Battery problem

[PhilR]

I have four 1 year old Group 34 AGM batteries and the engine battery won't take a charge. The boat is in a heated garage, on shore power with the battery charger operating... all engine switches are on except the parallel switch. The tester reads around 7 volts on the battery. Any ideas on what the problem may be other than a bad battery?

Phil

 

[stwendl]

At 7v you probably have one or two dead cells. The acr in your system may want to charge that battery as well and eventually the other batteries may go bad too unless acr cuts out before as they should

 

[knotflying]

Sounds like a bad battery. The relays should not allow a charge to that battery if it is that low so your other batteries should be safe. That is the problem with sealed batteries there is no way of testing cells. If it is only a year old is there a warranty? You also need to make sure that the charger is working properly and is set properly to ensure that it was not the cause of the battery failure.

 

[PhilR]

Thanks for the input. I talked with Marc at Wefings....he suggested turning on the battery charger with all electric switches on, including the parallel switch. He thinks the battery got drawn down by incidental demands and won't take a charge when it is that low. He thinks the parallel switch may enable it. I'll check it tomorrow. Also, correction....the battery is 2 years old not 1 as I previously indicated. Time sure flies at my age.

Phil

 

[SGIDAVE]

I have four 1 year old Group 34 AGM batteries and the engine battery won't take a charge. The boat is in a heated garage, on shore power with the battery charger operating... all engine switches are on except the parallel switch. The tester reads around 7 volts on the battery. Any ideas on what the problem may be other than a bad battery?

Phil

Hello Phil,

You say your boat has FOUR batteries. Is this the starting or thruster battery? You need to know HOW they are charged...that is, you probably have a THREE bank AC-powered charger, so at least THREE of those batteries should have a DIRECT charge coming from your shore-powered charger. How the 4th battery is supposed to get a charge current is your wild card and you will soon find out which battery it is...but for now you need to

a) get out your "tester" or VOM (volt ohm meter) and determine WHERE/WHICH batteries the leads from the battery charger go.

b) once found, you will see that the charger leads will have an inline fuse within a few inches of the battery - verify the fuses are good. You must know the location of those fuses and have spares aboard. Ascertain how the "4th" battery is supposed to get charge current whilst on shore power.

c) You probably DO HAVE A BAD BATTERY. But why? Your two year old battery certainly could have simply failed. But other likely scenarios could be that it was left uncharged and got drawn down as Marc says (from "parasitic" loads). Which means the battery was FINE but got RUINED do to lack of charge. So, you are back to checking the dead battery's means of receiving charge - either the inline fuse is blown or the Blue Seas ACR that was supposed to allow charge current to pass through one of your other batteries has crapped out.

Good luck with your investigations!

dave

 

[knotflying]

Sgidave,

I believe Phil's boat is wired differently. He has only one lead from the charger and the relays open and close to accept the charge to the battery needing it. Unfortunately if the charge gets too low in a particular battery the relay will not allow a charge to happen since it thinks there is a problem. Using the parallel switch will bypass the relays. Once the suspected bad battery is charged the parallel switch should be turned off and see if it holds the charge. If it does I would want to find out what caused the drain. If it is the engine battery it could be that the key was left in the on position.

 

[PhilR]

Hi Mike, I've had the charger on since this morning with the parallel switch on. Checked it this evening....all batteries showing full charge. I turned the parallel switch off and left the charger on. Hopefully the battery will show a full charge in the morning. I have kept the batteries connected thru the winter, and did leave the boat sit for over a month unplugged. Do you know what draws there may be on the engine battery? I do have a problem with the propane alarm going off frequently....don't know why. The propane tank is off. The key has not been in the ignition.

Phil

 

[Pilotnavigator]

It was said previously but should be repeated, to properly test a DC system you need a DC current clamp meter. It is the only way to monitor for current draw on a line. It is always current that you are interested in finding not voltage. A few minutes testing each line from the batteries forward to each load will tell you the actual current needs for each device. You should know this for the same reason you want to know your fuel burn. Treat the batteries as if they were tanks full of amps. You burn the amps in your devices and put amps back into the tanks with the alternator or the Chargers, either shore power or solar panels. One thing that helps is to connect the ground, yellow, and the positive, red, to opposite ends of the battery bank. Some will wire the negative and the positive from the same battery but this would cause the load to favour the first battery and wear or out first. The other way tends to draw them all down equally. Also be sure the alternator is connected to the house side. The arc will combine to the starter battery.

 

[stwendl]

I have four 1 year old Group 34 AGM batteries and the engine battery won't take a charge. The boat is in a heated garage, on shore power with the battery charger operating... all engine switches are on except the parallel switch. The tester reads around 7 volts on the battery. Any ideas on what the problem may be other than a bad battery?

Phil

Hello Phil,

You say your boat has FOUR batteries. Is this the starting or thruster battery? You need to know HOW they are charged...that is, you probably have a THREE bank AC-powered charger, so at least THREE of those batteries should have a DIRECT charge coming from your shore-powered charger. How the 4th battery is supposed to get a charge current is your wild card and you will soon find out which battery it is...but for now you need to

a) get out your "tester" or VOM (volt ohm meter) and determine WHERE/WHICH batteries the leads from the battery charger go.

b) once found, you will see that the charger leads will have an inline fuse within a few inches of the battery - verify the fuses are good. You must know the location of those fuses and have spares aboard. Ascertain how the "4th" battery is supposed to get charge current whilst on shore power.

c) You probably DO HAVE A BAD BATTERY. But why? Your two year old battery certainly could have simply failed. But other likely scenarios could be that it was left uncharged and got drawn down as Marc says (from "parasitic" loads). Which means the battery was FINE but got RUINED do to lack of charge. So, you are back to checking the dead battery's means of receiving charge - either the inline fuse is blown or the Blue Seas ACR that was supposed to allow charge current to pass through one of your other batteries has crapped out.

Good luck with your investigations!

dave

R27 have 4 batteries. Two of which are connected in parallel to increase capacity. Older r27 may have had a single charge source and use ACRs to let excess capacity flow into thruster and starter battery. Newer r27 have chargers with multiple outputs feeding each bank (one of which has 2 12v batteries in parallel as house battery). In either caseiof a battery is at 7v
That means most likely a cell or more is bad and the battery needs to be replaced. If you have flooded batteries check levels but lower fluid levels don't reduce the voltage, just the capacity. If you replace the battery try to replace it with the same type. As you can parallel batteries with the manual switches and the ACR all batteries should be the same type to avoid one battery trying to top of a another one with lower capacity or different behavior and causing it heat up.