Good MPPT controller advice needed for100Ah 12V lithium battery

[Doug SC]

I know this has been covered in the past, but when I did a search, I could not find MPPT controller. I believe CB posted something on this before the site changed to the new format.

The 100 watt/5.71 amp solar panel is used and given to me when a friend upgraded his RV. It came with a Go Power!  PWM solar controller (same brand as the solar panel) rated for continuous solar current input of 10amps. I seem to remember CB saying to go with an MPPT controller. I am wondering if I should just use this controller or go with an MPPT.

[Charles Brennan]

Doug, I think you may be coming down with "Timm R. Disease":
You tell us PART of what we need to know, but not ALL of it! 
We know it is a 100A/Hr Lithium battery, but what kind of Lithium battery? 

All these new High-Tech batteries have amazing properties, but they all achieve those whiz-bang efficiencies with very, very different, technical requirements.  So I'm reluctant to quote specifics, since there's so many ways to go.
I'll try to (generally!) cover what I can.

1) You are correct to disregard a PWM (Pulse Width Modulation) controller, out of hand.  Those are fine for lead-acid technology, but are like using a jack-hammer to drive in a tack, for Lithium batteries.  PWM chargers pulse varying amounts of current to the battery, by rapidly turning the current on and off for increasing (or decreasing) amounts of time as the battery gets charged.  A dirty little secret, not ballyhooed by the charger industry, is that the solid-state switchers used in PWM controllers are very often electrically-speaking, quite noisy.  (Especially, on the cheaper PWM controllers.)  No problem with a lead-acid battery, but when installed in close proximity to the BMS (Battery Management System) built into your Lithium battery, that PWM electrical noise can interfere with the proper operation of the BMS.

2) MPPT (Maximum Power Point Tracker) chargers are far more efficient than PWM controllers.  Where the PWM's fall down is that they don't have as much range of operation as MPPT controllers. For example, when your battery is nearly at full charge and it's a bright day and your solar array is cranking out the Amps, the PWM has to shed that excess energy as heat, which limits the maximum current it can tolerate.  Plus, we all know that Heat is the Enemy of solid-state technology.  Not a big problem for a 20 or 30 watt solar panel, but a 100 watt panel like you have, will give your average PWM controller fits.  Where the MPPT controllers really shine, is on those days when the sun ISN'T shining so brightly.  MPPT controllers are much more efficient funneling energy to the battery at low solar output ranges and more efficient bleeding off excess energy when it's a bright day or when the battery is nearly at full charge.  It's at the extremes of operation that makes the MPPT controllers worth their (exorbitant!) cost.

BTW, the 5.71A solar output you cite, is a mis-nomer. Using Watt's formula, P=E*I, 100 watts over 12 volts should give us 8.3 Amps, not 5 Amps. The manufacturer of your solar array Go Power specifies the out put of their array as a range of between 5.1 Amps to 10 Amps.  The 5.1 Amps is the short-circuit current output (and not really a useful measurement). Take all that with a liberal grain of salt anyway, as ALL solar power arrays are specified by their manufacturers, as the equivalent of a one minute average of continuous sunlight, at the equator, at high noon.  De-rate that slightly, for every 10º of latitude, north of 0º latitude.

3) The two factors that will most influence your choice of MPPT controller are the maximum output of your solar array and the maximum charge input specifications for your Lithium battery.  Lithium batteries have a "C" rating which is a measure of how fast your battery can either charge, or discharge. 1C is a full discharge or charge in one hour. 2C is a full charge in 30 minutes, .5C is a full charge in 2 hours, etc., etc. This means that using a high C rating battery in a basic power system won't necessarily make it faster or more powerful, but will allow for a more constant power delivery, keep battery temps down and may even increase run times. However, using a low C rating in a high performance power system will actually hinder performance, stress out the battery which will increase battery temps and can reduce run times.
Now, do you see why I wanted far more specificity, than what you provided?   
There's a LOTSA variables, out there! 

