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Lithium v AGM

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18 minutes ago, erice said:

"At the time of the crash, it was the only battery-powered glider in New Zealand."

You'd have to assume they won't be selling too many more here in the near future. 

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If you are interested in the size differences and electrical differences of lithium Iron Phosphate and Lead Acid AGM batteries,  I have started to put my battery compartment together this weekend.

idlerboat, as a 'super practical person' i am surprised that you would only see the weight factor as an advantage for lithium batts.  so, here's a couple of things i have found to be fantastic about m

I'm very interested in this. Which brand, how are they managed, what charging system you use etc. And if all that's shipping cost, you obviously bought these overseas from somewhere, not local. W

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3 hours ago, erice said:

am not a fan of lithium batteries on a boat

this is why


they always blame the charging......but personally i think there is something else going on that they don't yet understand


 The enclosure Boeing had to add is 185 lb (84 kg) heavier, negating the lighter battery potential.[61]


There are many many different types of lithium batteries available,  just stating that they are all bad in a sweeping statement doesn't make much sense.   The battery types they are quoting are lithium polymer batteries,  these have massive current draw capacity...I have seen Lithium polymer capable of a 100c discharge and have some of the highest energy v weight densities avalible...which is why they are in aircraft...But this amazing performance comes at a cost of them being extremely volatile and cell balance needs to be perfect. But they won't just catch on fire,  something in the system need to fail for that to happen and once that happens because the electrolyte is a hydrocarbon....petrol and diesel are hydrocarbons.  There is nothing magical going on that they don't understand with these batteries,  it will be a fault with the system looking after them as in the Boeing article they mention dendrites and these will form when a cell is over charged. 

Also these as with other lithium batteries they don't like to be fully charged and are happiest between 40 - 80% charged.  

The Lithium variant that are used on boats and generally all mobile applications are Lithium Iron Phosphate,  these are not capable of thermal run away.   They just die slowly and quietly with little fuss is not managed well.  You can shot them and almost nothing happens.  They are also by far safer than any of the lead acid battery family that you will have on your boat currently, Gel, Agm and flooded lead acid being the worst for safety [there are others].


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so the lithium iron phosphate batteries you speak of are not the lithium ion batteries that thermally ran away and caused these problems 4 years ago?



some good info here

Lithium Iron Phosphate (LiFePO4)
Lithium iron phosphate (LFP) has a lower specific energy and lower cell voltage than other cathode materials, it has the benefit of being very stable, which gives excellent cycle life and high specific power with much lower risk of thermal runaway, even if abused. This makes it the safest of the LI cathode chemistries currently on the market.
LFP are generally used in stationary systems. They are being used to replace lead-acid starting batteries in vehicles. Four LFP cells in series provide 12.8 volts, compared with a standard lead-acid battery 13.8 volts. There is some question as to how LFP batteries will fair in the long term as regular vehicle charging systems are designed to charge the battery at 14.4 volts continuously in operation (BU-205, 2018).


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11 hours ago, erice said:

so the lithium iron phosphate batteries you speak of are not the lithium ion batteries that thermally ran away and caused these problems 4 years ago?

No, different chemistry.  The hoverboards and the Samsung batteries, (and the batteries in the fatal battery glider story, mentioned above), were Lithium Polymer batteries or more correctly lithium-ion polymer (abbreviated as LIP, LiPo, Li-poly, lithium-poly and otherways) - the hoverboard chemistry was specifically LiCoO2 - Samsung was probably the same chemistry as are most small electronics.

Lithium Polymer is, (generally), no good on boat cause the nominal voltage is too high (3.6v - 3.9v depending on chemistry) and all of our electronics is designed to run at 12/24/48v and LiPo doesn't fit very well into that range.

Lithium iron phosphate batteries, abbreviated LFP, (generally), have the chemistry LiFePO4 and these are what you will find on boats and household solar installations, the nominal voltage is 3.3v which fits better with a 12v system and all the parts/things available that come for 12volts.

A new, (relatively speaking), player in town is the Lithium iron yttrium phosphate battery LiFeYPO4 - this is (according to the people that make them) superior to LiFePO4 but still has all the safety benefits.

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1 hour ago, waikiore said:

Still dont understand the cost versus what you really get with lithium types versus AGM, particularly when I have had a great run with AGM and comparatively safe also not requiring a specialised charging regime.

Well, thats pretty easy. Very basically - and please read the PDS for any you may consider using, but:

WAY more cycles.

Use of complete battery capacity (use till voltage drops, then recharge)

WAY WAY faster recharge - full charge source output until full, no charge tapering. 

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