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
http://svjohannarose.blogspot.com/
> On Dec 1, 2015, at 2:41 PM, cnc-list-requ...@cnc-list.com wrote:
>
> Date: Tue, 1 Dec 2015 13:35:47 -0600
> From: Josh Muckley <muckl...@gmail.com <mailto:muckl...@gmail.com>>
> To: "C&C List" <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>>
> Subject: Re: Stus-List small start battery for yanmar 3hmf
> Message-ID:
> <CA+zaCRDYHHvhgSFAXTjBNTGi+kBaRT=bqnnihvrq-kjum-m...@mail.gmail.com
> <mailto:CA+zaCRDYHHvhgSFAXTjBNTGi+kBaRT=bqnnihvrq-kjum-m...@mail.gmail.com>>
> Content-Type: text/plain; charset="utf-8"
>
> Paul,
>
> When this discussion came up in the past someone quoted the yanmar owners
> manual as stating that the minimum CCA of a starting battery should be 200.
>
> I really appreciate the added research into the eqAh rating. That is some
> misleading bullshit.
>
> As for charging at the rated amperage of 10amps the IIRC the echo-charge
> will charge at up to 15 amps. Maybe close enough to not cause any problems.
>
> It probably wouldn't be ABYC compliant but the li-po jump starters come
> with a cigarette lighter re-charge cable. It would be possible to hardwire
> power to the charger from the house batteries AND hard wire the alligator
> clamps to the starter. This would ensure that only the li-po started the
> engine and that it only got charged by the appropriate charger.
>
> Josh
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