engine voltometers vs el. panel voltometers Q

[vas]

good evening,

was about to ask that last year but forgot, now that I saw Piers thread on multicharging I thought I might as well send mine too

So, charging system seems to work fine with a Victron charger and engine alternators. I very rarely turn the engines when on the dock on shore power simply because I don't have shore power except in v.few occasions.
My problem is with the engine alternators themselves and not in relation to the Victron. Bear with me.

So, cruising at 1300-1500rpm 7-8kn at the beginning the VDOs on the dash show 24V then go to 28V and then zoom to over 32V
Initially I was scared looking at them up there, but after checking that batteries (open LA) were fine, levels were fine, I got used to it.
Now, once charged (I guess) they flick from 29V to 33V+ and then back again (say every few mins) and goes on and on for ever.
For the record, port engine does the service bank so hard work and always in need of some charge, whereas stbrd does bugger all, well starter batteries so often is more towards the 34V.

Throughout that time, the el. panel Voltometer (nice old one with a lovely needle) shows a fairly steady 28 (or thereabouts) which is as much as I see when the engine is off and the Victron is working (either via shore power or genny). Drops to 24 or even less after half a day on anchor, should improve with 600W of solar panels on the HT.

So, should I worry, should I have a look at the alternators, or forget it and get on with life? Anyone can relate these stages to float/charge or whatever my IVECO engines stock alternators can do?

following three pics show what I'm talking about, sorry too many light reflections but that's the only pics I found after a quick look

cheers

V.

 

[kashurst]

There's probably not much wrong, but first verify that all your gauges are measuring what you think they are measuring and check they are reasonably accurate. Get a reasonable multimeter even a cheap DVM is pretty accurate these days. Go from there. If you aren't boiling your batteries it's a wiring/instrumentation issue. The voltage going up and down is probably the charging system turning on and off as it senses voltage drop. Also if you have a split charge diodes, your meters could be measuring alternator output not battery voltage

 

[rafiki_]

Agreed. You should see 28 ish when fully charged. Check this with your multimeter. My guess is the system is working fine, and a couple of the gauges are reading high.

 

[vas]

There's probably not much wrong, but first verify that all your gauges are measuring what you think they are measuring and check they are reasonably accurate. Get a reasonable multimeter even a cheap DVM is pretty accurate these days. Go from there. If you aren't boiling your batteries it's a wiring/instrumentation issue. The voltage going up and down is probably the charging system turning on and off as it senses voltage drop. Also if you have a split charge diodes, your meters could be measuring alternator output not battery voltage

I'm pretty confident that the el.panel Voltometer is fine and shows what it should, I've cross checked with a 20euro digital voltometer numerous times on the battery terminals.
tbh, haven't got a clue where these two VDOs are hooked up to! Have to investigate!

Used to have all sorts of odd things plus a 30kg old (as in 1975 old) battery charger complete with a analogue as in watch mechanism timer which went for metal recycling plus a split charger that was absolutely pointless with the Victron which can do 3 separate banks (that was also there when I bought MiToS)
I'd expect the VDOs to measure current produced by the alternators, no? If it was going to the batteries, it would certainly show on the el.panel Voltometer which has a toggle to show either starter or service batteries voltage but as I said this shows normal values always, never gone north of 28V.

Agreed. You should see 28 ish when fully charged. Check this with your multimeter. My guess is the system is working fine, and a couple of the gauges are reading high.

Paul, yes that's what I'm thinking, however wonder why and if anyone is getting such an issue.

Also wonder what's the proper wiring for engine voltometers, I'd expect them to show what current they are producing. The el.panel can give me what is going to the batteries.

cheers

V.

 

[rafiki_]

Also wonder what's the proper wiring for engine voltometers, I'd expect them to show what current they are producing. The el.panel can give me what is going to the batteries.

cheers

V.

Not sure I understand this Vas. The voltmeters will show the volts only. Need an ammeter to show current. Have I missed something? I believe the ammeter on my Azi shows the current being drawn by the service battery set.

Apologies if I have misunderstood.

 

[vas]

Not sure I understand this Vas. The voltmeters will show the volts only. Need an ammeter to show current. Have I missed something? I believe the ammeter on my Azi shows the current being drawn by the service battery set.

Apologies if I have misunderstood.

nope, my mistake Paul, thinking in Greek and we often interchange words (wrongly!)
of course I meant that VDOs will show the voltage produced by the alternator, and the el.panel Voltometer the voltage going to the actual batteries (for sure it does that!)
I should get a wire from the alternator and the other to ground and measure with the engine running.

cheers

V.

 

[rafiki_]

Just measure at the back of the gauge Vas.

 

[BartW]

Just measure at the back of the gauge Vas.

all agreed,
also KH post #2

I have recently replaced 2 x VDO Volt gauges on the FB dash,
but the new ones are not much more accurate than the 25yo models
(and checked with a DVM at the gauge terminals)