2 is better then 1+1?

[Renato Candongas]

I fully understand the advantages of setting two batteries in parallel (A) but why not hook them like (B)?

My thinking is that on (B) you can choose to have one or two (full system amp) according to an specific need.
Scenario 1: Say one battery is enough to have you running for 3 days, if you are out just for a weekend you can just use one battery.
Scenario 2: 1+1 means you will know precisely when you reached 50% of your "off grid" time.

One argument is that having them always connected would reduce the load the system will be subjected thus keeping the voltage of the system higher and possibly making it charge faster or increasing the life of both batteries then if you discharge more just one battery at a time.

Comments?

 

[billiebob]

depends on the distance between A and B
but correct me if I am wrong, fuses are on the discharge side, not the charge side

 

[Renato Candongas]

depends on the distance between A and B
but correct me if I am wrong, fuses are on the discharge side, not the charge side

Well, they are there more as a switch to turn each battery in and out into the system then a fuse, sorry for the confusion.

A and B are at the exact same distance, the only difference is the ability to use two or one at a time.

 

[Rando]

The issue with 'B' is keeping the batteries in balance. If you run one way down, then tie them together to charge, yo run the risk of either not fully charging the discharged battery, or overcharging the charged battery. You also get a longer life out of the batteries if you discharge them less - running them in parallel, each only gets discharged half as much.

 

[billiebob]

Well, they are there more as a switch .

Don't use a breaker as a switch, get a bona fide switch.

 

[john61ct]

The current coming from a charge source is often much lower than what the battery will produce under a short condition.

That is why both circuit protection (fuse usually) and emergency/safety isolation switching is at the battery end of a long wire, ideally only inches from if not right at the post.

Most charge sources do not get CP on their side, every device or termination adds resistance thus voltage drop and power loss in operation.

When a collection of (usually identical same datestamp) batteries comprise a single bank, there is usually just one fuse and one switch.

Intra-bank wiring must be physically protected against accidental shorting, and of course everything well strapped down against shifting.

If you have multiple unlike banks, used separately but feeding the same circuits (not an optimal design) then each gets its own switch and fuse.

 

[Alloy]

Don't use a breaker as a switch, get a bona fide switch.

View attachment 577497

Switching breakers are made to do both.

 

[Alloy]

A breaker/fuse protects the wire.

In A the wire would be sized for 100A

In B the wire from the junction point of the 2 batteries to the controller/alternator/dist panel would be sized for 200A unless a 3rd breaker is used.

My system has 4 -12V (2x6V) banks each with a disconnect and individual swiching breakers protecting the charging souces / solar controller / dist panel.

 

[john61ct]

Switching breakers are made to do both.

But unless you're getting top notch hardware (expensive), their duty cycle lifespan can be very limited. Especially if high current loads are running when switched.

Blue Sea switches are designed for that specific purpose, will give very safe service for decades and don't even cost that much.

 

[Alloy]

But unless you're getting top notch hardware (expensive), their duty cycle lifespan can be very limited. Especially if high current loads are running when switched.

Blue Sea switches are designed for that specific purpose, will give very safe service for decades and don't even cost that much.

Also important the device be rated for DC. AC devices can be used but it is important the mechanical time is taken into account.

If there's a budget then cost needs to be matched to the purpose. Blue Seah makes cheaper and expensive products.

I've never seen a switching breaker that was mfg by Blue Sea. They are rebranded mostly from Carling Technologies.

Marine Switches, Battery Disconnects and Circuit Protection

Carling offers a variety of marine switches and marine circuit breakers, ranging from hydraulic-magnetic and thermal breakers to GFCI/ELCIs

www.carlingtech.com

The disconnect for my solar panels has breakers from Midnight Solar which are rebranded.

 

[Renato Candongas]

But unless you're getting top notch hardware (expensive), their duty cycle lifespan can be very limited. Especially if high current loads are running when switched.

Blue Sea switches are designed for that specific purpose, will give very safe service for decades and don't even cost that much.

I guess Blue sea is not what it used to be in terms of quality...

Amazon Sign-In

 

[john61ct]

Not the type I'm talking about, at all. That may in fact be a relabeled cheap Chinese product given the price and selling platform.

I did not mean to imply BSS is "the" solution, hundreds of other vendors to buy from just as good, just not cheap ones unless NOS on eBay or something.

Most platform reviews are fake, I **never** pay attention to them at all for 6-7 years now.

BSS will promptly take care of such issues if this is a genuine report. Such things do arise, no company is perfect.

 

[john61ct]

Example of a proper DC switch conservatively current rated, very reliable likely for decades, see spec sheet for loaded duty cycle.

e-Series Compact Battery Switch Off/1/Both/2 No Alt. Field Disc. | West Marine

Check out our e-Series Compact Battery Switch Off/1/Both/2 No Alt. Field Disc. and more from West Marine!

www.westmarine.com

At high amps good DC circuit breakers cost hundreds per, would be silly to use over proper fuses.

And still not suitable to use for a routinely operated switch.

 

[john61ct]

And of course beware counterfeits, very common these days

 

[Renato Candongas]

Not the type I'm talking about, at all. That may in fact be a relabeled cheap Chinese product given the price and selling platform.

I did not mean to imply BSS is "the" solution, hundreds of other vendors to buy from just as good, just not cheap ones unless NOS on eBay or something.

Most platform reviews are fake, I **never** pay attention to them at all for 6-7 years now.

BSS will promptly take care of such issues if this is a genuine report. Such things do arise, no company is perfect.

In fact I found it very strange to not have a single reply from BSS when so many ppl have complaint about the same issue.