Confusing battery charge problem need input.

[guyrj33]

1. Charging batteries in parallel is fine.
2. The voltage from the AC charger is low, something is amiss there.
3. Measure the voltage on each battery separately, with the 1,2,both switch set to OFF.
4. Charge each battery separately with the shore charger and record the voltage at the start and at the end.
5. I think you may find that one of the batteries is bad and is dragging the other battery down.
6. Dual use batteries aren't the best option, but with the usage pattern you describe they should be OK for now.
7. you don't need a 40 amp charger, 10 amps is fine, just make sure it's working by measuring the output voltage with each battery being charged separately. You may find the charger isn't wired correctly and is only charging one battery.

[witzgall]

Things to check/consider:
1. Corroded cables, lugs, shorted or damaged cables, etc
2. If one of the batteries was damaged and had a bad cell, it will quickly draw down and damage the other if left in parallel.
3. Check the battery switch carefully for damage or corrosion.
4. Consider adding a battery monitor, Voltage is a lousy indicator of state of charge in most applications. A monitor acts like a fuel gauge.
5. Consider seperating the batts as others have said. Use a product like the Balmar Digital Duo Charge to charge you start batt, send ALL charging sources to your house bank.

Disclosure - I work for Balmar.

Chris

[senormechanico]

guyrj33 and witzgall nailed it.

[a64pilot]

Cmon guys, they don’t need to spend money on battery monitors etc, they don’t even need a shorepower charger, although having one is prudent.
They only day sail the boat and nothing at all is on, except the bilge pump of course.
They should be able to use it like a car, with engine alternator providing what little charging is necessary.

Really only two likely scenarios,
a. Batteries are toast.
b. Something is drawing on the system, there is current being pulled by something, draining the batteries.

I just hope it’s not stray voltage, but I think a Pro needs to take a look, cause it might just be, before they go buying battery monitors etc. cause they have no need for one, anymore than you do in your car.


On edit cause he asked what the voltages should be, an automobile runs 14 V plus or minus .2 forever, so his alternator voltage is a little high, but not enough to worry about.
His 13.55 V on his shorepower is just about right for float voltage in my opinion, again, nothing to worry about.

[Dougtiff]

Firstly, there is nothing wrong with W.M. battery's, my AGM's are 5 year's old and fine, also the 10 A. charger is enough output for 85 amp hours of battery, charging source goes to the house bank, and a combiner is installed between the house and start,you can also install a bypass switch between the house and start, in case the combiner fails the house and start can be different type, example, my house bank is AGM and start is wet cell, why ?, because the start [wet cell] is easy to get to, to check water level, but the house [AGM] are hard to get to, other wise i would have all wet cell's.

[ramblinrod]

Originally Posted by er9

My friend has a Xantrex 10A 'TrueCharge' battery charger charging two 6 month old West Marine 'Dual Use' batteries (85 Amp Hour). We have her selector switch set to both (the batteries are not in parallel) so we are using both batteries simultaneously for starting power and they are being charged simultaneously from the charger.

One of the batteries has recently died completely and the other is in really bad shape. We have had to use an emergency jump start battery pack to get the boat started.

I'm trying to figure out what killed the batteries so quickly? The only thing that draws power from them is when we start the boat and the bilge pump (which is only cycling once every couple days, if that). There is no other power draw, ever.

When i put a multimeter across the terminals when the charger is running i get 13.55 volts. When i put meters across terminals when alternator is charging its 14.5ish volts

Is the Xantrex chronically undercharging and killing the batteries? I'm not sure what the correct output voltage should be.

When we motor out, which is 30-45 minutes of motoring, the battery is still not receiving sufficient charge from the alternator to start the boat again after we are done sailing. this tells me maybe the battery ability to store power has been severely degraded.

My gut feeling is the charger isn't doing its job either because were asking it to do too much by trying to charge both batteries at the same time or its faulty.

Any insight/second opinions?

2 x Dual Purpose Grp 24 Batteries, which may be paralleled for charging or isolated for loading is absolutely fine and a standard configuration.

My suspicion is that the 1/2/Both/Off Switch has not been used correctly and the batteries have been badly discharged and perhaps ruined.

It is important to keep batteries as fully charged as possible and not let them get below 50% charge. Letting them get right down to 0% charge (11 Vdc) several times will kill them, (they will no longer be able to accept a charge anywhere near their rated capacity).

