Tom tell us what you know about lead acid chemistry. It would appear as if you have more extensive knowledge than is initially apparent.
I’m a physicist and my knowledge of lead-acid batteries is limited to what you learn from working with the batteries in your own car, camper van, and houseboat. What exactly would you like to know?
Physics is a very interesting topic. What type of physics is your particular branch?
Tom, I’m not snarky because I know everything and think I’m always right, I’m snarky because I don’t have a high education like you do and lack the elegance in argument like you can articulate. Everything I’ve learned has cost me dearly. The experience I gathered is all I have. I protect it probably over fiercely, this would imply an element of the dunning Kruger effect.
It also implies insecurity in my knowledge. I don’t know if I’m right, noone does until a theory is proven or they are defined as an expert. Essentially we are all expressing different elements of knowledge and assumptions.
I’m 70 years old now and retired. During my studies, I focused on low-temperature physics (superconductivity, etc.). Back then, almost all the jobs for physicists were in the nuclear industry and the chip industry, and I didn’t want either of those. So, after completing my physics degree, I also studied architecture and then worked at the university for a while. I earned my living with software development, and later I also trained building energy consultants.
I have Asperger’s and am therefore practically addicted to knowledge; I’m interested in almost everything, and I want to know everything and understand how everything is connected. If it had been offered at a university in my region, I would have also studied cultural anthropology, and perhaps philosophy and politics as well.
But my knowledge isn’t just theoretical; it’s primarily shaped by my experiences. I lived on a sailboat in Sicily for many years, later on a houseboat on the canals of France, and then traveled throughout Europe in a motorhome. I installed the energy systems myself in all the boats and motorhomes, and in doing so, I acquired considerable knowledge about photovoltaics and batteries.
And before you ask: I still don’t know what I’ll do when I grow up 
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Ditto, I also suffer from Asperger’s and have been addicted to electronics from the age of dot, kicked off back in the early sixties by the Ladybird ‘Magnets, bulbs and batteries’ series of books. I’ve spent most of my working life self employed, designing and building control equipment for automating piling rigs on building sites, which had to be battery powered and extremely resilient, but I’ve never had to deal with the practicalities of battery management until I installed the solar PV system and suffered the problems I’ve described above. My ‘smart’ home is full of home built sensors and controllers all powered by the solar PV system. It’s not often I’ve come across anyone with a similar background, so always interesting to hear other peoples stories
PaulM
It’s nice to meet someone who is cut from the same cloth as me. Interestingly, I don’t “suffer” from having Asperger’s; in fact, I’m quite happy with it. It’s more everyone else who suffers because of it.
We simply have to accept who we are, and even if everyone else thinks we’re aliens, we can still lead a happy and fulfilling life.
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Please do not spread fake information. There is no LFP lithium battery that can last less than 1000 cycles, and that’s down to 80% of original capacity. No matter how bad you manage them, the built-in BMS will keep the cells under specs. Even the worst LFP batteries will easily give over 1000 cycles, unless the BMS gets damaged due to system misconfiguration.
This is rather broad and misleading.
Commercial batteries will typically state in their specs as part of warranties etc and it will vary, some are far above 6000 cycles.
No LiFe battery will only get 10 cycles, you are conflating different chemistries which will be confusing.
Building DIY batteries is also not for everyone. If you don’t know what you’re doing you can have real problems, as we see from the many issues that get logged here. It is a project not suited to everyone, that the internet has managed to convince people is incredibly easy.
Yes, exactly right, ‘suffer’ was the wrong word to use. After 70 years you become used to dealing with the ‘non-aliens’ who don’t have the same advantages as us
PaulM
Yes, it’s incredibly easy, much easier than, for example, assembling an IKEA shelf yourself. I did it myself. And yes: as with most other DIY projects, you need to know what you’re doing, and above all, you need to be aware of the dangers.
Edit: Sorry, I wasn’t finished with the comment and my phone posted it prematurely.
Just for clarification, when I say “Lithium,” I am speaking specifically about LiFePO4 (LFP) technology, rather than NMC/18650 types.
@nickdb
To clarify on the 6,000-cycle point—I’m not pulling that from thin air; it’s the standard specification for modern “Grade A” cells used in many DIY and commercial builds. For example, the EVE LF280K datasheet (Version B) explicitly guarantees ≥6,000 cycles at 0.5C/0.5C (25°C) to 80% capacity. Similarly, Winston (LYP) cells often cite 6,000 to 8,000 cycles depending on the DoD. While these are “standard test conditions,” they provide the benchmark for what the chemistry is capable of in a stationary storage environment like Paul’s.
@thanar
Regarding the “10 cycles” comment: I have personally seen batteries (specifically Super-B units) show “failed” or “degraded” status in their logs with fewer than ten cycles. This is usually a result of the BMS firmware flagging the pack due to severe mismanagement or environmental factors rather than the chemistry itself wearing out. In my experience, for a user, a “degraded” flag from the BMS often results in the same outcome: a system that isn’t working. these batteries are perfectly fine to use, many never did anything that would actually degrade them and the degradation comes by the firmware trying to overwrite nvm during update but the systic is overwriting that vector with old data meaning the system detects it as degraded, when in fact they were not ever abused. This is further correlated by the fact that the system flags them as degraded even thought they clearly show a low cycle count, (on average under 100).
