Battery pack question.

[AJI]

@Manoah

One thing I forgot to mention is that my system is 12v DC and 240v AC.
It means running a lot of heavy cable and in some places it's duplicated, but anything I can run natively on 12v DC runs on those circuits (lights, ventilation systems, pumps, etc..) to maximise efficiency (there are a lot of useful things you can steal off cars for your house and workshop), and the rest runs off the inverter.

[Greg Locock]

Mine is 48V. Running 12 V would mean a lot of thick cables, WAG about 100 mm^2 cross section. My panels are distributed across 3 buildings.

[AJI]

Mine is 48V. Running 12 V would mean a lot of thick cables, WAG about 100 mm^2 cross section. My panels are distributed across 3 buildings.

I'm lucky. I've got a huge roof area that faces due north, has no shadowing, has the perfect inclination for solar collection at my latitude and the maximum 12v cable run is about 15m and that circuit is only for low load lighting.

[Andres125sx]

I´m not sure about recylcing batteries from different appliances. First rule of thumb for big battery packs is all cells must be equal on voltage, capacity and use, but with different batteries there will be differences for sure. Also with cheap 18650 batteries you can´t even know real capacity, so I´m not sure about what will happen when lowest capacity cells are fully charged but highest capacity cells are lowering the average voltage readings

Just for reference, most affordable price for lipos I´ve found is around $410/kWh, those are 6s 22.2v (21-25.2v) 12Ah.

There´re also some on sale wich are $320/kWh, these are 6s 22.2v 10Ah


I don´t have an opinion about what battery is the most suitable for this, all of them have their drawbacks.


About safety, this may not work for karts, a bit on the heavy side , but it´s the safest and also cheapest system I´ve ever seen for home



In case of a fire the block will contain the fire while this will melt the plastic bag and the sand will extinghish it

[AngusF1]

This idea sounds totally hare-brained and likely to reduce your house to ashes, I would suggest buying new batteries designed for the purpose.

The basic problems are that you have no idea what the life or condition of the batteries is, and the more you have the more likely it is that one will catch fire.

[Andres125sx]

also, there's a 10kW 'treshold' - below 10kW you are essentially 'free as you wish'. (per day or per hour i'm not certain any more).

Neither of them, it´s 10kW, power, it doesn´t matter if for 10 minutes or constant for 10 months. It is a fuel flow limiter not a tank restriction

[Bloque 11: #a7]

No obstante lo anterior para los consumidores acogidos a una modalidad de autoconsumo tipo 1 que tengan contratada una potencia inferior o igual a 10 kW y que acrediten que cuentan con un dispositivo que impida el vertido instantáneo de energía a la red de distribución estarán exentos del pago de los estudios de acceso y conexión

type 1 refer to consumers who do not sell electricity to the grid

[Andres125sx]

Off-grid systems are exempt from complying with RD900/2015 ("Impuesto al sol" law)

[Bloque 4: #a2]

2. Se exceptúa de la aplicación del presente real decreto a las instalaciones aisladas y los grupos de generación utilizados exclusivamente en caso de una interrupción de alimentación de energía eléctrica de la red eléctrica de acuerdo con las definiciones del artículo 100 del Real Decreto 1955/2000, de 1 de diciembre, por el que se regulan las actividades de transporte, distribución, comercialización, suministro y procedimientos de autorización de instalaciones de energía eléctrica.

[Andres125sx]

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?

For same price I´d go for 18650 batteries, at least if they´re from a reliable manufacturer, and that´s a big if.

If they´re laptop batteries collected from different sources, no way I´ll risk a fire at home to save some money

Lead acid batteries are safer, cheaper but can´t use the full capacity or the battery longevity will be shortened. They also suffer a noticeable self-discharging rate

Lithium batteries (18650, lipo, LiIon...) are more dangerous (IMHO it was only some problems on early batteries more than a decade ago) and suffer when fully charged or discharged, but have better energy density and better longevity. Almost negligible self-discharging rate. I always try to keep my mobile battery in the 20-80% range for long term longevity, and people usually get surprised when I say I´ve never replaced one single battery, not even on a mobile I used for more than 4 years. But when you need to use the full capacity, you can use it without damaging the battery, unlike lead-acid wich will get some irremediable damage if discharged below 30% more or less just one single time


In that sense, A123 batteries should be a better match (they can be discharged to 0 volts with no problems), but there must be some drawback with those

[Manoah2u]

Andres thanks for the reply in regards to spanish law

Just for certainty, am i reading right then that
A > if you're off-grid, you don't need no tax in any way, whatever the case
B > so essentially, i can have enough solar panels that generate right below 10 kW 'the restriction', and for example store that in a battery set 'the tank' to infinite, so, theoretically, 10 hours of sun, everything works nominal, i have enough batteries to store, and the net energy produced and stored at the end of the day is 100 kW (or, atleast, 99.99 kW.)

in other words, i can have 5 airconditioning units running, fridge, freezer, computers, batteries charging, tv, all on, as long as i'm keeping SOLAR consumption under 10kW, and additionally, i could pull 10kW from the energy grid?

