diy solar

diy solar

39 year old flooded batteries

I remember almost panicking when I reached 39... :)
... and I live in a country with a life expectancy of around 83. But then, it was obviously about quality of life ;·)
Actually, I semi-panicked more at 29. By 49, I had got used to the idea. At 59, 'What, still around? Can't be too bad'. At 69... haven't got there yet. And I don't think it's very likely I will (well, hopefully :·)

Still, with a life expectancy of, what, 20 years? one has to admit they're doing all right ;·)
 
Just for clarity, what's your definition of shallow discharge?
If the power stays on and my generator works correctly the batteries will be on discharge less than 2 hours per year. So very shallow depth of discharge.

I think temperature controll is a big factor. Have you noticed than many new cars have the battery in the trunk, out of the hot engine compartment.
 
... and I live in a country with a life expectancy of around 83. But then, it was obviously about quality of life ;·)
Actually, I semi-panicked more at 29. By 49, I had got used to the idea. At 59, 'What, still around? Can't be too bad'. At 69... haven't got there yet. And I don't think it's very likely I will (well, hopefully :·)
Fun fact:
Life expectancy at birth is not the same as life expectancy once you've reached a given age. Life expectancy increases as you get older.
 
If the power stays on and my generator works correctly the batteries will be on discharge less than 2 hours per year. So very shallow depth of discharge.
OK, that's not a lot! Such a cool pic.

I think temperature controll is a big factor. Have you noticed than many new cars have the battery in the trunk, out of the hot engine compartment.
I hadn't really noticed. All my cars have had them in the engine bay, including the latest one. Keeps the high current cable to the starter motor short.

My own battery bank will be subject to environmental temperature fluctuation. They are inside a timber housing which is under the wide eave of my home. We are a mild to warm climate. I kept an eye on temps in the housing this Winter and lowest in the housing would be ~15°C. Not sure what Summer temps will reach in there (it can get hot here) but I'm not looking to get 30 years out of them!

Discharge won't be a lot but definitely more than your telco centre batteries. A typical grid outage will draw about 10% of (nominal) capacity and we average 10-12 of those/year. Occasionally we'll get a longer outage so 50% of capacity ~= 15 hours, not including supplemental energy from solar PV. I can plug a generator in to boost charge if we have a particularly long outage (we've had a 2 day outage before).

Charging / float energy is normally supplied by solar PV on a typical daily cycle and there is a small constant load so they will draw perhaps 1% of capacity each night before solar PV tops up/floats them the next day. It's also programmed to supplement charging from the grid if required and the parameters for triggering grid charging vary depending on time of day (lower state of charge trigger early in the morning, higher state of charge trigger at end of day and variable trigger in between). The other thing they do is provide some electrical ballast as I have a pool pump which is supplied energy from the off-grid solar PV.

It's all an experiment really. I wasn't looking for a deeper daily cycling, just backup and ballast and the Powersys units seemed pretty capable and were not particularly expensive. Way cheaper than a 48V lithium option.

What I'm hoping for is that they received similar treatment to yours. The typical city based data/telco centres here would have pretty reliable grid supply, and would also have generators to manage the bulk of backup energy needs, so the batteries would be a fill in. I'm guessing they have a routine replacement period for their batteries. I load tested the first bank and it performed really well. Not load tested the second bank yet but they came from same supplier/batch.
 
It's a telephone office DC power plant.
It's why your phone and data still work when the power goes out.
Long (long) ago when I was an apprentice we visited one of the last Strouger exchanges in the UK (Bath IIRC).

The backup batteries were massive open-topped tanks although perspex covers had been retro-fitted to reduce evaporation losses (and keep apprentice fingers out of the acid). At least it made topping up easy (plastic bucket of distilled water).

Sadly I don't remember the details, most of these visits were made on a Friday afternoon and the pub beckoned!
 
OK, that's not a lot! Such a cool pic.


I hadn't really noticed. All my cars have had them in the engine bay, including the latest one. Keeps the high current cable to the starter motor short.

My own battery bank will be subject to environmental temperature fluctuation. They are inside a timber housing which is under the wide eave of my home. We are a mild to warm climate. I kept an eye on temps in the housing this Winter and lowest in the housing would be ~15°C. Not sure what Summer temps will reach in there (it can get hot here) but I'm not looking to get 30 years out of them!

