I have a 2003 Sprinter. A series 22 AGM under the passenger seat. (May add another 22 if I put in a small fridge.) About a 12 foot cable run. My goal is to run cables from main to house battery with a simple manual disconnect either near the main or the house battery. I don't want to purchase an Add a Battery kit if I don't have to. I am only charging small stuff with the house battery and will have a CB wired to the house. My questions are. What size cables should I buy? What kind of connect/disconnect would be best/easiest? Should this be near the main or house battery. Is this setup the way a knowledgeable person would do this? If not, what is better? Thanks!
Main to house battery cable run.
- Thread starter vanavalk
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What is the very most amperes your alternator can produce? There are voltage drop tables all over the web. For charging circuits a voltage drop of less than 3% is desirable. 12 feet is a long run. That could need 2AWG, real heavy wire to work with. I prefer an automated disconnect. Using a continuous duty solenoid to connect when the alternator is charging and disconnect when the engine is off or during start-up cranking.
SternWake
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https://www.bluesea.com/products/6006/m-Series_Mini_On-Off_Battery_Switch_with__Knob_-_Red
Fat cable is always best,where charging batteries is concerned.
I use1/2/Both/OFF manual switches to direct current to or from either battery.
BUt now I have only one battery and all the switches are set to 2.
Nothing worng with a manual switch but for the human error factor.
Fat cable is always best,where charging batteries is concerned.
I use1/2/Both/OFF manual switches to direct current to or from either battery.
BUt now I have only one battery and all the switches are set to 2.
Nothing worng with a manual switch but for the human error factor.
Trebor English
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Normally the max amps and the % loss make sense. With charging the house battery that is all out the window.
When you first connect the two systems there may be 2 volts difference between the two, 14.2v, 12.2v. The starter battery is rated in hundreds of cranking amps output and the house battery has no rating on what it can take. The current can be quite high. To maximize rhe life of your solenoid switch some resistance is a good thing.
After a while the two batteries get to close to the same voltage. With low voltage difference, 13.6v starter, 13.4v house battery, the charging curent fades away. At 13.4v there is not much charging. Now what you want is the lowest possible voltage drop at a low current. A .5 volt drop will virtually stop charging. If the alternator could be persuaded to put out only 14.4 things would be much different.
In my opinion you want the fattest wire possible. The limits include things like the price of the wire, finding a place to run the wire, the physical work of installing the wire, availability of the wire, weight of the wire. These are not electrical limits.
Once you have the wire size established the solenoid switch size has to be determined. It has to be rated at enough amps to handle a full starter battery and an empty house battery or the reverse situation with the added twist of also running the starter motor.
The fuses protect the wire from the batteries. You want higher current fuses for less voltage drop. Breakers generally have more resistance than fuses, that's bad.
So, given that there are two substantial lead acid batteries and a pitiful alternator voltage regulator, the minimum is #6 awg wire and a 40 amp switch. That will do quite a bit of charging for a low price, emphasis low price. From there it depends on how much money you want to pay. The more you pay the more charge current you get and the higher state of charge your house batteries get to.
When you first connect the two systems there may be 2 volts difference between the two, 14.2v, 12.2v. The starter battery is rated in hundreds of cranking amps output and the house battery has no rating on what it can take. The current can be quite high. To maximize rhe life of your solenoid switch some resistance is a good thing.
After a while the two batteries get to close to the same voltage. With low voltage difference, 13.6v starter, 13.4v house battery, the charging curent fades away. At 13.4v there is not much charging. Now what you want is the lowest possible voltage drop at a low current. A .5 volt drop will virtually stop charging. If the alternator could be persuaded to put out only 14.4 things would be much different.
In my opinion you want the fattest wire possible. The limits include things like the price of the wire, finding a place to run the wire, the physical work of installing the wire, availability of the wire, weight of the wire. These are not electrical limits.
Once you have the wire size established the solenoid switch size has to be determined. It has to be rated at enough amps to handle a full starter battery and an empty house battery or the reverse situation with the added twist of also running the starter motor.
The fuses protect the wire from the batteries. You want higher current fuses for less voltage drop. Breakers generally have more resistance than fuses, that's bad.
