Confusing battery charge problem need input.

[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?

[parkstone bay]

13.55 and 14.5 ish AMPS??? VOLTS surely? A guaranteed way of damaging two batteries beyond repair is to link them and charge them as one. It will probably also not do the charger any good. Disconnect both from their circuits - charge them separately. Reason: they will be different in terms of their charging requirements. The regulator circuit in the charger can manage one but not both.

[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.

[er9]

Thanks for the input...much appreciated. Sorry typo volts not amps.

in my inexperience I did not realize that you could not just charge both batteries simultaneously. I thought thats what the 'both' switch was for and that the chargers were built to handle both simultaneously.

So i'm assuming both batteries are beyond repair and need to be replaced?

I did isolate the #1 battery via selector switch and its currently being charged. Guess i will have to see what i get when im back at the boat saturday. what should the minimum volts across terminals be (when not charging) for a battery thats still in salvageable condition for use?

[john61ct]

Completely wrong, combining Start & House circuits while charging is routine.

Best automated with a VSR / ACR, but a 1-2-B switch is common.

At this point treat them separately, maybe on can be salvaged as a Starter.

Buy an ammeter, get a pro with good tools to check the wiring and teach you how to do that, measure Amps and Volts at the various key locations.

Buy a good new charger, 40A minimum.

Then we'll walk you through what you should see happening and get to an optimum setup.

[meridian28]

Just to be clear, you only start your engine and run a bilge pump with this setup? No other devices?

[meridian28]

Diesel or gas engine?

[meridian28]

Is the charger on full time at the dock?

[a64pilot]

I have had my battery switch set to both for years to no ill effect, it's irrelevant. 10 batteries or 1 it's still 12 V
You want deep cycle batteries, not starting batteries ideally although for you ruse it's irrelevant.
I strongly suspect the charger, just cause most anything Xantrex I have seen, is often broken.
However if you really don't know what your doing, do as John says and hire a Pro. In the end it will likely be less expensive

When you buy new batteries, don't buy WM batteries they are not quality batteries, yet are likely that the most expensive you can buy

[thomm225]

What is the battery voltage with the charger and alternator off? Check right on the posts

If the batteries are not in parallel, are they 6 volt batteries in series?

Make sure your connections are good and clean

And Btw like others have mentioned, I always charge my two 12 volt batteries that are in parallel simultaneously whether it be with solar or with a charger which is how I used to do it years ago

[er9]

Originally Posted by meridian28

Just to be clear, you only start your engine and run a bilge pump with this setup? No other devices?

occasionaly a chart plotter but we havn't been using it because of the issue we've been having. dont use nav or interior lights as we only sail this boat during the day. no refrig or other electronics.

[er9]

Originally Posted by meridian28

Diesel or gas engine?

Universal diesel, 3 cylinder. complete re-build two years ago. Ranger 28 sailboat. Internal wiring is a mess but hasn't given us any problems up until recently. i'm not exactly sure when the charger went in. i think it was a year ago, brand new. not sure who installed it. think he was a local recomendation.

[er9]

Originally Posted by meridian28

Is the charger on full time at the dock?

yes its plugged in and wired to the AC circuit which stays on all the time. newly re-wired and re-built docks and electric pedestals.

[er9]

Originally Posted by a64pilot

I have had my battery switch set to both for years to no ill effect, it's irrelevant. 10 batteries or 1 it's still 12 V
You want deep cycle batteries, not starting batteries ideally although for you ruse it's irrelevant.
I strongly suspect the charger, just cause most anything Xantrex I have seen, is often broken.
However if you really don't know what your doing, do as John says and hire a Pro. In the end it will likely be less expensive

When you buy new batteries, don't buy WM batteries they are not quality batteries, yet are likely that the most expensive you can buy

thanks i was thinking the same. i am going to try and talk her into buying decent batteries. i do have a couple of good referals for electricians. was hoping for something obvious. the batteries we have in boat that are dying were WM 'dual use'.

[er9]

Originally Posted by thomm225

What is the battery voltage with the charger and alternator off? Check right on the posts

If the batteries are not in parallel, are they 6 volt batteries in series?

Make sure your connections are good and clean

And Btw like others have mentioned, I always charge my two 12 volt batteries that are in parallel simultaneously whether it be with solar or with a charger which is how I used to do it years ago

i will have to check saturday. they are two individual 12v batteries. i will double check connections to batteries to make sure clean and are no dissimilar metal washers etc...