Not all of them run backwards. A lot run forwards in both directions, to solve the problem of "people putting the meter in upside down a week a month to reduce their bill."

How on earth do you "put a meter in upside down"? They don't just slot in, they're wired in. If you're going to unwire your meter, you'd just take it out altogether. Or is the idea you connect the wires backwards and the meter reader doesn't notice? I think he'd spot the disk going the wrong way.

The smart meters also typically have separate registers to count "net energy through" and "total energy through," and if they split and you're not listed as a solar install, your power company may come sniffing around.

To determine what? Illegally making your own power from solar panels you paid for?

Yeah, but that's not a long lived battery, is it? What's the datasheet say?

Lithium and Lead both last about 2200 cycles. Lithium is for where you need lightweight or smaller size, like a car or a cordless drill. It's way too expensive (times seven!!) to use Lithium on a stationary system.

Only 200 cycles at 80% DoD? Weak...

No. The deep cycle ones are 220 cycles at 100% DoD. 2200 cycles at 80% DoD.

This is the Trojan battery I have in one of my solar trailers.

https://assets.ctfassets.net/nh2mdhlonj7m/5i2peNrNeLJO58mHprrXc7/86ef16e5e252fcc5f9ec782ba9396d82/SPRE_06_415_DS.pdf

Per the datasheet, it's rated at 1200 cycles to 80% DoD (down to 20% state of charge), and 2000 cycles at 50% DoD.

Sounds rubbish to me, so to make it last a long time, you can only use half of it, so you're buying twice as much battery as you need.

I just wish that battery manufacturers would be a bit clearer in their advertising blub when it comes to number of cycles "expected" - cell temperature (not ambient temperature), charge rate, discharge rate, charge cut-off voltage, discharge cut-off voltage, rest time between charge and discharge, rest time between discharge and charge (and many more factors) play a big role.

If you don't buy batteries from "Cheap manufacturer of the week," you get those datasheets in various forms.

If you buy Lead Acid, they're 7 times cheaper, so you don't care if one sux, you just avoid that make in the future.

My standing policy is that I won't buy a battery for deep cycle use without a datasheet.

I've never had a problem using the cheapest ones I can find. These ones are called "Snappy High Performance". I've abused them to hell and back and they still work fine.

A question pertinent to off-grid power (or semi-off-grid).
As we all know, batteries degrade with time and use, so, how many of us actually check that the "100AHr" battery actually has a capacity of "100AHr" when we take delivery of a nice shiny new one?
Also, how many of us keep track of the capacity over time (clock or cycles)?
I know this takes a bit of time and effort, but it can be quite enlightening to see what capacity we have actually spent money on, and how much of it has "vanished" with use.

Some years ago I was involved in installing instrumentation and logging on some equipment which included a number of 150Ah, 12V batteries, arranged into two 900Ahr, 48v bank. These banks were running as a sort of UPS, and regularly were to be hit with very high discharge rates, and then charged up to "full" capacity under a quite well controlled charge regime. OK, one might expect both banks to be supplied from a single source, but "the folks in the office" decided to buy from two sources. We inspected the batteries on arrival, for weight, dimensions. A bit of a shock as the two sets had somewhat different dimensions and weights, set A was dimensionally and weights were within less than 1%; set B on the other hand was somewhat random, and the weights were between 10 and 30% less than those of set A. Scratch heads, what's the difference? We now did capacity tests on all the batteries (a couple of days work as all needed to be fully charged before we started). Set A came in between 145 and 150 Ahr; the highest of set B came in at about 135Ahr, and lowest was just 105Ahr, even more interesting was that the lightest of set B was one of the highest capacities in the set. We (engineers) shouted at the office, asking in no uncertain terms why they'd bought from two sources, and what was the price saving - still waiting for an official answer to the second question.
We had to engineer a custom frame for set B, taking into account the different sizes of batteries (hours of welding) and try to get a balanced battery bank.
Now we come to service. About 12 months in we had a call to say that there was a problem with bank B, it wasn't holding up for the required run time, bank A was still running as intended. We arrange to go to site and run some tests. Opening the door to the battery room said there was a problem as there was a somewhat acidic smell, check what phase of operation the two banks were in - both had just finished charge phase and we had 72 hours before one bank would be needed. That was great news. First check the bank voltage Bank A was at just over 50V (about right for a resting 48v bank), bank B was down to below 46v (suggests a cell is down, or the bank is generally "weak". Strip bank B into its 12v sub assemblies and check the voltages - all were below 12V (many rude words). Start stripping the bank B blocks and check each battery in turn, a couple were down to 8V, but most were just below 12V. Time to do capacity tests, no battery was anywhere near their "as received" capacity, most were down to about 75%, and some were all but dead. Remember these batteries were only a year old, and had done about 100 cycles (twice a week, 52 weeks a year) down to what should have been about 30% capacity. The two banks were used alternately, and the loggers showed that this had been very rigorously followed, but bank A had actually done a few part cycles to cover for the failure of bank B.
One thing we did learn was that there was a "big saving" in the capital cost of bank B, but that was now being wiped out by having to purchase a new bank, new metal work, new cables and the time spend investigating the problem.
We are now six years down the line, and bank A is due to be replace with a LiFePO4 set - 'twill be interesting to see how that holds up. Rumour has it that if the LiFePO4 battery does what it says on the tin bank B will be retired in another year (remember this is a replacement for the ***py set).

