[westport4]

Looking for some advise on batteries. So just a brief history... We purchased this Z252 Shabah Feb 11th from a local dealer at the Lake of the Ozarks. Put it on the lift and had it winterized. Also connected up a trickle charger to both batteries and let it sit until two weeks ago (4/8). At that point we took off the trickle chargers, hooked up the cables to the batteries and off we went!

The boat went unused for two weeks and then we attempted to get out this past Sunday morning and the batteries were too low to turn over the engine. Gauge showed about 10v worth of charge.

Not sure the age of the batteries, so i plan to take them and have them tested out at O'Riley's or someplace and see if they are dying.

If i need new batteries, are there any gotchas I need to look out for? Any recommendations from the group? Current batteries are Fish Hunter brand with 575 CA and 450 CCA. That sounds low to me. My pontoon has a Diehard marine battery with 550 CCA.

Appreciate the advise!

[Firestone]

Just to verify you turned your battery selector to the off position?

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[GaryDoug]

You didn't say what engine you have.

From the Mercruiser service manuals,

If it's a 5.0L or 5.7L engine with a carburetor, the requirements are : 375 cca / 475 mca / 90 Ah
If it's a 5.0L or 5.7L with fuel injection the requirements are : 550 cca / 700 mca / 120 Ah
For a 7.4L or larger, it's : 650 cca / 825 mca / 150Ah

Are you using the batteries connected together all the time or through a switch? It would be unusual to have both main and backup battery low at the same time. How do you manage charging both? With a dual charger or one-at-a-time via a switch?

[westport4]

Mercruiser 7.4L engine. So per those specs, the batteries in it now are appear to be under powered.

They are run through the selector and what I was doing was setting that to off. Then i connected a Schumacher XM1-5 Maintainer, 1.5-Amp trickle charger to each battery.

I thought it was odd that both were low charge. I checked over all switches in the event I'd left something on.

Going to be rainy this weekend so it'll give me a good opportunity to take those batteries for testing.

[GaryDoug]

That charger has problems according to all the reviews I have read. It is too low a capacity to do much of anything but maintain a fully charged battery. Better to get a dual charger of at least 5 amps capacity. How are you managing the connections to the engine? Do you alternate them every time the boat is used? Generally you leave one connected for the day, and the next time you switch to the other one. That way they both get charged by the alternator.

[westport4]

Well being new to this type of boat, I was told to switch the selector to "all" when in use. Put it on 1 or 2 if coving out with radio on and such to avoid draining both batteries. Then switch back to all. Was that bad advise?


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[GaryDoug]

You may get a lot of opinions on this, but most agree that unless you have an ACR (automatic charging relay), you should use only one battery at a time unless you are needing a boost to get the engine started because the stronger/larger of the two batteries will limit the charging of the weaker/smaller one. Some folks use battery 1 on the way out and battery 2 on the way back. Or alternate them for trip1 and trip2 ... etc. Others, like me, use battery 1 all the time and keep them both on charge at the dock with a dual charger or two chargers. I have to occasionally switch to Battery 2 to check the cranking ability. If you can remember to switch them over, then you can get by with a single charger. Some folks use 3 batteries and use the 3rd one for accessory use only, like running the radio while anchored.
If you search around the forums and articles, you will get a lot of good advice. Keep in mind that some sites are trying to sell you battery hardware and chargers.

p.s. I do not recommend battery isolators due to their inherent inefficiency and power waste.

[westport4]

Okay well both batteries tested out as good after being on the trickle chargers all week. One tested out with 799 MCA and the other at 815 and both had 12+ volts in them. I must have left something on that drained the batteries in the two weeks it was left sitting. I didn't have time Sunday to put them back in the boat so I'll have to put them back in this coming weekend and see what happens.