Perpetual Motion

[tknight]

Ok, heres my idea, battery gurus please feel free to chime in on this one........
I have in my st8 truck freightliner m2 starting batteries, 2 of them about 2 years old now, I also have 2 gel cell 250 ah "house batteries" these are hooked up to an automatic relay that connects the house to the starting batt system so they get a full charge while I'm driving, I use this for my electric blanki and phone/ipad power while i sit waiting for the next adventure. I can get about 12 hrs of blanket in the winter, in the summer I can get days of use, if needed when freight is super slow. . So now comes the hair brained plan for the winter while truck is parked and I don't have 120v available for my charger/maintainer, (it puts out 6 amps trickle charge, works great on the 2 starter batts, I was wondering now, holld on boys and girls if I can made my electric system self charging. I propose to hook the charger up to my inverter and connect it into the starting batts to keep them topped off during the cold nights, I figured the following charger uses 72 watts @ 120vac, plugged into the inverter which will place a draw of about 6 amps per hr on them. I theoretically should get a decent amount of hrs of "parked charge"
So here I am wondering if this will work, not wanting to burn my truck down due to an electrical malfunction. The house batts will recharge when the truck is started and running all day again, so the cycle keeps repeating itself, hence perpetual motion.
Sorry it long winded but I wanted it made clear as to my intentions.

Happy new year to all, and to all happy motoring............

tk

ps, both battery banks are fully isolated from each other except when motor is running, in addition to the automatic swicher, i also have a manual disconnect switch I can throw while parked to assure complete isolation.

sent from my ipad, so forgive any wierdness, other than my normal self.

 

[paullud]

If I understand you correctly you are trying to use all 4 batteries. You could always just not isolate them but that could lead to draining the batteries to far, unless you are careful. The inverter will help prevent that but it will also have an amp draw along with the charger.

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[xiggi]

I think he wants to keep his starter batteries charged up while sitting using his aux batteries.

Sent from my Fisher Price - ABC 123

 

[tknight]

Right I thought that was clear!!

 

[tknight]

Last winter I tried plugging in my block heater to the 2 house batts didn't seem like it did anything except drain em off faster than I liked

 

[paullud]

So you want to charge your ipad, run your blanket, and charge the truck batteries off of the house batteries? Why do you want to charge your starting batteries if there is little to no draw?

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[tknight]

The cold nights always make for a harder to start truck thick oil and all better safe than a 100 dolla jump!

 

[Rocketman]

The cold nights always make for a harder to start truck thick oil and all better safe than a 100 dolla jump!

But, you'll be drawing down your house bank to do this correct?

You'll mainly be transferring charge from one set of batteries to the other. It seems like there would be a simpler way to do that?

 

[tknight]

drawing down the house is no big deal they are both 250 amp hr batteries tied in parallel
, they will recharge when the motor is running, as I live way out in the country and have to park at the end of my drive by the road there is no electric to plug in the truck on those really cold days, my house is a 1/2 mile down the drive, thats a mighty long extension cord..........

 

[zorry]

Buy an APU. ARI wires the block heater directly to APU and puts a lighted on/off switch in the bunk.
On a cold nite just flip the switch, reachable from the dinette or bed.
You and the truck stay warm, your batteries last longer.
You feel better so you're probably more productive.

 

[cheri1122]

I'm waiting for the acknowledged battery guru Turtle to respond - but meantime, I'd suggest a $20 investment in a voltage meter that monitors the battery power available. [Also measures usage draw of various gadgets & 'stuff']
I've found them only online, but it's worth the $20, definitely - beats needing a jumpstart.

 

[zorry]

About $17 at Walmart.

 

[cheri1122]

Zorry, do you mean the kind that checks the voltage, or constantly monitors it? I have only found the first kind at the brick & mortar stores.....at least in a 12v version, not plugin/ AC.

 

[tknight]

zorry, wanna give me about 8 grand? i'm fine without the apu!

 

[xiggi]

You said you have a switch in addition to your isolator. I believe you can get a perko switch that can be turned to allow starting power from all batteries when needed. Might be a better option.

Sent from my Fisher Price - ABC 123

 

[zorry]

I could spot you the 8, but if you don't need the APU, you probably don't need the $$.
Cheri, what Walmart sells monitors the constant Voltage. 13.8-14.5 while running and actual voltage when in off position.
You can see how quickly your batteries loose charge. Also if you need to change something as your voltage is dropping too low.

