3 electrical systems

[Blue~Go]

Okay, I just read through the manual. I'm not going to organize this because it would take forever, but I wrote my thoughts as I went along so that's how they are presented. They are below the numbered points which I tried to organize a little bit. I wouldn't use this for solar charging myself, as I understand it from a quick read-through. Why?

1) Battery charging voltages are not adjustable. You get one preset for your battery type and have to hope it matches (would not match my Lifelines).

2) You cannot put solar panels in series (voltage limit is only 23 volts). Even if you go parallel on the roof (which is fine, just means larger wire), I really really like to go series for ground panels because you can have a longer/thinner wire to set them in an advantageous place. (I get such good use out of my ground panels that I could not give that up.)

3) The 20 amps of solar charging is cut down to ~15 amps if the temperature is over 86ºF. That's okay if you only have 200 watts of panels, but no more (my solar controller will max out its 15 amps in full sun with 200 watts of panels). I forget your planned solar panel array size and type.

4) I don't see a very good display unless I'm missing it.

5) Their wire sizing chart allows for 10% voltage drop. Obviously you wouldn't do that, but it just makes me wonder what they are thinking, unless I'm misunderstanding.

6) Temperature compensation factor is not adjustable (again, fine if it happens to match your batteries).

As far as alternator charging I would have to compare it to other units to see how they compare. Maybe no other ones are better (and once you add the Smart Pass I'm not even sure which adjustment and charge factors from the SA250 apply?). I'm very familiar with solar controllers so that's easier for me to judge.

I guess this seems to me like those bookshelf stereos back in the day where they were never as good as components for all but the most quick and simple setups. Where might I use this? Well, I probably never would, but maybe I could see it for something like a Jeep with super limited space and where you would never put in anything more involved anyway.

Here are my notes from as I read along in the instructions. Some of these things I'm obviously just wondering about and don't know or couldn't tell.

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Temperature compensated charge voltage
The D250SA optimises the charge voltage by increasing the charge voltage at temperatures below 25°C/77°F and reducing it at temperatures higher than 25°C/77°F. The functions is always active.


Can the compensation factor be adjusted to match that of the batteries? Answer: No.
Does this apply to the Smart Pass too? I can't tell.

Optimised charging of AGM batteries
The D250SA can provide a suitable charging voltage for optimal charging of AGM (Absorbent Glass Mat) batteries, which require a higher charge voltage than other types of lead-acid battery. The installation section describes how the D250SA needs to be connected in order to activate the AGM battery function.

Is this adjustable? Answer, no, it is set at 23 mV/°C from 25°C/77°F. If this matches your batteries then great. If not you can't change it. This is "by what factor it adjusts the charging for every degree above and below 77F"

Also is the Smartpass is temperature compensated?? This might be something you would want if you are doing a lot of alternator charging (but one thing I don't know is if other ones, like Sterling, are temperature compensated from the start/alternator). Or does this somehow use the 250 temp comp? Voltage settings?

• SMARTPASS 120 supplies consumers from the alternator instead of from the service battery while the service battery is charging, which permits faster charging.

Not sure why this is necessary? All power has to come from somewhere, so normally while driving it's consumers from house bank and charge from start/alternator (and solar if sun it out). Why is it better to have both coming from alternator/start bank? Seems like it would just reduce charging by that amount? Or put more load on alternator? Maybe I'm missing something. Or maybe this really applies to something like a Jeep with a 60ah house bank and a huge alternator, where the house bank can't keep up?


Battery guard
SMARTPASS 120 disconnects consumers when the service battery voltage is low in order to avoid deep discharge, which would damage the battery. The consumers are reconnected after the service battery voltage has increased. Connect critical consumers directly to the service battery so they will not be disconnected if the voltage falls to lower than 11.5V.

So in order to use this you connect some of your house loads through the start bank? I'm not sure I get this.

• Start assistance
SMARTPASS 120 automatically connects the service battery to the starter battery for 10 sec to assist, if the starter battery on its own is unable to start the engine. After the start assistance func- tion has been activated, SMARTPASS 120 will display a fault indication until starting has been achieved without using the start assistance function.