1. Google "Lead Acid Battery Safe Handling" and follow instructions when handling batteries (they can be dangerous causing fire or personal injury if mishandled).
2. Verify the batteries are topped up to the proper level with distilled water (assuming they are not a maintenance free (VRLA) variety.
3. Carefully remove, clean, and replace each battery terminal / connector. (One at a time.)
4. Verify the battery charger and alternator are connected properly (according to manufacturers instructions).
5. With no charger on and no loads operating, record the voltage at each battery in each of the 1/2/B/Off switch positions.
6. Turn the shore power charger on, record the voltage at each battery in each of the 1/2/B/Off switch positions.
7. Put the battery switch in the B position, and leave for 24 hours.
8. Batteries should be fully charged, record the voltage at each battery in each of the 1/2/B/Off switch positions.
9. With the battery switch in the 1 position, turn on all the lights for 2 hours and record the battery voltages.
10. With the battery switch in the 2 position, turn on all the lights for 2 hours and record the battery voltages.

Report your findings.

I should be able to tell you if your batteries, battery switch, and shore power charger are connected and working properly.

[ramblinrod]

Originally Posted by parkstone bay

Part of the problem is, I suspect, we have 2 starter batteries in the system. You need to have one starter battery, and one leisure battery. RVs (Camper Vans in Britspeak) have similar problems to yachts. You want to have a dedicated starter battery, which CANNOT be run down by domestics use (TV, nav instruments, fridge, etc), and, entirely separately electrically, a domestics battery, which, when it does run down, CANNOT draw current from the starter battery. This way, you've always got power to start the donk. Talk to your local RV specialist, and he will recommend either a split charge diode system or a Voltage Sensitive relay. Both systems enusres that the starter is charged preferentially to the domestics. You need to get rid of the idea that linking 2 batteries to start is a good call - it ain't. One dedicated starter battery (85 AH should crank a 30HP diesel), and a SEPARATE leisure battery (perhaps 125 AH, even on a small boat), plus either the split-diode, or VSR. Using an outside charger, you should charge each battery separately, not together.

I disagree with most of this post if I understand it correctly.

2 x Dual Purpose Batteries, an alternator, a 10 A single bank charger and a 1/2/B/Off switch is a valid system that has been used by many boaters for many years.

Like anything, it must be installed correctly and used correctly to function properly.

It is true there are alternatives to a 1/2/B/Off switch that have pros and cons, but that does not make the former solution "invalid" or "untenable".

Used properly, it should not be necessary to parallel (switch B position) both fully charged batteries to start the small auxiliary diesel.

It is correct than in such a system, normally one battery would be designated the "start battery" and isolated from loads when no charger is operating, and the other battery would be designated the "house" battery and the only battery connected to loads when no charger is operating.

It may be necessary and is valid to parallel (B switch position) severely discharged batteries to start an engine.

My suspicion is that something is wired incorrectly or the 1/2B/Off switch isn't being used correctly.

Not to confuse the issue further, but since the two banks are effectively identical (when healthy), though not ideal in many ways, they have the advantage that one can alter the designation occasionally, to equalize the deep cycle use between the two banks.

[er9]

thanks for all the great replies so far. looks like i have some homework to do saturday when i can get back to the boat.

[er9]

Originally Posted by a64pilot

Cmon guys, they don’t need to spend money on battery monitors etc, they don’t even need a shorepower charger, although having one is prudent.
They only day sail the boat and nothing at all is on, except the bilge pump of course.
They should be able to use it like a car, with engine alternator providing what little charging is necessary.

Really only two likely scenarios,
a. Batteries are toast.
b. Something is drawing on the system, there is current being pulled by something, draining the batteries.

I just hope it’s not stray voltage, but I think a Pro needs to take a look, cause it might just be, before they go buying battery monitors etc. cause they have no need for one, anymore than you do in your car.


On edit cause he asked what the voltages should be, an automobile runs 14 V plus or minus .2 forever, so his alternator voltage is a little high, but not enough to worry about.
His 13.55 V on his shorepower is just about right for float voltage in my opinion, again, nothing to worry about.

when we first started having problems it seemed to me peripherally that something was drawing power from the batteries. at first it seemed like they were being discharged very quickly when no one was around. i actually spent the better part of a day searching for some power draw and was prepared to sleep on the boat a night or two to see if the bilge was cycling excessively. i was convinced something was sucking stray power. i couldn't find anything obvious so i brushed it off at the end assuming it was a bad battery or charger but that was my first impression.

i think we need a pro to come and verify things as this level of electrical is still a bit beyond my skill level and its not my boat.

[ramblinrod]

Originally Posted by er9

when we first started having problems it seemed to me peripherally that something was drawing power from the batteries. at first it seemed like they were being discharged very quickly when no one was around. i actually spent the better part of a day searching for some power draw and was prepared to sleep on the boat a night or two to see if the bilge was cycling excessively. i was convinced something was sucking stray power. i couldn't find anything obvious so i brushed it off at the end assuming it was a bad battery or charger but that was my first impression.

i think we need a pro to come and verify things as this level of electrical is still a bit beyond my skill level and its not my boat.

