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Forum Index : Electronics : Inverter batteries...
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
Hi everyone.  I just have a quick question about batteries for the battery bank on any inverter. Generally speaking, you use deep-cycle batteries, but is there any reason - and I know there will be - for not just using multiple car-batteries or even a bank of those bigger truck batteries? They can accept a large charge current, and can also supply a very large dischage current too. I would have thought that a bank of truck batteries would have been just about perfect for capacity etc, and would not break the bank as they are not as expensive as the deep-cycle batteries. However, I am quite sure I am missing something obvious here to all you inverter folk, so it would be good for me to understand this a bit more before I start looking at batteries. Thanks to anyone who replies. Smoke makes things work. When the smoke gets out, it stops! |
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| joebog1 Senior Member  Joined: 07/11/2015 Location: AustraliaPosts: 114 |
What happens when the sun dont shine? and da wind dont blow? You pull the batteries down below the "sort of" specified "low voltage" Truck batteries are same like car batteries, that is, they are designed to give 1000 amps for 3 seconds, NOT the other way around. MOST ( not all) are "pasted construction" which means the active lead and lead oxide are smeared onto a grid ( a little like plastering wattle and daub) its VERY easily dislodged with the batteries internally generated heat. This results in the "oxides" previously painted onto the grid wires, dropping to the bottom of the battery, causing shorts, which is why its almost always one cell failing. Deep cycle batteries are designed to go to a much lower "end voltage" before they are charged back up ( after a cloudy day, for instance) They cannot handle as big charge currents as a truck battery, NOR can they handle as big discharge currents as a truck battery. Like most car batteries, or truck batteries they are made MOSTLY for the producer of the battery. ( "let em change it every two years" attitude ). As a general rule, deep cycle setups are mostly designed by someone with half an idea!! That means that some effort ( and maybe a little math) has been expended matching the whole system together. Year ago we fitted a LARGE 24 volt solar system on a tropical north queensland island ( Bedarra Island) All was functioning well. The owner then made one of those naughty movies, with multiple girls blow dryng their hair every 10 minutes. One hour and we had a VERY angry producer, er I mean owner complaining the inverter had shut down. After a 3 hour drive, and a half hour boat ride, we arrived to see the most beautiful crystals built up on the 700 AH BP solar batteries ( biggest easily available at that time). What they did was take BIG power over a short time which resulted in the worst sulphating I have ever seen. Three days of trickle charging with a baby generator started the rebuild, but those batteries were never any good and required replacing a few years later ( worth many thousands of dollars, at that time one 2 volt cell cost $900!! multiply that by 12 cells needed). If you are miserly with your usage, and really keep in mind what you are using as far as energy goes, you will survive a few years. BUT, truck batteries are "consumable" Well maintained deep cycle batts "should" fetch at least 20 years, even though thats outside most of their specifications/guarantees. I hope I have sort of explained it a bit!! Im not very good at writing stuff down, but I hope it helps Best regards Joe |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
Awesome explanation, thank you very much. I understand this 100% more then I did before. Thanks. Anyone else feel free to comment too, but I have my answer. Smoke makes things work. When the smoke gets out, it stops! |
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Madness Guru  Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I use secondhand golf cart batteries, the way they charge them they get Sulphated. Good news is if you give them a good charge and Equalisation charges they work quite well. Not all come good but plenty do. They are deep cycle batteries and I buy them for scrap price, those that are no good I sell for scrap price. If you have any golf cart suppliers in your area or golf courses it is worth asking. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I started off with 100Ah calcium LA batteries, still have 400Ah/24V system supplying power via a separate inverter to all the lights in the house. A very light duty for these batteries but some are getting 7 years old now. This bank originally supplied power to my house too but I *really* had to baby the supply and do load shedding (connecting back to mains power) if it was cloudy. Then I changed the power side of my house to lithium batteries. Its now a 200Ah/ 48V bank. What a difference! This was my best decision ever. Yes, they were expensive and I had to make a special cell charge equaliser (did not trust the commercial ones) but what a difference in battery performance. There are 3KW of solar panels to feed the Outback MPPT regulator and I've seen 60Amps going straight into my batteries with no complains. These batteries can take whatever charge I can throw at them. These batteries can supply power right to the maximum of the inverter's capacity (8KW power jack conversion at the moment) with very little voltage sag. The lithium bank has now been in use for over 2 years and, since they rarely get drawn down to 50% capacity, I expect them to last many years yet. Klaus |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
@ Madness - good idea, will check that out. We have two retirement villages here, and plenty of those mobility scooters zip around the place. @ Tinker - Dear I ask.... How much was 'expensive', and where did you get yours from? The battery rep is going to be here on Monday, so I will ask him about their range of deep-cycle batteries and get some prices/makes/models etc. Smoke makes things work. When the smoke gets out, it stops! |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I got them from forum member Trev. Search the member list for Trev to get his contact details. No idea how much they are now, the price relates to the dollar exchange ratio. Klaus |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
One option would be to get a few thousand 18650 batteries and a 3D printer and make your own version of the Tesla batteries. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Well i have just added a few more 18650 batteries to my setup, now running 1690 of the bloody things, just takes a lot of messing around testing and wire them up before i put them in the box I will come up with better idea next time if i do this again. Cheers Aaron Cheers Aaron Off The Grid |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