I always run a quick check on a battery. Fully charge it, discharge it over say 2 hours (or whatever you intend to use it for) and see if you get what you expect. Why on earth didn't you send bank B straight back to the supplier when you first checked them? If I buy a brand new car and it doesn't run properly, I don't just put up with it. If it's supposed to go 120mph and I can't get over 90, it goes back, immediately!

As for the smell, didn't you have battery equalisers and fuses on each battery and so forth? Shouldn't be possible for one to overcharge and give off a smell, you're lucky they didn't explode.

Why are you buying Lithium at 7 times the price? I very much doubt it's anything like 7 times better.

You are not doing a proper battery test, indeed you are fooling yourself into thinking you are.
Do a controlled charge on the battery, checking its voltage over at least one hour, preferably more (until it is stable). Now discharge at a fixed rate (preferred rate is 0.1C - 10A for a 100Ahr battery), monitoring the voltage, and cell temperature, until the battery voltage has dropped to 12.00v, which equates to 25% of charge. Now do the sums. Now recharge the battery and repeat but discharge at a higher rate (say 0.5C) - yes another cycle. It's a pain to do, but the second cycle often shows up batteries that are failing but haven't actually failed.

The system has equalizers, but they don't work if there are dead cells in a battery, fuses don't really work when the batteries are not shorted (which they weren't - we stripped one of dead batteries and it had cracked, but retained plates). Additionally batteries can out-gas during discharge, and according to those with better noses than mine the smell is different. I agree, the customer was lucky that the abysmal set of batteries didn't explode, obviously there was just enough ventilation to keep the level of hydrogen below danger, but high enough for a well tuned nose to detect.

As for buying LiFePO4 batteries being 7 times the price of lead-acid, they are no longer 7 times the price but more like five times and have an expected life of about 5 times as many cycles as the lead-acid ones have had. Besides that, this is a job for a customer, and they want them, who also wants to more than double the capacity but don't have space on site for either a second battery room or doubling the size of the existing room. Oh joy, this change means a pile of work on the charge and monitoring systems.....

You are not doing a proper battery test, indeed you are fooling yourself into thinking you are.
Do a controlled charge on the battery, checking its voltage over at least one hour, preferably more (until it is stable).

Yes I did that, I left it on until it stopped taking much current.

Now discharge at a fixed rate (preferred rate is 0.1C - 10A for a 100Ahr battery), monitoring the voltage, and cell temperature, until the battery voltage has dropped to 12.00v, which equates to 25% of charge. Now do the sums. Now recharge the battery and repeat but discharge at a higher rate (say 0.5C) - yes another cycle. It's a pain to do, but the second cycle often shows up batteries that are failing but haven't actually failed.

I've only ever done the 0.5C. If it can do that it should be fine?

