Swollen old PC680...overcharging, or just age?

[MacCool]

I run two PC680's on the firewall. One of them is 3 years old, the other is over 6 years old. Two separate contactors on a split master switch, but they are wired in parallel. The electrical system normally will run from either or both master switches on. The (single) alternator charges both.

The other day, after a normal flight with engine off, I hit the right master switch in order to put the flaps down....all I got was "click click click". I turned the other master switch on and everything worked normally. I pulled the cowl, checked voltages directly, and the three-year-old battery read 13.8 volts, the 6 year old battery read 10.1 volts. Load testing showed complete failure of the older battery. I removed it and noted that it was quite swollen. I have a new one coming from Amazon.

Normally when in the hangar, the batteries are both kept on an Odyssey 6-amp charger (with "desulfation" mode), charged in parallel.

Is this a typical failure mode for an old, work-out AGM battery? I know that most swollen batteries are due to overcharging, and I gather that that is more likely to happen with age, but I'm wondering if I should be looking harder at the charging circuit, or consider a different float charging method. During flight, EMS indicates normal volts and normal amps.

 

[rocketman1988]

battery

Unfortunately, I have seen batteries like that before; my tug has 4 AGM batteries in it. I came to the hangar and found the tug inop and the top plastic cover warped and discolored.

Removing the cover, I found all 4 batteries swollen and soft welded together. Removing them, I had to drop them on the ground to separated the plastic cases.

Long story short, apparently, I left the tug arm switch turned ON while the automatic charger was in charge mode. Powering the electronics prevented the charger from completing the charging process and switching to float mode...so it continued to charge and overcharge the batteries. Basically cooked them.

It is an older charger built into the tug; the newer chargers wouldn't have done this. It was a $375 mistake. Lesson learned.

Point of the story is to make sure your chargers are functioning correctly if you are going to leave the batteries connected all the time.

 

[Ironflight]

One of the great things about the Odyssey batteries (when we first started using them in airplanes 20 years ago) was that you could leave them sitting for a year (or more) and they would still start the airplane just fine…no trickle charging, no water checking, no nothing. I have never trickle shared any of mine, and get five or six years on them. You seem to fly regularly enough - I’d skip the trickle (regardless of the brand of charger) and let the battery do what it was designed to do. It is, after all a “storage battery”……

I personally think more AGM batteries are killed by overcharging than anything else. And I‘ve never seen an Odyssey bulge like that!

 

[Mike S]

Totally agree..

I personally think more AGM batteries are killed by overcharging than anything else.

Lots of prior info posted here in VAF going back many years tend to support this.

 

[airguy]

Agreed - unless you are going to leave the airplane on the ground for multiple months, there is no need for the float.

 

[MacCool]

I personally think more AGM batteries are killed by overcharging than anything else. And I‘ve never seen an Odyssey bulge like that!

Agreed, but it should be impossible (ok..."unlikely") for a quality float charger to overcharge a lead acid battery. The newer identical battery has been treated the same for 3 years and is very healthy. I have an unknown amount of maintenance drain from my avionics, and I'm incented to keep the batteries fully charged as freezing during the winter becomes more likely as storage discharge progresses (this is Minnesota...-30° F is not rare in the winter, and I don't fly near as often).

However, point taken. I think that while I'm connecting and disconnecting batteries as I address this issue, I'll take the opportunity to measure current at rest in order to get a handle on parasitic drain from the avionics.

 

[lr172]

bulging SLA batteries is not an uncommon fault, though I don't know exactly what causes it. TIP: DO NOT charge two batteries on the SAME charger. These chargers have some intelligence to step through the phases of charging and it doesn't work correctly when connected to two batteries. For example the weaker battery will keep the voltage low, so the charger keeps on going and overcharges the good battery, venting electrolyte, etc. Unsure if this is the cause of your issue or not.

Larry

 

[lr172]

Agreed, but it should be impossible (ok..."unlikely") for a quality float charger to overcharge a lead acid battery.

