Charging the House battery while driving

[Lisahi]

Hello!  What's that thing under the hood that diverts (?) some of the charge to the house battery as the vehicle is driving - a selenoid?  Is it always charging the house battery while driving or does it have a switch to charge the house battery only when you want it to?  I ask because I probably will usually only be driving around with the house battery on my road trips, but for day to day minivan duty, I'd like to remove it from the van.  Which brings me to question #2:  I think I read that when the house battery is disconnected from the cables which have been run into the cabin, each terminal (?) needs to be insulated away from anything else, via a bicycle tube piece I think Bob Wells suggested?  #3:  is there a size range for the cables that run from under the hood into the cabin?  And finally (for now) #4:  those battery boxes - seem like a good protective idea.  Do they allow easy access to the battery?  Thank you!

 

[TMG51]

1. The solenoid is a switch, really. It just does the switching all on its own. When you start the car, current passes through the solenoid which magnetically causes a switch to flip and start charging your house battery. Turn the car off, switch turns off.

2. Any cables you buy should be insulated, but, the positive lead should never touch anything else since the whole car body is a negative ground (it makes a dead short to touch positive to the car body). Because of this, it's a good idea to protect the ends of the cables as well as anywhere insulation might rub due to vehicle vibration. The bicycle tube sounds like a good option to that end.

3. Basically, bigger is better. But it's also harder to run thick stiff wire.

4. If you have a good place for one!

 

[BigT]

Maybe you can simplify the system like I did and remove the OEM battery from under the hood and replace it with a Northstar AGM deep cycle unit.
It performs very well as both a starter battery and a house battery.
Of course if you're running multiple house batteries this won't work, but if you only need one, then this might just do the trick.

I really enjoy the simplicity of not having to wire a second battery to the system, potentially overloading the charging system. It's really "Plug-N-Play".

 

[Lisahi]

Maybe you can simplify the system like I did and remove the OEM battery from under the hood and replace it with a Northstar AGM deep cycle unit.  
It performs very well as both a starter battery and a house battery.  
Of course if you're running multiple house batteries this won't work, but if you only need one, then this might just do the trick.  

I really enjoy the simplicity of not having to wire a second battery to the system, potentially overloading the charging system.  It's really "Plug-N-Play".

Hi Big T:  Well, I don't know a lot about the electrical use/needs part yet, I'm still trying to figure it all out, so here's a maybe too simplistic question:  I really like the idea of one simple battery, but would that type of battery, the Northstar, run a small 12 volt refrigerator for say three days, with the addition of some solar panels?  And would the solar panels replace the charge in the Northstar? Don't want to have to drive around just to keep the fridge chilled, but do like the idea of not having to lug (and store) the house battery around when it's not in use.  Thank you.

 

[SternWake]

I am using only a single 90Ah group 27 northstar battery, and have 200 watts of solar, and running my 1.8 cubic foot/51 liter vitrifrigo 12v compressor fridge is never a concern.

FOr just the fridge, I could likely get away with 60 watts of solar, but I use a lot of laptop too which is a real power hog.

My fridge consumes usually well less than 1Ah every hour, My laptop will consume no less than ~3.5AH in an hour, and if the laptops battery is depleted, this can easily double.

In june It will be one year since my last 'house' battery got worn out and I started cycling the then 1.6 year old Northstar.

The trick with the Northstar AGM is to be able to high amp recharge it when it is seriously depleted, and fully charge it via solar as often as possible and it will serve you well.

'Full charge' however takes longer than most cheap solar controllers will allow absorption voltage to be held, so more money spent on a programmable controller can significantly extend battery longevity, and the Northstar AGM is ~325$ for a group 27 at 90 AH.

