Getting house batteries close to 100% SOC

[user 37446]

Hi,

Having read a lot of threads from others who understand this whole battery recharging thing better than I do, I still have a "basic" question that I'd like your thoughts on please:

(I am still S&B currently however am planning to succeed at this so am writing notes and researching a lot).  Figuring on two 6v deep cycle golf cart batteries, wired in parallel, and then make sure to have about a 1:1 solar watt to battery amp ratio, with cycling down to appx 75% SOC nightly.

Option 1 - depend on large gauge (0-4) stranded copper cabling from the alternator through the c. duty solenoid to bulk charge (figuring no more than 30-60 minutes of driving, not idling, a day).

Option 2 - a 12 volt to 12 volt charging system (perhaps a CTEK D250 with the additional 80 amp Smartpass system, about $450) which could then be used as both an mppt controller and multi-stage smart battery charger?  

Pro's:  It seems that the cost of an average Morningstar or equivalent 20-30 amp MPPT controller, the extra heavy guage copper wiring, all the fittings, crimps, fuses, labor, a 200 amp Cole Hersey type quality cont. duty solenoid could be about the same cost as simply buying the 12v to 12v (CTEK) system and forgoing all the previously mentioned stuff.

Cons: Location of the 12v to 12v unit (usually pictured close to the starting battery) which means the CTEK and its built-in MPPT controller are also now under the hood for heat and wiring purposes, a distance away from the solar leads and the batteries/inverter. (All the Aussies videos were showing SUV's or pickups with much more engine bay room, never in a van.)

I dont want to overthink this, and I remember a statement from Sternwake on a thread saying that batteries are to serve us, not the other way around...

I just am aware (thanks to the ever helpful forum) that most standard alternator charging systems dont bring the house batteries up to 100% SOC due to the voltage regulator limitations (13,4 ish).  Plus my extended time up here in Canada and the PNW often has me dealing with relatively poor solar conditions (like at the present).  Since I dont plan on using shore power or a generator, those options for recharging are out.

Thanks for any replies. Maybe this will help someone else out too.

 

[Spaceman Spiff]

I have two GC2s @ 208AH charged by 200W solar through a TS-45.  I am usually at 100% (Trimetric calibrated by S.G.) by 1PM.  I have alternator charging capability but seldom need it.  Some of my camping is under forest canopy (Northern Minnesota, Wisconsin, U.P.).

IIRC, I rejected the CTEK because it was not programable.

 -- Spiff

 

[user 37446]

I have two GC2s @ 208AH charged by 200W solar through a TS-45.  I am usually at 100% (Trimetric calibrated by S.G.) by 1PM.  I have alternator charging capability but seldom need it.  Some of my camping is under forest canopy (Northern Minnesota, Wisconsin, U.P.).

IIRC, I rejected the CTEK because it was not programable.

 -- Spiff

Sounds like you are at a northern latitude with not huge energy usage and its working out ok for you!  I was concerned that a 2-4 amp per hour fridge draw (summers more) and the microwave or other electrical cooking at times would deplete me more than 10 ish amps x 2-4 hours of "peak sun" could replace.  Just this last week in BC on Victoria Island its been rain or heavy overcast daily, so if I had to depend on solar it would have been very marginal, maybe an amp hour or two per panel (per hour from 10-2pm) at best. That's what I'm trying to help with on the alternator or 12 volt to 12 volt.

So you dont like the non-programmable 12v-12v, and you are satisfied with just the solar?  What's your average daily usage, if I might ask.  Any generator supplement?

Thanks Spiff, I've read many of your other posts and consider you knowledgeable.

 

[BradKW]

I had never looked at that CTEK before, but it doesn't appear that you can even select battery type, or pick from some generic profiles?

Does the Smartpass operate independently, or do you also need the 250?

