Battery pack question.

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NL_Fer
NL_Fer
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Re: Battery pack question.

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Heating?

Would the savings of offgrid electricity outweight the cost of heating with gas bottles? Vs heating with airconditioners running from gridpower.

Greg Locock
Greg Locock
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Joined: Fri Jun 29, 2012 11:48 pm

Re: Battery pack question.

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If you are off grid the best way to heat your house electrically is with a heat pump, effectively a reverse cycle air conditioner. A heat pump heater is the most energy efficient electrical means of getting hot water.

However in practice they both consume large amounts of energy and you are probably better to rely on bottled gas for heating and hot water. A 45 kg LPG cylinder lasts the two of us about 4-6 months, but in winter we do rely on two woodstoves .

In my off grid house I have 1.5 kW of panels and 20 kWh of lead acids (plate capacity, 6 kWh usable), so realistically I can go a couple of days without sun before needing to start the genny. My electric chainsaw, saw table and some of the big pumps are only run in winter if the sun is really blazing down or the genny is running. In the depths of winter I tend to run my diesel genny for an hour or two most days. I should install more panels.
Last edited by Greg Locock on Thu Apr 26, 2018 11:34 pm, edited 1 time in total.

AJI
AJI
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Joined: Tue Dec 22, 2015 8:08 am

Re: Battery pack question.

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Manoah2u wrote:
Thu Apr 26, 2018 2:13 pm
...what battery power (volts, amps, and all that is needed to know) would i need to simultaneously use all my home appliances together :

- washing machine ( saw a eco Zanussi that runs on 800 watts, buying price only 300 euros)
- salora 32" Led TV + soundbar ( 30 watts + 30 watts = 60 watts )
- AEG table-sized refrigerator ( 7 watts with 70 watts peak )
- Exquisit freezer table model ( 11 wats with 90 watts peak )
- ECO fan (40 watts)
- HP 17 inch laptop (45 watts)
- ECO coffee machine (450 watts)
- Microwave (600 watts)
You need to simulate duty, and an easy way to find out how much capacity you need is:
Buy all of the above, simulate living off-the-grid (while on-the-grid) and read the meter every day for as long as you can.
Once you have that data quadruple the average and you're pretty much there.

Greg Locock
Greg Locock
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Joined: Fri Jun 29, 2012 11:48 pm

Re: Battery pack question.

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Alternatively, spend 20 bucks on an energy monitoring plu, plug that into an extension cable and live off that extension cable (that's actually pretty much like living in an off grid house anyway).

The big short term draws are your microwave and toaster, but most of the energy goes into the fridge freezer.

We use about 4 kWh a day of which a surprisingly large amount is our (satellite) internet.

Manoah2u
Manoah2u
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Re: Battery pack question.

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NL_Fer wrote:
Thu Apr 26, 2018 10:42 pm
Heating?

Would the savings of offgrid electricity outweight the cost of heating with gas bottles? Vs heating with airconditioners running from gridpower.
heating and cooking are 2 different things.

i would use the stove with gas bottles - if i'd go offgrid and it is worth it. question is if it in the end is, but that aside.

heating is another question alltogether. if we're talking about a central heating system, that's where i need to investigate a lot. i can't find worthwile information. the houses i've ran across already have central heating, some have airco, some don't. airco usually runs from what i've read about 1kw in operation. does that same go for central heating? i don't think so, modern central heating units can operate at 100% efficiency believe it or not, but still consume a 'hefty' amount of energy.

i would need to look more into heat exchangers (heat pumps), as those are rather interesting too, though it must be said they share a concept that airco has aswell, but airco's are far from 100% efficient and i'm not sufficiently informed about 'heat exchangers' nor it's price tag.

i'm confident though that heating your house with airconditioning from the grid is more expensive than running central heating systems from the grid. if that also includes gas, i'm doubtfull. i believe gas is also rather 'expensive' in spain but i could be mistaken.

apart from that, most have fireplaces, and quite frankly, i'm very positive towards that. a trip to the mountains where there is a lot of wood for sale for cheap i expect is cheaper, but like everything, i'm gonna have to calculate, and i'm taking my time to find out everything. but offcourse, heating is very important to take into the equation, that's for sure.

@AJI,

why quadruple the average? would like to know the maths behind that. i understand it has to do with the battery, but would like to know how to get those figures.
Dumpster sounds so much more classy. It's the diamond of the cesspools.

