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Lithium battery €200 for 2kWh. Will we DIY?

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  • 31-05-2019 1:11am
    #1
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭


    Just spotted this:

    Linky

    4 times 5Ah 18650 battery for €8.26, free shipping

    Did a quick calc, so you can buy 26 of these packs, for a 104 cell, 13s8p battery with 3.7V * 13 = 48.1V and 8 * 5Ah = 40Ah

    So 48.1 * 40 = 1.924kWh capacity (usable about 1.75kWh)

    That's just the cells though. Let's play. What else is needed, please share your links and your experience. Preferably keep this at n00b levels. No spot welding, no soldering if possible. How do you build a battery pack (with or without BMS?) with these cells as cheaply as possible for someone with very low DIY skills.


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    #2
    reklamos
    Registered Users Posts: 793 ✭✭✭reklamos


    I would not start this if you're at n00b level. I'm sure you already googled for DIY powerwall and there are a lot of things required to get this running properly and even then you are not 100% when one these gonna go up in smoke. The phrase '...as cheaply as possible for someone with very low DIY skills...' is only looking for trouble.


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    #3
    the_syco
    Registered Users Posts: 37,295 ✭✭✭✭the_syco


    18650 batteries are usually around the €10 mark for decent name brand batteries (I use them for vaping). These are at "cheap chinese tat" prices, and thus I'd be worried that they'd blow when charging, as cheap batteries usually have no safety tech built into them to prevent them blowing up. Something to consider, at the very least?


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    #4
    n97 mini
    Registered Users Posts: 8,295 ✭✭✭n97 mini


    There's no way they're 5000mAh. The largest capacity name brand cells are ~3600mAh.

    Google for 5000mah 18650 and you'll find plenty of hits showing semi-branded (e.g. UtraFire) batteries labeled as 5000mAh, but are actually less than half that.


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    #5
    n97 mini
    Registered Users Posts: 8,295 ✭✭✭n97 mini


    Worth a watch

    https://www.youtube.com/watch?v=yZdf5rv0s7o


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    #6
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    Maybe they're not anywhere near 5000mAh. In fact it would be very helpful if they weren't. Buy them, pay with PayPal and enter a dispute if the supplier is not refunding you. You'll get your money back if they are bad. Most likely you will get to keep the batteries too :D

    I stopped watching that video when I realised he gives out about his cheap charger "overcharging" his 18650 by 0.5V. It's supposed to do that. A 3.6V-3.7V nominal 18650 can no problem be charged up to 4.1V or even 4.2V

    Now I wouldn't buy these 18650 cells to build myself a powerwall costing thousands that I would expect to last 20 years. I wouldn't buy any 18650 cells for that and I wouldn't spend serious money on DIYing it. I would buy off the shelf with a warranty. But they are far too expensive still for my liking


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    #7
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    Alternative supply from a professional recycle centre. €75 for 100 18650 used and with tested and guaranteed capacity of a bit over 2Ah (again eBay and PayPal for peace of mind)

    Linky


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    #8
    n97 mini
    Registered Users Posts: 8,295 ✭✭✭n97 mini


    unkel wrote: »
    I stopped watching that video when I realised he gives out about his cheap charger "overcharging" his 18650 by 0.5V. It's supposed to do that. A 3.6V-3.7V nominal 18650 can no problem be charged up to 4.1V or even 4.2V

    I didn't watch closely, but I thought he was complaining that his cheap charger is dumb. Basically it just supplies constant power to the battery, regardless of SOC. Eventually the battery will be fooked.


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    #9
    n97 mini
    Registered Users Posts: 8,295 ✭✭✭n97 mini


    unkel wrote: »
    Alternative supply from a professional recycle centre. €75 for 100 18650 used and with tested and guaranteed capacity of a bit over 2Ah (again eBay and PayPal for peace of mind)

    Linky

    I had actually spotted these a few days ago, with a view to using Jehu's DIY PCB. But... I watched one of his videos and the lugs in the battery holders were getting mad hot (as there isn't enough contact area), so I don't consider it a good solution. I don't mind soldering, been at it for 30 years, and 18650s are pretty easy to solder wire to, but I'm put off by the sheer amount of soldering, and then the pricking around if bad cells have to be removed. His PCB seemed like a solution to this pricking around but, as I said, they seem to have heat problems. And with higher power cells, the problem is potentially going to be worse.

    I'm pretty sure I'm going to stop looking into the Li-ion rabbit hole. A £300 (ebay) GoodWe GW2500-BP DC Charge Controller combined with 4 or 5 recycled AGM car batteries (free) looks like it might do the trick. I kept the old AGM battery from the Ampera, so only a few more to go :)


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    #10
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    I happened to have one of those cheap chargers myself. Must have got it when I bought my headlight (with 2 * 18650) for night hiking a few years ago. I ripped open a few dead laptop batteries this week and the charger charged those batteries perfectly (to about 4.15-4.21V) although it took a long time with some of them. LED light is red while charging and it turns green when it has stopped charging

    I can solder (at beginner level) but I don't want to solder 18650s for the same reasons as yourself. That's why I thought the Jehu system would be a nice alternative. Any link to his vid where you saw them get hot? Any suggestions for alternative non soldering kits?