 

[WalkaboutTed]

Hey This World,
I have the CTEK d250s and the Smartpass. My system is in the back of the van, connected to the engine battery by a 4 gauge cable. I'm currently having an issue with my solar charging, but I'm in communication with the Sweden office and they'll be sending me a new one. The company is very customer oriented. I, too bought the CTEK system because of all the rave reviews in Australia and UK. But, I thought I was going to be satisfied with my 280 watts on the roof and the 100 watts portable. The max for the CTEK mppt is 20 amps (340watts). I'm over that at 380 with the portable deployed. That really is no problem as the chances of me getting in the full 340 Watts from my 380 is slim. I was planning on using the portable only for cloudy days or if we're parked in the shade, so we'd never get up to the max.

But, I'm adding another 165 watt panel (for my rice cooker and more TV for the hubby in addition to the 4.2 cu foot fridge). That will bring me to 445 watts on the roof and the 100watt portable. I'll leave the 100 watt portable on d250s and will just squeak by with the Blue Sky 3000i mppt (max 30amps/400watts). So, I need both the CTEK unit AND the second mppt charge controller. I have 300 ah of battery bank. I also have a CTEK MUS 25000 AC to DC charger. That is meant for multiple battery banks and is superb. We're planning to use that charger for occasional RV park hookups or if we can bribe someone to let us plug in for a night. I've been using the 25000 for several months and am pleased with it.

The Smartpass is great. Even at idle, I've pumped in over 50amps. But, given your latitude, you may want to have more than a couple hundred watts of solar. You can do as I am and add it in with an additional mppt charge controller after the fact. Or you can start in with more. I am happy with the 5 stage battery DC to DC charger and will be using the ctek solar mppt for my portable. That way, any overage will flow to the engine battery. So, in retrospect, I'm satisfied with my configuration, even if it turned out to be different from what I initially envisioned. I didn't know that I was going to turn into a solar whore.

This all sounds very confusing. I'm very wordy (no, really?). PM me if you have additional questions. You may want to read from some of my multiple, very wordy threads.
Best of all,
Ted

 

[John61CT]

Too many things mixed up here, best to post specifics one topic at a time.

Either shoot for getting ALL the way to true 100% most cycles, or buy cheapest GC2s and plan on replacing them relatively frequently.

Fossil fuel charging will only get you part way there unless you are doing all-day driving stints. You need enough solar panels and sunny days, maybe supplement with a gennie, or shore power overnight to finish the long tail.

Cable sizing isn't to reduce charge times, more like fuses, to prevent fire and explosions.

The point of CTEK is to get the right voltage to your "other than Alt charged" batt, usually due to long cable runs or different chemistry banks.

Point of SmartPass is overcoming the 20A limit, usually not needed.

The built-in solar controller is OK to keep things topped up in the boonies, not great as a main one for heavy usage.

 

[user 37446]

Too many things mixed up here, best to post specifics one topic at a time.

Either shoot for getting ALL the way to true 100% most cycles, or buy cheapest GC2s and plan on replacing them relatively frequently.

Fossil fuel charging will only get you part way there unless you are doing all-day driving stints. You need enough solar panels and sunny days, maybe supplement with a gennie, or shore power overnight to finish the long tail.

Cable sizing isn't to reduce charge times, more like fuses, to prevent fire and explosions.

The point of CTEK is to get the right voltage to your "other than Alt charged" batt, usually due to long cable runs or different chemistry banks.

Point of SmartPass is overcoming the 20A limit, usually not needed.

The built-in solar controller is OK to keep things topped up in the boonies, not great as a main one for heavy usage.

I agree that the choice is to either replace batteries annually (I had considered Walmart marine batteries but nearly every "serious" thread discouraged that method) or focus on getting to 100% SOC daily.  I have read too many of SternWake's threads to believe that its healthy to just hope for the best or maybe figure that 85-90 is ok.  In school Id have been happy with 90%...

Anyway, because of where I spend half the year (again, currently I am in a condo with a family member up here and also stay in a condo down there) I dont have need for solar or 12v to 12v just yet. Just trying to figure it out.

The latitude up here and the typical PNW weather would probably call for 300 watts of solar instead of my planned 200.  I'd likely be able to fit that onto a conversion van but no more (since there's a F Fan in the planning too). 

