Trying to figure out a solar generator

[banterer]

Hello,

I'm a consumer and not a designer (I do have an electrical background but do not know much about solar generators.

I purchased a solar generator from a company that seems to have vanished from the internet and from history apparently because I cannot find even a trace of them.

The unit was called a Powercube 2000 and it uses a Midnight charge contoller, Victronix battery monitor and a Xantrex Freedom X inverter charger.

I bought it with an extra battery and the associated cables to allow me to externally connect this other Li-phosphate battery.

My very basic question is: To attach this external , supplemental battery, is it to be connected in parallel (+ terminal to + terminal and - to -) or + to - of each (which does not make much sense to me but I do not want to do anything wrong).

I initially tried adding the external battery in parallel and nothing blew up but according to the monitors, a large amount of current started flowing from the main battery to the auxiliary battery so I disconnected it.

Thanks in advance for any help you can render. Please let me know if there are other details I need to provide in order for you to be able to answer me.

Sincerely,
Jorge

[ClassicCrazy]

It isn't a good idea to connect two different age batteries in parallel if they are lead acid because of the battery aging process will want different charging setpoints for each battery. Also it is hard to connect two batteries in parallel and get all the resistances of cabling so that they are balanced and will not favor one battery over another leading to insufficient charging and early battery failure.

But I see you mentioned lithium  - so is the original battery lithium and the second new battery you said is lithium ?  Depending on that they are the same chemistries it might be able to put them in parallel if they have the same charging setpoints  . You would still want to have the cables be as balanced as possible .

It makes sense that the new battery you put on would start taking a large amount of current since new batteries are usually only charged to 50% capacity. Some types of lithium batteries can have very bad consequences like catch fire when one is so imbalanced compared to the other and that rush of energy happens. Not sure about your type. If it was me I would charge the first original battery full, then disconnect it , and charge the newer battery full. That way they should both be at the same charge level and shouldn't get that big rush of current.

I am assuming that the original battery is the same kind as the new one - if they are different like one is lead acid and the other is lithium you won't be able to combine them since they need different charging setpoints.

Larry

[banterer]

Hi Larry,

Both batteries are Lithium Iron Phosphates. They were purchased at the same time from the same company and the additional battery was charged at 100%. I am using the cables that they supplied. The cables are just two very heavy gauge stranded wires.

Jorge

[ClassicCrazy]

I would still charge each of them separately to ensure that they are the same level and you don't get any surges.
What kind of Midnite controller is in your setup ?
I would be interested to know what setpoints it has programmed into it.
The battery should have a bms in it that are supposed to keep bad things from happening but don't chance it.

Larry

[banterer]

It is the Classic 150 SL.

The "charging" can only be done from the main battery, that has the bulk of the electronics. The auxiliary battery only has the battery monitor and no input for the solar panels. I will attach some photos.

[ClassicCrazy]

If the second battery is parallel to the first it will also be charging from the Classic.
But if there is something else between the first and second battery that regulates the charge - who knows.
I would be opening that up and seeing how it is wired.
Does that case have ventilation holes or a fan to cool it ?
Larry

[banterer]

Has a fan. See  attached photo. It is meant to be charged from Classic since that other unit has not other terminals or jacks other than the two 12v posts.

[ClassicCrazy]

Is that the only breaker on the whole unit - that push button 20 amp reset ?
If I had that and wasn't planning on using it as a portable unit, I would open it up , take out all the components, and mount them on a piece of plywood attached to the wall.
That way you could check all the wiring and add appropriate breakers if needed.
I wonder if there is a shunt in that system ?
I don't know the Classic SL model very well  - I think it doesn't have network interface but there is a post on forums here where someone used an esp32 interface that Graham designed that plugged into the  serial port ( below mngp port) and that gave it capability to get all the data out to monitoring apps or mqtt.
You may also be able to add Whizbang to that to get better monitoring and control capabilities for the AUX ports on it.
Just some ideas if you want to get the most out of the Classic.
Larry

[banterer]

There is another reset on the AC input side. On the third side there are 2 cigarette lighter jacks and the 12 v terminals for connecting the aux battery.