Mixing Group 27 and Golf Cart Batteries

[Adelie]

Originally Posted by Peregrine1983

Hi all,

I am upgrading a solar and deep cycle house battery system. There is currently a compartment and trays sized to hold two Group 27's. I want to expand this battery bank using this space and some space available in other nearby compartments.

I know the best bang for the buck will be to do all new golf cart batts, but...

What is the downside of having two of these Group 27 Deep Cycles and a bank of 2 golf car batteries in a separate compartment?

The charge controller is a Sun Force 12v 30. The solar array is 425 watts monocrystalline.

I would assume the Group 27's might charge more quickly if the controller sees the bank as one big bank. Will this be the case? Could this result in overcharging of the 27's?

I would rather go all Golf Cart batteries as I'll get more amp hours for the buck, but I'd then have to modify two compartments instead of one, and it seems dumb not to utilize the already-built trays and compartment built for the group 27's.

I could also go all Group 27's, but then I'm sacrificing amp hours/$.

Any help appreciated.

In later posts you talk about wanting real Deep cycle but don't think you can get them in Gp-27 form factor.

There are actually at least 3 sizes for grp-27
Size L (inches) W (inches) H (inches)
27 12 1/16 6 13/16 8 7/8
27F 12 1/2 6 13/16 8 15/16
27H 11 3/4 6 13/16 9 1/4
https://www.batteryequivalents.com/g...endations.html

The link you have above seems to be for 27H. What are the real dimensions of your trays? Can you fit the 27Hs? If you can fit something with a slightly larger foot print you might be able to fit a Trojan T-1275 which is a real deep cycle are each 150Ahr batteries at the 20hr rate.
L (inches) W (inches) H (inches)
12 7/8 7 1/8 11 1/8

I have 2 T-1275s installed on my boat.

[Sunsetrider]

Originally Posted by Adelie

L (inches) W (inches) H (inches)
12 7/8 7 1/8 11 1/8

I have 2 T-1275s installed on my boat.

Adelie - can I ask: are you using both as house? and therefore do you have a cranking battery for start?
My battbox is 27.5 x 11.25 x 12.25
Currently filled with Group 31.s it seems. One deep cycle and one start.
Upside down and I can/t fix it. They are not upside down in the pre submit stage.

[Adelie]

Originally Posted by Sunsetrider

Adelie - can I ask: are you using both as house? and therefore do you have a cranking battery for start?
My battbox is 27.5 x 11.25 x 12.25
Currently filled with Group 31.s it seems. One deep cycle and one start.

I have a Cal-20. Those 2 batteries are everything.
Currently they are mostly used for traction, I daysail on Mission Bay and use a 33lb thrust electric motor to get in an out of the marina and to get back if the wind dies on me. When we have gone cruising on the boat, the electric motor is replaced with an outboard (pull start). For recharging I have a 30W panel I drop on deck on the south side of the boat, and the batteries are fully charged by the following weekend when I'm ready to go again. If I were to seriously cruise the boat I would mount an arch across the back with 160-200W of solar, plus I might put in a bimini with 100W on each side. Every panel would get it's own small MPPT controller.

In the long run I want a Cal34 or Cal36. In the short to medium term I intend to go with the largest house bank I can fit which will start the main engine without a dedicated starting battery. In the medium to long term I intend to mount an outboard and convert the Atomic-4 to an electric drive with something in the range of 240Ahr at 48v battery capacity for both house and traction.

[Adelie]

I researched long an hard to settle on the T-1275s.
I only have room for the 2 so that meant I had to get 12v, one battery dies I still have power, just diminished capacity. With 2-6v batteries I would have gained a bit in capacity and probably also longevity but if I lost one I would only have 10v at best which isn't going to do much if anything.

I have size limitations due to the small boat. I wanted FLA not AGM because I am not convinced of the longevity of AGMs if you can't get them to full charge almost every cycle.

I picked the T-1275 because Trojan has a pretty good rep and they are listed as Golfcar batteries which means there's a good chance they are real deep cycles.

Rolls didn't have any 12v that would fit that were flooded.
There was another top tier company I looked at but can't remember the name.
I looked at USBatteries but couldn't find anything that I was convinced was a deep cycle.

[Cheechako]

Originally Posted by Peregrine1983

Hi all,

I am upgrading a solar and deep cycle house battery system. There is currently a compartment and trays sized to hold two Group 27's. I want to expand this battery bank using this space and some space available in other nearby compartments.

I know the best bang for the buck will be to do all new golf cart batts, but...

What is the downside of having two of these Group 27 Deep Cycles and a bank of 2 golf car batteries in a separate compartment?

The charge controller is a Sun Force 12v 30. The solar array is 425 watts monocrystalline.

I would assume the Group 27's might charge more quickly if the controller sees the bank as one big bank. Will this be the case? Could this result in overcharging of the 27's?

I would rather go all Golf Cart batteries as I'll get more amp hours for the buck, but I'd then have to modify two compartments instead of one, and it seems dumb not to utilize the already-built trays and compartment built for the group 27's.

I could also go all Group 27's, but then I'm sacrificing amp hours/$.

Any help appreciated.

