ProTech Battery Charger Problems

[ralay]

I have been slowly going over the absolutely anti-KISS electrical system in our boat over the past few months.  We have 3 battery banks (house, engine, windlass) tied together with a variety of isolation switches, combiner switches, and automatic charging relays. 

(A diagram of the battery and charging system can be found as the third photo down here: http://www.peanutbutterdiet.blogspot.com/2012/12/12v-revamp-episode-4.html)

While questioning the sanity of the current setup, I noticed a mystery current that was allowing the LED cabin lights to be dimly lit even when isolated from the house battery by turning the house battery isolation switch "off."  When isolated from the house battery, the house breaker panel is only connected to one of the charging leads from our ProTech battery charger.  I'm not totally sure why the previous owner decided to hook it up to the load side of the battery switch, but he did.  Also, the charger was not hooked up to shore power for any of this, so I knew the current illuminating the lights had to be coming from an unexpected source on the boat.  I pulled the fuse in the charging lead from the battery charger and the lights went out.  I decided that the current might be coming through the battery charger from another battery.  I replaced the first fuse and pulled the fuse in the lead for charging the windlass battery.  That would also cause the lights to go out. 

I have groaningly concluded that the battery charger will allow small currents to flow between batteries through the charging leads and the charger itself.  The current must be small as it will only power an LED bulb, though not any of the halogen bulbs.  Still, it is not possible to have the batteries truly isolated while the charger is installed, well, unless I pull the fuses every time we leave the dock.  The manufacturer has only suggested that I connect the charging leads directly to the positive terminals of the batteries.  Obviously, this will correct the problem of being able to see the problem via the lights, but it will still allow each battery to pull small currents from the others without any switches to interrupt the flow. 

I'm curious if anyone else has noticed that a battery charger is allowing small currents to flow between their batteries.  I also wanted to mention that if anyone is considering buying a ProTech battery charger for multiple batteries, and if it's anything like ours, it may run hot, noisily, and undo any other work you've done to isolate your batteries.

[Captain Smollett]

I really cannot offer specifics to your situation since our electrical system is a single bank.   But, here are some thoughts just for gee whiz.

a variety of isolation switches, combiner switches, and automatic charging relays.

Single circuit On/Off switches are, imo, the way to go.  

http://www.defender.com/product.jsp?path=-1|328|51495|299265&id=589840

I think combiners are over complication.  Now, that said, using a single-circuit switch on each circuit requires more 'thought' by the user...turn one off before another on (if you have more than one bank feeding different uses, for example).

 Still, it is not possible to have the batteries truly isolated while the charger is installed, well, unless I pull the fuses every time we leave the dock.  

On/Off single circuit switches will allow at least isolation.  You may not need to keep the charger on all three banks while you are gone.  Turn two off and only keep charging on the 'critical' bank, charging the other two when you are there and can isolate each in turn.

The manufacturer has only suggested that I connect the charging leads directly to the positive terminals of the batteries.  Obviously, this will correct the problem of being able to see the problem via the lights, but it will still allow each battery to pull small currents from the others without any switches to interrupt the flow.

Are you sure about this?  I'm blanking on the current flows in my head at the moment and what you are describing. At the very least, I would wire it the way the manufacturing says.

Looking at the diagram you posted, over-complicated is an understatement.  The Protech 1225i is a 3 bank charger and I'd very very surprised if the current leak is internal to the charger; bank isolation would be one of the things they should be getting right.  I could well be wrong, though.

Final thought:  wiring, especially on a boat, benefits from simplicity.  Complicated setups "designed" to make it easier for the end user are just inviting stray currents like you are seeing.

Try this:  Disconnect the charger from one bank...say the windlass bank.  Wire the charger directly to the other two banks and eliminate all those switches/combiners.  Keep the leads as short as possible and as direct as possible.

If you do this...cut the system to two banks and as simple and direct as possible, do you still have the leak?

