El martes, 14 de julio de 2020, 10:04:48 (UTC-3), AS escribió:
On Tuesday, July 14, 2020 at 12:11:22 AM UTC-4, 2G wrote:
On Sunday, July 12, 2020 at 3:13:50 PM UTC-7, wrote:
For those who own Ventus Cm: have you ever measured the voltage on the starter when it is running?. Mine, with fully charged battery, while electric starter is running, voltage on battery fall out to 10volts, and on starter I measured only 6 or 6.5 volts. I have a voltage lost of aprox 2 volts over the positive wire and 1.5 over the negative one. Is that normal? I have starting troubles sometimes and i think it is because of it. What can you tell me about it?

The inrush current demand of a starter can be as much as 150 amp. Obviously, any resistance in the circuit (and I do mean any) will result in a substantial voltage drop, but not 3 - 3.5 V. You have a corroded connection somewhere. Replacing the cables WILL NOT solve the problem (unless they are damaged). You must find the bad connection(s). Taking everything apart and polishing them down to bright metal is the solution.

Your battery is bad and needs to be replaced (no surprise there). Typically they have 10 milliohms of internal resistance which means a 1 V drop at 100 amp. Any more means the internal resistance has gone up to the "toss it" level.

Tom

You can get a relatively inexpensive IR camera for your smart phone and take a look at the whole system while starting. Bad connections will show up quickly as hot-spots. Great trouble shooting tool.

Uli
'AS'

Thank you all for all the answers and advises.
I´ll try to reasume all the thing I´ve done on my glider.
This glider belonged originally to David Noyes (NL) in USA.
I bought it in 2017 to its 3rd owner C. Collman and imported to Argentina.
Since then, it started regularly but always with very few power, giving me doubts if i had to restart while flying to fly back home. Fortunately, it started all the times I really needed. (no more than 6)
I made a service to the original electric starter and it improved a little.
After one and a half year, dec 2018, first thing I replaced was Battery. I bought an Odyssey PC680, 12V 16Amp... but the problem was not yet solved.
Last year I decided to bought a new starter (the same as original), new relay (the same as original) and new coils and of course new spark plugs, and sparkplugs cables, etc etc.
I changed everything while applying an AD (propeller bearing replace) last year, and during last summer it seemed to be doing well.(we also found other problems that were repaired)
Now, after quarantine, I noticed the starter was running slow again and I began to inspect the electric installation.
This glider`s electric system is very simple: The positive wire goes from the battery directly to a 50Amp masterswitch/fuse. Then goes directly to the relay and then to the starter. The negative wire goes directly from battery to the engine pylon where starter is screwed.
The drops of voltage are (divided by section):
0-On battery: 3V. !! (measuring battery poles) (no voltage drops on connector)
1-from battery to fuse: 0.3V.
2-on the fuse: 0.22V.
3-from fuse to relay: 0.85V
4-on the relay: 0.2V
5-from relay to starter: 0.55V
Total drop on positive wi 2.12V (the drops on the wire are proportional to the lenght of each section of wire) (total lenght of wires is more than 5 meters)
Total drop on negative wi 1.4V
Total drop of voltage: 3.5V + 3V (battery) = 6.5V. Voltage on starter is 6.2 when battery is 12.7 !!
Tests done duplicating wires improves 1.4 volt on the starter. All the contacts are in good condition and clean.

So, the battery is a very good one (at least that is what the seller told me and what i could investigate myself) and is 1.5 years old, used for no more than 100/120 starts (including all the test I did).
The relay is new. The starter is new….( Less use than the battery)
I can't find a certain place where there are point voltage drops. I'm totally lost. I don´t want to buy a new battery and find that wasn´t the problem.

Next to do, I will measure the current with a DC Amperimeter in order to check if starter is consuming more tan normal.. It is labeled 400W, so it should consume no more than 35 Amp. And I will try to get borrowed another battery to compare.

One thing to make clear: once the engine starts it runs perfectly with any problem. Never stopped itself. No carburation problems.

But i am thinking now:… Could the engine be hard? Heavy? Even if i decompress it to start spinning

Regards,
Lucas