(2) 6 volt golf carts as a starting battery

[izzy1554]

My 2 12v batts are toast along with my batt charger so I'm redoing the whole system- batteries, battery switch with ACR, charger and wiring.

-I'm going to upgrade my battery cables from 4GA to 1GA.
-Replace my 1-ALL-2-OFF battery switch with a Blue Sea System Battery Switch ACR.
-Pro Mariner Pro Nautic 1250 12 Volt 50 Amp 3 Bank Charger
-(4) 6 volt golf carts batts. 2 for starting. 2 for house.

I talked with my co-worker and he said (2)6 volts golf carts batts is not a good starting batt.

If that is true, is it ok to have (2)6 volts golf carts as a house and have 1 12 volt batt as my starter? Is it ok with my charger?

My engine is a Beta Marine 20 with a 70 amp alternator.

I don't want to mess up my new batteries if I have a bad plan. What do you guys think?

[CSY Man]

Use 4 golf cart batteries for a house bank, then add a dedicated start battery separated from the house bank, but use a combiner for charging them all at the same time.

[Dockhead]

Your colleague is right. Use a 12v starting battery for starting.

I don't know whether that will be a problem for your charger or not -- read the manual. My charger has a second output which is specially for a starting battery and gives a smaller current. I don't use it, because it outputs 24v while my start battery is 12v.

If you have any doubt, then just install a separate charger. You only need a very small maintenance charger for a start batt, so this is not expensive.

Do not use a battery combiner switch ("One, Two, Both"). Keep the banks completely separate. For the unlikely emergency case where you have a dead start batt and charged house batts, keep jumper cables. But with no combiner switch and a separate charger, you are unlikely to ever have a dead start batt.

[Dockhead]

P.S. -- it sounds like you have a single alternator. You will need to split the charger from the alternator somehow. An echo charger is preferable to combiner relay as the charge cycle will be very different between start and house batteries.

[izzy1554]

ugh... what about my battery switch? the blue sea with acr:

Blue Sea Systems' Dual Circuit Battery Switch - Blue Sea Systems

[Dockhead]

Originally Posted by izzy1554

ugh... what about my battery switch? the blue sea with acr:

Blue Sea Systems' Dual Circuit Battery Switch - Blue Sea Systems

This is not really the best way to charge dual banks, especially when they are different types and capacities.

This type of switch also creates a risk of flattening the start batt by leaving it in the wrong position.

If I were you, I would get rid of it.

[estarzinger]

Originally Posted by izzy1554

-(4) 6 volt golf carts batts. 2 for starting. 2 for house.

I talked with my co-worker and he said (2)6 volts golf carts batts is not a good starting batt.

If that is true, is it ok to have (2)6 volts golf carts as a house and have 1 12 volt batt as my starter? Is it ok with my charger?

I use two 6vt batteries as my start bank and eight in my house bank.

For my engine (75hp yanmar) the 6vy batteries are 'overkill' as a start bank and I could get away with a lighter and cheaper start battery. But I use the same batteries in both banks in order to then occasionally rotate them (I mostly just rotate the connector cables and only occasionally physically move them). This makes the whole bank last longer, because the start batteries don't get cycled (and the batteries in the house bank string get moved around and more equally used).

Regarding battery switches, I believe the preferred solution today is three 'on/off' switches - house 'on/off', engine start 'on/off', and combine 'on/off'. I disagree with dockhead about not having the combine option and 'using jumper cables'. If you need to start the engine quickly and the start bank is dead, a switch is fast while jumper cables are slow.

I also have an ACR battery combiner, which is perfect (reliable and does the job) assuming the battery chemistry in both banks is the same.

[colemj]

There is no problem at all using the ACR in your application - even if you go with a 12V starting battery and 6V house banks. The only time an ACR would be problematic is if you mixed battery types like flooded and gel. There is no problem mixing battery sizes or characteristics of the same type and the charge cycles are the same (there is actually only a single profile for combined batteries).

If you mostly keep the batteries on a charger and use the boat for short cruises, I would put all 4 6V batteries as a house bank and use that bank for engine starting also. There will be no problem turning a 20hp diesel using 6V batteries or any other type of deep cycle.

However, this leaves you vulnerable to a dead bank and not being able to start the engine. If this is a concern, then I would just buy a cheap Walmart starting battery and keep the 4 6V in the house bank. Use the ACR to charge both banks.

But put the risk in perspective - you will have 450Ahr of house capacity - even a bilge pump running for a whole day or two will still leave you the ability to start the engine.

Mark

[capt-couillon]

Simple lesson in difference between Deep Cycle and Starting batteries.

Storage of energy in any Lead/Acid storage cell is based on the chemical reaction between the lead "plates" in the battery and the sulfuric acid electrolyte.

