RV solar noob here

[chrisski]

With flooded batteries & solar & being idle.

1) it's harder to overcharge than you think. If your hydrometer was reading 105% charge, something is off.

The other thing is maybe you are reading 105% full because the temp compensation was off, or at some point in time, electrolyte was added to refill, instead of distilled.

To avoid hijacking the OP's thread with my learning points, I've put my response in my "https://www.solarpaneltalk.com/forum...charger-to-buy" Thread

[Mike90250]

With flooded batteries & solar & being idle.
1) it's harder to overcharge than you think. If your hydrometer was reading 105% charge, something is off. Once all the sulfur has been driven into the electrolyte from the plates, you can't overcharge. You can still pump power into the cells, and you are now electrolizing water to gas, creating lots of bubbles of Oxygen and Hydrogen. This can raise the tempature a bit and that causes the electrolyte to expand in volume. If you had recently topped off the electrolyte with distilled water, this can sometimes cause the cell to overflow, which many people think they are boiling over. They aren't likely to be boiling with only a couple hundred watts. But if they are full, and sitting on a solar charger, that goes thru a Bulk and a 120 minute Absorb (or Boost) cycle, they will use a lot of water and some unnecessary plate material shedding, but it's preferable to being sulfated. Some chargers you can set the controller to a Float Duty, like exit signs, which only come on once a year. Then a day or two before you activate the RV for a trip, re-set to Cycle Duty, which changes the voltage back up.

The other thing is maybe you are reading 105% full because the temp compensation was off, or at some point in time, electrolyte was added to refill, instead of distilled.

But you don't want to be doing a daily Absorb for very much time, while the bank is idle, it just wastes water.

[chrisski]

Noob here again. It's been interesting watching the back and forth here, and I'm going to ask my EE son to peruse it and tell me what it means. Let me go back to my basic question though. First of all, I purchased the single 100w panel because I simply want to use it as a trickle charger to keep my batteries topped up, because i dont have shore power where i normally park it when not in use. It seems to do that quite admirably; ie it'll take 70% batteries up to 100% in 4-5 hrs or less. (I've never seen it charge at much over 13v) My real problem, and the obvious reason (to me) to have the controller is too prevent it from overcharging my batteries. The controller (HP 2410) is giving me different readings on battery level, depending on whether the panel is plugged in or not. The readings are much lower when plugged in, and seem more accurate wen its unplugged, because its consistent with the trailer's monitor panel. Is the controller the problem or am I misunderstanding the readings?

First, I hope your EE son can answer the electrical questions better than my Computer Science Major kid, who every question I get seems to be outside her area if study.

Second, I just finished my first test of my batteries and with them supposed to be charge to a specific gravity of 1.277 to be 100%, mine were charged to a temperature corrected 1.285, with very little difference between the cells. So I got .008 overcharged or about 105% charged. Now, I had two chargers on these batteries, one which had the electrical readout between 50 and 75 for all four batteries, and the other had the readout between 75 and 100 for all four batteries.

Right now I trust the responses I get off this forum more than from the battery shop and more than the one or two word responses I get when I E-Mail the battery manufacture's tech dept.

Since I think there is some "art" involved in this, to ensure my batteries don't overcharge:

1) I am going to remove them from the 600 watts of Panels when I store the RV. I thought about either putting one bank of 300 watts of panels on it, or even installing a second 100 watt panel just to charge the batteries but I opted against it.

2) I have a set of shelves with a charging and measuring station I built to keep my 270 LBS of Batteries charged. Now that they are charged, I am not going to leave the float charger connected. I will take specific gravity measurements every week to determine their health, and put them on the charger.

3) If there comes a point where I get sick of lugging 270 LBS of batteries between the RV and my house, I will start with rigging a 100 Watt panel to my MPPT charge controller, and take hydrometer readings and check water levels every month. I see myself going to this option sooner than I hope. Those batteries are heavy, and I'm really not sure if they're mode to be moved around a dozen times a year.

So basically, if it comes to option 3, I will be doing something similar to you, but I will check battery health with a hydrometer to make sure they're not overcharging or undercharging.

