Time It Takes To FULLY Charge Batteries

[RickG]

Originally Posted by RickG

On trusting your battery monitor to tell you when your bank is charged, I think my Victron BMV-712 is call 100% SOC too early and auto-syncing to 100%. While this thread has been going on I have been watching my batteries during the day. I am pretty sure that the BMV went from about 80 amps down to 100% this morning. It is an overcast day with occasional showers.

I am looking at the "Charged Detection Time" setting as a possible culprit. It is set to 3 minutes and it represents "the time the charged-parameters (Charged voltage and Tail current) must be met in order to consider the battery fully charged." Charged voltage is set to 13.2V and tail current is set to 3% (812 amp hour bank, 24.3 amps). For my 7 Fireflys the tail current should be 3.5 amps which is 0.004%.

I'll try setting tail current to 0.5% and charged detection time to 10 minutes.

Make sense?

Cheers, RickG

Correction, 3.5 amps 0.4% of capacity.

[barnakiel]

Originally Posted by RickG

(...)



Charged voltage is set to 13.2V



(...)

So ... your batteries are charged already at 13.2V ?


Ours are charged at 14.4 - 14.8.


Why do you think is this?


What technology are your batteries then?


barnakiel

[RickG]

Originally Posted by barnakiel

So ... your batteries are charged already at 13.2V ?


Ours are charged at 14.4 - 14.8.


Why do you think is this?


What technology are your batteries then?


barnakiel

According to the Firefly manual, the Fireflys are 100% charged when the charging current drops to 0.5 amps. I have the BMV-712 battery monitor now set with charged voltage of 13.4V, tail current of 0.5% (4 amps), and charge time of 10 minutes.

The challenge is that with solar the current and voltage can go up and down and the BMV can sync to 100% SOC early. I am trying to get the the SOC to be more accurate and not sync early. I'll see how the above settings work. The next step is the approach discussed in the BMV manual:

"The BMV synchronises too early
In solar systems or other applications with fluctuating charge currents, the following measures can be taken to reduce the probability for the BMV to reset prematurely to 100% state of charge:
a) Increase the “charged” voltage to only slightly below the absorption charge voltage (for example: 14.2V in case of 14.4V absorption voltage).
b) Increase the “charged” detection time and/or decrease the tail current to prevent an early reset due to to passing clouds."

Cheers, RickG

[sailorboy1]

Originally Posted by RickG

According to the Firefly manual, the Fireflys are 100% charged when the charging current drops to 0.5 amps. I have the BMV-712 battery monitor now set with charged voltage of 13.4V, tail current of 0.5% (4 amps), and charge time of 10 minutes.

I feel the voltage should be 14.4V with the rest the same.

[RickG]

I'm going to change charged voltage to 14.2V as the next change, once the current changes bake for a couple of days.

I did up the over voltage alarm to 14.6V because the BMV was alarming too often at 14.4V with very small over voltages. The Admiral was convinced I was cooking the batteries. She pretty much never wants to talk about batteries after I talked to her everyday about the subject when I was doing or electrical refit.

Cheers, RickG

[barnakiel]

" ... For a complete charge cycle, charge the Oasis to 14.4V with temperature compensation (bulk phase) and continue charging until the charging current drops to 1.5A (absorption phase, time will vary) ..."

http://azimuthsolar.ca/wp-content/up...nual-12-15.pdf

Just check if this is the battery type you have.


Note the meter has nothing to do with the charger (unless you have a combo) so what Voltage is attained and how long it is kept depends on the CHARGER.


And what 100% SOC you set up for your meter depends on how you set up the meter. Not all meters can be tuned with all chargers.



It is always nice to have a charger that can follow the optimum charge curve for our specific batteries, and a meter that will catch the 100% SOC in each cycle (and reset the counters) BUT ... it is not always that we can match everything (unless we buy all components to attain things only lobotomized electricians care about). ;-)



barnakiel

[RickG]

Originally Posted by barnakiel

" ... For a complete charge cycle, charge the Oasis to 14.4V with temperature compensation (bulk phase) and continue charging until the charging current drops to 1.5A (absorption phase, time will vary) ..."

http://azimuthsolar.ca/wp-content/up...nual-12-15.pdf

Just check if this is the battery type you have.


