Perplexing battery problem

[david100952]

I have trawled through the numerous threads on batteries/charging questions and cannot find a similar case to address my query. My starter battery seems to slowly lose its ability to turn over the 1GM10 after a few weeks and a half a dozen uses.

I have a small cruiser (sail) and have a house and starter battery system controlled by a BEP VSR cluster. I keep the batteries ashore in winter and keep them topped up with a "smart" charger on maintenance cycle which seems to work well as they both return to service in spring with full charge and work well. I replaced the Hitachi 35 amp alternator last year to try and solve the problem and have completely rewired the system and checked that I do not have any "leaks". I am sure the VSR is wired correctly and checked the voltage going in to the start battery at 13.7 when the engine is running. When I charge the start battery with my shore powered charger it takes a full charge and starts the engine well afterwards but after a few weeks it wont turn it over by itself and I have to use the bypass switch and put both batteries on line to start the boat.

Short of buying new batteries I have addressed every possibility and I still cant find out why this is happening. I have not replaced the batteries because I had them tested by a marine engineer and they are fine. - HELP!!!!!!

 

[VicS]

I have trawled through the numerous threads on batteries/charging questions and cannot find a similar case to address my query. My starter battery seems to slowly lose its ability to turn over the 1GM10 after a few weeks and a half a dozen uses.

I have a small cruiser (sail) and have a house and starter battery system controlled by a BEP VSR cluster. I keep the batteries ashore in winter and keep them topped up with a "smart" charger on maintenance cycle which seems to work well as they both return to service in spring with full charge and work well. I replaced the Hitachi 35 amp alternator last year to try and solve the problem and have completely rewired the system and checked that I do not have any "leaks". I am sure the VSR is wired correctly and checked the voltage going in to the start battery at 13.7 when the engine is running. When I charge the start battery with my shore powered charger it takes a full charge and starts the engine well afterwards but after a few weeks it wont turn it over by itself and I have to use the bypass switch and put both batteries on line to start the boat.

Short of buying new batteries I have addressed every possibility and I still cant find out why this is happening. I have not replaced the batteries because I had them tested by a marine engineer and they are fine. - HELP!!!!!!

13.7 is too low. Where are you measuring this. Directly across the battery terminals ? or directly across the alternator output?

Have you tried simply connecting the alternator output to the starter battery alone, without the VSR. If so what volts do you see.

Have you checked the operation of the VSR. I believe the BEP one does not close until the volts reach 12.7 and opens when the volts fall below about 12.8. Possibly you are not reaching the point at which the VSR operates resulting in one battery being undercharged and the other not at all.

 

[Modulation]

I had a similar problem on my last boat and it turned out to be the alternator. Someone had blown it by turning off the engine with the key.
Anyway I had it serviced by a motor engineering firm (a tenth of the cost of a new one) and refitted it and all was well.
Could it be that your new alternator is not correctly wired in? It sounds as if it just isn't delivering any charge to your battery. And your battery sounds ok as it's holding charge from your shore power charger.

 

[pvb]

Could it be that your new alternator is not correctly wired in? It sounds as if it just isn't delivering any charge to your battery.

Did you notice the bit where the OP said "the voltage going in to the start battery at 13.7 when the engine is running"?

 

[Stemar]

I'd check the voltage coming out of the alternator (engine running) and compare it with that at the batteries. If the voltage at the alternator is only 13.7, there's the problem. If it's 14.something, but the batteries are only getting 13.7, clean all the connections and try again. No improvement, it's the VSR bank that's the problem.

The cheap solution is to pop into Maplin or your local motor factor and get a 12v 50amp relay, the cubic ones that cost less than a fiver. Wire the engine battery direct to the alternator, connect the domestic + to the engine + via the switched contacts on the relay and feed the switching coil from somewhere on the connection from the charge warning light to the field connection on the alternator. I've had this arrangement on Jissel for years; it ain't clever and it ain't pretty, it just gets on with the job of putting the domestic battery in the charging circuit when the alternator's doing its stuff and keeping the two apart when it isn't. PM me if you need a wiring diagram.

The purists will say that the starter battery is usually pretty well charged, so it'll get overcharged when the domestic's a bit low, or the domestic will draw from the starter. They may be right, but I replaced my starter battery last year after the best part of 10 years and it was second hand when I got it, so I wouldn't say it owed me a great deal.

If the relay bank is at fault, I reckon you'd be better off getting a cheap relay and investing the savings in a couple of solar panels and a controller.

 

[Stu Jackson]

What kind of alternator. IIRC, Hitachis have a built in temperature sensor in the regulator that cuts back output. An alternator saving design feature but not so great for charging.

The problem with all Yanmar/Hitachi alternators, except some very old models, is that they can lead to chronic under charging and extremely slow bulk & absorption charging. Why? These alternators have a built in thermal protection system that works by lowing the target voltage point as the alt heats up.

Most of the Yanmar/Hitachi alts begin temp compensation at 20C / 68F and drop the voltage by 0.01V for every degree above 68F. When you consider that most of these alts will run at 210-220F+ in bulk that means:

220F - 68F = 152 degree difference

152 X -.01 = -1.52V drop in the alternators max voltage output at 220F.

The specs will also say things like 14.4V (+/-0.3V) for the regulated voltage. Let's assume your reg was producing the spec of 14.4V and your alt is now running at 200F.

