charging marine batteries?

[steveh2112]

i'm still very confused about how to connect a starter battery, a house battery, some solar panels and an optional additional charge from the alternator. i found this although haven't read the whole thing yet
http://outbackjoe.com/macho-diverti...ms-dual-batteries-solar-panels-and-inverters/

i hope SternWake can shed more light on this. its surprising to me there isn't a clear answer on the net about how to do this. you would think every rv're needs a similar setup?

 

[akrvbob]

You're way over-thinking this. You have two charging sources, solar and alternator, you simply run a wire from the positive and negative of each to the house battery.

You need something in-between them to protect the system. From the solar panel you put a charge controller between them. For the alternator you put a solenoid between them.

That's it you're done.

The devil is in the details and if you want to get every possible milli-amp then go ahead and worry yourself about it and drive yourself crazy. If not, buy a solar kit from Renogy and install it, and you're done. For charging from the engine, run a 4 gauge wire from the positive post of the battery to the solenoid (and the hot wire to the radio and it may need a ground) and from it to the positive of the house battery.

Ground the house wire to the frame.

Can every little detail of this be improved on in some tiny way? YES! Is it worth it? You have to decide that for yourself but my answer is NO!!! Not a chance in hell!!

You're going to be driving so much, you shouldn't have a problem. If you do, add another battery and panel!

We have a bunch of experts here who want you to get every detail right. And that is VERY good thing because we all learn from them!! I've leaned so much from these guys it's hard to imagine.

But if you let it paralyze you, then it is a very bad thing. All you have to do is set up a good system following good (NOT PERFECT!) practices and you will be fine (good practice includes fuses, good crimps, big enough wire--you never cut corners on those!). You can always work on perfection later.
Bob

 

[SternWake]

Bob is absolutely correct, One can obsess over achieving perfection and become a slave to their batteries.

Much of my postings regarding this topic are to relate what perfection is, and the reader must choose to decide to far to take it towards that end.

But much of my postings are to help prevent premature batterycide too.

Preventing those new to the 12vDC world from chronically undercharging their batteries and killing them all to early requires they at least be aware of what a battery wants, ideally, and lots of 12v batteries are truly petulant in their requirements to perform acceptably through an acceptable lifespan.


Setting up a System to perform to an acceptable standard initially, is often much cheaper than trying to redo it better the second time.

My current flooded 12v deep cycle battery would have been useless after 3 months had I not had the curiosity and tools and desire to figure out its sweet spot, regarding charging it to get good service from it with regard to what I require from it, which is 35 to 70 AH each night, every night, for 400+ cycles.

 

[steveh2112]

ok, so in the spirit of not over-thinking this, how does this sound?

i get one of those Wallmart group 29 marine batteries and if possible find a spot to mount it in the engine bay (assume econoline van), if no space or too hard to mount, maybe put it behind the front seats.

in normal camped up mode, i connect the Renogy system to the marine battery and let it charge all day. i get some 12-19vdc chargers for my electronics and i do my thing.

if i need to add extra juice to the marine battery while parked, and the sun is out to lunch, i start the van, hook up some jumper cables (or 4 gauge wire) from the starter battery to the marine battery (+ to +, ground through the chassis?) and let it run for an hour or so. maybe put a digital volt meter on there to check charge level so i know when to shut off the engine. also, if i'm in need of a bit of heating or cooling in the van, i can use the vans heater/aircon while charging.

while driving, i do pretty much the same as the above. clearly this will be a lot easier if the marine battery is in the engine bay, i'f not, i'll have to figure out a way to hard wire a cable. i guess go under the floor, drill a small hole under the seat to bring a cable though and seal with a rubber gromit and some caulking.

since i will most likely sell everything after 5 months, i'd rather not be too creative with switches, relays, solenoids, etc. i'm happy to manually connect a lug to a battery as and when needed.

i don't understand the point of the solenoid in bob's post, but i suspect its not needed i'f i'm able to connect and disconnect by hand.

