308 replies to this topic

[bfh4n]

The CTEK in my Fleet is installed near the batteries, so the size of those wires is not important. To some (unknown) degree, the capacity of the CTEK to boost voltage makes concerns about voltage drop in the wires from the truck battery to the CTEK unimportant. The same goes for truck generator output voltage.

 

The CTEK works similarly with solar input. (I guess all MPPT charge controllers do.) The voltage and current from the collector are not the same as what is applied to the battery. My brother has confirmed this with his single-collector solar CTEK installation.

 

By the way: The CTEK output is not a steady current, because it is constantly testing conditions (finding the Max Power Point, presumably) and adjusting accordingly. My brother reports that attempting to monitor the instantaneous output (voltage or current) gives confusing readings, especially with a digital meter. Averaging over about 10 seconds smooths it out. The TriMetric seems to do a good job of this, giving steady readings.

 

I used a 120-Amp Anderson Powerpole connector in my 4 AWG wires. It's very robust and a great waterproof hood is available. I had to buy a big special crimper, though.

 

- Bernard

[ntsqd]

Thanks for the SmartPass clarification.

 

I do not trust that voltage drop calculator link as it does not agree with the ABYC compliant chart that I've used for years. Nor do I trust most of the charts out there on the net because they are geared towards NEC applications employing AC and not DC. My Ancor Marine catalog has a chart for 3% Voltage Drop that I use. It can also be found here: http://www.ancorprod...nt-voltage-drop Note that on this chart that the circuit length is the total length, not the one-way length specified in the linked calculator. For a 3% V.D. at 20A it calls for 6 gauge up to a 40 foot total circuit length. 4 gauge is listed for 20A out to 60 feet, so that would be appropriate for less voltage drop on a shorter circuit length without going too far overkill or too deep into the wallet unnecessarily. Note the ripple effect that excessively large cables have on the wallet and on your inner peace from working with them in tight confines.

 

Given that the CTEK is a DC-DC converter the supplied voltage isn't too critical since it will trade amps for volts to deliver the programmed charging voltage. It may take a little longer to get to 100% SoC if the V.D. is excessive, but I doubt that a minor drop would even be noticed except by the most anal-retentive.

 

I am of the opinion that all camper battery controlling/charging devices should be mounted in the camper. This keeps the cables/wires between them and the battery(ies) as short as possible so they can be smaller. Mounting the device(s) outside the camper does not negate the need for large cables in the slightest, I see no gain and now when the camper is moved to a different truck none of it's support hardware came with it. That's what works for me anyway, I'm sure it's different for others.

 

Simply upgrading the charge wire should have no negative effect on the alternator. If anything it now has to work less hard to charge the battery(ies). I once read an article claiming that some resistance in the charge wire is desirable, but the argument made no sense. Flip side is that I see no reason for a 1/0 charge cable 18 inches long. Use the Voltage Drop tables to size the cable for the alt's max output over the length of the circuit. That being the length from the alternator to the truck's battery(ies) and back only.

[DrJ]

Vic,
I've been gone for days and just catching up on your outstanding posts.
Great work on educating our group on electrical power.

You mentioned before about using a 300 amp hour plus battery system. Do you have room for that big of a battery?

I went with 225 amp hours because that's all I could get to fit in my front dinette grandby battery compartment.

One thing I would recommend would be to have a portable and fixed panels to reach your solar goal.
I have 250 fixed 24 volt panel and a flexible 135 watt panel that I move wherever the sun is. Most times I get by without needing the portable panel.

Well done on putting together the most interesting post I've read in months!

[Vic Harder]

Thanks for the SmartPass clarification.

