Engine batterie dying too quickly

[GILow]

Originally Posted by kriskro

Following the recharge of the batterie at home, I went to test it again at super cheap and it came out that it was still good. So it was just flat



I went back on the boat, put it back and did a bit more testing.



With the battery full, I started the engine and measured, at 2200 rpm, 13.90v and 0.80 amps... I was actually surprised to see such small current.



My understanding is that alternators gives as much current as the load/ Demand. So the battery being full, this may be normal ?

I thought it was clear. There is a problem with parasitic discharge. The current you were losing with the system off was more than enough to kill the battery and could easily explain your problems with starting and engine battery life.

Have you fixed that problem yet?

[kriskro]

yes, there are basically 2 things that were consuming power, the wattmeter and the bilge pump.

When I leave the boat, I usually turn the switch house battery. I must have made the mistake of leaving the switch to start battery and this just sucked all the power out of the start... easy mistake when you just arrive to dock and you think only about the cold beer
And thinking about it, i should leave the switch to disconnect so that both battery are isolated. (Only the bilge and solar going to the house house bank directly)

Now, when disconnecting both batteries, there is no amps at all showing on the start battery.

I like the idea of the system where you can run the engine to load both batteries without changing where you consume the power from. At the moment, if I want to charge both batteries with the engine, then I have the load on both batteries... And I may well consume more power that the alternator is giving with the fridge and other appliances on board.

I may put something like below to make it simpler. With no connections between the start circuit and the house circuit and just the relay to charge start battery first and house battery second.

https://www.amazon.com.au/Square-Bat...98008768&psc=1

[GILow]

Ok, great to hear you’ve solved it.

I think it would be well worth starting a new thread describing your setup and asking for suggestions.

I’ll be no help at all because my charging setup is very weird and most people think I am crazy doing it the way I do. [emoji846]

[lituya1617]

Do the basics with the starting battery: 1. Install a permanent volt meter where you can see it during engine operation. 2. Install an ampere meter where you can see it. 3. Disconnect the positive engine battery terminal while the main switch is OFF (battery isolated from loads) and hook your multimeter up to the positive terminal and the positive battery terminal reading DC voltage. There should be no voltage reading. If there is, you have a short circuit draining your battery. Find and correct. 4. Fully charge the battery. Do a high-rate discharge test on your battery. 5. With the engine running at max idle speed and the battery connected watch the volt meter to test your alternator. The voltage should start high, around 14.7 volts and fall quickly to 14.3 volts and then slowly drop toward 13.7 volts when the battery is fully charged. If this happens, your alternator works. Simultaneously look at the ampere meter and see that it reads about 60 amps when the engine is first started. A good alternator will put out it's rated amperage just after engine starting but the value will fall quickly to a trickle of electricity when the battery is full. 6. It takes several hours to recharge a battery. To kill a battery rapidly, just let it sit partially discharged. Always run a trickle charger on a battery. If your engine battery is 600 CCA and is at 50% charge, it will take an alternator putting out 60 amps max at least five hours to fully charge it (rough estimate). Last note: no battery in any of my boats has ever failed, even after ten years of use. If you take care of them and they are properly built, plain lead-acid batteries last a very long time. Educate yourself about how to care for a battery; it's more complex than people think.

[Wotname]

Originally Posted by lituya1617

Do the basics with the starting battery: 1. Install a permanent volt meter where you can see it during engine operation. 2. Install an ampere meter where you can see it. 3. Disconnect the positive engine battery terminal while the main switch is OFF (battery isolated from loads) and hook your multimeter up to the positive terminal and the positive battery terminal reading DC voltage. There should be no voltage reading. If there is, you have a short circuit draining your battery. Find and correct. 4. Fully charge the battery. Do a high-rate discharge test on your battery. 5. With the engine running at max idle speed and the battery connected watch the volt meter to test your alternator. The voltage should start high, around 14.7 volts and fall quickly to 14.3 volts and then slowly drop toward 13.7 volts when the battery is fully charged. If this happens, your alternator works. Simultaneously look at the ampere meter and see that it reads about 60 amps when the engine is first started. A good alternator will put out it's rated amperage just after engine starting but the value will fall quickly to a trickle of electricity when the battery is full. 6. It takes several hours to recharge a battery. To kill a battery rapidly, just let it sit partially discharged. Always run a trickle charger on a battery. If your engine battery is 600 CCA and is at 50% charge, it will take an alternator putting out 60 amps max at least five hours to fully charge it (rough estimate). Last note: no battery in any of my boats has ever failed, even after ten years of use. If you take care of them and they are properly built, plain lead-acid batteries last a very long time. Educate yourself about how to care for a battery; it's more complex than people think.

Yes, let's stick to the basics. While the general thrust of your post is good, some of the detail is misleading (IMO).

#5 - the voltage numbers you describe is very dependant on the type of voltage regulator (VR) fitted to the alternator. Many alternators have a simple VR that only regulates to a single voltage point. In these instances, the regulated voltage remains constant.

#6 - if you are referring to the start battery (as mentioned in the first sentence of your post), then it is simply wrong to say it takes hours to recharge a start battery. It only takes minutes. Let's do the maths - starter motor draws say 300A, it takes say 5 seconds to start the engine. That is 0.42 AH. To replace the 0.42AH will take (worst case) around 1AH. If the start battery was near 100% SOC before starting, that is around 1% of the battery capacity so battery acceptance charge current will be quite low. Let's say 5 amps (average). This means the start battery will be recharged in 12 minutes. This is predicated on worst case numbers. Certainly 30 minutes will be far in excess of what is needed in all normal situations.

Lastly, the CCA rating has no bearing on the time taken to recharge. The time taken to recharge is dependant of the AH rating and the SOC at time of recharging.

[GILow]

Originally Posted by Wotname

... Let's do the maths ...

Yes, PLEASE, let's do the maths. Up to now I was feeling a bit lonely in that approach.

[MVNightWatch]

Can't say that this IS the cause, but I have a friend who fought this exact same description of a gremlin for months. Turns out, the shore charger was keeping the starboard engine start battery topped off, but within 10 minutes after casting off, we'd lose that engine, cause the bad battery was really completely dead, and not sparking the gas engine plugs.It was being charged...just not able to hold it. Testing this is done with a battery load tester, available for loan from many auto stores. Something to check...good luck.

[GILow]

Originally Posted by MVNightWatch

Can't say that this IS the cause, but I have a friend who fought this exact same description of a gremlin for months. Turns out, the shore charger was keeping the starboard engine start battery topped off, but within 10 minutes after casting off, we'd lose that engine, cause the bad battery was really completely dead, and not sparking the gas engine plugs.It was being charged...just not able to hold it. Testing this is done with a battery load tester, available for loan from many auto stores. Something to check...good luck.

I think the OP has the problem sorted, but your friend’s experience reminds me of my boat when I bought it. The house bank seemed fine, but 24 hours away from the shore charger and it was completely dead.

One of a few painful lessons for me in boat ownership.