The system has equalizers, but they don't work if there are dead cells in a battery,

I'm guessing they'd try to and start wasting power.

fuses don't really work when the batteries are not shorted (which they weren't - we stripped one of dead batteries and it had cracked, but retained plates).

But if you have a 6 cell battery connected to a 5 cell battery (which is what they are when one collapses), you get colossal current flow. It would stop what my unfused one did, the 12V ones blew up the 10V one.

Additionally batteries can out-gas during discharge, and according to those with better noses than mine the smell is different. I agree, the customer was lucky that the abysmal set of batteries didn't explode, obviously there was just enough ventilation to keep the level of hydrogen below danger, but high enough for a well tuned nose to detect.

I take that warning with a pinch of salt, they say not to charge them in an enclosed space, as though good ones give off hydrogen. If they did that on every charge, they wouldn't have much left inside them soon!

As for buying LiFePO4 batteries being 7 times the price of lead-acid, they are no longer 7 times the price but more like five times

Depends on the country. In the UK, 7 times, in Australia, 2 times. Lead and Lithium are mined and the batteries manufactured in certain countries, and (especially Lead) batteries expensive to ship. So it matters where you live. An Aussie told me the Lead he could buy were made in the UK, but the Lead for them was mined in Australia! Worst possible case!

and have an expected life of about 5 times as many cycles as the lead-acid ones have had.

No, both are 2000-odd.

Besides that, this is a job for a customer, and they want them, who also wants to more than double the capacity but don't have space on site for either a second battery room or doubling the size of the existing room. Oh joy, this change means a pile of work on the charge and monitoring systems.....

And more money for you?

I've only ever done the 0.5C. If it can do that it should be fine?

Guessing here but even if the o.5C test on its own shows fine, a significant difference between the two would be suspicious?

What do you do about earth/ground?

I have a ground rod driven, bonded to neutral at the inverter.

Very stupid really, since you can touch a bare live wire and the actual ground and get a shock. If it was floating, like on a building site with isolating transformers, you couldn't. No current would flow.

How much do those isolating transformers cost? And once wiring is installed, you shouldn't be seeing bare wire at all. It should all be enclosed in a few layers of various protection from "fingers and bare wire." If you're the sort to work on live electrical systems, well, I think "turning off power" is a lot cheaper than 200A capable isolating transformers.

And multiple computers talking to each other, best if both chassis are the same voltage exactly, so no current flows through the ground wire of a USB cable for example.

Yeah, or don't hook computers together with things that aren't isolated. Ethernet has magnetic isolation as part of the spec, so different ground voltages isn't a problem with it.

Or I could use a 12V system, but then all the low voltage wires would be thicker and more expensive.

And you've just reasoned out why almost nobody does high power DC systems. You end up with wires the size of your forearm to handle the current for any serious power.

Going 48VDC -> 240VAC -> 12VDC at the destination is almost certain to be lower losses for any real length of run than trying to do it at 12VDC with sane wire sizes. Also, "percent loss" is lower for a given voltage drop at higher voltages. I can lose 5V on a 240V run and only lose a tiny fraction of the total power delivered. Do that at 12V, you've lost nearly half the power and nothing will run. So not only do you need fatter wire to handle the currents, you need even fatter wire to keep the voltage drop acceptable. The few volts of drop acceptable at mains voltage isn't workable at 12V.

How on earth do you "put a meter in upside down"? They don't just slot in, they're wired in.

In the US, they very much do "slot in." And you can put them in upside down, if you want - there's rarely anything actually prohibiting that.

If you're going to unwire your meter, you'd just take it out altogether. Or is the idea you connect the wires backwards and the meter reader doesn't notice?

I don't know. I've not looked extensively into the details of how to commit power bill fraud. I've been told this is the reason that a lot of the meters either "always run forward" or "detect when power is flowing the wrong way through them" by people who do that sort of thing, and I've not decided to write a PhD thesis on the history of power meters.

To determine what? Illegally making your own power from solar panels you paid for?

Yeah. Exactly that. To determine if you've hooked up some sort of generating system without having gone through the various inspections and paperwork to ensure it's legal and licensed for use on the power company's grid, that it shuts down properly with the grid going down (or isolates from the grid if you have a transfer switch), and various other things to ensure that you're not putting some piece of Chinese trash with 10% THD on the power grid.