    BTW I'm looking into AGM batteries myself, comms ones :D


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    #11
    n97 mini
    Registered Users Posts: 8,295 ✭✭✭n97 mini


    I had a quick look and I can't find the video. Jehu has a lot of videos! But I know from past experience that poor contact is probably the biggest cause of fires in electrical equipment. I've had a couple of them myself. Nothing serious, but enough to learn a lesson.

    If you're determined to go down the Li-ion route, I'll do the soldering for you, but the troubleshooting will be your job! :)


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    #12
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    Nah not determined. Would be just as a little project really. Wouldn't charge or discharge the battery in the house anyway. Either in the shed or outside the house against a stone wall. Thanks for the offer though :)

    From some videos it looks like the proper way to connect them is by spot welding them. Seems to be far easier than soldering too. I would just buy a cheap spot welder but you'll like this - DIY spot welder made for just a few euro :D

    https://www.youtube.com/watch?v=o1NFbchHeM8


    I have plans for a big battery. But it will be lead. Unless off the shelf lifepo4 batteries would come down in price big style in the next few months. But as regulars of the EV forum you and I both know that's not going to happen


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    #13
    n97 mini
    Registered Users Posts: 8,295 ✭✭✭n97 mini


    That's very cool, kudos to yer man in the vid.

    But I'd still have reservations about contact area. Combined with the fact that soldering is probably easier (assuming you have an iron) and provides a bigger contact area, I think it's the way to go.


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    #14
    SlowBlowin
    Registered Users Posts: 1,884 ✭✭✭SlowBlowin


    Soldering an 18650, unless it has tags, is very difficult to do as the cell dissipates the heat. If you do get a joint its often a bad one. A good temp controlled iron, running very hot, is required.

    Hey Unkel, in case you missed my post on the HR thread, here are the cells I am using (very untidy)..

    battery.jpg


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    #15
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    Nice! What exact model are they and how much did you pay for them? You use them off grid with solar PV, or what's your setup?


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    #16
    rolion
    Closed Accounts Posts: 3,362 ✭✭✭rolion


    We should keep a history of this thread here... how do not play with fire !
    Guys,make sure you have a good and valid home insurance,with small printing covering small DIY games.

    I know you didnt asked for my advice but please... stay away or play safe !
    Not worth it,riskwise and financial,not talking about RoI.
    I see it just something to keep your mind occupied,busy.
    Spend quality time,get a proper battery system with good validated cells and a certified BMS.


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    #17
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    Thanks for your concern, rolion :)

    I have no plans to do any soldering or welding on batteries myself and any battery system I will get or build will live outside of my house
    rolion wrote: »
    get a proper battery system

    Just buy a LiFePO4 battery off the shelf? Too boring and expensive for me I'm afraid...


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    #18
    rolion
    Closed Accounts Posts: 3,362 ✭✭✭rolion


    unkel wrote: »
    Thanks for your concern, rolion :)

    I have no plans to do any soldering or welding on batteries myself and any battery system I will get or build will live outside of my house



    Just buy a LiFePO4 battery off the shelf? Too boring and expensive for me I'm afraid...

    Thank You ... i was really worried about your endeavour...

    Re batteries,i am not the most qualified person to say your next step,sorry,i am just waiting for better times and few more LEAFs to drop off the street on second hand market. Once they are under 2k and a bit more than 1k,then maybe...

    Take care.


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    #19
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    rolion wrote: »
    Once they are under 2k and a bit more than 1k,then maybe...


    They already are.

    A 2.4kWh Pylontech off the shelf battery with built in BMW costs less than a grand. Add an inverter (I paid GBP400 shipped for mine), connect it all up and you have your battery system for about €1.5k if you do it DIY and have a friendly electrician who won't charge you to connect it to your consumer unit.


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    #20
    SlowBlowin
    Registered Users Posts: 1,884 ✭✭✭SlowBlowin


    unkel wrote: »
    Nice! What exact model are they and how much did you pay for them? You use them off grid with solar PV, or what's your setup?

    The cells are 2YS31P from Rolls battery.

    bat4.jpg

    http://rollsbattery.com/battery/2-ys-31p/

    They are good for well over 3500 Ah at the rate I am pulling from them. I bought them new, can't remember how much I paid (it was much more than a Tesla powerwall costs but thats progress for you). Slight hernia bring them up the mountain...

    I have 2 inverters connected, a 800 watt sine wave Victron and a 2.2KW sine wave Studer (more efficient to have 2).

