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DC-DC Charger...Does It Ever Need to Be Disconnected When Stopped?


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#11 Wallowa

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Posted 21 September 2021 - 03:08 PM

Your 4 gage wire and shorter wire run is apparently keeping your voltage at the charger high enough that your charger isn’t cycling, and probably also doesn’t need to do the “”is the engine still running” test every 2 minutes.

 

 

Thanks...never even knew that the "test' occurred if motor  was still running ..assumed this only happened when the motor was shut off....makes sense and appreciate the insight...

 

Phil


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#12 Vic Harder

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Posted 22 September 2021 - 05:57 PM

Another thought.  If you are wanting the LiFePo4 battery to NOT be fully charged at all times (it has been recommended to not store these batteries fully charged) then you may want to disconnect the DCDC charger when your truck is on the trickle charger.


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#13 Wallowa

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Posted 22 September 2021 - 07:32 PM

Vic...good thought...still in process of determining IF the DC/DC will pass current from the Battery Tender to the BB battery with Tundra motor off....your suggestion is a good one...any pointers on desired storage voltage for a BB?  Now sitting at 13.25v.

 

Phil


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#14 Jon R

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Posted 22 September 2021 - 09:27 PM

You should be able to tell from the Victron phone app what the charger is doing.
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#15 Vic Harder

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Posted 22 September 2021 - 10:50 PM

.any pointers on desired storage voltage for a BB?  Now sitting at 13.25v.

 

Phil

I would not use voltage.  As I think rando and I have said before, 50-80% SOC is where you could store it for optimum life span... IF YOU CARE to have the battery last longer than you will on this earth.


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#16 Jon R

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Posted 23 September 2021 - 12:41 AM

For my battery I use 14.2 volts as the maximum charging voltage, and sync the monitor to 100% when it stops charging at that level. Relative to that slightly conservative 100% value, 13.3 volts seems to be about 75-80% charge with the battery resting, so 13.25 is probably just fine for storage if you don’t have a monitor to be more precise.
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#17 Wallowa

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Posted 23 September 2021 - 02:23 AM

For my battery I use 14.2 volts as the maximum charging voltage, and sync the monitor to 100% when it stops charging at that level. Relative to that slightly conservative 100% value, 13.3 volts seems to be about 75-80% charge with the battery resting, so 13.25 is probably just fine for storage if you don’t have a monitor to be more precise.

 

 

I agree, not withstanding the Victron 712 SOC....the voltage also reflects the SOC....I do have a monitor but as has been pointed out the exact SOC is very difficult to pin down; and, the SOC / voltage range is a very tight one....not many volts to dramatically change the SOC...so we guess and hope for the best...in my case 13.25v.


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#18 Wallowa

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Posted 23 September 2021 - 02:25 AM

You should be able to tell from the Victron phone app what the charger is doing.

 

 

yes, I have been monitoring the DC/DC on Bluetooth and the voltage on the BB while on Battery Tender...so far no input showing or voltage increase in BB..


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#19 Wallowa

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Posted 26 September 2021 - 09:09 PM

Went back to check Prowse's UTube on Voltage vs SOC  on BB...what complicates judging the SOC for me is the non-linear and increasingly often abrupt drop in % as the voltage goes down...like from 13.3V to 13.2V it drops 20% [from full] and then 30% more at 13.1V....

 

My Victron 712 shows 13.24-13.25V steady state with no discharge and master switch off and yet it shows "100% SOC"...how is that possible?  

 

I am missing something....

 

14.4V.....100%

13.6V.....100%

13.4V..... 99%

13.3V..... 90%

13.2V..... 70%

13.1V..... 40%

13.0V..... 30%

12.9V..... 20%

12.8V..... 17%

12.5V..... 14%


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