 

[SternWake]

For a 5 month period that should work fine.

I do not know the capabilities of a Ford alternator at Idle speed. A proper size stick to place between seat and gas pedal to hold a slightly higher rpm could vastly increase charge current into house battery, when needed.

As an example, when my alternator and engine is hot, it idles at 525 rpm and can only make 32 amps at most, but if i add 300 rpm it can make just over 60. So 300 more rpm can make a huge difference.

Not sure what type of connectors the renogy kit comes with to easily hook to battery, or if you have to worry about the kit walking away where you will be camping, but these are considerations to take into account.

 

[steveh2112]

i like the stick on the gas pedal idea. maybe put one of those turnbuckle things on for fine tuning.

i guess disappearing solar panels are problem for everyone not screwing them to the van roof. what options do you have? just hoping for the best and checking your insurance i guess.

 

[SternWake]

Panels growing legs can be mitigated to a degree with some steel cables through holes drilled in the frame and attached to the Van, but nothing is going to stop a determined thief.

With the stick to the gas pedal, one can fine tune to some degree by moving the seat forward or back. or perhaps a wedge to increase decrease the distance as desired.

 

[SternWake]

At some point, the stick will no longer be required as the battery acceptance rate will diminish. A cheap clamp on DC ammeter is an enlightening tool to see how much current is flowing.

Just clamp it over one wire in any DC circuit to see the amp flow. this way you can see how much your devices are drawing, and how much the alternator or solar are returning and basically eliminate the guesswork.

http://www.amazon.com/gp/product/B0...d_t=201&pf_rd_p=1944687662&pf_rd_i=B003TXUZDM

These are also full function digital multimeters which is basically a requirement in this lifestyle and a good tool to have, so spending a little more which can easily measure current without opening the circuit, is wise.

Although harbor freight sells an adequate DMM which can measure upto 10 amps of current if the circuit is opened and the meter placed inline. Sometimes they give these away for free with purchase, or sell them for as low as 3$. many easy to find coupons for these cen tech digital multimeters from HF, and no dweller should travel without one of these at a minimum.

 

[steveh2112]

that's a good looking meter, i didn't know you could measure dc current with a clamp style meter. i though they used inductance and dc doesn't have any.

here's how
http://www.kew-ltd.co.jp/en/support/mame_02.html
"In general hall elements are used as a sensor to detect DC current because it is not possible to employ an electromagnetic induction method as used for dedicated AC clamp meters"

 

[MikeRuth]

FYI on a Ford E-150, Mine is a 2007 Stock to my knowledge although it seems beefed up, but that's for another thread.
My stock Alternator is rated at 135 Amps, During a recent test I had my inverter running a 6.5 hp Shop vac pulling down about 121 amps of the house batteries.
For the test I set the engine to 1500 RPM(stick method ) and then closed the solenoid...
24 Amps flowing to the starting battery and 91 amps flowing to the house bank.

I could tell there was some strain on the serpentine belt. BTW Alternator was not HOT so I'm sure that if it was a 110 outside and I had a HOT engine etc, this would be lower.
I'm actually not a fan of closing the solenoid unless I'm on the road. But this was to see just how well things might work.

 

[steveh2112]

one more question about charging 2 batteries (starter and house) while driving. on a long drive, should i leave the house battery on charge even after its full, or should i disconnect it that that point?

is there a risk of damaging the marine battery if i leave it connected to the van charging circuit too long?

 

[SternWake]

Yes, leave it connected. Only in the case of super long drives in super hot weather is there really a danger of overcharging while driving the vehicle.

Mount a small inexpensive voltmeter for each battery on the dashboard, and you will likely notice that when the batteries are charged fully, the voltage the regulator allows drops to the mid 13s. It really depends on the vehicle platform how the regulator behaves, and if it does hold 14.8v all day long then disconnecting the house battery is not a bad idea.

