Inverter/UPS system, help required!

[M@tree2]

Hey all, some help needed, looking at getting an inverter or UPS setup soon, questions:
12/24v, apparently 24v is more efficient, how much more efficient?
Looking to run a load of about 300/400w for roughly 3-4 hours, on deep cycle batteries, given they shouldn't be discharged more than 80%.
Running a 600w plus load is just ludicrous on batteries (9700k, gtx1080, etc etc), come load-shedding or outage I will use my laptop.

NB: The body corporate won't allow a generator, will also need an electrical certification if a fixed install.

I Will be in a sectional title property, so I might want to take this setup with me when I leave, hence I don't really want to have a fixed installation.
If it is a fixed installation, what does this all involve?
Recommendations?

Location: Pretoria
Regards

 

[aiccc]

Are you aware you get inverter gennies that are near silent.

rule of thumb

12 volt is OK for up to 1000 watts
24 volt is OK for up to 2000 watts

1 volt loss on 24v/48v is less percentage loss than on 12v

There is less load on the cables on a 24 system. Age causes cables to deteriorate.

I have a gennie but recently added inverter / battery pack. We have too many power outages. Gennie -> inverter ->small ups ->computer

I can now refuel the gennie with out upsetting the missus.

For you a 12v system would be fine based on wattage to be used.

But this is a better read.

Is a 24V inverter safer than a 12V inverter at 2200W

There are a number of 12V inverters made by reputable manufacturers that will output more than 2200W on a continuous basis so it puzzles me that some people seem to be of the view that it is unsafe running 12V inverters at this power level and insist you should use a 24V inverter.

forum.solar-electric.com

I recommend you have a look here.

Power Forum - Renewable Energy Discussion

powerforum.co.za

 

[M@tree2]

Are you aware you get inverter gennies that are near silent.

rule of thumb

12 volt is OK for up to 1000 watts
24 volt is OK for up to 2000 watts

1 volt loss on 24v/48v is less percentage loss than on 12v

There is less load on the cables on a 24 system. Age causes cables to deteriorate.

I have a gennie but recently added inverter / battery pack. We have too many power outages. Gennie -> inverter ->small ups ->computer

I can now refuel the gennie with out upsetting the missus.

For you a 12v system would be fine based on wattage to be used.

But this is a better read.

Is a 24V inverter safer than a 12V inverter at 2200W

There are a number of 12V inverters made by reputable manufacturers that will output more than 2200W on a continuous basis so it puzzles me that some people seem to be of the view that it is unsafe running 12V inverters at this power level and insist you should use a 24V inverter.

forum.solar-electric.com

I recommend you have a look here.

Power Forum - Renewable Energy Discussion

powerforum.co.za

Awesome, thanks man!
Currently have an inverter generator, but policy is no gennies, that property is in Pretoria, I have the generator on the farm.

Would something like a 24v mecer inverter be okay, or should I look a bit further?

 

[M@tree2]

Are you aware you get inverter gennies that are near silent.

rule of thumb

12 volt is OK for up to 1000 watts
24 volt is OK for up to 2000 watts

1 volt loss on 24v/48v is less percentage loss than on 12v

There is less load on the cables on a 24 system. Age causes cables to deteriorate.

I have a gennie but recently added inverter / battery pack. We have too many power outages. Gennie -> inverter ->small ups ->computer

I can now refuel the gennie with out upsetting the missus.

For you a 12v system would be fine based on wattage to be used.

But this is a better read.

Is a 24V inverter safer than a 12V inverter at 2200W

There are a number of 12V inverters made by reputable manufacturers that will output more than 2200W on a continuous basis so it puzzles me that some people seem to be of the view that it is unsafe running 12V inverters at this power level and insist you should use a 24V inverter.

forum.solar-electric.com

I recommend you have a look here.

Power Forum - Renewable Energy Discussion

powerforum.co.za

Just reading a bit further and from trying to parallel charge a homemade 4S lipo, balance charging is a PITA.