Standard "Starting" batteries are physically constructed for their normal use. Short high current discharge. Short high current recharge (via engine alternator) This means they have thin plates usually of "sponge" construction as the chemical reaction necessary for discharge/storage of energy starts at the surface of the plates and works its way inward.

Deep Cycle batteries (including "golf cart" batteries) are built for long low current discharge and recharge. This means the plates are thicker, and usually less porous as the slow rate of discharge/charge allows time for the chemical reaction to penetrate the thicker less porous lead plates.

Each type is physically constructed to reflect it's expected discharge/charge cycle. Deep cycle type batteries are usually heavier for a given amp/hr rating due to thicker plates. Reason for using 2 6V deep cycle batteries in series rather than a single 12V deep cycle of the same capacity and construction is purely weight and size. A single lead-acid cell has a nominal voltage of 2V. A single 6V battery has 3 cells connected in series hence 3 fill holes. A single 12V battery has 6 cells connected in series. 2 6V are easier to get in and out due to weight and allow more configurations due to size.

Wet-cell / AGM / Gel type cells all use the same chemistry. Differences are in the method of storing the H2SO4 electrolyte. Advantages, disadvantages and uses have and are being debated elsewhere on these forums.

[Sailormantx]

Originally Posted by CSY Man

Use 4 golf cart batteries for a house bank, then add a dedicated start battery separated from the house bank, but use a combiner for charging them all at the same time.

This is the exact system I use, it works great. Blue Sea sells a battery switch with a "combine" position , use it on the house bank for charging from the engine and also for jump starting the engine if its battery is down. Do remember to turn the switch back to normal position when the motor is shut down so the starting battery is not drawn down. Blue Sea also makes an automatic combiner for charging, but I prefer the manual method.
Evans' idea of using another pair of 6 volt batteries is well worth a thought, I can see a number of advantages to having all the same type of batteries.

[noelex 77]

Originally Posted by capt-couillon

Simple lesson in difference between Deep Cycle and Starting batteries.

As a general rule deep cycle batteries are less suitable for delivering the high current needed for starting, but 2x6v deep cycle golf cart cart batteries are not going to to even break into a mild sweat starting a 20hp engine and are perfectly suitable (in fact overkill) for this application.
You could use a much smaller starting battery, but as others have mentioned there are some advantages buying and maintaing the same type of batteries for start and house.

Which bank is your anchor winch wired too?

It sounds like your boat may have been set up with idea of two equal banks using bank 1 as the house bank on odd days and bank 2 on even days. Running the main engine every day charging both banks.
This is very old fashioned, but can still work well if all charging is done on the main engine and you are not the forgetful type.

[izzy1554]

thanks guys, with more and more research i will stick w/ my 1/2/all/off switch & go with the 4 GC2 6V as my bank #1, 500cca starting/reserve for bank #2 (hopefully i have room for 5 batts), ACR, and alternator output to bank #1

i believe my 70 amp alternator has a jumper wire that go to the starter and then goes to my batt switch...

anyone have a wiring diagram for the beta marine 20 w/ 70 amp alternator?

[valhalla360]

Deep cycle are fine as long as they are rated for sufficent cranking amperage.

A starting battery is designed to put out a lot of amps but for only a short time. If you deep cycle it, you will wear it out very quickly.

A deep cycle will put out less amps (for the same size battery) but can be cycled much deeper without much harm.

The reason for starting batteries is if you have a runabout with a 300hp engine, you would need a large heavy deep cycle battery bank to get enough cranking amps to start the engine. A smaller lighter starting battery can do the job without taking up as much space or weight. With cruising sailboats, you need a large heavy deep cycle battery bank for house electrical needs and with relatively small engines, it is already plenty big enough to turn over the engine (as long as the bank isn't too far from the engine as voltage loss over the cables becomes a problem).

I suggest looking up the cranking amps recommended for the engine and comparing that to the deep cycle batteries accounting for voltage drop between the batteries and the starter (wire size and length can have a big impact). If it meets the ratings, go for it, no harm will come of it.

We have the option to pull start so we don't even bother with seperate banks.

[DotDun]

From Trojan Battery website:

Trojan Battery Company

Can I use my deep-cycle battery as a starting battery?
deep-cycle batteries can be used for engine starting but starting batteries should not be used for deep-cycle applications. A deep-cycle battery may have less cranking amps per pound than a starting battery, but in most cases a deep-cycle battery is still more than adequate for the purpose of starting an engine.

[foggysail]

Has ANYBODY ever had experience where a deep discharge battery......in good condition .... failed as a starter battery???? In my over 30 years with boats, I have never, ever had trouble starting anything with a deep discharge battery.

Another thing to keep in mind, CCA means cold cranking amperes at 0 degrees F. A battery that has about 600 CCA will provide about 900 HCA at 80 degrees F.

Foggy