I need more power Scotty!

good point. For a trimetric PWM controller, we can wire in parallel if the voltages are the same. POWER of the panel, rated in WATTS is irrelevant.
 
Another long post folks. Thanks for your patience with me as I work through all the options to power solution for our campers. This post focuses on how to choose between the Trimetric PWM controller and the Tracer A MPPT controller.

Here is a great site for planning solar installs. This is the wiring page - http://www.thesolarplanner.com/steps_page9.html

Previous thread on where/how to place your charge controller:
http://www.wanderthewest.com/forum/topic/12903-solar-controller-placement/

Great site referenced in that thread on all things power related from a marine/rv perspective
RV / Marine Battery Charging - Solar & Shore Power Combined!

Post 3 in this thread links to a bunch of info on wire sizes
Is there a maximum length of wire that can be ran with a Solar Panel? - Solar Panels - Solar Panels Forum

Great info on the Victron Energy website:
GREAT paper on PWM vs MPPT - LINK
Whitepapers - LINK
Tech info on battery cables and a great book on the life and times of the lead acid battery - LINK
Real life RV solar system test on Trimetric system by a guy who is a machinist extraordinaire - LINK
His solar install (280W, Trimetric, dual Optima Platinum group31 batteries 210 AH) is really good too - LINK
Positive review of Trimetric - LINK
Video positive review of Trimetric - LINK


Now, on to today’s conundrum, How to choose between PWM and MPPT charge controllers, specifically the Trimetric SC2030 and the Tracer A Series. Both are used by folks on the forum. I’ve mentioned both in this thread. I am close to purchasing and need to make a decision. Here are my thoughts:

MPPT advantages that matter to us are:
- No need to rewire the existing 10g wire going to the roof
- No need for anything besides the usual 10g solar cables with MC4 connectors on long runs to portable panels
- Uses higher voltage/power panels that may be less expensive to purchase

PWM advantages that matter to us are:
- Usually less expensive than MPPT controllers
- Can mix panel types more readily than MPPT controllers can

MPPT disadvantages that matter to us are:
- Should not mix panels at all
- Would need two controllers for sure if mixing 24v panels on roof with lower power (*typically 12v) portable panel

PWM disadvantages that matter to us are:
- As the “need” for more power happens, we should really rewire our campers
- A long external cable will need to be home made, and HUGE to use a panel 50’ or more from the camper

Now, as the specific two controllers I am considering, here are the pros & cons:
- The cost factor is actually reversed! The Tracer A and MT50 combo is about the same price as just the TM2030 alone
- Tracer A’s charging algorithm is not as clever as the one in the Trimetric (see more in post #xxx above)
- Wiring costs are lower with the MPPT controller
- Less hassle running smaller gauge wire and no need to re-run cable with the Tracer A
- North American vs Chinese source... is that relevant?
- The Trimetric is actually better than some MPPT controllers... it is very smart for a PWM controller - LINK
o Bogart admits freely in C1 of this FAQ that MPPT is BETTER than PWM if you are using 24V panels
- SolarBob LOVES the SC2030. And would use the TM2030 for metering MPPT controllers too. - LINK
- The Tracer A uses an internal shunt, so less parts cost and simpler wiring
- The Trimetric system uses an external shunt, which means it can monitor ALL charging sources and tune the solar charging using that info. Much better if your alternator is also involved in charging!

So, the crunch factors for me are:
- Trimetric is smarter
- Tracer A is cheaper and less hassle for wiring in
- Will I be using 24v panels?
- But which will charge my batteries better? And give me longer battery life?

If using 24 panels, the choice is clear – MPPT and Tracer A – by Bogarts own admission. Why? As post #7 here says:
- A PWM controller wastes the voltage between the panels Vmp and the battery voltage. So if the Vmp of the panel is 18v and your battery is charging at 14v... The PWM controller is wasting almost 30% of the panels output.