4) Unless there is something unusual in your battery's specifications, most of these numbers will be moot.
MPPT controller size is affected by those C numbers, as higher C numbers means that you can charge at higher rates of current.  Instead of your average 8 Amp or 20 Amp battery charger like you're used to for lead-acid technology, you could have MPPT controllers that can pump 50 Amps or 100 Amps at a time, into a depleted Lithium battery.
This is basically moot for your application, since you're unlikely to get more than 8 Amps out of your solar array. So when you start shopping for Lithium battery MPPT controllers, you can ignore most anything rated for much more than 20 Amps.  I would instead, look for bells and whistles like blue-tooth operation and battery monitoring, that can be viewed from your smart phone.

Without knowing more specifics about your particular model and brand and technology type (yes, the industry really IS that fragmented and that modular) in the most general sense I would recommend something similar to an MPPT 100/20 controller.
Here is a typical one:
https://shop.pkys.com/Victron-Energy-SCC110020160R-Smart-Solar-MPPT-10020-Charge-Controller-with-Bluetooth_p_7857.html

Hope this helps,
Charles Brennan

[Doug SC]

Thank you, Charles! I thought I remembered you recommending Victron and had looked at them. I just wasn't sure which one to go with. The battery is a Litime 12.8V LiFePO4 suitable for trolling motors.

link
https://www.amazon.com/Litime-LiFePO4-Protection-Rechargeable-Trolling/dp/B0C8T1FD7M/ref=sr_1_1_sspa?crid=378A1J3WJ1PTJ&dib=eyJ2IjoiMSJ9.V94C60siU1Imlf4vhQvBQwMAvNacoc4rkRwU7fTM1oRxa9Ksn-h1p-YnPqmugwDqBLeuST7e1DpaGMKmhcy3vEeKSjjWyE9cLxgEXIwNbEXRvumuAlKtzsa76KWkKa96Ohdb6FSF17vwYJIiH79aj5U6CWnd0V9HbKJwSjRdg8k3vdWzEhWXrH1y8LrBxRa1z0vqMlCMiys-cwZmyy4Akgxp4TssmTPpKShf6KEB3Js.kD09_z3xieu9EvBmx1BW0_MqGyDZdctE68bBO-OeYU4&dib_tag=se&keywords=litime+12v+100ah+lithium+battery+self-heating+low+temperature&qid=1729301233&sprefix=Litime%2Caps%2C129&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

[Charles Brennan]

Doug, Nothing like a good hard FACT! 
In that case, the Victor MPPT 75/15 would be more than adequate for your needs.

Hope this helps,
Charles Brennan

[Doug SC]

I am looking at using 10-gauge tinned copper wire but see reviews on that being difficult to connect to the controller even through it is advertised for up to 10 gauge. So, I am considering using 12-gauge. What are the advantages or disadvantages of doing this. I am considering using 10-foot lengths of wire for panel to controller and for battery to controller, so I have enough wire to reach most places on my 19' boat.

I was advised by my friend to have a 15amp fuse close to the positive terminal of the battery which I also plan to do.

[Charles Brennan]

Doug, I TOTALLY zoned out    on finding out your maximum current requirements, with everything turned on.  If your total current load exceeds 15 Amps, the MPPT 75/15 will shut it off.  I never asked (for example) if you are going to be running a trolling motor, in additional to your other house loads on your boat.  I intend to get an MPPT 100/20 because I will be using a trolling motor, nav lights and possibly a tiller pilot and expect loads approaching 20 Amps, in some cases.  I was focused on getting an efficient and correct input from the solar array into a specific type of Lithium battery and COMPLETELY discounted the loads AFTER leaving the battery
My apologies.

You need to do an energy audit of your anticipated (and more importantly, possible UN-anticipated!) loads, before you settle on a specific solar charger.

