Controller dead, can I connect solar panel direct?

[bcripps]

My year-old Outback controller bit the dust. Another on order: NOT Outback!

In the meantime, can I wire the panel directly to the battery posts with a fuse in place?

Thanks,
Bry

[newhaul]

Questions
What size panel
What size battery bank
Liveaboard
On mooring
In marina
Daily draws
Your location
Answers to these will help advise you
The short of it if panels are same voltage as bank yes it will work just be.careful not to over charge bank and fry batteries.

[zeehag]

i do that with one panel and have 3 via controller. when i donot need to hard charge batts i cover the panel that is directly wired to batteries.
you will want to check batteries daily until you figure out the rate of charge and so you donot harm your batteries. mine is a smaller panel , only 2.5 amp output so i donot worry , a si know my bank of batteries can tolerate it for a couple of days.
if you have large panels, i would not do this. if you have a smaller one you can do this with, is not a bad idea. just continue checking frequently.
everyone is gonna say you are gonna burn down your boat and die, but i know better., ha ha ha ha ha

[Dsanduril]

The short answer is "yes", but the long answer is it's complicated. Solar panels are a current source, so even if you have a 40V panel, if the battery can accept all of the current then the battery will "control" the voltage at whatever level is required to get that current into the battery.

The problems will come in when the battery can no longer accept all of the available current. At that point the voltage will start to rise until you reach the panel's nominal voltage. If you have a 16V panel, and are operating in hot environment where the actual voltage is less then that may not be a big deal. If you have a 40V panel then it could ruin your batteries and pretty much every piece of electronics you have connected to the system.

It used to be quite common to wire small 16/18V panels direct to batteries on the assumption that they would never get the battery fully topped up and thus no controller was required. But, if your panel(s) is capable of fully charging the battery then you won't have any control of the voltage once the batteries are full.\

[EDIT] - Unless, as Zeehag notes you can manually control charging by covering or disconnecting your panel, but then you are the fallible human controller.

[bcripps]

Thanks everyone. Specifics:
50 watt panel
two 85 amp AGM Trojan batteries
Liveaboard on mooring
Daily draw... a couple of fans, computer charging
Located in the Dominican Republic

New controller is on order but damn, this is the hottest month of the year! Really need my 2 Hella fans. Lost the Outback controller during Irma. No idea why. But just need to put some juice back into the batteries.
Thanks,
Bry

[newhaul]

Originally Posted by bcripps

Thanks everyone. Specifics:
50 watt panel
two 85 amp AGM Trojan batteries
Liveaboard on mooring
Daily draw... a couple of fans, computer charging
Located in the Dominican Republic

New controller is on order but damn, this is the hottest month of the year! Really need my 2 Hella fans. Lost the Outback controller during Irma. No idea why. But just need to put some juice back into the batteries.
Thanks,
Bry

Ok with those specs I see no issue with direct hookup to the house bank just leave the fans running . Untill you get the new controller.

[Paul Elliott]

And monitor the battery voltage in the afternoon. Fans running or not, if your panels are generating more power than you use, you will eventually overcharge the batteries. One time I did the direct connection after my controller failed. At sea there was no way that they would overcharge the batteries; the best they did was to slow the rate of discharge. But when we reached shore I would have to disconnect the panels around Noon before the batteries got too full.

[bcripps]

That's great news... we are dying over here with the heat. I'll keep fans running (no problem), and monitor the batteries. New controller should arrive on the 24th. We can manage from there.

Much thanks,
Bry

[Dsanduril]

At the very best your panel will put out a little less than 4A into the system, and with a couple of fans running you'll be lucky to see 1A into the batteries, suspect you'll never have to worry about voltage. But, keep an eye out in the afternoon and make sure. You can always turn on a light or two to use up the rest of the power if you don't want to disconnect the panel.

[icemate]

Originally Posted by bcripps

Thanks everyone. Specifics:
50 watt panel
two 85 amp AGM Trojan batteries
Liveaboard on mooring
Daily draw... a couple of fans, computer charging
Located in the Dominican Republic

New controller is on order but damn, this is the hottest month of the year! Really need my 2 Hella fans. Lost the Outback controller during Irma. No idea why. But just need to put some juice back into the batteries.
Thanks,
Bry

If it were mine, I would leave the fans running while hot wired to solar panels. Maybe a light or two. That may keep battery from topping off and frying.

[thinwater]

You can also easily turn the panel off by simply covering it with a towel. Do this while connecting and instead of running a fan, when the fan is not needed. So simple.

[newhaul]

Originally Posted by thinwater

You can also easily turn the panel off by simply covering it with a towel. Do this while connecting and instead of running a fan, when the fan is not needed. So simple.

Covering panel during hookup is a is a good idea if the panel was big. Also he is in dominica so this time of year the fans are needed 24/7.

[SimonV]

My only thought is you will at midday you could be pumping in Amps at 17 to 21 volts.

[bcripps]

Thanks everyone. Yes, i get 20 volts off the panel in noonday sun. I'm watching carefully and the fans are running. If I get nervous, I plug in the computer.

So yes, working well and the new controller is on the way.

Thank you so much,
Bry

[john61ct]

No problem at all for the batts, just be careful of electronic load devices that may not like high voltages as/if bank gets close to full.