How can I tell which panels I have or should use?
- If your panel is more than 140 watts or has more than 36 cells, then this would usually be a “high voltage” panel
- The higher cell count PV modules are cheaper per watt then the lower cell count modules - ... 12vdc modules (with 36 cells) often cost twice as much as they are being produced in lower quantities

I was thinking about the charging algorithms, and a post by xxxx got me pondering how often we actually need to use any of the smarts in these controllers. He stated in a PM to me that even after a full day of charging he sees only 93-95% of full charge. By noon he at 90%. That’s past the bulk stage, but just barely. He would be in Absorb stage only, not float. So the smarts about when to go into float stage are not applicable. This sounds like it would be normal for most FWC users, as we unlikely to have enough solar on our rigs to fully recharge daily.

IF we have enough solar power to fully charge then the advantage is to the smarter controller, the Trimetric. See this thread, the critical point which I will quote here too:
- Finish charging (delayed boost) is different. It is an algorithm designed to limit current to the battery to no more than C/10 to prevent excessive water use and heating of the battery. And at the same time provide a high voltage finish stage that fully desulfates the negative plates. It is now almost the industry standard recommend charge profile (Trojan, US Battery, Surrette, and all industrial forklift/floor maintenance, locomotive and marine batteries). Industrial grid-powered forklift/floor maintenance and marine chargers have used it for years (IUIa with no float). Currently there are only two RE chargers that I know of that can do it - the XW from Schneider and the SC-2030 from Bogart. Of the two, only the Bogart SC-2030 does it correctly. (emphasis added)

As I understand it, if we are NOT fully charging:
- The Trimetric will:
o Bulk charge at whatever the panels will put out until the batteries reach a voltage you can set called P1 or Bulk Volts. This is about 85% of full charge
o Then will absorb charge until it gets really hard to push current into the batteries. The current value can be set in P2. This is what most controllers (3 phase) would call “fully charged”, and would normally go into float mode. Most of us are not likely to get to this stage.
o The Trimetric goes into the fancy “finish absorb” mode that apparently only the SC-2030 does correctly – almost all of us are not going to see this unless parked for days in the sun without a draw. However, it WILL keep your batteries very happy between camping trips!
o After an overnight draw, the Trimetric will go back into bulk mode, and repeat.
o See page 15 of Bogart Engineering instruction PDF - Here
- The Tracer A will:
o Bulk charge at whatever the panels will put out until the batteries reach the constant voltage setpoint, much like the P1 for the Trimetric
o According to the Tracer A manual, p 5 Section :cool: when it the controller goes into Constant Charging mode (Absorb) this controller is no longer working in MPPT mode. That’s somewhat disconcerting. Why not? It will stay in this mode for a maximum of three hours, after which it goes into float mode, whether or not the batteries are ready for it. Using xxxx’s case for example, by 2 pm the charger is going into float mode. Xxxx’s battreries where not even at 95% when the sun went down.
o Assuming the sun goes down at 7 and effective charging is possible until 5, that we are missing out on 3 hours of charging time. So even if you have enough solar to fully charge the batteries, the Tracer A won’t even try to get there.
o EPsolar manual here - LINK


Tough decision.
 
Vic,
You are a serious researcher.
You've posted some great info and links here.

I went with the MPPT controller because of my 24 volt panels and love the setup.

But for the many reasons you listed, the combo controller monitor of the trimetric is hard to beat.
If I did not have 24 volt panels, I would have made that choice.

Maybe Bogart will develop a model with MPPT someday too?
 
I'll just add in my two cents on batteries. We need a true deep cycle battery for our purposes. Hybrids just don't cut it. I've tried the Optimas and the Sears Platinums in my camper and it was all to easy to destroy them. I have the Optimas in my Jeep and the Sears Platinums in my truck and they work well, as a starting battery, not as a deep cycle. Doesn't matter if its AGM or FLA or whatever just make sure its a real deep cycle battery.
 
