Heavy duty battery for minivan???

[Kathleen]

Wow, @ John61CT, that link is amazing. And of course the guy is an electrical engineer, a profession I always admired due to my fascination with electricity and lightning (I try not to draw it to me when I'm out in the field!)

My eyes are tired now so I was only able to scan his entire info, and it is lengthy, but I don't mind that because he explains so much so clearly.

I will read it again soon when my eyes are rested. I'm impressed by his knowledge, and it's just in the nick of time because I MUST get someone to install my system properly in order to get the most out of it. I can't afford sloppy mistakes or the wrong equipment.

I see he's no longer permitting posts in response to this solar info. Too bad. Will see if he has a current blog somewhere. He's got the info down and warns against spending hard earned money with salesmen who don't know what they are talking about. "Everyone has an agenda..." Hah! I was in sales and I know this to be true.

When I read it again I have to look for how this info might be applied to my needs living in a minivan. He's in a big RV and has room for all those devices. I'd love to talk to the guy and get his take on what I should do. Better yet, I'd like him to do the install!!  :idea:

Thanks so much for that link!!!

 

[John61CT]

Yes it's cool to get honest personality and some entertainment along with the Knowledge.

​Charles Sterling, "Maine Sail", Chris Gibson are all great,

Here are a couple of links on monitoring battery health and SoC charge level, I find the second very funny

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

http://www.ybw.com/forums/showthread.php?73924-Smartbank-battery-management/page5

As you do your research googling the relevant discussion forums, you'll start to recognize those who know what they're talking about. Read the back threads a while taking notes and gradually your knowledge will grow to the point you can ask the right questions for your own unique scenarios, and engage in intelligent discussions with world-class experts without driving them nuts.

They tend to have strong opinions, and there are valid disagreements, but at that level all the choices are better than the ones you would have made back when you were a noobie.

You're unlikely IMO to find someone local to you with the required knowledge in the various components, but once you know what you want start ordering, build up the inventory, write your specs and draw your design, then your trusted mechanic can do the physical install.

 

[John61CT]

Starting simple: http://www.expeditionportal.com/for...ke-a-cheap-isolated-dual-battery-setup-for-50

Not for extended boondocking, doesn't even deal with multiple charge sources, but IMO a decent starting point to understand at the ground floor level.

Personally, I would move the Alternator output over to the "house" (I will call it the Primary) circuit, start the van engine off that big deep-cycle bank in normal circumstances, and keep all current loads there and also add any other charging sources there.

Thus what most people call the "starter" battery is now used only for Backup purposes, I'd have no loads on it whatsoever, except for when you've run the Primary (house) bank down too much to crank the engine.

If your system is designed and being used properly, this should happen very rarely, either a component failing or you leaving something on too long.

The key to this setup is making sure your "house loads" are smaller than what your alternator is putting out, and "never" using the Backup battery for anything else.

But for belt & suspenders, have one of those small "personal power" jumper packs kept charged up for emergencies as well.

 

[SternWake]

all sorts of strategies can be employed.

My preference would be not touching the original engine battery alternator circuit, and simply tap the alternator itself for house battery charging.

I would not want the house battery bank starting the engine, even if it is quite capable of doing so.
My reasoning is there is a voltage spike when the starter is disengaged that 'could' damage things hooked to house battery.

But I also must say I have been starting my engine from house battery as they are presently one and the same, without issue.

I have no battery in engine compartment, and only one group 27 AGM in a location where I could fit 2 of them. I can get away with this because my 3 charging sources are optimized, and I know how charged or discharged my battery is because I have an amp hour counting battery monitor.

I don't even carry a jumper pack, but probably should, and no doubt would if travelling to an area where getting a jump would be difficult or inconvenient.


In the Expedition portal thread, notice how the 'factory wiring' goes from alternator to engine battery then to a fuse and then to solenoid to another fuse then to house battery.
If one bypasses the 'factory wiring' and engine battery, and pulls power for solenoid from alternator (+) stud and (-) mounting bolt, charging amps will improve greatly as it bypasses the original factory wiring, and one needs one less fuse as the factory wiring is already fused, and bypassed, will not be carrying the additional current of a depleted house battery.

Taking power for solenoid from engine battery is simply more convenient, but reduces recharging performance significantly into a depleted battery by a considerable degree, over taking power directly from alternator.

