Volt meter

[sandman]

On my drifter 582 when flying, my volt meter is reading between 15-16volts. I thought the regulator charges the battery at 13.2 volts. I have a powermate regulator that's only 9 months old.

 

 

[Litespeed]

Your powermate regulator should be charging the system at a preset maximum of 14.4 volts

 

That is a typical charging voltage and quite normal.

 

If yours says 15-16 volts it sounds a bit inaccurate

 

What is the gauge you are using?

 

 

[Downunder]

Yeah. A bit high. Best to check if gauge is reading correctly.

 

A ground run with a multimeter connected should confirm or deny that reading.

 

 

[onetrack]

A lot of gauges are far from accurate, particularly if it's not a critical instrument.

 

If it really is charging 15 to 16 V, then your battery is suspect.

 

Batteries suffering from a degree of sulphation often have higher resistance to taking charge.

 

 

[cscotthendry]

Also check how the regulator is connected to the battery. On some systems I've seen, there is a fuse between the regulator and the battery. My Legend was built like this. If that fuse blows, then there is no load on the regulator. When that happens, the reg will overvoltage and possibly burn out.

 

 

[sandman]

The guage is the standard drifter guage I guess but I discovered it only reading this high when I blew a 5 amp fuse and drained the battery flat then recharged the battery overnight, since reinstalling the battery it has been reading high on the voltmeter, it has a 15amp fuse in the reg. but haven't checked that lately.

 

 

[facthunter]

If you are overvolting it will cause a lot of gassing and maybe breakdown of the battery particularly a low maintenance or "paste" battery, if it gets HOT. To look after a battery for a plane I would use one of those "relatively expensive " chargers that can be left on. I have them and use them often with motorbikes. You don't have to leave them on, It's just that if you do it doesn't wreck things. A solar powered one in the hangar seems like a good idea. It will work through a clear roof panel. You really don't need a SUSS battery in an aeroplane. A sulphated battery doesn't like taking a charge and may develop an internal short on one or two cells, so don't risk it if it's sat flat for a long time. (month or two).

 

A "healthy" battery will take a momentary high charge, when nearly flat (or a high discharge when it's charged.) That's one simple way of checking them I use . It only has to be momentary. Don't prolong it. If it's a small battery not used for starting the engine, observe makers charge rates. Nev

 

 

[cscotthendry]

If your electrical system is wired and operating correctly, (and you use your airplane more than once every 6 months) there should be no need for those "always left on" chargers. When your electrical system is off, there should be NO drain on the battery, except for possibly a clock which must stay on all the time, and generally these clocks only draw microamps in standby.

 

If your battery is being flattened between flights, either a) your battery is stuffed, or b) there is something constantly "on" in your system. From my observations with airplanes, the most common "always on" culprit is a miswired regulator.

 

There is a control wire that activates the regulator and I've seen a few cases where this activation wire is permanently wired to the battery, rather than through the master switch. This means that the regulator is working and trying to regulate the power system all the time. On the Rotax supplied regulators, this is the "C" input. Other regulators may have different designations for this input.

 

 

[facthunter]

Frost and cold temperatures will discharge a battery partly and there is always some internal leakage in a lead acid battery. By keeping it fully charged the sulphating is stopped from happening. Nev

 

 

[sandman]

problem sorted, faulty guage, as I checked the battery voltsge being 12.76v and the volt meter reading 14v. Reg was putting out 14.12v.

 

 

[facthunter]

That's what I would think is the correct figure for the regulator. Nev

 

 

[Pearo]

Your powermate regulator should be charging the system at a preset maximum of 14.4 voltsThat is a typical charging voltage and quite normal.

 

If yours says 15-16 volts it sounds a bit inaccurate

 

What is the gauge you are using?

This is not correct. The regulator should set the voltage correctly regardless of the state of the battery. The tip for detecting bad battery is when the charge current does not go down after time or if it there is no charge current at all (in which case you probably know when starting).

