Float voltage for Firefly batteries

[N4585K]

Wild Cherry, I’m actually having a Victron bmv installed in Lefkada this Friday. CYS is doing the work. They have also been very good at sourcing different alternators for me. Recommended!

[john61ct]

Originally Posted by Wild Cherry

Interesting dilemma I'm faced with re lengthy charging times and cost benefit ratios brought up by my many learned friends on this forum. A 100amp Mastervolt charger costs around 1600 euros and an 80 amp charger around 1200 euros. Should I not rather spend that cash on solar panels? The thought of several hours of generator noise every other day is not appealing.

That is expensive, but it is not either-or.

Even if you have plenty of solar, there are times you need a mains charger anyway.

With the genny, when solar aline is not enough, best combo is genny in the AM to pump Bulk amps in until you get to 80-90%, depends on predicted conditions.

Finish that before the solar morning, so that has all day to get the bank through the ling tail to 100% Full.

Doing this, you can start with just a few panels, see how you go, then add more later to reduce genny runtime.

A good alternator setup off propulsion engine can substitute for genny too.

[john61ct]

Get pricing on Magnum & Sterling.

Can order online, drop ship to the marina.

[a64pilot]

You don’t have to and I wouldn’t toss the 40 amp charger, keep it.
However do install another charger hopefully larger one. You can buy a 60 and added to the 40 that’s 100, as opposed to having just the 100.
Multiple chargers play well together and give you redundancy.

[a64pilot]

Originally Posted by Wild Cherry

Interesting dilemma I'm faced with re lengthy charging times and cost benefit ratios brought up by my many learned friends on this forum. A 100amp Mastervolt charger costs around 1600 euros and an 80 amp charger around 1200 euros. Should I not rather spend that cash on solar panels? The thought of several hours of generator noise every other day is not appealing.

I think if you don’t mind having panels and can install them etc, that you’ll be happy with panels, cause they just work, every day, day after day they work without you having to remember to do anything and they of course make no noise etc.
Ideal situation is of course a big mains Charger, Solar and a big alternator with a good external regulator.
If I had to prioritize, I’d put Solar first, big mains second and alternator third. But your usage may be completely different than mine, you may crank the motor and travel under power almost everyday, if you do then the alternator becomes very important, or you may live where there is very little Sun.

[Wild Cherry]

Now we talking John! My thinking exactly - solar panels are made for summertime in the Med and an easy installation (flexible on the Bimini top). Another charger in tandem with my existing charger and together not much more than the Mastervolt 100amp charger. I like the idea of a bigger alternator as well. They should charge money for Cruisers Forum !

[FlyingScot]

I just installed 4 LG Neon 360w 36v panels and 4 Victron Smart 100/30. One panel per controller. I have low 2.1-2.3% voltage drop calculated. Hard to measure. I also installed 3 Firefly L15+ 4v 450ah batteries in series for 12v 450ah. I use 80-120 ah overnight.

Batteries charge so fast, I was playing with a 1500 watt heat gun just to give the panels something to do today.

But my question: Firefly user manual says to have the set point of 12v for 1 min to reenter bulk phase. My Victron controller with latest hardware and using phone app for configuration has one place that is this 'trigger' to reenter bulk phase and it's the float voltage setting. Therefore I would have to set my float at 12v to meet this requirement. But, this could cause other issues, like using power from the house bank while the sun shines.

I also found that I had to adjust my absorption voltage to 14.2 vs 14.4, otherwise when they were filling up the voltage overshoots into the 14.5-6 range. I don't need them to charge faster thus I don't need the higher voltage. And I want to maximize life of the house bank.

I do have a newly installed BMV-712 and it shares battery temp (from sensor) to the controllers and voltage. Why it doesn't share amps so we could use tailing current, I'll never know.

Also, any thoughts to leaving the boat with this much solar? Disable some of it? Turn the max amps way down? Turn the float to 12v and let the pack cycle?

Your thoughts are appreciated. I'm heading back to the USA in the morning. Nothing like waiting to the last minute...

[RickG]

We have Firefly G31s and two Panasonic 330 watt panels into dedicated Victron 100/30 solar controllers. We leave the panels engaged when we travel and return to the batteries about 26 amp hours below full charge per the BMV; The Victrons go to float early for our system, but the Fireflys' PSOC perfomance makes us unconcerned. Given the size of your bank and your panels, you could easily turn off two of the solar controllers and still come back to full banks.

Some assumptions - refrigerator/freezer are left on, anchor light, no shore power.

Cheers, RickG

[john61ct]

Originally Posted by FlyingScot

I also found that I had to adjust my absorption voltage to 14.2 vs 14.4, otherwise when they were filling up the voltage overshoots into the 14.5-6 range. I don't need them to charge faster thus I don't need the higher voltage. And I want to maximize life of the house bank.

good call. I'd want to nail this down with support at some point, should not be this way. Is V at batt post same as measured by the controller?

> I do have a newly installed BMV-712 and it shares battery temp (from sensor) to the controllers and voltage. Why it doesn't share amps so we could use tailing current, I'll never know.

I believe Color Control GX does that.

> Also, any thoughts to leaving the boat with this much solar? Disable some of it? Turn the max amps way down? Turn the float to 12v and let the pack cycle?

Shore power?

Have you got significant loads?

Some just set all voltages while stored to =Float 13.2V. Why are you using 12V?

For long term storage IMO ideal is bank completely isolated, reliable human reconnects to top up for a cycle every few weeks.

[RickG]

Originally Posted by john61ct

]

Some just set all voltages while stored to =Float 13.2V. Why are you using 12V?

Good call and easy to do via the Bluetooth app. At least the batteries will cycle a bit overnight.