See above. charging two batteries on one charger can easily over charge one of them. A modern charger looks at current draw and voltage to step between 3 or 4 different phases of charging. The guy writing the logic didn't assume someone would put two batteries on it and there is no way for it to know how many batteries are attached, therefore it keeps treating it like one battery. WHen connected to one battery, it is unlikely they will overcharge. That said indefinate floating can trash a SLA battery, which is why the odyssey charger doesn't float; It monitors for voltage drop, then starts another charge cycle instead of a contant float like a battery tender. This is unique behavior; Most chargers just continue to float once the charge is complete. Battery tenders SHOULD NOT be use on SLA batteries. They are made for flooded lead acid batteries and work relatively well on them.

 

[MacCool]

See above. charging two batteries on one charger can easily over charge one of them. A modern charger looks at current draw and voltage to step between 3 or 4 different phases of charging. The guy writing the logic didn't assume someone would put two batteries on it and there is no way for it to know how many batteries are attached, therefore it keeps treating it like one battery. WHen connected to one battery, it is unlikely they will overcharge. That said indefinate floating can trash a SLA battery, which is why the odyssey charger doesn't float; It monitors for voltage drop, then starts another charge cycle instead of a contant float like a battery tender. This is unique behavior; Most chargers just continue to float once the charge is complete. Battery tenders SHOULD NOT be use on SLA batteries. They are made for flooded lead acid batteries and work relatively well on them.

It's a good point, and I called Odyssey 3 years go while wiring the charging pigtail to ask about that. I was told at that time that such charging in parallel "should not be a problem" if the batteries were the same model and were in similar condition, and if using one of their Odyssey chargers, which I am. That said, the bulging of one battery and not the other does suggest that that older battery had been overcharged. I can see how the age of the dead battery may have caught up with it and lead to it being killed by overcharging in the scenario you pose. The concern is that the age difference between the remaining good battery and the new one I've bought is the same as the age difference of the previous two. Likely worth a call to Odyssey and ask again. Thanks for the input.

 

[lr172]

charging in parallel "should not be a problem" if the batteries were the same model and were in similar condition, and if using one of their Odyssey chargers, which I am.

That is true. However, you have no real way to know if both batteries are in similar condition, at least not after they have been in service for a while. Also, the two batteries must be at the same state of charge for this to be correct. All of this applies to modern 3/4 stage charges and not to to the older simple chargers.

 

[MacCool]

That is true. However, you have no real way to know if both batteries are in similar condition, at least not after they have been in service for a while. Also, the two batteries must be at the same state of charge for this to be correct. All of this applies to modern 3/4 stage charges and not to to the older simple chargers.

Yeah. No good way to know the relative health of the two batteries, but reasonable to assume that a three year-old battery will have more sulfation and therefore be closer to its EOL. Also reasonable to assume that that would be why my older battery overcharged and puffed.

I appreciate your post...put me on a different line of thought.

 

[lr172]

Yeah. No good way to know the relative health of the two batteries, but reasonable to assume that a three year-old battery will have more sulfation and therefore be closer to its EOL. Also reasonable to assume that that would be why my older battery overcharged and puffed.

I appreciate your post...put me on a different line of thought.

Sulphation, generally speaking, does not occur from age alone. It starts occurring once the battery drops below a specific charge level. somewhere aound 80% IIRC. The lower it goes below that level and the longer it stays there, the more sulphation occurs. On the age issue, each discharge cycle moves lead particles from the lead plates to the electrolyte. The greater the discharge depth, the more particles that move. This can only go one for so long and eventually the plates get thin and don't perform well. This is the classic age failure for batteries and the reason that deep cycle batteries are so heavy (the greatly increase the size of the plates to deal with it). I rarely discharge my car battery beyond starting and my batteries last for 7 years plus. My wife is always leaving her interior lights on and rarely gets more than 3 years from her battery.

 

[clam]

bulging SLA batteries is not an uncommon fault, though I don't know exactly what causes it. TIP: DO NOT charge two batteries on the SAME charger. These chargers have some intelligence to step through the phases of charging and it doesn't work correctly when connected to two batteries. For example the weaker battery will keep the voltage low, so the charger keeps on going and overcharges the good battery, venting electrolyte, etc. Unsure if this is the cause of your issue or not.