AJI
AJI
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Joined: Tue Dec 22, 2015 8:08 am

Re: Battery pack question.

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Quadruple was the rough number for my setup. It calculated out at 2.7, but it wasn't enough if I had a week of bad weather. Oddly enough you get storage-anxiety. I'm sure it's no where near as bad range-anxiety, but turning on the diesel generator feels like failure.
Ideally I'd like a 200kW solar panel setup, 16kWh of battery storage and Tesla P100 which powered the house for auxiliary power.
Everything is dependent on your position on the face of the planet, solar panel position and efficiency, whether they are sun tracking, average weather and cloud coverage, how many other sources you use for heating/cooling, etc... But mostly, how conscious other members of your household are of energy consumption...
The calculations can be quite involved and you need years of data to get it right, but I'm pretty happy.

Manoah2u
Manoah2u
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Re: Battery pack question.

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AJI wrote:
Fri Apr 27, 2018 12:34 am
Quadruple was the rough number for my setup. It calculated out at 2.7, but it wasn't enough if I had a week of bad weather. Oddly enough you get storage-anxiety. I'm sure it's no where near as bad range-anxiety, but turning on the diesel generator feels like failure.
Ideally I'd like a 200kW solar panel setup, 16kWh of battery storage and Tesla P100 which powered the house for auxiliary power.
Everything is dependent on your position on the face of the planet, solar panel position and efficiency, whether they are sun tracking, average weather and cloud coverage, how many other sources you use for heating/cooling, etc... But mostly, how conscious other members of your household are of energy consumption...
The calculations can be quite involved and you need years of data to get it right, but I'm pretty happy.
great to hear. i'm delving into some youtube videos now on DIY tesla battery pack kits, with people actually making very powerful 18650 battery packs providing 20kWh power 'banks' for only 300 bucks. what i don't have answered there yet though is the lifespan of these batteries. if they can last about 5 years, it might be the border. 10 years would be very practical. if i could make a 40kwh energy storage for only 600 bucks, i'm starting to get very excited to go and make it. just youtube it.
but again, i'm going to write down and document all the numbers, and all the benefits and setbacks of which battery.

for example, some questions raise for me;

if you have the option to combine a good load of lead-acid batteries, or you can combine a whopping load of 18650 batteries, for more or less the same price, what would be better? do lead-acid or perhaps liquid gel batteries, live longer than 18650 batteries? aren't 18650 batteries actually what's used in laptops and even tesla car batteries?
Dumpster sounds so much more classy. It's the diamond of the cesspools.

NL_Fer
NL_Fer
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Re: Battery pack question.

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Image

Lead acid has a very short lifespan if you discharge them. They are propable waisted in 3-5 years when cycled for 100 -> 50% s.o.c. every day.

For minimal wear lithium is best kept between 30-80% s.o.c. . full top up or total discharge is causing most wear. Tesla’s are guaranteed for 8 years with good battery management: Keep soc between 30-80% and temperatures between limits.

Also there are very much brands of 18650 cells. Some are cheap, but the high quality brands like Panasonic are expensive.

AJI
AJI
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Joined: Tue Dec 22, 2015 8:08 am

Re: Battery pack question.

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18650 all the way, but $300 for 20kWh sounds a bit unrealistic. If it's true I got ripped off!
I guess if they're making them out of old stock, maybe..?
Either way, if you can get 20kWh for $300 jump on it. Even if they only last a couple of years you're way ahead of me!

Greg Locock
Greg Locock
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Re: Battery pack question.

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Perhaps the story got lost in translation, $300 per kWh sounds more likely.

AngusF1
AngusF1
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Re: Battery pack question.

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I recently performed a similar task for work, although not for a house. As an example let's say you want to provide power for 2 people with storage for a week, in a location which gets cold in winter.

1. Decide how much ENERGY you need each day. Typical units in this application are KiloWatt-Hours (kWh). Typical Western usage can be around 5kWh per day per person.
2. Decide how many days of storage you want, and hence decide how much total storage you need. Energy per day * number of days = total energy. For example, 10kWh per day * 7 days = 70kWh.
3. You can't draw the batteries down completely without damaging them, so you need to increase by a minimum of around 20%. 70kWh + 20% = 84kWh. The battery manufacturer will provide this specification.
4. Take into account the lowest average temperature the batteries will experience throughout the year, as batteries function poorly at low temperatures. The precise factor depends on the actual batteries you purchase - the manufacturer will provide data. For example let's say in Winter the daily average temperature is around 5 degrees, this could add about 50% to the requirement. 84kWh + 50% =~122kWh of installed battery capacity.

