Another battery question

[BeeJay]

Ron,

Check out these wiring diagrams. There's a difference between what you're describing (2 paralleled 6V sets wired in series) and what is recommended by industry experts (multiple 12V series sets wired in parallel).

94 Battery Wiring Diagrams

This could be a worthwhile read when considering battery wiring:

https://www.impactbattery.com/blog/tutorials/how-to-charge-marine-and-rv-batteries-in-parallel/

 

[psneeld]

I don't believe you understood what I was describing, and possibly I did not do the best job of describing the house battery bank. At the bottom left of your diagrams you will see "3 Parallel 12V" batteries. What I had was that same exact bank, but only 6 volt GC batteries, each rated at 225 AH. So with the ONE BANK you have 3 X 225 AH = 675 AH AT 6 VOLTS !!!
You take two (2) of these banks, and hook the minus (-) of one bank to the (+) of the second bank. Now you have a SERIES of 2 banks, each bank has 6 volts at 675 AH. When connected in SERIES, the total of the two banks is 12 VOLTS and the 675 AH remains the same.


Sorry if I did not make my self clear. If you refer to your 3 parallel diagram, but with only 6 volt batteries, not 12 volt, you will have the combined AH but the same voltage. When you take the two banks of 3 each 6 volt batteries in parallel, AND hook those 2 banks in series, the voltage is 6 + 6 = 12 volts at the 675 AH. Again, sorry if I did not do the best job of explaining myself in my prior text. Captain Ron D. Sandy Eggo.

You get the same amp hours either way......

The question is how they compare in charging and discharging

 

[BeeJay]

You get the same amp hours either way......

The question is how they compare in charging and discharging

Yep - I agree, but maybe worth considering. I changed my battery set up to balance the charging when I replaced the batteries a few years ago. The hope is that they will last longer and it would be kinder on them. The old batteries had loads taken from part way along the bank and were treated pretty bad and still lasted 8 years so maybe not worth the effort other than peace of mind. The water use now seems to be similar across the bank so who knows, maybe I will get 8 years and 3 days out of this set. (Probably more likely 7 years will tick over and I’ll change them as a matter of course and it would of been a waste of time)

 

[psneeld]

Yep - I agree, but maybe worth considering. I changed my battery set up to balance the charging when I replaced the batteries a few years ago. The hope is that they will last longer and it would be kinder on them. The old batteries had loads taken from part way along the bank and were treated pretty bad and still lasted 8 years so maybe not worth the effort other than peace of mind. The water use now seems to be similar across the bank so who knows, maybe I will get 8 years and 3 days out of this set. (Probably more likely 7 years will tick over and I’ll change them as a matter of course and it would of been a waste of time)

Were yours in pairs or groups then in series?

 

[sdowney717]

When I got my boat, PO had four 6v golf cart type. 2 linked for 2 banks. They did not crank well the engines. When they failed, were about 5 yrs old. I just was not impressed. Bought an 8D, terrible choice. Huge heavy. Got 2 yrs out of it. Then bought used starting batteries for 25 dollars. They lasted 4 to 6yrs. Just as good as the others and cranked well. Recently decided since used where up to $45, got the Duracells. The 31 farm was used 1 yr old for $45. Tested like new. Seeing I have generator not been worried much. I had a Motorcraft battery . It was in boat used before about 4yrs. I used it for 4 more yrs. Then I put in car. It is now 11 yrs old and like new. That Motorcraft was ford dealer and somehow has survived.

 

[tiltrider1]

When I got my boat, PO had four 6v golf cart type. 2 linked for 2 banks. They did not crank well the engines. When they failed, were about 5 yrs old. I just was not impressed. Bought an 8D, terrible choice. Huge heavy. Got 2 yrs out of it. Then bought used starting batteries for 25 dollars. They lasted 4 to 6yrs. Just as good as the others and cranked well. Recently decided since used where up to $45, got the Duracells. The 31 farm was used 1 yr old for $45. Tested like new. Seeing I have generator not been worried much. I had a Motorcraft battery . It was in boat used before about 4yrs. I used it for 4 more yrs. Then I put in car. It is now 11 yrs old and like new. That Motorcraft was ford dealer and somehow has survived.