Larry

Thoughts on this equipment? I installed this on a boat, but they also claim it may be used with many of their aviation chargers.

https://www.batteryminders.com/multiple-battery-connector-210-AY

 

[Adam]

Well, I have an Odyssey battery that’s been in the plane since I built it 15 years ago. I know that sounds crazy and trust me I’m amazed that it works every time but it does. At annual I check it, I don’t trickle charge it and I honestly for the last two years don’t fly the airplane as much as I should, but it keeps on cranking! Now I’m sure when I go to fly it this week it probably won’t start

 

[tjo]

I am not a battery expert, but do have some experience with them. Your typical flooded lead-acid battery is vented so that pressure does not build up inside the case and cause swelling when you get high temps or overcharging conditions. The downside is venting acid can cause (or does cause) damage and you have to refill them. AGM batteries, on the other hand, are "sealed". As a result, they don't vent when overcharged or overheated, and will swell like this if the internal pressure and environmental temperature is too high. The problem is, if you allow the pressure to build too high, the case will break, which would be very bad, so they do have a pressure relief valve built in. If they overheat due to overcharging or hot environment, consequently overpressure, and vent, there is no way to tell and no way to refill, so they just experience an accelerated failure. Each overcharge and/or overtemperature cycle causes more venting, in turn making it easier for the battery to overcharge or overtemp. The short answer is what was stated above; don't trickle charge and try to keep the battery as cool as you can.

Tim

 

[lr172]

Thoughts on this equipment? I installed this on a boat, but they also claim it may be used with many of their aviation chargers.

https://www.batteryminders.com/multiple-battery-connector-210-AY

That just allows a trickle or float charger to connect to to different batteries at the same time. Perfectly acceptable for flooded lead acid batteries, like on boat. Not recommended for an actual battery charger (at least not a modern multi-stage charger) and I do not recommend float charging SLA batteries. Self discharge rate is very low on SLA, so no need for one, unlike a flooded LA.

 

[newt]

One of the great things about the Odyssey batteries (when we first started using them in airplanes 20 years ago) was that you could leave them sitting for a year (or more) and they would still start the airplane just fine…no trickle charging, no water checking, no nothing.

Interesting that you say that.

I've never had that outcome. In all the time I've owned the airplane, I've always had to put it on the charger to get a good start after an extended period of idleness. Especially if the battery is more than about 3 years old.

I'm not over charging them (Plane Power internally regulated 60 amp alternator). And, after completely rewiring the airplane 2 years ago I know there are no parasitic loads on it.

Granted, as a PC-625 it's smaller than the usual Odyssey on RVs, but it's also a bit lighter and has roughly the same CCA according to the spec sheet.

In my experience the AGM batteries do lose some grunt if they're not regularly charged. Enough to be lethargic across the first compression stroke after four or so weeks anyway.

Having said that: My understanding is that AGM wants a slightly higher output voltage from the alternator, but I can't adjust the Plane Power regulator, so maybe mine is never quite getting charged enough?

(I've just ordered a new battery, after my 3 year old PC-625 couldn't start the engine at all after being cold soaked all night at -1ºC last weekend. Cold temperatures aren't really good for anything at all, huh)

- mark

 

[lr172]

Interesting that you say that.

I've never had that outcome. In all the time I've owned the airplane, I've always had to put it on the charger to get a good start after an extended period of idleness. Especially if the battery is more than about 3 years old.

I'm not over charging them (Plane Power internally regulated 60 amp alternator). And, after completely rewiring the airplane 2 years ago I know there are no parasitic loads on it.

Granted, as a PC-625 it's smaller than the usual Odyssey on RVs, but it's also a bit lighter and has roughly the same CCA according to the spec sheet.

In my experience the AGM batteries do lose some grunt if they're not regularly charged. Enough to be lethargic across the first compression stroke after four or so weeks anyway.

Having said that: My understanding is that AGM wants a slightly higher output voltage from the alternator, but I can't adjust the Plane Power regulator, so maybe mine is never quite getting charged enough?

(I've just ordered a new battery, after my 3 year old PC-625 couldn't start the engine at all after being cold soaked all night at -1ºC last weekend. Cold temperatures aren't really good for anything at all, huh)

- mark

You can do the research, but I vaguely remember that the self-discharge rate, which is what the battery loses from sitting idle with no load, was around 5-10% of charge state over 6 months for sealed lead acid. A flooded lead acid is somewhere around 10-15% per month. If you fly and come back to a weak sluggish battery after a month, I suggest that you have in issue somwehere, as that is not normal. Could be a bad battery, a wiring issue, an alternator issue, some parasitic draw, etc. I have done many starts at 0F and it still cranks with authority even after sitting for 2 or 4 weeks. Have never had the need to charge the battery other than when I drained it for some reason. The battery in my 6 has been in service for at least 4 years and notice no degradation from new. I am sure there is some, but it is not noticeable in the cranking authority.