I could go simple and just get a $25 c. duty solenoid (85 amp) with a 100 A fuse and some 4 guage cabling and call it good. I just did not think that's going to cut it (for 100% SOC) and dont want to kill $200 in batteries in a year.  Of course the price of the 12v to 12 volt system is anywhere from $240-450 so that's a set or two of batteries as well. :-/

Spiff said (and I have no reason to doubt him) that his Trimetric monitoring and specific gravity checks show him he's at 100% SOC daily by 1 pm up in Minnesota, and that with 200 watts of solar.  So maybe I'm being pessimistic. After all, I'm not out there doing it and (you) are...  :huh:

 

[user 37446]

I had never looked at that CTEK before, but it doesn't appear that you can even select battery type, or pick from some generic profiles?

Does the Smartpass operate independently, or do you also need the 250?

Hi Brad,

From the Aussie videos I see and the Amazon reviews and product descriptions, the Smartpass adds up to 80 additional amps to the 250 unit's standard 20 amp charge rate however both need to be bought.

 

[Spaceman Spiff]

 . . .  I was concerned that a 2-4 amp per hour fridge draw (summers more) and the microwave or other electrical cooking at times would deplete me more than 10 ish amps x 2-4 hours of "peak sun" could replace.  Just this last week in BC on Victoria Island its been rain or heavy overcast daily, so if I had to depend on solar it would have been very marginal, maybe an amp hour or two per panel (per hour from 10-2pm) at best. That's what I'm trying to help with on the alternator or 12 volt to 12 volt.

So you dont like the non-programmable 12v-12v, and you are satisfied with just the solar?  What's your average daily usage, if I might ask.  Any generator supplement? . . .

Refrigerator should be no problem with 200W/200AH.  I only cook with propane so I can't comment on what cooking would draw.  My advice is to get a kill-a-watt meter and do some measurements at home to come up with a realistic energy budget.  And you can get charts that will tell you what to expect for solar energy in the places and times you will be staying.  Those will give you what you need to figure out how much solar you will need.  I figure 5 hours of max charging in the summer and 4 in fall and spring for the places I go (Great Lakes and Mountain West).

I don't dislike the non-programmables, I just think that one gets better results from a customizable system.  IMO whenever you get something that does multiple things it compromises on each individual task; so I got a charge controller that just regulates my solar.  I'm probably a pretty light user and it has served me well.

My main draw is an old Norcold refrigerator.  It runs ~30% duty cycle at 70ºF (~28AH) and 50%+ duty cycle at 90º ambient (~45AH).  The rest of my loads are small:  MaxxFan on low (~1AH), LED lights (~0.3AH), run a cell booster as needed (~4AH), charge a laptop (~4AH), inReach PEB (~1AH), i-Phone (~2AH), jetpack (~0.5AH).

My only other source of charging is my truck alternator; which I have only used twice.  I do have the room to double my solar but so far I don't see the need.

 -- Spiff

 

[highdesertranger]

I have said this many times, "heating anything with electricity is very inefficient." it might be convenient but it's inefficient. highdesertranger

 

[user 37446]

Yes, I'm slowly morphing away from the microwave, and that change in plans would save me a 1,000 watts of inverter (difference between say 500 and 1,500), large fuses, the heavy cabling, possibly the 3rd 100 watt solar panel, worry about voltage sag and all. I've got the propane stove and bottles, just have to deal with my breaking the zapping food and drink habit. I've been living with/cooking solely with the microwave for months, haven't turned the stove on for a long time. Retraining needed.

 

[John61CT]

the Smartpass adds up to 80 additional amps to the 250 unit's standard 20 amp charge rate however both need to be bought.

