Overlap? - trailer charging and solar

[mlrtime99]

Be gentle guys, my first go around in this world. I just picked up a tent trailer and I'd like to add a bit of 120v for those amenities that make our lives a little better.

A brief inventory of what I currently have:
- I'll be towing with my 2014 4Runner which currently has a Diehard 31m and a 7pin trailer connect. The AUX + pin is hot when the key is in the running position. Voltage appears to be .2 lower than batt and I've not traced the entire run to check gauge or fuse rating, I'd bet small. I have the 31M-PC2150ST version of this battery converted to 4 post which gives me very very clean wiring with my Warn ZEON 10S Platinum winch.

- I have a fairly cheap 12amp charger that I use to bring the starter battery up every 6 months or so when I get down to 12.1v (I have a blue sea m-LVD in the 4Runner babysitting the UHF radio, subwoofer, dashcam, amplifier, and LED bar).

- A new BushRanger 200XT on its way

Now what I think I want:
- I need the ability to charge the trailer battery prior to the trips with something a little more intelligent and capable of bringing something that's be drained a bit more than my $40 schumacher might support.
- I'd love to keep the trailer charging while in tow (between spots during long trips)
- I'd like a battery swappable with my vehicle battery. I know if I'm at the trailer and in a position to swap batteries I could just as easily jump them but something about this really appeals to me but I'm willing to be talked out of it (lower costs, more Ah).
- Solar, yep.

Parts:
I'm still looking around but I think I'm sold on a foldable solar product like Powerfilm or Flexopower. Form factor aside that means I'm only going to end up with 150W or so of solar.

The CTEK D250S seems like a pretty attractive MPPT charge controller with the alternator input. If I could take the 7pin output of the trailer harness, fuse it down with an auto reset breaker to protect the factory wiring or increase the gauge I'd at least get some help from the 4Runner alternator.

For the charger/inverter the Samlex EVO-2212 looks pretty attractive. Pure sine wave (I'll be running a lot of sensitive electronic like laptops, battery chargers) and I've outgrown 600W and 1200W inverters in the past so I'd like to overspec this a bit. I'm not the biggest fan of needing to support 280ish A on the battery cables but I'll make it work. It does have a solar input but that seems redundant with the D250S.

Again with another 31m I'd have 105Ah.

So what's broken here? From reading the forums I gather that I should never equalize an AGM, the 2212 also has a pretty hefty 100A of charging if I add a second battery. I'd love an all in one solution here but I think this is as minimal as I can get.

Thoughts?

 

[dwh]

I doubt you need to do anything to the factory 7pin to feed the ctek, which is only a 20a charger.

 

[mlrtime99]

Do you think the D250S is adding any value outside of the solar charge controller? I haven't been able to tell from their datasheets WHAT exactly it's doing besides switching sources but I assumed it might increase a low voltage input (from a lengthy trailer run) into something a bit more healthy for charging an AGM battery. If not I could just get a quality MPPT and skip the neat-o factor.

 

[DiploStrat]

Do you think the D250S is adding any value outside of the solar charge controller? I haven't been able to tell from their datasheets WHAT exactly it's doing besides switching sources but I assumed it might increase a low voltage input (from a lengthy trailer run) into something a bit more healthy for charging an AGM battery. If not I could just get a quality MPPT and skip the neat-o factor.

The data sheets and the owners manual suffer from a bit of bafflegab but, in grossest terms, a B2B:

-- Draws down the voltage of the starter battery to 13v.
-- This causes the vehicle alternator to produce more current.
-- The B2B takes this current and boosts it to (in the case of the D250S) 14.4v @ 70F, adding temperature compensation.

So the B2B throws away the higher amperage of the alternator in exchange for 20 amps of higher voltage. (N.B. Some B2B offer different profiles, the option to drop the voltage, and compensation for newer vehicles with alternator braking.) The D250S still requires healthy wire sizes.

Huge discussion of B2B by a skeptic here: http://www.smartgauge.co.uk/controllers.html

The CTEK D250S/SmartPass combo gets really interesting if your vehicle only charges at 13.9v, because:

-- It gives you 20A of 14.4v at the camper battery.
-- It incorporates an intelligent relay for the first part of the charge, giving you more than 20A, albeit at lower voltage.
-- It incorporates a small MPPT controller, saving the cost.
-- It does allow solar charge of the starter battery, a function not performed by most B2B.

 

[mlrtime99]

The CTEK D250S/SmartPass combo gets really interesting if your vehicle only charges at 13.9v, because:

EXACTLY what I was hoping to hear since I have the infamous minimal 13.8v Toyota charging system. It seems like as long as I protect that OEM wiring with an auto reset breaker I should be a happy camper (pun intended).

Thanks Diplo!