My goal was simply to show Paul that if he moves to LFP and manages it well (which he seems more than capable of doing), he’ll get 10x the life of his current AGMs.
I appreciate the correction if it seemed I was misrepresenting the chemistry—I’m focused on the system-level reality users face.
That would be amazing, 10x the life I’ve had with the AGMs would be 35 years, by which time I’ll be 105, hopefully sat in my rocking chair on the patio watching the world go by and not worrying about solar PV or batteries
The central statement of the presumption is: If 6000 is the projected cycle count, even if it were half, 3000, that’s still very much better than the cycle count you are experiencing here with lead acid
EDIT:
here are the data sheets:
Thanks, I’ve added the data sheets to all the other info. I’ve accumulated, this whole thread has been very educational. I shall spend some time now looking at everything that has been suggested so hopefully in four years time, when the batteries need replacing again, I’ll be in a much better position to upgrade to something more permanent.
Any experience with the Victron Battery Balancer, Battery Balancer | Victron Energy ?
PaulM
I would love to have tested it, I would love tear that baby apart and decompile its firmware and find all its secrets.
Fact of the matter is I have yet to do that, and I can only speak from my experience and what I know:
Based on that, I have had questions about it functionality, unfortunately they will remain questions until I get get my hands on one and am able to formulate my questions so they don’t sound like brain farts. The impression I have is pretty stellar tbh. A bit pricey and based on my lack of knowledge not as versatile as I would have hoped for the price, but other then that they appear to be designed with the single purpose of working in the unique realm of victron kit. I bet that exactly that use case might be precisely where it shines like a *riggin’ diamond.
Can you switch out the chemistry? Partially, within the confines of the manufacturer, and that is already way more than some other companies offer. You’d have amazing support here from very knowledgeable people, you wouldn’t have to write any weird drivers or software because its all just right there.
Can it justify the price of kit? Well obviously if I’m going to tear it apart, no. If I’m going to try and hack it together to work with other chemistry, maybe… that is for me the ultimate use case, total control, open hardware, interoperability, interchangeability of chemistry, repair-ability and availability of schematics…that is my definition of a universal bms. I simply dont know enough about it to say anything valuable to you right now.
I like to get into the nitty gritty and cut my teeth on the rocks if you know what I mean.
Difficulty is a challenge to be accepted and cherished as its reward is the highest, that is knowledge.
Its not easy, its rewarding.
My gut feel also is it’s a bit pricey for what appears to do, but there again so is the rest of the Victron kit, you pay for their research and expertise as well as the cost of building the kit, not to mention the convenience of buying something off the shelf that you know will work reliably.
The operation appears quite simple so along with investigating the diyBMS etc. I may have a play with a diy version once I have new batteries installed in the PV system. Theoretically it shouldn’t even need any ‘intelligence’, but what equipment these days doesn’t have a couple of microprocessors built in for driving a few LEDs ? There again, if the diyBMS/Lithium batteries comes to fruition I won’t need it !!!
PaulM
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Safe travels and happy hunting
It’s important to understand that LFP cells don’t age as much over time, but rather due to temperature stress. This stress can be managed, for example, through battery design with good temperature management, or by the user themselves by avoiding high charging and discharging currents.
For my EVE 280K cells, the manufacturer specifies a cycle life of 8,000, but at a maximum charge or discharge current of 0.5C. Manufacturers of batteries using the exact same cells often specify a cycle life of only 4,000, but at a maximum charge and discharge current of 1C. This clearly illustrates the impact of high currents on heat generation.
Because a smaller battery wouldn’t have been cheaper, I opted for a larger battery than necessary, namely 15 kWh instead of just 8 to 10 kWh. This will hopefully lead to an even higher number of charge cycles, as my charging and discharging currents are now only a maximum of 0.3C, and my battery will still be perfectly usable for many years even after its “official” end of life when its capacity drops to 80%. It will only become critical for me when my battery’s remaining capacity drops to 50%. Even if the larger battery is more expensive, the extra cost is offset by the significantly higher number of charge cycles and longer lifespan.
And another advantage of a battery that’s actually too large: You can then use a smaller inverter than the installed PV capacity and still feed all surplus power into the grid. I only have an MP2-3000, which delivers a maximum output of 2.4 kW, but I have 5.4 kWp of solar power. The surplus power is stored in the large battery and fed into the grid at a constant rate, for example, overnight. This significantly reduces my costs.
Tom, thanks for that info, it makes a lot of sense and will definitely help with my decisions around future battery replacements.
Gassing off of lead acid batteries is way more hazardous than lithium. Pb batteries need good ventilation, in a basement this is not normally the case.