So, given that there are two substantial lead acid batteries and a pitiful alternator voltage regulator, the minimum is #6 awg wire and a 40 amp switch. That will do quite a bit of charging for a low price, emphasis low price. From there it depends on how much money you want to pay. The more you pay the more charge current you get and the higher state of charge your house batteries get to.
SternWake
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The vehicles voltage regulator has a huge part in how fast a depleted battey will charge. the best one can do, other than manipulating or bypassing that voltage regulator, is making sure there is as little resistance as possible on the circuit.
But, how much improvement will there be using 2awg compared to 6awg when the VR only seeks 13.6 with a very depleted battery?
Not all that much. BUt When it seeks 14.5v+ then there will be a big difference.
All vehicles are different and will respond different with different loads on the alternator.
13.6 to 13.8 is what most vehicles will revert to fairly quickly, so as to not overcharge the starting battery.
With fuel injection the engines generally start so quickly ,that under a minute being held at 14.5v, and the battery is at the same state of charge as before starting. Fine for a starting battery, not fine for a depleted house battery tacked onto the end of the circuit.
But any charging is better than no charging, just do not expect the alternator is some magical instant battery recharger. It has potential to deliver high amperage, but it's potential is throttled back by the voltage regulator, and a battery can only accept so much amperage at any given voltage, and 80 to 100% state of charge on a healthy battery takes 3.5 hours at ideal voltages, no matter what.
There is no getting around that fact.
Combine that with unideal voltages, and an alternator only recharged deeply cycled battery is highly unlikely to ever get fully charged when driving, and thus is doomed to a shorter lifespan.
Which could be perfectly acceptable to the battery user, or not.
But, how much improvement will there be using 2awg compared to 6awg when the VR only seeks 13.6 with a very depleted battery?
Not all that much. BUt When it seeks 14.5v+ then there will be a big difference.
All vehicles are different and will respond different with different loads on the alternator.
13.6 to 13.8 is what most vehicles will revert to fairly quickly, so as to not overcharge the starting battery.
With fuel injection the engines generally start so quickly ,that under a minute being held at 14.5v, and the battery is at the same state of charge as before starting. Fine for a starting battery, not fine for a depleted house battery tacked onto the end of the circuit.
But any charging is better than no charging, just do not expect the alternator is some magical instant battery recharger. It has potential to deliver high amperage, but it's potential is throttled back by the voltage regulator, and a battery can only accept so much amperage at any given voltage, and 80 to 100% state of charge on a healthy battery takes 3.5 hours at ideal voltages, no matter what.
There is no getting around that fact.
Combine that with unideal voltages, and an alternator only recharged deeply cycled battery is highly unlikely to ever get fully charged when driving, and thus is doomed to a shorter lifespan.
Which could be perfectly acceptable to the battery user, or not.
Optimistic Paranoid
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Theoretical question for Sternwake:
Would it be possible to wire one or more marine battery switches (with AFD if needed) in such a way that you could kill all charging to the engine battery shortly after starting and have all alternator power going to the house battery? Obviously, the engine systems - ignition, fuel pump, lights, etc. - would have to be treating the house battery as a source of power while that was going on. I'm just not sure how you would wire for something like that. And would the voltage regulator or computer recognize the low state of charge of the house battery and keep the amps flowing?
Would it be possible to wire one or more marine battery switches (with AFD if needed) in such a way that you could kill all charging to the engine battery shortly after starting and have all alternator power going to the house battery? Obviously, the engine systems - ignition, fuel pump, lights, etc. - would have to be treating the house battery as a source of power while that was going on. I'm just not sure how you would wire for something like that. And would the voltage regulator or computer recognize the low state of charge of the house battery and keep the amps flowing?
SternWake
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Some newer GM's have a hall effect sensor on a battery cable to know how much the battery is accepting, or providing. I hope it would adjust voltage accordingly to faster recharge a depleted battery but I do not know for sure.
I am not sure bypassing the fully charged engine battery will allow any paricular vehicles VR to sense that it is requiring a higher field current to maintain the higher voltage, and thus allow this higher current to be held longer to faster charge a battery.
VR manipulation will be different on every vehicle. I once tried to figure out Why my VR decided to choose 14.9, 14.7, 14.1 or 13.7, and most of the time it was 14.9 or 13.7, very rarely anything other.
