LiFePO4 - The future for off-grid battery banks?

[T1 Terry]

There is an alternative, that is to switch in a Mains to nominal DC power supply Diode OR'ed with the battery feed to the inverter. That way if the Power supply is enabled a little before the output of the battery falls below this point there is a smooth changeover. The only issue is the added conversion losses in the power supply/inverter. It also can be activated when the solar system misbehaves during the day.

There are many UPS type inverter battery chargers that can be used for this purpose. Either time triggered to switch to mains power to utilise the cheap off peak power in Aust, or switched by a low cell alarm on the batteries and switched back off after say an hr or so, allowing the battery to recover a bit and hoping the solar kicks in before another low voltage alarm kicks in.
I was planning to move to this type of set up, but now the ig gum tree out the front is gone, even in the middle of winter I have plenty of solar for battery charging.
As far as cost, roughly AU$4,000 for 720Ah of Li batteries, around AU$200 for 2 x 1000w PSW inverters from evilbay, around AU$5,000 worth of solar panel that I could buy now for $2,500, and I thought I was being clever getting them before the price went up but then I've had cheap power from them so.....
Cut a bill of around AU$500 x 4 times a yr 2 yrs ago down to around an average of $150, but that will come down more now the tree is gone. At AU$1,400 a yr saving on power it will take a while, but I have 100% reliable power now and my bills are going down while everyone else is screaming because they are going up, over 100% increase in the last 2 yrs.... so my $500 power bills may have been $1,000 now, my system has run 24/7 for over 2 yrs now. Looking at it that way, it's already paid for itself... think I like looking at it that way better

T1 Terry

[akb]

Switching to mains

This is basically what I did, the solar charge controller is set so when the battery voltage decreases, the controller clicks a relay which switches the load from inverter to utility, not synchronized, however but I notice no abberations in about 8 months so far.

There is an alternative, that is to switch in a Mains to nominal DC power supply Diode OR'ed with the battery feed to the inverter. That way if the Power supply is enabled a little before the output of the battery falls below this point there is a smooth changeover. The only issue is the added conversion losses in the power supply/inverter. It also can be activated when the solar system misbehaves during the day.

[choyak]

It is not 'free' at all, it is an interesting hobby for me.

I also removed a ton of typos.

[inetdog]

This is basically what I did, the solar charge controller is set so hen the battery voltage decreases, the controller clicks a relay which seeitches the load from inverter to utility, not synchronized, hosever but I notice no abberations in about 8 months so far.

Please read post #112 and tell us what your estimate is of your relative costs for "free" solar power versus grid power.
Thanks.

[choyak]

Good day all.....
I'm not very good at this forum stuff, but I guess it's correct to stay on topic.

I will use Headway 38120HP (Red Cells) for an off grid system.

I've seen people using this in type of system while on Grid safely with a
Generator style pony panel. So you could collect sun all day and store into batteries,
run the house clocks and low consumption items while no one is home. Continue to
use during the evening until more consumption is required, then switch over to Grid power.

This way you get the best of both worlds, a back up without fuel and using solar to supplement

Any thoughts?

Tommy L sends....

This is basically what I did, the solar charge controller is set so when the battery voltage decreases, the controller clicks a relay which switches the load from inverter to utility, not synchronized, however but I notice no abberations in about 8 months so far.

[SunEagle]

You mean a combination of a fuel cell to produce electricity and an electrolyzer to produce fuel? Storage of the hydrogen is a big problem.

I just heard about a different type of fuel cell that uses natural gas instead of hydrogen. These units are being used by a medical company B&D out in California.

I don't have any details but it sounded interesting.

[inetdog]

Has anyone thought of using a fuel cell?

You mean a combination of a fuel cell to produce electricity and an electrolyzer to produce fuel? Storage of the hydrogen is a big problem.

[bradash]

I'm looking into buying new batteries

My 3000 Ah battery bank is getting pretty old and will not hold charges for very long anymore, so I have started looking to replace all the AGMs with something else. I was thinking about trying LiFePO4 but have not looked into if it will work with my inverts yet.