Contrary to popular theory, I have not had an issue with mixing batteries. I even had gel mixed with wet on one boat for quite a while, sold that boat with all batteries still working.
I've had battery banks with a shorted battery in them, and of course that's a problem, but it also proves that even "identical" batteries of the same age, may not be so for long. This was a live aboard cruiser not in marina and charged daily.

[DefinitelyMe]

Originally Posted by Sunsetrider

My other issue is whether a large suite of house batts will do double duty as starters. I don't see why not - it would simplify life considerably.

Yes absolutely. And they don't even need to be large. That's exactly what we do. No relays, one switch which stays on the entire time, minimal complexity, zero hassle. Honestly, the only reason I can see for having a separate starting bank is if you're leaving the boat for extended periods. If you're a liveaboard I just can't see how your batteries should ever be able to go flat.

[GrowleyMonster]

Originally Posted by laika

Another possibility if you have the height in the compartment is to get a pair of L16s, J305s or similar as opposed to 4 golf cart batts.

That's a good idea. However, there aren't any real low budget sources for those excellent batts. Sams Club has GC-2 usually for around $85 or so.

FWIW, I routinely took my GC-2 batts down to around 30% and they lasted almost 8 years in propulsion service as well as for a 48v house bank. I started out not allowing them to get under 50% but stuff happens. gp 27 won't stand up to that for very long, I don't think.

[Dockhead]

Originally Posted by Sunsetrider

. . . My other issue is whether a large suite of house batts will do double duty as starters. I don't see why not - it would simplify life considerably.

A bank of deep cycle batteries works fine to start a diesel engine. Provided it's in a decent state of charge.



But eliminate a separate start battery? I wouldn't do that. What if you run the house bank down?


I not only have separate start batts for BOTH main and generator, but none of these systems is connected in any way to the house electrical system. Separate alternators, separate chargers, nothing connected except starters and engine electrics, no interconnection of any kind. KISS.

[GrowleyMonster]

Originally Posted by Dockhead

A bank of deep cycle batteries works fine to start a diesel engine. Provided it's in a decent state of charge.



But eliminate a separate start battery? I wouldn't do that. What if you run the house bank down?


I not only have separate start batts for BOTH main and generator, but none of these systems is connected in any way to the house electrical system. Separate alternators, separate chargers, nothing connected except starters and engine electrics, no interconnection of any kind. KISS.

I like your style, DH.

[Adelie]

Originally Posted by Dockhead

A bank of deep cycle batteries works fine to start a diesel engine. Provided it's in a decent state of charge.



But eliminate a separate start battery? I wouldn't do that. What if you run the house bank down?


I not only have separate start batts for BOTH main and generator, but none of these systems is connected in any way to the house electrical system. Separate alternators, separate chargers, nothing connected except starters and engine electrics, no interconnection of any kind. KISS.

On a very large boat that works, I'm not sure I would call it simple but certainly a lot more redundant than echo chargers, Automatic Charging Relays and things like that.

On small boats with limited space on the engine or in the engine room extra alternators may not be possible to install, nor do they necessarily fit with a budget set up.

[DefinitelyMe]

Originally Posted by Dockhead

A bank of deep cycle batteries works fine to start a diesel engine. Provided it's in a decent state of charge.



But eliminate a separate start battery? I wouldn't do that. What if you run the house bank down?


I not only have separate start batts for BOTH main and generator, but none of these systems is connected in any way to the house electrical system. Separate alternators, separate chargers, nothing connected except starters and engine electrics, no interconnection of any kind. KISS.

Each to his or her own. Personally I don't think that setup satisfies the KISS principle at all. What if I run the house bank down?! Well, it's pretty much impossible to do that without noticing but: I'd turn everything off, have a beer before it got warm and wait for the solar to do it's job.

[Adelie]

Originally Posted by DefinitelyMe

Each to his or her own. Personally I don't think that setup satisfies the KISS principle at all. What if I run the house bank down?! Well, it's pretty much impossible to do that without noticing but: I'd turn everything off, have a beer before it got warm and wait for the solar to do it's job.

+1...

[Dockhead]

Originally Posted by DefinitelyMe

Each to his or her own. Personally I don't think that setup satisfies the KISS principle at all. What if I run the house bank down?! Well, it's pretty much impossible to do that without noticing but: I'd turn everything off, have a beer before it got warm and wait for the solar to do it's job.

Well, to each his own.

Completely separated and redundant systems is certainly the most robust and failure resistant configuration from a systems architecture point of view, eliminating any single point of failure and eliminating complexity and potential failure points in interconnections between systems. All high end cruising boats are configured that way.

Next best is separate start battery with echo charger.

Worse than that is the old On Off Both combiner switch which used to be almost universal - all my boats prior to this were like that. You had to switch to Both when the engine was running, and then remember to uncombine the banks when you shut the engine down. Classic fail with this is forget to uncombine and run the batts down overnight. Happened to me I can't remember how many times. I used to carry extra long jumper cables for this case :banghead;

If this never happens to you with your single banks, then, well, you must be far smarter than the rest of us.

NOW in modern times there is another way to deal with that problem - one of those newfangled li-ion emergency starting units. I guess that would neatly solve the emergency starting problem, so maybe make a single bank look quite different.