If you go for just a single marine AGM battery under the hood, You might want to carry a jumper pack until you figure out how much juice you really need. Something like this:

http://www.amazon.com/Jump-N-Carry-...8&qid=1463036636&sr=8-13&keywords=jumper+pack

Beware of the jumper packs which have inverters and air compressors as these bells and whistles are usually very poor bells and whistles. The battery in these smaller jumper packs is just a small 12AH AGM battery:

Similar to this:
http://www.amazon.com/ExpertPower-E...e=UTF8&qid=1463036795&sr=8-3&keywords=ub12120
I recommend Never using it for anything but jump starting. Recharge it monthly to keep it full, so it will be there if/when you need it.

That 12AH AGM battery was enough to help start my dodge 318 5.2L v8.

How big a battery you can fit in the stock location underhood is also a big factor if you choose this single battery route. Ideally you would be able to fit this:

http://buy.northstarbattery.com/p/nsb-agm-31-battery

 

[Lisahi]

I am using only a single 90Ah group 27 northstar battery, and have 200 watts of solar, and running my 1.8 cubic foot/51 liter vitrifrigo 12v compressor fridge is never a concern.

FOr just the fridge, I could likely get away with 60 watts of solar, but I use a lot of laptop too which is a real power hog.

My fridge consumes usually well less than 1Ah every hour, My laptop will consume no less than ~3.5AH in an hour, and if the laptops battery is depleted, this can easily double.

In june It will be one year since my last 'house' battery got worn out and I started cycling the then 1.6 year old Northstar.

The trick with the Northstar AGM is to be able to high amp recharge it when it is seriously depleted, and fully charge it via solar as often as possible and it will serve you well.

'Full charge' however takes longer than most cheap solar controllers will allow absorption voltage to be held, so more money spent on a programmable controller can significantly extend battery longevity, and the Northstar AGM is ~325$ for a group 27 at 90 AH.

If you go for just a single marine AGM battery under the hood, You might want to carry a jumper pack until you figure out how much juice you really need.  Something like this:

http://www.amazon.com/Jump-N-Carry-...8&qid=1463036636&sr=8-13&keywords=jumper+pack

Beware of the jumper packs which have inverters and air compressors as these bells and whistles are usually very poor bells and whistles.  The battery in these smaller jumper packs is just a small 12AH AGM battery:

Similar to this:
http://www.amazon.com/ExpertPower-E...e=UTF8&qid=1463036795&sr=8-3&keywords=ub12120
I recommend Never using it for anything but jump starting.  Recharge it monthly to keep it full, so it will be there if/when you need it.

That 12AH AGM battery was enough to help start my dodge 318 5.2L v8.

How big a battery you can fit in the stock location underhood is also a big factor if you choose this single battery route.  Ideally you would be able to fit this:

http://buy.northstarbattery.com/p/nsb-agm-31-batter

Thank you for all the ideas and cautions!

 

[steamjam1]

Hello!  What's that thing under the hood that diverts (?) some of the charge to the house battery as the vehicle is driving - a selenoid?  Is it always charging the house battery while driving or does it have a switch to charge the house battery only when you want it to?  I ask because I probably will usually only be driving around with the house battery on my road trips, but for day to day minivan duty, I'd like to remove it from the van.  Which brings me to question #2:  I think I read that when the house battery is disconnected from the cables which have been run into the cabin, each terminal (?) needs to be insulated away from anything else, via a bicycle tube piece I think Bob Wells suggested?  #3:  is there a size range for the cables that run from under the hood into the cabin?  And finally (for now) #4:  those battery boxes - seem like a good protective idea.  Do they allow easy access to the battery?  Thank you!

A constant duty solenoid. Napa Part # ECH ST85. You can cable it in series to the car battery with the solenoid between, then wire a toggle switch to activate, or wire it to your ignition so whenever you drive, the alternator charges it.

Insulating the cable terminals when not in use is a great idea. You can get high amperage quick disconnects for battery cables that are already insulated.

A standard battery cable will work.

Battery boxes are great.

 

[phillipaaron]

I have a question about this. What prevents the battery from being overcharged?

 

[steamjam1]

I have a question about this. What prevents the battery from being overcharged?

The cars existing voltage regulator.