 

 

[facthunter]

Normal behaviour for say a fully charged (externally) battery after engine start is to have a significant charge current (at the right RPM for the engine generator if an old system, or less critically when the alternator energises at a lower rpm.) This is a good practical check of correct function. The starting has used some charge and the system should immediately try to restore it . Voltage readings are not required, and unless you know what loads are on the system, don't mean a lot. If the engine start was rapid , the charge rate should reduce within a few minutes. If you cranked it over for a while, it might take till in the cruise to restore the fully charged condition. This is why you should always start the day with a fully topped up battery charge wise. Nev

 

 

[Yenn]

You have no idea of what the charge current is with a voltmeter. Current measurement requires an ammeter.

 

I have Voltmeter only and can check the state of the battery, pre start, during cranking and then charging voltage.

 

I used a solar charger for several years with Odyssey batteries and I think it did more harm than good, they lasted only about 3 years.

 

I stopped using the solar 3 years ago and have one Odyssey which is still working from before that time.

 

 

[Pearo]

As always, I replied to the wrong post. My response was meant to be to onetrack, apologies to litespeed.

 

Yenn, best bet to understand battery state is to use both a voltmeter and an ammeter.

 

 

[facthunter]

A valid test is a high discharge rate with a voltmeter reading which is a bit dramatic. How your engine turns over when starting cold is doing that for you, without the gauges, if you are familiar with what "normal" is

 

A high charge rate charger will show battery condition. A crook battery won't take a high charge, when it's in a low charge state. It's internal resistance is not low enough. You don't have to do it for long. High rates of discharge and charge damage batteries. Nev

 

 

[Bruce Tuncks]

The use of the voltmeter is to see if your charging system is overcharging the battery or not. This will become more important as we change over to LiFe batteries, where a simple regulator system like on the Jabiru can damage the battery.

 

I use a digital voltmeter on the panel to switch out the battery as soon as the starting energy has been replaced and the voltage reaches 14.4. This is well before take-off.

 

 

[facthunter]

That may be a good thing Bruce, But the regulator should be reliable and it virtually does that job automatically if it is functioning correctly. Checking it and doing it manually is not something I would criticise. The only warning is with some alternators fitted to earlier GA planes , a flat battery MAY not allow the alternators to be energised, as they have a "start- run" two position switch. Your biggest worry is that a battery may start to short out due internal failure and develop heat and do a mini melt down. One cell only may fail and that makes the battery very suss. It won't accept a high charge rate and won't provide a high discharge current (as when starting). Don't keep a suspect battery in an aeroplane. It can make them quite unreliable. An "OLD" battery may still look as if it's fully charged based on voltage shown bit in reality have only a very small% of it's rated ampere-hours capacity. Only a high current test will pick this. You have one each time you start the motor. If the motor only "just" starts, and is not it's normal self (cranking speed) it may not charge very well subsequently, and could be about to let you down. Nev

 

 

[Yenn]

I have found that with my Diesel Prado that if the battery falters it is time to renew it. I have re charged batteries and they seem to work perfectly well for a few months, but suddenly they fail completely.

 

Knowing that, once a battery falters, it is out of my aircraft.

 

 

[facthunter]

It's not worth the risk. Depends on your machine. Sulphating is a cause of premature battery failure This is where white lead sulphate forms on the plates making them fairly useless at taking a charge, and likely to cause an internal short on one or more cells. Keeping your battery fully charged will prevent this. Low maintenance batteries have a clear viewer about 1 cm dia that shows green when charged. This type of lead battery is less likely to have acid leakage and corrosion associated with venting during the charge process so I prefer them . Nev

 

 

[Bruce Tuncks]

You are quite right FH, but lead acid batteries are things of the past. Just look at the cordless power tools in Bunnings. I actually owned a leaf-blower powered with a lead-acid battery, but these days it works with a LiPo duct-taped on and it is much better.

 

Well at 70, I'm a thing of the past too so don't feel hurt at the comment.