MPPT controller, BMS and inverter recommendations

I am putting together a basic system for a Sprinter van conversion. I recently obtained two used 305w solar panels and two like-new 100ah deep cycle lead batteries.
For now, I am looking to use both batteries and probably one panel mounted to the top of the van, but want the option of adding the second panel either permanent on the roof at some point or just carry it along and plug into the system when parked. So, things would have to work off one or two panels. Also, I intend on upgrading to lifepo4 in the future and I will build my own batteries from cells. However, I have a trip planned soon and would not be able to get the cells, and build the battery in time, so I got the gently used deep cycle marine/RV wet lead batteries as a temporary solution. I will be running a regular 110v mini fridge, and maybe a microwave or coffee maker for 10-15 minutes a day. Not too heavy a load.

From what I have read, I should get an MPPT controller and a pure sine wave inverter. I have no clue about what kind of BMS to get. However, these components would need to be able to run off one or two solar panels, handle wet lead acid (200ah total) or lifepo4 (intend on doing 280ah), and be able to run some basic 110v appliances.

What brand and size of controller should I get? I am looking for reliable but not necessarily top of the line. I know Victron is very good but also expensive. I am under the impression that EPEVER is a decent brand maybe? Any thoughts on other brands? Renogy?

Same questions on brand and size for BMS and inverter. I am thinking 1000-1500w inverter should do it. I am clueless on the BMS to use.

Thanks
Nik

These are the batteries and the specs on the solar panels.

I would get a 150v mppt if you want to use those panels in series, otherwise any 75-100v unit of your choice. You can't really go wrong with Epever or Victron. I'm yet to hear a good thing about a renology branded product.

You don't need a BMS on those batteries. They look like marine batteries which as a rule of thumb should only be discharged by 20% max. Not really ideal for cyclic applications.

You don't need a BMS for lead acid. Just don't discharge below 50% SOC.
Microwave requires a 1500W inverter minimum.
Two panels in series are below 100V (Voc), so a Epever with 100V / 10a would be fine.

Thanks for the replies. Sounds like Epever is a decent quality unit that won't break the bank.
As far as voltage and amperage, I was confused as to which numbers from the panels to use. But it seems like you should base things on Voc, not Vmpp. In series we would have approx 90v at approx 9A. In parallel would have approx 45v at approx 18A. So for these panels it would probably be best to do in series with two of them and a 10A unit would be fine regardless of the battery setup? As in...if I go 280ah lifepo4 in the future then a 100v, 10A Epever would still be fine?

Which Epever would you recommend? The Tracer3210AN or Tracer2206AN? The first is a 30A 100v and the second is a 20A 60v. It seems the lower amp models will not handle higher voltage. I am leaning towards the 30A model just to be safe. I guess the 20A model could still be used if I put the panels in parallel, but that would be pushing the limit on that controller.

Sounds like BMS is only needed for lifepo4, so I will worry about that later when I go with that chemistry.

Any suggestions on brand for a pure sine wave inverter? Again, reasonably priced but solid?
I am not living in this van or anything...just some weekends here and there.

Thanks

So apparently there is a 2206 and a 2210 model that can handle 50 and 100 volts respectively. I went with the 3210 just to be safe because it was only another $17.

Any pure sine inverter recommendations? I know Victron makes nice stuff. I also see a brand called AIMS that appears high end. Both of those brands are expensive. Is there a brand of inverter like Epever that is decent quality without a huge price tag?

If you want larger batteries someday, go with the larger amp charger. Maybe even larger than 30a that you mentioned. Have a 40 amp 100v and a 60a 150v Tracer. The 40a is still fairly small but the 60a is much larger....if space is a concern. (edit) you can run them in parallel on the same battery bank.

I understand Giandel brand inverters are pretty solid. I have purchased 1500w 12v and 1200w 24v recently but I have not really used them yet.

The Voc needs to stay below the max PV input of the charger, to protect the charger from being damaged by a voltage that it was never designed to tolerate.