Out here, they're mostly looking for UL listing of the inverters and they actually test the rapid shutdown and feed in delay times when you commission the system (sit there for 5 minutes with a current clamp on one of the lines to make sure it behaves as specified).

Again, I don't know the UK power systems or wherever you are - I just know US systems. If you're free to stick whatever you want on the power grid, fine, but that's not the case here, and at least in my power company's area, if they identify you as a solar generator and backfeeding without having gone through their process, they'll come and disconnect the system - and if there's no easy way for them to do that, they simply take their meter base and leave, and it's on you to fix the problem to their satisfaction.

Sounds rubbish to me, so to make it last a long time, you can only use half of it, so you're buying twice as much battery as you need.

I guarantee whatever lead acid batteries you're using have very similar curves, because that's how the chemistry works. If yours don't have datasheets, then you're just guessing, instead of being able to actually look up the performance curves.

If you buy Lead Acid, they're 7 times cheaper, so you don't care if one sux, you just avoid that make in the future.

Yeah, except that I make my living in my office powered by this stuff, so I'd rather not have them regularly fail on me.

We clearly approach power systems very differently, though. I'm willing to spend the money to have something reliable with demonstrated performance, for where I make my living. You seem to value "low cost over everything," which is fine, but I doubt it beats the power grid for uptime (my office does).

but I doubt it beats the power grid for uptime (my office does).

Here the power grid has gone down no more than twice in the past 10 years. There are parts of UK where it isn't as good as Cambridge but most of the country it is pretty good.

I have a ground rod driven, bonded to neutral at the inverter.

How much do those isolating transformers cost? And once wiring is installed, you shouldn't be seeing bare wire at all. It should all be enclosed in a few layers of various protection from "fingers and bare wire." If you're the sort to work on live electrical systems, well, I think "turning off power" is a lot cheaper than 200A capable isolating transformers.

People get shocks, eg a kettle lead gets damaged, then they can get a shock from it's live to the earthed washing machine their knee is touching. So they invented earth leakage breakers. Now if neutral and earth were different, no current would flow, no danger.

I'm not suggesting an isolating transformer. In my house, and I suppose most houses, a cable comes from the nearest substation transformer with only two cores. One is live, the other is earth/neutral. Now if that second core was just neutral, there would very rarely be any shocks.

You don't have to bond the invertor's neutral to ground. You gain nothing from doing so. And you allow current to pass from live to earth, all you've done is increase danger.

Yeah, or don't hook computers together with things that aren't isolated. Ethernet has magnetic isolation as part of the spec, so different ground voltages isn't a problem with it.

Not sure what you mean here, so I'll tell you what I have. A normal desktop computer with it's own PSU. The chassis is connected to mains ground. The chassis is also 0V DC for the PSU output. It's the refence ground for all DC stuff in the computer. It also acts as shielding. I also have some graphics cards powered by a different supply. That supply's chassis is also grounded and the 0V output connected to that in the same way. So the graphics cards and the computer both have their chassis clamped to the same mains earth. So when one sends a 5V signal in relation to that, there is no problem. If I don't ground the two chassis, then I can feel some AC with my finger getting onto the casings by induction. I'm assuming that could cause interference.

In the US, they very much do "slot in." And you can put them in upside down, if you want - there's rarely anything actually prohibiting that.

That makes no sense at all. Firstly, why aren't they designed to only go one way with some kind of physical change on the top or bottom? Secondly, the meter reader is going to see your meter being the wrong way up! Thirdly, why are they slottable in? It's not like a lightbulb you need to change often. In the UK, they're hard wired. Having them removable easily by the customer is asking for someone to take them out, take them indoors and fiddle with them in private, or connect some wires behind them.

Yeah. Exactly that. To determine if you've hooked up some sort of generating system without having gone through the various inspections and paperwork to ensure it's legal and licensed for use on the power company's grid, that it shuts down properly with the grid going down (or isolates from the grid if you have a transfer switch), and various other things to ensure that you're not putting some piece of Chinese trash with 10% THD on the power grid.