As to your follow-up question regarding wiring:
Allow me to start with the same analogy I used to use, when instructing dealers on installing our electronic equipment.
"You can't suck a milkshake through a cocktail straw."
Which is by way of saying you can't get proper current flow without a sufficient cross-sectional area of copper for the electrons to rush through.

In Ye Olde Analogue Lead-Acid Dayes voltage and current drop was not really a big deal.  In fact, ABYC standards allowed for a 10% voltage drop on non-critical electrical functions and a 3% voltage drop across more critical electrical functions.
You indicated using 10 foot lengths of wiring to the controller and to the battery for the 15 Amp model.
Checking my math, that's 20 feet of wiring.  According to most ABYC wire-sizing tables for 15 Amps at 3% voltage drop you have to have at LEAST #10 gauge wiring.

You cannot view this attachment.

To further rain on your parade:
In reality, current has to go OUT and current has to come BACK, in an electrical circuit.
10 feet out and 10 feet back is actually 20 feet and for your two components we now have 40 feet.
For a 3% drop, now you're talking #6 gauge wire.
For a 10% drop, you are back to #10 gauge wire.

The two options for this are:
A) Reprogram your voltage cutoff and current cutoff points on your charger to accommodate a 10% voltage drop, in lieu of the factory-set 3% drop.
i.e. 12.8VDC - 1.28VDC (10%) = 11.52 VDC before cutoff; as opposed to 12.8VDC - .384VDC (3%) = 12.41VDC before cutoff.

B) Use the right damn'ed gauge of wire.

Those voltage differences didn't really mean anything in the analog days, but to these digital high-tech gadgets those numbers are critical, and the charger will merrily cut off your entire house load when those voltage levels are reached.

Your final concern was about inserting a #10 gauge wire in the connector.
If the specs say you can get a #10 gauge wire in, then you have to be patient and/or careful.  Just because ham-handed DIYers (like us!!)  are having problems doesn't mean it can't be done.  I worked around Engineering types for decades and when they publish a spec, they MEAN what they publish.

3 Options:
1) To test whether they were right, or not, try to get hold of a 0.1935" drill bit (strangely enough, called a #10 gauge drill bit) and see if that fits in the wiring connector.  If it does, the Engineers were right.  The most common mistake noobs make, is trying to twist the stranded conductors.  This will increase the over-all diameter, not decrease it, and you may have problems.  Keep the stranded wires straight and parallel and carefully insert the wire into the connector.

2) If the connector was so tight the drill bit didn't quite fit and you're feeling brave enough to risk your warranty,    put the #10 drill bit into a drill, then enlarge the holes slightly.

3) If you're both klutzy and totally chicken about your warranty, get a #10 fork lug like this:
You cannot view this attachment.
Insert the wire and crimp as normal.
Cut off those two right-angle ends on the end of the connector.
Then using a stout pair of pliers, fold the fork in half, so that each fork is laying over the other and doubled up. One way to do this, is to use two pairs of pliers, one on each fork and bend them toward each other and when mostly together, complete the bend with a single pair of pliers.
Then insert the folded over fork into the connector.  (This is why we had you cut off the right-angled ends.)

Sorry for any confusion and I hope this clarifies,
Charles Brennan

[Doug SC]

No apology needed. I am not good with an understanding of electrical systems and am very grateful for the time you have taken to inform me of what I don't know. This lack of knowledge on my part is the root of having given you incomplete information.

I have a 55 lb. trust trolling motor that will be part of the mix. I don't have it on hand as it is on loan at the moment. Running and anchor lights, cabin light, depth sounder, and an on-board VHF are the other electrons on my Potter.

For the Scamp I have a complete set of Navisafe running lights (gift from my son) that will use AAA rechargeable batteries. I also have a handheld GPS that uses AA rechargeables. For the AAA and AA batteries I have an AAA and AA battery charger that can work off of AC or DC. I have Luci lights that are solar charged and can be charged by USB. I have a handheld VHF that I use when racing and kayaking that unfortunately requires AC for recharging.

