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Batteries - DOD Life Cycles


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Conversation around a campfire came up about DOD Life Cycles. One gent said you could use your total history of AH's Out divided but the total DOD Life Cycles rating of a battery bank, to get an approximate measurement of Life Remaining. 

Say: 75,000 AH's out/600,000 (600AH Bank X 1,000 DOD Life Cycles) = 0.125 (So ~12-13% of battery life consumed, with 87-88% remaining)

This sparked input from others about:

-Cutting the 600,000 in half, to represent 50% SOC

-Using both Total AH's Out and thus Total AH's back In, as this is the 'traffic' thru the battery bank (So 75,000 Out would be 75,000 In = 150,000 total AH's traffic thru the battery.)

-Adding a 5% per year battery capability from aging (Nominal/Medium bank usage, up to 10% per year Heavier bank usage.) (Some input that this should be different for Wet vs AGM, due to higher potential erosion of Wet then AGM. Arguments of doubling the aging factor met substantial resistance, but the brain collective of this campfire did feel that some higher aging factor should be used for Wet. Say 7.5% for Nominal/Medium usage, and 15% for heavier usage (Me? I would would have added a smaller increase factor of 25% vs 50% so 6.125% up to 12.5%)

-Battery lifetime environment, would also have an impact on the aging factor of a battery bank. A harsher environment of say much higher temperature, or lower temperature, usage environment - could accelerate the aging.

Say above 12-13% + 25% of usage (For a Nominal/Medium used battery bank that was 5 years old.) = 37-38% of battery life consumed, with 62-63% remaining. (Assuming AGM Battery Bank in these examples, and in good battery environment usage.)

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I'm not sure about cutting the bank in half to represent 50% SOC preferred usage of a bank. Seems to me it would be all about DOD, which is the math of a batteries rated size X's DOD Life Cycle?

With good metering systems, even if they're off + or - by say 5-10% from actuals. The logic of the math about battery life used vs remaining passed my filters. And, as batteries, even AGM's, do have a finite amount of the 'stuff' (Techie talk about what makes a battery work:)!) that supports them, this will also deteriorate over the years (Thus, the DOD Life Cycles ratings.) And I felt the combination of Out/In AH's volume 'traffic' was more meaningful.

So adding up AH's Out/In volume, adding on some aging errosion of total life capacity by years, did seem to make sense to me - in giving a relative range of percentage of battery life used/remaining.  

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Having read this board's input on batteries over the years, I know many of you would have had great input in this campfire conversation:)! What say you here? We're we as the campfire brain collective, going down the rabbit hole on this trend of thinking?

TIA for thoughts, and best to all,

Smitty

Be safe, have fun,

Smitty

04 CC Allure "RooII" - Our "E" ride for life!

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I think it is good "campfire conversation". 

For facts, I prefer to look at Trojan DOD to life cycle chart for a good estimation of the life of the battery.  I always notice that for 25% discharge, there is a really large number of cycles.  At 50% discharge about half of the 25% number and it really drops off for the 75%-80% discharge. 

 

Al & Sharon
2006 Winnebago Journey 36G 
2020 Chevy Colorado Toad
San Antonio, TX

http://downtheroadaroundthebend.blogspot.com/

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