[SalientAngle]

It may be neutral is carrying current to ground as well... finding the fault is the trick

[ralay]

Well, I disconnected the charger (which totally resolved the problem without having to change anything else), popped the face plate off of it, and measured the resistance directly between the positive terminals for the charger leads.  The resistance between any two of the three terminals was 200 ohms.  That would allow a small current of 60 mA at 12V, no?  Is that an acceptable application of Ohm's law?

If so, that would be enough to explain the dimly lit LED lights. I think individual LED diodes draw ~20 mA.  On the other hand, it would take >1000 hours to drain one of the batteries through the charger 60 mA at a time.  Maybe that's not worth worrying about.  There are other changes I want to make to the set up, but I feel like the mystery current has been traced.

[Captain Smollett]

Not necessarily. On phone now; will try to post some more detail later.

[s/v Faith]

200 ohms woud be inline with the use of a large diode to isolate the banks.  The typical diode c
blocks used to isolate the output of your alternator could compound the proble as you may wind up with resistance in paralle.  sorry i did not look at your diagram, i am typing on a kindle from an ancorage at Trellis Bay in the BVI's recovering from the full moon party...

good luck w the poblem, hope you can get cruising soonest!

[Captain Smollett]

Okay, some more detailed thoughts.

I apologize up front if some of this insults your understanding.  I'm just trying to start at the baseline so we are speaking the same language.

(1) Measuring a resistance across two of the charger's leads when it's not connected to anything and not "on" probably does not tell you anything.

I'm pretty sure that I read that that model charger uses a 3 stage regulator (at it should) and since it has three banks, each bank has it's own such regulator.

There is sufficient circuitry (sometimes, microprocessor controlled, but I'm not sure about that model) between the two power out leads (for two banks) that making a measurement on the unit in any state other than "in use" is pretty much meaningless.

(2) Without the detailed schematic of the internal wiring, trying to pinpoint an internal cause may be a waste of time.

For example, those regulators have voltage sensing circuits (so the correct charging stage can be made active) implying transistors and internal diodes, each of which can give 'wonky' results when Vin is not applied...especially if your multi-meter is providing a bias voltage (as it is to measure resistance) in the absence of Vin.

If some of the regulation circuitry is on chips (as it might well be if digital processor controlled), the internal wiring of the chips means measuring resistance across chip leads can be VERY confusing. 

I've done a fair amount of board and component level troubleshooting and in my recollection, it can only be done effectively with the proper inputs applied and a schematic (and understanding of the schematic) to tell you what outputs are expected for those inputs.

(3) My best advice is to contact the manufacturer of the charger and ask a tech person very clearly and specifically if such a measurement SHOULD result in an open circuit with the unit off and not connected to anything, and if so, is this unit faulty?

(4) The charger could be suffering from some internal fault.

If the regulation circuitry on your charger is not working properly, for one or more banks, you will destroy your batteries.  There's a reason deep cycle batteries last longer with 3 stage chargers (vs two, like automobile regulators tend to use) and even with that, you may not know if the regulator is working at all...switching when it's supposed to, etc.

(5) LED's are of course biased, so the current can only be flowing in one direction to produce the light you see.  Try switching the leads from the charger to the respective banks.  If the light remains, I don't see how the fault can be simply attributed to a leak inside the charger.

Also, on a related thought, such a leak SHOULD be correlated to the regulator output stage active for BOTH banks involved in the leak.  If your LED's show variation in the brightness with different voltages, you may see this. 

(6) It's not an easy problem.  At all.  Simply things down to nothing but base elements.  Two banks, no charger, no switches, no distribution panel.  Is there a current leak?  No?  Add one thing at a time.  When it comes to adding in the charger, add it different ways - power lead 1 to bank 1, then power lead 2 to bank 1, etc.  One thing at a time.

And, keep notes.

Good luck.

[Captain Smollett]

Any update on this?

[ralay]

Not a productive update.