Note the meter has nothing to do with the charger (unless you have a combo) so what Voltage is attained and how long it is kept depends on the CHARGER.


And what 100% SOC you set up for your meter depends on how you set up the meter. Not all meters can be tuned with all chargers.



It is always nice to have a charger that can follow the optimum charge curve for our specific batteries, and a meter that will catch the 100% SOC in each cycle (and reset the counters) BUT ... it is not always that we can match everything (unless we buy all components to attain things only lobotomized electricians care about). ;-)



barnakiel

I have Firefly G31s. The 2020 manual suggests charging until current 0.5A per battery - https://oceanplanetenergy.com/wp-con...1-4V-450Ah.pdf. All chargers are networked Victron components. My challenge is getting the battery monitor settings perfected for the Fireflys. I'll report back what works.

Cheers, RickG

[sailorboy1]

Originally Posted by RickG

. My challenge is getting the battery monitor settings perfected for the Fireflys. I'll report back what works.

Cheers, RickG

put it on the FireFly thread

[dalemann]

Originally Posted by AnglaisInHull

Yeah, I had the engine rep try to sell me a new high capacity alternator, because, well, it'll charge faster, right?

With the current (is that a joke?) setup, we'll be down 45 Ah after a night at anchor. I start the engine and the battery monitor shows 45 A charging current. So I'll be good in an hour ... except 15 minutes later the batteries are only taking 25 A.

And a 200 Amp alternator would fix this how?

To get any good benefit from a large alternator you need a smart voltage regulator rather than relying on the primitive regulator that comes with the alternator. I installed a Sterling smart regulator and it solved so many charging problems.

[Trimaran Ken]

Originally Posted by Bill O

My comment/question would be, do you ever get to 100% if you are constantly pulling amps out of you batteries (refrigeration, etc.) while you are charging an AGM or FLA?
Mathematically you could say you are putting in more amps than taking away, but does your battery (AGM/FLA) accept all of that?
We do go into float mode early (low daily usage and large house bank) and holds at 12.8V for a while after the solar input is 0, but you are still constantly drawing from the batteries.

This is physics, not experience or opinion. If you have solar panels and a proper charge controller setup, at some point your charge controller will declare the batteries have taken all the charge they can and will hold the batteries at that point. The power coming from the solar panels will then be used to meet current demand, and NO power will be "pulled" from the battery.


Your charge controller decides when your batteries are 100% charged. If you feel that the charge controller never gets your battery to 100%, then get a new charge controller.

[Adelie]

Originally Posted by dalemann

To get any good benefit from a large alternator you need a smart voltage regulator rather than relying on the primitive regulator that comes with the alternator. I installed a Sterling smart regulator and it solved so many charging problems.

AIH's point was that if he almost never uses enough power overnight to get the batteries down below 80% then the high output alternator isn't going to shave any time off of recharging, the batteries will not be in bulk charging and will already be in absorption which is voltage limited rather than current limited.

[sailorboy1]

This thread has proven that lots of people don't really understand. But they post and comment because they believe they do understand.

[RickG]

I think understanding is a process. We can read RC's posts on marinehowto.com, but most don't have his experience, knowledge, or resources to bench test our components. Living aboard you need to work with what you have, usually in place with a load on it. After 2 1/2 years with our system I am still learning. I learned a bit from this thread. Part of that was just watching the charging all day for a few days and making some tweaks. I'm not done and may never be.

The last few days it's been cloudy and rainy and I've just watch batteries discharge. I usually run the generator if the batteries get down to 12.3V; today may be that day. Why bother with PSOC Fireflys? It's going to be cloudy for 3-5 more days and I'd rather charge the batteries on my schedule.

Cheers, RickG

[Stu Jackson]

Originally Posted by sailorboy1

This thread has proven that lots of people don't really understand. But they post and comment because they believe they do understand.

It was tempting to suggest this, glad you did.

[sailorboy1]

Originally Posted by Stu Jackson

It was tempting to suggest this, glad you did.

Yes, it is pretty unusual for me to be willing to stick my neck out