Sigh....suffering electrical insanity ..at midnight

S34

S34

.
Jan 3, 2016
17
Self built Stewart 34 Auckland
New install running tests and suddenly getting 24v!
Two banks paralleled of 2x6v in series.
Three BlueSeas switched MS favoured system of : house/emergency/Start
ACR to house +ve & Start +ve.
Fuses in approriate places.
New 50mm wire from start switch to starter +ve.
New 25mm wire from alt to house +ve & alt to negative common bus.(all batteries & block)

Switched house "on" all tests good. negligible VD.
Switched Start on & tried to start motor.As expected old start bat not up for it.
Turned start "off", Emergency "on" started instantly.
Checked charge voltage on house 14.2, 12.38 on Start.
Uhh-oh ...no neg wire on ACR for volt sensing. Shut down.
Check voltages again, 24.8V.....what! double check....24+V
OMG! Isolate batteries & check individually....all check out as normal.
Reconnect them as before and chk with DMM in all switch configs....12.8 & 12.38V.
Check with shore charger (too late to start engine again in marina) in all configs and cannot recreate the 24V!
What black majic is this?
 
B

Benny17441

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May 24, 2004
7,213
CC 30 South Florida
Can not get blood out of a turnip, check the calibration on your voltmeter. If you are sure that the series and parallel connections were correct then the only explanation is an incorrect reading from your metering tool or instrument. Where are you measuring voltage at?
 
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walt

walt

.
Jun 1, 2007
3,550
Macgregor 26S Hobie TI Ridgway Colorado
FYI, was this a cheap Harbor Freight meter and accidentally set to AC instead of DC when you measured that.. I remember from a long time ago this happened to someone with one of those cheap DVM's.. They measrued a DC voltage with the meter set on AC and it read TWICE the correct DC voltage. FYI, this is not the way a decent meter works.. but apparently some of the give away HF meters at least at one time did do this.

Woops.. I see you are in Auckland.. change that from a HF meter so something extremely cheap from China.

Some meters will also do odd stuff like that when the batteries are about to give out.
 
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S34

S34

.
Jan 3, 2016
17
Self built Stewart 34 Auckland
Benny17441 said:
Can not get blood out of a turnip, check the calibration on your voltmeter. If you are sure that the series and parallel connections were correct then the only explanation is an incorrect reading from your metering tool or instrument. Where are you measuring voltage at?
Click to expand
Connections are correct.(Apart from no earth to ACR) Not a lot to screw up. 24 is too much like 2x12 for my liking.
Measured at Nav table +stud, +ve take off on paralelled house bank, and +start all to neutral bus.
Suns up, I'm going to fire her up. Thanks for moral support. Get a bit low at 1am.
 
S34

S34

.
Jan 3, 2016
17
Self built Stewart 34 Auckland
walt said:
Woops.. I see you are in Auckland.. change that from a HF meter so something extremely cheap from China.

Some meters will also do odd stuff like that when the batteries are about to give out.
Click to expand
Yep, you nailed it. I'm cheap. Always looked at fluke with desire in my eyes, but little will.
DER EE DE-3100 AC clamp meter. dig ac/dc vm etc.
Ta for the heads up. I wont be buying a fluke just yet.......may need an alternator...sigh.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,343
Catalina 34 224 Maple Bay, BC, Canada
There are plenty of options between the cheap stuff and a Fluke. I've had a (USA) Radio Shack digital DVM for 35 years. Works just fine, but it ain't an ammeter too unless it's under 10A. RTFM:) You really can do better for just a little less cost.
 
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S34

S34

.
Jan 3, 2016
17
Self built Stewart 34 Auckland
Yep time for something a bit better. Those max and hold buttons are annoying too.
Always catching me out.

Something a bit weird. I charged the weak start bat with the Ctek charger and it went thru its cycles
finally dropping to float around 12.9v this morning. As soon as I plugged in the - ve on the ACR
it started climbing again. Like the ACR wasn't working properly?

I would have expected the house to slowly start climbing (which it did) and the start to maintain 12.9v
or slowly drop.
If I ever get a tattoo thats what it will be. Or, DOS.
 
walt

walt

.
Jun 1, 2007
3,550
Macgregor 26S Hobie TI Ridgway Colorado
By cheap.. I mean the $5 USD ones that Harbor Fright would about be giving away at store. The very nasty cheap ones can read twice DC voltage on the AC setting plus not being all that accurate. Yours (DE3100) doesn't look this cheap. The Lab where I used to work had a low end Fluke that would read twice the DC voltage when the battery was shot - but still enough juice to make you think the meter was working. In that instruments defense, I think the low battery icon was showing when it did this.
 
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S34

S34

.
Jan 3, 2016
17
Self built Stewart 34 Auckland
Well it was about $100 nz about 10yrs ago.made in Taiwan so well could be USA tech.
But you never can tell here, whats what.
Just ran up the motor. All good numbers with the Hitachi 55A alt putting 14.4----> 14.2V over 20mins on both banks.
Seems pretty ambitious for a hitachi?
Haven't hooked up the shunt etc so don't know the current.
Dunno what was up last night. Maybe I dreamed it. Moral of story is don't work at 1am , with flakey gear.
Thanks guys.
 
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