I already ordered the 30A. But I can try to cancel it and replace it. For two of those 305w panels and 280ah of lifepo4, do you really think I need the 40A? Any body with feedback would be appreciated because I will need to change the order or cancel it quickly. Thanks

Nikg736 said:

I already ordered the 30A. But I can try to cancel it and replace it. For two of those 305w panels and 280ah of lifepo4, do you really think I need the 40A? Any body with feedback would be appreciated because I will need to change the order or cancel it quickly. Thanks

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I didn't state larger amps were better based on what equipment you have now but in general (someday you will be more hungry). Also, you could add a second charger later if that was a better solution.

I would rather just size it up in anticipation of the future upgrade, that way I dont have to buy more later. It seems more efficient to just buy one controller and have it under-worked now and properly loaded later.

And please guide me here...I read a bit more about controller sizing and it appears to be more a function of the solar panel array and battery bank voltage than the battery bank capacity. For example, I have seen on several sites to take the total output of the panels and divide by battery bank voltage. For 12v some say use 14.4v as the voltage...not sure about that?
However, using this method we get 610w/12v = 50A. Or using 14.4 we get 610w/14.4 = 42.36A
The guy I bought the used panels from said he tested them and they were probably 5-10% loss on output, so I am thinking the actual output is probably 550-580w. But even 550/12 = 45.8A.

All of the above leads me to believe that I should have at least a 40A controller regardless of the battery bank (unless 24v bank). I know mppt controllers can throttle things down, but to get the full use out of a unit with the system I described, I am thinking maybe I even need a 60A? I'm just not sure why I was given the advice that a 100v, 10A controller would be fine?

Looking at the 50A and 60A controllers from Epever, they are rated for 150v and we get a step up in relative price. It's about $100 for the 30A 100v model and $125 for the 40A 100v model. But the 50A 150v is $220 and the 60A 150v is $240.
Seeing as I am not going to get into that 150v range, would it just be better for me to order two of the 30A models and chain them together? Are Epever capable of being put in parallel?

Nikg736 said:

I would rather just size it up in anticipation of the future upgrade, that way I dont have to buy more later. It seems more efficient to just buy one controller and have it under-worked now and properly loaded later.

And please guide me here...I read a bit more about controller sizing and it appears to be more a function of the solar panel array and battery bank voltage than the battery bank capacity. For example, I have seen on several sites to take the total output of the panels and divide by battery bank voltage. For 12v some say use 14.4v as the voltage...not sure about that?
However, using this method we get 610w/12v = 50A. Or using 14.4 we get 610w/14.4 = 42.36A
The guy I bought the used panels from said he tested them and they were probably 5-10% loss on output, so I am thinking the actual output is probably 550-580w. But even 550/12 = 45.8A.

All of the above leads me to believe that I should have at least a 40A controller regardless of the battery bank (unless 24v bank). I know mppt controllers can throttle things down, but to get the full use out of a unit with the system I described, I am thinking maybe I even need a 60A? I'm just not sure why I was given the advice that a 100v, 10A controller would be fine?

Click to expand...

You're on the right track. You need a charge controller that can charge at the right number of amps which in your case is 50A (actually slightly less given that you will charge at higher than 12V, but 50A gives you a little head room). If you get a 10 amp charge controller you'll be throwing away a lot of solar power.

So the MPPT charge controller needs to be rated for both the Volts and Amps that your solar panel can produce (don't go over the Volt rating, if you go over amp rating the excess power will just be wasted), and it has to be able to produce enough charging amps to fully use the solar power coming into it.

In your case the MPPT charger needs to accept 90V minimum (VoC x2 but better to leave a little headroom) and 10 Amp input and charge at 50 amps assuming a 12V battery bank (610W/13.6V notional bulk charge voltage gives you about 45 amps required).

OK, so now I am thinking just get two of the 30A models and put them in parallel. When running one panel, just use one. With two panels, run two controllers. One panel is about 45v and two in series would be about 90v, so the 100v ratings should be perfectly adequate leaving about 10% headroom. And at 20-25A for one (40-50 for two), it would seem each of these controllers would run in their "sweet spot" for efficiency. Not sure where I read it (and not sure if it is true), but I had seen that running controllers at about 75% of their max rated capacity is where they run most efficiently.