 

[SternWake]

I have a question about this. What prevents the battery from being overcharged?

A solar controller is nothing but a voltage regulator, granted it is much smarter than the voltage regulator in vehicles which are primarily concerned with not overcharging a battery, and as such are great at undercharging a battery by not allowing high enough voltages for long enough.

Far too many people think that the alternator is some near instant magical battery charger that can defy the laws of physics, but it takes 1 engine HP for it to produce 25 amps, and it takes 3.5 to 4 hours to take a healthy battery from 80 to a true 100% charged, no matter what the charging source is.

When a battery is cycled and not regularly fully charged, its capacity shrinks much much faster and it becomes harder and harder to fully charge what capacity is left, requiring even more time to do so, and perhaps higher voltages too.

So overcharging is rarely a concern in this lifestyle, as long as voltage is controlled to stay 14.8v or below.  More of an issue is a voltage regulator dropping to 13.7v when the battery is still only 80%.
While it might take 4 hours to go from 80% to 100% at 14.4v+,
It will take 8 or more hours to got from 80 to 100% at 13.7v, and it might not even be possible to fully charge it at 13.7v no matter how long the charging source holds 13.7v.

 

[Optimistic Paranoid]

Stern, I would appreciate your checking my logic on something.

I have a Group 31 Odyssey AGM battery I'm going to use as a house battery.  I'm planning on setting it up to recharge from both driving and two 100 watt Renogy solar panels. 

The odyssey manual says it needs to be recharged between 14.1 and 14.7 volts.  I've checked the output of my alternator with my Fluke DVM.  It's 14.35 volts right after I start my truck.  I have a Morningstar Sunsaver controller that comes factory set at 14.4 volts on the FLA setting, but only 14.1 volts on the AGM setting.  However, I can reprogram it with my pc, and I've been thinking about setting it up to deliver 14.7 volts and turning off the equalization.

Now here's the part that's bothering me.  Voltage is pressure.  If the Sunsaver is pushing 14.7 volts into the circuit, won't that keep the 14.3 volts from the alternator from flowing into the house battery?  In fact, seems to me that some of the current fro the panels should be pushed back into the engine battery by the higher pressure, no?

The panels can deliver 10 amps, max, and the alternator should be good for a lot more than that, so I'm thinking I need to wire a relay into the circuit so the solar panels don't charge while the engine is running.

Or am I missing something really stupid here?  Appreciate your thoughts on this.  Thanks.

 

[NeedAnEscape]

If the panels produce enough power to hold the battery at 14.7 then the alternator won't do anything. If the panels can't hold it at the higher voltage the alternator will take most of the load. The solar will still be putting power into your batteries, but the alternator will do most of the work.

 

[SternWake]

Stern, I would appreciate your checking my logic on something.

I have a Group 31 Odyssey AGM battery I'm going to use as a house battery.  I'm planning on setting it up to recharge from both driving and two 100 watt Renogy solar panels. 

The odyssey manual says it needs to be recharged between 14.1 and 14.7 volts.  I've checked the output of my alternator with my Fluke DVM.  It's 14.35 volts right after I start my truck.  I have a Morningstar Sunsaver controller that comes factory set at 14.4 volts on the FLA setting, but only 14.1 volts on the AGM setting.  However, I can reprogram it with my pc, and I've been thinking about setting it up to deliver 14.7 volts and turning off the equalization.

Now here's the part that's bothering me.  Voltage is pressure.  If the Sunsaver is pushing 14.7 volts into the circuit, won't that keep the 14.3 volts from the alternator from flowing into the house battery?  In fact, seems to me that some of the current fro the panels should be pushed back into the engine battery by the higher pressure, no?

The panels can deliver 10 amps, max, and the alternator should be good for a lot more than that, so I'm thinking I need to wire a relay into the circuit so the solar panels don't charge while the engine is running.

Or am I missing something really stupid here?  Appreciate your thoughts on this.  Thanks.