I gave up trying to find any logic in its patterns, put a 10 ohm 50 watt resistor in between the two wires that originally went to the field terminals on alternator, thus tricking the engine computer into thinking it was still attached and controlling alternator, and used an adjustable voltage regulator, a Transpo540HD. I modified this VR with an external potentiometer, located on my dashboard next to voltmeters and ammeter, and do the He-man 'I have the POWER' type of battle cry every time I adjust voltage
more details on that modification here:
https://vanlivingforum.com/Thread-Your-Vehicles-voltage-regulator?highlight=voltage+regulator
Basically with this set up, If I have enough rpms available, I can always charge my battery as fast as safely possible anytime my engine is running.
When something else is controlling voltage, that is not possible.
But still, 80 to 100% takes time even at ideal voltages, and 100% regularly is important to battery longevity.
2 years ago my flooded group 31 battery was removed from my van leaving me with only a 90Ah northstar AGM for both house and engine duties. Initially I was planning on another battery for the house, as I am wired for it.
But I found this AGM battery can easily start my engine depleted 65 of its 90AH, and it is highly unlikely I will use more than 65 of its 90AH. This battery now has ~ 575 deep cycles on it, and several hundred more shallower cycles on it, and several thousand engine starts, and turns 4 years old in November.
For the first 8 months of only having one battery, my voltage regulator in engine computer behaved pretty much exactly the same as when I had two batteries, one fully charged engine battery and one house battery at various levels of depletion.
While highly vehicle specific, I can say that on my vehicle, bypassing the engine battery shortly after starting sending all its current into depleted house battery, would not yield any noticeable difference to how long the voltage regulator held a higher voltage, and this is with the voltage regulator inside the engine computer, granted it is a 1989 computer.
And as far as that switching, well I have a 1/2/both off switch. 1 is the engine located battery, 2 is the house battery. i could start the engine on one, then switch to both, then to 2, and completely remove engine battery from the loop, and used to do so, but did not ever notice any different behavior of my engine computers voltage regulator.
But it might have an effect with other vehicles.
Without data it is only speculation.
To the casual reader, Do note that the 1/2/both/off manual switches have a consequence. if switched to OFF with engine running, it can blow the diodes int he alternator, so the direction of rotation of the switch is very important.
AFD is an alternator field disconnect incorporated on some of these switches, which is for externally regulated alternators. One runs the field wires through the switch, so when it is turned to off, it disconnects the field too, saving the alternator diodes.
My switches do not have AFD and if they did I would not run the field wires to where my switches are located anyway.
And i use the term switches, plural, as one switch is for my OEM wiring, switching starter/alternator original battery (+) cable to either battery. My other switches are for loads and charging sources, so I can switch all house loads to either battery or all charging sources like my MEanwell poiwer supply or my solar to either battery. I do not include the alternator in that 'sources' switch though.
But now i only have one battery. All switches are kept in the 2 position as there is no battery currently in my engine compartment, and will not be one until my electrical needs change.
I am not sure bypassing the fully charged engine battery will allow any paricular vehicles VR to sense that it is requiring a higher field current to maintain the higher voltage, and thus allow this higher current to be held longer to faster charge a battery.
VR manipulation will be different on every vehicle. I once tried to figure out Why my VR decided to choose 14.9, 14.7, 14.1 or 13.7, and most of the time it was 14.9 or 13.7, very rarely anything other.
I gave up trying to find any logic in its patterns, put a 10 ohm 50 watt resistor in between the two wires that originally went to the field terminals on alternator, thus tricking the engine computer into thinking it was still attached and controlling alternator, and used an adjustable voltage regulator, a Transpo540HD. I modified this VR with an external potentiometer, located on my dashboard next to voltmeters and ammeter, and do the He-man 'I have the POWER' type of battle cry every time I adjust voltage
more details on that modification here:
https://vanlivingforum.com/Thread-Your-Vehicles-voltage-regulator?highlight=voltage+regulator
Basically with this set up, If I have enough rpms available, I can always charge my battery as fast as safely possible anytime my engine is running.
When something else is controlling voltage, that is not possible.
But still, 80 to 100% takes time even at ideal voltages, and 100% regularly is important to battery longevity.
2 years ago my flooded group 31 battery was removed from my van leaving me with only a 90Ah northstar AGM for both house and engine duties. Initially I was planning on another battery for the house, as I am wired for it.