[AWS]

I'm not a solar guru or much of electrical wiz. I do have a 100 watt solar panel on my van that runs the interior lights, furnace or fantastic fan depending on the season and chargers for laptop, kindle and phone. If I have any kind of sun it will keep my two 35 AH batteries charged. I have a Renogy PMW controller, no meters but lights, while charging(volt meter on the battery reads 14.1-3 v) the lights are on steady, when fully charged it goes into float mode one light blinking(meter reads 13.5) and when the sun goes down it is fully charged at 13.1 v. As long as the sun is shining I can stay indefinitely. The battery meter usually reads 12.1v in the morning if the furnace has run all night, it is a very low draw furnace for a vanagon that I installed in my ford van. After three years my batteries started losing power and would drop into the 11.? v range by morning and fully charged at 12.8v, I changed batteries and we are back to normal I use two 35 AH wheel chair batteries in parallel and my controller has a SLA setting.

I have a suitcase panel for the motor home(100 w) and a PMW control, the load consists of lights, 12v c-pap machine all night we still have enough power to run the furnace in the morning and the 100w panel will have the house battery(single small deep cycle) topped off 1-2 in the afternoon. stove, refer and water heater are all propane. I've changed out all the lighting to LED

I'm planning a panel for my trailer to charge my trolling motor batteries, I have two one in the canoe and the other on the charger. I'm going to use the suitcase panel for now to charge them.

[Mike90250]

Since I don't have a manual for the HP 2410, I can't comment much on it's readouts and operation. Generally, a CC is connected first to the battery and allowed to boot up, then connected to the PV. I don't know of any controller where that boot up sequence is illegal.

Interpreting the readout sometimes takes having the manual in hand to understand the display.

The points Secessus brought are valid, but extremely rare. It's much more common for a poster to appear here with circumstances like yours - 100w panel and a controller that makes no sense of what is happening. Or the ever popular MPPT sticker on a PWM controller.

The Gensun controllers are the only brand I have ever heard of that provide boost to charge a battery

https://genasun.eu/collections/genasun-boost-mppts/products/genasun-gvb-8-lead-acid-12-volt-wp-mppt-2017

Secessus - if you would like to start a thread in Off-Grid about reliable, low cost MPPT or PPT controllers, that would be a welcome addition, and we can refer questions to it.
with so many counterfeit products on amazing and allibabba , I can't keep it all straight.
Question, will gensun Boost controllers ( say for 12V battery) also perform MPPT tracking on higher voltage panels, or only boosting to battery voltage ?

[SunEagle]

Noob here again. It's been interesting watching the back and forth here, and I'm going to ask my EE son to peruse it and tell me what it means. Let me go back to my basic question though. First of all, I purchased the single 100w panel because I simply want to use it as a trickle charger to keep my batteries topped up, because i dont have shore power where i normally park it when not in use. It seems to do that quite admirably; ie it'll take 70% batteries up to 100% in 4-5 hrs or less. (I've never seen it charge at much over 13v) My real problem, and the obvious reason (to me) to have the controller is too prevent it from overcharging my batteries. The controller (HP 2410) is giving me different readings on battery level, depending on whether the panel is plugged in or not. The readings are much lower when plugged in, and seem more accurate wen its unplugged, because its consistent with the trailer's monitor panel. Is the controller the problem or am I misunderstanding the readings?

The controller may be providing the voltage it is putting out to the battery and not the battery voltage. Just something to think about. The measured voltage is not a perfect way of knowing the battery State Of Charge (SOC). The only way I know to get that data is to use a temperature compensate hydrometer to measure the acid content of each battery cell. It's more work but provides more accurate data.

[Chasleyko]

Noob here again. It's been interesting watching the back and forth here, and I'm going to ask my EE son to peruse it and tell me what it means. Let me go back to my basic question though. First of all, I purchased the single 100w panel because I simply want to use it as a trickle charger to keep my batteries topped up, because i dont have shore power where i normally park it when not in use. It seems to do that quite admirably; ie it'll take 70% batteries up to 100% in 4-5 hrs or less. (I've never seen it charge at much over 13v) My real problem, and the obvious reason (to me) to have the controller is too prevent it from overcharging my batteries. The controller (HP 2410) is giving me different readings on battery level, depending on whether the panel is plugged in or not. The readings are much lower when plugged in, and seem more accurate wen its unplugged, because its consistent with the trailer's monitor panel. Is the controller the problem or am I misunderstanding the readings?

