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Old 09-20-2016, 04:03 PM   #11
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I had the same conundrum. Knowing that the house and starter were different and paralleling was maybe not optimum.

However, I think a good solar system with good charger solves many house battery issues and is better for longer term storage as you keep those AGM's frosty. Alternator for bulk charging, solar to finish the job and provide for loads during the day.
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Old 09-20-2016, 04:15 PM   #12
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The 7622 is basically a automatic switch that monitor voltages on both sides of the terminals, the starting battery/alternator side and the house battery/solar/shore charger side. Voltages are monitored (on both sides) and if the separator sees a low voltage of 12.8 (on either side), it sends a command to open. Same is true for higher voltages (sometimes referred to as charge voltage) that hover around the 13.3 or higher range. If the separator sees a 13.3 volt jump (on either side) when a charge voltage in introduced, the separator closes. When closed the charge voltage from the alternator, solar or shore charger charges all batteries on board.

Most of us are running 12v AGM house systems. A diesel has twin batteries due to the starting amperage and how those engines operate, those batteries are paralleled. So are those who use multiple 12v house batteries. The separator simply protects one bank from discharging the other. The reason I had two house batteries installed is because most of what is used in the conversion is often used w/o any charge plus I factored in my anticipated loads during the evening hours.

So if you have a spot light that pulls about 8 amps and you plug it into one of the 12v power ports that is hooked up to the house side (with no charge applied), eventually the house system will be drawn down to the 12.8 state and the separator will open. If a charge is applied to either side (from the alternator/shore charger/solar, it doesn't matter) the separator closes when it sees 13.3 or higher and begins to charge both starting and house battery systems. There is no voltage regulation applied by the separator. The same is true if you leave your headlights on. The separator sees the starting batteries begin to drop from their fully charged state and as soon as it sees 12.8, the separator opens so the house batteries aren't being drawn off of. The 7622 (and many others) can be manually closed to help jump start the vehicle. It's also why you need a fairly heavy sized wire that can handle starting the vehicle from house system... long crank times can melt down wire that is too small.

Batteries simply draw what they need depending on the state of discharge they're in (provided they are in a good state of health). It doesn't matter how many batteries are put into the loop or if one bank is more discharged than another. Once the higher charged bank is nearing a full level, more amperage is available for the deeply discharge battery system. The problem with most alternator regulators is they only supply about 80% of the charge. Solar helps to top off the batteries to a true fully charged state. Most Shore chargers also do the same.
Most all batteries are really only a series of cells paralleled together. If one cell in a battery fails, the whole battery fails. Same is true with batteries that are banked together...if one battery fails it takes its partner(s) down. I haven't seen a need to install a separator between the 2 house batteries I have and just rely on keeping it simple. Instead I try to monitor the charging and battery voltages often. Usually if a bad battery is in the loop, charging characteristics change and I'll see that before heavy damage occurs. One thing I had an issue with was using a maintenance free starting battery with Lifeline batteries. Seemed like the daily solar, even with it's lower amp charging was over charging the starting batteries. After I switch to AGM batteries, the problem went away...but I have no true evidence of this, only what the difference was after I installed the AGM starters. Still the two AGM battery systems have slightly different charge voltage specs, but they're close. I turned down the Solar controller voltage to match what Concorde (Lifeline) told me to do. I also installed an alternator regulator that supplies a smart charge via the alternator. If you have a battery system that requires a specific charge voltage like gel or Lithium batteries, for the most part you wouldn't want the two systems to automatically connect during a alternator charging session unless the manufacture says the batteries can take it. I learned the hard way with gel batteries.
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Old 09-20-2016, 08:39 PM   #13
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Thanks guys! Dave, that really helps explain things for me - much appreciated! It looks like for my needs, a new lithium capable charger/converter in conjunction with the bluesea 7700 should work fine. I've got a portable solar system that I've simply been clamping onto the house battery side of the isolator, so it looks like I can use that to top off the batteries while off-grid just the same as I have been, even after a switch to lithium batteries.

Thanks again!

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Old 09-20-2016, 09:34 PM   #14
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Let's go for a really simple explanation......

In a typical circuit the resistance of the load (lightbulb, starter motor, etc) determines the current out of the whatever is supplying the juice.

Think of it this way....two water faucets, one is fully open the other is half open.....the fully open faucet results in twice the flow as the half open faucet....or twice the current...assuming there is enough pressure (voltage) to keep everything flowing as designed.

A discharged battery has a lower resistance than a charged battery so for a given voltage, it draws more current, since the resistance of the load determines the current.

In the above case the alternator, or solar system, or shore power provides the juice and the battery is the load.

Here is another simple analogy....let's take a water tank mounted to the ceiling connected to a tank several feet below........

now let's poke different sized holes in the lower tank......

the larger holes will leak more water (current) than the smaller holes since they have less resistance than the smaller holes to flow, even though the pressure (voltage) in the lower tank is the same for all of the holes.

.......so if you have a bank of 10 batteries wired in parallel, and a voltage source like an alternator, the batteries with the lowest state of charge will draw the most current since they will have the lowest resistance.
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Old 09-20-2016, 09:51 PM   #15
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daveb

would like to know a little more about your solar charge controller and alternator charge controller......or at least which ones you are using.

