Combining Batteries?

[Loren Beach]

http://www.svsarah.com/Sarah/ewUpgrade12VDC.htm

While doing some information-gathering on line I found this interesting site.
The author seems to have put in some quality time on electrical additions as well as some serious sea time.
I am close to (finally) getting my BlueSeas #8080 distribution panel installed and am looking over the choices in combiners.

Sidebar: The only quandary now is whether I have painted myself into a 12 volt corner (metaphorically speaking) by staying with a two-golf cart battery flooded housed bank and a spiral cell starting/emergency battery. I wonder how/if these can live together if charging were to be combined on a regular basis.

As usual, I just post the info for your comment and consideration, not because it's representative of any "right" or wrong way to do things.

Lots of experienced boaters and engineers on this site, and the input is always educational.
Thanks in advance (TIA)... as they say on the internet!
:nerd:

We are going sailing later today.
Fair winds to you, too!


Loren

 

[celtium]

Thanks

Loren,

I am considering work on my battery situation as well. I run 2 each West Marine 12V deep cell bats, 1 for starting and standby, the other for house. I would like to add a dedicated starting battery and move the deep cell used for starting to house only.

I am sure this gents site will be of help. And of course Nigels book is always good as well!:nerd: Thanks for the post!

Jay
E 38-200
SF Bay

 

[Tom Metzger]

Loren - It is a very bad idea to charge an AGM start battery and a flooded cell house battery together. The AGM will tend to hog the charge current while not needing it. This is because an AGM cell has a lower internal impedance than a flooded cell. It shouldn't hurt the batteries.

There are current limiting combiners out there which would help, but I am not a fan of using any combiner because it lengthens the time to charge the house bank. We have been through this before, ad nauseum.

 

[Loren Beach]

clarification requested

It is a very bad idea to charge an AGM start battery and a flooded cell house battery together. The AGM will tend to hog the charge current while not needing it. This is because an AGM cell has a lower internal impedance than a flooded cell. It shouldn't hurt the batteries.

There are current limiting combiners out there which would help, but I am not a fan of using any combiner because it lengthens the time to charge the house bank. We have been through this before, ad nauseum.

It's too bad that AGM batteries are so expensive. I was looking around for quotes and found that a pair of golf cart format batteries would run abourt $500. , give or take.

BTW, can you expand a bit on your comment that: "The AGM will tend to hog the charge current while not needing it. This is because an AGM cell has a lower internal impedance than a flooded cell. It shouldn't hurt the batteries."
I might infer from this that actually charging the two types, agm and flooded, in parallel would not harm either bank. (?)

Thanks,

Loren

 

[Tom Metzger]

Loren - I was referring to both types having very similar charge voltages. I probably should have added a caution about over heating the AGM battery.

This might be a problem with an AGM house bank also because the start battery would see a much longer than necessary high voltage charge. There is no way to get around the fact that the start battery doesn't need the charge that the house bank needs.

Even if the starting battery is not overcharged I wouldn't charge them together because of extending the time required to charge the house bank. I don't want to sail with the engine running.

 

[Mark F]

Hey Loren,

What I have found is that AGM's and regular flooded batteries require different charging voltages. AGM's being a bit lower voltage. I don't think you can charge flooded with AGM without some kind of regulator (if you can at all). The issue being that you can lose water if you overcharge a battery. With a flooded battery you just add the water lost but with the AGM being sealed it's lost forever and eventually the battery dies.

That said you just have to be a little more vigilant regarding charging with the AGM.

There are some deals out there on AGM batteries, I bought four of these; http://www.batteryconcepts.net/yuasa/ub121100.html for my electric inboard. West Marine had a sale a year ago on group 27 AGM's for $150 (I bought four of those also).

Prices are coming down on lithium iron phosphate batteries http://en.wikipedia.org/wiki/Lifepo4 . Seems like a lot of advantages with this technology.

 

[stuartm80127]

Batteries

I installed two FullRiver G27 batteries this Spring. Purchased from DC Battery Specialists in FL and the price was right. I installed with an ACR and a manual switch that I can use to combine the battery banks. Both banks are monitored by a channel on my Link 20.