 

[dwh]

Do you think the D250S is adding any value outside of the solar charge controller? I haven't been able to tell from their datasheets WHAT exactly it's doing besides switching sources but I assumed it might increase a low voltage input (from a lengthy trailer run) into something a bit more healthy for charging an AGM battery. If not I could just get a quality MPPT and skip the neat-o factor.

Well, it depends on the normal bus voltage of your truck's chassis electrical system. In other words, what your voltage regulator is set to. My truck maintains 14.5v at any RPM above idle, so 14.4v would be a step down on my truck.

Voltage drop back to the trailer battery is completely irrelevant. The loop of wire that is charging the battery is going to be at battery voltage. Everywhere. There is no voltage drop from point A to point B, that's a fallacious concept. A circuit is a circle and a circle has no ends. So if the battery is at 12v, then the wire loop will also be at 12v.

So in terms of voltage, a multi-stage charger just runs wide open (not bothering to regulate the voltage) until the battery reaches the bulk stage set point, and then the charger starts regulating the voltage to prevent overcharging.

The voltage regulator on your truck does the same thing. So if your truck's voltage regulator is set to say 13.9v, then yes, using the ctek to step up the voltage and bulk the battery to 14.4v, and then holding the voltage up above 14v while the battery absorbs (which takes hours) will get the battery charged faster.

But if your truck's bus voltage is already up above 14v, then you won't see much, if any, improvement from adding the ctek.

Ultimately, the battery voltage will rise until it gets high enough for the regulator (truck or ctek) to start regulating the voltage. The wire won't make any difference to that. The wire can make a difference in how long that takes, because while it won't reduce the voltage, it can reduce the amperage. The factory hot to the 7pin is probably 10 guage, so you probably won't ever see more than 30a flowing through it to the trailer battery. But with the ctek, you won't see more than 20.


As for the MPPT, the ctek's solar input is limited to 22v, so if your PV module has a Vmp higher than 22v, you can't use it with the ctek.


So...what is your truck's bus voltage regulated at?

 

[dwh]

Okay, question answered. So yes, the ctek will help. The smartpass add on to the 250s will not help if you are getting power from the factory 7pin.

 

[DiploStrat]

EXACTLY what I was hoping to hear since I have the infamous minimal 13.8v Toyota charging system. It seems like as long as I protect that OEM wiring with an auto reset breaker I should be a happy camper (pun intended).

Thanks Diplo!

But before you buy a CTEK, look at the Toyota voltage control devices on this page: http://www.mechman.com/voltage-control-modules/ (Sadly, I am not aware of a plug and play module for Sprinters.)

Australians run their Toyotas at 14v+ all the time. These make it easy.

And whether you call it voltage drop or amp choke, wire size is important to charge speed. I am fond of playing with this little toy: http://www.calculator.net/voltage-d...ce=30&distanceunit=feet&amperes=100&x=28&y=12

Change the values to reflect your voltage, amperage, wire size, and distance. Note that as amps drop, so does voltage drop - so dwh is correct, but size does matter if you want any kind of realistic charge rate.

 

[mlrtime99]

Another good point Diplo. I've researched a few of those options and actually found a few of the devices in my car react VERY negatively to higher voltage. My navigation unit, for example, continually reboots itself while the charger delivers 14.7v to the battery. With all of the modern do-dads they cram into there if I can get away with the stock voltage output being boosted by the D250S so it can do its job I'd prefer that route.

Also noted on the 7pin wiring. I'll probably upgrade that to 10AWG and run it from my always on m-LVD. This will let the D250S do its job on solar and charge the starter battery without the key needing to be in the "on" position yet all the m-LVD to disconnect the D250S if the starter battery drops to 12.1v.

Feel free to poke holes.

 

[dwh]

The 250 won't charge the starter battery at all without the smartpass. Solar goes only to the aux battery.

Far as I know, the 250 won't charge your aux battery from your starter battery unless it sees a high enough voltage on the chassis bus side.

So with the engine off, the 250 will solar charge aux battery and that's it. Won't charge starter battery, but won't draw it down either.



Repeatedly drawing your starter battery down to 12.1v is going to shorten it's life.

 

[mlrtime99]

This may just be marketing B.S. from the D250S manual but it sounds like when the house battery is fully charged...

"The solar input will also maintain the Alternator battery"

 

[dwh]

But is that from the section of the manual that talks about the smartpass? I'm just working from memory here, been years since I looked at that manual.

 

[DiploStrat]

Manual

The D250S/SmartPass manual is here: http://smartercharger.com/wp-content/uploads/2010/11/D250S-DUAL_EN.pdf

Much of it is rather opaque with advertising bafflegab, but basically:

-- The set up that most of us want is on page 20.

-- It is the SmartPass that feeds solar/shore power back to the starter battery. (If I read correctly.)

And, the suggested wire gauges are on page 26. HINT: They're BIG.