Dragonfly battery help.

[Dpm70820]

Have new 2023 Springdale 286BHU. SolarFlex 200 installed. 1. Can anyone explain how I know the battery is charging(charged) on the VictronConnect App? 2. If I were to add a second Dragonfly battery would the MPPT 75-15 be able to handle charging(but slower if I understand correctly.)? Dealer not very knowledgeable in this regard. 3. Could I add a second solar panel of equal value to the MPPT 75-15? thanks in advance.

[mikec557]

Originally Posted by Dpm70820

Have new 2023 Springdale 286BHU. SolarFlex 200 installed. 1. Can anyone explain how I know the battery is charging(charged) on the VictronConnect App? 2. If I were to add a second Dragonfly battery would the MPPT 75-15 be able to handle charging(but slower if I understand correctly.)? Dealer not very knowledgeable in this regard. 3. Could I add a second solar panel of equal value to the MPPT 75-15? thanks in advance.

1) I can't help you with that. It's been too long since I used the app.

2) yes, it will charge it just fine. Remember to hook the batteries up in parallel. It's not that it charges more slowly. They are, presumably, run down further. You added a 2nd battery because you wanted to use more energy. At this point (but see #3), your solar system is not any bigger, so it will take longer for your solar to fill two batteries.

3) probably, with a caveat. The controller can handle up to 15amps, thus the (75-)15. I'm guessing your 200 watt panel has a 9 amp maximum output. So two panels in parallel would be 18 amps max. It is *very* rare to actually get the max output. Think Phoenix at noon and your panels are pointed straight up. But because it *could* happen some folks would say get a bigger solar charge controller.

3.5) but you could wire the two panels in series instead of parallel. Then the volts double and the amps remain the same. Look at the max voltage of your panels, it's probably 19ish volts. So two would be 38 volts, well below your 75 volt ceiling (75-15).

[Dpm70820]

Thanks very much for the great information. Indeed I have only one “factory” 200 watt panel. My brainstorm was a second battery and a portable add-on second solar panel. But weather I can add it when needed and how complicated the connections would be is another story. Parallel would be easier to add on when needed. Series would be more complicated I think. And then would the extra panel feed raw power in or have its own onboard controller….. And as you noted, would I need a larger capacity controller to be on the safe side….. More thinking to do…. Thanks again….

[Cheesehead4Life]

Welcome to the forum DPM.
1) on the main screen in the “Output” section the second line is “current”. A negative number means you’re discharging, positive is charging. That’s the flow to/from battery.
2) not a problem to add another battery. ‘Best practice’ with multiple batteries in parallel is to connect positive to one end of the bank, and negative to other end of the bank. Not both to to same end/battery.
3) No you cannot. That 15a in the model number is the OUTPUT. In nice round nominal numbers, your 200w divided by 12v = 16 amps. (You won’t get 200w, and you will charge at 13 so you’re fine) But more solar=more charge controller in your case. There have been other threads about this upgrade with links to keystone site with good Q&As on this.

[Dpm70820]

Based on your information, sound like adding a second battery would be the simplest approach. I do understand it will take longer to recharge batteries exclusively by Solar but that is not really an issue with me as long as the charger will indeed "top them off" at some point as long as I am not using more energy than the charger is putting back. I think this might work. Don't want to get too complicated right now as this is a new camper for me. Thanks for your insights.

[JRTJH]

Keep in mind that if you're using the solar system while the trailer is in winter storage and relying on it to keep your batteries charged while they are connected to the trailer "phantom drains" (CO detector, radio memory circuits, etc) that any snow, ice or leaves that might cover all or part of the solar panel will affect the ability to obtain any energy. Compounded with the angle of the sun in your area (about the same as Chicago or Detroit) you may find that the batteries won't receive any (or very limited) charge during the winter storage.

So, your plan may work fairly well during the summer camping season, the same plan might have different results during winter conditions.

I wouldn't rely on the solar system in any "snowy winter conditions" without frequent, even daily rooftop checks for snow removal.

[Dpm70820]

Thanks for the reply. Understand the issues with winter storage of Dragonfly batteries. Dealer says shoreline or generator should charge batteries on times of extended no sun/bad weather. Winter storage will be at my home and I am not adverse to removing batteries to my cellar with a quality Lifepo4 maintainer. I usually cover my RV anyway. Time will tell. 2023 Camper came up here (Massachusetts) from Connecticut to local Campers Inn. Trying to confirm battery state if they had it over last winter and make sure it functions as designed. Still a lot to learn. (New Technology). Thanks for the info.

[JRTJH]

DragonFly batteries are designed to be stored in "long term storage" (3-6 months) without the need for any "maintainer charging". They are stable and will retain the charge for that long without recharging. As long as the battery is not connected to anything, the BMS will remain inactive and not use any battery power to "self heat" or operate the BMS.

During the winter, all you need to do is fully charge the batteries, keep them in a "moderate temperature area away from heat or sunlight/UV rays". They lose about 2-3% of their charge per month, so you're looking at somewhere between 2-3 years before they're discharged to a point where they need to be recharged.

Here's the DragonFly storage instructions from their battery manual: https://dragonflyenergy.com/wp-conte...3_09062022.pdf

"How to Properly Store Batteries
We recommend bringing the Dragonfly Energy Battery to a 100% state of charge. Then, disconnect the battery from any loads by removing the negative cable from one battery. On average, the batteries lose approximately 2-3% capacity per month. This is subject to increasing if stored in extreme environmental conditions. "

You'll be good to go with just checking them once during the winter to see what the voltage is on each battery. If it's at or above 13.3 VDC (90% charge) they don't require anything but maybe "dusting them off". A 50% charge is between 13.1 and 13.2 VDC, so anything above that voltage should be "OK with no charging required".

[Cheesehead4Life]

John beat me to the self discharging and pointing out no need for a maintainer.

On your battery monitor, it never really knows how much energy is in your battery. It just calculates how much you’ve used of the known 100 amp hours or whatever capacity your battery is. So after it knows you’ve used 20 amp hours it just calculates that you’re at 80% state of charge, it’s not like a fuel sensor where you drop it in and the float knows how much you have in the tank. For this reason it’s important that you fully charged the battery and take note that it says 100%, so you know it’s calibrated. Because this is a new to you setup, that’s a step you should take to know that it’s properly calibrated to start with. And also, if you do add a second battery, you need to go into the settings to tell it how much battery capacity you now have. And that is because of what I explained above.