TECHNICAL INFORMATION ABOUT LiFePO4

There is lots of information available about Lithium Iron Phospate and lots of rumors as well. We have the experience and knowledge to try de-bunk some of those myths.

So you are thinking about lithium but your questions have yet to be answered.

Well hopefully we can help answer some of them here.

 

The benefits of lithium are:

Lighter, approx 30% the weight of Lead acid.

Safer, no harmful chemicals or emisions.

Smaller, less than half the size of lead acid.

More efficient, will charge from flat in about 3 hours and get upto 50% more power from your solar system.

Longer lasting, up to 10 times the life of lead acid.

Cheaper, over the full life cycle, lithium batteries are less than half the price of many types of lead acid.

 

The drawbacks are:

Expensive to buy, they will cost you 3-4 times the price of lead acid batteries, depending on the type.

May need to change chargers or solar regulators.

General information:

Lithium batteries are happiest in an environment that suits humans, don't charge or discharge outside the range of 0-45C.

Don't run them below 10 volts - our power pack units have a cutout that prevents you doing this.

Don't charge them above 15 volts- our power pack units have a cutout that prevents you doing this.

Don't leave them on float voltage above 13volts for extended periods.

When not in use for long periods, discharge to 50% and turn off all loads and charging sources.

 

If you have a coulomb counting type energy monitor, like a Victron BMV700, you will need to re-program it to the battery capacity, a CEF of about 96% and Peukerts to 1.05, Tail current 2%, Battery floor 10%. Call us if you need help to do this.

Your 240 volt charger needs to be one without a de-sulphation mode and preferably without a float, many are very close to the desired settings when AGM is selected.

Your solar charger should be MPPT or at least have no de-sulphation and float voltage below 13.3v. You can charge them from a car system when driving, a battery isolation switch like a Redarc SB112 is a good idea. A voltage sensitive relay will not work in a car , it is best to wire the relay to connect the second battery (Lithium) when the car is running.If you have  vehicle with a smart alternator, most cars since about 2010 have, you would be best to have a local auto electrician check the voltage to the battery.

 

IF YOU HAVE ANY QUESTIONS THAT I HAVE NOT ANSWERED HERE, PLEASE DON'T HESITATE TO CALL ME ON 0411 520 920

 

- PETER CLARK

WHAT SIZE PACK FOR ME ???

Not sure how to size your lithium battery pack, from our experience this is the size pack required for a given use. The solar panel size is recommended for fixed flat mounting and should give sufficient power for average use, if you are unable to fit the listed amount of solar your system may need external topup on cloudy days. If you are a light user, you may be able to go down one pack size, if you are heavy user it may be useful for you to go up one size. Run well you should be able to free camp and not have to run a generator, however if your solar panels are in the shade at times, the system may struggle. This table applies to a 12volt system and is not meant for domestic house supply system which would have to be larger.

 

SMALL SYSTEM, Replace 100ah AGM

Use - Lights, device charging - phone, computer, tablet.  

Power pack size - 75ah

Solar panel size. - 200w

 

MEDIUM SYSTEM, Replace 300ah AGM

Use - Lights, device charging - phone, computer, tablet, Small fridge 60l Engel/Waeco

Power pack size - 150ah

Solar panel size. - 400w

 

AVERAGE SYSTEM, Replace 400ah AGM

Use - Lights, device charging - phone, computer, tablet. Medium fridge 80l, small inverter to run microwave, kettle, toaster.

Power pack size - 225ah

Solar panel size. - 600w

 

LARGE SYSTEM, Replace 500ah AGM

Use - Lights, device charging - phone, computer, tablet. Two door fridge, inverter to run microwave, kettle, toaster.

Power pack size - 300ah

Solar panel size. - 800w

 

EXTRA LARGE SYSTEM,

Use - Lights, device charging - phone, computer, tablet.  Large fridge, large inverter, microwave, kettle, toaster.

Power pack size - 450ah

Solar panel size. - 1200w

 

MAXI SYSTEM,

Use - Lights, device charging - phone, computer, tablet. Large fridge, small freezer, full electric kitchen/galley induction hotplate. Full electric with no gas use is possible. Small airconditioner.

Power pack size - 600ah

Solar panel size. - 1600w

 

BATTERY MANAGEMENT SYSTEM EXPLAINED

For many people, coming to terms with the difference between the old Lead acid batteries that have been around since 1848 to the newer LiFePO4 takes a little getting used to. Batteries are made up of cells: in each cell is an anode, cathode and an electrolyte. A given chemistry has a given voltage and for a lead acid cell the voltage is 2 volts per cell. If you have a different anode, cathode and electrolyte the voltage may well vary, as is the case with LiFePO4, which is nominally 3.2 volts. So to make up a battery with a target nominal voltage of 12 volts, we connect a number of cells together. In the case of lead acid, there are 6 cells to make a 12 volt battery and LiFePO4 we combine 4 cells to make make a nominal 12 volts. The actual voltage varies of course because of the state of charge of the battery- a full battery will be a higher voltage.fridge, small freezer, full electric kitchen/galley induction hotplate. Full electric with no gas use is possible. Small airconditioner.

 

So why do lithium battery banks require fancy electronics to look after them, where lead acid cells don’t? 

 

When a lead acid battery approaches full it takes less charge, hence they need fancy chargers that reduce the charge as the battery nears full; this enables the lower performing cells to catch up somewhat and the cells with a higher charge just “gas off” which is exhausting flammable hydrogen gas. So they tend to self balance. One of the main advantages of Lithium iron phosphate cells is their ability to take full current right up to a full state of charge, thus reducing the charging time dramatically. Lithium iron phosphate cells do not like being overcharged or over discharged, and to protect them from these states occurring we recommend the use of a battery management system.

 

The battery management system usually involves a high voltage cutout (HVC) and sometimes a low voltage cutout (LVC). They also may have a temperature sensor that will keep the cells within a safe range. The better BMS also incorporate a method of balancing the cells to ensure all the cells are at an equal level of charge. It is however possible to use these batteries without one.

 

- PETER CLARK

CARE AND MAINTENANCE OF YOUR LITHIUM IRON PHOSPHATE BATTERIES

These batteries require very little maintenance, they do not need chemical top ups or other service like that.

The top of the cells with the vent on it should not be tilted at anything more than 45deg from vertical during use or storage to prevent electrolite discharge in the event of a stressed cell.

 

Before storing for long time, drain the battery to approx 50% state of charge, around 12.9-13.1v with no load. Remove all charging sources including trickle chargers and all load, including the voltmeter.

 

The batteries should be checked every few months that they are not going below 10 volts state of charge, 12 volts is better as a minimum and represents a battery that is at about only 2% of capacity.

 

Do not exceed the stated charge/discharge ratings for voltage and current, these ratings can be found on the information pages of this website.

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