 

[Turtle]

First, charging one battery from another is certainly possible. It's incredibly inefficient, but it's possible.

Second, and perhaps my most important questions, why would you put gel batteries in a vehicle and then have the alternator charge them? Gell batteries are awesome for boats, but between Gel, AGM and wet cell, gel is the way worst for a car, van or truck, unless exacting provisions have been made to keep them properly charged.

Gell batteries require strict voltage regulation as per the manufacturer's specifications. a couple of tenths of a volt high or low, just one time, and gel batteries will have a dramatically reduced capacity and lifespan. If they are charged at too high a voltage, as can certainly happen in hot weather with an unregulated charging source (unregulated insofar as being regulated to the tight specifications of a gel battery), then as with any battery, but especially with a gel battery, you can encounter what is known as "thermal runaway" where the battery gets hot, really hot, and keeps getting hotter, until you experience a genuine adventure. It's very important with gell batteries to only charge them with a temperature compensated, constant potential, voltage-regulated charger. For Trojan gel batteries, for example, you should charge to at least 14.1 volts but no more than 14.4 volts at 77°F (25°C). At 85°F the max voltage drops from 14.4 to 13.8. A standard automotive battery charger is not designed and regulated for gel batteries, and a truck or car alternator even less so.

Also, instead of a voltmeter for high dollar gel batteries, you should get a $150 Xantrex or TriMetric Battery Monitor, rather than relying on a $12 voltmeter to tell you the state of your batteries.

Finally, as someone has already mentioned, if you are parked and not drawing anything from your cranking batteries, there is little reason to top them off overnight. Self-discharge overnight, even in cold weather, shouldn't have any effect on starting the vehicle, unless the batteries aren't healthy to begin with. If they aren't healthy, they need to be replaced.

One statement that gives me pause is, "I can get about 12 hrs of blanket in the winter..." Uhm, 12 hours before what? Before the inverter starts screaming because you've discharged the battery down to way below what the inverter requires? Be it known that resistive heat applications, such as heat and air conditioning, are the worst way to use a battery. However, most electric blankets will draw between 5-7 amp from a battery bank. Even at 7 amp hours, you should be able to go 30+ hours with a 480 AH battery bank (a pair of 240 AH batteries) and still not get down to even 50% DoD. So I pause at only 12 hours....

But the bottom line answer is, sure, you can trickle charge your cranking batteries with your house bank. If it's a 72 Watt charger, it'll draw 7 amps, not 6, through the inverter, though. A charger and an electric blanket at the same time, now you're in the 15 AH range and the Perkert Effect comes more dramatically into play, so runtime will be lessened as available AH will be reduced.

 

[cheri1122]

I could spot you the 8, but if you don't need the APU, you probably don't need the $$.
Cheri, what Walmart sells monitors the constant Voltage. 13.8-14.5 while running and actual voltage when in off position.
You can see how quickly your batteries loose charge. Also if you need to change something as your voltage is dropping too low.

Do you know what the brand name is? Because I searched WM and Menards and Lowes, etc, looking for it, and found only the plugin AC version, while the one I ordered online is a 12v kind, which is what I want.
I'm not gonna blow $150 on it, but I don't have gel batteries, either.

 

[zorry]

I'm out of the truck for a week or two. Will look when I get back.
I've bought three in the last 12 months at three different Wal-marts.
One had a cig lighter plug and the head sat infront of the outlet.
The last two I bought have the cig plug and a short (24") cord so you mount it elsewhere.
They will be near the batteries on a bubble card. Usually hanging on the shelf bracket of the end of aisle shelving.
Ask. If the say no, ask again.

 

[Turtle]

Do you know what the brand name is? Because I searched WM and Menards and Lowes, etc, looking for it, and found only the plugin AC version, while the one I ordered online is a 12v kind, which is what I want.
I'm not gonna blow $150 on it, but I don't have gel batteries, either.

For most people, a simple voltage monitor is all they need to monitor their cranking batteries, especially if they run small inverter loads off their truck batteries. Walmart has three of them, Equus Innova 3721 Battery Charging System Monitor, the Schumacher Battery Monitor, and the Everstart 932W Digital Battery Monitor.

This one is a little better than those: Battery Low Voltage Alarm

This one is a lot better. Priority Start 12 Volt ProMax