 

I do not trust that voltage drop calculator link as it does not agree with the ABYC compliant chart that I've used for years. Nor do I trust most of the charts out there on the net because they are geared towards NEC applications employing AC and not DC. My Ancor Marine catalog has a chart for 3% Voltage Drop that I use. It can also be found here: http://www.ancorprod...nt-voltage-drop Note that on this chart that the circuit length is the total length, not the one-way length specified in the linked calculator. For a 3% V.D. at 20A it calls for 6 gauge up to a 40 foot total circuit length. 4 gauge is listed for 20A out to 60 feet, so that would be appropriate for less voltage drop on a shorter circuit length without going too far overkill or too deep into the wallet unnecessarily. Note the ripple effect that excessively large cables have on the wallet and on your inner peace from working with them in tight confines.

 

Total length, doh.  Yes, I suppose there and back is more like 40' vs the 20' I was thinking.  And it is interesting that they recommend a max of 3% drop.  I suppose this is an industry accepted value?  I love your reasoning on inner peace, $$$ and wire gauge .  

 

I'm wondering if there is still value in reducing the voltage drop more than the 3% ABYC recommends, given that the battery manufacturer wants to see around 15v for the bulk charge phase.  It isn't just about the current.  That's also my concern about the CTEK, as the voltages are not adjustable.  They are OK, just not great.  And given that the batteries are the heaviest and  most expensive part of my power system, AND that they will fail eventually, I want to maximize their life expectancy.  I'm just not sure if the way to do that is to use the CTEK to avoid pushing high levels of both volts and amps at the batteries when they no longer need it, or to suffer from insufficiently charged batteries because the CTEK is factory configured to not supply enough volts to the batteries.  

 

I think i need more documentation, not more power! 

 

Simply upgrading the charge wire should have no negative effect on the alternator. If anything it now has to work less hard to charge the battery(ies). I once read an article claiming that some resistance in the charge wire is desirable, but the argument made no sense. Flip side is that I see no reason for a 1/0 charge cable 18 inches long. Use the Voltage Drop tables to size the cable for the alt's max output over the length of the circuit. That being the length from the alternator to the truck's battery(ies) and back only.

 

Thom, I'm not following you here.  Why only to the truck's batteries vs all the way back to the camper batteries/CTEK/ACR?

Edited by Vic Harder, 17 October 2016 - 06:15 PM.

[Vic Harder]

Vic,
I've been gone for days and just catching up on your outstanding posts.
Great work on educating our group on electrical power.

You mentioned before about using a 300 amp hour plus battery system. Do you have room for that big of a battery?

 

I'm building up a shell, so I can decide now how big my battery box needs to be.  The L16 (400+ AH) size is a bit too big for my tastes, but the 330 AH size is only an inch or so taller than the 220AH batteries.  I can work with that 


One thing I would recommend would be to have a portable and fixed panels to reach your solar goal.
I have 250 fixed 24 volt panel and a flexible 135 watt panel that I move wherever the sun is. Most times I get by without needing the portable panel.

 

That's what I was thinking too... 265w on the roof and 160w portable.  Are you feeding both into the same mppt controller?  You have a Tracer A mppt, right?  How is that working for you?

Well done on putting together the most interesting post I've read in months!

 

Thanks!  I know I'm interested because I am trying to understand all this before I spend big $$ on it.  It is gratifying to see others getting value from this discussion too.

[ntsqd]

The Ancor Marine page has a 10% V.D. (Voltage Drop) chart for motors etc., and a 3% V.D. chart for electronics. I use the 3% chart as my jumping-off point for everything. It builds in some Factor of Safety and things generally work better when the voltage is on the high end of the normal range.

 

DC-DC converters more or less consume Current to make Voltage when the output voltage desired is above the input voltage. So the CTEK will output whatever voltage it is programmed to output, it will just use some of the current to do so and not pass all of it on to the battery(ies).

 

As to the battery charge wire from the alternator, consider that if the camper were not present then the length from the alt. to the starting battery and back is the total length of the charging circuit. It is likely to be a fairly short length circuit, so a reasonable wire gauge will result in a low V.D. No need to use 1/0 there.

Add on the camper and that doesn't change, V.D. to the starting battery(ies) will be the same. Size the cables from the starting battery(ies) to the camper battery(ies) to have the minimum acceptable V.D., the alternator to starting battery charge wire will still have the designed V.D.