GC batteries do not make good starting batteries. They make great deep cycle battery banks. Like wise if you want to kill a starting battery use it as a house battery. 8D batteries come in many forms, there are starting versions and deep cycle versions. Their are also huge differences in cranking amps with 8D’s. I’ve seen as little as 650 cc and as much as 1350cc.

It is very hard to have battery bank discussions due to the Apple vs Orange comparisons. Battery quality varies greatly, no two people cycle batteries at the same %. Poor chargers can shorten battery life, poor maintenance, bad wiring, all kinds of things have an effect on battery life.

Some practices are better than others.

 

[FlyWright]

I bought a boat that came with 3 8D batts - 2 8Ds as a house bank and the other for start. I was replacing the whole shebang and wanted to pack the most bang into the solid 8D boxes. The GC-2 fit the bill perfectly with 3 GCs per 8D box. They sat a little higher but I had room to work with. I ended up increasing my house from ~440-660AH in the same footprint giving me a ~50% increase. (I sure don't miss lifting those 8Ds in and out.) As a GC-2 from Costco, I can return one anytime within 40 or 48 months (?) for a free replacement. It's about the best battery support I can afford on my budget.

I like having a larger bank from the 6 GCs but the larger the bank, the better the charging needs to be. In my case, I also had to upgrade cables, switches, combiner, charger, SOC meter, inverter, alternator and external regulator. In the end, it was worth it.

 

[sdowney717]

Good idea on upgrading the charger . Mine maxs at 30 amps on the gauge. It does 3 banks. It has lasted since 1970. I did replace couple output diodes. Charger made by Raritan. Bigger banks might be an issue for me. Yrs ago called and talked to Vic. When I gave him model and serial, he was surprised and pleased it was still working. Said he probably hand built mine.. It was based on a popular mechanics article from 1960's. It is not ferroresonant. Has some fancy feedback circuitry. I could even improve it adding in an equilization cycle by modifying the circuit. He sent me the schematic. I am just too busy to do that. And it works as is.

 

[BeeJay]

Hi psneeld,


Mine are in series.

I only mentioned that it could be worth thinking about the effect the wiring may have on how they are charged to try and draw a comment.

I don't know enough about batteries to give any valid advice myself.


I think it really depends on how they are used and we a varied lot in that regard.


Although balanced charging makes good sense to me, it could be that if the charge isn't balanced across the bank, but you regularly charge the bank fully, that the battery or batteries receiving the lower charge get everything they need anyway so may make little difference.

There are some pretty smart people here (I suspect yourself included) that I hope will be able to comment if balanced charging is just a nicety or something worth considering when making changers to the banks.

 

[tiltrider1]

The more things you do right the longer life you will see out of your batteries. What is hard to say is how significant balanced charge would be as there are so many variables in the whole system.

 

[catalinajack]

GC batteries do not make good starting batteries. They make great deep cycle battery banks. Like wise if you want to kill a starting battery use it as a house battery. 8D batteries come in many forms, there are starting versions and deep cycle versions. Their are also huge differences in cranking amps with 8D’s. I’ve seen as little as 650 cc and as much as 1350cc.

It is very hard to have battery bank discussions due to the Apple vs Orange comparisons. Battery quality varies greatly, no two people cycle batteries at the same %. Poor chargers can shorten battery life, poor maintenance, bad wiring, all kinds of things have an effect on battery life.

Some practices are better than others.

GC batteries do not make good starting batteries? Tell that to my twin Lehmans. Recently, I depleted my eight house GC battery bank to 22%. The engines started without any difficulty, any. No separate starting batteries for the Lehmans. I do have two Group 27's dedictated to starting my generators. Yes, I have two on board.

 

[psneeld]

By nature of battery design/chemistry, they all have their niches..... It's not to say they can't overlap .....but it isn't what they are best at....

 

[FlyWright]

The more things you do right the longer life you will see out of your batteries. What is hard to say is how significant balanced charge would be as there are so many variables in the whole system.

+1 Most accept a certain imbalance in charge as a compromise for the lower cost of cabling as depicted above. I've got this cable configuration and don't see much more than a few thousandths of a difference in voltage across the batteries after 2 years. I last got 5 years years out of a 6xGC set. They only failed after a slow-dying charger finally gave up the ghost. I expect an easy 7 years out of this set.