While my voltage regulator is in my engine computer, and should be relatively smart, it exhibits strange behavior at times allowing 13.7v maximum when the battery is still low, and other times allows 14.9v when I know the battery is indeed full. Ambient temp plays a part, but better if there were battery temp and alternator temperature sensors so it can take those factors into account, but those are just 2 more sensors that can fail and cause even bigger issues.

The two voltmeters you will find enlightening. I certainly do. While I do have a battery monitor that reads amperage, I cannot see it from the drivers seat, safely. I think about adding a digital ammeter to see what the alternator is producing total, and this number would be a bit different than what my current ammeter reads, as it reads only amperage into or out of the batteries, and does not include what the vehicle's ignition and other stock electrics are consuming.

http://www.amazon.com/Voltmeter-2-5...1428279575&sr=8-10&keywords=digital+voltmeter

I've got two of these on my dashboard, but in green. What is good about these particular is you can calibrate them. They only power up with Key turned on, and the voltage sense wires go right to the (+) terminal on the battery.

Mine were too bright, and I placed two layers of 35% tint over them to mute them a bit, but I wish they were Red instead, I also wish they read to 0.01V instead of 0.1v. I did buy one 2 decimal red voltmeter, however it was not able to be calibrated and almost 0.2v low and remains in my parts bin, unused.


One of the most enlightening things is having both and ammeter and a voltmeter while the alternator is charging the house battery and one is driving.

Since the well wired alternator in most cases can provide everything the depleted battery can accept at the allotted maximum voltage, One can see just how much a battery can accept at such voltages and with increasing experience, can closely estimate as to how charged the battery is.

 

[SternWake]

Wait, please ignore that link above, as that voltmeter only has two wires, meaning no individual voltage sense wire. It will read voltage right where ever it is getting 12V power from, and if this is not right at the battery terminal, can be off by a good amount depending on the load on the circuit where the wiring is tapped into.

http://www.amazon.com/SMAKN-Voltmet...1428280712&sr=8-68&keywords=digital+voltmeter

This one has an individual voltage sense wire that one can run right to the battery (+), and then calibrate the voltmeter with a real digital multimeter reading the battery terminals.

Those voltmeters one plugs into a ciggy plug can be way off, as the circuit powering the ciggy plug can be powering other things whose load causes voltage drop on the circuit.
If the Ciggy plug has no other loads on it they can be accurate but not have the ability to easily calibrated if they are not.

Rewiring Ciggy plug receptacles to bypass the original circuit, right to the battery itself over 12 or 10 awg, and fised as close to the battery as possible, is another thing I recommend people do in this lifestyle. Often these receptacles are wired from the factory with 18awg wiring and have dozens of feet of this wiring through half a dozen different connectors, all which cause too much resistance and voltage drop, to the detriment of the battery, and the device at the end requiring power.

 

[steveh2112]

interesting, but i think in my case i'd get that fancy clamp style multimeter you listed in the other post, then i could bring sensing wires from the starter and house battery to a terminal block in the passenger area and get my co-pilot to check the voltage periodically

 

[SternWake]

Here is another interesting product. I do not have personal experience with it, but it is a combination voltmeter and Ammeter capable of reading 100 amps. If there is only a single house battery it is unlikely to ask for more than this much current, and smaller inverters not powering microwaves will not ask for more than 100 amps either.

A Shunt needs to be installed between house battery (-) and chassis ground for it to be able to measure amperage into or out of house battery.

Voltage alone tells well less than half the story when a battery is charging or discharging. An Ammeter and Voltmeter together tell about 85% of the story. If that Ammeter( battery monitor) has the ability to measure Amp flow both into and out of the battery, then that approaches 100% of the story.

But on a Flooded battery, only the use of all three plus a hydrometer can tell 100% of the story.

That is, If one actually cares to know all the details of the story.