Has anyone thought of using a fuel cell?

[Sunking]

Anyone found a good place to buy new batteries?

Wallmart sells batteries for cheap.

[inetdog]

Do you mean the original Boeing battery design did not have have cell balancers built into it? After a number of cycles, the cells would get out of balance and, obviously, you get a cell being overcharged and thermal runaway. You'd think that Yuasa or someone with any battery system construction experience would have done cell balancing and voltage monitoring per-cell. There are 13 year old kids playing with RC cars who know that multi-cell packs need balancing.

It does contain active cell balancing. But only a controlled shunt around each cell activated by high voltage. No detailed feedback to the separate charge controller unit and no record of individual cell voltages. Individual cell temperatures were not even monitored. The current capability of the shunt is seriously limited by the size of the wires to each cell.

The protective contactor that disconnects the battery from the charger in the event of over voltage, under voltage or overcurrent is a normally CLOSED contactor opened under battery power. I suspect that this may be what causes the battery to require replacement when it is over discharged, since the protective circuitry (contactor coil) will continue to draw power until the battery is irreversibly drained. Unless it gets to a maintenance facility before then.

The company that contracted the whole battery and charger system and the company that built the charger both sub-contracted the testing to Yuasa, the battery manufacturer, since they had no idea what to test.

Yuasa did not have much if any experience with the use of that size battery in an aircraft where it is subject to large air pressure cycles as well as wild SOC swings.

Finally, the charger supplier was very proud of their patented method of predicting end of charge that meant that they did not have to continuously monitor the battery voltage!!!

Visit PPRuNe (Professional Pilots Rumor Network) for a lot more information and speculation on the whole subject. There are two active threads:

http://www.pprune.org/tech-log/512398-787-batteries-chargers-part-2-a-3.html

and

http://www.pprune.org/rumours-news/505455-faa-grounds-787s-89.html

[SunEagle]

Do you mean the original Boeing battery design did not have have cell balancers built into it? After a number of cycles, the cells would get out of balance and, obviously, you get a cell being overcharged and thermal runaway. You'd think that Yuasa or someone with any battery system construction experience would have done cell balancing and voltage monitoring per-cell. There are 13 year old kids playing with RC cars who know that multi-cell packs need balancing.

Or someone at Boeing trying to cut corners to save money and believed a salesperson when they said the battery was a plug and play and wouldn't need to worry about it for 5 years.

[bonaire]

Do you mean the original Boeing battery design did not have have cell balancers built into it? After a number of cycles, the cells would get out of balance and, obviously, you get a cell being overcharged and thermal runaway. You'd think that Yuasa or someone with any battery system construction experience would have done cell balancing and voltage monitoring per-cell. There are 13 year old kids playing with RC cars who know that multi-cell packs need balancing.

[inetdog]

Ok, sorry. I did not know, that it's not allowed.

Regards
Falko Jahn
ECS

No problem, it has been taken care of. Welcome to the forum.
My biggest interest in Li at the moment is in following the Boeing 787 debacle. I am sure you have some opinions on what happened.
The design looks like it was done by somebody who did not really understand LiCo and none of the individual cell voltages were recorded, or even left the BMS inside the battery case.
I have much better feelings about LiFePO4.

[spacevoyager]

Much as I appreciate the reference, Falko, the moderators will see it as a violation of the no advertising, no links policy. If you can restate it as a suggestion for a web search rather than a URL is might be acceptable, but probably not.

Ok, sorry. I did not know, that it's not allowed.

Regards
Falko Jahn
ECS

[Beanyboy57]

Yes, we have developed a charge controller and bms System special for LiFePo4 and LiFeYPo4.
If you are interested have a look on our website.
www dot ecs-online dot org

If you have any quesions, about it, feel free to ask us

regards
Falko Jahn
ECS Team

Victron energy also have products for lithium charging and management.