 

[sdowney717]

GC batteries do not make good starting batteries? Tell that to my twin Lehmans. Recently, I depleted my eight house GC battery bank to 22%. The engines started without any difficulty, any. No separate starting batteries for the Lehmans. I do have two Group 27's dedictated to starting my generators. Yes, I have two on board.

8 golf cart batteries!, would start the engine ok, even depleted. that is a lot of batteries.
I had 2 golf cart batteries, and they did not crank well the engines.
Made me wonder at the time if the starters were going out.
I took the starters apart, could not see anything wrong, took them to a starter repair service, guy looked them over and said they were ok.
Putting in a starting battery, they cranked great.

I had 4 golf cart in 2 banks, but the banks were separate to each engine, and it was poor cranking. That setup was done by a previous owner. If I had 8 golf cart batteries joined together, my engines would also crank great.

And the batteries were not new, had a few years on them. They failed on me all 4 about the same time a few years after I got the boat. Their lifespan was not spectacular, not any longer life than the starting batteries I used afterwards..

When they finally failed, they were swollen up on their sides like other batteries do. So I suppose they sulfated. Most of my starting batteries, the failures are shorted cells, so I would get 10 or 8 volts.

One week the battery started the engine, next week, one battery 10 vdc, another 8 vdc. The 8vdc was paralleled with another good battery and it is ok. The charger ramped up the volts to 15.6v output and they were gassing. The charger knew something was wrong and tried to compensate. And had to clean up some acid in the battery tray.

A good idea is to sprinkle a layer of baking soda in the tray- box to neutralize battery acid.

 

[FF]

Start batts have very thin plates and insulators and littl space below the plates.

This gives them the surface area to crank at higher voltage, for a while.

Happily if over cranked the gas formed on the plate surface will lower the voltahe , till all the gas leaves.

House deep cycles will start as well as stat batts IF they have the same surface area to create the voltahe.

Thick plates , thick insulators and space at the bottom for failed lead mean that even at the same weight , the deep cycles need to be ganged to create the required surface area.

 

[JDM]

You get the same amp hours either way......

The question is how they compare in charging and discharging

Just put in four pairs of six volt batteries. Great for long stays at anchor. Only strange thing is that bank voltage drops to 12v almost as soon as charging stops (shore, alternator, or generator.). This is with sophisticated smart chargers. Old 12v system used to start at 13.5+\- and slowly drop as batteries discharged. ????

 

[FlyWright]

One of my banks was doing that recently and I found I had a short in my alternator to that bank that was draining the battery. Replaced the alternator and problem solved.

 

[Bacchus]

JDM
That sure sounds like something is draining them.
I'd start by turning everything off and checking Amp draw w a clamp on at the bank to see if there is A draw.
Also... aren't the chargers switching to float mode?

 

[wpc691]

Start batts have very thin plates and insulators and littl space below the plates.

This gives them the surface area to crank at higher voltage, for a while.

Happily if over cranked the gas formed on the plate surface will lower the voltahe , till all the gas leaves.

House deep cycles will start as well as stat batts IF they have the same surface area to create the voltahe.

Thick plates , thick insulators and space at the bottom for failed lead mean that even at the same weight , the deep cycles need to be ganged to create the required surface area.

2x on plate surface area. My 6 x GC2 inverter bank spins the starboard 3208 like a top; this is the setup the boat came with, and the old bank lasted 5 yrs. I replaced the port 2 x 8D start bank with 3 x Grp 34 Interstate Workaholics, work like a charm, and I didn’t need a squad of Marines to get them in. In addition to the parallel toggle on the flybridge, I have a rotary parallel switch in the engine room to connect the banks if needed.

 

[kchace]

Just put in four pairs of six volt batteries. Great for long stays at anchor. Only strange thing is that bank voltage drops to 12v almost as soon as charging stops (shore, alternator, or generator.). This is with sophisticated smart chargers. Old 12v system used to start at 13.5+\- and slowly drop as batteries discharged. ????

Yeah that's not normal sounding. You have an ~800AH bank - that's a lot of power. I have the same setup and even with my usual 8 Amp house load it takes a while to bring the voltage down to under 13. Of course when you say 12V I hope you mean something more like 12.6V? First thing to check is to make sure things are wired correctly. Also, how is this voltage being measured? Either the meter itself or the wiring to it may have an issue. Another thing to check is for a load. Frankly, if its load related you must have at least a 10-20 Amp load to bring the voltage down so quickly.