So...does two of the 30A models make sense? That would be cheaper than a single 50A model, plenty adequate for the voltage, plenty adequate for amps, flexible in that I could run one controller for one panel and two for two panels, and also if one controller crapped out on me, I could theoretically run the system off of one controller and one panel (or two panels in "limp mode" because the controller would limit the output and some solar charging energy would be wasted)

Please advise because I am about to contact the seller again and say to make my order two of the 30A models.

Thanks

Nikg736 said:

I would rather just size it up in anticipation of the future upgrade, that way I dont have to buy more later. It seems more efficient to just buy one controller and have it under-worked now and properly loaded later.

And please guide me here...I read a bit more about controller sizing and it appears to be more a function of the solar panel array and battery bank voltage than the battery bank capacity. For example, I have seen on several sites to take the total output of the panels and divide by battery bank voltage. For 12v some say use 14.4v as the voltage...not sure about that?
However, using this method we get 610w/12v = 50A. Or using 14.4 we get 610w/14.4 = 42.36A
The guy I bought the used panels from said he tested them and they were probably 5-10% loss on output, so I am thinking the actual output is probably 550-580w. But even 550/12 = 45.8A.

All of the above leads me to believe that I should have at least a 40A controller regardless of the battery bank (unless 24v bank). I know mppt controllers can throttle things down, but to get the full use out of a unit with the system I described, I am thinking maybe I even need a 60A? I'm just not sure why I was given the advice that a 100v, 10A controller would be fine?

Click to expand...

It sounds like we are on about the same level of experience with solar. I am faced with a similar delima. Ive decided I will probably go 24 volt.

Snubber -- I currently have two 12v batteries, so yes going 24v is actually possible for me right now. But with my future upgrades in mind, I would have to go with 24v of lifepo4 as well, and that would get much more expensive than I want or need. It wouldn't really be a problem if there were inverters that could run on 12v or 24v, but from what I have found you have to pick one or the other. Plus, I will use this battery system to run a few 12vdc items like some LED lighting, therefore I will probably just stick with all 12v. If you don't have any of these issues and considerations, then 24v is probably better. Higher voltage is usually more efficient and does not require as large wiring.

Unless somebody tells me different, I am just going to run with the idea of getting two of the 30A models and assume they can be put in parallel to suit my needs.

Nikg736 said:

Snubber -- I currently have two 12v batteries, so yes going 24v is actually possible for me right now. But with my future upgrades in mind, I would have to go with 24v of lifepo4 as well, and that would get much more expensive than I want or need. It wouldn't really be a problem if there were inverters that could run on 12v or 24v, but from what I have found you have to pick one or the other. Plus, I will use this battery system to run a few 12vdc items like some LED lighting, therefore I will probably just stick with all 12v. If you don't have any of these issues and considerations, then 24v is probably better. Higher voltage is usually more efficient and does not require as large wiring.

Unless somebody tells me different, I am just going to run with the idea of getting two of the 30A models and assume they can be put in parallel to suit my needs.

Click to expand...

If you read my posts in general discussion ( I've only been a member for a couple days ) I think our set-up needs are "similar ". I'm learning and on a budget as well. I plan to use a 24v to 12v step down for my 12v needs.

Well...I contacted the seller on eBay to cancel my original order for one unit and get two of the 30A units instead. Hope I made the right decision.

Snubber - I havent read your posts, but I can. Are you doing a van system?

Nikg736 said:

Well...I contacted the seller on eBay to cancel my original order for one unit and get two of the 30A units instead. Hope I made the right decision.

Snubber - I havent read your posts, but I can. Are you doing a van system?

Click to expand...

Nikg736 said:

Well...I contacted the seller on eBay to cancel my original order for one unit and get two of the 30A units instead. Hope I made the right decision.

Snubber - I havent read your posts, but I can. Are you doing a van system?

Click to expand...

No , it's a shed. Trying to cool it in summer.