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kernowsolar avatar image
kernowsolar asked

Mppt. DC to DC Charger . AGM battery settings

Hello . I have a Victron 110AH Battery , with a Victron 100/30 MPPT, and a Victron DC to DC charger (18amp).


I want to make sure , I have selected the correct charger settings for my battery , on the MPPT, and the DC to DC charger .


My Battery Says it had a :

Standby : 13.5 - 13.8 v

Cycle : 14.4 - 14.7v


On my MPPT I have chosen the AGM Spiral Cell setting

Absorption 14.7v

Float 13.8v

Equalisation Voltage 16.5 ( Manual - Disabled)


On my DC to DC Charger, I chose AGM Spiral Cell

Absorption 14.7V

Float 13.8V

Please could you let me know if these are the correct settings. I think they are , but I spent a lot of money on my battery and want to make sure i am charging it correctly .


Thank you for your help


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2 Answers
marcve avatar image
marcve answered ·

@kernowsolar. Settings look good, except the equalization voltage. Don't know if this is correct, but usually for agm this is between15.5 and 16,3 volts, and should be 8 hours long. But, you have it set to manual, so you can still set the correct value if needed.

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kernowsolar avatar image kernowsolar commented ·
Hi Marcve, thank you for your help . I will do some more research on the equalisation option and update . Thank you
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klim8skeptic avatar image
klim8skeptic answered ·

@Kernowsolar please disregard @MarcvE advice before you boil your batteries dry.

Your battery manufacturer recommends 14.4-14.7v for bulk / absorption for cyclic use.

And 13.5-13.8v for standby use.

Given your batteries wont be used as a standby battery (it gets charged by the solar / dc2dc, and does not get held at the standby voltage 24/7, but rather discharged between charges) use a combination of the cyclic and standby voltages.

14.4v would be ok as an absorption voltage (with adaptive absorption).

13.8v for the float is ok as the chargers are not connected 24/7.

Given that you have a Victron AGM it is safe to use the standard "Position 2" preset, for Victron batteries.

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kernowsolar avatar image kernowsolar commented ·
Thank you Klim, I will look at changing the settings tomorrow, or at least using the position 2 preset . Thank you for explaining the standby voltages. It makes a lot more sense now :)
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marcve avatar image marcve commented ·
The sun does not do what you want. So you cannot simply state the battery is not used as a standby battery. The user does not !. To many variables involved. So please, don't say to disregard my input. I won't do to yours. It is all about helping out with the knowledge we have. And don't state the user is going to boil his batteries, I never did.
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klim8skeptic avatar image klim8skeptic ♦ marcve commented ·

@MarcvE normally you wouldn't equalize AGM or Gel batteries, unless the battery manufacturer recommends it.


Even then you have to be really careful as to what the manufacturer intends equalization to actually mean. Equalization = Absorption for some manufacturers.


As to whether the battery should be charged to 14.4 or 14.7v, choose the safer 14.4v option with a good quality "intelligent" charger that can adjust the time the battery spends at the absorption voltage. Maybe for a fast charge, or a dumb charger then 14.7v would be appropriate.

Remember you want to minimize the amount of off-gassing (AKA boiling) that happens during charging, as gas lost = water lost from the sealed battery (AKA dry). Charging batteries at higher voltages increases the amount of water lost, leading to shorter battery life.


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