Multiplus II 2x120 - I have a couple of questions

Gould

Solar Enthusiast
Good morning ,

My solar install is dangerously close to complete. It’s been operational on the 12v side of the RV for a few weeks now and running great. While working away in the garage last night the last piece of the puzzle finally arrived 2 months after ordering.

Of all the complexities within this system and the ridiculous amount of research, I have a couple of what seems like pretty simple operational questions I’m hoping folks can help answer.

1.) I have a 150/100 SCC and the multiplus both with the potential of charging the batteries. I suspect that I use the same charge profile settings for both chargers?

2.) If both the solar charger and multiplus are operating i.e. the sun is at high noon and I’m plugged into shore power, do they compete or just magically figure things out?

3.) I’ve read somewhere that a resistor should be placed inline if the positive from the inverter to the battery the first time the battery is connected to avoid arcing. Is there a size of resistor that’s recommended?

4.) And lastly, I can’t seem to find a way to energize the multiplus enough to connect to it and configure it, without it actively powering the rig or charging the batteries. The inverter power button has a position I and II, could that be it?

Many thanks!
 

Gould

Solar Enthusiast
I’ll update with what I find if anyone else is interested. Regarding number 3, I found a video where Will describes the capacitor pre-charge process. He uses a 30W 25ohm resistor.

 

TAS CPA

Solar Enthusiast
4.) And lastly, I can’t seem to find a way to energize the multiplus enough to connect to it and configure it, without it actively powering the rig or charging the batteries.

Many thanks!
Someone here had a post where they had wired in an extension cord to power the unit while on the bench. Basically just cutting the female end off and stripping some wire. Try searching for that and asking them more specifics.
 

Gould

Solar Enthusiast
Just had a good chat with my reseller, very knowledgeable! (not sure if there are forum rules against mentioning them by name).

1.) Correct, both devices should receive the same charge settings based on the data-sheet from the battery OEM

2.) This is no issue - these devices all monitor the battery voltage and adjust their charge parameters accordingly. So if the solar is putting a full charge on the batteries and you happen to move to shore power, the inverter and controller will adjust their outputs accordingly based on that battery voltage they see at the device.

3.) I have seen the same guidance and Utube videos that show the use of a resister to enable the unit to be powered up and to not fault out some BMS’s on the LFP batteries. I personally have not seen this issue occur in units we have sold. If you are nervous about it, you can also use a car battery (if it is a 12v Multiplus) to precharge the capacitors). It will enable the large current inflow without a fault typically

4.) The Multiplus will power up when connected to the battery bank. The charger only operates when AC is applied to the unit. To keep the unit from charging with the wrong profile, just keep the AC off. This is not a big deal regardless, a few minutes (or even hours) of AGM charging profile will not hurt your BMS/Battery. “Most lead-acid battery chargers will do the job just fine. AGM and GEL charge profiles typically fall within the voltage limits of lithium iron phosphate battery. Wet lead-acid battery chargers tend to have a higher voltage limit which may cause the battery management system (BMS) to go into protection mode. This won’t harm the battery; however, it may cause fault codes on the charger display.”

Hope this helps others!
 

SacRV

Solar Enthusiast
Even though I have the same inverter I didn't know the answers to your questions. But I do enjoy learning more through your install. Thanks!
 

Gould

Solar Enthusiast
I’ve learned these are very capable but comprehensive units so like you, any sources of on hands experience are more than welcome!

One major annoyance is the fact that a $2000 device doesn’t have Bluetooth, or the ability to change the default settings without an additional dongle. It comes pre-configured for use with an AGM battery. The only way to change it is going into the professional installer settings via the dongle. I get they don’t want DIY’ers blowing anything up so put the battery config in the standard menu.
 
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