I now plan to use 10 AGW wires of shorter lengths, and the recommended Victron 100/20 controller. Below is a list of my now intended purchases and items on hand for setting up the Potter 19.

Litime 12.8V 100Ah battery recently purchased. A hand-me-down used Go Power 100 watt flexible monocrystalline solar panel with 22" pigtail.

I intend to tie that to the controller with these 6 feet of wiring found on Amazon .

https://www.amazon.com/dp/B083DQ52FY/?coliid=I3I9YYI0ZPX8GA&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it


From the controller to the Battery these two wiring bundles.

This one out from the controller is 3.28 feet long.

 https://www.amazon.com/dp/B09PD99VPQ/?coliid=IWQ07TV82HTUD&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

This one out from the battery is 2 feet long.

https://www.amazon.com/dp/B0BD771G7P/?coliid=IR1K1T3J3X7LS&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

A question about the wire supplying power to the electronics on the boat. Do they come from the battery as they do now or do I wire the controller to the control panel for the onboard electronic switches?

I have been looking at portable power stations for camping from the Scamp and this one from Bluetti is the one I am considering. It can be hooked up to solar panels and has an internal MPPT. 120AC, DC, and USB outlets.

https://www.amazon.com/dp/B0CLG6FYLQ/?coliid=IEEMASJKMFT3O&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

I would really appreciate your assessment of these choices.   

[Spot]

I would recommend having a fuse or breaker on both the inputs (charge controller, alternator. shore power) and outputs of the battery. On my boat the solar is fused and the battery to main circuit panel is a breaker, thought it would be better not to loose all power for the want of a fuse.

I would also recommend the boat having its own charge controller and then the power station's internal one can be the 'suspenders' of 'belt and suspenders'.

I had been using the worst looking used lawn tractor battery and a 50w panel and a 10A PWM contoller since 2019 on the Southwind 21, leaving the battery in the boat and having the security lights come one one hour each night to remind me the system is still working.  I recently upgraded to a bigger FLA battery in case I wanted to run the fish finder/ GPS several hours a day and have enough left for lights and fans and charging 2 smart phones (mine and crew) in the evening. I may baby the newer battery a bit more.

And now we return to our regularly-scheduled Brennan, er, uhm, I mean program...

[Charles Brennan]

Doug, On the TSBB, we got OPINIONS and we're not afraid to use them!! 
Assessments in order, are:

https://www.amazon.com/dp/B083DQ52FY/?coliid=I3I9YYI0ZPX8GA&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it
In and of itself is fine, but a little bit of overkill.
(This from the guy who believes: A Thing Worth Engineering Is A Thing Worth OVER-Engineering. ) 
Don't forget, you'll probably NEVER get much more than 8 Amps out of your solar array, so a #14 gauge wire and connector would be more than ample for your application. 

 https://www.amazon.com/dp/B09PD99VPQ/?coliid=IWQ07TV82HTUD&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it
No problems there; exactly the right thing to use.

https://www.amazon.com/dp/B0BD771G7P/?coliid=IR1K1T3J3X7LS&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it
Ditto.

Your question:
"A question about the wire supplying power to the electronics on the boat. Do they come from the battery as they do now or do I wire the controller to the control panel for the onboard electronic switches?"
You ABSOLUTELY, wire from the LOAD terminals on the controller to your boat's electrical system and DO NOT connect the house wiring, directly to the battery.  The power curve of a sudden current surge, can mimic the current curve of a short circuit and cause the controller to make mistakes.