[secessus]

> The problem is that there are so many false MPPT type CC's it would take many pages to list them all

List the known-good ones.

> we are stating a fact that for a very large percentage of CCs that do not work well with a small wattage system. You can disagree but please don't label our posts as FUD."

So say it that way without the "low cost MPPT" language. That language is what makes it FUD.

> What I try to say is that the decision to purchase what they are looking at is up to the poster since each person has their own level of spending.

Agreed.

> others are greatly disappointed that their system is not working the way they thought."

Including people with $600 controllers. Again, price is not the driving factor.

[SunEagle]

> Our biggest problem is that most Noobs want to purchase cheap MPPT CC's which turn out to really be PWM type or pieces of crap

The solution to that problem is providing accurate information. "The problem is that there are so many false MPPT type CC's it would take many pages to list them all. It is a little easier to just provide out thoughts on a particular CC that someone is looking to purchase."


> For the most part a low cost MPPT may or may not work efficiently with only a 100watt panel.

As with ALL controllers. That is an excellent example of FUD. "I disagree. We aren't instilling fear we are stating a fact that for a very large percentage of CCs that do not work well with a small wattage system. You can disagree but please don't label our posts as FUD."

> You have to do the research first to find something that does.

Agreed, regardless of price.


> So while we may use a broad brush and put down all cheap MPPT type CC's we are really just trying to keep people from wasting their money.

One could just as easily make the argument that telling people to spend 3-4x more to meet the same need is wasting their money. I won't make that argument since I don't know what's best for someone else. "I have never wasted my money by purchasing a quality piece of equipment. Sure I look for the lower or discount price on something before I buy something but saving a few $ usually tends to be wasted on lower quality. What I try to say is that the decision to purchase what they are looking at is up to the poster since each person has their own level of spending.. Some people get by with low quality equipment but others are greatly disappointed that their system is not working the way they thought."

Comments posted above in " "

[secessus]

> Our biggest problem is that most Noobs want to purchase cheap MPPT CC's which turn out to really be PWM type or pieces of crap

The solution to that problem is providing accurate information.


> For the most part a low cost MPPT may or may not work efficiently with only a 100watt panel.

As with ALL controllers. That is an excellent example of FUD.

> You have to do the research first to find something that does.

Agreed, regardless of price.


> So while we may use a broad brush and put down all cheap MPPT type CC's we are really just trying to keep people from wasting their money.

One could just as easily make the argument that telling people to spend 3-4x more to meet the same need is wasting their money. I won't make that argument since I don't know what's best for someone else.

[SunEagle]

Our biggest problem is that most Noobs want to purchase cheap MPPT CC's which turn out to really be PWM type or pieces of crap and just dangerous. For the most part a low cost MPPT may or may not work efficiently with only a 100watt panel. You have to do the research first to find something that does.

Speaking for the Moderators on this Forum, we are not spreading Fear, Uncertainty or Doubt. We are trying to make sure people trying to save money not purchases something that most likely will not work. So while we may use a broad brush and put down all cheap MPPT type CC's we are really just trying to keep people from wasting their money.

[secessus]

> converted to 14V gives 7.14 amps about 1.5A gain and you use a $200 controller to get there.

It seems to me your underlying argument is that small MPPT configs are not worth the gain economically to you. Maybe not, that's up to you. There are other use cases where it might be worth it.


> But since I don't know of any MPPT controllers that would actually work in this configuration,


The only MPPT I know of that wouldn't work in that situation are the Victrons that have unsually high MPPT-initiation voltages (+5v, IIRC). And even then it doesn't have to be Vmp>=Vbatt+5, just panel voltage broadly speaking. Once initiated it only requires +1v.

The Genasun GVB MPPT series has a boost circuit and will charge from as little as 5v input.



> I'll stand by "it's going to run in PWM mode."


