2018 G21 Battery type

[Az182]

Hi all,

I'm looking to replace the dual batteries in my 2018 G21, The current batteries go flat if I empty the ballast one time without the engine running, evening after a day riding to charge them up, this means I have to switch the batteries over to combine in order to start the boat. I thought the pumps would run off the accessory battery so you still have the starter battery to get you going?
The current batteries are standard car starting/cranking type, would deep cycle/marine/leisure batteries be better suited? Stereo is the standard system, I only use it sometimes when underway.

Does anyone else fill/ drain their ballast with the engine off?

Thanks

[charlesml3]

On a 2018? Those batteries should be nearly new. If they're going flat that fast then either they're defective or there is something else on the boat that's severely drawing them down.

I drain/fill with the engine off all the time. The pumps do not draw that much.

-Charles

[Az182]

Yep, 2018. That's interesting, do you know whether your batteries are deep cycle or normal car starter type?

Thanks

[Infinity]

You should be putting those batteries on a maintainer, keeps them in top shape. Also, check the water levels in them, could be a partial reason why not working right (use distilled water to top them off). On a 2018, I am surprised you don't have cranking for starter battery and deep cycle for the accessory battery. They don't make batteries as good as they used too. If I were switching batteries, I would go to AGM, Sam's Club has some great pricing on AGM if you have a membership or know someone who does.

My 2014 came with dual battery setup and I fill/drain with engine off all the time, saves hours on engine. I added a 2nd accessory battery in 2017 for a total of 3 just cause I wanted more juice, but not cause the 2 batteries couldnt not handle it, I am just OCD like that. Also installed a 3 bank NOCO charger/maintainer and keep it plugged in anytime boat is home in the garage (that way you only have one plug in and all batteries are charged/maintained). I also check water level in the batteries 1-2 times a year and they always need a little bit, so definitely something to check. Mine are wet cell Interstate batteries.

If your batteries sat in boat all winter and started with a low charge, they may have gotten low enough that they will not fully re-charge now.

[Az182]

Thanks for your help. You are correct about AGM batteries.

I emailed Nautique direct to confirm the batteries they recommend. I've attached it here for reference in case it helps anyone else.

It's now clear my issue is that the wrong batteries are fitted, they are standard starter batteries.

[blueroom]

I wouldn't be surprised if a number of dealers are putting the standard Deka marine battery in new G's and not AGM's. $100 battery x2 instead of a $300 battery x2.

[Infinity]

AGM are expensive for sure but I would say worth it if you are buying a new one anyway. Sams Club has great pricing on the Duracell AGM marine batteries tho, here are 2 examples. Starting and deep cycle, group size 34M @ $119....& Deep Cycle, group size 31 @ $179 each.

https://www.samsclub.com/sams/durace...lp_product_1_1

https://www.samsclub.com/sams/durace...lp_product_1_2