Where does Odyssey state that  14.1 is acceptable?

reading this:

The message to be taken from this graph is clear – in deep cycling applications it is important to have the charge voltage set at 14.4 – 15.0V. A nominal setting of 14.7V is a good choice, as shown by the test results.

http://www.odysseybattery.com/documents/us-ody-tm-001_0411_000.pdf

HOw any charging source is going to react to the presence of another charging source, can vary widely.  Usually,  BOth will work together well, until the battery voltage gets to the maximum of one charging source, or the other, and then that charging source drops out leaving the other to carry on alone.  This is OK, as usually the one charging source can maintain the amperage needed to hold absorption voltage at that point.  if it cannot, then voltage will drop and the other charging source might kick back in

The key here is your alternator can likely meet the 0.4c charge rate, or 40 amps per 100Ah of capacity, and this is key to these TPPL AGMS when they are deep cycled.
  YOu can't easily manipulate the vehicles charging voltage for the ideal charging of a deeply cycled depleted battery, but there is no need to set up a relay or a switch to decide which charging source gets to perform and which one gets to rest.

For odyssey's group31, Ideally 40 amps applied until voltage reached 14.7, then is held there for 4 hours, or until amps taper to 0.5% of capacity at absorption voltage, then float at 13.6v.

As far as what your vehicle allows, it will also vary widely depending on teh make and where the voltage regulator is.  many have the VR inside the alternator, and as the alternator heats, the output voltage drops, by design, not only for the health of the alternator, but for the battery too, which is assumed to be baking in the engine compartment as well.

It is very hard to meet the Ideal recharge parameters of any given battery, some more than others.  Odyssey is among the most difficult in deep cycle applications as that 40 amps per 100Ah of capacity when depleted to 50% is Very important to get the electrolyte migrating through the glass matting.

And While the alternator might be rated at 130 amps or more, what it can actually deliver, when hot, and what the voltage regulator allows, means this 40 amps might be exceeded only briefly before the VR cuts back maximum target voltage and thus charging amps slow considerably.

But in general, your awareness of this batteries requirements put you well and far ahead of 95% of the people who buy a ~400$ AGM battery, and assign superbattery status to it, completely ignorant of how much current this battery needs initially when depleted to the 50% range or below, and just how long that 14.4 to 15 volts needs to be held before the battery can be considered fully charged.

If you can raise your solar controller to 14.7v, by all means do so.  There are ways to manipulate the max voltage your alternator is allowed to target, but it is not easy and the procedure can vary widely depending on vehicle and might not even be possible without setting off the check engine light.

My alternator was regulated by my engine computer and was unideal in the extreme, but I managed to find a way to choose any target voltage between 12.8 and 15 volts.

i say target voltage as it will take time for even 50 amps to bring a 50% battery to 14.7v.

It takes about 25 to 35 minutes before my 50% depleted 90AH Northstar battery is brought upto 14.4v from ~12.2v being fed 40 amps. So even if I have it set at 14.7 or higher, it is going to take time to get that high, and once it gets there, another 3 to 4 hours held there is required for 100% to be reached.

It is very enlightening to put a digital voltmeter on the dashboard so you can see the voltage climb, and what the vehicles voltage regulator decides to hold when the battery is in the 80% charged range and can accept 20 amps or less at 14.x volts.  An Ammeter on the dash showing amperage into the house battery would be even better, as one could see how much is required to raise the voltage to the max setpoint allowed, and how much it drops when the Vehicle's VR inappropriately decides 13.7v is just fine and dandy, when the battery is still craving 14.x.

Mainesail's writeup on alternator vs deep cycle batteries is enlightening.

http://www.pbase.com/mainecruising/automotive_alternators_vs_deep_cycle_batteries

Those with Dodge vans 88 and newer can see how I managed to bypass my voltage regulator in my ECM without setting off the check engine light here:

https://vanlivingforum.com/Thread-Your-Vehicles-voltage-regulator

Other vehicles might be able to borrow some of these techniques.

