Idiot's guide to a self build battery

[Stinsy]

Brand new batteries from the same batch will (should) stay very close indeed when new. However over the years as they age their capacities will diverge slightly and they’ll start to move out of balance. This can expedite ageing because a low cell in the string will be excessively-discharged and a high cell excessively charged. This situation will become worse over time. In extremis it can be dangerous.

Running parallel links between all cells and their sisters in other strings will help because the weakest cell in the pack will be propped up by stronger cells. However an active balancer is a really good idea considering the cost compared with the cost of cells.

Don’t expect it to do much now. But in 10 years it’ll be silently keeping everything good!

[AlBargey]

Uh oh. Well done @Joeboy, I've read this thread a few times over the months, and I think It might be catching and time to sell on my 1.3t of lead...

I'm thinking 8S3P 304Ah (24v) But it means I've been jamming my brain researching and reading info on the net and the Will Prowse solar forum too, and as a heads up I hadn't noticed much/any talk of how it seems most 'Grade A' cells are actually not the Automotive / EV grade, but 'B' grade - maybe not an issue for us as ESS but I'd still rather know.

Many Alibaba suppliers have been grinding off the laser etched 'B' that EVE prints on their QR code for cells not up to spec for EV's but should be OK for ESS, and then they print a new fake QR over the top, tell tale signs are sanding marks around the QR code when peeling back the black top cover around it. - A google will find many threads and examples of this!

Has anyone here done capacity / IR testing of their cells or checked the QR codes for authenticity?

I asked because the QR code on the cells below looks a bit suspect?

Can use an app like: https://play.google.com/store/apps/deta ... =web_share

or just put details in here to check: https://www.gobelpower.com/lifepo4_decoder.html

I have no affiliation, but saw lots of talk and the links on the other forum, and don't mean to scare anyone, hopefully they are all fine and dandy.

May all our cells live a long and happy life

Is this QR code legit?

I had some bad luck and it seems my second batch of batteries was damaged while being shipped.

[Colin Deng]

Uh oh. Well done @Joeboy, I've read this thread a few times over the months, and I think It might be catching and time to sell on my 1.3t of lead...

I'm thinking 8S3P 304Ah (24v) But it means I've been jamming my brain researching and reading info on the net and the Will Prowse solar forum too, and as a heads up I hadn't noticed much/any talk of how it seems most 'Grade A' cells are actually not the Automotive / EV grade, but 'B' grade - maybe not an issue for us as ESS but I'd still rather know.

Many Alibaba suppliers have been grinding off the laser etched 'B' that EVE prints on their QR code for cells not up to spec for EV's but should be OK for ESS, and then they print a new fake QR over the top, tell tale signs are sanding marks around the QR code when peeling back the black top cover around it. - A google will find many threads and examples of this!

Has anyone here done capacity / IR testing of their cells or checked the QR codes for authenticity?

I asked because the QR code on the cells below looks a bit suspect?

Can use an app like: https://play.google.com/store/apps/deta ... =web_share

or just put details in here to check: https://www.gobelpower.com/lifepo4_decoder.html

I have no affiliation, but saw lots of talk and the links on the other forum, and don't mean to scare anyone, hopefully they are all fine and dandy.

May all our cells live a long and happy life

Is this QR code legit?

I had some bad luck and it seems my second batch of batteries was damaged while being shipped.

The A grade cells has the test report from EVE
With the EVE logo stamp on it
Hope this will help

[Joeboy]

Uh oh. Well done @Joeboy, I've read this thread a few times over the months, and I think It might be catching and time to sell on my 1.3t of lead...

I'm thinking 8S3P 304Ah (24v) But it means I've been jamming my brain researching and reading info on the net and the Will Prowse solar forum too, and as a heads up I hadn't noticed much/any talk of how it seems most 'Grade A' cells are actually not the Automotive / EV grade, but 'B' grade - maybe not an issue for us as ESS but I'd still rather know.

Many Alibaba suppliers have been grinding off the laser etched 'B' that EVE prints on their QR code for cells not up to spec for EV's but should be OK for ESS, and then they print a new fake QR over the top, tell tale signs are sanding marks around the QR code when peeling back the black top cover around it. - A google will find many threads and examples of this!

Has anyone here done capacity / IR testing of their cells or checked the QR codes for authenticity?

I asked because the QR code on the cells below looks a bit suspect?

Can use an app like: https://play.google.com/store/apps/deta ... =web_share

or just put details in here to check: https://www.gobelpower.com/lifepo4_decoder.html

I have no affiliation, but saw lots of talk and the links on the other forum, and don't mean to scare anyone, hopefully they are all fine and dandy.

May all our cells live a long and happy life

Is this QR code legit?

I had some bad luck and it seems my second batch of batteries was damaged while being shipped.

The A grade cells has the test report from EVE
With the EVE logo stamp on it
Hope this will help

Hey Al, get them weighed in! I ran through the full gamut of emotions pre & post install. Straight up, trust Colin, pm him what you are looking to do or on the thread. He steered me correctly to the 6,000 cycle batteries.

My first couple of/few ðays post install I was checking power flows and capacity. My capacity test was not scientific. Basically if I run X amount of house load for X amount of time and stay under the 3.8 inverter grid threshold I should have X% left. It was absolutely fine. You'll do well with Colin. For clarity, no affiliation here other than wishing to see a good professional guy get the business.

