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SOC / DOD


Jaco De Jongh

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1 hour ago, Gerald_db said:

Maybe twice a year.

Interesting.

This is NOT advice nor a suggestion on what anyone should do. Just sharing my information.

Equalizing is supposed to be linked to how the batteries are used daily. To this effect, in cycling batteries daily up to 20% DOD / 80% SOC,  I was told:  Equalize voltage of 32V once a month is also perfect and remember you equalize for 1-2 hrs max.

 

The response below was on a question I raised on why the Trojan docs differ. I used 2 examples of slightly different voltages obtained from the Trojan website. I was told:
Remember charging voltages for Absorption, Float and Equalize are NOT like a pin point value. There are accepted range of values in Absorption, Float and Equalize.
From your 2 examples
(see below), they are actually all perfect because your differences are 29.4 & 29.6 which is a 0.2V difference and you have 30.96 & 31.00 is 0.4V difference.

These differences above are negligible. Sometimes you can even have a 0.8V difference and that will be still fine, especially in Absorption & Equalize.
The differences could be because of voltage drops in connections and even the cables and that is normal.


Example one:
Absorption: 2.35-2.45 = 28.2-29.4v
Float Charge: 2.20 = 26.4v
Equalize Volts: 2.58 = 30.96v

Example two:
Absorption: 29.6v
Float Charge: 26.4v
Equalize Volts: 31.0v

 

EDIT: And Gerald's doc says:
Absorption: 29.64v
Float Charge: 27v
Equalize Volts: 32.4v

 

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Re DoD and battery lifetime that is such a theoretical projection and assumes perfect cycling to exactly the same dod on a daily basis. Reality is some days I go to 30%, other days only to 10% or even just staying at float because of bad weather. Only time will tell.

Sent from my SM-G920F using Tapatalk


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Charging keeping the temps in mind automatically is a very good thing over 10 years I think if your batts are in a hot room.

 

FWIW - I got 4 x 105ah batts, maintenance fee UPS batteries, for free.

They did not last as expected, as I expected. DOD says 92% but inverter switches off due to volts too low. Now keep mind, this little system is off-grid, no Eskom anywhere, so the load and batts must match. 

So I charged them separately, and in pairs, improvement, but not wow. So I though, my Victron controller is clever.

Manual says: Every morning controller starts a new charge cycle when the sun starts shining. The maximum duration of the absorption period is determined by the battery voltage measured just before the solar charger starts up in the morning. 

So I though, right, temp is taken care of and as above, the absorption also. Lets give the equalization a go, set it to every single day and see where the chips fall.

Few weeks later I run comfortable on good days down to 82% DOD, sometimes as low as 70% in bad weather, inverter runs 24/7 now.

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  • 3 months later...
On 10/13/2016 at 9:55 AM, The Terrible Triplett said:

Here is the latest T105RE doc I have. 

Absorption charge: 2.35-2.45 = 7.05-7.35v per batt: 48v = 56.4-58.8v
Float charge: 2.20 = 6.6v per batt: 48v = 52.8v
Equalize charge: 2.58 x 3 = 7.74v per batt: 48v = 61.92v

If you have temperature compensation even better: Subtract 0.005 volt per cell (VPC) for every 1°C above 25°C or add 0.005 volt per cell for every 1°C below 25°C.

T105RE_TrojanRE_Data_Sheets.pdf

I am now confused again. Just as i think i get the hang of things...

 

What should i float my T105 RE's at? 54V or 52.8V?

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@Jaco de Jongh its seems we have the same type of batteries and AH capacity and therefore the same technical problems. I use a Raspberry Pi3 with Manie's ICC-Pi program to control the inverters (cluster of 2 in parallel) as well as the Remote Dashboard on both my Ubuntu and Windows 10 PCs to monitor from my office. I installed a BMW 700 and connected it with the overpriced USB cable to the Pi and set switching to grid and solar at low values on the inverters. If I had to buy again I would buy the BMW 702 which has clear advantages. All this works flawlessly except that I am concerned when loads are very high and a high current is drawn from the battery bank. At present I am waiting for HA02 battery balancers from @Chris Rossouw to keep the bank in balance. Just done a post on http://powerforum.co.za/topic/1125-balancing-of-battery-bank/ for balancing 6V Trojans with the HA02 balancers and am hoping there will be some feedback that will help us both.

At present I run on the grid from 17:30 until midnight and this morning my SOC was 74%. The morning was a bit overcast so the solar kicked in a bit late. If a solution to overcoming the high battery load currents materialises in ICC-Pi, I will switch to running the system on SOC instead of time based. My  base load is around 500 to 600W from midnight to early morning. I have 2300W panel capacity and my charge current hovers around 20A during the day. Right now at 18:12 the batteries are at 100%. The inverters' charge current is set to 2A. No need to pay Eskom for what the sun can do for free. Hope some of this helps in optimising your installarion.

 

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