Panels producing too much voltage

[SunEagle]

No, I think the charge controller is working just as it is designed. On-Off style style controllers do not stay on and continue to charge, they do not provide a float voltage. As the battery degrades, the on-off cycling becomes more pronounced. The current delivered during the on portion is enough to spike the voltage above the cut-off due to the batteries internal resistance, but after the charge current is removed, the battery quickly rests back to below the trigger voltage, turning the controller back on. This cycle continues for as long as decent charge current is available.

If this is the only controller those batteries have ever seen, they are probably in rough shape, having never been given a real absorb or float voltage (let alone EQ, if FLA). A better controller will help, but new batteries are probably in the OP's future.

An inexpensive controller that would be an upgrade to what the OP has now:

https://www.amazon.com/ALLPOWERS-Con.../dp/B01MU0WMGT

Mppt is worth considering if the system will ever grow, but is not always worth the money for small (<250 W) systems.

I see your reasoning and agree.

[littleharbor]

If you do ebay you can find that exact controller for around 12 bucks.

[symbiosis]

Thanks again for the replies and what you say makes sense to me as well and explains the off/on cycling. My total panel wattage is just under 300 (so small) but think I will need a min 30 amp controller? So (to put it into simple terms) what is happening is that during the summer my panels are quickly charging my battery up past 14.2 v (the safety voltage overload disconnect on my existing controller), which then prompts it to disconnect the solar input (as it should) but then the battery voltage immediately drops below 13.4 v (the re-connect setting) and so the cycle begins again.... What does the float option do and (in this circumstance) what should I be setting it at please?

[symbiosis]

I'm in the UK - does this look suitable please https://www.amazon.co.uk/MOHOO-12V-2.../dp/B01KV1GTQG

[littleharbor]

Same controller, so yes suitable. Don't know the exchange rate, what's that in USD$?

[Sunking]

At night, my controller tells me my battery is around 12.8 v

That would be a FULLY CHARGED BATTERY

[symbiosis]

Same controller, so yes suitable. Don't know the exchange rate, what's that in USD$?

Around $30

[symbiosis]

So if my battery ends up fully charged, is this constant connect/dsconnect actually doing any harm to my system?

[inetdog]

So if my battery ends up fully charged, is this constant connect/dsconnect actually doing any harm to my system?

A bit of harm to the batteries, not to the panels, wiring or inverter. It is contributing to unnecessary cycling (although micro-cycling) of the battery and it is either steadily overcharging or failing to charge properly, since it is not maintaining a proper float voltage.

[symbiosis]

Thanks. The charger that was suggested (and the one I linked to) states it has Float Charge: 13V (default,adjustable) - is that what I need to prevent this happening and (as its adjustable) its 13 v optimum?

[sensij]

Thanks. The charger that was suggested (and the one I linked to) states it has Float Charge: 13V (default,adjustable) - is that what I need to prevent this happening and (as its adjustable) its 13 v optimum?

I think you'll find that the Amazon description is incorrect, and that the charger documentation will indicate 13.7 V default for float. That is a typical value for lead acid... if your battery manufacturer has a recommendation for your specific batteries, you should follow that.

[jflorey2]

So if my battery ends up fully charged, is this constant connect/dsconnect actually doing any harm to my system?

It's how it is supposed to work, so no - not much.

[Sunking]

Thanks. The charger that was suggested (and the one I linked to) states it has Float Charge: 13V (default,adjustable) - is that what I need to prevent this happening and (as its adjustable) its 13 v optimum?

Float Voltage is not 13.0 volts. It depends on the battery and will be between 13.2 to 13.8.

[symbiosis]

Thanks again - here's all the info I can find on my battery http://www.systems-sunlight.com/wp-c...-12v-200ah.pdf

[Sunking]

I can help you with the voltages, but I doubt your controller has the ability to be set correctly. Additionally some of the claims the manufacture makes is let's just say optimistic. Your battery is made for Float Service in a UPS.

Set the Bulk/Absorb to 14.6 volts and Float to 13.6 volts.