LiFeP04 Batteries for Solar & BMS

[tasman]

I don't recall anyone saying there would be "problems" or it isn't possible. I believe what the majority are saying is it would be atypical to design and build a system capable of putting out 3000W at 12V. I would never consider it, but I'm glad yours meets your needs.

I wouldn't want to *build* such a system, let alone think about what problems might pop up. For my system, I needed 33,600 Wh of battery capacity @ 48V, or 700Ah. I would need 2800Ah @ 12V.

You use 700ah a day, what sort of equipment would use that much energy daily. The reality is, how much your system uses daily and how it will cope with spikes in use. not some fanciful figure you feel you may need. We are dealing with lifepo4, not 19th century L/A, past its use by date, junk. The differences are dramatic, especially charge times and usable capacities.

I understand my system doesn't suit the acceptable parameters, that's the case with lots of things and for me, it all boils down to economcis, reliablility and functionality. After all, innovation, development and creation of new systems, always comes about by those who challenge the accepted approach and make it work.

If we stuck with the accepted claimed reality, we'd all still believe in lead acid, fossil fuels, god and economic growth as our saviours. When the factual reality is the opposite and it's the same with all aspects of evolution. Experiment, challenge the norm, do it safely and responsibilly. Then you get real results, not perceived ideological ones. My approach works, is economical and safe with the energy reuiroments we need. The inverter seems over kill, but it means it never works beyond about 50% of it's capacity. This means it should last much longer than other inverter pushing 60-100% of its capacity constantly.

[Living Large]

I don't disagree with you, but been using the 3000-6000w 12v inverter for close to two years and never a problem. I expect if I was using 3000w+ continuiously, then there may be problems. But we never use more than 1500w and then only for the vacum cleaner which is supposedly 1800w. It all boiled down to economics, this was so cheap compared to higher voltage inverters, just couldntl go past it and ir works.

I don't recall anyone saying there would be "problems" or it isn't possible. I believe what the majority are saying is it would be atypical to design and build a system capable of putting out 3000W at 12V. I would never consider it, but I'm glad yours meets your needs.

I wouldn't want to *build* such a system, let alone think about what problems might pop up. For my system, I needed 33,600 Wh of battery capacity @ 48V, or 700Ah. I would need 2800Ah @ 12V.

[tasman]

Tas if you are mobile in MH aka RV, that is fine. But a wired home, 12 volt does not fit is all I am saying.

I don't disagree with you, but been using the 3000-6000w 12v inverter for close to two years and never a problem. I expect if I was using 3000w+ continuiously, then there may be problems. But we never use more than 1500w and then only for the vacum cleaner which is supposedly 1800w. It all boiled down to economics, this was so cheap compared to higher voltage inverters, just couldntl go past it and ir works.

[Living Large]

Tas if you are mobile in MH aka RV, that is fine. But a wired home, 12 volt does not fit is all I am saying.

Yes, my comment was directed solely at off-grid home use 2000W or above, and I believe others were as well. Not 1000W or below. At 1000W, you are at 80A or so - which is OK IMO.

[Sunking]

Tas if you are mobile in MH aka RV, that is fine. But a wired home, 12 volt does not fit is all I am saying.

[tasman]

I understand the psychics involved, that's not my argument, in a perfect world you'd use 24-48v, but it's about economics and availability. Now I'm retired (70), we travel for about 7-9 months of the year and decided about 2 years ago, after a couple of expensive electrical repairs which now know could have done myself for almost nothing, decided to learn how to do electrics and simple electronics myself.

Have always fixed most 12v faults in vehicles etc, but never things like lifepo4, inverters are energy systems. So that's where I'm at, understand what you're saying, but when looking at the economics, nothing computes for a reasonable outcome. To me it's much better to have a number of cheaper replacements than spend a heap on some brand name. We've only had one problem and that was a manufacturing fault, will stick with this approach until something make me change.

Have come across lots of people who accepted the professional approach and ended up with expensive gear and when it breaks down, they either have to travel for long distances to find a technician that can handle it, or wait for an expensive replacement or import. During which time they may not have any power and its the same with off gird system in lots of Aus, because of remoteness and availability of supply.