 

[Optimistic Paranoid]

Where does Odyssey state that  14.1 is acceptable?

reading this:

http://www.odysseybattery.com/documents/us-ody-tm-001_0411_000.pdf

I believe that's the Odyssey Technical Manual.  They also publish a simple Owner's Manual.  The specification of 14.1 volts min and 14.7 volts max is on page 6 of that.

http://www.odysseybattery.com/documents/US-ODY-OM-007_0209_rev_000.pdf

 

[Optimistic Paranoid]

If the panels produce enough power to hold the battery at 14.7 then the alternator won't do anything. If the panels can't hold it at the higher voltage the alternator will take most of the load. The solar will still be putting power into your batteries, but the alternator will do most of the work.

Thanks.  That checks with the way I understand things.

 

[Optimistic Paranoid]

HOw any charging source is going to react to the presence of another charging source, can vary widely.  Usually,  BOth will work together well, until the battery voltage gets to the maximum of one charging source, or the other, and then that charging source drops out leaving the other to carry on alone.  This is OK, as usually the one charging source can maintain the amperage needed to hold absorption voltage at that point.  if it cannot, then voltage will drop and the other charging source might kick back in

So, basically, if the solar can hold 14.6 or 14.7, the power from the alternator won't recharge the battery.

I feel sure that 20 or 30 amps at 14.3 is going to be better for the battery than 8 to 10 amps at 14.7.

Btw, I have a 2012 Ford, 157 amp alternator and the voltage is regulated by the engine computer.

I'm hoping that the battery will never get as low as 50%.  Going to power an Engel fridge, some led lights, and a max-air roof vent, and that's pretty much it.

Thanks.

 

[NeedAnEscape]

The battery will require more power to be held at 14.7 than it will require to be held at 14.3. If the solar can produce enough power to hold the battery at 14.7, then it will. If not, the solar will provide as much current as it can to the battery, and the voltage will drop to 14.3, where the alternator will provide what it can. Having a situation where there's less current going to charging the battery at a higher voltage is impossible with the same battery, in the same condition and same state of charge. Voltage will drop if the source isn't capable of meeting the needs of the load.

 

[Optimistic Paranoid]

You're absolutely right, technically, but I think you're missing my point.  I WANT my alternator to be my main recharging source while I'm driving.  I don't want my solar to prevent that from happening, which I think it will do if it's higher than the voltage the alternator is producing.

Guess the real answer is to run some tests with my DVM and see what the real world results are when I put it all together in a couple of months.

Thanks for your thoughts.

 

[NeedAnEscape]

Your solar won't prevent the alternator from charging the battery, unless the solar is making more power than the battery was able to accept.

 

[SternWake]

Don't forget the vehicle requires a certain amount of amperage just to run the engine/computer/ignition/fuelpump, fuel injectors,daytime running lights.

I measured my engine consumption at 8.2 amps at idle, and this would likely be higher at high rpms. Newer vehicles likely consume higher levels just to run the engine.

While my 198 watts of solar can go as high as 13 amps in ideal conditions, I've rarely seen the solar making 13 amps and providing all the current necessary to run the van.

Before my voltage regulator mod, the ecu 's VR would often choose 14.9v, and if the amperage was there to get the battery to 14.9v, and my solar ABSV was set for 14.7v, the second 14.8 was attained the solar controller would go open circuit, contributing nothing.

I think this is a non issue.  The issue and problem is most vehicles will NOT hold a high enough voltage for long enough, so a solar controller still seeking 14.7v, contributing everything it can, is NOT going to stop the alternator from doing what it needs to do, until perhaps very high state of charge when the battery(s) only need very small amperage numbers to be held at 14.7v.

I like it when my solar is able to take some load off the alternator.  i can definitely feel it on the gas pedal.  the engine is way more free revving.  

Every 25 amps an alternator has to produce requires 1HP from the engine.  I'll gladly let my solar take up as much of that as possible.  Micromental MPG gains  possible in strong sunlight.