But I found this AGM battery can easily start my engine depleted 65 of its 90AH, and it is highly unlikely I will use more than 65 of its 90AH. This battery now has ~ 575 deep cycles on it, and several hundred more shallower cycles on it, and several thousand engine starts, and turns 4 years old in November.
For the first 8 months of only having one battery, my voltage regulator in engine computer behaved pretty much exactly the same as when I had two batteries, one fully charged engine battery and one house battery at various levels of depletion.
While highly vehicle specific, I can say that on my vehicle, bypassing the engine battery shortly after starting sending all its current into depleted house battery, would not yield any noticeable difference to how long the voltage regulator held a higher voltage, and this is with the voltage regulator inside the engine computer, granted it is a 1989 computer.
And as far as that switching, well I have a 1/2/both off switch. 1 is the engine located battery, 2 is the house battery. i could start the engine on one, then switch to both, then to 2, and completely remove engine battery from the loop, and used to do so, but did not ever notice any different behavior of my engine computers voltage regulator.
But it might have an effect with other vehicles.
Without data it is only speculation.
To the casual reader, Do note that the 1/2/both/off manual switches have a consequence. if switched to OFF with engine running, it can blow the diodes int he alternator, so the direction of rotation of the switch is very important.
AFD is an alternator field disconnect incorporated on some of these switches, which is for externally regulated alternators. One runs the field wires through the switch, so when it is turned to off, it disconnects the field too, saving the alternator diodes.
My switches do not have AFD and if they did I would not run the field wires to where my switches are located anyway.
And i use the term switches, plural, as one switch is for my OEM wiring, switching starter/alternator original battery (+) cable to either battery. My other switches are for loads and charging sources, so I can switch all house loads to either battery or all charging sources like my MEanwell poiwer supply or my solar to either battery. I do not include the alternator in that 'sources' switch though.
But now i only have one battery. All switches are kept in the 2 position as there is no battery currently in my engine compartment, and will not be one until my electrical needs change.
I ran 10 feet of 4 AWG. I have purchased a 100 Amp inline fuse to be wired right near the main battery. I bought a Park Power battery Master Switch On/Off 48 voltage rating. This will be mounted near the house battery and within reach while driving. I have a Scangauge II connected which will show me the Volts. Going to connect it all tomorrow and spin the key. I can check the charging of the house battery with my Multi_meter, right? Also, should I see a drop in voltage on the Scangauge when I switch the house battery on?
Weight said:
I was told by the owner of Wills RV in Sturtevant Wi. to put the fuse near the main battery. He exclaimed that in case of a short somewhere in the line too the house battery it would blow the fuse before it got to the main battery. If the line shorted with the fuse near the house battery, the arc (for lack of a term I don't know) would reach the main battery and cause many issues I don't want to think about. OR, do you mean another 100 amp fuse near the house battery also??? And if that's what you mean before or after the on/off switch?
Spaceman Spiff
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vanavalk said:
Either battery shorted can cause a fire, so you want a fuse as close to each battery as possible. ABYC spec's call for a fuse within 8" of a battery (or battery bank if multiple batteries in proximity are hooked together). I'd put it before the switch.
-- Spiff
Trebor English
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Every wire needs protection at every point where power is applied. This wire is connected to two batteries. Both batteries have the capacity to light up the wire. Both ends of the wire need a fuse close to the battery.
At the vehicle battery end, if you connect the wire at the alternator rather than the battery the fusible link that is already there protects the wire from the vehicle battery. If the alternator can only produce 90 amps and the cable is good for 100 amps then the cable doesn't need protection from the alternator.
At the vehicle battery end, if you connect the wire at the alternator rather than the battery the fusible link that is already there protects the wire from the vehicle battery. If the alternator can only produce 90 amps and the cable is good for 100 amps then the cable doesn't need protection from the alternator.
I did put another 100 amp fuse 6 inches from the House battery. Got it all wired and working as it should!!! I am very appreciative of ALL you guys help. One more thing. a couple of you noted my puny 90 amp Alternator in the Sprinter. They sell 120 and 150 amps on Rock auto. Do you think I should upgrade or will my original alt be enough for me. I am only using the house for charging things and run a small fan. Maybe in the future, I'll run a small fridge. Thanks again. Mike.
Now I am ready to hit the road in the SkiRV and aim toward Alaska for 2-3 months.
Now I am ready to hit the road in the SkiRV and aim toward Alaska for 2-3 months.