We used this brand of batteries for my project. http://www.sunxtender.com/battery_sizing.php Note that they seem to combine steps 3 and 4 in their example calculation.

5. Determine how much solar panel capacity you need to charge the batteries. Solar panels are typically rated by the maximum POWER they can produce in full sunlight. POWER = ENERGY / TIME. Typical units: Watts (W). This is difficult to calculate and is heavily dependent on your latitude and cloud cover. Most solar companies use special software to estimate the requirement in your specific location. As a rough example let's say the sun shines perfectly for 4 hours per day. To obtain 124/7 = 17kWh in 4 hours you would need about 4kW of solar capacity.

Then figure out how much it will all cost...
Good batteries cost ~$200+ per kWh. 122kWh * $200 = $24,400.
Solar panels cost around $1 per W. $1W * 4000 = $4000.

So you have $30,000 USD for batteries and panels. Then consider shipping, electrical cabinet, inverter, installation and wiring, permits, paperwork, labour etc. You then need to figure out how long the batteries are going to last.

You'll see that this quickly gets expensive if you want significant storage in a cold climate. You may prefer to have less storage and run a generator with wood or gas heating in winter. It's definitely a lot easier to afford these solar setups for a holiday house which you only go to occasionally for a weekend than for a permanent house with your wife and kids who expect hot water and lighting 24/7 every day of the year. Then again, I guess that depends on how much the local electricity company wants to charge you for a connection.

Also don't forget to take the efficiency of the inverter into account.

Don't get confused when looking for batteries - they are usually quoted in Amp-Hours (Ah), not kWh. To get kWh from the Ah, you need to multiply the Ah by the Voltage (V) of the batteries. For example, a 12V battery rated at 100Ah has a storage capacity of 1200 Wh, or 1.2kWh.

AngusF1
AngusF1
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In summary, you're thinking about the problem the wrong way around. You need to determine your energy requirement, storage requirement and loss factors, then specify the solar panels based on your location.

NL_Fer
NL_Fer
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Re: Battery pack question.

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I can find 3400mh cells for about 3-3,5€, that is about 10wh. 300-350€ per kwh

An lead acid AGM battery is about 150€ for 1kwh.

Manoah2u
Manoah2u
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Re: Battery pack question.

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AJI wrote:
Sat Apr 28, 2018 5:53 am
18650 all the way, but $300 for 20kWh sounds a bit unrealistic. If it's true I got ripped off!
I guess if they're making them out of old stock, maybe..?
Either way, if you can get 20kWh for $300 jump on it. Even if they only last a couple of years you're way ahead of me!
less actually, 300 bucks was including a hundred dollar glass cover for the wooden construction that also cost money to mount the battery pack in, simulating a tesla wall.

though i didn't see actualy proof of spending, i take the story as being honest.

the note that must be said, is that those batteries are not new but second hand. he managed to get his hands on a lot - and i do mean a lot - of discarded / 'dead' laptop batteries, which he then disassembled to take out the 18650 batteries inside (9 in every battery pack). then took the effort to measure which batteries were fine and which not (time consuming obviously) and discarded the bad ones and saved the good ones.
mentioned that the laptop battery protective chip is built to recognise power fluctuations between batteries, so from the 9 batteries in each pack, if 1 is faulty, or the chip itself, the batteries decides to quit and gets replaced under warranty normally and that leaves a 'discarded' (scrap) battery which in many cases actually is far from worthless.
he had 600 well usable 18650 batteries for his system.

if i had to calculate that 300 bucks minus 100 bucks for the glass cover, i forgot the wood paneling (plywood), let's say 20 bucks, so 180 bucks for the batteries. each pack has 9 batteries, so 600 batteries divided by 9 equals about 66 to 67 laptop battery packs atleast. that means me might only have paid 3 bucks for each discarded laptop battery. after all, 3 bucks x 67 batteries equals about 200 bucks so if he's being honest........that's a amazing deal.

so the biggest game here would be to get ones' hands on enough laptop battery packs. let's say half of the cells in the battery packs in itself actually can't be used, so then let's say 130 laptop batteries would be required for the 'system'.

