noticed the fan was running flat out, then noticed you could braai on the battery cabinet, so I pulled out the battery cages with oven mitts and gave them a few hours to cool. What you see above is the damage to the batteries. The separator plates and hexagonal vents have left an impression and I needed to pry everything apart with a screwdriver. These were stewing for less than a day; I'd hate to see what they look like after a week unattended.

richjdavies said:
Photos... or it didn't happen :)

Would love to hear more -- what's the issue with the batteries in parallel? Just the internal resistance being multiplied up or something?
Click to expand...

The problem is that the weakest string gets most of the charging current, which makes it deteriorate even faster. After a short while, the string resistance is so low that you've basically shorted out the whole system. The other packs have a lot of energy in them, so you get a meltdown.

Gnome said:
<pic>

APC puts fuses between each individual battery, so a complete "melt down" seems less likely.

However, things can get desperate if the batteries aren't maintained:

<pic>
Click to expand...

APC puts one fuse in each cage. The rest of the links are just wire. The fuses are in the heat-shrink-covered link. You can also see the spacer plates and hexagonal vents in this photo.

DSC00020.JPG

Those fuses are 30A x 2, so 60A per string. 10 XLBP battery cabinets means 21 strings, or 1260A at 192V (both nominal). 241kW of power is more than enough to ruin your day. [Yes, I'm fully aware that the fuses will blow before that, at about 18kW. The full power that these cabinets are capable of is just shocking. <ha ha, shocking, that's punny>]

DSC00021.JPG
 
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Those bloated batteries result from a charger simply "pushing" a charging current towards the battery, without any feedback as to how the battery is absorbing the charge

Many batteries can develop an internal short (insulation breaking down) or open circuit (plate clamps coming loose) which will cause the battery to heat up and swell.

I have been using rechargeable batteries in my job since 1976 and have seen all manner of manifestations occur

Paradox (an alarm co based in Canada) have developed an intelligent charger which will stop the charge current and measure the state of the battery at regular intervals. It is suggested that each individual battery in a multiple battery system be equipped with such a charger as you can never know which battery will malfunction and when. It is quite easy with diodes to isolate each battery from the other.

I got a 3000VA UPS with "pure sine wave" output for someone last week. Despite costing R 4400 + VAT and having 6 x 12 volt 7.0 a/h batteries, all the batteries were connected in parallel without any isolation or protection. Yesterday I went to check on the batteries and found one getting quite warm. Instead of an open circuit voltage of 13,65 like the others, this one was down to 12,10 V. Of course the supplier maintains that they have never had any problems, but here is a new unit with the transformer blazing hot trying in vain to charge a faulty battery

So the argument of melted batteries above is a real and present danger and you must be prepared to inspect the batteries on a regular basis

Batteries where the insulation breaks down are often found to use cardboard as an insulator. Rough handling (even dropping) of the battery compromises the insulation, shortening the life
 
Quality UPS systems don't come cheap . Expect to pay R8k+ for a 5kva UPS system that has functions that avoid battery damage.
I got a good one that automatically keeps the charge at optimum levels.
 
The_Traveller said:
Quality UPS systems don't come cheap . Expect to pay R8k+ for a 5kva UPS system that has functions that avoid battery damage.
I got a good one that automatically keeps the charge at optimum levels.
Click to expand...

I was looking at 3kva UPS that were around 14k in price :/
 
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