SternWake
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A higher rated alternator should be able to shed heat better, but there is no guarantee it will decrease charging times.
I'd notspend the bucks on the upgrade to replace a fucttioning alternator unless it proved woefully inadequate.
My alternator is rated at 120 amps, very rarely is it ever required to product that much juice.
My battery would have to be very depleted, and I wouldfhave to be using headlights, blower motor on high and blasting my stereo before it would hit that wall, and it could only do it at 2400+ rpm, where my engine rarely goes and when when it does, is brief.
YOu could carry a spare if a failure on the Alcan is a cause for worry.
I'd notspend the bucks on the upgrade to replace a fucttioning alternator unless it proved woefully inadequate.
My alternator is rated at 120 amps, very rarely is it ever required to product that much juice.
My battery would have to be very depleted, and I wouldfhave to be using headlights, blower motor on high and blasting my stereo before it would hit that wall, and it could only do it at 2400+ rpm, where my engine rarely goes and when when it does, is brief.
YOu could carry a spare if a failure on the Alcan is a cause for worry.
billybob200138
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Hi all. General question. I have a heavy duty van battery. If I tie in another marine battery to it will my alternator keep it charged? Thanks not sure what the alternator puts out on my 92 Ford van? Thanks again
highdesertranger
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Hobo Joe that's a hard question to answer with the info you gave us. I recommend starting your own thread so we don't derail this one because there are a lot of questions that need to be asked. highdesertranger
It is possible to use a smaller wire gauge to interconnect the batteries, but then you need a self-resetting breaker inline to protect the wiring.
This is the way I wired mine, an older Class C and my current Ford Van.
During starting, the heavy current, if any, that tries to flow from the house battery to the starting battery is quickly stopped by the breaker. After a few seconds, the engine will have started, and then a few seconds later, the breaker resets and charging current can resume and flow between the batteries and equalize them.
If the charging current is still too high for the breaker, it will trip again. Then reset again, and effectively it will 'pulse' repeatedly until the batteries are equalized. But this rarely happens since the house battery contributes almost nothing to start the vehicle.
I use a 20 amp self-resetting breaker, so the average current flow can never exceed that, although short pulses of 100 amps are possible. But they are very short duration and do no harm. You could also install a 100-200 amp fuse inline if you felt it was needed but I have not done that.
The smaller gauge wire is much easier to deal with inside the vehicle, and the wiring is highly simplified. Another advantage is that you can use a simple toggle switch inline to manually isolate the house battery overnight to keep the starting battery ready for the next morning when you need to start the motor. If you add a toggle switch I recommend using a 10 amp self-resetting breaker instead of the 20 amp.
On mine, the solar panel and controller are wired to the house battery, and contribute nothing to the starting battery when the toggle switch is set to OFF, which isolates the two batteries.
In all normal driving situations, I keep the switch set to ON, and both batteries receive some charging from the panel and the alternator.
Works for me....YMMV.
This is the way I wired mine, an older Class C and my current Ford Van.
During starting, the heavy current, if any, that tries to flow from the house battery to the starting battery is quickly stopped by the breaker. After a few seconds, the engine will have started, and then a few seconds later, the breaker resets and charging current can resume and flow between the batteries and equalize them.
If the charging current is still too high for the breaker, it will trip again. Then reset again, and effectively it will 'pulse' repeatedly until the batteries are equalized. But this rarely happens since the house battery contributes almost nothing to start the vehicle.
I use a 20 amp self-resetting breaker, so the average current flow can never exceed that, although short pulses of 100 amps are possible. But they are very short duration and do no harm. You could also install a 100-200 amp fuse inline if you felt it was needed but I have not done that.
The smaller gauge wire is much easier to deal with inside the vehicle, and the wiring is highly simplified. Another advantage is that you can use a simple toggle switch inline to manually isolate the house battery overnight to keep the starting battery ready for the next morning when you need to start the motor. If you add a toggle switch I recommend using a 10 amp self-resetting breaker instead of the 20 amp.
On mine, the solar panel and controller are wired to the house battery, and contribute nothing to the starting battery when the toggle switch is set to OFF, which isolates the two batteries.
In all normal driving situations, I keep the switch set to ON, and both batteries receive some charging from the panel and the alternator.
Works for me....YMMV.