Discharge won't be a lot but definitely more than your telco centre batteries. A typical grid outage will draw about 10% of (nominal) capacity and we average 10-12 of those/year. Occasionally we'll get a longer outage so 50% of capacity ~= 15 hours, not including supplemental energy from solar PV. I can plug a generator in to boost charge if we have a particularly long outage (we've had a 2 day outage before).

Charging / float energy is normally supplied by solar PV on a typical daily cycle and there is a small constant load so they will draw perhaps 1% of capacity each night before solar PV tops up/floats them the next day. It's also programmed to supplement charging from the grid if required and the parameters for triggering grid charging vary depending on time of day (lower state of charge trigger early in the morning, higher state of charge trigger at end of day and variable trigger in between). The other thing they do is provide some electrical ballast as I have a pool pump which is supplied energy from the off-grid solar PV.

It's all an experiment really. I wasn't looking for a deeper daily cycling, just backup and ballast and the Powersys units seemed pretty capable and were not particularly expensive. Way cheaper than a 48V lithium option.

What I'm hoping for is that they received similar treatment to yours. The typical city based data/telco centres here would have pretty reliable grid supply, and would also have generators to manage the bulk of backup energy needs, so the batteries would be a fill in. I'm guessing they have a routine replacement period for their batteries. I load tested the first bank and it performed really well. Not load tested the second bank yet but they came from same supplier/batch.
Try to keep the temps below below 80f if possible. Heat kills lead acid batteries.
 
Try to keep the temps below below 80f if possible. Heat kills lead acid batteries.
Thanks. I'll keep an eye on it.

It might be a challenge some days but we'll see. Mean daily max temperature in Summer months is 29-30°C (84-86°F). Obviously it can get hotter some days. Hottest day was 42.9°C (109.2°F).

The housing is up against the house, under a 2m wide eave and away from any direct sun. The floor is thick terra cotta tile on concrete slab. I have a digital temperature monitor with a temp probe on one of the batteries with a display inside the house so I can at least see it at a glance. I'm hoping the vegetation near this area and the pool as well will help to moderate the micro climate in that spot.

Battery temp monitor at the moment says 21°C in the housing while the outside temp is 14°C. We had a 31°C the other day but I didn't check the battery temp. Whether this temperature moderation works the other way (i.e. stays cooler inside the housing when it's hotter outside) I'll have to wait and see.
 
You guys are going all techie on these things. I'm just imagining dusting them all. Looks like you could eat off the shelves if you don't mind a little acid sauce on your lunch.
 
How can lead last that long? I have always been told they will only last about 5 years!

In the early 2000s I was an electrical apprentice and visited a backup power plant in Germany, which had the inters of a WW2 Submarine. (U-Boat)
That included the Diesel Engine, Generator and the Lead batteries.
Still functional 60 years later. They did start the diesel to demonstrate - no idea what the batteries where used for.

I thought some of you might find this interesting.
Here are a few pictures from work.
thanks! that was like a throwback :)

Lead is not a bad technology, it is very useful and recently there is more R&D development in this direction again.
There a lot of pros to lead in stationary applications and they are 100% recyclable - what lithium is not yet.

Further there are actually many applications where you need weight - like forklifts - and excavators, cranes, etc. When you try to electrify those - a big hunk of lead is ideal.
 
I work in a telecom CO myself and we monitor a good 1,000 of em or so. We have the same Powersafe G batteries at ours. 4 strings. Those round ones are very interesting design. Almost looks like standard buckets. Funny enough it has crossed my mind to look at the viability of DIY lead acid batteries and I thought of using buckets like that.

The nice thing about lead acid is you don't need to balance charge them and they can also be floated. This means it's very simple to setup, you string 24 cells in series to get 48v, float them at 54 volts, and attach the load to the same bus. You don't need any circuitry to ensure each cell is being charged at a specific profile etc or have to account for the actual load. Of course there will be some sensors like mid point voltage reading to monitor if anything goes wrong.
 
I wrote about those same round batteries in another post. A friend of mine works at a Telcom Satellite Up-link station on an island in the Caribbean and I was fortunate enough to see them Install the 50ft dish. They also had about 8-12 of those round batteries used as a backup in case the Grid went down. They only keep things going until the standby generator is fully up. That was back in the Mid 1980s and he tells me they are still in service today.
 
Just for clarity, what's your definition of shallow discharge?