Right you are DavidO.
DrJ, I fired off a question to Bogart about their plans for MPPT. Their response time is pretty good, so we’ll have more info about that shortly.
Craig333, very true. Deep cycle “traction” batteries specifically designed for Renewable Energy is what we need.

Now, as I may need to change the wiring in the roof, I did some more “serious research”. ;-) And found some great pictures that I can use as a how to:

Rewiring the roof –
http://www.wanderthewest.com/forum/topic/9972-renovating-sk%C3%B6ldpaddan-%E2%80%93-1977-grandby-interior-build/
http://www.wanderthewest.com/forum/topic/7978-wiring-a-fwc-or-atc-for-a-solar-panel-roof-mount/?hl=%2Bwire+%2Bsolar+%2Bpanel
http://www.wanderthewest.com/forum/topic/12690-hawk-solar-upgrade/

I also dug up some websites that have more basic info on Charge Controllers and solar terminology
https://www.solar-electric.com/solar-charge-controller-basics.html/
https://www.victronenergy.com/blog/2014/07/21/which-solar-charge-controller-pwm-or-mppt/
http://www.wholesalesolar.com/solar-information/charge-controller-article

AND I found a somewhat heated discussion about whether or not we even need to bother with thicker wire when using PWM controllers
http://www.wanderthewest.com/forum/topic/10391-running-heavier-wire-for-solar-panels/page-7

Member Pods8 really got me thinking (is he still around?), and he may have a good point about the gauge of the wire not being that important with PWM controllers.

If they do operate as he suggests, then as long as the output of the panel – voltage drop => vBatt +.5v then you will get charging happening, and there is no real benefit to upgrading the existing wiring. That is not what I thought before. Seems not everyone on the conversation agreed with him. Any thoughts on this?

In English, if your panel is 18.31v like the 165w panel I was considering, and the max current is 16.4 A (two panels in parallel), then voltage drop across the 12g wire in my 2005 Hawk over 20’ (one way) = 3.6% and the critical number is the voltage remaining, which is 17.65V. More than enough to be .5V over any battery we are likely to be charging. Wow. So, no real need to rewire the roof. Fascinating.

Now, for the long high current run from the alternator to the camper batteries, the voltage drop is still critical, so the stuff I figured out before is still relevant.
 
Vic Harder said:
In English, if your panel is 18.31v like the 165w panel I was considering, and the max current is 16.4 A (two panels in parallel), then voltage drop across the 12g wire in my 2005 Hawk over 20’ (one way) = 3.6% and the critical number is the voltage remaining, which is 17.65V. More than enough to be .5V over any battery we are likely to be charging. Wow. So, no real need to rewire the roof. Fascinating.
Click to expand...
Using Circuit Wizard, http://circuitwizard.bluesea.com/, and plugging in your numbers (12v,16.4a, 40' conductor) from above your wire size should be AWG 6 if going for 3% voltage drop.
Cheers.
 
Captm said:
Using Circuit Wizard, http://circuitwizard.bluesea.com/, and plugging in your numbers (12v,16.4a, 40' conductor) from above your wire size should be AWG 6 if going for 3% voltage drop.
Cheers.
Click to expand...
Yes, I get that, and before I was planning on a 1% drop! The "new" bit of info is that it appears as though a PWM type of controller won't need that high a voltage anyway. I'd appreciate insight on that bit of news. Seems counter intuitive to me!
 
Coming late to this party - I was out an an extended trip when this thread started, and I started playing catch-up last night. Great thread, Vic! I'm determined to figure out the charging system on my camper, and all the info here is very helpful. I particularly like Vic's methodical investigation, with the links to supporting info.

I've been working slowly through the first post, but jumped ahead to see what I was missing, and saw the post with the link to the discussion about wire size and PWM controllers. That was an interesting exchange- I could feel the tension as the discussion escalated. But Pods8's reasoning that increasing wire size to a solar panel might be needless if you use a PWM controller makes sense to me.

