New House Battery (2)-24 vs (1)-4D

[islandrunner70]

Hi gang,

For my house bank I had (2) Group 24 size FLA batteries each @ 75Ah. One of the batts died over the winter. Solidified....I think it was a bad batt when I got the boat from the PO. Lesson learned...

So I have been hunting around looking for a new 24 size batt to replace the dead batt.

In my battery box the batts are stacked long ways. So I actually have room to fit either 2-24 size batts or 1-4D size batt. I was trying to stay with FLA so I would not have to revamp the entire electrical charging system as it sounds (from reading a multitude of posts in the forum). Also I am still relatively new to the different battery types and wanted to stay with something I am a little more familiar with.

I remove the batts in the fall and store in my garage during winter.

But from my research it seems that I can get a single 4D with more Ah than 2-24 batts.

One con i could think of is that the 4D wieghs more than 2-24s. This may make it difficult to remove and install at the end/beginning of the season.

I would appreciate any other input from this group.

Thanks.

[djmarchand]

Most, maybe all FLA 4Ds are not true deep cycle batteries. I suspect the same can be said for Group 24s. So that may be why your 24 died. Unless the battery has an amphour rating stamped on the battery, it is probably not a true deep cycle- thicker plates, etc.

So what to do? Maybe the best thing is to bite the bullet and buy either a 4D AGM or two 24 AGMs. There isn't much, if any difference between a starting AGM and a deep cycle AGM.

I hate 4Ds and 8Ds because of the weight, but if you can live with that I would go with an AGM 4D if it will fit.

David

[NewMoon]

Have you considered a pair of 6V golf carts, wired in series to make 12V? Seems to me they fit in almost the same the footprint as 24's, if you can handle the additional height, maybe 1", and width, maybe less than 1/2". The pair I have for my travel trailer (Deka FLA) measure 10.23 long, 7.13 wide, and 10.88 high. Great house batts, available in FLA or AGM.

[islandrunner70]

I haven't considered the 6v option.

So this would be 2-6V batts wired in series to biuld 12v. So both batts have to be the same size in amperage, correct? Amps are not added for wiring in series.
No impacts to charging system, alternator, correct?


From the distributors, it appears that 2-6v batts have nearly twice as much capacity(Ah) as 2-12v batts. Even in some cases over a single 4D. This appear correct?

Thanks for the assistance.

[Stu Jackson]

Yup, no issues at all.

[Target9000]

Originally Posted by islandrunner70

I haven't considered the 6v option.

So this would be 2-6V batts wired in series to biuld 12v. So both batts have to be the same size in amperage, correct? Amps are not added for wiring in series.
No impacts to charging system, alternator, correct?


From the distributors, it appears that 2-6v batts have nearly twice as much capacity(Ah) as 2-12v batts. Even in some cases over a single 4D. This appear correct?

Thanks for the assistance.

This is correct. Two 6v wired in series will yield a 12v battery. The available amp hours will remain the same. So two 220amp/hr 6v batteries in series will become a single 12v battery with 220 amp/hrs.

They have some additional benefits. They're true deep cycle batteries and since it is 2 batteries instead of one, its easier to move than a single 4D battery.

There are tons of posts on this forum about this type of setup. Suggest a search and then do a little research.

[djmarchand]

If two 6V golf cart batteries will fit, then that is your best solution. But they are bigger and taller than Grp 24s so maybe not.

And one 6V GC typically has an amphour rating of 220. But two wired in series to give 12V still has 220 amphours. Only if you wire them it parallel (for 6V) do you get 440 amphours.

David

[btrayfors]

Golf cart batteries are by far your best bet. They are:

1. more robust than either the group 24 or 4D batteries;
2. smaller, easier to move than 4D or 8D batteries;
3. have thicker plates and will take more abuse and give longer service;
4. require one less jumper cable (only one, instead of two if paralleling);
5. have more AH capacity, typically 220-235AH;
6. available just about everywhere in the world; and
7. plenty powerful enough for both engine starting and house bank service.

Trojan T-105's have been the "gold standard" for years, but they keep raising their prices. To my mind, they are pricing themselves right out of business.