I use easily to get components, which are cheap and seem to work just as well as the brand name expensive stuff. My BMS is one which is for an EV cost juist over $200, the same quality with less progammabilty, costs well over $500. Mine has been reprogrammed for off grid, sadly they are no longer manufactured and luckily bought 4. They perform flawlessly and never had a problem, I've altered and continue to refine the operation, if I had the expertise I'd reprogram and re-engineer it so it does everything I want. But expect that will occur with the system I'm putting together using other simple cheap cell and battery monitors, once I fully understand how to put together what I want, properly.

Paid $225 for my 3000-6000w 12v inverter, similar in 48v is more than $2000, in 24v, from $900. In the years it has been in use, nothing has happened adversely, nor come across anyone else who has problems.

Have stated a number of times, which no one seems to listen to, use 12v in our MH for most appliances and a 1000w 240v inverter.

In our home everything runs through the 3000w 12v inverter and nothing runs on 12v. We have 240v LED globes and all other things run on 240v, including vacum, two large freezers, fridge, 65cm LED tv and sometimes a PA. If they were all used together then sure there would be problems, we switch off non required things to use something else (vacum or PA). Many times checked the inverter to see if it's effected and it's fine, no hot wires or anything that looks adverse. The distance between the battery pack and inverter, is less than 30cm and use the wiring that came with it. Could have got away with a smaller inverter, but prefer to use one that is idling along, rather than peaking at times. Doubt its ever used more than about 1500w and that would be for the vacum cleaner, everything else wouldn't make 1000w.

As for the economics, try buying 24v or 48v appliances for your MH at the same price and variety you can get in 12v, almost impossible. As it is my MH is 24v and have to convert it to 12v for some vehicle things, because they don't come in 24v cheaply and it's the same with internal lights, radios, small chargers, dash and reverse camera's, try getting them in 24-48v for the same price.

Hate that title, RV makes out you are a recreational of road vehicle, when in fact the majority are bitumen conga line travellers and spend the majority of their time in van parks. Which really makes them motorised caravans and not mobile homes.

Like real MH owners, we are completely self sufficient when we travel, even for fuel as all our vehicles and machinery run on veggie oil and my MH carries 1200lt of it.

[Sunking]

250 Amps DC, for a 3kW+ inverter @12V?

Copper cable the size of your wrist and takes a $3000 15-ton hydraulic compression tool to terminate that kind of cable.

[Living Large]

Why do they sell so many 1000+w 12v inverters if they are dangerous and inefficient, most I've seen use 1-2.5kw 12v inverters in MH's and 3+kw 12v inverters in their homes with no problems at all. There are only loses when energy has a long distance to travel to the storage or load, aren't there.

250 Amps DC, for a 3kW+ inverter @12V? It may be common somewhere, but I wouldn't want it in my house. When you start talking about 2000 or 3000 Watts, at 12V, the current becomes unwieldy and all the wiring associated with the PV and batteries is going to have to increase to larger sizes. And it requires larger current capacity charging equipment too. I'm new to this, but those are my thoughts.

[Sunking]

Why do they sell so many 1000+w 12v inverters if they are dangerous and inefficient,

Because consumers are trapped in 12 volt boxes, and ignorant. Same reason you can buy plug-in Grid Tied Inverters that are not legal to use, marijuana, cigarettes, tobacco, and automatic weapons. There is a lot of money to made off from fools. It is that simple. 12 volt cost more to install, operate, and are dangerous about 1000 watts. One can even argue 1000 watts is way too much. 12 volts is for toys and RV's. End of story. In an off-grid you would not use DC power on anything. You would use 24 or 48 volt battery with a 240/120 VAC inverter. 240/120 volt appliances and gizmos are a lot cheaper and way more efficient than a 12 volt toy model.

[tasman]

Lower voltage systems have more losses, and as Sunking says, over 1000W delivered AC, the current density just gets insane and becomes dangerous.

And then you have the issues with parallel batterys to get the enormous Ah required to support the loads.

Every MH I've come across using L/A or lifepo4 batteries uses 12v through 1000+w inverters and most off grid homes using inverters do the same.

