What do you all think?. 36V just for the STB engine.

[Blain]

My STB battery bank no longer starts the engine without a parallel. Port engine battery bank seems to work fine. I am in a situation where I cannot easily get a hold of 8V batteries but I can get 12V batteries and 12v chargers. After reading all previous posts dealing with 36V, here is something I am considering as a solution for the time being. Easier process for the STB side. I would love to know your thoughts and ideas.

1. Disconnect the STB alternator fuse in the STB engine room metal fuse box to deactivate the 32V alternator charging the bank.
2. Install 3 x 12V batteries in series (instead of the 4 x 8V batteries).
3. Install a 3-bank 12V charger for the 3 x 12v batteries. Disconnect the current 32V charger dedicated for the STB bank.
4. When underway, Turn on the 3-bank 12V charger. Power to the charger would be delivered by a Victron Inverter from Lithium bank. I have a Balmar alternator charging the lithium bank when underway (160Amps), plus 30-40Amps from solar... so plenty to keep the Inverter happy.
5. also, batteries would be charged when running the generator (1-2 hrs per day as needed).

Of course, I can continue to parallel the banks until I am able to get 8V batteries. However, this setup can come in handy if something happens to the Port bank in the interim.

Thank you in advance.

 

[Pascal]

That’s a lot of hassles… why can’t you get 8V batteries ?

 

[Blain]

I agree it's a lot of work but we just got to the Bahamas and will be expecting visitors On & off for the next 8 weeks and we were also hoping to head to Turks (if our insurance approves) after that. I called around in Nassau but no one is answering the phone.
I remember seeing lots of Golf carts in Spanish Wells.. maybe a repair facility has 8V batteries.

 

[Boatsb]

First question.

Did you check the batteries before you headed to the bahamas? How and what was the result?

Second question.
How old are the batteries?

Third question

What charger? How do you know its good?

Batteries can be found there or shipped in. Its not cheap but that's why our customers have them checked beforehand.

 

[JD5652]

Definitely sounds like a huge hassle.
So, the 36V bank would ONLY be used for starting?
I've never had to do it, but I've heard you can get "things" shipped from the mainland to Bahamas pretty readily. But have no real world experience to validate that hearsay.

 

[divert00]

Technically, I think your solution is ok. When in the Bahamas, sometimes creative workarounds are necessary to save the cruise. You should be able to have 8v batteries shipped to Nassau or Spanish Wells. But, no guarantee when they might arrive and cost will be steep. There are lots of golf carts on SP and Harbour Island. I’d call SP. Start with R&B Boatyard or Dion’s Workshop.
John McCarley - USCG 100T Master
Water Colors
Wrightsville Beach NC

 

[Blain]

Thank you gents. I spoke with Makers air at length. The cost will be pretty steep, not helped by weight & the arbitrary tariffs. Could try to send on a ship.

Divert00, thank you for the info.. I will try the SP outfits first and see how it goes.

 

[Pascal]

How old is each bank? I d be tempted to get three 12v batteries (probably group 31) and set them up with jumper cables ready to use if your port bank craps out.
That’s why I hate how Hatteras didn’t use a dedicated house bank!

 

[Blain]

Thanks, Pascal. Both banks were newly installed in 02/2024. But I suspect the batteries were manufactured prior to that date.

If the Port Bank craps out as you say, I am going to be in a lot of hurt. The windlass & bilge pumps won't like 38-40V. I would probably cobble together 4 good batteries from the 2 banks and rebuild the Port bank & hope for the best.

I see Rolls have various good 8V options.. FLA & AGM. If I cannot get something sorted here, I may try to connect with a fellow boater who is crossing over in the next 4-6 weeks.

 

[Pascal]

2 years old isn’t bad. Flooded or AGM? If flooded Make sure the water level is good. If AGM make sure your charger is set for AGM
Personally I don’t care for AGMs. I ve always had Flooded on my boat and AGMs in the boats I run because that s how they came. I can’t say the AGM have lasted much longer than the flooded even with high tech multi stage charger. The only benefit of AGM is not having to top them off but if access is easy, no big deal.
There has to be golf cart dealers in Nassau.

