Controller with generator backup

[RogerSun]

I am managing a solar powered network in a remote location.
Currently we can get just by with 4 x 100 watt panels and 4 x 90AH 12V batteries.
We have enough power to make it trough the night but not much to spare.
Beside adding some panels and one or two more batteries I would like to be able to charge the batteries with a generator when needed.

In a previous attempt to change the batteries in parallel with the solar controller the controller broke down.
According to the instructions that came with the charge controller I cannot disconnect the batteries as the controller might get damaged when power supplied buy the panels has no where else to go. So I cannot use a switch to disconnect the controller and fire up the generator to give the batteries a boost.

Any suggestions how to solve this problem?
What charge controller can handle this?

Thanks for your advice,


Rogier

[Sunking]

Why would you need to disconnect the batteries to charge with a generator?. That is just plain silly.You do not need any switch, just connect the AC charger, start th egenerator, and turn the charger on. Your Controller will not care. If you had the system designed properly you would not need to run the genny everyday.

FWIW your whole system is poorly designed. You panels should be sized to generate 1.5 times more energy than you use in a 24 hours period, Batteries sized for 5 days so if you have 3 cloudy days before you have to run on generator. In addition to having 5 day battery capacity also makes the batteries last much longer. A battery discharge 20% per day will last around 5 to 7 years. A battery fully discharged everyday is good for about 6 months.

Lastly you should not use 12 volt batteries in parallel If you needed 400 AH then buy 400 AH battery. Those will be 6-volt batteries. Your way fully dischargging them every day, and in parallel gives you real short battery life and costing you a lot more money in the long run.

[RogerSun]

Hi Sunking,

Thanks for your quick reply.

When I started this system I way underestimated how much power a Satellite modem uses. These things suck between 80 and 100 watts 24/7
Had I known we would need 4KW per day to keep the system running I would have chosen larger batteries, But this is what we have....

I started with one battery and two panels thinking we had 400% capacity. Witch turns out to be only 25%...
So we started to add batteries and panels until the system would stay online. Until recently the 4 panels would change the batteries to 100% by 2PM. But now the winter has set in that's not longer the case.

The current controller is a Renogy 40 Amp MPPT

https://www.renogy.com/renogy-40-amp-mppt-solar-charge-controller/

We had mayor trouble in the beginning and it turned out to be a faulty controller witch they replaced. Perhaps it was bad from the beginning. I assumed that the parallel charging damaged it.

I will start by adding more batteries (these are Marine Deep Cycle batteries) to get more buffer and increase their life span.

Can I add different batteries?
For example add two big 6v batteries in series connected to this 12 volt bank?

[bcroe]

Those 100W panels are extremely uneconomical compared to say, 250W (standard grid tie) panels. It appears your
panels don't have optimum angle, unless you are close to the equator. You would do much better under clouds and
into winter with a few big panels properly elevated. Plus fix problems noted above. Bruce Roe

[RogerSun]

These panels were cheap enough and economy per sq ft doesn't bother me in this case.
Usually the batteries are charged by 2PM not sure if building a rig to to adjust the angle will make a significant difference or does it?
Only interested in changing the angle if I can get say 30% extra out of these panels otherwise I will just add a few more.

I will aks my question about mixing the batteries in the appropriate section of this forum.

Thanks!

Rogier

[bcroe]

What is your latitude? Laying the panels near flat hurts you most in winter, just when you need energy the most. One approach is
get enough panels suitably aimed for satisfactory winter service. They will be more than enough for summer, with less than optimum
angle. Bruce

[RogerSun]

Have a look at this picture, the first one might make it have it look like it was near flat. But this roof has a normal pitch.
IMG_3082.jpg

[Mike90250]

A generator powering a quality charger, will not damage batteries, Solar Charge controller, or any of your loads.
BUT using a AC powered CRANKING charger could fry a lot of things.

[RogerSun]

What do you mean by "Cranking Charger" ?-)

[SunEagle]

What do you mean by "Cranking Charger" ?-)

A lot of car battery chargers have the ability to supply "cranking amps" which should be able to start the vehicle without having a fully charged battery.

While those type chargers are great for a standard FLA auto battery that usually have higher voltage charging set points that can easily over charge a deep cell battery especially if it is an AGM or something other than FLA.

[Mike90250]

What do you mean by "Cranking Charger" ?-)

One of those big wheeled charging units that car dealers use to charge a dead battery in 3 minutes, it dumps +80 amps into the battery, Only way to do that, is with about 40 volts, which will fry a bunch of stuff on the 12V line.