Make sure you can see this indication and look for it often! Some of the old Sure Power combiners had an automatic function like this and it "allowed" people to go for years without knowing their start battery had failed. I would rather this not exist and so I know obviously that my start battery is not up to the task and I manually combine then fix it at first opportunity.

• Separation of the starter battery and the service battery
SMARTPASS 120 separates the starter battery from the service battery when the engine is not running.

Is this magnetic latching, or? If not, what type is it and does it induce any voltage drop? I couldn't find this but admittedly I was nearly skimming.

The cable size chart does not specify one-way or round trip wiring. I would guess one-way since most vehicles use chassis ground for the return trip so there is only one wire (plus two jumper bits in the negative run). But I question their math as they are saying 1AWG cable for up to 140 amps on a 30 foot wire? Let's check that voltage drop: That's 10% voltage drop. That is beyond unacceptable for something like this. I mean look at it this way: You carefully buy a product that will absorb charge your batteries at a carefully set 14.4 volts. Then you reduce that by 10%. Now you are "charging" your batteries at 13 volts…. No. Maybe there is a voltage sense wire? [Note, I don't see a voltage sense wire]

On the solar part, maximum input voltage is 23 volts. So that means no series connected panels whatsoever. That's not too bad on the roof but kind of cuts out ground panels with any meaningful length of wire. Why so low?

Okay, here we get to the meat of it. This is what cut it out of my consideration list before (friend was asking if it was a good idea): Battery charging parameters are not adjustable. Their "AGM" profile, for example, is not correct for any of the parameters of my Lifeline batteries. Does it fit yours? Do you ever plan to change? I just think this is a bad idea in general. Why have something so fancy and then not be able to set it correctly (unless you find batteries that happen to fit their parameters). They have "AGM" at absorb 14.7 volts and float 13.6 volts. Lifeline AGM calls for 14.4 and 13.3 (tenths are a big deal in battery charging).

Also a key thing in charging lead acid batteries, is… what mechanism does the charger use to decide when to stop absorbing (ideally this is exactly when the battery is full; different chargers use different ways). I don't see them saying how, but I see a "timeout" of 12 hours (you would normally absorb for something like 1-4 hours). How are they deciding when to go from absorb to float?

It only works down to -4F. Probably not an issue but something to note if you are up north in winter. BUT more importantly, at 86ºF the 250 is reduced to 16 amps. That could be an issue for solar power, as 86 is not that hot. If you are not going to have more than 200 watts of solar then it might not matter so much. I don't think that affects alternator power (not mentioned in 120 specs). That wouldn't work for me for solar though.

[Blue~Go]

So, if you decide you want to step back and re-evaluate the Ctek setup, I would ask you this:

1) How much of your house bank charging do you see being alternator/start charging?

2) What type of solar array do you have planned (now or in future)?

3) What are the charging parameters for your house batts and do you ever see changing them? (Type, brand, or size.)

4) What type of climates do you plan to travel in?

[Riste]

You are amazing.
Our style of travel is just that, we will be touring the country, probably not staying in a single location for more that 2 days.
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Therefore I would expect that most of our charging would be done by the alternator.
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Solar array is not determined. I would like as much as needed to replenish what the alternator does not do. (Obviously I am not an English major).
Anticipate using a little less than 100 amp hours per day.
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I will attempt to attach the battery profile that Interstate (GC2-ELC) sent me.
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We will be "chasing 70" with the goal of not seeing any extreme temps.