BUT do i in every case need the permits fixed?
that's where i'm still in the blind spot.

do i need permits and 'legislation' (administration) done if i stay under 10kW, or do i need to have that anyway,
and does that ALSO go if am off-grid or would that only apply on-grid?

[Manoah2u]

@ 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!

great to hear the fun with the kart.

Yes, i'm looking into several safety appliances. i've seen fuses on every battery, and also fuses in every row of either parallel or series connected applications, which were paired to a temperature sensor 'fuse' which measures temperatures in real-time and exceeding a certain treshold will 'cut' power, so that would be a fantastic means anyway. personally i'm looking into 'devices' or 'sensors' rather that operate within a measurement, for example; 3.2 volts the led turns red, and above 4.0 volts the light turns red, within 3.2 and 4.0 volts the light stays green.
if there's some way i can find - or make/solder - something like that, then that would be fantastic as if i could mount that to every battery i could immediately see if a battery needs replacement or not. it probably would turn out costly though. hell, it would already be great if i could do that for every 10 batteries.

and yeah, i'm planning a visit to various car junkyards for battery leads/cables.
i've also gotten the tip to simply look for wiring in your house, for example, outdoor cables.

also gotten the tip to simply drive to a construction site where they're building (prefab) houses and working on electricity wiring and simply ask some guy to cut me 10 meters of cable for a crate of good beer. they've got an excess of cable anyway and well.....they usually really like beer

as for the supposed hare-brained fire-risky stuff;
i'm not that worried, as fact is, i do know how to know the capacity, and i do know how to measure actual capacity by simply 'measuring' it with the tools required.

and i'll repeat; stay within the designed operating window (3.0 volts minimum, 4.0 volts maximum) and you're just as safe as for any application. and then there's the sensors that read the rest of the information you want and paired to fuses and other cut and kill switches, you're fine.

[AJI]

This idea sounds totally hare-brained and likely to reduce your house to ashes, I would suggest buying new batteries designed for the purpose.

The basic problems are that you have no idea what the life or condition of the batteries is, and the more you have the more likely it is that one will catch fire.

It's not really hare-brained. It's not that difficult to test the condition of the cell or its capacity, it's just time consuming. Extracting the cells is also not an easy feat. I had a go yesterday on a dead laptop battery and it took me 30 minutes just to open the pack. The cells were spot welded and leave very little room for error during extraction. Still, I did it, and there was only 1 dead cell...
I'm in the process of testing them now, but all signs point to

Now I just have to do it 5000 more times...

[Zynerji]

You can buy Prius that is totaled on erepairables for about 500. Would it be worth buying 2-3 to harvest the batteries for something like this?

A Toyota Prius battery, by the way, contains 168 1.2-Volt nickel-metal-hydride cells, which contain a total of 1.6 kilowatt-hours of energy. Its peak power output is 27 kilowatts, or about 36 horsepower.

Or maybe one of the lithium batteries from other manufacturers...

[Andres125sx]

I really like the Prius battery idea. They´re equal cells with equal use, and NiMh chemistry is IMO better for this than lead-acid or lithium batteries as they can be kept fully charged without damage (unlike lithium batteries), can be fully discharged without major damage (unlike lead-acid batteries) and also can be balanced just keeping a <C/10 charging rate without dismantling the pack (unlike lithium, not sure about lead acid)

[Andres125sx]

Andres thanks for the reply in regards to spanish law

Just for certainty, am i reading right then that
A > if you're off-grid, you don't need no tax in any way, whatever the case
B > so essentially, i can have enough solar panels that generate right below 10 kW 'the restriction', and for example store that in a battery set 'the tank' to infinite, so, theoretically, 10 hours of sun, everything works nominal, i have enough batteries to store, and the net energy produced and stored at the end of the day is 100 kW (or, atleast, 99.99 kW.)

in other words, i can have 5 airconditioning units running, fridge, freezer, computers, batteries charging, tv, all on, as long as i'm keeping SOLAR consumption under 10kW, and additionally, i could pull 10kW from the energy grid?

BUT do i in every case need the permits fixed?
that's where i'm still in the blind spot.

do i need permits and 'legislation' (administration) done if i stay under 10kW, or do i need to have that anyway,
and does that ALSO go if am off-grid or would that only apply on-grid?

The law stablish two figures, consumer and producer. Consumer is anyone who use grid electricity. Producer is anyone who produce electricity wich goes to the grid. Based on this there are 3 scenarios.

Type 1 (according to the law): Consumer
Type 2 (according to the law): Consumer and producer
Type 3 (not covered by the law): off-grid, so you´re not a consumer nor producer as you have no connection to the grid

Type 1: does need to comply with the law (instalation certificates) but only need to pay taxes if energy production or grid contract is > 10kW
Type 2: does need to comply with the law and pay taxes
Type 3: does not need to comply with the law and do not have to pay taxes

At least that´s how I read it, but I´m not a lawyer

[Manoah2u]

prius cells might be interesting,

but tesla model S cells are just as salvageable by now. renault zoe models have battery rent contracts, so they're hard to come by unfortunately but i don't know if they use the same batteries. i think they do though.
renault leaf batteries. plenty to go around.