If you think there are loads on when the battery switch is off you can test for that with an ammeter. If you have a DC current panel meter, just check the reading when everything should be off.

Assuming all loads are connected through it, perhaps not sooooo….

If you have a DC clamp-on ammeter it is relatively easy, just clamp it on over the battery plus cable. If it reads something when everything should be off, start disconnecting loads until it drops to zero.

If no DC clamp-on, you could disconnect the battery terminal and connect an in-line DC ammeter. Beware many have a limit of 10 A or an internal meter (easily replaceable) fuse will be blown.


Another option is to go around with a voltmeter and measure across suspected loads for voltage. If 12 Vdc is across it, when it should be off, it is powered.

Some loads are connected to an "always on" circuit, so that when the battery switch is "off" they can be operated.

These may include:

1. Bilge pumps
2. VHF Radio
3. Safety sensors (propane sniffer, CO, etc.)
4. AM/FM radio memory.

One that is not always on, but used to get me on my boat, was the engine compartment lights.

(Our battery switch is always on "B" (both), to combine the split house bank, except for test / service purposes.)


Note that a typical bilge pump draws around 5 A (varies with size). Even if it was on for 15 seconds every hour, this would only draw 0.5 A-hrs per day. On a 85 A-hr usable bank, from fully charged you should be at 50% SOC (12.2 Vdc) after 170 days, if no other load is on.

(If the bilge pump is on more that 15 seconds every hour, fix the leak(s), the boat is trying to sink.

[er9]

Originally Posted by ramblinrod

1. Google "Lead Acid Battery Safe Handling" and follow instructions when handling batteries (they can be dangerous causing fire or personal injury if mishandled).
2. Verify the batteries are topped up to the proper level with distilled water (assuming they are not a maintenance free (VRLA) variety.
3. Carefully remove, clean, and replace each battery terminal / connector. (One at a time.)
4. Verify the battery charger and alternator are connected properly (according to manufacturers instructions).
5. With no charger on and no loads operating, record the voltage at each battery in each of the 1/2/B/Off switch positions.
6. Turn the shore power charger on, record the voltage at each battery in each of the 1/2/B/Off switch positions.
7. Put the battery switch in the B position, and leave for 24 hours.
8. Batteries should be fully charged, record the voltage at each battery in each of the 1/2/B/Off switch positions.
9. With the battery switch in the 1 position, turn on all the lights for 2 hours and record the battery voltages.
10. With the battery switch in the 2 position, turn on all the lights for 2 hours and record the battery voltages.

Report your findings.

I should be able to tell you if your batteries, battery switch, and shore power charger are connected and working properly.

I was only able to get to the boat for about an hour on sunday unfortunately so was not able to do all the suggested tests but did do some and have a little more information to share.

Just to refresh the info...the last time we used the boat (sunday july 29th) we could not start the boat. we tried it with the switch in the 'both' position, the #2 position and the #1. in the 'both' and #1 position the engine would barely turn over and would not start. In the #2 position it appeared the battery was completely dead as there was no power at all when i turned on the ignition key. when we left the boat it seemed #1 battery might be salvageable so i left the battery switch in the #1 position for the week.

I did some testing this sunday 5th with a multi tester. I did not have enough time to remove the batteries and check the fluid levels or to verify if the charger wiring was correct. the wiring to the battery terminals seemed ok though. I only had enough time to do tests #5 & #6 as you outlined above...here are the results....

#5 Test (no charger, no loads):

Switch Position / #1 Battery #2 Battery
OFF - 13.6v - 13.6v
#1 - 13.59 - 13.59
#2 - 13.57 - 13.57
BOTH - 13.58 - 13.58

#6 Test (Shore power/ charger on)

OFF - 13.8v - 13.8v
#1 - 14.09v - 14.07v
#2 - 14.29v - 14.28v
BOTH - 14.19v - 14.14v

I then tried starting the engine with the battery switch set to #1 position, Engine started right up. Engine swith in 'BOTH' position, engine started but slightly harder. With switch in #2 position, no power at all as if battery was 100% dead.


I then turned on engine and ran it for a few minutes with the selector switch in the #1 position and tested each battery with engine running. #1 battery was reading 13.3v and #2 battery was reading 13.3v as well.

I turned off engine and re started it with selector switch in "BOTH" position, charger not on only alternator charging and readings were 13.45v on #1 battery and 13.3v on #2 battery.

I could not start engine on #2 position so could not test.

i turned off engine and turned on all the lights i could. with switch in #1 position they all worked. with swith in 'both' position they also worked. with switch in #2 position everything went dead.

