# Maximum 12v DC system Voltage

Discussion in 'Tech/Mech General' started by sallylillian, Aug 10, 2015.

1. ### sallylillianFunsterLife Member

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I have a new Flair which has 3 off 165 amp hour Varta professional AGM's. They should be Victron but that is another story. The inverter charger is a Victron Multiplus. Varta have published charging characteristics for these batteries of 14.8 absorption, and 13.8 float. (temperature compensated) both of which seem high to me. I have interrogated the Victron and the factory have set the absorption at 14.4. I have emailed Varta for confirmation on the correct voltage. But it led me to worry about such a high absorption voltage, as obviously when the batteries are colder the temperature compensation will take this to over 15 volts and my concern is other equipment using 12 volts and getting 15+. My CBE central panel for example?
Am I concerned unnecessarily?

2. ### Wildman

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yes

3. ### sallylillianFunsterLife Member

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thanks!

4. ### SomeoneElseFunster

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Varta issue leisure battery operating instructions

It contains the following:

Recommendation:
a) Standard charging: charging current with IU charge profile for AGM: I = 25% of the
nominal capacity, max. voltage = 14.8 V; for wet-cell batteries: I = 10% of the nominal
capacity, max. voltage = 14.4 V; for golf carts: I = 10–15% of the nominal capacity,
max. voltage = 2.47 V per cell.
b) Trickle charging: restriction of partial charging voltage to 2.3 V (AGM), 2.23 V
(wet-cell batteries) and 2.20 V (golf carts). Alternatively, use a charger with IUoU charge
profile that charges with I = 10% of the nominal capacity.
c) Charging to avoid acid stratification (not necessary for AGM): use a charger with
IU charge profile with higher charging voltage (2.6 V per cell). This “overcharging” should
only be conducted for a short time as prolonged use could encourage water loss.
- After charging, the recharge value should stand between 2.12 and 2.13 V.

5. ### Don QuixoteFunster

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Whoosh.......................................................................... No wonder most men do not read the manual/instructions.

Last edited: Aug 10, 2015
6. ### Lenny HBFunster

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Where Gel & Wet batteries will reach a full charge at 14.3 volts, AGM need 14.8 for a full charge.

7. ### sallylillianFunsterLife Member

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Which is what I posted without the verbosity!

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8. ### Don QuixoteFunster

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Wonder how many members are looking that word up right now............

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9. ### TechnoFunsterLife Member

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Me

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10. ### sallylillianFunsterLife Member

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noun: verbosity
1. the fact or quality of using more words than needed; wordiness.

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11. ### TechnoFunsterLife Member

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noun
1. the fact or quality of using more words than needed; wordiness.

12. ### TechnoFunsterLife Member

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Snap!

13. ### JJFunster

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When you switch on a switch, does the item it connects to work?

Yes.

No.

Get the dealer to fix it.

Worry = a human's most useless emotion.

JJ

14. ### TechnoFunsterLife Member

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A man of few words is there a word for that?

EDIT CONCISE

15. ### sallylillianFunsterLife Member

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Excellent to have all this underwritten insurance!

16. ### JeanLucFunster

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Leaving aside debates about verbosity versus pithiness, I think it would be worth asking Varta what time they recommend for the absorption phase, as well as noting the maximum voltage of 14.8v. In their promotional literature Varta state, as one of the benefits of AGM technology, that the batteries charge in far less time than conventional flooded or gel batteries (gels are notoriously slow to charge).
I have no knowledge of the Victron system but I know that in the case of Schaudt chargers, the main difference between gel and lead-acid programmes is the time taken for the absorption stage (there is no AGM programme - at least not on the earlier Schaudt chargers). For gel it is around 8 hours; for flooded lead-acid around 1 hour. A Funster posted recently about Varta AGM battery failure and in his case the charger had been set to 'Gel'.
Perhaps the Victron system has a controllable time limit as well as maximum voltage setting?

17. ### sallylillianFunsterLife Member

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Yes it does, using the VE configure program I can connect and make changes to a whole raft of settings, but I have always just modified the charging algorithm to match the battery manufacturers spec. Currently the max absorption time is set at 8 hours, also I have a 1 hour absorption every 7 days for when the system is in hibernation. I have emailed the UK distributor but may well telephone as well. Thanks for the feedback.

18. ### Lenny HBFunster

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Different battery manufacturers give different charging regimes for AGM, some say use Wet cell settings some say Gel, you do need to check with the manufacturer.
Schaudt were supposed to have an AGM charger available in March this year weather it is available and is being fitted by converters yet I don't know.