now where and how to get me hands on a grand total of 130 laptop batteries that are 'dead' ? i might know some ways though. question is, how much is that going to set me back. if 3 bucks are anything to go by, then i'd calculate i'd need to spend 400 bucks for 130 laptop batteries. that would be a directive.
laptop batteries are the preferred direction as there are many crappy 18650 batteries from china that don't even produce a tenth of promised output, so the advise is sony, lg, etc. etc. a-brand batteries over 'unknown' brands.

i've seen offers that go as low as 0,65 euros for a single 18650 cell but repetitively, those exist of non a-brand cells, so quite frankly, completely useless.

but again, indeed, as mentioned,
i've seen lead acid batteries that have 100 amps or more for about 150 euro's, as another poster mentioned above.
so i'm in between on what would be the right decision then.

it's said those 18650 batteries need to operate between 40% lowest and 68 to 70% tops in charging and depletion to get most life out of those cells. likewise, leadacid batteries don't really enjoy being depleted either, so i'd say fair treatment would hold the same number.
thus again - taking in concideration the standard average figures for wear and lifespan, energy loss, and combining that with investment, not the least mentioning 'practicability' of replacing a cell/unit, and also taking in concideration the specific battery's 'danger' (leadacid is dangerous in different ways than lithium-ion batteries, but then there are also 'traction batteries' and 'gel' batteries (still lead acid if i'm correct, but without the need to refill), which claim are actually fully 'safe'.

i've already seen computer server rack housings as little as for completely free up to 30 bucks for a 180cmx80x80 cm including cooling fan array on top, made out of metal and covered in weatherproof paint which can theoretically sit outside but i'd go and set it in the garage anyway. another option would be second hand electricity rack housings in similar or smaller sizes for similar prices, but are factory-made to be mounted outdoors.

as a safety measurement, outside of a complete kill switch (which should also be controlled through sensors), i want to look into 'extinguishing' measurements. water obviously isn't the smartest move i'd say so i'm going to need to look into other extinguishing measurements in the case of short-circuiting, (small) fires, or potential leaking of either lead-acid or lithium-ion leakage. safety over taking a potential risk any time.

btw i'm not at all in the position to assume or think you 'might' have been ripped off, as in all reality, i'm gathering theoretics, not personal experience or touchable evidence. I only have accounts of multiple youtube testimonials which are supported by evidence (though not 100% waterproof), and own googling through ebay, online stores, and traders. which does however paint a picture of what is reasonable to expect. still, a lot of routes to go.

for example, i head out repetitively to the dominican republic, and due to the countries well-known power outages, a good amount of homes run on backup power through 12v or 24v lead-acid batteries, which power only the absolute neccesites like the refridgerator, 1 or 2 fans, and some 12v appliances. more than 1 opt for diesel generators, but that's something i'm rather trying to avoid. offcourse safety measurements over there are vastly different (minimal, if any :mrgreen: ) over there, and same goes for the energy bill :mrgreen:
the lead-acid batteries offcourse then are a proven concept, BUT demand there is vastly different too. let's call it different way of life. solar panels over there then again are costly and a costly investment, especially concidering the amount of theft and....cough....cough....law enforcement over there.

still, any reliable info i can base my calculations on are worth noting, so thanks guys for sharing this vast wealth of information. 8) 8)

who knows it may lead to something we can all benefit from :P
Dumpster sounds so much more classy. It's the diamond of the cesspools.

AJI
AJI
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Re: Battery pack question.

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@ Manoah

Wow! I've never thought about dead laptop and even power tool batteries, but yeah, they're right. There's generally only 1 or 2 dead cells and the system goes into 'time for a new battery' mode.
Go for it! It sounds very time consuming, but the value is amazing even if you only get a year or 2 out of the pack.
I did a bit of research and it looks like Tesla fuse each individual cell, which is smart. I'd highly recommend this. Your fire control ideas sound sensible to me. 18650's are very safe, but a thermal runaway situation in a single cell could be catastrophic...
On a slightly different note I converted an old clubman go kart to electric recently for a bit of fun. I used Li-po packs, 30 of them in a 15s 2p configuration. The pack weighs about 4kg and only has 610w hours of capacity (that was $300), but it'll burst 24kW (which is more than twice the capacity of the peak output of the motor). The thing flies and the torque is incredible!