6V Battery question

[megalops]

I swapped out my old house bank last year, trading 2 lead acid 8D for four L. A. deep cylcle 6 volts, Interstate U200.

I experienced an immediate decline in battery life, I struggled to keep a charge on them either from my engine and it's 100 amp alternator (with "dumb" internal regulator) or from my Xantrex true charge 40. They would drop to about 10.5 volts in less than an hour. Disappointing, as I expected better performance not worse. Nothing I did seemed to help. My daily load did not change in any significant way.

Today I borrowed a load tester from my mechanic. I disconnected all four batteries then let them sit for an hour and a half with no load on them. Then I tested them at the posts with my fluke multimeter. All 4 read 6.4 volts.

When I put the load tester on them 3 read right at 6 volts, but the 4th read only 5. Does this sound like the problem to you guys? Do you think I could have gotten a bad battery from the very beginning?

Thanks

[mitiempo]

Could be a bad battery from the beginning as you suggest. This is certainly not representative of golf cart batteries I have installed.
How much load was on them when they dropped to 10.5 in less than an hour?

I would try just 2 in series leaving the low voltage one and one other out of the mix for a day or 2 and see what happens.

[megalops]

Ok, I replaced the weak battery, with not so good results. I still can only charge the bank to about 12.3 V, either using my Xantrex tru charge 40 or the alternator on the engine (100 amp). When I switch the main breaker from AC power to DC power the lights dim significantly and the charge drops below 12 V within about 1 hour. Even with just 3 lights and my fridge running.

I have a 4d starting battery next to my house bank, so I switched the main cable (runs to the positive buss) from the house bank to my starting bank 4d. No dim lights, no voltage drop.

Again, I have had this problem ever since I converted my house bank from 2 8D to 4 6V.

Any help would be appreciated. I'm about to dump 4 1 year old 6v batterys and go back to 8D.

Thanks

[mitiempo]

Can you explain exactly how everything is wired and how it is charged. A picture might help if you have one.
I too have never had an issue with golf cart batteries, whether Trojan or other brands.

[s/v Faith]

Couple thoughts;

The 5v battery had a bad cell... sadly, it was a load for the rest of the bank (all cells that were connected to it were loaded).

The advantage of 2x 6v batteries is they can be replaced individually... accept if they are in parallel with other banks they can draw
the other banks down.

In other words, 2 x 6v = 12v... but if that 12v lives in parallel with another 12v battery and one cell dies then it will be exactly like having 2 12v batteries and you may have to replace them all.

Also, you might read your jumpers and check for a voltage drop (less likely). Place a load on the bank, and read voltage from terminal to terminal (between connected batteries). Should read nothing (or very very low voltage)...

[megalops]

OK, thanks for the tips guys.

I replaced the weak battery, then equalized, then gave them 48 hours on the charger. That bank will now get up to 13.2 Volts and hold it, whereas before I could never get it to take a charge over 12.2. I will check for voltage drop this week.

My lights still dim significantly though when I switch from AC power to DC power, which they never did with my old 8D bank.

[mitiempo]

What kind of lighting do you have that is both AC and DC?

[mitiempo]

All good questions, but the charger should float at 13.5 volts. 14.5 is bulk/absorption voltage for flooded batteries.

All 4 golf cart batteries are best used in one large bank without the ability to separate them.

[mitiempo]

A large battery bank is more efficient than 2 smaller banks. The bank is not taken to as low a state of charge as 2 separate banks so the batteries last longer and charging is easier to manage or automate,
Here`s a full explanation: http://www.sailnet.com/forums/gear-main ... esign.html

This is the better way to design a battery system and is used by the better manufacturers currently as well as by many who are re-doing their electrical systems.

Doesn`t have to be 6 volt batteries, multiple 12 volts, any thing from group 27 to 8D`s are used as well. As long as the result of parallel, series or serieséparallel adds up to 12 volts. But 6 volt golf carts are the best value in a deep cycle flooded battery.

[megalops]

OK, Let me see if I can answer all these questions...

1. Is there a bad connection? This was my first thought as well. I built all new jumper for the bank when I bought it and then redid them a few months later just to make sure. possible, i guess, buy there is no visible corrosion anywhere.

2. Are all connections in great shape? See above. Yes, I think they are. The cable from the positive post to the main positive bus bar for the house is older, but is still very supple. Also, I'm checking voltage at the posts, not on the bus bar.

3. Yes, the system is grounded to the engine. I was actually having some unrelated starting issues about two years back and upsized the ground cable. Also, (my boat is an old trawler) the two engines are connected together with a ground cable.

4. I can't really tell when my charger cycles on to meet demand, other than listening for it. It doesn't run very often, it is not like it is struggling to keep a charge up.

5. The Alternator is putting out a full load, not sure about the charger, though it is in good shape and is having no problem maintaining the starting battery, a 4d in a seperate bank.

6. I have not tried to isolate the banks. They are somewhat isolated when charging from the engines though. I wired the stb alternator directly to the start batt and the port alternator directly to the hosue bank (sometimes it is nice to have 2 engines).

7. Not sure if there is an amp draw with all the DC stuff turned off. I will check. If there is one it can't be much. Bildge pumps would be the only thing.

8. Yes, I am getting a full 110 volts to the AC charger, it keeps the start battery in really good shape.

9. The charger stays on all the time. It is automatic, a xantrex tru charge 40.

10. I can isolate the banks with switches. I have a simple on/off switch on the house bank, with a cable that leads from it to the "2" lug on a off, 1, 2, both switch. The number 1 lug on the off, 1,2,both switch leads to the house bank. I can combine the banks by leaving the house bank switch on and setting the starting bank switch to both.

11.The charger is set correctly.

12. My lights are DC, but on my main panel there is a switch for them in both the AC and the DC row. If I leave both switches on and turn on the shore power, the AC over rides the DC. They re probably 50 to 60% brighter when the shore power is on. They also get brighter when i combine the battery banks.

13. This bank has never gotten up to 14.2, even when all four batteries were brand new. It doesn't matter if they were charged by the xantrex or the alternator.

14. Here is how my batteries are wired: Batt 1. A jumper goes from the + post to the - post on battery 2. A second jumper goes from the - post to the -post on battery 3. Batt 2: A jumper goes from the +post to the + post on batt 4. the + post on batt. 3 is connected to the - post on batt 4. Hope that is not too confusing.

Thanks in advance for all your help.

Doug



4.

[mitiempo]

That sounds logical to me, and the charging arrangement with 2 engines makes sense as well.

Does the charging from the Xantrex Truecharge go direct to each bank? They are good chargers and I have installed several lately.

Are the negative connections from each bank to the main ground point, either a bus or one of the engine blocks, solid and not corroded?

If so it certainly sounds like you have done everything correctly. Have you tried using 2 of the golf carts and leaving the other 2 out of it for a few days? Rotating them this way could tell you something.

I'd love to see how AC/DC lighting circuit is wired. On any boat I have seen the lights are all DC and if plugged in to shorepower the charger is on, replenishing what is used by them.

[megalops]

The lights have always confused me as well. But since they have always worked just fine up to now, I have never worried too much about them. I guess I should do some digging.

Thanks for the tip on temporarily setting up a bank of 2 batteries. I will give that a try.

[Popeye1865]

I'm confused by your description your batteries should be wired like this.
Pictures of your wiring would help. something is missing you should have fair charging and good usage out of the bank arrangement you describe

http://www.vonwentzel.net/Battery/00.Gl ... rallel.gif