    On the input side I have 24 x 100 watt Solara PV panels. These are fed through two Morningstar MPPT60 controllers, I logged into one just now and have enclosed the screen shot, since I last reset it (some years back) it has generated 2 mega watt hours, the other one should be the same.

    mppt.jpg

    Because I live high up on a mountain in Kerry windmills are an issue, most people who install find them in bits after a few storms, but I am planning to install a Marlec 1200 later this year (on a tower that can be bought down easily if metorite58 says so), at the moment I am working on the hydro/pumped storage. We have a number of small streams on the mountain and I am currently trying to clean them up a bit which should take most of the summer.

    The whole system is then controlled by a PC which is on 24/7 powered of the system. The software monitors everything and determines where the power best go, e.g. if the battery is full and the lounge is not too hot and power needs using it switches on small electric heaters. 7 years ago the system used to power cryto mining rigs to generate heat and value in the house, but I stopped that about 5 years ago now excess power is dumped to heaters and lights in the poly tunnel.

    By the way coming back to the original comment with cells this big soldering is out of the question, indeed I have learnt that soldering is no good at all where large currents are involved. In industry all high current cables are crimped, and I know why from my own mistakes. When my system is charging at 120 amps


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    #21
    rolion
    Closed Accounts Posts: 3,362 ✭✭✭rolion


    unkel wrote: »
    They already are.

    A 2.4kWh Pylontech off the shelf battery with built in BMW costs less than a grand. Add an inverter (I paid GBP400 shipped for mine), connect it all up and you have your battery system for about €1.5k if you do it DIY and have a friendly electrician who won't charge you to connect it to your consumer unit.

    I was hoping for a LEAF battery system not cheapie and smalller capacity.
    A LEAF at 24KW listed capacity but with minim 70% health will do me for couple of years. All in DIY regime and very easy and safe.


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    #22
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    SlowBlowin wrote: »
    The cells are 2YS31P from Rolls battery.

    Impressive setup!

    I thought those were the cells alright, but it didn't make sens that you'd install a 12V solar PV off grid system. But now you've explained I presume you have the system a good few years now and your solar panels are probably 12V, hence your 12V battery. I guess you have spent a fortune on cabling alone with those amps :D

    What's the lowest voltage you allow your battery bank to be?

    Somebody who knows their stuff told me Studer make excellent inverters and the Morningstar Tristar MPPT is the best solar controller there is bar none

    I'm using some of the excess of my own PV also for crypto mining, but with the summer coming, the heat is no longer needed in the house, so I'm going to quit soon


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    #23
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    rolion wrote: »
    I was hoping for a LEAF battery system not cheapie and smalller capacity.
    A LEAF at 24KW listed capacity but with minim 70% health will do me for couple of years. All in DIY regime and very easy and safe.

    You could pick up a Leaf battery for reasonable money a few years ago, but that ship has long sailed. The prices they go for on eBay these days is simply crazy.


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    #24
    SlowBlowin
    Registered Users Posts: 1,884 ✭✭✭SlowBlowin


    unkel wrote: »
    Impressive setup!

    I thought those were the cells alright, but it didn't make sens that you'd install a 12V solar PV off grid system. But now you've explained I presume you have the system a good few years now and your solar panels are probably 12V, hence your 12V battery. I guess you have spent a fortune on cabling alone with those amps :D

    What's the lowest voltage you allow your battery bank to be?

    Somebody who knows their stuff told me Studer make excellent inverters and the Morningstar Tristar MPPT is the best solar controller there is bar none

    I'm using some of the excess of my own PV also for crypto mining, but with the summer coming, the heat is no longer needed in the house, so I'm going to quit soon

    The panels are 12v but they are wired in series, the parallel, as they are MPPT controllers. In that picture on the previous post you can see the array was at 71 volts, but its often different. As the controllers are next to the cells I dont need much heavy gauge wire, the interconnect wire is about the width of a broom handle. When I speced it, everything was from top end manufacturers.

    I have reasons for wanting very high current 12v so thats why the system is built as it is.

    I try to never let the voltage fall below 12.3. An old engineer once told me batteries never die, they are always murdered, so I keep them where they are happiest.


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    #25
    unkel
    Registered Users Posts: 64,771 ✭✭✭✭unkel


    12.3V that's about 60% state of charge? According to the spec sheet that's good for 5000 cycles (with one cycle per year that's 14 years) and it will probably still have something like 70-80% capacity
    SlowBlowin wrote: »
    An old engineer once told me batteries never die, they are always murdered, so I keep them where they are happiest.

    Yeah I heard that too. With a lithium battery if you keep it between 25% and 75% SOC under ideal circumstances (constant temp of 20C), it will still work in 100 years time


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    #26
    SlowBlowin
    Registered Users Posts: 1,884 ✭✭✭SlowBlowin


    unkel wrote: »
    12.3V that's about 60% state of charge?

    It would be, but that is under load, so its more like 80%. The system is always on, and state of charge voltage tables are no load. Most of the time the battery is between 85-100%.


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