Sunday, Jan 12, 2014 at 13:28
The technology is not lithium-ion, it is lithium-iron-phosphate - LiFePO4.
Many members of our
Kimberley Karavan owners club have swapped out the 320 Ah AGM batteries for 260Ah or less of Lithium. When my AGMs die, I will too.
It is not a cheap exercise to do it properly, $2k to $2.5k depending on whether or not you need a new mains charger and a couple of other things. (In comparison a replacement set of AGMs for our vans is about $1300.)
But EVERYONE who's done it is ecstatic and say they would never go back. With 260Ah of lithium you get about 230Ah of usable power. With 320Ah of AGM, using the 50% rule, you get 160Ah.
There is a 70kg weight saving.
You don't need to faff about with multi stage chargers. Charge flat out until the battery is full and switch off or go to float. A solar charging system can deliver its full output until the battery is charged, whereas a system charging a lead-acid battery delivers full output in the boost phase, then spends a lot of time (ie, hours) throttled back for the absorption phase.
Our Karavans are power-hungry if you use all the facilities available. People with Lithiums typically recover to 100% after overnight use about 4 or 5 hours ahead of people with AGMs and similar useage patterns and charging equipment. So you are less reliant on a whole day of perfect sun.
You don't need temperature compensation, there are no corrosive fumes or chemicals, so no ventilation required. Batteries are robust, vibration and shock resistant.
A supplier here in
Sydney runs his car on four cells the size of Red Bull drink cans. He says they will out-crank a standard battery for that car.
Their discharge curve is flat, meaning they hold their voltage at near full-charge levels until nearly flat (about 10%, I believe), so all your 12V stuff gets a full 12V all the time.
They don't sulphate. Unlike lead-acid batteries they can live for long periods at partial SOC and then recover fully when a full charge is available, with little or no affect on calendar life.
High quality industrial lithiums are reported to be still going strong after 7000 (yes, 7 and 3 zeros) cycles. Cheaper domestic ones over 3000.
A set of heavily cycled Lithiums will likely outlast 3 or 4 sets or more of similarly cycled lead-acid batteries, maybe more - the technology hasn't been around in the domestic market long enough for that to be properly established yet.
What they DON'T like is over voltage and under voltage. Over-charge and over-discharge will kill them. The conversion kit that fits our vans includes a VSR that will disconnect in either of those circumstances.
They also need occasional cell balancing which is akin to equalisation in a lead-acid battery. A mains charger with a lithium profile, or a lead-acid charger with suitable switched voltages will do that.
Some mains and dc-dc chargers have settings that are suitable for lithiums, but they are a compromise. In many cases replacement will be required. Some manufacturers offer re-programming of their lead-acid equipment, and switch-selectable lithium profiles are beginning to appear on new recreational 12V products.
Those are about the only caveats I can think of.
Cheers
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