My understanding is that a pulse width modulation controller takes an input dc voltage and effectively switches it on and off many times a second, and then sends the resulting pulse train through a resistor-capacitor circuit to smooth it out and average the pulses. If the input voltage is 17V, the output voltage will be 8.5V if the pulse width duty cycle (the percentage of time the "switch" is on) is 50%, and it will be 5.1V if the duty cycle is 30%. So if the input voltage is 17V and and the controller needs to output 14.4V to charge the battery, it will adjust the duty cycle to 14.4/17 = 85%.

I'm not sure what happens when the "switch" is off, but I guess that the controller needs to dump the current still coming in due to inductance and the relatively high current (I think of inductance as the inertia of the electrons). My guess is that it's dumped to a load resistor that converts it to heat (which might explain why the SC-2030 has a big honking heat sink).

If that's correct, then pick your poison - drop the excess voltage in the wires to the solar panel, or have the PWM controller drop it as heat. I think I'd rather drop it in the wires instead of heating up the battery compartment where my charge controller is located.
 
Rusty, welcome to the party! I've been in dialog with Bogart Engineering. They have no plans for an MPPT controller, and I asked about how their PWM works compared to "normal" PWM. Should have an answer next week.
 
I am also late to the party, but just went through a similar (but less well researched and documented! ) process.

After much reading and consideration, I went with a full system from Victron Energy - a BMV-700 (although if you are using 6v cells a BMV 702 with a mid pack voltage reading would be a good option), a 12/75 MPPT charge controller, the MPPT display, a VEbus to bluetooth adapter and a small Phoenix Inverter.

I looked closely at the trimetric given the reviews here, but I really couldn't see the advantage over other Coulomb counting battery monitors, and both the interface design and engineering seem a little archaic. That said, it does seem to be very reliable, but I haven't seen any indication that the other options (particularly the BMV-700) isn't reliable.

For me the big advantages over the Victron energy system over the bogart engineering system are:
- More modern and user friendly interface and design
- MPPT charging with fully configurable setpoints for what ever battery type/chemistry you choose.
- Real time display of MPPT charing performance.
- Cheaper (for my configuration any way)
- All parameters are configurable for both charger and monitor
- Part of a defined framework/network - if I want to get fancy in the future these devices will talk to their 'Color Control' and other fancy control panels.
- Bluetooth interface

At first I was on the fence about Bluetooth, but now that I have it, I realize it is a real game changer in many ways - programming all the setpoints and parameters is entirely straight forward and intuitive from any device (ios, android, windows osx). The intuitive app allows to easily view your battery status and history (# charge cycles, time since last full charge, depth of discharge etc) without having to remember weird 7 segment display codes. I park the camper in the driveway and leave the electronics on full time, this interface allows me to check on the camper from the living room on my iphone.

The only other comment I have is that I think your power usage scenarios are overly pessimistic. I know you are planning for the worst case scenario, but you should adjust your depth of discharge tolerance for this infrequent scenario. While it is not good to take your batteries down to 30% SOC (for AGM) it is not going to significantly damage them to do this once in a while. At least for AGM, I would recommend adjusting your worst case model with no charging for 2 days to end up at a 30% SOC. Then model your 'most likely scenario', which may be something more like 40Ah per day and XXX Ah per day solar current and shoot for a 50% SOC.

This is where having your battery monitor is really useful, for two reasons - First, it allows you to actually determine what your average and worst case usages actually are without having to make any assumptions. Second, it gives you realtime feedback as to where you stand, which allows you to slightly modify you usage when approaching the worst case scenario. If you know it is cold and cloudy, and you battery is approaching 30% SOC, you may choose to go for a drive that morning, as opposed to waiting until the afternoon. This is one of the hardest parts in modeling systems you are designing - how to model human factors!