Ken

 

[kchace]

Yeah that's not normal sounding. You have an ~800AH bank - that's a lot of power. I have the same setup and even with my usual 8 Amp house load it takes a while to bring the voltage down to under 13. Of course when you say 12V I hope you mean something more like 12.6V? First thing to check is to make sure things are wired correctly. Also, how is this voltage being measured? Either the meter itself or the wiring to it may have an issue. Another thing to check is for a load. Frankly, if its load related you must have at least a 10-20 Amp load to bring the voltage down so quickly. I also wonder since the bank is brand new that maybe you have a defective battery?

Ken

 

[FF]

"Only strange thing is that bank voltage drops to 12v almost as soon as charging stops (shore, alternator, or generator.)."

From here my guess would be there not fully charged , as fully charged they should rest at 12.7 or .8.

What style V regulator is charging ? What is top charge voltage?

What does the SOC meter say?

 

[JDM]

6v system

Not a charging problem. We put in a new 100 amp Balmar. Alternator with smart regulator. Batteries hold twelve volts for at least 12 hours(haven’t tried for more than that). Just seem to indicate 12volts as soon as charging stops. Thought it might be a quirk with 6volt pairs. Not really a problem.

 

[ranger58sb]

Not a charging problem. We put in a new 100 amp Balmar. Alternator with smart regulator. Batteries hold twelve volts for at least 12 hours(haven’t tried for more than that). Just seem to indicate 12volts as soon as charging stops. Thought it might be a quirk with 6volt pairs. Not really a problem.

12 point how many volts? There's big difference between 12.2 and 12.5, etc...

If you mean 12.0, the batteries are seriously discharged.

-Chris

 

[Delfin]

That was my thought. I’ve always approached it with creating 12v batteries and then connecting them in parallel instead of creating large 6v batteries and connecting them in series.

I’d love to hear from some of the electrical guys if there is any difference.

Either approach works, although there are issues with series connections of 6v batteries to make a 12 v unit, and the more 6v batteries you series connect before connecting them in parallel increases the possibility those issues will crop up.

Before connecting in parallel, the series connected 6v batteries s/b charged, then equalized as a 6v pack. If you don't do this, then if there is one cell that is weaker than the others - and the more cells you series connect the more chances of this - then when being discharged the weaker cell will give up voltage to the strong, further weakening it and eventually causing failure. The net effect of this is that in a series connection, the total capacity of the pack is determined by the weakest component, whereas in parallel it is a function of the sum of capacities.

According to David Smead, who wrote the book "Living on 12 Volts", if batteries are connected in series, the above described phenomenon means the more series connections you have, the more you should limit the depth of discharge to preserve battery life. He summarizes by saying "In general, best performance will be achieved by parallel connections, thus series connections should be avoided unless space availability and battery availability force you into building extra capacity from 6v units."

 

[Delfin]

Not a charging problem. We put in a new 100 amp Balmar. Alternator with smart regulator. Batteries hold twelve volts for at least 12 hours(haven’t tried for more than that). Just seem to indicate 12volts as soon as charging stops. Thought it might be a quirk with 6volt pairs. Not really a problem.

At 12 volts resting, you have about 20% capacity, which is effectively a dead battery. If that is truly what your pack is charged to, if it hasn't failed yet it will soon. If it is performing well for you, then it is being charged to a higher voltage than you've indicated, since no LA battery will sustain itself without serious sulfation at that charge voltage.

 

[FlyWright]

Just put in four pairs of six volt batteries. Great for long stays at anchor. Only strange thing is that bank voltage drops to 12v almost as soon as charging stops (shore, alternator, or generator.). This is with sophisticated smart chargers. Old 12v system used to start at 13.5+\- and slowly drop as batteries discharged. ????

JDM, Have you charged your batteries without a load on them? Try charging your batteries without ANY loads connected and see what the battery charge looks like after a full charge to float and a 24 hr rest. If the voltage stays up at 12.6 or higher, your batts are probably fine but you might have a parasitic load on the batteries. If the charge drops off, you might very well have a battery problem.