The SmartPassonly **allows** the extra current to flow, in order to be needed

your alt or other charge source produces over 20A

AND

that charge source is going directly to your little Starter rather than House that needs it

AND

your House is big enough that it demands Bulk cycle amps over 20 for a time longer than you want to run that source

AND (

The voltage drops too much over distance,

OR

your target bank has a different voltage due to its chemistry
)

If they both take the same voltage, just run your big current source directly to House and the Starter will never need over 20A

 

[John61CT]

I could go simple and just get a $25 c. duty solenoid (85 amp) with a 100 A fuse and some 4 guage cabling and call it good. I just did not think that's going to cut it (for 100% SOC) and dont want to kill $200 in batteries in a year.

Your method for isolating/combining is just one small part, and in fact should only affect your cheap starter, see above.

Still aren't getting from 50 to 100% on a big bank made of normal lead in less than 5 hours of charging, more likely 8. Ideally that's first a big fossil fuel source in the AM, followed by a long sunny day with panels.

Start with pairs of cheap EC2s, maybe $200 each, if you make them last over four years then consider better quality to get maybe ten.

 

[sushidog]

One thing I don't think anyone caught yet, is that if you have 2 6v CG-2s you need to wire them in series to get 12v. If you wire them parallel, as you suggest, you will only have a 6v bank. This means that the AH capacity of the battery bank, wired in series, will be the same as one of your batteries, not double. You would need 4 - 6v batteries (2 in parallel and 2 in series) if you want twice the AH (400+) at 12v.

Chip

 

[John61CT]

yes, two 245AH 6V cells = one 12V battery at 245AH

four cells needed to get 12V at 490AH (245 usable)

 

[galladanb]

Spaceman Spiff, You said...
"I am usually at 100% (Trimetric calibrated by S.G.) by 1PM."

PLEASE for all of us newbie solar whore wannabe not yet starters, PLEASE, PLEASE explain this statement in much agonizing detail?

For instance, I don't know the following:
1.) How to tell when I'm at 100% SOC or state of charge?
2.) The "Trimetric" is a meter of some sorts? If I buy a Renology package that comes with the MT-50, Is that the same thing?
Will I need the Trimetric separately, will it work with my Renology components?
3.) How do I "calibrated by S.G." ? I'm assuming this means Specific Gravity from a hydrometer? I bought one, and I admit I don't know how to use it?
Also, how do I correctly use it to get the readings, AND how do I then plug those numbers back into the meter?
4.) When you say "by 1PM." Again, I assume you mean solar charging? from dawn to 1PM?

I respectfully apologize for being a putz and or a numb nutz, and I am not challenging you or anyone else, I just don't understand all the Jargon and lingo, and then how to use the info given... For instance when someone says "Just divide it" that sounds simply enough, but maybe the person on the other end of the directive does not know how to divide, the direction is almost meaningless without further detailed instruction.

I've been reading a lot of posts in this and other forums since October, and I am learning at a pace I never in all of my formal education prior...
I am not the sharpest knife in the rack nor am I the butter knife...

Just seeking clarity and knowledge! Thank You all so much for this!

 

[Spaceman Spiff]

For instance, I don't know the following:
1.) How to tell when I'm at 100% SOC or state of charge?
2.) The "Trimetric" is a meter of some sorts? If I buy a Renology package that comes with the MT-50, Is that the same thing?
Will I need the Trimetric separately, will it work with my Renology components?
3.) How do I "calibrated by S.G." ? I'm assuming this means Specific Gravity from a hydrometer? I bought one, and I admit I don't know how to use it?
Also, how do I correctly use it to get the readings, AND how do I then plug those numbers back into the meter?
4.) When you say "by 1PM." Again, I assume you mean solar charging? from dawn to 1PM?

First off you are not a putz or numb nuts for asking good questions!  We all were at your stage of learning solar at one point.  It is amazing how 'I want to do this' enhances learning.  I apologize for being terse in my above answers but I didn't want to get too long winded.

Second, if you haven't read handybob's blog, it would be worth your while:  https://handybobsolar.wordpress.com
It is a difficult read because he rants a lot but it has a wealth of info on RV solar battery charging.  I had to read the 'RV Battery Charging Puzzle' four times before it started to sink in.