There are at least two situations where MPPT controllers are not running at the maximum power point and in my opinion PWM is not a useful description of either case:

* when the MPPT algorithm is not active due to insufficient Vpanel or other requirement (I think this is one you mean here). Victron's +5v requirement, or EpEver's apparent ~10w minimum. I don't observe this outside dawn/dusk so have not studied it carefully, the available power at such times being so minor. My recollection is that when the algo isn't running it's Vpanel == Vbatt with periodic sweeps. Heck, even PWM controllers aren't doing PWM in such situations; it's just a circuit with no pulses to modulate.
* when maximum power is not demanded. You've said elsewhere that "Generally, with MPPT chargers, as the batteries require less power, the charger reverts to PWM mode...". MPPT chargers typically move Vpanel off Vmp to another powerpoint that meets demand (usually toward Voc). . Watch Vpanel move around after Vabs is attained and compare that to your panels' published curve. I have argued elsewhere that calling MPPT controllers PPT controllers would keep people from getting hung up on the maximum part of the name.


> PV panels are generally hot, being in the sun, and that drives their Vmp voltage lower

Right, I am familiar with temp derating. Folks running MPPT in hot ambient temps would do well to shoot for higher Vmp.

The most popular 100w I know of (framed Renogy mono) has a Vmp around 18.9v, if memory serves. That panel would hold 14v+1 until ~98F ambient.



> b) genuine MPPT $200

I see you repeat this mantra often, and take issue with it. ("You can do it right, or you can do it cheap. You now see the results of cheap."). There are small MPPT controllers down to about the $50 mark. Yes, one has to pay attention to get a real one.

A 10A Chinese tracer/epever/epsolar 1210-series controller is about $50 from the mainland, or $60 off Amazon. My 40A 4210BN controller was less than $200.

Are Midnite Solar or Morningstar a better value for me at 3x the cost and for my use case? No. Am I going crap on them whenever they are mentioned just because they don't make sense for me? Nope. I am hoping you will follow suit, if for no other reason than there's a moderator badge on your avatar.


> So convince me how it works in real life for you


In the past I've run MPPT successfully on systems as small as 5A genasun mppt (GV5? back when serial numbers were handwritten) on a 60w panel, and 10A 1210 controller mentioned above on a 100w panel.

Forgive me if I say I think you have an entrenched position and cannot be convinced. I don't want to convince you; I want you to stop spreading FUD.

[Mike90250]

> A MPPT controller is wasted on a single100w panel. There is nothing for it to do except run in PWM mode

Both statements are trivially disprovable.

[game on]

Of course you are right. and I'll do the math ( and assume 100% efficiency, and charging at 14v which I used before, and
assuming the MPPT requires no overhead voltage instead of the typical Vbatt x 130%)

MPPT
100w @ 18Vmp = 5.55a
converted to 14V gives 7.14 amps about 1.5A gain and you use a $200 controller to get there.

But since I don't know of any MPPT controllers that would actually work in this configuration, I'll stand by "it's going to run in PWM mode."

PV panels are generally hot, being in the sun, and that drives their Vmp voltage lower, and less likely to be able to have MPPT action happen.
exceptions - a really cold day that shifts the Vmp point to 20V might help.

And of course the newcomers don't always know there are really 3 kinds of charge controllers
a) PWM $30
b) genuine MPPT $200
c) PWM with a MPPT sticker over the PWM label $50 ( which works till the user gets a reliable meter and takes Vmp vs Vbatt readings and finds out he's been screwed )


So convince me how it works in real life for you. (MPPT with a single 100w 12v panel) . I want to be able to pass honest info along, and if you have something that works, share it.

[secessus]

> A MPPT controller is wasted on a single100w panel. There is nothing for it to do except run in PWM mode

Both statements are trivially disprovable.

[Mike90250]

The 100w panel might take 2 days to recharge that battery. If you have a regular car charger, throw it onto the battery for a day, so the battery does not become damaged from being in a constant low state.

Just about any < $50 entry level PWM controller should work for you. I'd not bother to get less than a 15A controller.

If you only plan on using a LED light and charging some USB gear, you will be OK for a few sunny days. It's hard to be sure what the USB loads are going to be, but the big battery will hold a lot of recharges before it goes flat.