double batts with perko, one tender or two?

[Puto]

I have a dual battery system managed by a manual perko switch. I have been leaving it on the lift with the switch in the OFF position. I hook a battery tender (Delco 800 water resistant) to one of the batteries. Is that enough for the system or do I need a tender for each battery? I usually move the perko to ALL when I'm underway, and then to "2" when I'm coved up, using it like a house battery. Then if I run out of juice with all my stereo playing and wife phone charging, I have the option of switching to "1" to start the boat, and then recharging while underway again.

Thanks

[jays0n]

I believe you would require 2 tenders. To solve the same issue I installed a Promariner Prosport12 marine battery charger (google search for the best price) that is made for 2 banks (or two separate batteries) and it doesn't care how the batteries are connected to each other. The different models have different charging rates and can be for single, dual or triple bank setups. I'm guessing the one I chose was around $140 plus I added an "inlet" below one of the seats, it's a covered male connector so you just have to run an extension cord into the boat and plug the female end into the inlet. We leave our boat this way all winter, very clean install and no issues so far.

[Marc K]

It depends upon the size of the tender and the size of the batteries.

Standard Marine batteries will draw about 1% (or a bit less) of their rated capacity on Float - typically 13.2v. So, if you have something like a 75 AH group 24 or smaller, they will need about .5 to .75 amps to maintain. So two of them in parallel could be supported by a tender with a 1 to 2 amp output. You want both batteries to be on the maintenance charge while stored, so the ALL position on the switch would be the choice.

Remember that flooded (wet) marine batteries have a self-discharge rate of around 10-%-15% per month. At 80% charge, they start to form sulfation internally on the plates. As the battery discharges further, the process accelerates. Over time, sulfation results in a loss of capacity.

If you run larger batteries, each with a 150 ah to 200 ah capacity you really should go with a multistage charger as jaysOn did.

Marc

[Steiner]

In addition to what Marc said, I'd recommend a Battery MINDer vs a Tender. The MINDer runs a constant desulfation cycle when in maintenance mode. Since I switched to them, I've not had a battery last less than eight years including the $25 Walmart mower battery.

[Puto]

Uh-Oh, so running the tender while the Perko switch is on OFF isn't doing me any good? Man, I'm out of my element here. I was running the above listed Delco, but now you guys are suggesting a MINDer instead? Is there a recommended model?

Thanks for helping me save my butt here.

[Steiner]

This would be a good one. A little cheaper on Amazon.
https://www.batteryminders.com/batterym ... esulfator/
https://www.amazon.com/BatteryMINDer-12 ... s9dHJ1ZQ==

[Marc K]

Your Delco charger might be doing exactly what you need. Just make sure that you are seeing around 13.1v to 13.4v on the terminals of BOTH batteries while in storage. Simple as that.

What is the amp rating of your Delco charger?
What voltage does it output?
What is the AH rating of your batteries?

Marc

[Marc K]

This would be a good one. A little cheaper on Amazon.
https://www.batteryminders.com/batterym ... esulfator/
https://www.amazon.com/BatteryMINDer-12 ... s9dHJ1ZQ==

Good advice.

They make good stuff and the 1.5A rating will support larger batteries like a pair of Group 31s, depending upon the brand.

[steve1313]

I have this one and the same perko switch you do.
It's made for for two batteries. Charges, maintains, conditions.

https://www.amazon.com/ProMariner-43012 ... nk+charger

[Flanker]

I've got a Battery Minder on the boat and Battery Tenders on my tractor and gator, haven't bought a battery in years.