12 volt lights on a 24 volt system?

The best option for this upgrade, IMO, is an additional controller/larger controller and parallel the outputs to the existing 12 V battery bank. By the time you are done purchasing and installing the 24V->12V converter, the additional cabling, the circuit protection, and hardware, the second controller is the less expensive route.

If you keep the same stuff but add two more panels you have options:

A. Second controller for the new panels and put the two controllers in parallel on the battery bank (BTDT, works great)

B. Get a new 24v inverter for the big things like MW, toaster, kettle, and the 24-12 converter to run everything else while the batts are wired as 24v

Compare cost of A and B.

C ? I don't know if you prefer to have a big inverter and a little inverter to run big 120v stuff and little 120v stuff, but if you still want a little inverter to run the little stuff, then I am unclear what you should do.

On that---I recently decided to ditch the little inverter and just use the big inverter for everything, using its remote on/off switch more. The AH saved by having the second small inverter was trivial. So back to A or B.

JiminDenver wrote:
So use the converter listed above for the 12v stuff off of the 24v bank. I would think two of the panels in series paralleled with the second pair to guaranty enough voltage for a 24 volt bank. BFL tested a 24 volt panel on a 24 volt bank and there wasn't much head room to work with.

24-24 gets more amps with a buck converter controller than 24-12 even with the 60 cell panel. The issue of "overhead" arises with the 60 cell panel vs 72 cell panel.

I had no trouble getting the single 60 cell panel to raise the battery voltage to 30v, but it stalled out there. So it was able to fully charge the batteries but would not have been able to equalize them.

I can't remember if that limit was the same with MPPT and PWM. They got the same amps at 24-24, more than MPPT doing 24-12.

Salvo suggested elsewhere that you might try two 36 cell 12s in series instead of a single 60 cell 24 to beat that. (72 cell 24s are not common anymore it seems) That would not work with my older version Eco-Worthy MPPT which has a Voc limit of 42v, but it could work with the newer version that has a 50v VOC limit.

675 Ah @ 12v. Panels were in series so the conversion was huge.

JiminDenver wrote:
When I had 970w on my TS-MPPT-60 I noticed that at times the array was putting out 800w but the controller was only using 660w. I know it was running hot and am wondering if it was limiting the output to protect the controller.

Into 12 or 24 volt battery?

When I had 970w on my TS-MPPT-60 I noticed that at times the array was putting out 800w but the controller was only using 660w. I know it was running hot and am wondering if it was limiting the output to protect the controller.

JRRNeiklot wrote:
what other steps are necessary to get my trailer up to speed and have lights, water pump, etc running? I apologize for my ignorance.

Did you miss my first post?

Recently upgraded to 700W. But the 30W MPPT controller ignores some of that on bright/sunny cold days. No problem though, as I really only need all that panel space on cloudy/rainy days; and then the controller is not wasting any of it.

Thought about going to 24V so the controller can use all the amps on bright/sunny days, and may do it if I ever really need that max wattage.

So use the converter listed above for the 12v stuff off of the 24v bank. I would think two of the panels in series paralleled with the second pair to guaranty enough voltage for a 24 volt bank. BFL tested a 24 volt panel on a 24 volt bank and there wasn't much head room to work with.