After having used T-105s for over 20 years, and having studied them intensely for several years, when I replaced my six house batteries last year I did some further research and decided to go with Crown industrial golf cart batteries. The model I chose is rated at 235AH, has a white case and red top, and has the thickest plates on the market. They are made in the USA and are a quality product. I'm very happy with them so far. I got them for just under $100 each; Trojans are about $135-150 each.

FWIW,

Bill

[islandrunner70]

Thanks for the excellent feedback by all.

I am strongly leaning the dual 6v batt route.

An additional question. My battery box is located right underneath the stairwell and right in front of the engine. So the batteries are enclosed in this compartment with the engine (Volvo Penta 2003). I don't think it gets extremely hot under their but I think any heat above 70 will be bad for the batts.

Is there any concern with explosion, etc. from the engine with the gases that come out of the batt during charging?

Thanks

[westwinds]

Originally Posted by islandrunner70

Thanks for the excellent feedback by all.

I am strongly leaning the dual 6v batt route.

An additional question. My battery box is located right underneath the stairwell and right in front of the engine. So the batteries are enclosed in this compartment with the engine (Volvo Penta 2003). I don't think it gets extremely hot under their but I think any heat above 70 will be bad for the batts.

Is there any concern with explosion, etc. from the engine with the gases that come out of the batt during charging?

Thanks

If the charge voltage is above 14.2, then oxygen and hydrogen can be generated. An equalization charge can produce more gas. However, not a problem unless you are very close to the battery with an electrical spark, like disconnection from a portable battery charger. Otherwise, the gases, especially hydrogen, dissipate very quickly.

About temperature, here is something: Charging Batteries at High and Low Temperatures

[islandrunner70]

Update:

Thanks for all the great advice. I am going with the Dual 6volt batts. After some careful review I decided to move the house bank to a different location away from the engine compartment and next to the charger.

Question on connecting the dual 6-volt batts wired in series and connecting it to the charger.

Plan::

Boat_GND connected to (-) Batt_A (+) connected (-) Batt_B (+) connected to Boat_Pos and connected to Chrg(+).

Correct?

[michaelmrc]

ive been a big fan of the interstate 6v golf cart batteries. formerly known as the u2200 series now called the gc2-xhd. rated at 232 ah. ive had 2 in my boat now for 4 years and still running perfectly.

[btrayfors]

Originally Posted by islandrunner70

Update:

Thanks for all the great advice. I am going with the Dual 6volt batts. After some careful review I decided to move the house bank to a different location away from the engine compartment and next to the charger.

Question on connecting the dual 6-volt batts wired in series and connecting it to the charger.

Plan::

Boat_GND connected to (-) Batt_A (+) connected (-) Batt_B (+) connected to Boat_Pos and connected to Chrg(+).

Correct?

Yes, but:

(1) there should only be ONE boat ground; usually this is the engine; no problem hooking the house battery negative to this boat ground.

(2) Be sure to fuse the positive cable from the batteries. Only two types of fuses are ABYC approved for this: ANLs or MRBFs. These have the requisite 5,000 ampere interrupt capacity.

Bill

[islandrunner70]

Thanks for the info Bill.

I plan to purchase two Crown Deep Cycle batteries [CR-260] providing to 260Ah capacity.

What size fuse should I use between the batts and the connection to the house electrical system?

[btrayfors]

Originally Posted by islandrunner70

Thanks for the info Bill.

I plan to purchase two Crown Deep Cycle batteries [CR-260] providing to 260Ah capacity.

What size fuse should I use between the batts and the connection to the house electrical system?

That depends. Normally, fuses are used to protect the wiring, so you'd need a fuse appropriate for the size wire used.

If you plan to ever use the house batteries for engine starting -- as in an emergency -- then the fuse needs to be large enough to handle the in-rush current of the starter, say 300 amps or so.

Fuse size depends on how you're wiring your boat, i.e., wiring size, maximum load, etc. And, nothing says you can't use multiple fuses, e.g., a 300A fuse and heavy cable on the circuit used for emergency engine starting and a smaller fuse on the smaller wire feeding the panel and house loads.

Bill