Out here, they're mostly looking for UL listing of the inverters and they actually test the rapid shutdown and feed in delay times when you commission the system (sit there for 5 minutes with a current clamp on one of the lines to make sure it behaves as specified).

Again, I don't know the UK power systems or wherever you are - I just know US systems. If you're free to stick whatever you want on the power grid, fine, but that's not the case here, and at least in my power company's area, if they identify you as a solar generator and backfeeding without having gone through their process, they'll come and disconnect the system - and if there's no easy way for them to do that, they simply take their meter base and leave, and it's on you to fix the problem to their satisfaction.

I can understand them not wanting high THD onto the grid, but what's all the fuss about not shutting off? No sane electrician is going to assume there's no power on the live cable he's playing with. And if my invertor can't power everyone's load, it'll overload and shut off anyway.

There's a thing called solar islanding. Let's say the power coming into my village dies. Lots of us have solar, we all feed into the grid. The solar is enough to power what everyone's using. Sounds like a good thing to me - we all still have power, including the ones without panels.

I guarantee whatever lead acid batteries you're using have very similar curves, because that's how the chemistry works. If yours don't have datasheets, then you're just guessing, instead of being able to actually look up the performance curves.

They're not 7 times worse than Lithium, so it's not worth paying 7 times as much for Lithium. I'd only use Lithium if I really needed it lightweight or small.

Yeah, except that I make my living in my office powered by this stuff, so I'd rather not have them regularly fail on me.

But they have a predictable life. And you can see them beginning to fail by watching the battery meter.

We clearly approach power systems very differently, though. I'm willing to spend the money to have something reliable with demonstrated performance, for where I make my living. You seem to value "low cost over everything," which is fine, but I doubt it beats the power grid for uptime (my office does).

There is no reason I'd have anything less than 100% uptime. And for the same cost I end up with more power.

You talk about depth of discharge, but obviously with changing weather patterns, any battery system will normally not be discharging very deeply, because you'll have enough battery to cope with the odd terrible times where there's no sun at all. So it doesn't really matter if those few times wear the battery out a bit, because they're rare.

And I'd also have a diesel generator programmed to charge the batteries when they drop to a certain level, so I can enjoy power in winter. Depends on the price of diesel and more solar panels.

but I doubt it beats the power grid for uptime (my office does).

Here the power grid has gone down no more than twice in the past 10 years. There are parts of UK where it isn't as good as Cambridge but most of the country it is pretty good.

It's rare here too in central Scotland, but I do for some reason regularly (sometimes a few a day, sometimes a few a month) get 1 second dips, enough to cause some computers to crash or shut down. Hence I use UPS.

Off-grid I'm planning is for two reasons. Overall it's cheaper. The place I'm going to buy is most likely not served by the grid without paying an astronomical fee for cabling a long distance.

I've only ever done the 0.5C. If it can do that it should be fine?

Guessing here but even if the o.5C test on its own shows fine, a significant difference between the two would be suspicious?

Perhaps, but I usually find with any product, it's easy to find a defect. I've got dozens of free Lithium cells (as in AAA, AA size) because I know perfectly well they misadvertise the capacity. When you get angry with a Chinese Ebay seller, they give you a full refund and don't want it posted back at great expense. You don't even need to bother with an electrical test, just weigh them! You can do the same with USB sticks. 32GB stick for free? Easy.

If this battery is genuine, and I've never had a fake anything from Aliexpress, this is worth getting instead of Lead Acid. It's under twice the price of Lead Acid, instead of 7 times the price from UK suppliers.

https://www.aliexpress.com/item/1005005790696143.html



And I also got to thinking.... before we were talking about higher voltages being more efficient to transmit. But if I placed these batteries in the computer room, they could directly feed the 12V GPUs, as there would be no power line losses. Saves on invertors and 12V PSUs. It's probably also possible to get a PC PSU that makes the 3.3V/5V out of 12V. And I could just use 12V invertors for mains supply instead of the 48V I planned, then there's no complications of using a load of current off one of the 4 in series.