Updated battery manual at link below. No need to charge during storage for up to two years. This version of the manual bumps the float voltage to 13.4V per the manufacturer's recommendation. But, the designer and the manufacturer prefer not to float at all.

https://www.bruceschwab.com/wp-conte...L15-181019.pdf

Cheers, RickG

[FlyingScot]

Originally Posted by john61ct

good call. I'd want to nail this down with support at some point, should not be this way. Is V at batt post same as measured by the controller?

> I do have a newly installed BMV-712 and it shares battery temp (from sensor) to the controllers and voltage. Why it doesn't share amps so we could use tailing current, I'll never know.

I believe Color Control GX does that.

> Also, any thoughts to leaving the boat with this much solar? Disable some of it? Turn the max amps way down? Turn the float to 12v and let the pack cycle?

Shore power?

Have you got significant loads?

Some just set all voltages while stored to =Float 13.2V. Why are you using 12V?

For long term storage IMO ideal is bank completely isolated, reliable human reconnects to top up for a cycle every few weeks.

The controllers are setup to get temperature from the BMV-712. I compared the 712 readings with the individual controllers by using two iPhones simultaneously and they were always within +/- 0.02v so I believe that the sharing function is working properly. I also compared the readings against a Fluke 365 true RMS meter. Weirdly the Fluke, despite it's price and quality, only reads down to .1 volt. It's more of a clamp on meter with removable jaw. As best as I could estimate there is a 0.05v difference between the actual measured voltage and the BMV & MPPT voltages. The BMV shunt sits only a couple of feet from the batteries and the batteries have brand new Ancor 4/0 cables and Ancor lugs.

I didn't realize the Color Control could do so much. My initial look saw the price and assumed it was a fancy color display. After further research I may buy one, but I still don't think it will report current from the charging to determine when to stop charging. The docs I read said it would report the sum of all the MPPT's to the BMV to improve SOC accuracy.

I hope to never plug into shore power again. Definitely not in Curacao where 110 VAC is available but only at 50HZ. Nothing worked well on my boat when I did this.

I have a combo unit inverter charger (Xantrex RV2012GS with remote panel). I may eventually replace this since it is modified sine wave. The Xantrex remote panel (RC/GS RC7) can display both inverter/charger amps and total average amps flowing through it. Combined with the BMV-712 it is easy math to see where the power is going.
Example: BMV show +40 amps, Xantrex shows average amps -10 and inverter amps at -3. This tells me that solar is providing approximately 50 amps at that moment. 3 amps going to the boat AC outlets, another 7 amps going to other loads (refrigeration and radio are common for me) and 40 amps going into the batteries. When I look at individual panel output they add up to just a little over the 50 amps.

I do have a newer 1000 watt pure sine wave inverter installed in my cabin for important charging items.

I left the boat with all the loads shut off this time. In the future I plan to leave the refrigerator running.

I disabled two panels by pulling the fuse. My fear is to have a water ingress and not have enough power for the bilge pumps to handle. Two panels current limited to 10 amps was my idea of a solution.

I'm not using the 12v setting other than for a short while to test what happens. What happened was the sun was shining and after the batteries went to float they started draining. Thus my confusion and question about the trigger voltage to restart bulk charging.

[john61ct]

Originally Posted by RickG

Good call and easy to do via the Bluetooth app. At least the batteries will cycle a bit overnight.

Updated battery manual at link below. No need to charge during storage for up to two years. This version of the manual bumps the float voltage to 13.4V per the manufacturer's recommendation. But, the designer and the manufacturer prefer not to float at all.

https://www.bruceschwab.com/wp-conte...L15-181019.pdf

Cheers, RickG

13.2V is "still better". 13.4V is an acceptable "up to" in order to accommodate some buyers' non-adjustable existing hardware (marketing simplification).

No Float is optimal as with LFP.

[FlyingScot]

Originally Posted by john61ct

13.2V is "still better". 13.4V is an acceptable "up to" in order to accommodate some buyers' non-adjustable existing hardware (marketing simplification).

No Float is optimal as with LFP.

I currently have float set at 13.1v. I was trying to have it just high enough to use the sunshine without 'charging' the batteries. I don't know the true resting full voltage of the batteries but under a 7-10 amp load this seemed to be the 'full' point when the amps into the batteries were below the 6 amp threshold for tail current specified by the documentation from the mfg.

If there is another solution to not float the batteries without draining them, I'd like to do that. But what I don't want is to charge the batteries by noon and then drain them and possible start charging them again during the same day. This would also have the risk of less available AH overnight and end up with a higher DOD by morning.

I have not seen a voltage / SOC table for resting or under 10 or 20 hour load. If anyone has one, I'd love to see it.

[john61ct]

Originally Posted by FlyingScot

the trigger voltage to restart bulk charging.

That is still I believe an algorithmic "black box".

Definitely not just a simple voltage trigger

Noelec did some deep study and concluded Victron re-starts Bulk/Absorb cycles at a more frequent / shallower point than most vendors.

Which is a good thing, given their AHT algorithm is better than a dumb eggtimer approach as well.

I believe in trusting our computer overlords, long as AHT is getting the bank to Full at least most days when enough energy vs usage is there.

But I would do the FF "capacity restore" procedure on a precise manually controlled power supply, which may require (be easiest with) shore power present.

[john61ct]

Originally Posted by FlyingScot

I have not seen a voltage / SOC table for resting or under 10 or 20 hour load.

That to me is like asking for a sledge hammer when standing in a fully stocked Swiss CNC-capable machine shop.

Easy to make your own using tailing amps to reset the BMV then counting AH down at a standard rate (.05C / 20-hr? up to you) in 10% DoD increments, resting isolated a standard time period before reading each V.

And then do a new one each year using the same settings, since the SoC vs Voltage will change