Theoretically, on some very crude math, I should get the same run time out of a 48v inverter system, with less amperage on the wires.

 

[aiccc]

The local forum has many threads on the mecer inverter.

 

[M@tree2]

The local forum has many threads on the mecer inverter.

Hmm, 60% efficiency on the mecer, quite low.
Have found something from sinetech.co.za, 88% efficiency at 12/24v, given it is 2-3 times the price of the mecer.

 

[M@tree2]

Next question, when wiring 4x105AH Lead acids in parallel, what stops them having unequal internal resistance, and by what basic physics knowledge I have, if the cells IR is different, then voltage output per cell will be different and can lead to horrendous imbalances over the course of a few months.

Have read that the EQ time of a daily cycle PB in series is a few months, so plenty of time for it to go wrong.


Given I have 4x105AH lead-acid batteries, what is the best way to get the safest and best efficiency out of them?

 

[rulingtex]

I would suggest a bit of reading on PowerForum

 

[M@tree2]

I understand the time calculations etc, I'm looking for the technical advice on the efficiency of 12/24/48V systems, how to keep all batteries at equal voltage, given each PB will inevitably have different internal resistance to the next, thus each having a different charge characteristic, which could lead to one being out of whack, when compared to the others, damaging your batteries.
This is where 24v or 48v especially does a better job of managing each BLOCK(EACH 12v), or apparently so.

As someone who has dealt with LiPos and joined cells together, balance charging each cell is extremely important for proper operation, otherwise, you get an imbalance, and well we know how well that works out with LiPos. So based on that knowledge, PB's should be no different, so ultimately, what stops a PB from being 2-3V different from the next one, if not balance charged?
Hence 12/24/48V for this application, based on the batteries that I currently have at my disposal?
Batteries at my disposal 4x105AH Deep cycles.

 

[aiccc]

I did a bit of reading prior to the inverter install. But I am no way an expert. The power forum guys can certainly answer this type of question.

However if you need less that 1000w, stick with 12v. It is cheap and will work.

If you intend to increase the wattage draw; then investigate carefully.

Note LiPos has pros and cons. There is a buy one get one free deal atm. It is a bargain.

Just a note, there are numerous scammers out there. A trusted person tried to defraud me.

I got a retired sparky to do the install. I saved a bit of money on the labour. But still not cheap.

 

[SPWM]

I did a bit of reading prior to the inverter install. But I am no way an expert. The power forum guys can certainly answer this type of question.

However if you need less that 1000w, stick with 12v. It is cheap and will work.

If you intend to increase the wattage draw; then investigate carefully.

Note LiPos has pros and cons. There is a buy one get one free deal atm. It is a bargain.

Just a note, there are numerous scammers out there. A trusted person tried to defraud me.

I got a retired sparky to do the install. I saved a bit of money on the labour. But still not cheap.

Pls share who is selling buy one get one free?

Sent from my SM-G960F using Tapatalk

 

[wes1987]

This depends what you are trying to get out of it in the end.

24V would work out better, thinner cables (saves a lot), cheaper breakers as less current draw.

Now you also need to look what you want to run, if it's on SMPS (Switch mode Power supplies) like that of a computer PSU, or laptop charger, you are ok with a cheap mecer modified sine inverter. if you want to run anything with a transformer as a step down converter (think high quality Audio gear), or a motor you going to need a pure sine inverter.

For your purpose, I think the Mecer 2400VA unit (it is a 24V unit I think) running in a 2P2S config will work. that should give you around 210AH of capacity @ 24V... taking the fact you only want to discard max 50% of it, 105AH will be available to you.

for the VRLA batteries, you can buy small balances (part number is HA01), you will need 1)
to run between the series back, to keep them balance. however should you not be doing high current discharges, they should remain fairly well balance throughout.

