Solar Fan Connections

Hi there! I have a 24 Volt Fan and a 24 Volt panel that are meant to go together. I have 2 12 Volt Batteries hooked together in a series to make 24 Volts. I have a 12/24 volt solar controller. Panel is going into controller. Batteries are going into controller but im not sure if I am wiring the batteries properly for it the controller. For a while it worked and then it fizzled out on me. Big thing is my controller will not show 24 V going through it. Only 13 volts and I am stuck on what I have done wrong!
Any ideas?
Than you!

link to parts' documentation and spec please

you can also make a crude schematic on how you wired it

I'm betting a BMS went into protect and took a pack offline, controller is trying to charge a 12V battery.

Agreed that more info is needed.

An easy test would be breaking down the pack, setting the controller to 12V and trying to charge both batteries completely.

What 42Ohms said --

I would bet you need an active balancer/equalizer to keep the batteries in sync - they drift apart from different internal resistances.

I did some math a while back and it showed when the charging and usage on a series string was constantly the same one battery or the other would go into protect and shutdown. My experiment showed it was about 2 days on the short time or 2 weeks before one went into protect and had to be reactivated.

The lesson here is that it is ALWAYS better to use a battery that is the voltage you are on verse trying to build one with a series string.

Only thing I would add is, is it one of those very cheap solar controllers? Did you wire the fan into said solar controller or directly to the batteries? The $2 solar controllers are a toy and when people use.them 90% of the time they have issues from not being able to output rated loads to blowing up batteries.
Photos of the controller and a drawing of how you wired it would help everyone give you an answer.

Here are pics of my controller. I tinkered with it yesterday and got it to read 24 v.

I’m getting enough voltage but it’s not going to the fan.

Solarequine said:

Here are pics of my controller. I tinkered with it yesterday and got it to read 24 v.

I’m getting enough voltage but it’s not going to the fan. View attachment 223741

Click to expand...

Yep those things are about as much use as a chocolate kettle from my experience, I have a stack to torture test on my workbench after my neighbour nearly killed someone with his. I'd highly recommend not using it.

That is a cheap PWM controller....as long as it is paired with a 24v panel it works with about 70% efficiency... where it gets dangerous is if you put a 37v panel or better on it.

I disagree with Taffy on them being dangerous. If the unit came with the fan it should be fine for the purpose you are using it for. I wouldn't expect it to charge a household battery but for just a fan it should keep up.

For wiring...

Battery1 pos -> battery2 neg with both pwm pos and fan pos -> battery1 neg with pwm neg and fan neg

Make sure the wires used are large enough for the amps pulled by the fan and the wires to the pwm are large enough for the panel Isc value.

Before you connected the batteries did you fully charge each individually? If you haven't take them apart and do that.

Also make sure to set the mode to your battery chemistry... I see in the pictures it is set to b1, are your batteries flooded lead acid? These usually have 3 modes, have to check the manual for sure... seems like b1 is FLA, b2 is AGM, and b3 is lithium...but it varies so check the manual and match it up to your chemistry.

robbob2112 said:

I disagree with Taffy on them being dangerous. If the unit came with the fan it should be fine for the purpose you are using it for. I wouldn't expect it to charge a household battery but for just a fan it should keep up.

Click to expand...

I saw first hand how dangerous they are, well I heard the explosion and saw the aftermath it was running off a 18v panel charging a 12v 45ah Pb that was running a 12v fan here's what happened to the battery.

So, what was the actual cause? Short? Over charge? Ran dry over years?

Overcharge more than likely the cell was regularly topped up and although it was connected by a Thai man all the connections were taped to the point they could have prevented a 600v short using 16mm aluminium cable

Solarequine said:

For a while it worked and then it fizzled out on me. Big thing is my controller will not show 24 V going through it. Only 13 volts and I am stuck on what I have done wrong!

Click to expand...

Damage the battery with over discharge? Is one battery in protect mode? Try charging separately at 12v, then put back in series.

Im going to try to charge my batteries seperately and see!