Adding a parallel battery for house load

[Lost Islanders]

We have a 2008 260 DA with twin batteries and a selector switch. When on the hook, we'll use batt#1 as our house battery for stereo, fridge, lights, etc. and save batt#2 for starting the gen or engine. I'm considering adding another battery in parallel with batt#1 to extend the time that we can remain on batteries (w/o having to start the generator to charge them). I will wire the new battery in parallel with the existing battery and use the same diameter cables; connect the positive (red) cable to the battery post and the negative (black) cable to the ground post on the back of the engine block. I'm pretty sure the battery charger can handle charging both if they get drained down. My question, has anyone completed this or know of a better way to do it? I'd like to get some feedback before I purchase the cables (custom made based on new battery location). Kudos to CSR forum I have found a good source for the cables.

Dean

 

[cod]

The only thing I would do different is rather than connect the batteries directly together, I would install a battery switch so you can have the choice of using either battery or both.

 

[wyrman]

I have two banks of two,for a total of four batteries. I like having two together for the house batteries as they last quite some time.

 

[tdschafer]

You may just want to check the output on your alternator as well. I'd imagine that if you start it up after a long time on the hook the draw could be large. That's if you don't have the time to run your genny first. I'm assuming it's portable or you wouldn't be needing the extra batteries.

Sent from my SM-G930V using Tapatalk

 

[BryanOnTheBay]

We have a 2008 260 DA with twin batteries and a selector switch. When on the hook, we'll use batt#1 as our house battery for stereo, fridge, lights, etc. and save batt#2 for starting the gen or engine. I'm considering adding another battery in parallel with batt#1 to extend the time that we can remain on batteries (w/o having to start the generator to charge them). I will wire the new battery in parallel with the existing battery and use the same diameter cables; connect the positive (red) cable to the battery post and the negative (black) cable to the ground post on the back of the engine block. I'm pretty sure the battery charger can handle charging both if they get drained down. My question, has anyone completed this or know of a better way to do it? I'd like to get some feedback before I purchase the cables (custom made based on new battery location). Kudos to CSR forum I have found a good source for the cables.

Dean

Also, you should always have matched batteries. Therefore, if you are adding one, replace the old since the old battery will go bad sooner, and kill your new battery. Also, you should look in to how to wire it up so that the batteries are balanced. That will make a difference as well.

This article discusses the issue: http://www.panbo.com/archives/2016/05/gizmos_new_firefly_battery_bank_working_out_the_details.html

Bryan

 

[wyrman]

Good point about matched batteries.
I renentlynhaf one of mine go bad so I replaced all four.

 

[Wylie_Tunes]

and the negative (black) cable to the ground post on the back of the engine block.

I prefer a more direct connection by running a cable directly between the two battery grounds. Skip the connection at the block.

and use the same diameter cables

How did you come to this? What size are the existing cables? what is the length of the new cables? whats the potential load? Food for thought.

I'm pretty sure the battery charger can handle charging both if they get drained down.

Whats its output and is it a distribute on demand smart charger?

Yes, I would suggest installing two new identical batteries on that house bank.

 

[bbwhitejr]

I did the same thing 18 months ago. Bought 2-new Grp 31s and one new tray. My boat was wired with 4/0 wire. Overkill, but I also had 2-custom 4/0 cables(1- red and 1-black) made. As stated above, just went + to + and - to - to connect the two new house batteries in parallel.

Also so added a ProMariner 1240P charger and we crank the gen for the AC and hot water, but no more to charge batteries. My system thus far has been flawless.

Bennett

 

[dpmulvey]

+1 to Bryan's post. If you are always going to use the same bank for house use, consider AGM's. Another option would be a couple of 6VDC golf cart batteries in series.

 

[Lost Islanders]

This is great information; thanks to all for your feedback. Good point on matching the batteries, size and age. Timing worked in my favor here as I was in the process of buying a new house battery earlier this year when I decided to purchase the extra. It's just taking some time to get it hooked up.

Bennett - our 260 is similar where we have 4/0 cables. I like the suggestion that Wylie_Tunes made to go post-to-post. I'll plan on doing that as well as evaluating upgrading our charger. My biggest challenge has been locating the space for the extra battery. Both of the existing batteries are tucked away nicely I the aft starboard area of the engine compartment. I unscrewed these and shifted them around but could not free up enough space to fit another battery in. I ended up locating it on the port side just below the charger, between the water heater and pump. Makes for a clean install but the cables become lengthy (approx. 10') and pricey. I haven't bought these yet but not too concerned with cost. Having the extra battery capacity will be worth it. Just curious where you located your extra battery?