Why do they sell so many 1000+w 12v inverters if they are dangerous and inefficient, most I've seen use 1-2.5kw 12v inverters in MH's and 3+kw 12v inverters in their homes with no problems at all. There are only loses when energy has a long distance to travel to the storage or load, aren't there.

[Mike90250]

.....Correct me if I'm wrong

Lower voltage systems have more losses, and as Sunking says, over 1000W delivered AC, the current density just gets insane and becomes dangerous.

And then you have the issues with parallel batterys to get the enormous Ah required to support the loads.

[tasman]

Beg your pardon. I do not know who told you this or where you picked that up from is FALSE.

12 volts @ 100 AH = 24 volts @ 50 AH = 48 volts @ 25 AH = 1200 watt hours every day of the week any time of day. All three can be made with the same 4-12 volt 25 AH batteries. At higher voltages I can use much smaller less expensive wire at higher efficiency.

Same applies to charge controllers. At 1000 watts you have to use a $600 80 amps controller on a 12 volt battery with much larger wiring. At 48 volts all I need is a 20 amps $200 controller and small inexpensive wire. No matter how you want to spin it higher voltage = higher efficiency and lower cost.

I understand what you're saying and the perceived savings, but it doesn't compute when looking at the real economic facts. I have 2x60amp programmable mppt solar chargers on my MH, (1000w), total cost was less than $300, 4x 60amp on my house (2000w) and will add more as I increase panels.

My theory is rather than use a single big controller, much better to use a couple of smaller ones, then if one packs it in, you still have energy input, even if it is limited. Also have two spares in the MH and two at home and as I bought them all together, got a great deal. My set up allows me to switch off sections of the panel grid if necessary, it's aligned with my battery pack charge cut off. People have commented on my set up, but there have been a number of occasions where we've come across other travellers who were experiencing energy problems because of controller break downs. It happened to us when we first set the system up, one of the controllers failed, just switched off half the panels and changed over the controller. It was a production fault so was replaced quickly by the suppliers. These mppt controllers have been operating for years without a problem, first on L/A, then gel, now lifepo4. That's when we switched to MPPT. after seeing the difference between what goes into a battery with PWM, compared to a MPPT on another MH in shade.

The availability of 24v and 48v appliances and accessories is virtually nil. So 24 and 48v is useless for using low voltage appliances, it's the same with lighting. Try finding 24v or 48v lights or appliances and you enter the non existent, or expensive zone down here. My panels on the MH are 12v and on the house, 24v, because of the distance between the panels and controller, plus they are cheaper here than 12v panels.

Which means for off road and off grid, you have to use an inverter, or stick with pure 12v, meaning you can utilise your energy better and cheaper. Why add cost to break down 24-48v to a usable 12v, when there is no need and it's cheaper. We have lots of 12 volt charged, or operated stuff which would be impossible to obtain using higher voltages. Then you have to go to 240V AC and transform the power back to 12 volts. It may be different in the USA or Europe, but in Aus and especially Tasmania, we are very restricted in choice.

When you have a system that's been running for nearly 2 years on lifepo4, used daily and has yet to reach top or bottom charge parameters, to me that's a very efficient system, with a good fail safe backup.

[Sunking]

I believe efficiency is determined by the cost and return of a system, so it's not very efficient to use 24v-48v when you have short runs less than a few metres, with 6 BS wiring, 12v is much cheaper because you lose capacity by increasing voltage.

Beg your pardon. I do not know who told you this or where you picked that up from is FALSE.

12 volts @ 100 AH = 24 volts @ 50 AH = 48 volts @ 25 AH = 1200 watt hours every day of the week any time of day. All three can be made with the same 4-12 volt 25 AH batteries. At higher voltages I can use much smaller less expensive wire at higher efficiency.

Same applies to charge controllers. At 1000 watts you have to use a $600 80 amps controller on a 12 volt battery with much larger wiring. At 48 volts all I need is a 20 amps $200 controller and small inexpensive wire. No matter how you want to spin it higher voltage = higher efficiency and lower cost.

