Easiest way to regulate 12V from solar charged battery??

[Dunk_c]

Hi Everyone

Can I get some advice please.

I have a solar charged SLA bank that has an absorption voltage that gets up to 15v when it is cold.  I have noticed that the DC-DC laptop charger I use on the battery cannot maintain a stable 19v output when the batteries are being charged at the higher voltages.  Any ideas why?

This prompts me to find an easy way to make/buy a 12  instant voltage DC regulator.  It would have to cope with maybe 200w of output as I sometimes have two laptops charging. I have read about LT3790.  Are there any Chinese converters online using this?

Is there a simple solution such as buying several cheap eBay buck/boost synchronous converters and using the in parallel to get the power needed?

If not I'll just run off the inverter but I think this is less efficient and would prefer to stay at 12v and round trip through 240v.

Thanks

[Dunk_c]

Anyone there?

[Chalcogenide]

What kind of voltage variation are you suffering? It's quite strange that the boost converter cannot maintain regulation, unless you are somehow exceeding the input voltage limit of the IC. Does the battery voltage drop significantly under load? When batteries are cold, not only the voltage might increase but the ESR increases quite a bit so maybe this could be causing the issue as well.

[Dunk_c]

It is varies rapidly between ~17v and 19v when battery is at 14.6v.  When battery is is floating at 13.6v, the DC-DC converter is able to hold 19v stably.  Sorry for my vague initial description.

Can buck converters cope with continuously varying input voltage and maintain constant output voltage?

[Seekonk]

Frankly, I am not sure what you are trying to say.  Silicon Chip had a boost converter for a car that had to have a diode or two in series with the battery in order to boost properly.  Some boost converters need to boost at least 2V over supply in order to work properly.  I don't think that is the problem here.