Said differently, the charge wire will be relatively short, so it can be large-ish without being near as big as the starting battery to camper battery wiring, and still have a very small V.D.

[Vic Harder]

More CTEK info.  There shore power battery chargers are way smarter than the D250s Dual, with settings for Wet/AGM/Cold weather charging.  The Dual doesn't have those settings, unfortunately.  Their generic voltages may work for some batteries, but not all.  

 

Right now I'm leaning away from the CTEK, and ONLY because the battery type/voltage is not customizable.

[craig333]

My recent trip allowed some decent experience with my upgrades. 250 watts of solar into 225ah of batteries monitored with the trimetric. Most days I'd awake in the morning with 2.9 volts or more still showing. I ran the heater, used the microwave and made no attempts at conserving power. My last day we came off the trail in the afternoon. Oops, taking something out of the fridge I'd accidentally turned it off. Seems they have little insulation as it was completely warm. Turned it back on. Next day after returning from Randsburg it was overcast. Trimetic showed 80% SOC and 12.6 volts. 

 

So overall I'm pretty happy. With good weather I should never have a problem. Now I'll have to do some more testing with just the alternator simulating poor weather conditions.

[Vic Harder]

More on Solar Charge Controllers

 

Fascinating.  I’ve been reading manuals.  (And they say men don’t read instructions!!)  Lots of manuals, from the manufacturers of charge controllers, both PWM and MPPT types.

 

Short conclusion:  SolarBob is onto something when he says the Trimetric SC2030 is one of the best/smartest controllers out there.

 

Long conclusion: 

 

1)      Most of the manufacturers of less expensive units have unchangeable presets for the various battery types.  This is not ideal

2)      Even the more expensive and reputable manufacturers (Morningstar/BlueSky/Midnite) use a charging algorithm that assumes your solar panels are sized such that you WILL get a full charge every day, not the actual state of the batteries

a.       A “Big enough” solar array is usually 1.5 to 2x watts in your solar array as AH in your batteries.   And IDEAL charging conditions. 

b.       So for 200 AH battery array you would need 300W of solar panels

c.       The algorithm is TIME based.  As in, charge at this voltage/current for xxx minutes

d.       The algorithm should check the voltage and current characteristics of the battery bank to determine if the charging is done, not assume the weather is good

e.       Ideally, it would do both C & D.

f.        The more expensive units do this: OutBackPower

3)      The Trimetric does this, and it is inexpensive to boot

 

Oh, the other surprise was that you should not mix different solar panels feeding into the same controller.

 

“Only solar panels of exact or similar current should be wired together in series. When you connect a 3A panel to a 3.5A panel, the overall current will be dragged down to 3A. Such a reduction in current will by all means lead to a reduction in power output and therefore loss in system performance.

Similarly only solar panels of exact or similar voltage should be wired together in parallel. When you connect a 15V panel to a 24 V panel, the overall voltage will be dragged down to 15 Volts. Such a reduction in voltage will lead to a reduction in power output and therefore loss in system performance.”  http://solarpanelsve...g-solar-panels/

 

This means that if you have different types of panels (for your portable and rooftop, or panels added later to an existing array) then you need to have multiple controllers, one for each type.

 

I know DrJ has had good luck with the EPEVER Tracer A, but those are among the controllers that only charge in the Absorb and Float phases for set amounts of time, not by when the batteries are actually charged. 

 

So I am leaning very strongly towards the Trimetric SC2030 and upgrading my wire sizes if needed.

[craig333]

Unfortunately some people don't read this correctly. "Similarly only solar panels of exact or similar voltage should be wired together in parallel". I've seen some people think you can't add panels of dissimilar "wattage" but how would a controller know? It just sees the total. Fortunately my rooftop panels and my portable panel are the same or close enough in voltage. 17v seems pretty common in the panels most of us are looking at.