Change both Batteries or only One?

[James V]

One of my batteries died after 2+ years. The other is just as old and is the stock battery.

Should I wait until the stock batteries no longer takes a charge?

Change both at the same time?

I am not using both at the same time.

Thanks, James


ModsNote:
Moved to Modifications ~fc

[Hamin' X]

It is always best to have batteries that are of similar capacity and condition, unless they are always kept separate in both use and charging. The danger is in the charging. If you charge with the batteries in parallel, the bad battery will be "telling" the regulator that it needs more charge, even though the newer battery is at full charge. This results in over charging the newer battery, leading to it's early demise.

~Rich

[Trouts Dream]

I use a combiner which keeps the batteries seperate buy will charge both batteries at the same time.

[Hamin' X]

I use a combiner which keeps the batteries seperate buy will charge both batteries at the same time.

All the more reason to have batteries in similar condition, because the combiner does not know which battery to charge. There are sequence chargers that will work better, but the danger here is the bad battery taking too much of the charging time and not letting the good one reach full charge.

~Rich

[John Christian]

James , the answer depends on your set up. Mine for example, utilizes a combiner with house hooked to charger and motor hooked to alt. When combined either source charges both. If the house battery was low, ( a setting you can control) the shore power would only charge the house battery, until it reached the threshold and then the combiner would combine both banks and charge the start battery as well. I guess if it were me, I'd replace one and make sure that was the start battery. Will require some additional monitoring but I'd rather delay shelling out $200 on another battery as long as possible.

Does your combiner have an auto relay to protect overcharge???? Probably it does, and you may very well be able to set that limit yourself.

I agree 2 batteries of similar make and condition are always preferable, but somewhere cost has to factor into all our decisions.

[pokerrick1]

Go for it! Batteries are cheap at Wal Mart

Rick

[James V]

Thanks for the data. The salesman at West Marine could not explain but I thought I was right. I normally use only 1 battery all the time. As long as I do not use A + B combination I should be OK. This is what I thought.

Series 24 deep cycle marine at West is $ 116 here in Maryland. No WalMart around.

[Dimitri-2000X-Tampa]

I went with Walmart batteries last time around, I think I got 2 batteries (one group 24 and one group 27) for the price of one WM group 27 but now they are only 1.5 yrs old and already showing some signs of premature demise. Guess you get what you pay for because I think my last WM battery lasted about 4 years and the 2 marine diehards I had in my old keel boat (which are probably twice the price of WM batteries) lasted a whopping 6 years.

If both batteries are within a similar generally fair or poor condition, I would replace both but in some cases, if one battery is totally worthless and the other one is performing pretty well, then I would only replace the worthless one.

[Frank C]

I have two of Walmart's massive Group 29 Marine Deep Cycles, 115 Ah each, $65 each.

Walmart's batteries have the longest life cycle of all major brands now in this market.
( so says Consumers Reports )

Edited for emphasis ... no link available.

[Dimitri-2000X-Tampa]

I think your link needs fixing. Where do you put those batteries at? I have mine in the stock 26X location but wouldn't mind having more amp hours (especially for long hours sailing with the A/P and 160W stereo). Problem is that the pressure water system, galley and coolers take up most of the other usual real estate and I don't want to remove any flotation from under the v-berth either.

[Frank C]

I think your link needs fixing. Where do you put those batteries at? . . .

It wasn't a link, since Consumer Reports is subscription-only. If you're a subscriber, it's a 2008 report.

I fit both of them into Roger's battery locker, the 26X's aft galley seat.
It simply required expanding the hatch opening by a half-inch, or so, with his original hatch cover still on-duty.
Look in your local Wally's. These are the biggest Marine batts they carry (called MAXX-somethin, Gp 29).
I no longer have starter vs. house batteries. I prefer the ODD-EVEN approach to batt-mgmt.
It was discussed during your absense ... search for that phrase.

[DaveB]

I bought 2 Wallmart group 31 marine 125 ah for $72 ea. in Feb.for my house batteries and lasts me over a week with battery above 12 volts. This does all my House needs running, sterio 200 watts, 9 inch HDV TV with CD built in,lights,depth guage,running lights, 2 fans, TV I run on a 75 watt converter, charge cell phone's and other AAA batteries includeing handheld VHF.
Just spent 4 days on boat and after trip Batteries were 12.34 volts.
I have a start up battery for engine and is isolated from House batteries, chargeing system is 10 amps and charges all batteries independent. My 2 house are in series.
Can't beat the wally batteries but be sure to bring in old core or you will pay $9 each.
Dave

I have two of Walmart's massive Group 29 Marine Deep Cycles, 115 Ah each, $65 each.

Walmart's batteries have the longest life cycle of all major brands now in this market.
( so says Consumers Reports )

Edited for emphasis ... no link available.

[John Christian]

Frank, I work in the Domestic Automotive business, I havn't looked at a consumer report for 30 years, can I assume their claims were based on wet cell batteries only?

JC

[Frank C]

Yes, in the Wet-cell segment of their report, Walmart batteries were either highest, or second-highest ranked, and also won "best value." You can sign-up on their website for about 20 bucks a year, and then access the current year of reports. Alternatively, check out this year's issues in any library.

[James V]

Thanks for everything. The M's battery storage cannot fit 2 series 29's in it. The orginal battery is a series 24 and that is what I bought. I was thinking to replace the other series 24 with 2 series 29's deep cycle. I think that I can put in the battery compartment 1 -24 and 1 29 and then another 29 in the storage compartment. I have a 3 way battery switch.

Anybody done this on an M?

Is there a "Born date" on a battery? I understand that if a battery has be sitting to long it will not preform as well.