And I'd also have a diesel generator programmed to charge the batteries when they drop to a certain level, so I can enjoy power in winter. Depends on the price of diesel and more solar panels.

A friend living about10Km from me is completely off grid. He has I think about 7KW of panels. (He used to have just 5. Since adding the extra 2KW plus a 500W wind turbine, the only time he runs the diesel generator now is to check it is still working. Though that may be more about no longer having two teenage daughters living at home!

If this battery is genuine,

If of the same standard as the ones being sold by one local supplier here almost unbelievable value. (The ones I have just been looking at are over 4 times the price for a lower capacity. Though they do have ports to interface with some of the inverters that monitor the battery health. I don't know how much adding those ports and the electronic gubbins increases the price.

A friend living about 10Km from me is completely off grid. He has I think about 7KW of panels. (He used to have just 5. Since adding the extra 2KW plus a 500W wind turbine, the only time he runs the diesel generator now is to check it is still working. Though that may be more about no longer having two teenage daughters living at home!

How do these people get away with it? You can buy a "250W" solar panel on Ebay for £19 brand new, which is 28cm x 53cm. According to Wikipedia, the sun at it's highest delivers 1050W per square metre, and these panels are managing to absorb 250W in an area which only receives 150W. The best solar panel made to this date is 49% efficient. These are alledgedly 167% efficient. They must suck it from a parallel universe. They even admit the power output is 5.67A at 18V, multiply those together and you get 104W, not 250W. Even 104W would be 67% efficient, which is better than any panel ever made. I'm reporting them to Ebay customer service, that is against interdimensional law.

Genuine ones seem to be £145 for 250W. So your friend has 4 grand of panels, bloody hell.

Hang on, this might be real: https://www.aliexpress.com/item/1005005792141491.html - £42+VAT for 200W.

I'll probably be getting an LPG generator (35% less fuel cost and runs quieter), I've seen 8kW for a grand, although I didn't spend long looking for bargains. I'd charge the batteries with it, not use the power directly, so I can run it for shorter periods.

If this battery is genuine,

If of the same standard as the ones being sold by one local supplier here almost unbelievable value. (The ones I have just been looking at are over 4 times the price for a lower capacity. Though they do have ports to interface with some of the inverters that monitor the battery health. I don't know how much adding those ports and the electronic gubbins increases the price.

The one I linked to has internal equalising and protection against short/overload/overcharge/overdischarge etc, and tells you how full it is and what temperature it is. They are made in China and that's direct from the manufacturer. An Aussie I saw posting in a solar forum does buy them that cheap, from China, and they work. AliExpress isn't so full of fakes as Ebay. Still, I'd be testing that battery when I got it!

Over 4 times that price, and you'd be better with Lead Acid.

Tee hee, counterfeit investigation now underway for four sellers of fake panels on Ebay. I wrote a nasty report with the above explanation and they're looking into it. The online chat function from 8am on a Sunday is nice.

Tee hee, counterfeit investigation now underway for four sellers of fake panels on Ebay. I wrote a nasty report with the above explanation and they're looking into it. The online chat function from 8am on a Sunday is nice.

I have reported a similar scam on faceache.

Genuine ones seem to be £145 for 250W. So your friend has 4 grand of panels, bloody hell.

Probably more. The original 5KW is about 15 years old now and they have come down a lot in price since then. Installing was probably cheaper than most of us pay though as they were put on the roof when the house was built.

Genuine ones seem to be £145 for 250W. So your friend has 4 grand of panels, bloody hell.

Probably more. The original 5KW is about 15 years old now and they have come down a lot in price since then. Installing was probably cheaper than most of us pay though as they were put on the roof when the house was built.

I will not be paying anyone to do anything, it gets done myself for a fraction of the price. My Aunt actually paid £700 to get a car charging socket fitted to her house. I can get a used one on Ebay for £100 and connect it myself.

I might give the https://www.aliexpress.com/item/1005005792141491.html - £42+VAT for 200W a try. Flexible!

Did you know you can put them on other things than rooves? Vertically on south facing walls they will work (75% as well). You even get 25% on a north facing wall! Cover the building in them! Make a tent out of them!