Most importantly - Great write up, thanks for sharing and spurring what will hopefully continue to be a valuable discussion!
 
To clarify on my last point a little - here is a plot of depth of discharge (lowest SOC) vs the number of discharge cycles that an AGM battery will last:
Lifeline-Cycles1.png


From this you can see that regularly going to 50% SOC is not really a problem. 1000 discharge cycles is a LOT of cycles, for the weekend camper, this would easily outlive the camper. Going all the way down to 10% SOC (or 90% depth of discharge) on occasion is not really going to dramatically impact the life of the batteries, it is only the equivalent aging of 2 or 3 50% charge cycles.

Point being, I think you could probably halve the battery capacity you are considering and still have your battery pack last many years. In my considerations, weight is an important factor, so I am currently running a 70Ah AGM, and have a 100Ah LiFePO4 pack that I am working on to replace it and drop down to 30lb total battery weight.
 
From my initial reading, I'm liking this Victron stuff. The manuals are a bit harder to decipher than the Bogart ones. I have yet to see the spot where they explain their charging algorithm (says on the software page, but where?) and how to configure the set points.

So you went with both the BMV700 and the MPPT controller displays? Why both?
 
There charging algorithm is standard 4 stage bulk/absorption/float/equalize. All the voltage and time set points are adjustable either through the app or through the MPPT display. It is very intuitive through the app, so much so that I am not sure I even read the manual.

As to having both displays - the BMV display only tells you the net info for the battery, where as the MPPT display tells you exactly what the solar controller is doing, and gives you the history of the solar energy harvest. Honestly, you don't need the MPPT display, but I am a fan of information overload and buttons.

Vic Harder said:
From my initial reading, I'm liking this Victron stuff. The manuals are a bit harder to decipher than the Bogart ones. I have yet to see the spot where they explain their charging algorithm (says on the software page, but where?) and how to configure the set points.

So you went with both the BMV700 and the MPPT controller displays? Why both?
Click to expand...
 
Not that I'm planning on going lower than 50% SOC (at least until I"m convinced lower is okay) you make a good point about how much solar is really needed. I need enough energy to run my stuff (heater, fridge lights etc.) for whatever duration I require. If I arrive home after my week (or whatever) at 50% then I had enough energy. We just have to make sure aren't based on a best case scenario. Yes, my 100w panel could power me adequately if, if I were camped in Saline in July.

Now I need to go do some winter camping and see just what I can get away with. 225ah should be plenty for a weekend even if get 0 solar. Not to mention so far I haven't been using the alternator at all. I really need a month off to really see what I can do :)

The bluetooth on the victron is a nice feature. I've noticed a lot of boaters really like victron. Next up a Victron Trimetric shootout!
 
craig333 said:
The bluetooth on the victron is a nice feature. I've noticed a lot of boaters really like victron. Next up a Victron Trimetric shootout!
Click to expand...
I have a Victron if someone wants to bring by a trimetric we can have a Comapro! However I don't really see how the victron could loose. In my experience it does what it says it does, so even if the trimetric also does what it says it does, the victron wins on features and ease of use. It seems like the trimetric was the schnizzle when it came out 20 years ago, and thus it has a great reputation on the forums and the like. However it doesn't appear that Bogart has put much effort into continuing to innovate and improve the product, and as a result they have fallen behind.
 
So I pulled the trigger and ordered all my solar & power stuff. Big $$$. This is costing me more than the shell itself did! Still, I get a fridge, 465W of solar and 250AH of battery. I decided to go with the Victron solution for solar controllers, as they are just the best "inexpensive" MPPT controller out there that do almost everything that the Trimetric does in the PWM space. I say almost, because they don't have a great temperature compensation solution. They do have one, just not as good as the one Bogart Engineering uses.

So far I have just run the 2g wires from the truck battery back to the truck box. Waiting for other parts to arrive...
 
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