In response to your 1, 2, 3: I accept that it may be meaningless to take measurements with the device disconnected.  I haven't been able to get any technical information through the manufacturer's e-mail contacts.  I received what I suspect are rote responses to my initial questions and no further responses to my follow up questions.  One of these days, I'm going to sit down and try to pressure some information out of them through the phone contact, but I haven't got around to it.  I'm not thrilled about having to describe some of my questions over the phone rather than via e-mail where I can send/receive pictures.

We have the mast down, and I've been helping jw with the deck and working on other projects.  Some day soon I'll get a cup of coffee, patience, and the phone then proceed with more information.  Frankly, I'm inclined just to remove the charger as I can't detect any of the unusual symptoms as soon as the charger is removed.  As we are rarely ever at a dock while cruising, I don't imagine it'll see much use in the months after our refit.

[SalientAngle]

quick question ralay, do you have one negative bus or multiple?

[ralay]

There are a few intermediate ones that tie together various negative cables, but they all eventually lead to one common negative bus to which the engine is also attached.  I'd be interested to hear about how the configuration of the negative side of the system could affect this.  Most books just put a little "to ground" symbol and never say anything else about that half of the system.  Asking folks around here, I've got mixed responses on whether it's alright to combine negative leads (via bus bars and a single larger cable) before the common bus bar.  Some people have said that it doesn't matter as long as it all leads back to common bus eventually.  Others have said that all the negative leads need to go back the negative terminal of the battery their associated with before going to the common bus.  Hard to know who's right as references seem to gloss over it.

[SalientAngle]

raylay, isolate dc negative from engine and any other bond and see if problem still exists.

[ralay]

Alright, I called the phone number for tech support I found in the manual and was immediately put in touch with a helpful and knowledgeable person.  I should have gone that route in the first place.

The short answer, as I understand, it is that, yes, the charger will let very small currents pass through it.  The currents should be on the order of 15mA.  The company considers this negligible.  The technician didn't sound surprised that the leads weren't an open circuit or that disconnecting the charger fixed the symptoms.  Basically, he said that unless the flow was in amps, it was likely it was just the charger and not to worry.  I'm inclined to call it settled.

I thought of a different, more troubling issue as I was looking through the manual for the phone number.  Our boat doesn't have an AC system.  The charger has a 3 prong, AC plug running directly to an extension cord on the dock.  I had always assumed the charger came with the plug until I noticed the instructions for wiring it into the boat's AC system.  The unit has both an AC ground wire and a DC chassis ground from the metal case to the common ground of the DC system.  I asked the technician if this had the potential to link the negative side of the DC system to the AC ground.  He said, yes, the unit was intended to be installed on a boat with a permanent AC system (with its requirement for a galvanic isolator) and that he wouldn't recommend installing one without going through a galvanic isolator.  *sigh* Whoever draws the short stick is going to jump in for a look at the zincs while we think about what to do with this charger...

[marujo_sortudo]

If you decide to wire it up properly, Maine Sail did a nice write up on GI's recently:

http://forums.sbo.sailboatowners.com/showthread.php?t=148402

[SalientAngle]

aha, and, if you don't plan on spending alot of time in slips with shore power, I wouldn't bother... recommend a "floating" dc system isolated from all water metal... much simpler imho... just $0,02 (your mileage may vary and all the usual codiciles apply)

[ralay]

Given our cruising behavior, I'm more inclined to sell the charger and put our money/time toward installing a solar panel or two rather than fuss with buying a galvanic isolator.  We spend so little time at docks while cruising that it doesn't make sense to put more money toward an AC-dependent charging system. 

[marujo_sortudo]

Sounds like an excellent choice.  We planned on never using shore power, and indeed, after 4 years of sailing the boat, I've plugged in twice.  Albeit, right now we're plugged in for a month as we take a long pause in Brunswick.  Our AC system is wired correctly and I've even tested our GI to confirm that it works.  That said, if the charger failed, I'd rip it out before I'd spend a dollar to replace it.  I'd rather spend boat bucks on power generation where we'd use it most, at anchor.