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Here is a short and sweet question that I believe I know the answer to but I am not positive. Using the rated spec sheets provided by life line and looking at the 8 amp draw rate lets compare our choices. My question is about the 6 volt 300 amp hour battery that lists a 2205 minute rating at a 8 amp draw rate. Obviously I would need two in order to provide for a typical 12 volt system. I thinking I cannot double that 2205 rating even while using two battery’s. So this works out to be around 36 hours of capacity when subject to an 8 amp draw. Switching back to 2 large 12 volt battery’s like say the 30HT and using the same draw rate it sounds like my discharge time would be around 37 hours. Do these numbers and conclusions sound correct or am I missing something?
I am aware that the use of agm’s caution against full discharge. The math simply provides the total hours. Reading the literature makes it sound like only the top 50% of capacity should actually be considered available, am I correct to assume that?
Well, never having had AGM’s I can only speculate a bit…
Since AGM’s are still considered a wet-cell (with lower internal resistance), then the 50% DOD (depth of discharge) makes sense, this to avoid adversely impacting a battery’s longevity.
What’s less clear to me is the slight discrepancy between available minutes at 8a, considering that either arrangement would end up with 300a/hrs (gross, 150a/hr net) since either way, watt/hrs are still watt/hrs (watts = power)??
So I’m confused as well, but in realville I doubt you’d notice any kind of difference…FWIW, my 6v GC’s are now nearing the end of their life cycle, and after having some extensive ‘hands on’ empirical data with my *neighbors 12v 100a/hr Lifepo4 battery (31# cylindrical cell), compressor operation and solar harvesting, I decided on Li for the replacement and ordered a 200a/hr Lifepo4…
* Home-brew V-nose cargo trailer to hi-tech camper conversion.
Finally now getting some competitive pricing, so will be installing in the next few days (awaiting 0004 cables)…The two things that impressed me about Li (besides weight) is that the voltage stays relatively constant throughout the entire discharge (of nearly 100a/hrs – ideal for reactive loads where power factor (pf) really matters), running 11kbtu roof-top air conditioner, and that Li recharges uber fast even in marginal harvest conditions, this (unlike chemically sluggish WC) due to extremely low internal resistance…
Best Regards,
Phil
I had some time this week because of the rain so I made a call to Life Line. My assumptions turned out to be correct. The reps suggestion providing I had the space was to use the 16 size 6 volt. This set up would yield 53 hours and would provide the owner with 100 extra cycles.
Bottom line, weight, size and cost should be your criteria. Assuming you will only use 50% of the capacity two 12 volt 30Ht’s will weigh around 200lbs and will set you back nearly 1000 dollars. 18 to 19 hours at a 8amp draw will be your capacity. Two 6CT’s will weigh 180 and will give you 18 hours. There cost would be around 860. Two 16T’s will tip the scale at 238lbs and cost nearly 1400 dollars. Subjecting them to an 8 amp draw and using only 50% of there capacity would give you around 25-26 hours. Don’t forget I was told this battery will provide increased cycles.
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