solar charge controller

[thurkh]

I recently mounted a residential 400 Watt solar panel on top of my 24' bumper pull trailer.
I have now discovered this panel puts out 39 Volts DC. I am really struggling to find a reasonable priced charge controller for this panel.. I have two deep cycle lead acid batteries to charge for now. Any suggestions.

[SJ-Chris]

With a panel with that high of voltage, you will need an MPPT solar charge controller. Unfortunately, they are a lot more expensive compared to PWM.


With 400w, you will need a minimum of a 20amp MPPT solar charge controller (...that's actually a bit undersized for 400w). From your post, it sounds like you might in the future want to add more solar. If that's the case, you might as well bite the bullet now and buy a 50-60amp MPPT solar charge controller. That way you won't need a new one in the future.


The cost at the low end for say a 30a MPPT solar charge controller will be ~$80-90. The price goes up from there.


Note: There are many PWM cheap (<$20) controllers on Amazon that say they are MPPT, but they are not.


If cost is the utmost importance, you might find a used on for sale on facebook marketplace or craigslist.


Good luck!
Chris

[SafariBen]

Agree with everything SJchris said. Technically a PWM controller will work, but won't step up the amperage with the voltage drop, so you'll be losing a big part of the power from the 400w panel, up to 2/3 if the panel is pointed at full sun. BUT, if you only use the batteries once a week, and they have enough power for current use, then they'll be fully charged in two average days and it makes no difference at this point. The panels are getting to be the cheapest part of the system, especially when you consider the life of the different components.

[Tomahawk]

I use a residential panel as a portable setup. The panel nominal voltage is 24V. I am not sure what the open circuit voltage. I have been using the EPEVER 30A MPPT for about 6 years. It is current around $175. I use my TT about 3 or 4 weeks a year and I am almost always dry camping without power.

[ppine]

Go with MTTP controller because it is more efficient and means you need less solar panels to do the same job. 30 amp would be a minimum.. 40 amp would be much better.

[Stircrazy1]

should be able to find a good MPPT charger for under 200 bucks for one panel. you can go with a renogy rover mppt 20amp which will take a 520 watt panel, no room really if you want to put a second panel on but that's on sale for 79 bucks, the 40 amp version is on sale for 159.00 that would let you throw a second panel up easy.

[B-Man]

Buy once, cry once. You can get an excellent quality, Bluetooth-enabled Victron 100/30 for $127. Victron 100/30 MPPT

98% efficient, 45 days of on-board performance data storage, 30ma self-consumption, cell phone app is excellent for seeing what is happening with the MPPT and your batteries. If you add additional Victron equipment it will network easily and they all work with the same app.

If you are planning to add a panel in the future you can series it in but I would go to the 100/50 for $40 more. The 100/30 will provide 440 watts of charging power at 12V. The 100/50 takes that to 700 watts.

Both will auto-sense the battery and both can work with 24V systems as well. If you go to 24V you will see double the charge power capability with the same unit.

[Sunnyfalls]

PWM solar charge controllers are less efficient, less cost, but are more robust a design that is less likely to fail than MPPT solar controllers. What is more important than the specific type of charge controller that you select is to FIRST MINIMIZE and DETERMINE what your maximum daily solar panel AH replenishment needs to be and THEN DESIGN and SELECT your solar panel capacity AND charge controller COMBINATION such that this AH replenishment can be accomplished in 4 hours or less under good solar conditions.

You can use more solar panel capacity and a more robust, lower cost, less efficient PWM solar charge controller to accomplish this design requirement. Or you can use a less robust, higher cost, more efficient MPPT charge controller to accomplish this design requirement. Total cost for either approach is similar, but the PWM approach results in a design that is less likely to fail when you do a lot of dry camping. And keeping a spare PWM on hand doesn't cost much either.

Gayle & Bob
"Los Gatos Casita"

[SteveJ.]

Avoid Renogy anything except panels. Their quality is quite uneven and customer "service" is atrocious for some people.

I've had a Victron 100/30 in service for 4 years, no reliability issues. Wonderful app. The one slight negative is that it will not turn on until the panel voltage is 5 volts higher than the battery voltage. This is not an issue with higher voltage panels but is problematic nominal 12 volt panels.

[Sunnyfalls]

Originally Posted by SteveJ.

Avoid Renogy anything except panels. Their quality is quite uneven and customer "service" is atrocious for some people.

I've had a Victron 100/30 in service for 4 years, no reliability issues. Wonderful app. The one slight negative is that it will not turn on until the panel voltage is 5 volts higher than the battery voltage. This is not an issue with higher voltage panels but is problematic nominal 12 volt panels.

Yeah, I have heard that too, but our actual experience has been just the opposite...

I have found Victron to be over-priced and largely no better than anything else. Same with BattleBorn batteries too. But being an engineer, I tend to open up everything to see how it was designed and access the overall build quality. We have been 100% happy with our Renogy products which include their 200 Watt portable solar suitcase, 100AH LiFePO4 Smart Self-Heating Battery and 3000 Watt Inverter.

I can't comment on customer service as we have never needed it. Same for Starlink too. However, I am fairly certain that folks who experience premature failure of these systems is more likely the result of abuse and misuse of these systems. This is especially true when using LiFePO4 batteries and the larger Inverters.

https://lithionicsbattery.com/wp-con...sh-Current.pdf

And for sailboats and RVs, I think it is best to keep things as simple as possible. It easy to be temped by bells and whistles that tend to reduce overall reliability in the long run.

Gayle & Bob
"Los Gatos Casita"

[Marine359]

Hey, Black Friday sales on now. If you think you may need more battery capacity and a big inverter, you can buy a mid-size powerstation. Their built in mppt controllers love high voltage. Just food for thought.

[Sunnyfalls]

Don't see any advantage...only disadvantage? These so caled "powerstations" combine a LiFePO4 battery, charger and an Inverter in one heavy package. So if any one of these three components fail, you are SOL and have to replace the entire, expensive unit. So prefer having these three components be separate and installed in the RV so don't have to physically carry them around and can just replace one component if it fails...and then use a proper extension cord plugged into one the RVs exterior 120/240VAC electrical outlets to provide the additional distance desired. Our truck has a 120VAC electrical outlet too.

Gayle & Bob
"Los Gatos Casita"

[creativepart]

Another vote for a Victron 100/30 for $128. Could you spend less? Probably but no one buys an RV to save $50.

https://www.amazon.com/SmartSolar-MP.../dp/B073ZJ3L13

[Stircrazy1]

Originally Posted by SteveJ.

Avoid Renogy anything except panels. Their quality is quite uneven and customer "service" is atrocious for some people.

I've had a Victron 100/30 in service for 4 years, no reliability issues. Wonderful app. The one slight negative is that it will not turn on until the panel voltage is 5 volts higher than the battery voltage. This is not an issue with higher voltage panels but is problematic nominal 12 volt panels.

the only thing renogy I have heard to avoid is the batteries. I have a renogy solar controller for the last 5 years, works perfect, a dc to dc works perfect and and inverter charger, once again works perfect. I wouldn't spend the 3x more mony for Victron as its just not worth the extra money.