[Riste]

Bulk: 10% of 20hr Ah Rating 2.47 (per cell) 7.4 (6 volt)
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Absorption:Taper to 3% of 20 hr Ah Rating and hold for 2-3 hours 2.47 (per cell) 7.4 (6 volt)
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Float 2.20 (per cell) 6.6 (6 volt)
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Equalization Total time = 2 hrs. 2.60 (per cell) 7.8 (6 volt)

[Riste]

More info on the Interstate CG2-ECL.
Why this battery-an acquaintance runs the battery shop, kind obligated. He is however not overly technical.
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We recommend using the following: For every 1º F below 77º F add 0.0028 volts per cell or for every 1 C below 25º C add
0.005 volts per cell to the charger voltage setting.
▪ 1: A 12 volt battery @ 70º F. The recommended charging voltage at 77º F is 14.8 volts. The adjusted charging voltage is
14.8 + (6 cells * 7 degrees below * 0.0028) = 14.92 volts.
▪ 2: A 12 volt battery @ 21º C. The recommended charging voltage at 25º C is 14.8 volts. The adjusted charging voltage is
14.8 + (6 cells * 4 degrees below * 0.005) = 14.92 volts.
For every 1º F above 77º F subtract 0.0028 volts per cell or for every 1º C above 25º C subtract 0.005 volts per cell to the
charger voltage setting.
▪ 1: A 12 volt battery @ 85º F. The recommended charger voltage at 77º F is 14.8 volts. The adjusted charging voltage is
14.8 – (6 cells * 8 degrees above * 0.0028) = 14.67 volts.

[Blue~Go]

Can you tell me what the below figures are for? Oh, I think this is specs for your battery? I looked up the Interstate GC2-ECL and I see these are flooded cell batteries. Are yours the ECL-S or the ECL-UT?

I am more familiar with AGMs and have never used flooded cells for a house bank in a boat or RV. But let's see if we can make sense of this.

Bulk: 10% of 20hr Ah Rating

Okay this is the number of amps they want to see coming from your charger. Okay, I see the "UTL" version has a 225 amp hour 20 hour rating (your bank will still be 225 amp hours because you are combining two 6 volt batteries). So 10% of that is 22.5 amps. What I'm not sure of is if you need to limit your charger, or if the batteries will simply only take what they need and/or if this is a minimum and more is fine. Perhaps the internal resistance limits them. It's the opposite situation with AGM or Lithium as they are like big black holes and will suck up all the charging you can give them (well, comparatively anyway). So that's what I'm used to. Is this a minimum? Maximum? Or? Something to look into as I am more used to AGM or a little bit Lithium (but not flooded). As a rule of thumb I had always heard 10% of bank size, which in your case would be 22.5 so those match. Again not sure if this is a minimum and more is fine.

Absorption:Taper to 3% of 20 hr Ah Rating and hold for 2-3 hours 2.47 (per cell) 7.4 (6 volt)

So it looks like they want to absorb at 14.8 volts. I don't think the C-tek went that high, did it?

The holding for 2-3 hours sounds a little generic and non-specific, but maybe they assume you have a non-smart charger (or maybe it's not that critical for flooded cells). Here is why I say that. For example the Lifeline batteries are fully charged when a certain percentage of their capacity in amps is going in at the absorption rate. The absorption stage is constant voltage with diminishing current as they fill up. What this means for my bank is that when I am in absorb the batteries are fully charged when the current has gone down to about 1.8 amps. This might take short or long time depending on various factors. It is usually from 1-4 hours though. So I guess you could just say hold for 2-3 hours. I don't remember what the C-tek does for absorb time and how it decides to end it. Maybe check on that. AGM like to be charged 100% as often as possible and don't really like partial states of charge so you don't want to short them on absorb time. Not sure how flooded cells compare.

Float 2.20 (per cell) 6.6 (6 volt)

Okay so float voltage desired is 13.2.

So you want 14.8 absorb /13.2 float.
The C-tek in flooded setting gives you 14.4 absorb /13.6 float so that's not right.
The C-tek in AGM setting gives you 14.7 absorb 13.6 float. Closer.
Neither is exactly what the battery calls for though which is why I like adjustable voltage settings.

Equalization Total time = 2 hrs. 2.60 (per cell) 7.8 (6 volt)

Equalization is something you only do occasionally. I set mine to manual so I know what's going on. So they want 15.6 volts for 2 hours. C-tek gives you 15.8 volts for 4 hours (you could manually stop it I imagine). You might want to disconnect certain things during this time as 15.8 volts might not make some loads happy (kind of high).