[AlBargey]

The A grade cells has the test report from EVE
With the EVE logo stamp on it
Hope this will help

Yes, this is a good tip! Real A grade will have the original test report from EVE available to see.

[AlBargey]

Hey Al, get them weighed in! I ran through the full gamut of emotions pre & post install. Straight up, trust Colin, pm him what you are looking to do or on the thread. He steered me correctly to the 6,000 cycle batteries.

My first couple of/few ðays post install I was checking power flows and capacity. My capacity test was not scientific. Basically if I run X amount of house load for X amount of time and stay under the 3.8 inverter grid threshold I should have X% left. It was absolutely fine. You'll do well with Colin. For clarity, no affiliation here other than wishing to see a good professional guy get the business.

Love the practical capacity test

There's still plenty of life left in the 2v Hoppekke's, think I'll put them up for sale with stainless battery box after the switchover, would be a shame to send them for scrap!

I'm just thinking I should be able to gain up to 20% efficiency from Lifepo4 vs Pb, currently we're getting around 77% round trip efficiency only (Worse when it's cold) That's a fair bit of diesel in the winter

Will give Colin a shout

[Joeboy]

Hey Al, get them weighed in! I ran through the full gamut of emotions pre & post install. Straight up, trust Colin, pm him what you are looking to do or on the thread. He steered me correctly to the 6,000 cycle batteries.

My first couple of/few ðays post install I was checking power flows and capacity. My capacity test was not scientific. Basically if I run X amount of house load for X amount of time and stay under the 3.8 inverter grid threshold I should have X% left. It was absolutely fine. You'll do well with Colin. For clarity, no affiliation here other than wishing to see a good professional guy get the business.

Love the practical capacity test

There's still plenty of life left in the 2v Hoppekke's, think I'll put them up for sale with stainless battery box after the switchover, would be a shame to send them for scrap!

I'm just thinking I should be able to gain up to 20% efficiency from Lifepo4 vs Pb, currently we're getting around 77% round trip efficiency only (Worse when it's cold) That's a fair bit of diesel in the winter

Will give Colin a shout

It's good they'll get a second life rather than just recycled. Looking forward to seeing a marine build!

[Stinsy]

Hey Al, get them weighed in! I ran through the full gamut of emotions pre & post install. Straight up, trust Colin, pm him what you are looking to do or on the thread. He steered me correctly to the 6,000 cycle batteries.

My first couple of/few ðays post install I was checking power flows and capacity. My capacity test was not scientific. Basically if I run X amount of house load for X amount of time and stay under the 3.8 inverter grid threshold I should have X% left. It was absolutely fine. You'll do well with Colin. For clarity, no affiliation here other than wishing to see a good professional guy get the business.

Love the practical capacity test

There's still plenty of life left in the 2v Hoppekke's, think I'll put them up for sale with stainless battery box after the switchover, would be a shame to send them for scrap!

I'm just thinking I should be able to gain up to 20% efficiency from Lifepo4 vs Pb, currently we're getting around 77% round trip efficiency only (Worse when it's cold) That's a fair bit of diesel in the winter

Will give Colin a shout

There are loads of benefits of Lithium over Lead! The whole charging/discharging process is much simpler, no “absorption, bulk, float”. Absolutely zero maintenance. Ultra-long lifespan. Effectively zero self-discharge rate. Fantastic efficiency. Way better energy density. No problem keeping them in middle charge-state most of the time. Etc.

The only learning curve is “balancing”. With lead you just overcharge the pack and the lowest cell charges while the higher cells give off the energy as heat. If you try this with lithium you end up on the news. So you need a device to balance the pack. For £50 you can get an “active balancer” this takes energy from the highest cell and shifts it to the lowest. Alternatively you can get a cheaper “passive balancer” this bleeds power off of any cell that is high and puts it through a resistor, it only works at high SoC. Either way it is a fit and-forget type situation (you might want to check cell voltages annually). Interestingly I know of no BEV with active balancing…

You should look forward to having an ever-so-slightly simpler life!

[AlBargey]

Yep I'm definitely excited to swap out the lead, I especially won't miss needing an 8 hour+ charge cycle with tapering absorption current dragging on for hours! LFP will also help shorten genny run time in winter.

I'm going to go for 3 x JK BMS with 2a Active balancer built in, which I can get to work with the Victron, but it seems there still aren't any perfect and affordable BMS's available yet. At least JK's are relatively cheap and pretty good, hopefully they last..

[Joeboy]

Yep I'm definitely excited to swap out the lead, I especially won't miss needing an 8 hour+ charge cycle with tapering absorption current dragging on for hours! LFP will also help shorten genny run time in winter.

I'm going to go for 3 x JK BMS with 2a Active balancer built in, which I can get to work with the Victron, but it seems there still aren't any perfect and affordable BMS's available yet. At least JK's are relatively cheap and pretty good, hopefully they last..

Al, looking at a 24kWh energy storage solution in LFP, is this a step up in storage volume and will it be significantly more compact? I know space matters on a vessel of any type. Certainly with my add on battery pack it is significantly smaller than the pylontechs beside it.




I am mildly obsessed with storage and like the idea of more space for tins of food.