Disharging anything less than about 5 percent of rated capacity is considered "short cycling". (if you are actually cycling, and not standby)

What short-cycling does is not allow for an overall smooth layer of sulfate to form nicely over the plate surfaces. The natural process of sulfation during discharge that is - not neglectful sulfation.

Instead, without a deep enough discharge of at least 5%, tracks and channels can form instead of a smooth surface during initial discharge and cause issues with parts of a plate and it's active material doing all the work initially in a repetetive shallow discharge environment.

So it's application dependent. The extreme would be purchasing a 100ah pure-lead agm and use it for charging your cell-phone and charging the agm back up again every time. (silly extreme).
 
Disharging anything less than about 5 percent of rated capacity is considered "short cycling". (if you are actually cycling, and not standby)

What short-cycling does is not allow for an overall smooth layer of sulfate to form nicely over the plate surfaces. The natural process of sulfation during discharge that is - not neglectful sulfation.

Instead, without a deep enough discharge of at least 5%, tracks and channels can form instead of a smooth surface during initial discharge and cause issues with parts of a plate and it's active material doing all the work initially in a repetetive shallow discharge environment.

So it's application dependent. The extreme would be purchasing a 100ah pure-lead agm and use it for charging your cell-phone and charging the agm back up again every time. (silly extreme).

Interesting. What you are suggesting is it would be good for the battery to have a little bit of modest cycling, e.g. down to SOC of ~90-95%, every so often?

What sort of frequency? Weekly, monthly?

Here is a chart of my SOC over the past month:

Screen Shot 2021-10-01 at 11.47.46 am.png

A couple of weeks back I finished off the project to double my storage capacity.

Since then, aside from a simulated overnight grid outage as a test run (8 hours, SOC down to 80%), the battery hardly gets cycled in normal operation. We had an actual grid outage on afternoon of 25 Sept which last 1.25 hours, and SOC dropped to 96%.

We have times of year (Summer) when grid outages are more common, while other times of year we can go for many months without supply interruption. Longest run without outage has been 228 days. The average is every 31 days. Anything >~5 min is classified an outage in my stats. Short "brownout" outages are not included.
 
I always kind of wondered myself if doing cycling once in a while is a better idea than constantly letting it full charge. I know doing equalize once in a while is good too but not sure if it's enough on it's own.
 
Must not be what the phone company backs DSL with, if the power goes out my DSL goes out about 5 minutes later.

I work from home and put my whole house through an inverter with PV and a battery, and was disappointed to find out the phone company only has about 5 minutes of power backup on their end.
 
Must not be what the phone company backs DSL with, if the power goes out my DSL goes out about 5 minutes later.

I work from home and put my whole house through an inverter with PV and a battery, and was disappointed to find out the phone company only has about 5 minutes of power backup on their end.
There must be another piece of equipment in the field that isn't backed-up. The DSL signal has a limited range so there is probably a piece of equipment in your neighborhood that has also lost power.
 
Could be that you have fibre to the node, and the node batteries are shot. They are typically not any bigger than what's in a standard UPS but setup as a 48v config, usually 8 12v batteries (2 strings). I've heard of techs being able to charge these with their truck in a pinch. Not sure if they just connect booster cables across 12v worth of batteries then move them around. With an actual generator then it just powers the rectifiers but often not worth dragging a big generator around for those.

I remember once talking to a tech over the phone, there was a problem with the generator cord or something, wrong type maybe, I forget. He got it going and he's like "You don't want to know what I did, but the site has power now". Gave me a good laugh. Some of the stuff techs need to do sometimes to keep stuff running.
 
I am a retired Telco field tech and Red Squirrel is correct, the fiber to the node has back-up batteries that can be charged from a portable gas generator when the grid goes down. The ones I worked with would lasted about 8 hours before they were dead, it also depends on the usage by the customers. ( more calls or more internet = shorter battery time) We would have to take portable gas generators to the node site after hurricanes to keep the batteries charged until grid power was reestablished. This could take weeks if it was a major storm and you had crews that would gas up the generators in the field for weeks, what a nightmare keeping portables generators running for weeks

We would also find customers near the nodes plugging extension cord into the extra plugs on the generators to use in their homes while the power was still out for lights or their refrigerators. We were good with that as the nodes used a small amount of power to recharge the batteries and people needed help.
 
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