Date: Wed, 17 Jun 2009 06:22:29 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Battery/Charging system questions.. A lot of info included..
In-Reply-To: <6bc66ccf0906161214ne92e438m514576b4b4a5b887@mail.gmail.com>
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If you really had 17 to 20 volts across the battery you would have an awful
gassy bubbly mess. You are either using the meter wrong or you have a bad
ground and are seeing the voltage of the two batteries in series.
2 or 4 volts across the relay while closed is an indication the relay is not
making a good contact. This is common with the large relays as the small
current battery charging presents will allow the large contacts to oxidize
and foul up, especially with the cheaper of these relays. You also can have
a bad battery. A shorted cell can cause all sorts of havoc.
Usually battery charge lines are not fused. Fuses do not make sense as you
have a power source on both sides. The wires need to be large enough to
carry both the charging load and all appliances on that battery.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Don Hanson
Sent: Tuesday, June 16, 2009 3:15 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Battery/Charging system questions.. A lot of info included..
From a dummy...
The last few months my coach battery hasn't seemed to be staying charged
up as well as in the past. I've changed nothing recently.
So I got out my handy dandy Radio Shack digital meter today and began
poking around. I find lots of Volts. Dunno what it should be, but I seem
to have too many at the Vehicle battery and plenty at the Coach
battery..however, my water pump is kinda slow and the Westie Indicator
lights are on the Red bulb most of the time (when the engine is not
running)..
My system:
I have two identical NAPA batts. of around the same vintage (aug '07)
These are "sure start 65" BCI 42 with 500cca and 250amps. One under the
passenger seat (the vehicle batt) and the Coach batt under the driver's
seat. I have a big wire (fused, of course) across (vehicle to coach batt)
which feeds a big 'mechanical' can 3 terminal relay, also under the drivers
seat. This relay is controlled by a wire from the ignition and the wire is
also switched (that supply wire from the ignition to the relay)...I wasn't
sure about starting the vanand how the two batteries would inter react
during start up, so I began by having that secondary switch off whenever I
started up...That proved to be un-necessary but it is nice to be able to cut
the power to the secondary battery without shutting off the van..
Ok, so I run the van and check the relay...Flip the switch from the
ignition to excite the relay and "Click!" it works fine..
But the numbers (from my digital meter) don't make sense....Oh yeah, when
the van is running, the Westie stove-front power indicator light goes
Green...engine off..Red...on Green.
From my digital meter: Vehicle battery..Van off reads 20.6 Van running
reads 21.8
Coach battery...Van off reads 17.3 Van
running and relay active reads 21.7
I double checked with an older analog meter and my Radio Shack one is
functioning fine...though I wasn't sure which scale to read on the analog
meter, it is consistent with the digital one.
So how come so many volts? Is this bad? Or is my meter simply screwy or
my testing technique faulty?
Also, across my 'mechanical' relay (a silver cylinder with two (+/_) large
terminals and a 'supply' terminal..I am seeing (I think) some current when
there shouldn't be any. I see about 4 volts across the two main (+ (in from
the vehicle battery) and -(out to the accessories in the coach))
connections. That shouldn't be, unless perhaps the relay is now faulty?
Anybody care to take a shot at this weirdness?
I am thinking I probably have a couple of things going on here..Maybe my
meter is reading wrong and maybe the relay is faulty.
The setup has worked pretty well for me for about 18 months including a
prolonged (4 months) outing where the Van was used as a second bedroom and
work/play vehicle daily..I would get about 2.5 hrs of satellite radio,
incandescent light and some computer time before my coach battery went
down...At present, I'd guess maybe I'd be getting about 1/4 that, so
something is out of whack somewhere...I know I could have a more appropriate
electrical system but I don't want to re-do the whole thing right now.
Don Hanson
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