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joe19 avatar image
joe19 asked

Constant voltage drop loop

  1. Hi,

I have gone through the posts, but were unsuccessful in finding an answer. If I missed something, please direct me.

My victron system charges the 400A freedomwon lithium upto 14v/100%. As soon as it reaches 100%, the voltage drops to about 13.4v/99%, and the process repeats itself.

The orion b2b however, charges the battery to 14.2v and keeps the voltage constant-no voltage drop.

Freedomwon has checked on their side, and can find nothing wrong. Any ideas?

The system is on a sailboat. We have three methods of charging: shore power, solar and the b2b connected between starter battery and lithium.

How can I get the system at a constant 14.2v without the endless loop of discharging and charging?

Any help would be greatly appreciated.

Thanx in advance.

battery system voltage
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2 Answers
delf67 avatar image
delf67 answered ·

Why do you think your system needs to be at 14.2V? A fully charged battery will read 13.2-13.4V (it's nominal voltage). You are seeing a higher voltage with the b2b because it is constantly applying a charging voltage to the battery. For lead-acid batteries a constant trickle charge was needed to keep the battery topped up. As far as I know you don't need to do this with lithium. As soon as they are fully charged the charging voltage is removed and the battery settles back to it charged voltage. I would say the charging profile on the b2b is treating your battery like a lead-acid one, not lithium. Are you sure your system is configured correctly for the type of battery you are using?

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joe19 avatar image joe19 commented ·

Thanx. I'll double check the b2b settings. The real issue for me is the fact that the battery is discharging (although there is a constant power supply) to 13.4v and charges back up to 14v/100%. As soon as 100% is reached it discharges again to 13.4v. And this repeats constantly.

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delf67 avatar image delf67 joe19 commented ·

When the voltage reduces to 13.4 it is not "discharging" as such, it is the battery voltage settling back to nominal voltage because the charging voltage has been removed.

I take it you do not have the batteries BMS communicating with the Victron equipment?

So no Cerbo GX etc?

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joe19 avatar image joe19 delf67 commented ·

Thanx for the feedback. When the system was first commissioned, the system charged to and stayed on 14v. Unfortunately I can't remember when it started with the "discharge/charge cycle" .

The bms is connected to the victron system with a cerbo gx that links to a colour controller

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delf67 avatar image delf67 joe19 commented ·

My system is 48V, lithium batteries, BMS, Cerbo etc. It will charge @56V (equivalent to your 14V) until 100% SOC then the current drops to zero and the voltage will slowly drop back to nominal. Everything I've read seems to say that lithium don't need the "float" charge that lead acid do. Maybe I'm wrong

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joe19 avatar image joe19 delf67 commented ·
Appreciate the info. Thank you
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delf67 avatar image delf67 joe19 commented ·

batt_volts_amps.jpg

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batt-volts-amps.jpg (41.5 KiB)
Albert de Jongh avatar image
Albert de Jongh answered ·

What victron product are you using to charge the battery with?

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joe19 avatar image joe19 commented ·
4 x 100/30 mppt's

1 x orion smart b2b 30amp

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