12v battery/ 12./24v MPPT ~ 24v PV Panel

I have done it with PWM. It all depends on your controller. Some controllers recommend against it, others like it just fine.

Many people do this with MPPT.

Jim

I may have missed it somewhere reading through this thread. Blame it to being O&S.

Anyone have hands on, charging 12v batts, using MPPT or PWM controllars with 24v panel?

I will try soon but would like someone to perhaps chime in and say, yes, NO problems.

Hi KJ,

I believe Blue Sky for the 3024di says 98% @ 17 volts and 96% @ 30 volts input. I agree that line losses can be significant. My RV came with a #10 prewire. To use it with low losses I chose to go series parallel for the Unisolar panels (system voltage @ 33). That gave me a line loss of under 1%. (dual #12 from panels to combiner box, #10 to the controller, #8 from controller to battery banks).

I believe I'd choose the new Rogue 3048, when the time to add panels comes around. I can't justify it yet, as I keep failing to run out of power. *grin*

I do wish Marc had chosen to do a 6048 Rogue. If he had, I might have "started over" and would aim at 1200 watts of solar.

I'm currently sending 170 watts (13v, 13a) to the battery banks from 256 watts of flat installed panels at 10:30 a.m. local time. I've deliberately forced equalization mode as my house keeper is running an 1100 watt vacuum cleaner. I'll be doing about 45 minutes of driving so that should pump about 15 amp-hours back into the bank.

PT

I do not believe I said all Blue Sky controllers were cheap - what I said is that the one I had the misfortune of looking at had a "JUNK" MPPT tracking system with a user adjustable pot nothing more - to me that's cheap junk

A bit of a correction / explanation is needed for your earlier statement
"The higher the input voltage the more of the energy will be wasted as heat inside the controller--so it still behooves one to use lower voltages unless you wish to save on the cost of #4 wire to the controller from the roof."

The losses in a properly designed buck conversion stage is negligible at best with higher voltages, the advantages far out way any potential loss. Smaller more flexible wire, lower cost wires, easier to hide out of sight, far less line losses, P=I(squared)*R half the current 4x less line loss. Lijne losses at high current say 30 amp array current even with 4 awg wire can be 3 to 4% if running long lines - a proper buck conversion stage might have 1% loss difference between the input voltage range

This is the LandStar manual for questions on equalizing etc.
I have the 20amper. Little more price, twice the amps in case you go crazy and get more wattage of panels (nobody ever does that---)

http://www.pvsolarchina.com/wp-content/uploads/2012/09/User-Manual-of-LS1024-LS1524-LS2024-Solar-Controller.pdf

I have two of these 20ampers in parallel on the one battery bank and they operate just as one 40amper would for the charging profile going to Absorption and then to Float just as shown in the manual. No issues.

Yes, as I have posted in the past, these manuals seem to have been written by the same guy who writes the Morningstar manuals. Same drawings too. Can't say who is copying whom, or if MS is made by the same factory.

You MPPT guys getting into all this is very useful in learning about the various aspects. Seems to be quite a few aspects to juggle.

Load terminals. I guess that is for timed things like somebody said before. Actual loads are off the battery anyway and the solar just tops up the battery while the load is running, so why bother having a "diversion" when there is extra solar such as in the afternoon? Can't see any difference. If the panels would do 15 amps on a low battery but can only do 5 on the near full battery, you can run 10amps of load "for free" with no effect on the battery.

Hi KJINTF,

The Blue Sky 3024 is not what I'd call "cheap" and works fairly well. It does have "load" terminals and in the latest iteration can do a diversion load of 20 amps. I'd find that a useful feature.

Interestingly enough the Morningstar MPPT units don't do diversion loading--so that load feature perks my interest. I've maxed out my 3024 and will either have to buy a "slave" or have another independent controller when I upgrade the solar watts.

KJINTF wrote:
BLF

My first reaction would have to be the old adage "You get What You Pay for"
They copied / pasted the MS manual in many places.........
Looks as if they tossed in several useless features to make it look good. An example the load function which is typically only seen on low cost low power units

BFL13

Do you know the logic for the LS1024 as to when it may equalize? MS claims once ever 28 days and epsolar manuals speak of when it detects overly discharge batt?
I'm interested in the waterproof LS1024RP

The 4210 has various efficiency curves in the back of the manual that shows a drop as the panel wattage increases and shifts as for 17v, 34v, and 68v

http://www.epsolarpv.com/en/uploads/news/201304/1366686104517198.pdf

Hi BFL13,

volts x amps = watts

380 watts max @ 12 volt out for the 30 amp
480 watts max @ 12 volt out for the 40 amp

Input voltage is independent of power out (so long as it is below 30 and 40, respectively) and only indicates a limitation of the controller's input parameters.

You could feed the 30 amp 150 volts @ 2.4 amps; or 100 volts at 3.8 amps. The wattage going into the controller remains the same in both cases.

The higher the input voltage the more of the energy will be wasted as heat inside the controller--so it still behooves one to use lower voltages unless you wish to save on the cost of #4 wire to the controller from the roof.

BFL13 wrote:
Doesn't that mean the 30 amper can have more total Voc and so more panels, but they have to be smaller to not go over the watts limit?
Seems backwards to me.

BLF

My first reaction would have to be the old adage "You get What You Pay for"
They copied / pasted the MS manual in many places.........
Looks as if they tossed in several useless features to make it look good. An example the load function which is typically only seen on low cost low power units

A few specifics
1 – Very limited configuration possibilities. That little numerical display would drive me nuts. The battery charge parameters are a bit limited
2 – External communications limited to none available. No way to interface a computer or anything else to remotely view status, system information, etc..
3 – No voltage sense line - not a big deal in many installs but for me a requirement when above about 25 amp capability
5 – No mention of meeting any World-wide electrical or safety standards. Could be fire and safety issues and or insurance issues your RV
6 – Limited built in fault prevention and alarms
7 – No battery EQ capability
8 – MPPT Tracking – unknown but looks better than some of the Blue Sky offerings with their "joke" user adjustable pots

That said for the price it might be worth taking a closer look at it. Some of the missing functionality might not impact the typical set and forget installation.

I would love to get my hands on one to play with it

They say the 4210 has "Several seconds tracking speed" and claim this is "rapid tracking" for various temperatures.