2nd Battery and solar choice -- more questions

[Joe917]

It is not a case of just failing. 14 volts is not the correct charging voltage. Usually these cheap units do not give you the option to set the voltage, 14.8v for flooded lead acid.Temperature compensation is also a must. You spend money on a system then waste it with a crappy controller. Displays on charge controllers are a waste since:
They need to be places as close to the battery bank as possible (usually making them hard to access).
And You should be using a battery monitor that will give you any information the charge controller would.
They are not built to be installed outside or in the battery compartment. Morningstar controllers have millions of miles on the road.

 

[calicamper]

Yes 14.8 to be exact and temp monitoring etc, all things my simple $27 unit does, no joke its all the same stuff my high end marine unit does on my boat. If we were talking 5yrs ago I would say yes big difference but today, no not from what I'm seeing. Just pointing out I dont think there is a big gap in quality between $200 and $30 controllers today. For the price I consider it worth a try. There are far far more $30 controllers being used today to manage off grid power needs than $200 controllers that is for sure. Every lamp pole at work is running a $30 controller and they rarely have issues.

Just sayn..

By the way the LED stuff and the cheap solar stuff these days makes for pretty fun power projects.

 

[AndrewP]

Why spend money on a charge controller? Because that $27 made in China won't be the only thing you have to replace after you let it loose on your battery bank. Chinese build quality is a function of the build specification, usually something specified by Walmart to be as cheap as possible. No wonder its mostly rubbish. Do your research, invest in quality, do it once.
While we're at it you are missing the most important part of the system : a battery monitor. Not a voltmeter, they are useless for SOC in a working system. You need to add a true amp/hr counting monitor to know what your system is actually doing. Trimetric or equivalent.

I think many of your concerns apply to larger and more expensive installs-like a full time RV, or a big boat. For off road use, where carrying more than 2 normal size batteries is difficult, you can get by without crazy money equipment like watt counting battery monitors and MPPT controllers. You can be practical where Morningstar PVM controllers are outstanding value, and voltmeters give a decent idea about state of charge. Or, you can throw $1000 worth of electronic monitors, chargers and controllers at what is basically a low power 2 battery system. I agree with CaliCamper in this regard-it isn't worth it.

The original poster has a small truck and wants to do a nice job of running an engine battery and a house battery. Unless I read it wrong, he isn't looking for a massive battery bank and 600 watts of solar.

 

[dwh]

They mention that this the only 'true deep cycle' battery available on the market.

Wait...what? Who said that?

It's not true - there are TONS (yuk it up guys, that was a pun) of deep cycle batteries on the market. One of the most popular for decades has been the Trojan T-105 series.

 

[calicamper]

Wait...what? Who said that?

It's not true - there are TONS (yuk it up guys, that was a pun) of deep cycle batteries on the market. One of the most popular for decades has been the Trojan T-105 series.

Yup

 

[calicamper]

I think many of your concerns apply to larger and more expensive installs-like a full time RV, or a big boat. For off road use, where carrying more than 2 normal size batteries is difficult, you can get by without crazy money equipment like watt counting battery monitors and MPPT controllers. You can be practical where Morningstar PVM controllers are outstanding value, and voltmeters give a decent idea about state of charge. Or, you can throw $1000 worth of electronic monitors, chargers and controllers at what is basically a low power 2 battery system. I agree with CaliCamper in this regard-it isn't worth it.

The original poster has a small truck and wants to do a nice job of running an engine battery and a house battery. Unless I read it wrong, he isn't looking for a massive battery bank and 600 watts of solar.

Not to mention there are "Zero" solar related products made today that do not contain nearly all china sourced components. Your only fooling your self if you think your getting a product that isnt made in or does not contain a majority of its components from china. The only US based built solar product are panel mounting systems racks. China killed solar product competition by under cutting everyone else via labor costs and GOV subsidies while no one thought to levy import duties to level the playing field.

 

[Dust999]

Another question...

Instead of using the ACR 7622 and a solar controller, either a PWM or MPPT, has anybody here used this DC to DC charger from CTEK?

CTEK D250S Dual. Isolates the battery, is a MPPT solar controller, boosts voltage (for what it's worth for my needs). Seems a much simpler setup.

 

[dwh]

Several people here on ExPo have the CTEK. I have seen a few rave reviews and no bad reviews. One caveat - it's bigger than it looks in the pictures. Another caveat - without the added SmartPass unit, it'll only do 20 amps from the engine side to the aux side. Another caveat - watch the input on the solar, it's limited to 22 Voc max even though the built-in charge controller is an MPPT unit.