[Sunking]

Now your using and very distorted example, I already knew and understand the efficiency of higher voltages over distance and energy medium carrying capacity with energy loss. However that doesn't equate when you are using an inverter, within a metre or two of the supply, nor in any situation with short wiring runs in a MH.

I believe efficiency is determined by the cost and return of a system, so it's not very efficient to use 24v-48v when you have short runs less than a few metres, with 6 BS wiring, 12v is much cheaper because you lose capacity by increasing voltage. The loses would be very minimal and you double your ah capacity with lower voltages, making your system much more efficient in it's use of stored energy. Higher voltages only become more efficient when you have long runs and seeking high HP energy outputs.

Wouldn't it be more reasonable to say, it is more effective to use higher voltages and wiring for long runs, but not more efficient because of capacity loses and cost. The cost if a 48v 500amp pack, is 4 times the price of a 12v pack and won't provide any more than a 500amp 12v pack over the distances and situations we are talking about.

Off course if you have 10-30m between your supply, and your storage or usage, then it makes sense to us higher voltages and wiring capacity. Our 350w wind generator pumps high voltages to the controller over about 20m, which is very efficient and sensible. But when it comes to storage capacity, to me it's much more efficient to get the most out of your pack and by doubling or 4 times the energy availability, to me is very efficient use of a system. Correct me if I'm wrong

Have forgot about the wiring between panels and controller, or systems that use 12 volt DC appliances like an RV. Even th e short wiring between battery and inverter use the exact same model I have used here. A 1000 watt inverter at 12 volts needs 100 amps or 25 amps at 48 volts. If given the choice higher voltage wins every single time. Go above 1000 watts and using 12 volts is extremely dangerous and expensive.

[tasman]

I did not say that, I said 200% more efficient. Big difference.

Let's assume two simple circuits of a 12 and 24 volt battery 100 feet of copper 4 AWG wire, and 2 500 watt Gizmos one rated for 12 volts and the other rated for 24 volts. The 12 volt battery and 24 volt have the exact same capacity. The 12 volt is 320 AH = the 24 volt is 160 AH. We use the exact same two 12 volt 160 AH batteries.

On the 12 volt system the gizmo draws 42 amps and looses 1.2 volts or 10% of its power (50 watts)
On the 24 volt system the gizmo draws 21 amps and looses .6 volts or 2.5% of its power (12.5 watts)

Having said that we could make the 12 volt system just as efficient as the 24 volt system. We would have to use 2/0 AWG copper cable instead of #4 AWG. 100 feet of #4 AWG cost roughly $70, and 100 feet of #2/0 cost $220. Which system do you use?

I would not use either of them. I would use 48 volts and only loose 1.25% of the power or 6.25 watts. I could use a little smaller battery and panel wattage saving me more money. Now you know why utilities use very high voltages.

Now your using and very distorted example, I already knew and understand the efficiency of higher voltages over distance and energy medium carrying capacity with energy loss. However that doesn't equate when you are using an inverter, within a metre or two of the supply, nor in any situation with short wiring runs in a MH.

I believe efficiency is determined by the cost and return of a system, so it's not very efficient to use 24v-48v when you have short runs less than a few metres, with 6 BS wiring, 12v is much cheaper because you lose capacity by increasing voltage. The loses would be very minimal and you double your ah capacity with lower voltages, making your system much more efficient in it's use of stored energy. Higher voltages only become more efficient when you have long runs and seeking high HP energy outputs.

Wouldn't it be more reasonable to say, it is more effective to use higher voltages and wiring for long runs, but not more efficient because of capacity loses and cost. The cost if a 48v 500amp pack, is 4 times the price of a 12v pack and won't provide any more than a 500amp 12v pack over the distances and situations we are talking about.

Off course if you have 10-30m between your supply, and your storage or usage, then it makes sense to us higher voltages and wiring capacity. Our 350w wind generator pumps high voltages to the controller over about 20m, which is very efficient and sensible. But when it comes to storage capacity, to me it's much more efficient to get the most out of your pack and by doubling or 4 times the energy availability, to me is very efficient use of a system. Correct me if I'm wrong