Charging a single bank of two batteries in parallel

[JayBee74]

Hello all, new sailboat owner here (1984 Ericson 30) in the planning stages of rebuilding my shoddy electrical system.

My main goal is to simplify - it is currently set up with a Off/1/2/Both in some weird attempt to have a start and house bank when it's entirely not needed IMHO.

Anyhow, on to the question. I'm going to rewire to be a single bank in parallel with a simple on/off switch. Now when it comes to the charging from a AC powered charger, would it be better to have a single bank 10 amp charger hooked up to both batteries since they are in parallel or use a 2 bank charger hooked to each individual battery?

Thanks.

[Wolfe10]

Combining into one battery bank would mean if you run it down, no way to start the engine.


With that said, with two 12 VDC batteries in parallel, connect the positive lead from the charger to one battery's positive and the negative lead from the charger to the other battery's negative.


You could achieve very close to the same thing by leaving your current switch in BOTH.

[S/V Illusion]

Originally Posted by JayBee74

Anyhow, on to the question. I'm going to rewire to be a single bank in parallel with a simple on/off switch. Now when it comes to the charging from a AC powered charger, would it be better to have a single bank 10 amp charger hooked up to both batteries since they are in parallel or use a 2 bank charger hooked to each individual battery?

Thanks.

They aren’t individual batteries anymore once parallel connected.
If you parallel connect 2 12v batteries, that is one bank. You don’t have two banks with which 2bank charger can connect.

[Calif.Ted]

My main goal is to simplify - it is currently set up with a Off/1/2/Both in some weird attempt to have a start and house bank when it's entirely not needed IMHO.

That's not "weird", that's standard for boats. Your opinion is invalid, "both" combines the batteries when appropriate and allows separation when not, rethink this. Also standard for fire and rescue equipment where 1 dead battery could lead to disaster.

[JayBee74]

Thanks ya'll I'm aware of the cons. Fixing the currently shoddy installation would require more time than I currently have and my proposed solution fits all my needs on a day only sailor. My only non engine related loads are lights and don't get used unless on shore power hanging out at night.

Originally Posted by Calif.Ted

That's not "weird", that's standard for boats. Your opinion is invalid, "both" combines the batteries when appropriate and allows separation when not, rethink this. Also standard for fire and rescue equipment where 1 dead battery could lead to disaster.

It most definitely is weird if you actually saw how the previous owner wired it up. Not only would I not be any worse off than if I only had one battery I would be approximately 672% safer than I currently am.

https://marinehowto.com/1-2-both-bat...onsiderations/

relevant quotes from link -
"Over the years most all boat builders, of both sail and power, have installed the simple and redundant 1/2/B switch. The switch, I believe, has gotten an undeserved bad rap over the years. Why? It’s really not necessarily due to the switch itself, but rather due to the way most builders install them, and the way many boat-owners have used them."
"If you wish to continually move the switch from 1 to 2 then 2 back to 1 etc. etc. it may feel like you have a START & HOUSE bank but you really don’t. In the #1 or #2 position each bank serves both starting and house purposes. Starting and House services cannot be isolated from one another with a 1/2/B unless you add another ON/OFF switch."

[Madehn]

i would suggest that you do a little more reading on your setup-- some basic books out there like 12volt bible, the 12 volt doctor's practical handbook, etc. They would help you get a better handle on the basics to tackle beginning projects without making mistakes. Personally i would rethink your plan to combine everything into 1 bank. JMHO- your boat- your choice as i am fond of saying. best of luck

[Reefmagnet]

Use one battery as a cranking battery, and the other as a deep cycle house bank. Connect the two with an "ACR" (automatic charge relay).

Use an on/off switch for the cranking battery and a suitable circuit breaker with integrated switch for the house bank. Both these additional components are cheap to buy.

When charging, connect the charger to the cranking battery.

[Ballsnall]

Originally Posted by JayBee74

My main goal is to simplify - it is currently set up with a Off/1/2/Both in some weird attempt to have a start and house bank when it's entirely not needed IMHO.

Anyhow, on to the question. I'm going to rewire to be a single bank in parallel with a simple on/off switch.

There is a reason you have 2 seperate banks, redundancy. Second highest reason assistance calls is electrical/battery problems.

As your wiring is sub par by all means get it sorted out but do consider how you will manage a failed or flat battery. As you have decided a single bank is right for you then I have found the lithium starter packs are excellent to keep onboard for emergencies, just need to remember to charge them at least every 6 months.

[PaulCrawhorn]

Neither

just one big charger, ACR (VSR) holding the two banks in parallel, only while charging