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alemanza avatar image
alemanza asked

BlueSolar 75/15 tail current

Hi everybody, could someone confirm the value of tail current to 0,1% of floaded lead acid battery bank capacity A/h ? After long reserch on this blog and others, i find this value, i drop the 1 amp tail current setting to 0.3 amp (0,1% of my 300 A/h bank) and finally i see a good increase of SOC without any heat or gas, with absorbing time into the parameter limit and a good increase in capacity that i didn't had before. Just to know if the value can be correct. Thanks.

BMV Battery Monitor
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2 Answers
Mark avatar image
Mark answered ·

The recommended tail current varies depending on the exact type of battery and make, but its normally in the range of 1.0% to 2.0% of battery bank capacity (not 0.1%, that's too low and likely can't ever be achieved).

So for a 100Ah battery, about 1A to 2A.

PS. Some manufacturers recommended less than 1% for AGM type batteries.

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alemanza avatar image
alemanza answered ·

Thanks Mark, my battery bank is 2 x 150Ah normal truck starter battery, setting 14.5v bulk and absorbtion, but with tail current set to 1A the absorbtion time was too short and i realize a SOC of only 80%, working with load alweys between 80 to 50%, once set the tail value to 0.3A , the absorbtion time take longher (how have to be to top up the last 20% SOC) but still into the paramiter of absorbtion time by the charge controller algoritm, and finally i see my battery cherged....so for my point of wiew is correct...could be because i am in Malaysia where folk say the battery factory fill with low % of acid mix due to the temperature range at 30 degree celsius average? Thanks for your time.

2 comments
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Mark avatar image Mark ♦♦ commented ·

If you are using a battery monitor to track SOC% you should be setting it to synchronise to 100% SOC when the tail current is slightly above the MPPT tail current.

Tail current at the absorption voltage is the best indicator that the battery is at 100% SOC.

Judging by your comments, I think your battery monitor might be getting out of sync and/or your batteries may be on their way out.

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alemanza avatar image alemanza Mark ♦♦ commented ·

Because i don't trust in battery monitor and i am still studying the Phukert law, i use the old hydrometer sistem, take it 1 hour after charge end, and at morning before charge start all compensated by temperature, battery bank 1 year old...and with 1A tail current set, i never see 100% (80% max), now with tail set to 0.3A after 3 days i start to see 95%....

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