Idiot's guide to a self build battery

[Joeboy]

Wow thanks joe

Plenty of ways you have posted to get in touch with Colin .

In the mean time, kick started by buying a BMS on the 11.11 Ali sale -
It’s from their official store, and I see many battery videos using the same BMS so should be a good

Figured it was about the price of a balancing board and get the benefit of Bluetooth. Can’t say no to Bluetooth

Funnily enough, it was cheaper getting it shipped to the UK than getting it delivered to HK, for a relative who is coming back in the new year to carry over. Hah

No worries, spoke to him last night.

[Caesium]

Also the balance function is a max of 30mA. This is OK once the cells have been initially top balanced and will keep them in "sync". But if they are not initially close in terms of cell voltage it will take a very long time to balance the pack.

This is the main reason I didn't end up with a Daly - I did look at them - but instead went for JK BMS that has 0.6A balancing current (they do bigger models with higher current but this should be plenty). Unsure whether I'll keep the separate active balancer attached as well; it can't hurt (and can shift over 5A, but thats at very extreme voltage deltas); but may be unnecessary.

Off Grid Garage (youtuber) recommends the JK units very highly as well and he seems to know what he's talking about.

They have bluetooth and also a UART socket which I've already hooked up to a USB-serial board so I can read cell voltages off every few seconds, seems to work well. Planning to use the first one on my second DIY stack once it arrives, so I'll do pictures then

[Kenny000666]

Oh man, in my impulse buy moment, I brought the 60a version of the daly, and yes your right, had to trawl through the net to find a data sheet and max charge is 30a … . Damn it I was thinking 60a was sufficient as my inverter is set to max charge and discharge on 50a for my pylon US5000.

Let’s see if it’s not too late to get that upped to the 100a version.


On the battery front. Got some quotes back from both suppliers
280k for 108 a piece from Caesiums recommended supplier and 302s for 109 a piece from Joes supplier. Looking at the battery comparison Caesium posted before, the “k” versions have double the cycles of the none “k”, although capacity wise seems for a dollar more can squeeze an extra 1 kWh into it. I’m asking for a spec sheet for the 302s, but I think my research suggests they are newer and so have the similar 6500 cycles as the “280k” versions.

Not sure if I missed it in your threads, but was there a reason you went straight for the 280s rather than the slightly higher models at such a small price diff?

Currently I’m leaning towards the 302s as slightly cheaper in total (cheaper delivery) coming in at $2019 vs the 280k coming in at a total of $2088. Got the be a no brainer if it’s cheaper and maintains the same cycles as 280s and higher capacity

[nowty]

Not overly impressed with this review of a Daly BMS.

ONLY balances when charging ????

And I've seen a few of this guys reviews so he knows what he's on about.

[Caesium]

Are you sure both quotes are EVE? I'm pretty sure EVE don't do a 302Ah - they do 280Ah and 304Ah

https://www.evlithium.com/hot-lithium-b ... ttery.html
https://www.evlithium.com/LiFePO4-Batte ... -cell.html

I suspect your 302Ah quote is for another manufacturer, CATL?
https://www.evlithium.com/CATL-Battery- ... 302ah.html

So its probably comparing granny smiths and golden delicious. (specifically didn't say apples and oranges as they are both batteries

You may find the 304Ah EVE are a bit more than $1 extra over the 280Ah.

Thats not to say the CATL are rubbish though, I've no idea - I didn't really look into those too deeply. But generally I think I saw EVE used more in the DIY crowd? It seemed the safer bet and what a lot more people were going for, so I stuck with it.

[Caesium]

And I've seen a few of this guys reviews so he knows what he's on about.

Yep this is the same guy that convinced me to go JK

[Oldgreybeard]

Not that unusual for a non-active balancing BMS to only balance when charging. For years the majority of BMS designs only balanced at the end of a charge, and from watching the behaviour of our car it looks very much as if this is what its BMS does. Our car is just finishing a charge now, and the charge current has been tapering down for the past fifteen minutes or so as it does the cell balancing part of the charge. I did plug in a gadget to the OBD port not long after we got it to see the cell voltages, and that showed the balancing going on for the last part of the charge.

[Kenny000666]

Thank Caesium, yeh sorry, it was a catl and the eves are coming in about $100 higher @ $115 a piece.

Don’t want to start a EVE vs CATL debate but the way I see it, they are both main stream manufacturers and reputable, similar specs, so yeh why not go for the CATLs for $100 cheaper

If I recall a thread correctly, nowty shared a link for CATL’s he brought.

[Joeboy]

Oh man, in my impulse buy moment, I brought the 60a version of the daly, and yes your right, had to trawl through the net to find a data sheet and max charge is 30a … . Damn it I was thinking 60a was sufficient as my inverter is set to max charge and discharge on 50a for my pylon US5000.

Let’s see if it’s not too late to get that upped to the 100a version.


On the battery front. Got some quotes back from both suppliers
280k for 108 a piece from Caesiums recommended supplier and 302s for 109 a piece from Joes supplier. Looking at the battery comparison Caesium posted before, the “k” versions have double the cycles of the none “k”, although capacity wise seems for a dollar more can squeeze an extra 1 kWh into it. I’m asking for a spec sheet for the 302s, but I think my research suggests they are newer and so have the similar 6500 cycles as the “280k” versions.

Not sure if I missed it in your threads, but was there a reason you went straight for the 280s rather than the slightly higher models at such a small price diff?

Currently I’m leaning towards the 302s as slightly cheaper in total (cheaper delivery) coming in at $2019 vs the 280k coming in at a total of $2088. Got the be a no brainer if it’s cheaper and maintains the same cycles as 280s and higher capacity

Physical size of the units for a fixed space and the 6,000 cycle were my happy parameters as was a confirmation of grade A status.

[Joeboy]

Been chatting with another member through PM who is buying into the self build battery storage . Firstly, well done to him for taking care of business!

Making a cuppa there as I sweat out the last of this cold and I thought to myself 'I wonder how much storage capacity we have across the membership'?

Energy storage seems to be a hard one to get in place at grid scale in significant volumes for chemical batteries. Certainly in Winter it's a critical component in the home level RE game? Then there's my personal favourite which is the low cost thermal mass batteries, concrete slabs, storage heaters etc, then super insulated hot water tanks, thermal stores, sand/wax other phase change materials. Just a thought...

I am 101kWh chemical battery storage and 80kWh thermal mass storage incl HWT.

I will not include my Varta AA & AAA rechargeable batteries nor my power banks.