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CA Traveler

The Western States

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Posted: 11/16/19 02:59pm Link  |  Quote  |  Print  |  Notify Moderator

Here's my shunt.

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Harvey51

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Posted: 11/16/19 04:43pm Link  |  Quote  |  Print  |  Notify Moderator

Battery monitors are wonderful! I got a cheap one with a built in shunt about 6 years ago. Now I always know what per cent of full charge the batteries are at. I bought a Hall Effect one with wireless display screen last year for a car that had a bit of a parasytic current problem that got solved before I installed the monitor so I have a spare for the motor home.


2004 E350 Adventurer (Canadian) 20 footer - Alberta, Canada
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MDKMDK

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Posted: 11/16/19 04:55pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

MDKMDK wrote:

Sounds like he wants a "fuel gauge" type of monitor for his battery bank.
I'm fine with my charge controller's system status indicator, plus the One Place guesstimate of the chassis and coach battery states of charge. I guess some prefer a more precise solution, but that depends on calibrating the gauge when the bank is fully charged, which is what you're trying to determine, by installing the fuel gauge in the first place?


You tell when your batts are truly full by other means, and then reset the AH counter on the monitor.

Wets--by SG at baseline SG for full, say 1.290 or whatever
AGMs-by when tapering amps at 14.x volts fall to 0.5a/100AH of bank.

The monitor will have an ammeter to it, so you can use that to tell when you get down to the full mark for AGMs.

You do have to reset the AH counter like that fairly often because they get out of whack from recharging counts with not having quite the right allowance for charging efficiency.

Not a good idea to believe the monitor for saying the batts are full by its AH count or by how it gets to a voltage/amps combo magic system and comes up with a percentage SOC based on setting of bank AH size. That bank size is always changing for one thing.

Fact of life with monitors is to determine true full as above, reset the monitor, and use it as a rough indication where you are at until the next time you can get to true full and measure it properly. That still leaves the monitor as useful thing to have.


That's way too much micro-management for me.
That's why I suggested (tongue in cheek) the cylical argument for determining the SoC so that the fuel gauge is accurate. Your point about the baseline numbers always changing is exactly why I don't bother with one.
If it's only going to be "close", I might as well be close with what I've already got.
To each, his own. (or YMMV, if preferred) [emoticon]


Mike.
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BFL13

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Posted: 11/16/19 07:13pm Link  |  Quote  |  Print  |  Notify Moderator

Harvey51 wrote:

Battery monitors are wonderful! I got a cheap one with a built in shunt about 6 years ago.
---------

Now I always know what per cent of full charge the batteries are at.

----------

I bought a Hall Effect one with wireless display screen last year for a car that had a bit of a parasytic current problem that got solved before I installed the monitor so I have a spare for the motor home.


I would worry about the statement concerning Percentage of charge, except Harvey51 has been on here long enough to know the truth, and is getting by ok.

We must assume he properly just uses his monitor as part of the evidence and is not using it as the only evidence.


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CA Traveler

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Posted: 11/16/19 08:00pm Link  |  Quote  |  Print  |  Notify Moderator

"That's way too much micro-management for me."

X2

My monitor resets it's self periodically based on my settings. It's mostly used for a morning SOC check to determine gen run time if any based upon my crystal assessment of the days solar and sometimes at night. It was very useful when the charger failed and the 20A auto charger was marginal and resulted in a change of plans to get it repaired/replaced.

While the solar controller display is very useful it's not aware of the battery parameters vs house loads.

The monitor was installed pre solar as a refinement for the energy audit.

dieseltruckdriver

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Posted: 11/16/19 09:28pm Link  |  Quote  |  Print  |  Notify Moderator

In my opinion there is no reason to fear a shunt. They typically don't fail, and they aren't a connection to worry about corrosion, unless you would install it on top of the battery.

The Victron I have uses one, so did the ebay special that I had in my previous 5th wheel. I also deal with some at work that have been installed for over 70 years, and still working.

That being said, the Victron is much more refined than the ebay one, but they both end up giving the same information. When the amps start tapering down, you are getting closer to fully charged.


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time2roll

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Posted: 11/16/19 10:19pm Link  |  Quote  |  Print  |  Notify Moderator

If my voltmeter shows 14.5+ volts at some point in the day I know I have enough charge to get through the evening meal, tv, charge small items and run the furnace.

Remember this is solar. Not a 120 amp inverter/charger that will show full voltage in 20 minutes.

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MDKMDK

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Posted: 11/16/19 10:22pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

If my voltmeter shows 14.5+ volts at some point in the day I know I have enough charge to get through the evening meal, tv, charge small items and run the furnace.

[image]


It doesn't get much simpler than that.[emoticon]

BFL13

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Posted: 11/16/19 11:05pm Link  |  Quote  |  Print  |  Notify Moderator

"When the amps start tapering down, you are getting closer to fully charged. "

With solar and its typically low charging rate (under 10%) you can be in the 90+ percent SOC zone, but with a better charging rate you will not be close. Even so it takes a long time to get from 90 to 100.

EG, at the 20% charging rate specified for the Bulk stage with AGMs amps will start to taper at about 75% SOC--a long way from being fully charged.

MDKMDK

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Posted: 11/17/19 06:18am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

"When the amps start tapering down, you are getting closer to fully charged. "

With solar and its typically low charging rate (under 10%) you can be in the 90+ percent SOC zone, but with a better charging rate you will not be close. Even so it takes a long time to get from 90 to 100.

EG, at the 20% charging rate specified for the Bulk stage with AGMs amps will start to taper at about 75% SOC--a long way from being fully charged.


What about LiFePO4 banks? Can't assume everyone is using FLA or AGMs any more.

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