 

[Captain Ralph]

Why not some cheap 2 x 12v & a single 8v. These should be in the islands.
Are all of your 8Vs bad at the same time? Maybe just one good one and pick up a cheap set of 12s till you get home.
Then the engine gauges, and anything else on that battery bank will work. You may need to hit the parallel switch but everything will work while operating.

Currently I'm using 2 x 4Ds and a single big 8v cart battery,
My 12Vs never spun so fast.

Swamp logic sometimes works.

 

[Boatsb]

And you get what you pay for in free advice. It’s not good to mix and match batteries. Thats how over and undercharging happens. Ever see a melted or exploded battery?

Do it right or dont do it all. Cost is not the choice to take over safety.

 

[Blain]

Thank you Capt. Ralph. I really like your recommendation as it seems that 3 of the 4 8V batteries in that bank are still good, so I can use one of the good 8V batteries & buy 2 x 12V.

My question is, would the 32V charger or alternator create charging imbalance between the 12 V & 8V batteries? but I guess as long it is still reasonably safe for charging then a little imbalance is OK… For a temporary setup for 3 months..

 

[SKYCHENEY]

Yes, you will have a charging imbalance which is not ideal but good enough for getting by in a pinch.

 

[Captain Ralph]

Thank you Capt. Ralph. I really like your recommendation as it seems that 3 of the 4 8V batteries in that bank are still good, so I can use one of the good 8V batteries & buy 2 x 12V.

My question is, would the 32V charger or alternator create charging imbalance between the 12 V & 8V batteries? but I guess as long it is still reasonably safe for charging then a little imbalance is OK… For a temporary setup for 3 months..

No matter what my battery configs have been, seems the top battery always cooks, fails and needs more attention. I wonder was it your top 8v battery that failed?
In an emergency, Just find another 8V cart battery and go.

Rite up to about 5 years ago, I was advising others that strange things would happen (charging imbalance) and warned against this idea.
But I had to do something; Swamp logic driven by swamp finances (retired with old boat).
I had to try it myself.

I try to check water levels 3 to 4 times a year. I think I'm due now.
It does seem that they are gassing and requiring water every visit, just as when I still had all 8v batteries.
So for me, it seems to be working.
Your in a pickle and already deployed. Maybe worth a try? I don't think you can hurt anything short term.
Keep a frequent & tight water level check schedule up until you get a feel for mixed battery brands.

 

[Boatsb]

Just poorly installed and this happened. Think about the mismatch cell size before you do it.

 

[piripucha]

Fifteen years ago when the country started to go to hell, and 8v batteries whre unavailable I experimented with two 12v and one 8v, The inbalance did not work well with the battery charger! After I while
I switched to 36v. and installed a 3 banks charger for each battery bank. I have not have any issue with the pumps or the lights, I had to change the breakers of the head pumps ( galley maid) . It was supposed to be a temporary thing, but 15 years have passed and they are still running. As a temporary thing I think you are on the clear. Good luck

 

[Blain]

Thank you all very much for the great input and commentary. I have been calling around to secure 8V golf cart batteries as these may be available. So far, no luck in the Exumas. Still waiting on shops in Nassau? . If that fails, the 3 x 12v batteries & a new 3-bank charger would be my next step. Mainly for safety until we are back & order a new set of 8V Rolls.
I found this type of charger but it only had 6A per bank.. 18 amps total.. charging capacity. Not sure if that is enough. I would also be charging the batteries underway through the inverter. My balmar capped at 80% capacity pushes 140amps/hrs at 1200rpm, more at higher RPMs.

Since it's the STB bank, I don't think that I need to worry about breakers. I need to decide on the alternator output. Thinking of disconnecting it completely.