For LiPo batteries, that's a different issue all together, you will need special charger, with balance capabilities. or a dedicated BMS, a voltage difference of more then 0.5V per cell could be a huge fire hazard. I would recommend rather Li-ION, or LiFE.

 

[M@tree2]

This depends on what you are trying to get out of it in the end.

24V would work out better, thinner cables (saves a lot), cheaper breakers as less current draw.

Now you also need to look what you want to run, if it's on SMPS (Switch Mode Power supplies) like that of a computer PSU, or laptop charger, you are ok with a cheap mecer modified sine inverter. if you want to run anything with a transformer as a step-down converter (think high-quality Audio gear), or a motor you going to need a pure sine inverter.

For your purpose, I think the Mecer 2400VA unit (it is a 24V unit I think) running in a 2P2S config will work. that should give you around 210AH of capacity @ 24V... taking the fact you only want to discard max 50% of it, 105AH will be available to you.

for the VRLA batteries, you can buy small balances (part number is HA01), you will need 1)
to run between the series back, to keep the balance. however should you not be doing high current discharges, they should remain fairly well balance throughout.

For LiPo batteries, that's a different issue altogether, you will need a special charger, with balance capabilities. or a dedicated BMS, a voltage difference of more than 0.5V per cell could be a huge fire hazard. I would recommend rather a Li-ION, or LiFE.

Thanks for taking the time!
Not trying to get much, just enough to power an ONT, switch, laptop, 2x24" LED monitors, and 1/2 LED lights in that situation.
Laptop PSU - 45w
2x Dell 24" - 22w each
ONT,switch, WiFi router ~100w
2 LED lights, absolute outside 50w each

No step-down converter as far as I can think of, just general electrical stuff.
With regards to the mecer unit being 60% efficient, this then means we have 63AH available to use.

This then means that at 300W/24v = 12.5A being drawn, and therefore 63/12.5 = ~ 5 hours of runtime when discharging to a min of 50% capacity.

If I look at a unit of >80% then we have 84AH available to expend.
Therefore the same 12.5A being drawn as above, thus 84/12.5 = ~ 6.7 hours, highlights the importance of the efficiency rating.

Given the unit is more expensive, but will include better management.
Thinking something along these lines:
Geewiz AXPERT
or
Something from the likes of Sinetech.
Agreed with the mecer system working, but there are a few areas where it is lacking, also the AXPERT has different battery types in the config, so if down the line, LiFeP04 become viable, I can then replace with that.
With the battery array, it's parallel first, then series, from what I have read, this is the better way to do it, also then allows the 2 parallel blocks to be EQ'd.

Regards

 

[wes1987]

the axpert units are really good. perfect for a DIY ups actually.

The axperts actually work well with the Pylontech batteries, so you can use those in future if you want to expand. you can look at a VM range of it, as they have different solar input options. try get the 1PF unit, as that will be a 3kw unit. They will also allow you to configure the low voltage cut-off etc. so it gives you a better control over the batteries. and the result will be the batteries last longer. they are also pure sine, so sensitive electronics will be good on it.

The effeciency changes on the load level though, some might be better at 50% load, others at 90%. it's hard to actually get an exact figure from a cheaper brand. the more expensive units (think victron) give that to you.

Regarding connections, the way you mention is correct.

Also bear in mind, those loads are worst case scenario, that 45w laptop charger won't be doing 45w all the time, same goes for the screens etc. so you will be safe for 5+ hours.

Main thing though, make sure you can recharge batteries completely before discharging again, and that you set the highest possible charge rate you can for the battery before damaging it... it's usually 0.2C @25 degrees but you will need to check on the batteries data sheet for that.

 

[aiccc]

Pls share who is selling buy one get one free?

will send tomorrow

 

[SPWM]

will send tomorrow

Any feedback?

Sent from my SM-G960F using Tapatalk

 

[aiccc]

Sorry I cannot find that thread on the forum.

 

[RIK]

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