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Old 23-06-2018, 12:22   #211
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Re: What count as a cycle (battery life)

Getting back a bit closer to the thread topic perhaps, I had an interesting experience with my near-new 510ah bank of Lifelines last week.

I was at the dock with batteries topped off and the Victron BMS reset, and decided to turn the charger off for much of the week to see what some of my individual appliance & cumulative loads might be. My frig/freezer runs off 110v, and with gps & instruments mostly off it was primarily lights, shower drain, heads, bilge pump, CO detectors drawing on the batts.

With no lights on but CO detectors running, along with heads, bilge pumps, shower drains turned "on" but not running, the typical draw was about 0.46 amps. The cumulative draw over the approx. 4 days, according to the BMS, was a little over 100 amps. So with a newly minted 510ah bank, I should have theoretically used approx. 20% of its capacity.

But the BMS showed no lower than 87% SOC. What's also odd (I thought), was when I turned the charger back on it stayed in float, delivering no more than 20 or so amps back into the batts at any given time at 13.3v. This was based on the remote monitor for my Xantrex 50A charger, and not metered from the batts. themselves.

Does this sound about right, or should I suspect something may be wrong with my (8 year-old) batt. charger? And what explains the 87% SOC reading with 100 amps drawn from a near-new, 510ah battery bank?
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Old 23-06-2018, 12:37   #212
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Re: What count as a cycle (battery life)

read up on Peukert:


discharge at the 20h rate, capacity = rated capacity
discharge at higher rate = less than rated capacity
discharge at lower rate (as you did) = battery has higher capacity.


plus, your peukert factor is probably wrong, the BMV700 uses 1.25 by default, for lifeline it should be 1.12
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Old 23-06-2018, 13:22   #213
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Re: What count as a cycle (battery life)

Quote:
Originally Posted by LeaseOnLife View Post
read up on Peukert:


discharge at the 20h rate, capacity = rated capacity
discharge at higher rate = less than rated capacity
discharge at lower rate (as you did) = battery has higher capacity.


plus, your peukert factor is probably wrong, the BMV700 uses 1.25 by default, for lifeline it should be 1.12
Thought it might have something to do with that (Peukert), but I'm obviously not well-schooled. Also probably explains why when I turn off an appliance the voltage will often go up.

Also didn't realize you could change this setting on the monitor. Could help explain why the total-time-to-discharge reading was wacky.

I would think that being down to 87% would be enough to trigger bulk mode on the charger, but maybe not.
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Old 23-06-2018, 13:41   #214
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Re: What count as a cycle (battery life)

That Link unit was never very accurate as a SoC meter, and is now very long in the tooth.

But this nay help you tweak it:
https://marinehowto.com/programming-a-battery-monitor/

As far as the charger goes increase the "bulk return" setpoint.

These adjustment should be tuned to your normal usage patterns, or adjust between marina vs cruising cases.

No point in spending time tweaking for an experiment scenario never encountered IRL.
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Old 23-06-2018, 13:45   #215
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Re: What count as a cycle (battery life)

Quote:
Originally Posted by Exile View Post
...
I would think that being down to 87% would be enough to trigger bulk mode on the charger, but maybe not.

I don't think your charger knows about the 87% from the BMV, two totally separate systems. I don't know your charger, but maybe it triggers bulk/absorption (at higher voltages) charging only if batt-voltage was below xx.xV. Your batts probably had >= 12.7 Volts all the time with that little load. But that is just a guess...


on edit: John was quicker :-)
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Old 23-06-2018, 14:14   #216
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Re: What count as a cycle (battery life)

Quote:
Originally Posted by LeaseOnLife View Post
I don't think your charger knows about the 87% from the BMV, two totally separate systems. I don't know your charger, but maybe it triggers bulk/absorption (at higher voltages) charging only if batt-voltage was below xx.xV. Your batts probably had >= 12.7 Volts all the time with that little load. But that is just a guess...


on edit: John was quicker :-)
Yup. Lowest voltage I saw was 12.77. And the charger isn't reading amps coming out, of course, only voltage.

Makes sense. Thanks to you both!
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Old 23-06-2018, 14:27   #217
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Re: What count as a cycle (battery life)

For lithium anytime the battery charges even as little as 1% or 100% counts as a cycle.
Had a phone with a lithium battery and a external battery pack. The external battery pack maintained the phone's battery at 80% full. After three months of my phone at the 79-80% battery range with a weekly drain to less then 30%. The phone's internal battery failed in 3 months.


Lead acid type batteries are different but the big issue with them as they discharge the lead becomes more porious. It's called sponge lead. And repeated deep cycling leads the lead to shed into the bottom of the battery case eventually shorting out a cell. Deep cycle batteries are built with thicker plates so sheding is usually reduced. Leaving a increased life.
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Old 23-06-2018, 15:35   #218
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Re: What count as a cycle (battery life)

This is great!

My brain is both growing and exploding at the same time.
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