Now THAT is a brilliant idea.  Never thought of that at all, but a quick look on Mr. Google, has revealed lots of links to pages and YouTube videos of people doing this very thing. Another option to consider at any rate. @ Revlac - how do you find your pack of 1690 cells works generally speaking? Smoke makes things work. When the smoke gets out, it stops! |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Surely, you guys must be kidding to even consider heaps & heaps of 3.4Ah lithium batteries connected up to make a useful alternative energy storage to power a house. You need about sixty of them just for one of my 200Ah lithium cells. And I have 16 cells, so that is 60X16=960 cells. Just remember this: a chain is only as strong as its weakest link. And there are 960 links in that 18650 battery idea to go awol. Beside, balancing that monster looks like a nightmare to me. Unless the batteries are free and have a good life left perhaps as a challenge to power a bicycle the idea might some merit, but a house  Klaus |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Tinker that is exactly what is in the Tesla cars and Power Wall, sound strange but it is true.  When I said you need a few thousand I was not over stating it. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
@ Grogster the batteries have being running the house vary well no problems at all. some of the cell's are up to ten years old all of them were secondhand, As for cell balancing its series parallel (I think thats how Tesla has done it) so there is only 13 cells or sets to check, full charge is 53.2volts and down to 49volts in the morning . I check them once a week and balance the every 2 weeks it's less than .1 volt to balance anyway. I have spacers between all of the cells (fireproof) and if some go bad it shouldn't damage any others, Well I Hope Anyway. We all take our own chances doing these things, Nightmares too. I did start off a year ago with 4 truck batteries running the house during the day and then back to grid in the afternoon, All off grid now. However will use the truck batteries again to run the workshop during the sunny days as will be a separate system from the house, 002 inverter build still testing and building it, the solar panels will take the load not so much the batteries. @ Tinker These cell were free, may not be next time. Aaron Cheers Aaron Off The Grid |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
Fascinating - I would love you to post a photo or two of your setup..... Smoke makes things work. When the smoke gets out, it stops! |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Thanks Madness, for that picture - I did not know they use tiny cells. Perhaps these make it easier to mold the battery into odd shapes. But the connecting side looks like a nightmare. Perhaps a robotic assembly? Revlac must be truly dedicated to tackle something like this, good on you if it works. Just for comparison, my 16 cell 200Ah lithium battery bank shows full charge (floating) at 54.7V. I have never seen this bank below 53V. But I try not to use power hungry devices if its overcast two days or longer in a row. My clever solar controller tells me it takes around 5-6 KWh to recharge this bank. That, of course, includes the power used during sunshine hours. So this is what I'm using, one person, small house, decent workshop. Klaus |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Sorry Grogster no photos yet i would like to tidy it up bit and there is a few more improvements to still to make. There are some solar pumping stations around that don't need batteries some in 3PHASE just use a lot of panels, could make cheap power plant for sunny day use bit like a GTI without the grid power consumption over night was 3.5-4KWH last time i checked Small house 2 of us here, large tv,large fridge,1 large deep freezer 1 small deep freezer running most of the night, lots of other things running during the day 2x air-cons and so on. OK back to spectator mode. Aaron Cheers Aaron Off The Grid |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
the tesla battery pack is basically flat, it forms the underfloor and part of the chassis. refereed to as a skateboard configuration. 2 rows of 7 modules and an extra pair stacked in front for the bigger 90 and 100kw pack to give a total of 16 modules. unfortunately I am addicted to Bjorn Nyland's LOOOONG Vlogs about road tripping Tesla's, I have spent hours watching him charge those damn things. I think the 100D charges to 402 volts and has 8,256 cells so that would be 86 cells parallel by 6 cells series per module. I was hoping it would be 7 cells in series because that would be a perfect 14 cell/ 56 volts with a pair of modules for our 48 volt systems. I am toying with the idea of building a spot welder to Ian Hoopers design and making a few ebike packs. I am still a bit shy about buying 18650 cells just because of the sheer number of counterfeit cells in the market. I'm confused, no wait... maybe I'm not... |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
We are living in a golden age for renewables, cheap panels, cheap inverters and so on. Cheaper batteries and cheaper electric cars will be the next game changer. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
The only thing stopping EV's having the same range as petrol or diesel powered vehicles is the battery technology, really. That, and the recharge time. Even a fast-charger will be about 1000 times slower then just filling up the tank again, but that MIGHT change with time and technology. EV's have many advantages over fuel-powered vehicles IMHO. But then - I would say that, being that it is an area of interest for me.  Back on topic, yes, it seems that eBay is infested with FAKE 18650 cells, so perhaps the best bet is to indeed start collecting dead laptop batteries, and strip them for the GOOD cells. That seems to be what everyone who is building power-walls of their own is doing, and it is also very cheap as dead laptop batteries are basically worthless as a laptop battery, so you can pick them up dirt-cheap just to extract the good cells. Weather this is indeed worth all the effort...... I guess if it works..... Smoke makes things work. When the smoke gets out, it stops! |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
No, we are there now, the latest generation of road cars (not city cars)are charging in the 65-100kw per hour range so a 30 minute charge will get you 250km+ and the ranges are around the 280-320km with the latest tesla doing 450-530km. the bottleneck for us will be the charging network, although there has been three Tesla's charging in my town on a Perth to Sydney trip. the best point to start from is to know your battery, battery bro have a pretty good list of what is out there, its pretty satisfying when I pop open a cordless tool and instantly recognize the cells. I am inclined to agree with Tinker, the LiFePo4 cells really do shine in the off grid application for a smaller system. there is a way to fast charge AGM cells but it involves coulomb counting in the bulk charge phase at high voltage then cutting back as we hit 80% soc. That was my goto build for portable packs until lithium come onto the scene, it would still be cheaper but one mistake and a cell is toast. I'm confused, no wait... maybe I'm not... |
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