solar charge controller and domestic inverter. incompatible?

[pashmina]

Hi guys. I'm setting up a system in India, where there are frequent all-day power cuts, and lots of sun.

I've hooked up a 500w/24v array to two series batteries via a 20A charge controller. I've also connected a 1400w 24v inverter to the batteries (the domestic kind popular here, that normally charges the battery when the mains is on). The problem is, when the solar array is connected and the controller shows it's charging, after a minute or so the inverter gives a 'low voltage' alarm and shuts off, even though the batteries are fully charged (showing 28v). Disconnect the solar panels and it's fine.
Is it possible the controller pwm or something is messing up the inverter somehow? Are they incompatible?
I've noticed you can get special Solar Hybrid inverters for just this job. Do I really need to replace my standard inverter with one of these?

[Bala]

've also connected a 1400w 24v inverter to the batteries (the domestic kind popular here, that normally charges the battery when the mains is on).

standard inverters do not charge batteries, they change DC to AC,

It should be: panels, charge controller, batteries, inverter,

if you want to charge the batteries from the mains then you will need to add in a charger, or an inverter/charger,

Have you got the A/C of the inverter connected to your mains power??????????

[pashmina]

not (quite) that dumb

The inverter I'm using is a Inverter/Charger already installed and working, but with no pv. All I've done is hook up the pv+controller to the battery as an additional source of charging current that doesn't depend on the mains, which is often cut off during the daytime.

[Bala]

Im sorry, your thread was a bit confusing to me, It did sound like you had an inverter charger

[pashmina]

My fault

I'm such a n00b at this. I need learn to get my terminology straight.

[Mike90250]

Even if your solar charge controller has a LOAD terminal for 12V gear - DON'T use it. Generally, it's not rated for high amps and will blow out the solar charge controller.

Use a volt meter, and see if your batteries are charging .

When power is restored, switch off appliances, so the juice can be used to recharge the weak batteries, after a short while (30 min or so) turn gear back on.

Since the original post is pretty confusing, please describe the setup a bit more and include a sketch of how things are wired

[pashmina]

this is the set up

I'll try to explain better...

There's an existing inverter/charger set up as follows:

battery----------

[Mike90250]

One cause for low voltage, is undersized wire. Another is the charger not actually charging the batteries. You need to use a volt meter to verify what the voltages are, and if thye are trending higher or lower.

Can you post the mfg and model & and links to the gear you are using ? I can not see any reason adding a solar charge controller of any kind, could reduce the voltage sensed by the inverter and shut it down.

Possibly try removing the solar charge controller, and wire panels directly to the batteries, verify they are charging the batteries, and see what happens. (don't leave it alone for long, you don't want to overcharge the batteries.)

Are the wires on the charge controller connected properly?

[pashmina]

Update -solved

Ok, I think I may have solved it. As suggested, I temporarily connected the pv directly to the battery and watched the voltage. It climbed steadily from 28v, and when it reached about 30.5v, the inverter/charger threw its 'low voltage' alarm, which I suspect was actually a battery OVER voltage cutout.

The Phocos charge controller I'm using has a facility for using sealed batteries as opposed to vented, which I understand reduces the upper voltage limit to avoid gassing gel batteries. With that setting, the controller limits the charge voltage to about 28.5v and now the inverter/charger doesn't cut out. Hurrah!

So thank you Mike, for making the suggestion that led me to the answer.

[digimart]

I have installed similar setup as yours :

I already had a UPS ( Inverter + Charger ) with 4 batteries working on 48 VDC, and with capacity of 3 KVA.

I have now installed 8 pannels of 100 watts each ( total panels 800 Watts ) to a PMW charge controller ( 24/48V upto 30 Amps ). Cable from charge controller has been attached to one starting and one ending terminals of the battery bank.

You can view the pics of my setup in the attach album on my page.

To my good luck my system is working flawlessly from last 2 weeks. For about 4 hours in a day i switch on AC-Mains, and the rest 19 hours its solar panels and batteries.

[simonbond]

I was looking for some threads to know about the solar charge controller and domestic inverters. Your thread has cleared everything to me. Thanks for this informational thread. Keep sharing like this.

[pashmina]

What confused me was that the inverter/charger (aka UPS) was flashing the 'low voltage' indicator when it really meant 'voltage too high'. In fact, setting the 'sealed battery' option on the charge controller did not completely solve the problem. I think the controller does some kind of 'equalization' function which involves temporarily raising the battery charge voltage, which trips out the UPS again (please correct me if I'm wrong here).

I have now switched from the Videocon Dual Tech 1425 UPS I was using to a Su-Kam 'Smiley' model, which seems to have a higher over-voltage trip limit (more than 29.2v) and it seems to be okay.

If continual battery state monitoring and manual intervention (i.e. switching off the mains supply when the sun is out) are an option, then there's no problem. However (being lazy), I would like to just leave it switched on all the time. Does anyone know if there is a downside to this, and whether investing in a 'solar hybrid' inverter would be worth it? Presumably such a device would intelligently manage the distribution of solar and mains charging sources.