[Blue~Go]

PS: Given that lots of people charge with alternator and flooded batteries, I imagine a larger charger than 22 amps is not a problem. What I don't know is how much advantage it will give you. In other words, how does the internal resistance of the batteries relate to how MUCH current they can take (if the 22 amps is a minimum recommendation). That's something I have not really looked into for flooded cell batteries, although common sense says people are doing it and no-one is exploding. Although would they actually accept anywhere near 140 amps? If not, then no sense wiring with huge wire to pass that kind of current with low voltage drop. Yes, you will be passing close to 200 amps if self jump starting, but in that case voltage drop is not quite as critical as with precise charging. However THAT said, you'll likely have 1/0 anyway just for fusing. But you may not need any larger than that if the batteries cannot accept the full 140 amps anyway. OTOOH, this is kind of moot if you can't set your charging voltages correctly. (Ha, it's always a matter of circling around and around to figure these things out.)

[Riste]

" I looked up the Interstate GC2-ECL and I see these are flooded cell batteries. Are yours the ECL-S or the ECL-UT?"
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The only difference between S and UT are the terminals.
Given the difference between what the battery would like and what ctek offers, what would be in your shopping cart?
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It feels like you are suggesting that the solar should be stand alone. What would be in your shopping cart?

[Blue~Go]

Well, I need to preface this with I'm not an expert on flooded cell batteries (although they are lead-acid batteries, as are AGM, but I mean the nuances). And also, there are lots of ways to go and everyone is different. For example, a person could toss in a single cheap flooded battery, figure they'd buy a new one every year, and only do the minimum safety requirements (fusing). Nothing wrong with, IMO, that as long as it's a choice. And it is a good choice for some scenarios. It's basically what did for the first year while I built up my system (my Chinook came with one Group 27 Interstate flooded battery).

I'm kind of the opposite. BUT, I also live by my 12-volt system, and charge almost entirely with solar, and so I don't mind putting money and thought into the system to make it perform well and last reasonably long.

Given that you are buying Blue Sea panels, I'm guessing you are not trying to go minimum dollar. If you are going to be traveling long term, that tells me it's going to be your home for that period of time. So if it were me that would point to a decent quality system. So let ask you this (yep, another question). Pardon me if this is a repeat but I'm laid up with a broken foot and my brain is a little foggy.

So, let's flesh it out:

1) Lots of traveling, I'm presuming for some longish period of time (can't just be weekends if you are chasing 70º).

2) Not so much sitting in one place for weeks.

3) Plugging in what percentage of the time? This has to do with how much you need to provide your own power vs. getting it via cord.

4) Where are you on the "hard walled tent" vs. "it has to be just like home" scale? This will describe your power expectations.

If you already told me this, I'm sorry to ask again. But just humor me

[Riste]

Bummer about the foot. I hope it "heals" quickly (attempt at a foot joke).
Answers:
So, let's flesh it out:

1) Lots of traveling, I'm presuming for some longish period of time (can't just be weekends if you are chasing 70º).
Planning on several months at a time on the road.
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2) Not so much sitting in one place for weeks.
True, maybe a few three, or four day spots, but mostly a new place every day or two.
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3) Plugging in what percentage of the time? This has to do with how much you need to provide your own power vs. getting it via cord.
Plan on plugging in if we really need the Air Con, or heat, a long hot shower, or the batteries need a big charge. Lets use 20% of the time as plug in.
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4) Where are you on the "hard walled tent" vs. "it has to be just like home" scale? This will describe your power expectations.
We do NOT want to put wheels under home home. We are hoping for this to be a different experience, want some comfort of course (a good nights sleep is critical), having a wet bath, and the ability to feed ourselves. We are vegan, so cooking is relativity easy. Will use a propane cook top, the chest refrigerator. Not much tv, lots of reading and computer use. Lights are all LED.