Dual Battery Charging Question

[jryan]

Hey All, I've been reading about dual battery charging (or charging in general) and am starting to doubt that I may not be doing this right. I have a dual battery setup with a selector to switch between the batteries. My charger is a Schumacher SC-1200A which supports float mode. I'm reading about chargers boiling electrolytes out of the batteries. I'm now getting very nervous that my setup could be doing harm.

When I charge the batteries, I hook the charger up to a single battery (the one that's exposed and not in the battery box). My assumption was that since these were hooked up in parallel that it would charge them both. I'm now doubting that this is not accurate.

Any feedback or tips? Do I need to run out and buy a dual bank charger?
The boat is in my garage when it's not on the water.

 

[jryan]

Ok, that clearly wasn't charging both. I just hooked up the charger to bank no 2 and it's at 80%. Next question would be, is it ok to charge these in parallel?

 

[fireflymedic]

Ok, that clearly wasn't charging both. I just hooked up the charger to bank no 2 and it's at 80%. Next question would be, is it ok to charge these in parallel?

I would say no. Seems it boils out the water in the first battery to top off the 2nd. We have a 24 volt system in a truck and keep running into this problem no way to charge the bank without destroying 2 of the 4 batteries. (Using a 24v charger ofcourse)

 

[tabbibus]

you will likely need a 2 bank charger, like the NOCO genius. I also don't know about your switch set up (looks after market), but the stock switch for our boats necessitates a little mod to be able to charge more than 1 bank

 

[ripler]

You need a 2 bank charger. When you charge 2 batteries with a single bank charger the charger sees it as 1 battery and if 1 of the batteries is fully charged the charger has no way of knowing the other battery isn't charged.

 

[marcham]

How often do you use the boat? If more than 30 days between uses, and the boat is stored out of the water, simply turn the switch to off. Then every 30 days,turn the switch to both and plug in your existing charger to one of the batteries for 24 hrs. After 24 hrs, disconnect the charger and turn the batt selector to off.

A dual bank charger would simply avoid having to manually turn the batt selector to both. Charging 2 batteries of the same chemistry in parallel is perfectly normal.

Question, when you drive the boat, where do you set the batt selector? Ideally, you would set it for 1 or 2, since both are starting batteries. Without an automatic battery combiner (acr or dvsr), you will need to turn the switch to both with the engine running to charge both batteries. With regular use, another strategy is 1 for odd days and 2 for even days and don't worry about the both position unless you have starting problems.

 

[ZGhost]

You also should consider cleaning that rusty cable connector going to the battery post. That can interfere with the flow of electricity in both directions.

 

[jryan]

How often do you use the boat? If more than 30 days between uses, and the boat is stored out of the water, simply turn the switch to off. Then every 30 days,turn the switch to both and plug in your existing charger to one of the batteries for 24 hrs. After 24 hrs, disconnect the charger and turn the batt selector to off.

A dual bank charger would simply avoid having to manually turn the batt selector to both. Charging 2 batteries of the same chemistry in parallel is perfectly normal.

Question, when you drive the boat, where do you set the batt selector? Ideally, you would set it for 1 or 2, since both are starting batteries. Without an automatic battery combiner (acr or dvsr), you will need to turn the switch to both with the engine running to charge both batteries. With regular use, another strategy is 1 for odd days and 2 for even days and don't worry about the both position unless you have starting problems.

Well..I just bought the boat so we're out with it multiple times a week (practicing our boating skills before it gets busy). For now I'm going to charge them up when I get home one at a time and then take them off the charger. The day of boating, I'll double check them and make sure they are showing full voltage. Thanks everyone, I know it's a rookie question but it had me stressing out.

 

[Compatico]

You also should consider cleaning that rusty cable connector going to the battery post. That can interfere with the flow of electricity in both directions.

@jryan Once they're clean put the cables back on and then put a thin coat of petroleum jelly (Vasolene) over the exposed metal parts. They won't rust when coated - learned this from my dad who worked on vehicles in the military. Simple trick and very cheap. You can use white lithium grease too, but that costs 10x as much. A small tub of jelly will last for years and can be easily cleaned and re-applied as needed.

 

[marcham]

Well..I just bought the boat so we're out with it multiple times a week (practicing our boating skills before it gets busy). For now I'm going to charge them up when I get home one at a time and then take them off the charger. The day of boating, I'll double check them and make sure they are showing full voltage. Thanks everyone, I know it's a rookie question but it had me stressing out.

If you're out every week and using each battery alternatively, then there's probably no reason to use a shore charger. Do you spend long periods with the engine off and radio on?

One of your batteries is 5 years old, it's probably on it's last leg. Not too worry as long as the other starts the engine easily by itself. With 2 , you can wait for one to fail or start exhibiting reduced cranking power.

 

[anmut]

I'm tagging on a question here: Can you use two battery tenders to trickle charge your dual battery setup? I had one for my last boat, I was going to buy another for the new boat. Turn the battery switch off, clamp on chargers, done - right?

 

[ripler]

I'm tagging on a question here: Can you use two battery tenders to trickle charge your dual battery setup? I had one for my last boat, I was going to buy another for the new boat. Turn the battery switch off, clamp on chargers, done - right?

This is what I used to do before I installed an onboard dual charger, never had an issue.