It does not have to be that bad. I don’t remember the source at the moment, but I have seen some calculations showing that if you need a large bank and you are pressed for space and weight, the LiFePO4 batteries can offer a decent value. As you mentioned, you need about half of the capacity (in Ah) (due to deeper discharge cycle), so you need fewer of them. They weigh less (per unit of capacity), so you have substantially less then half the weight. And they take substantially less room. They would probably cost substantially more, but they would last more (substantially more discharge cycles). So you may need to compare the cost to several sets of the lead acid batteries. From what I have read and seen, the biggest kicker is the charging system. You would need a new alternator, a new (and sophisticated) controller, a Battery Monitoring System etc. Your $2500 investment in batteries might be just the beginning.
For anyone interested, I suggest this reading: http://www.pbase.com/mainecruising/lifepo4_on_boats&page=1. And this guy knows what he is talking about. Marek From: Dreuge via CnC-List Sent: Tuesday, December 01, 2015 5:10 PM To: cnc-list@cnc-list.com Cc: Dreuge Subject: Re: Stus-List small start battery for yanmar 3hmf Josh, I looked into this a bit more, and while I still think it is wrong to use “EqAh”, the concept is not as misleading as I originally thought. The claim is the depth of discharge for Li-Fe batteries is 95% whereas for lead-acid batteries this is 50%. In other words, a 110Ah lead-acid battery has only 55Ah of usable deep cycle capacity whereas a 110Ah Li-Fe battery would have 105Ah of usable deep cycle capacity. This would give a 6 Ah Li-Fe battery 12 EqAh_deep_cycle. [at this time the largest capacity is only 12 Ah (36 EqAh) ~$300] For engine starting, the capacity drain at higher loads is non-linear for lead acid batteries due to high internal battery resistance. That is 1A draw for 110hr would completely drain a 110Ah lead-acid battery, but at 150A the battery would drain out in 1/4 hr (or even much less, not 3/4 hr as 110Ah capacity suggests). The claim is that the Li-Fe batteries have much less internal resistance which why they use the “EqAh” (or AH PBEq). It is sort of like using Watts to measure lightbulb intensity. Below is an interesting exercise demonstrating why we likely have not heard much about Li-Fe battery for marine deep cycle use. *** Two energy-wise equivalent deep cycle battery banks *** Duracell EGC2 6V golf cart batteries [Batteries Plus $109.99 64 lbs] 12V 230Ah (115 Ah usable) battery bank (2 batteries) total cost: $220 total weight: 128 lbs LFX36A3-BS12 Shorai 12v 36 AH PBEq LiFePO4 Power Sports Battery [BatteryStuff.com $295.95 5 lbs] 12V 120Ah (114 Ah usable) battery bank (10 batteries) total weight: 50 lbs total cost: $2959.50 On the other hand, someone may be willing to spend $300 for a 540CCA battery that weighs in at only 4.96 pounds, has a foot print of Length 6.5" x Width 3.4" x Height 6.1”, and can be mounted in any orientation(even upside down). - Paul E. 1981 C&C 38 Landfall S/V Johanna Rose Carrabelle, FL
_______________________________________________ Email address: CnC-List@cnc-list.com To change your list preferences, including unsubscribing -- go to the bottom of page at: http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
