Voltage at the starter?

[Matata]

I'm considering moving my battery closer to the Beta 20 to get more kick. If I measured the voltage at the starter when the engine is been started what voltage would you like to see and below what voltage would you consider putting in new cabling and or relocating the battery, considering the battery (110 amp) is in good condition? Opinions appreciated Nik

 

[William_H]

Perhaps the best way of estimating the power at the starter is the enthusiasm with which it turns over. If it seems a bit doubtful then yes there is a problem. The voltage at the starter should be around 9 or 10 volts while cranking. Part of this low voltage will be caused by the battery voltage sagging but part will be due to loss in the cables.
A good trick is to connect the negative of your volt meter to the negative battery terminal (onto the actual post if you can) and the positive onto the body of the starter. When you crank you will measure voltage drop of the negative line. This should be I would guess less than .5 volt.
You can do something similar with the positive line and again this should be less than .5 volt. This drop will include your battery power switch and wire. You can move the meter to across the power switch contacts which may be giving a loss.

.The volt drop of the cables and switch should be small compared to the drop of the battery voltage at the terminals of the battery.

good luck olewill

 

[dovekie]

Yes, agree with William H that you can measure the drop as he says. The proportion of power lost in the cable, rather tahn used in thestarter, will be the voltage drop divided by 12 I think. I'm not sure what drop is acceptable - I guess if it cranks vigourously and starts, it's acceptable. One thought rather than move the battery, if you do find you have a problem, would be to put fatter cables on with good crimped terminals. I've just put 95mm2 cables with a 1 metre run on a beta 38. I'll measure the drop and post it here for you if that helps.

 

[MoodySabre]

Two things

My battery is very close to the starter but the cables run a long way to the battery switch before going to the starter - must be 3 metres total at least. So if you move it nearer then the battery switch or isolator will need to be near too.

A volt drop test through the system might show up a poor connection that is causing the drop in amps to kick the engine. How to perform a drop test here

 

[boatmike]

Also see my post on recent thread re cable sizes. If you have current drop ensure you have adequate cable

 

[Amulet]

Seem to recall Nigel Calder says a loss of 1.5 volts is acceptable - too lazy to go and look it up. I lose about 0.8 on a voltage drop test.

 

[NorthUp]

95mm!
no problems with voltage drop, but did you use welding cable?
The danger with heavy cable like this is lack of flexibility, especially if the engine is on flexible mounts.

 

[dovekie]

Good point. I know nothing technical about cabling, but the stuff I used is very flexible, hundreds of tiny strands of copper, rather than dozens of approx 1mm strands. Hope it's OK.

 

[NorthUp]

Sounds like welding cable. The fine strands are more susceptible to the effects of corrosion, but sealed at the crimps with tape, you should be OK.
If you ever re-engine , you can re-use it, its good for engines over 1000HP!

 

[Matata]

You learn something every day! I'll keep you posted. I'f all holds out 'till late summer ,will check things over and may recable this winter if there is a problem found. The present cables don't look great either size wise or condition and maybe a simple rewire might sort things out. Just one futher point. Does the 4 way knob work by activating relays/solenoids or is it purely mechanical? Ta Nik