My interpretation with my current level of experience suggests the charger is probably working fine and both batteries are good. The alternator is toast due to bad alternator or wiring issue. The selector switch is possibly bad and/or there is a wiring problem. The wiring on the boat is atrocious so im planning to bring in a pro to quote rewiring the battery/charging circuit. curious if anyone else has a differing opinion based on limited results?

[Bdozz]

This may be a dumb question, but cant you just take your batteries to a car parts store and have them tested? I am a professional mechanic, not really familiar with boat systems, your alternator should put out about 14.3 vdc when working properly. I would have both batteries tested before hiring someone to come check your electrical system, they are going to do that first anyway.

[ramblinrod]

Responses in bold blue.

Originally Posted by er9

I was only able to get to the boat for about an hour on sunday unfortunately so was not able to do all the suggested tests but did do some and have a little more information to share.

Just to refresh the info...the last time we used the boat (sunday july 29th) we could not start the boat. we tried it with the switch in the 'both' position, the #2 position and the #1. in the 'both' and #1 position the engine would barely turn over and would not start. In the #2 position it appeared the battery was completely dead as there was no power at all when i turned on the ignition key. when we left the boat it seemed #1 battery might be salvageable so i left the battery switch in the #1 position for the week.

I did some testing this sunday 5th with a multi tester. I did not have enough time to remove the batteries and check the fluid levels or to verify if the charger wiring was correct. the wiring to the battery terminals seemed ok though. I only had enough time to do tests #5 & #6 as you outlined above...here are the results....

#5 Test (no charger, no loads):

Switch Position / #1 Battery #2 Battery
OFF - 13.6v - 13.6v
#1 - 13.59 - 13.59
#2 - 13.57 - 13.57
BOTH - 13.58 - 13.58


This indicates the charger is working. You are seeing the charge voltage on the batteries. 100% charged batteries with no residual charge voltage will read <12.8 Vdc. Charger likely OK.

#6 Test (Shore power/ charger on)

OFF - 13.8v - 13.8v
#1 - 14.09v - 14.07v
#2 - 14.29v - 14.28v
BOTH - 14.19v - 14.14v

This indicates the charger is working and goes into absorption mode when first turned on. Charger OK.


I then tried starting the engine with the battery switch set to #1 position, Engine started right up.

This indicates battery 1 is accepting a charge.


Engine swith in 'BOTH' position, engine started but slightly harder.

This indicates Battery 2 is not as healthy, and is draining energy from battery 1.

With switch in #2 position, no power at all as if battery was 100% dead.

This indicates battery 2 has very very little capacity to retain a charge. It reads high immediately after the charge voltage is removed, but as soon as a load is applied, what little charge it had is gone.

Battery 2 is most likely boiled dry. Remove the caps, (assuming non VRLA) top up the fluid level with de-ionized water. Put it back on the charger in the BOTH position for 24 hours. If it still won't start the engine, it is ruined and must be replaced.


I then turned on engine and ran it for a few minutes with the selector switch in the #1 position and tested each battery with engine running. #1 battery was reading 13.3v and #2 battery was reading 13.3v as well.

I turned off engine and re started it with selector switch in "BOTH" position, charger not on only alternator charging and readings were 13.45v on #1 battery and 13.3v on #2 battery.

I could not start engine on #2 position so could not test.

i turned off engine and turned on all the lights i could. with switch in #1 position they all worked. with swith in 'both' position they also worked. with switch in #2 position everything went dead.

This confirms battery 2 is not holding a charge.

My interpretation with my current level of experience suggests the charger is probably working fine and both batteries are good. The alternator is toast due to bad alternator or wiring issue. The selector switch is possibly bad and/or there is a wiring problem. The wiring on the boat is atrocious so im planning to bring in a pro to quote rewiring the battery/charging circuit. curious if anyone else has a differing opinion based on limited results?

I think Battery 2 is the culprit. If all connections are clean and tight, it has likely boiled dry. Top it up with de-ionized water, put it on the charger in "Both position" for at least 24 hours, and see if you can operate lights and start the engine on Battery 2.

If not replace battery 2.

I will reserve judgement on the alternator, until battery 2 is replaced.

It could be that battery 2 is drawing so much current, the alternator can't deliver more than 13.X volts. If you replace battery 2, and fully charge both batteries with the shore power charger, after starting the engine, the alternator should slowly increase the battery voltage from about 13.3 to 14.2 Vdc as it tops the batteries back up.

[er9]

Hey Rod, thank you for taking the time. i really appreciate it and all the insight everyone else has provided. great learning experience. i will pull #2 battery next weekend (actually both) and check the fluid levels and do as you suggested. Interesting info about the alternator...i would not have figured that out. will let you know how it goes.