House Battery Blues?

[boywonder]

I have a combo propane/CO detector that is hardwired to the house batteries....having an on/off switch for that doesn't give me warm/fuzzies....too easy to forget.

If you have a battery disconnect, everything is off so that pretty much has to be on to camp.....more failsafe.

The Blue Sea add-a-battery kit has both the ACR separator and a nice battery disconnect switch in one package.

Pretty sure I found mine for under $100 somewhere.....a couple of years ago

https://www.amazon.com/Blue-Sea-Syst.../dp/B01DVOH5W2

[xcnick]

I am making do with Todd Enginnering thing to save money. A trip to Wally World for two 27s and a couple of switches was under $200. Things have been much better this summer but far from perfect.

I ordered this monitor this weekend because it will do amps with the simple hall effect. We will see if it is too simple.

https://www.amazon.com/bayite-Digita...or+Transformer

[Flux]

That's an awesome little gizmo!!

[Scalf77]

Originally Posted by xcnick

I am making do with Todd Enginnering thing to save money. A trip to Wally World for two 27s and a couple of switches was under $200. Things have been much better this summer but far from perfect.

I ordered this monitor this weekend because it will do amps with the simple hall effect. We will see if it is too simple.

https://www.amazon.com/bayite-Digita...or+Transformer

I don't have a problem with the Hall Effect sensor, other then you will suffer some accuracy. The big issue is that this is just a current/voltage meter, it will tell you what the instantaneous current draw is, it will not count that overtime. A key to a good current monitoring battery monitor is to be able to know how many amps have been drawn and how many have been taken from the battery. Not that I don't like measuring stuff, I just would not call that a battery monitor.



There are probably a couple of threads on the forum about Battery Monitors.
http://www.sportsmobileforum.com/for...ors-17692.html There are probably a couple of threads on the forum about Battery Monitors.

[xcnick]

I have been putting the amp/volt meter everywhere since it came in the mail today and I think Todd is the enemy. Is it possible the Todd Powersource 45 uses some battery juice to close a relay or something?

The meter shows 0 when I turn on one tiny LED, but .2 when I turn on two tiny LEDs. Measures to a tenth but only accurate to .2?

I am not getting a good measurement on the wire to/from Todd so I figure it is draining about .1. What I always get is a spark when I touch it to the terminal. Then no spark. If I wait 30 seconds I get the spark again. I get the spark even if Todd is disconnected from all AC.

[MountainBikeRoamer]

Originally Posted by xcnick

What I have wondered about is: what are long trips charging at 14 volts from the alternator when it is already charged doing to the battery? Makes me think I should disconnect the house battery on long drives. Are long drives overcharging the batteries?

Good question! (And very reasonable question!)
I had the same question!

....And.....I asked that same question in a parallel thread a couple days ago .
(Link here -- second-to-last post on that first page):
http://www.sportsmobileforum.com/for...ons-18059.html

Long and short.....as it turns out:
it's sounds like it's a non-issue.....and all because of basic battery-charging electrical physics.

From that thread, here's an excellent response to the question:

Originally Posted by boywonder

Let's go for a really simple explanation......

In a typical circuit the resistance of the load (lightbulb, starter motor, etc) determines the current out of the whatever is supplying the juice.

Think of it this way....two water faucets, one is fully open the other is half open.....the fully open faucet results in twice the flow as the half open faucet....or twice the current...assuming there is enough pressure (voltage) to keep everything flowing as designed.

A discharged battery has a lower resistance than a charged battery so for a given voltage, it draws more current, since the resistance of the load determines the current.

In the above case the alternator, or solar system, or shore power provides the juice and the battery is the load.

Here is another simple analogy....let's take a water tank mounted to the ceiling connected to a tank several feet below........

now let's poke different sized holes in the lower tank......

the larger holes will leak more water (current) than the smaller holes since they have less resistance than the smaller holes to flow, even though the pressure (voltage) in the lower tank is the same for all of the holes.

.......so if you have a bank of 10 batteries wired in parallel, and a voltage source like an alternator, the batteries with the lowest state of charge will draw the most current since they will have the lowest resistance.

Lastly --- from the same thread --- here is how I had (apparently correctly) pictured it:

Originally Posted by MountainBikeRoamer

This is what I was slowly reasoning my way towards....theorizing that a discharged battery must act like a relatively-low-resistance circuit.....and that as it nears a state of being charged, it must start to increase in resistance. When it's empty, it's hungry for current....as it nears full, not so much so.

[Scalf77]

Originally Posted by xcnick

I am not getting a good measurement on the wire to/from Todd so I figure it is draining about .1. What I always get is a spark when I touch it to the terminal. Then no spark. If I wait 30 seconds I get the spark again. I get the spark even if Todd is disconnected from all AC.

I would figure that you have a current transfer when you attach to the battery, from charging some capacitors inside the Todd, once the cap was charged there would be no transfer if you left it connected. Waiting 30 seconds lets the cap discharge.

-greg

[xcnick]

Empty it was very hungry. I saw 50 amps at start up. It went down to 30 after 10 min. Interesting because this is way more than Todd can provide so it is clear starting the engine is the fastest way to get the battery back up.

When "full" according to a car charger which goes green when full, starting the engine showed 4 amps and never seemed to go lower than that. I let it run a half hour. It just seems 4 amps for an eight hour drive might be bad.

But the amps drop as it gets more charge like the reasoning suggests.

[xcnick]

Capacitor makes sense. I wonder if it is a drain over weeks of sitting.

[Scalf77]

Once it was charged as long as you don't remove from the battery, it should stay charged. So I would not expect a drain.