Date: Sun, 10 Oct 2004 16:49:17 -0700
Reply-To: Rocket J Squirrel <j.michael.elliott@ADELPHIA.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Rocket J Squirrel <j.michael.elliott@ADELPHIA.NET>
Subject: Re: Monitoring aux battery charging?
In-Reply-To: <6.0.3.0.0.20041009074218.0381d1a8@buncombe.main.nc.us>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
You're right -- I tested the new setup this week and the analog 60-0-60A
meter does not have enough resolution to monitor current going out of
the aux battery unless I fire up the 12V car vacuum. Then you can see
some activity. I also did see charging current when I started the
Vanagon after the aux battery went down to 12.1V. About 15A at first I
reckon, then dropped as the battery picked up charge. There are 30-0-30A
dash meters at Pep boys, but I think that's still not enough resolution.
10-0-10A sounds about right to me. It may be possible to open up one of
these meters and see what's going on inside. If they are true ammeters,
then more turns of wire around the core can be used to increase
sensitivity. If a voltmeter internally, then increasing the series
resistance that the meter is in parallel with will suffice. I don't
think I'll need to bypass the meter for high-amperage applications.
I did mount a voltmeter next to the water level/ battery monitor panel,
using one of those Radio Shack indoor/outdoor thermometers with built-in
battery voltmeter-monitors and digital clock. A SPDT toggle switch lets
me switch the input of the voltmeter between the aux and engine battery.
I used a center-off on-off-on switch so that I could set it to center
position to monitor neither battery. Doing so causes the readout display
light to shut off at night. I mounted the "outdoor" thermal sensor in
the refrigerator. Now I have means to monitor the voltage of the two
batteries, the cabin temp, the reefer temp, and the time o' day.
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westphalia: "Mellow Yellow (The Electrical Banana)"
KG6RCR
Edward Maglott wrote:
> I don't think you're going to see much on the 60 amp scale of the
> typical ammeter. Let us know if you have this in place and how it
> works...
>
> I once had a dream of monitoring the following: Aux battery amperage
> going in or out, voltage of main battery, voltage of aux battery. I
> was going to do this buy cannibalizing a cheap digital multimeter that
> had a 10amp DC current scale. I was going to mount it somewhere and
> then have a selector switch of some sort that would switch the setting
> on the meter and the routing of the wiring between the van's
> electrical system and the inputs on the meter (simultaneously). I
> would also have an "off" setting that would take the ammeter out of
> the circuit in case I needed to draw more than 10 amps from the aux
> battery for any amount of time. I took the multimeter apart and
> started figuring what I would need to do in terms of wiring and
> switching. Then my head started hurting, and I think I eventually hit
> a problem that I couldn't figure a way around. I think it may have
> been when I came up with the requirements for the selector switch I
> would need. Someone more clever than I could probably come up with an
> elegant way to do this.
>
> Edward
>
> At 12:13 AM 10/1/2004, you wrote:
>
>> Fortunately Mellow Yellow and I are not at sea for months at a time, and
>> a failed battery will not sink us. So a first-order approximation of
>> battery charge should suffice, I reckon. Today I picked up an good old
>> school round analog ammeter with a +60-0--60 scale. Wired it in series
>> with the aux battery's (+) terminal. Negative readings big enough to
>> deflect the meter will indicate that I am pulling a lot of current out
>> of the battery, so I should back off on the power consumption. And
>> during charging, high positive current will show that the battery is
>> absorbing a lot of current while it charges up from a partially
>> discharged condition. The current should taper off as the battery
>> reaches full charge. All I need to do is make sure that the engine is
>> revved enough to make the alternator's voltage regulator regulate and
>> watch the meter. A digital voltmeter connected to the aux battery will
>> let me monitor alternator voltage when the engine is running and the aux
>> battery is connected to the main battery. And when the engine is off and
>> the aux battery disconnects from the main, the voltmeter will let me
>> keep an eye on how much reserve the aux battery has. Optima does not
>> recommend letting this Yellow Top discharge below 10.5 volts.
>>
>> That's my plan, it's a good one, and I'm sticking to it.
>>
>> --
>> Mike "Rocket J Squirrel" Elliott
>> 71 Type 2: the Wonderbus
>> 84 Westphalia: "Mellow Yellow (The Electrical Banana)"
>> KG6RCR
>
>
>
>
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