Consider the following comedy-of-errors feedback loop:
1) You have your battery and boat wiring system tied together.
2) You switch on your 55lb thrust trolling motor, you know: the one that draws 50+ Amps?   
3) The circuitry in your MPPT controller sees the sudden current surge/draw compares it to the load current (none, 'cuz nothing's hooked to the load terminals!) and it thinks:
"Omigod! A Short Circuit!!"    And promptly disconnects. "Whew! I saved it!" 
4) This fakes out the BMS (Battery Management System) circuitry in the Lithium battery, which momentarily resets, killing power to the trolling motor.
5) The sudden thrust on the motor stops and the boat starts to coast.
6) Everything having reset by now, the motor again turns on and draws half your battery's Ampacity, like before.
7) Go back to Step #2 and repeat, until the BMS circuitry overheats and shuts down completely, requiring a factory reset.

Go read up in your battery manual about performing a factory reset on a catatonic Lithium battery, whose BMS is on strike.
The best way to visualize BMS circuitry, is to compare it to the worst, most officious, DMV bureaucrat, you ever had to deal with and go from there. 

The whole idea behind the MPPT controller, is that it mitigates and protects your battery and your boat electronics, from actual short circuits and surges.
That's why I was concerned that you match the loads properly on your MPPT controller choice.

"But Charles," you say. "That couldn't really happen, could it?" 
Try it. 

And a Story:
My Son-in-Law had a buddy upgrading the electrical system on his Bass boat, and his trolling motor kept surging strangely. SIL (an electrician) came over with his ammeter to help out his buddy and hooked on to the power lead and couldn't find anything amiss, except for no current.  This was strange, since the trolling motor kept surging.  Checked for shorts or mis-wiring and couldn't see anything on his ammeter that was out of the ordinary.  So why no current?!? 
Did what my kids have done, half my life: 1 800) CALL-DAD
Told him sure, bring it over and we'll look at it.
When they got to the house, I re-checked their wiring and watched my SIL test the wiring with his ammeter.
Looked good to me, too, except for the possessed trolling motor. 
Maybe we need a Priest, instead of a Technician. 
Hmmm . . . . Maybe that industrial digital ammeter circuitry just can't keep up with the MPPT controller switching speeds.
I dug out a big honkin' shunt resistor, from when I used to test power supplies and put my oscilloscope on each side of the shunt resistor and had them connect the battery and saw a flicker on the scope.
OK, speed up the time-base switch! 
Wow!    The switchers on PWM controllers work in the milliseconds, but the MPPT controller was switching in the micro-seconds.  When I checked the battery directly, I discovered the BMS circuitry was switching in the tens of nano-seconds.     
OK, now we know WHAT is going on; now, WHY?!? 
Checked the peak current draw across the shunt: 53 Amps, on a 55lb thrust trolling motor, before it kicked out in a micro-second, or two.
Hmmm . . . . "You got any way to see the factory settings on this thing?" 
Bass Buddy promptly whipped out his smart phone and loaded the battery blue tooth app.
About 4 menu layers down, I discovered that SOMEBODY (not him, he swore, because he NEVER touched ANY of the settings!),    but clearly, SOMEBODY had changed the max cut-off load, by a factor of TEN!! By moving a value, a  whole decimal point over, on one of the menus!
Told him: "Yeah. God doesn't repeal the Laws of Physics for anybody." 
Reset the errant menu choice and the gear worked flawlessly.

To review:
1) Solar wires go to PV input.
2) Battery wires go to Battery input.
3) All stuff on the boat goes to the LOAD input.
Mix and match any of those and you too, can end up scratching your head, all winter!
The MPPT controller WILL save you from yourself, but it never promised it wouldn't drive you crazy, doing so!!   