 

[MacCool]

One of the great things about the Odyssey batteries (when we first started using them in airplanes 20 years ago) was that you could leave them sitting for a year (or more) and they would still start the airplane just fine…no trickle charging, no water checking, no nothing. I have never trickle shared any of mine, and get five or six years on them. You seem to fly regularly enough - I’d skip the trickle (regardless of the brand of charger) and let the battery do what it was designed to do. It is, after all a “storage battery”……

I personally think more AGM batteries are killed by overcharging than anything else. And I‘ve never seen an Odyssey bulge like that!

The bulging was impressive, and almost certainly due to overcharging. I was. shocked. As mentioned, I suspect it was due to the age difference between the two batteries...Odyssey actually warned me about that years ago when I called them to ask about float charging two batteries in parallel.

As opposed to 20 years ago, parasitic draw from on-board electronics these days is what leads me to constant float charging my system. I don't know what that parasitic draw is, but I know roughly what it supposed to be. I'll measure it today when I wire in the new battery (arrived from Amazon yesterday). That parasitic draw may aid me in coming up with a more rational charging scheme (or lead me down a rabbit-hole search for a short, I suppose).

One thing I'm contemplating...only using one battery and leaving the second as backup, engaging that master switch only in the event I would ever need the extra amp-hours. That would leave the alternator only charging one battery instead of two while the engine is running. Maybe it's a bad idea to ask my alternator to charge two batteries. Opinions?

 

[lr172]

The bulging was impressive, and almost certainly due to overcharging. I was. shocked. As mentioned, I suspect it was due to the age difference between the two batteries...Odyssey actually warned me about that years ago when I called them to ask about float charging two batteries in parallel.

As opposed to 20 years ago, parasitic draw from on-board electronics these days is what leads me to constant float charging my system. I don't know what that parasitic draw is, but I know roughly what it supposed to be. I'll measure it today when I wire in the new battery (arrived from Amazon yesterday). That parasitic draw may aid me in coming up with a more rational charging scheme (or lead me down a rabbit-hole search for a short, I suppose).

One thing I'm contemplating...only using one battery and leaving the second as backup, engaging that master switch only in the event I would ever need the extra amp-hours. That would leave the alternator only charging one battery instead of two while the engine is running. Maybe it's a bad idea to ask my alternator to charge two batteries. Opinions?

The alternator is a single stage charging device (it is really not a charging device, but a variable amperage, constant voltage power source) and it is completely acceptable for it to charge two batteries in parallel (many trucks do exactly that). It is the intelligent multi-stage chargers that should not be used on multiple batteries, as they need to sense the charge absorption to change stages.

 

[Carl Froehlich]

SNIP

Having said that: My understanding is that AGM wants a slightly higher output voltage from the alternator, but I can't adjust the Plane Power regulator, so maybe mine is never quite getting charged enough?

Two comments:
- Your buss voltage with the engine running will tell you what voltage is being put out of your alternator. The Plane Power ones I’ve seen are right at 14.2vdc - just fine for an Odyssey battery.
- If you really want to increase alternator output voltage this can be achieved by inserting a diode inline with the alternator sense voltage. Depending on the diode, this will result in a 0.2 to 0.6vdc drop in what the alternator is sensing as buss voltage - and provide a corresponding increase in output voltage to the plane. BUT, I suspect you don’t need this or want this.

Carl

 

[Snowflake]

Well, I have an Odyssey battery that’s been in the plane since I built it 15 years ago. I know that sounds crazy and trust me I’m amazed that it works every time but it does. At annual I check it, I don’t trickle charge it and I honestly for the last two years don’t fly the airplane as much as I should, but it keeps on cranking! Now I’m sure when I go to fly it this week it probably won’t start

I'm in a similar boat... The Odyssey that I installed a year or so after i bought the plane is now 12 years old and has lived on a trickle charger 24/7 when in the hangar (apart for a 3 year period when I was in a hangar with no power). It's only just started to seem like it might be getting sluggish on the first blade, i'm planning on a replacement at this year's annual.