My plan right now is to go stock alternator (135 amp), Blue Sea 7622, Lifeline 4D, and a 200 Watt solar system. Not sure what solar controller yet, maybe a Midnite solar KID, but an MPPT charger for sure. My house loads shouldn't exceed 20Amps.

I'm just very curious about dialing it all in. I don't understand alternators all that well, other than they crank out 14.4 volts?? But I am learning.
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Old 09-20-2016, 10:02 PM   #16
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Quote:
Originally Posted by boywonder View Post
Let's go for a really simple explanation......

In a typical circuit the resistance of the load (lightbulb, starter motor, etc) determines the current out of the whatever is supplying the juice.

Think of it this way....two water faucets, one is fully open the other is half open.....the fully open faucet results in twice the flow as the half open faucet....or twice the current...assuming there is enough pressure (voltage) to keep everything flowing as designed.

A discharged battery has a lower resistance than a charged battery so for a given voltage, it draws more current, since the resistance of the load determines the current.

In the above case the alternator, or solar system, or shore power provides the juice and the battery is the load.

Here is another simple analogy....let's take a water tank mounted to the ceiling connected to a tank several feet below........

now let's poke different sized holes in the lower tank......

the larger holes will leak more water (current) than the smaller holes since they have less resistance than the smaller holes to flow, even though the pressure (voltage) in the lower tank is the same for all of the holes.

.......so if you have a bank of 10 batteries wired in parallel, and a voltage source like an alternator, the batteries with the lowest state of charge will draw the most current since they will have the lowest resistance.
DUDE! Thank you!!!! This makes sense.

I was really feeling like there must be some basic underlying "essential natural/physical behavior" of all batteries that governs how the charging voltage (or rather, as you're stating, the current.....) meters itself through the cells during any charging. (And less so the idea that some sort of sophisticated electrical component is always in the loop that "senses" how much current a battery needs and adjusts it accordingly.)

This is what I was slowly reasoning my way towards....was talking to capnkurt earlier today, and theorizing that a discharged battery must act like a relatively-low-resistance circuit.....and that as it nears a state of being charged, it must start to increase in resistance. When it's empty, it's hungry for current....as it nears full, not so much so.

(I was thinking that perhaps that very slowly-increasing battery resistance was what signaled to "smart chargers" (very likely!) or voltage regulators (not correct, I can see) to begin to taper off its current or voltage....)

Yeah this is cool.
Despite remembering my high-school physics equations P=I*V and V=I*R.....I'm primarily a visual guy (I think a lot of us "hands on" kind of guys/girls are....I draw pictures of cars for a living...)....and having visuals like you shared truly helps to make sense of all this stuff.

Thanks so much boywonder!
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Old 09-20-2016, 10:29 PM   #17
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.......theorizing that a discharged battery must act like a relatively-low-resistance circuit.....and that as it nears a state of being charged, it must start to increase in resistance. When it's empty, it's hungry for current....as it nears full, not so much so.

I draw pictures of cars for a living

.
exactly......

Are you an industrial designer?
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Old 09-20-2016, 10:50 PM   #18
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Are you an industrial designer?
Yepper!!!
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Old 09-20-2016, 10:56 PM   #19
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daveb

would like to know a little more about your solar charge controller and alternator charge controller......or at least which ones you are using.

My plan right now is to go stock alternator (135 amp), Blue Sea 7622, Lifeline 4D, and a 200 Watt solar system. Not sure what solar controller yet, maybe a Midnite solar KID, but an MPPT charger for sure. My house loads shouldn't exceed 20Amps.

I'm just very curious about dialing it all in. I don't understand alternators all that well, other than they crank out 14.4 volts?? But I am learning.
I'm using an older Blue Sky controller. This industry changes so frequently I'd hate to send you in the wrong direction. I'd be asking those who have recently purchased and have researched the matter.

FWIW I am not running Lithium batteries and is where this thread seems to be going. My alternator is an XP-270 with a Bal-mar smart regulator set up by Nations alternator. I was worried the regulator (remotely mounted) would not like the engine bay heat. They say no but it kept me from going this route earlier. Anyway the shop was able to mount it inside the cab and I love that. There are several charging options to set it to. I had the largest stock alternator from Ford and it just couldn't handle the loads. I actually lost house battery reserves when driving at night with the Starcool running. Huge difference when I upgraded to the XP-270. I've only been running the Bal-Mar for a few months but is is nice not seeing 14.4 volts at the house battery when the batteries were already full. IIRC Lifeline says about 13.5 or so is the float voltage to meet.
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Old 09-21-2016, 01:11 AM   #20
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That's a heck of a nice alternator setup and thanks for the info. I am gonna bookmark this thread for future reference. I was thinking of oversizing my cables to handle at least 200 amps from alternator to house for future alternator upgrades. I appreciate the info very much. I will get all this straight in my head. One thing would be to just switch the house off until it's drained enough to deal with the stock "dumb" alternators 14.4 volt charge. I guess I need to look into the profiles a bit more.
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