  Now to your questions:

1)  The metric I use to determine state of charge is the specific gravity of the electrolyte in each cell of the battery.  When I first got my batteries I charged them up overnight with a battery charger and did an equalizing charge on them (a controlled overcharge to stir up the electrolyte), let them rest overnight and then measured specific gravity with a hydrometer.  Mine measured out at 1.275 to 1.285.  I consider this as fully charged.

2) Trimetric is shorthand for the Bogart Engineering Trimetric 2030 RV Battery System Monitor.  It is basically an amp counter; it keeps track of all the amps going into and out of your battery and does some basic statistics on the data.  Not sure about the MT-50.  from a cursory look at its manual it provides similar information, but I don't know how it gets it.  The Trimetric not charge controller specific.  It should work with any solar/battery system.

3)  The following will explain better than I can:
http://ezgo.smartmanual.biz/using-a-hydrometer/using-a-hydrometer_en.html
http://support.rollsbattery.com/support/solutions/articles/4347-measuring-specific-gravity
The Trimetric (or other meter) will give you instructions on how to tell the meter your batteries are at 100%.  This is important: you are calibrating the meter and its output is only as good as your calibration.  I got a good reading on my batteries when I first got them (see #1) to initially set 100%.  For the first month I tested weekly, then monthly; now I test 4X a year (I do check water levels every month).

4)  When I get up in the morning my batteries are at their lowest state of charge: usually ~80%.  What I mean 'by 1 PM' is that my batteries are at 100% (Trimetric reading) by early afternoon.

I hope I have been clear in answering your questions.  If not you can ask again.  I'm sure others will chime in with clarifications (and confusions ) to your questions.

A good sight for learning about batteries:  http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

 -- Spiff

 

[WalkaboutTed]

^^^Above for other answers^^^


My evolution into a solar whore began when I decided that I just want more, then even more solar watts than I had originally planned. At first, I figured that I would be happy at 100 watts, using an an icebox, no refrigerator. With 100 watts, I could run my lights and charge my laptops and other small devices.

Then I realized that I wanted a fridge-and a badass, power gulping 4.2 cubic ft one.

Then I decided that I wanted to bring my 800 watt k-cup coffee maker.

Then Hub said that he wanted to watch TV without having to watch every watt.

And from there, our electrical desires kept increasing. I finally decided that we could live without the the coffeemaker so we could use a rice maker. I was able to find a 310 watt little Panasonic cooker and took it from up there. Our current configuration would be fine with good sun. I wasn't satisfied with that. If the weather sucks and we're inside, we'll want to run our electronics even more. With the extra 165 watts solar, we will have more flexibility with our power use. 545 watts should do it.

I am a solar whore.
Ted

 

[user 37446]

The SmartPassonly **allows** the extra current to flow, in order to be needed

your alt or other charge source produces over 20A

AND

that charge source is going directly to your little Starter rather than House that needs it

AND

your House is big enough that it demands Bulk cycle amps over 20 for a time longer than you want to run that source

AND (

The voltage drops too much over distance,

OR

your target bank has a different voltage due to its chemistry
)

If they both take the same voltage, just run your big current source directly to House and the Starter will never need over 20A

All correct, for some reason some people want the convenience of the multi-stage charging 12v system with its built in mppt controller. They seem to be the 4x4 folks who have a dual battery system and the smartpass or CTEK under the hood, instead of 10 feet away like I would have to wire.

 

[user 37446]

One thing I don't think anyone caught yet, is that if you have 2 6v CG-2s you need to wire them in series to get 12v. If you wire them parallel, as you suggest, you will only have a 6v bank. This means that the AH capacity of the battery bank, wired in series, will be the same as one of your batteries, not double. You would need 4 - 6v batteries (2 in parallel and 2 in series) if you want twice the AH (400+) at 12v.

Chip

Ha ha, good catch. Anyone who has read these threads for a year and a half like me shouldn't have made that sort of mistake, but then, I know me... 

Maybe that was an intentional error to see if anyone read it closely (nice try...)