Martin,
Let me give a slight addition to the comments on Lithium batteries. I electrified a boat with LiFePO4 batteries for one reason: high energy density. My 160 Ah 48v nominal bank weighs 200 lbs. With my Torqeedo 4R, I got my 15' aluminum utility up on a plane for 25+ miles. You do have to exercise some care in charging and monitoring but it is not very difficult or expensive. A 25 amp 48v 3-stage charger designed for Li costs about $500. A mini-bms battery management system is about $200. You can spend much more but these are completely adequate for marine applications. I had no difficulty in locating a source for the batteries. There is a large market created by the diy electric car people.
However, if you are converting a sail boat or other application where weight is not an issue or even may be an advantage then definitely go with the AGMs. They are much cheaper initially.
If you need more help on LiFePO4s let me know.
Ned
On Jan 28, 2012, at 7:47 AM, Bill Heintz wrote:
On Jan 26, 2012, at 09:44, martin demers wrote:I would like to know what is the advantage with Li -po batteries in boatsA very good question Martin. [and I'm not sure I am qualified to answer ;)]I chose AGM (lead acid) batteries for my boat for pragmatic reasons:I'm not a battery expert, and where I hope to travel, I don't suppose I will find a whole lot. AGM's were a smaller initial investment, it is easier to charge, and [I think] I understand the chemistry of it enough to charge them properly and keep them sufficiently maintained. If I travel and need a replacement, I can quickly get a replacement. Until my wallet starts to get too heavy I will probably stick with lead acid.On oversimplified comparison . . .Lead Acid: (includes flooded, SLA, VRLA, AGM, and GEL)Advantages: cheaper, proven technology, easy to replace, chargers are readily available, a large bank of batteries can be charged all in series, no memory, high over-charge toleranceLimitations: heavy (30-50 wh/kg), cannot be left in a low-discharged condition, a deep cell battery has perhaps 300 cycles, high internal resistance, takes a while to charge (8-16 hrs), contains LeadLi-Polymer: (LiCoO2, LiMn2O4, LiFePO4, LiNiMnCoO2, LiNiCoAlO2, and Li4Ti5O12 to name a few see Notes below)Advantages: lighter (100-130 wh/kg), can be made environmentally friendly (no Pb, Cd, or Hg), 1,000+ cycles, no memory, lowest internal resistance of rechargeable batteries, faster charge (2-4 hrs)Limitations: expensive, charging properly is critical, chargers are expensive, (each cell needs to be monitored and charged individually when charging), low over-charge tolerance, hard to find a dealer that will sell you one suitable for a DIY-EV boat (24-48vdc boats are either too big or too small)In the Title Post, the battery chemistry refers to Lithium Nickel Manganese Cobalt LiNiMnCoO2 (NMC)Notes on Lithium Ion (Li-ion) and and Lithium Polymer (Li-po)†:• Scientists and the media give Li-ion batteries unique names but unless you are a scientist, this might cause confusion.• The polymer hype of the early 2000s is still going strong, however most users cannot distinguish between a regular Li-ion and one with polymer architecture.• All Li-ion polymer cells today incorporate a micro porous separator with moisture. The correct term is "Lithium-ion Polymer" (Li-ion polymer or Li-polymer for short.)• Li-polymer can be build on many systems, such as Li-cobalt, NMC, Li-phosphate and Li-manganese.• As far the consumer is concerned, the lithium polymer is essentially the sam as the lithium ion battery.† - Batteries in a Portable World - Isidor Bunchmann - pp. 59-60. See also "Battery Types" on www.BatteryUniversity.com, an up-to-date reference for comparing different battery chemistries.Types of Li-ion batteries: Table 2-10†
Also Lithium Cobalate or lithium-ion-cobalt)
(60% Co)
Manganese Oxide1
Also Lithium Manganate
or lithium-ion-manganese
e-bikes, EV, medical, hobbyist.
Iron Phosphate1
(10–20% Co)
9% Co)
in electric powertrain and grid storage
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