And your final query:
https://www.amazon.com/dp/B0CLG6FYLQ/?coliid=IEEMASJKMFT3O&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

Confuses me. 
Is the electrical system we have been discussing on a different boat, or is it on the SCAMP?
If it is for the SCAMP, then you already have most of that on board; you're just missing two components:

https://bluemarine.com/products/victron-energy-phoenix-inverter-v-e-direct?variant=49038620819752&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gad_source=1&gclid=CjwKCAjw1NK4BhAwEiwAVUHPUEQbU3JYG260XFVv6KIxH-0w-i_tRbOcdcGdhf4MZnmKyAETaMB0vBoCt2wQAvD_BwE

and: 

https://www.amazon.com/Outlet-Charger-Charge3-0-Android-Suitable/dp/B0BX6F1ZP9/ref=asc_df_B0BX6F1ZP9/?tag=hyprod-20&linkCode=df0&hvadid=693712892536&hvpos=&hvnetw=g&hvrand=8189726722553101799&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1015134&hvtargid=pla-2198052683439&mcid=02f488f1e0723737b4318fa15a62063a&th=1

$100 bucks, versus nearly $500 bucks for the same thing in one box, is OK if you want/need that kind of redundancy, but it sounds kind of like overkill, to me, Dude.

Hope this helps,
Charles Brennan

[Doug SC]

Thanks again for the education.
 
The system we are talking about is for the Potter 19.

The power station is for camping with the Scamp. I thought it would be a multi-purpose thing to have around as well. I have also considered smaller units like these. Since being a sailor, I am inherently cheap.

https://www.amazon.com/dp/B0CMQYK2KW/?coliid=I2GCF57UDO0TW&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

https://www.amazon.com/dp/B0CZ6P84WH/?coliid=I189P8QM7U13U9&colid=19ARYS9922JV9&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

[Charles Brennan]

Doug, Finally out of the realm of numbers and physics; which is to say: Out of my wheelhouse! 
Since I have NO possible idea of how many watt/hours you suck up on your average camping trip, there's no way I can make a recommendation that carries any weight, or sense of rationality.

In terms of bang for the buck, dividing watt/hours by dollars gives us:
2.02 W/Hr per $ for the big one.
1.60 W/Hr per $ for the middle one.
1.43 W/Hr per $ for the small one.

Figure out how many watts you consume on a camping trip, and go from there.
You might get in the ballpark, by using the blue tooth app on your phone to tally power consumption on your Potter, on any given weekend.  Not much more than a horseback guess, but perhaps better, than wetting your finger and holding it up to the wind.

That's all *I* got!! 
Charles Brennan

[Timm R Oday25]

Excuse me , Charles why not recommend a 10 gauge pin connector ?
I use them at work from 28 to 6 Guage . I've not yet had a problem

[Charles Brennan]

Timm, You ask a very good question; I have a few different reasons, which (In no particular order) are:

1) I TOTALLY FORGOT! 
2) Our local hardware and auto parts stores universally NEVER carry them and I simply assumed Doug would have an equally hard time finding them.
3) Because I am so used to not having the part I need when I need it, I have made it a habit of using the far more common and readily available fork lugs and modifying them.
4) The final and admittedly pedantic reason, is for the increased surface area of the doubled-up forks to handle increased current loads, compared to the pin connector.

But having spent this entire thread, trying to ensure the right parts for the right application are being considered, I would be remiss in not correcting my own bad habits.
And since Doug is apparently getting everything on-line from Amazon anyway, another few bucks for hardware, should be a no-brainer.

DOUG: Here ya go! 
https://www.amazon.com/12-10-Ga-Heat-Shrink-Pin-Terminals/dp/B00NVAD24M

Use THIS: 
You cannot view this attachment.

NOT THIS: 
You cannot view this attachment.

Sorry for any confusion,
Charles Brennan

[Timm R Oday25]

Charles ,good on you .
I'm in the other boat . I have access to pretty much anything I could ever want component wise .
Digikey ,Newark are only a click away .
Amphenol and Duestch are my preferred connectors . The crimpers are stupid priced . The connectors themselves are free for me .

[Doug SC]

I was already considering the yellow pins as I saw a reviewer had recommended using them. do I need a special crimper is the question I have.

Spent the day fly fishing for trout on the Chattooga River. Only caught one rainbow but the weather went from 40s to 70, bluebird day with leaves changing color water temp got up to about 52 in the foothills of SC. "All most Heaven"!