Stacking another ring terminal on the alternator (+) output stud can be a challenge and perhaps more effort than simply using engine battery, but a very worthwhile and significant increase in amperage making it to depleted house battery will occur when 'factory wiring' is bypassed

Not shown in that diagram is the ground path.

If house battery is grounded to frame, then alternator current has to pass partially through original engine to battery ground and battery to frame/firewall ground, thereby greatly increasing the distance, and resistance. If house battery is grounded to nearby frame, add another ground cable from frame nearby alternator to alternator mounting bolt for GREATLY improved house battery recharging.

Even better is to eliminate the frame grounds, and use a thick black (-) cable from house battery(-) to alternator mounting bolt.

Asking the factory wiring to recharge a depleted house battery bank is like asking a marathon runner, or a sprinter, to breathe through a single cocktail straw.
Fat + and - cables between alternator and house bank is like 3 McDonald's soda straws stuffed up each nostril.

It just happens to be standard practice to use a cocktail straw, then wonder why the house battery is sulfated and worthless in short order, despite regularly driving.

Join my campaign against cocktail straws in alternator charge circuitry for house battery!

Just say no to factory wiring! It is just barely adequate ( just fine, lol) for the engine battery and woefully inadequate when another depleted battery is tacked on the the end of it. Even if the tacked on circuit is thick. Bypass the restrictions! Take power from alternator (+) stud instead!!

 

[Kathleen]

This Noobie says a big Thank You to every one of you who took the time to respond to my questions! You're all heroes in my eyes, providing me with all that information.

Best to all of you and happy travels.

 

[akrvbob]

You are underestimating solar. With 500 watts and 3 batteries, you should easily be able to run the few things you want. It won;' be cheap, (around $1200) but you will have free (other than replacing the batteries periodically) electricity for life.

 

[Ticklebellly]

A depleted battery might accept 40 amps at 14.7v, but only 10 amps at 13.7v.

The 200 amp alternator will charge no faster than a 100 amp alternator when the battery can only accept a certain amount, ...............................

A small paraphrase may help those who may be a little unsure.   A very simplistic explanation of electrical performance is "Volts (Electromotive Force) push Amps (Current) through Ohms (Resistance to current flow)".   In the case of a fixed voltage alternator, an alternator output of 14.7 volts will "push" some measure of current into a battery with a SOC voltage less than the alternator voltage.   As SOC voltage of the battery rises, less current is "pushed" into the battery as the difference between the charging source voltage and the charging battery is progressively smaller.   A graph of the falling rate of current into the depleted battery can be considered a graph of the bulk charging of the depleted battery.   As said above, alternator systems that drop their output voltage from 14.7 to 13.7, make the charging performance less efficient to the point that charging current is "not much".   If the difference between alternator voltage and depleted battery terminal voltage is small, then a 4000 Amp alternator will not charge appreciably faster than a 100 amp alternator.

 

[John61CT]

My preference would be not touching the original engine battery alternator circuit, and simply tap the alternator itself for house battery charging.

Thanks for the substantive response!

So if I do stick to "no load on the Backup, start from the Primary/House", do you mean keep the alt directly connected to the small Backup starter? I plan to use some sort of acr/solenoid to combine when the Alt is charging, otherwise isolated from Primary/House.


> voltage spike when the starter is disengaged that 'could' damage things hooked to house battery.

I'd rather just create a "sensitive stuff" circuit that gets momentarily disconnected while cranking if this turns out to be an issue - or do that for the whole House Loads circuit. Most of my electronics are either behind their own battery or (maybe?) an inverter.


> amp hour counting battery monitor

Have you run into the reset/calibration headached discussed around Gibson's SmartGuage (Balmar here)?


> In the Expedition portal thread, notice how the 'factory wiring' goes from alternator to engine battery then to a fuse and then to solenoid to another fuse then to house battery.
...
significant increase in amperage making it to depleted house battery will occur when 'factory wiring' is bypassed

Not sure I follow all the ramifications, but I think the issues there are also resolved by my just sticking to the design of "Backup-only starter isolated from all loads except when (very rarely) needed (and only) for cranking".

Alt is always wired direct to Primary/House, Backup gets float/minor top-ups secondarily.


> ground path.
...
eliminate the frame grounds, and use a thick black (-) cable from house battery(-) to alternator mounting bolt.
...
Fat + and - cables between alternator and house bank
...
Join my campaign against cocktail straws in alternator charge circuitry for house battery!Just say no to factory wiring!


sounds good, consider me signed up! except for getting a massive double flood of soda up my nose ? (⋟﹏⋞)