 

[Creekwood]

Why not switch the bank wiring so the two house ones in parallel are together and the other is remote? You might be able to use existing cables better that way.

 

[trflgrl]

The only thing I would do different is rather than connect the batteries directly together, I would install a battery switch so you can have the choice of using either battery or both.

+1. When you're building a better mousetrap, build the best one you can!

 

[Wylie_Tunes]

If im reading correct, the OP already had a dual bank setup, and is looking to increase the reserve capacity of the house bank. The best way to do that, is to wire the two batteries together as one. They need to cycle together. creating another bank through a 2nd dual battery switch over-complicates the setup with one more manual switch to work, you now have to monitor each battery and switch when needed, and adds additional cabling and terminals. I dont see an advantage to this over simply wiring two together for 2X the Ah.

 

[bbwhitejr]

This is great information; thanks to all for your feedback. Good point on matching the batteries, size and age. Timing worked in my favor here as I was in the process of buying a new house battery earlier this year when I decided to purchase the extra. It's just taking some time to get it hooked up.

Bennett - our 260 is similar where we have 4/0 cables. I like the suggestion that Wylie_Tunes made to go post-to-post. I'll plan on doing that as well as evaluating upgrading our charger. My biggest challenge has been locating the space for the extra battery. Both of the existing batteries are tucked away nicely I the aft starboard area of the engine compartment. I unscrewed these and shifted them around but could not free up enough space to fit another battery in. I ended up locating it on the port side just below the charger, between the water heater and pump. Makes for a clean install but the cables become lengthy (approx. 10') and pricey. I haven't bought these yet but not too concerned with cost. Having the extra battery capacity will be worth it. Just curious where you located your extra battery?

My batteries are located aft Starboard as well, between the waste tank and the transom. My #1 Battery(cranking)- sat the most aft and was fastened down parallel to the transom. My #2 Battery(house) sat between the cranking battery and the waste tank also sitting parallel to the transom. I unbolted the house battery box and turned it 90 degrees so it sat perpendicular to the transom, moved it over close to the starboard side of the boat and had perfect room to mount the 3rd battery box right beside it. If I remember correctly, I ordered 12" cables to go post-to-post on the 2-new house batteries.

Initially, I looked at placing the 3rd battery on the port side under the charger as well, but I have a milk crate there for storage and I did not want to lose that as well as the expense of the cables to run side-to-side.

Hope this makes sense. I can post a pic Sunday night if necessary, but all 3 fit perfect in the same spot.

I just looked at some pics of the 2008 bilge and yours looks identical to mine and I remember a little more now. I had to relocate the blower hose, and I think I did move the battery closest to the transom a little closer to the transom. I was able to use all existing cables and just purchased 2-12" ones to hook the 2 new batteries together.

Bennett

 

[Lost Islanders]

Bennett,

Thanks for the info. I don't remember off-hand what series batteries we have. They are fairly large. I remember trying to squeeze them in side by side and even with moving the vent line, they were too wide. I don't think I tried to turn 2 perpendicular to the most aft battery. Seems like it's do-able. We'll be traveling for the next month which will have me waiting until I get back to give it a try. I like your milk crate install as well. Always looking for some extra storage space. I'll keep the group posted on the outcome.

Thanks again for everyone's input.

Dean.

 

[bbwhitejr]

Bennett,

Thanks for the info. I don't remember off-hand what series batteries we have. They are fairly large. I remember trying to squeeze them in side by side and even with moving the vent line, they were too wide. I don't think I tried to turn 2 perpendicular to the most aft battery. Seems like it's do-able. We'll be traveling for the next month which will have me waiting until I get back to give it a try. I like your milk crate install as well. Always looking for some extra storage space. I'll keep the group posted on the outcome.

Thanks again for everyone's input.

Dean.

Here is a pic:

 

[Lost Islanders]

Ok, I finally got around to installing the extra battery, and it fit in the same space as existing 2. Would be great to add some pictures but can't figure out how? Oh well, looks similar to Bennet's. Looking forward to some extended battery time!

 

[Lost Islanders]

ok, I figured out how to add pictures; adding the extra battery was easier but I think I got it figured out now.