That is a 132 degree rise above 68F so 132 X -.01V = -1.32V

14.4V - 1.32V = 13.08V at the batteries

This is NOT INCLUDING ANY VOLTAGE DROP IN THE WIRING

Lowering the voltage point reduces accepted current by the battery bank and allows the alt to cool... It is a safety feature for the alternator but a death feature to your batteries...

 

[JumbleDuck]

I have trawled through the numerous threads on batteries/charging questions and cannot find a similar case to address my query. My starter battery seems to slowly lose its ability to turn over the 1GM10 after a few weeks and a half a dozen uses.

Have you an idea whether it's number of starts or length of time which matters. If the battery can't cope with more than half a dozen starts, and assuming that the engine isn't asking for an inordinate amount of cranking (my 1GM10 needs about 5s from cold and 2s when warm) it suggests that the battery is knackered. A 1GM10 starter is nominally 1kW, which is 80A, so it takes 45s of cranking to take a single Amp-hour out of the battery.

If your battery is good then it's clearly not charging when the engine is running and it's discharging in the meantime. Have you tried disconnecting it completely when you're away from the boat?

 

[dslittle]

Most of the Yanmar/Hitachi alts begin temp compensation at 20C / 68F and drop the voltage by 0.01V for every degree above 68F.

Slight thread drift but relevant. I have noticed that the volts going into my batteries have recently dropped by 0.2 volts i.e. 14v instead of 14.2v initially and then 13.5v instead of 13.7v on float. The ambient temperature has risen recently (and long may it last). The charging regime is exactly the same as it was previously. Is the temp the reason?
Cristec Charger on shorepower not alternator.

 

[Stu Jackson]

Slight thread drift but relevant. I have noticed that the volts going into my batteries have recently dropped by 0.2 volts i.e. 14v instead of 14.2v initially and then 13.5v instead of 13.7v on float. The ambient temperature has risen recently (and long may it last). The charging regime is exactly the same as it was previously. Is the temp the reason?
Cristec Charger on shorepower not alternator.

Do you have temperature compensation on your charger?

 

[dslittle]

Do you have temperature compensation on your charger?

That is my perplexing bit because I don't think it has and I have never noticed these voltage drops before over the last five years...

 

[Stemar]

If it's hard-wired, the first thing I'd do is look for voltage drop along the wiring, cleaning contacts where I find it.

 

[ffiill]

My modest alternator split charging delivers almost 15 volts through the two charging circuits voltmeters.
Similarly my trickle charging solar panel delivers a similar voltage to my starter battery.

 

[RichardS]

I had a similar problem on my last boat and it turned out to be the alternator. Someone had blown it by turning off the engine with the key.

I don't think that does any harm. I believe that it is disconnecting the battery by turning off the "1 - 2 - Both - Off" switch whilst the engine is running that damages the regulator.

Richard

 

[VicS]

I don't think that does any harm. I believe that it is disconnecting the battery by turning off the "1 - 2 - Both - Off" switch whilst the engine is running that damages the regulator.

Richard

Thats right. Turning off the key switch does not disconnect the alternator from the battery. Its turning off the isolator while the engine is running that causes the problem.

Imagine all the electrons speeding along the wire. If the isolator is suddenly opened they have nowhere to go. Big pile up of electrons causes a voltage surge which blows the diodes.

Like when a lorry jack-knifes on the motorway. All the BMWs speeding along at 100mph + suddenly have nowhere to go. Big pile up of BMWs.

Turning off the key switch is like putting a speed limit up on the matrix signs ...... has feck-all effect

 

[VicMallows]

Slight thread drift but relevant. I have noticed that the volts going into my batteries have recently dropped by 0.2 volts i.e. 14v instead of 14.2v initially and then 13.5v instead of 13.7v on float. The ambient temperature has risen recently (and long may it last). The charging regime is exactly the same as it was previously. Is the temp the reason?

How confident are you in the accuracy of your voltmeter with temperature change??

 

[halcyon]

I have trawled through the numerous threads on batteries/charging questions and cannot find a similar case to address my query. My starter battery seems to slowly lose its ability to turn over the 1GM10 after a few weeks and a half a dozen uses.

I have a small cruiser (sail) and have a house and starter battery system controlled by a BEP VSR cluster.

The alternator should normally be wired direct to engine battery via starter cable, so VSR should not effect engine battery charge, so first job is to check for volt drops.

Get a 5 meter length of 1 / 1,5 sq mm cable, strip back one say 50 mm, twist tight around multimeter neg probe, tape to help hold in place, strip back other end, undo neg battery terminal and push cable beside terminal lug refit terminal and clamp. You now have a fixed negative to measure anywhere on the boat, volt drop in positive cable will show up as increasing voltage, volt drop in negative cables will also show up as a increase above base zero.

Now with engine running work out from engine battery towards the alternator, checking voltage on any connections, any increase will be current check point or between there and previous check.

It will also be useful if you can check charge amps to engine battery.

Sounds a bit like low charging resulting in surface charge and little charge amp hour capacity.

Brian