 

[calicamper]

Several people here on ExPo have the CTEK. I have seen a few rave reviews and no bad reviews. One caveat - it's bigger than it looks in the pictures. Another caveat - without the added SmartPass unit, it'll only do 20 amps from the engine side to the aux side. Another caveat - watch the input on the solar, it's limited to 22 Voc max even though the built-in charge controller is an MPPT unit.

Dw is that 22 volts solar max? Just checking

Curious given I was shocked to see my super small panel hit 19.5 volts for about two hours on a clear 80 degree day, I was not expecting it to generate that much voltage.

 

[Dust999]

Several people here on ExPo have the CTEK. I have seen a few rave reviews and no bad reviews. One caveat - it's bigger than it looks in the pictures. Another caveat - without the added SmartPass unit, it'll only do 20 amps from the engine side to the aux side. Another caveat - watch the input on the solar, it's limited to 22 Voc max even though the built-in charge controller is an MPPT unit.

With the smartpass addition will I get the batteries to charge faster? i.e., I need to drive less or have less solar exposure?

 

[dwh]

Dw is that 22 volts solar max? Just checking

Yea, if I recall correctly, that's open circuit.

Curious given I was shocked to see my super small panel hit 19.5 volts for about two hours on a clear 80 degree day, I was not expecting it to generate that much voltage.

It did that because the battery voltage was high and the PWM was spending more time with the solar disconnected from the battery than it was spending with the solar connected to the battery.

PWM is just a really fast computer controlled on/off switch. With a switch, when the solar is connected to the battery, the solar will be operating at battery voltage. But with the PWM fast switching, the duty cycle (time solar spends connected to battery) can be regulated, which moves the voltage readings around a bit.

Say with a solar panel with a 20v open circuit (Voc). If the PWM spends say, half it's time (50% duty cycle) with the solar connected to the battery, then the voltage is going to fluctuate between battery voltage (say 14v) and solar Voc (20v). So the average that you'd see if you measured at the solar panel will be around 17v. The reason you see the "average" on the meter, is because the PWM switches a lot faster than the meter can respond, so you don't actually get to see the solar voltage jumping back and forth from 14v to 20v a few hundred times a second.

The fact that your meter was reading 19v indicates that the PWM was spending most of it's time with the solar disconnected from the battery (it was operating at maybe a 5% or 10% duty cycle).

 

[dwh]

With the smartpass addition will I get the batteries to charge faster? i.e., I need to drive less or have less solar exposure?

Theoretically. I think it can do 80 amps or some such.

But that's only theoretical. The actual amps flowing will depend on the battery's resistance + the resistance of the wire. You might get an 80a peak for a little while, and then it tapers off as the battery voltage rises. So depending on the situation - for instance you don't drain your battery much - you might not shave much time off the charging cycle by having the SmartPass.

 

[calicamper]

So it looks like the CTEK acts as a battery monitor/tender which you power off your car battery to manage your isolated 2nd battery, I wonder if a second solar controller could simply be set up between the Solar Panel and the secondary battery, thus your getting charge options from two sources?

I just pulled out the specs on the solar charger unit I have. In theory it could care less where the power comes from, so solar power or car power. Its max pv voltage limit is 40volts. Max charge current is 20amps. I think all of these small units are capped at 20amps, even my shore power unit on my boat runs at 15amps. So there is probably a amp limit on the typical power load placed on your typical 12volt system to avoid battery damage.

From the looks of it these units all work in the same manner they handle a range of source power and manage the battery status on the other side.

 

[calicamper]

Ok interesting read
From what I can tell amps pushed to the battery as a general rule you want 25% or less of the batteries amp hour rating or you can cook it given it cant absorbe the amperage ie charge fast enough. This also is dependant on the battery type and its quality etc. So it sounds like for the most part you cant just dump a big amperage on the battery. More amps = less charge time up to a certain point.
http://www.chargingchargers.com/tutorials/12-volt-charger.html

So my little 18ah battery I dont want to exceed 4.5 amps on the charge. So it wouldnt do me any good to boost solar panel capacity beyond a 80watt panel, unless!!! I'm powering something else or rarely see good solar conditions, given a 80watt panel flat out can get into the 4amp range, but poor conditions its a 1amp source.

 

[DiploStrat]

It takes a LOT of reading to get to to a real description of what the SmartPass (http://smartercharger.com/products/dcdc/ctek-smartpass/) actually does, but basically, it is an intelligent relay (like the Blue Sea ACR) but engineered to work with the D250S B2B. Basically, when you start the engine, it closes the relay to put the batteries in parallel. When the bulk stage is complete, that is, when the charge rate drops to about 20A, then it opens the relay and completes the absorb stage using the D250S alone. As noted, the D250S doubles as a solar controller.

dwh has mentioned the caveats of size and cost. But if your alternator doesn't charge above 14v, this might be a slick solution.