Batteries in Series

Yes and no. You are correct that the reason given to you is a bad reason to change all six batteries. Having one bad battery of a set of six is no reason to change all six. Having one bad battery of a set of six batteries of the same age is very often a sign that the other five will soon fail. Do you have to change them all at once, probably not. Depending on the circumstances you could accept the probable increased risk of a stranded golf cart and replace only the one battery. What's the worst thing that could happen, you could have to walk and carry your own clubs for the rest of the outing.

If you're the kind that likes to tinker, you might try a rejuvenation procedure...we have several threads here on techniques, and there are several on youtube....they sell kits on ebay...In any case I would check the date code and determine the age of the batteries...

Hey at around $1000, I want to get everything I can out of those batteries....

http://batterylifesaver.com/bls-for-golf-carts/

No problem with tinkering. Sulfuric acid powder,or liquid, is easy enough to come by at the pool store.

Incidentally, we have a fleet of golf carts where I work. I buy them. Every golf cart salesman I've ever talked to refers to them as golf "cars", not carts.

But, some of them cost as much as "real" cars.

When they start talking brand name, you know you're in trouble....

How about a Penwick?

....which is really cheap compared to the Garia....

Plain Jane EZ Go gas, with a bed, top, fold down windshield, street legal.

They pull little 4'x4' trailers.

To be honest, putting a thousand dollar set of batteries into a tens of thousands dollars vehicle makes more sense to me. Still $52,000 for a golf cart is very extreme.

Only because you are not a billionaire.

No.

Don't go all technical on us.

Watch the video. They use a powdered product. I could mean sulfur trioxide if that'll make you happy.

Change all six, if it has crossed warranty period. Short cuts wont work finally and you pay out more. Try to get more price for 5 batteries during sale.

Bite the bullet and replace them all.

Fred has part of the reason, but the other one is that the new battery will be strained much more doing some of the work its tired old buddies can't do. They'll soon die anyway.

The golf cart shop probably thinks that since you're just a dumb old fart, their logic will convince you to buy them all.

Buy them all, so you won't be worried about batteries while you're teeing off, and you can keep up with the other cart on the way to the 19th hole.

Oh, and don't waste your money on those clubs that say they can cure your slice with an off-set head. They don't work. At least none of the 8 that I bought ever helped me.

Didn't take you too long to find that out. :-)

Slow learner.

Wanna buy a golf club?

I don't golf and no clubs will help my swing. :)

Since the batteries are in series, can you explain how the old batteries can put strain on the new battery. What kind of strain? I understand that since all the batteries are the same age others may fail, but $$ may be an issue.

The old ones can't store, or supply as much power as the new one. So, the new one will have to supply more power to the system.

Batteries are like horses. They give as much as they have until they die.

You could try to check/recondition the weak one, per SE's suggestion, since you're retired, and I know that you can't play golf and drink beer all the time.

How's your slice? I've got a club that can help that.

It's a function of work. Older batteries will not hold the same charge they did when new and their internal resistance changes with time. As batteries age that resistance goes up.

In a series circuit arrangement the battery with the lowest resistance (i.e., newer battery) will be the battery that delivers the most current (does the most work).

So, given a set load, the newest battery must work harder than its companions to make up for the older, less capable batteries.

Think of it as a team of 6 people that are lifting a telephone pole. The pole always has the same weight, but if 5 of the 6 people carrying the pole are ill, more load is put on the 6th team member to accomplish the task of lifting the pole.

The same thing applies to batteries. The new battery will be forced to carry more than its share of the load to make up for its weaker team members.

Until they can't.

Technically, he is right. Mixing old with new puts higher stress on the new battery, which will shorten its life.

Best to start with a clean slate.

The best way to find out the condition of each battery is to charge it by itself and then test it with a "load tester"/"battery under load tester". This will give you a fairly accurate state of the battery's condition and therefore its potential future.

When the batteries are in series, linked like a chain, they also act like a chain. Only as strong as the weakest link. The string is unable to reach fully charged because one battery is weaker than the others or completely goes through the weak battery with no charge to it if shorted. This strains the batteries because they are being charged with too high a voltage.

To put the batteries to a test of actual performance charge them either individually at 6v each or charge them in parallel. This will charge all the batteries to each one to its highest level of charge. Then put them back in series and test them in that configuration if you have a load tester that will handle that combined voltage. If not, put them back in the golf cart, run it and compare it to previous performance.

If one battery is bad you can replace only that one and operate the cart until others fail. This is inconvenient since you will have to replace each battery at a time over a length of time. As others have said, replacing all batteries at once will require you to do this to all batteries only one time. Decision is up to you. Run the tests to determine what you have and then see what the "whole picture" is. Better to have more information about what you have.

Good Luck, Old Salt

No mercy for intoxication in Florida ...and I thought we drank (in excess) for other reasons, but there you go, you learn something everyday!

I realise about batteries of a similar age and work regime being the ones to team together. Just had a neighbour pass over 2 18v cordless chainsaw battery packs that were no longer accepting charge and a dead 14.4v pack from a similar aged cordless drill. (Internally, there are 15x 1.2v cells in the 18v pack and 12x 1.2v cells in the other). Of the 42 cell count, 14 were effectively dead. Some rough and ready purging got the dead count down from 14 to 9. (They were all the same spec lithium ions).

After some mixing and matching, neighbour has two reasonable chain saw packs, (replacement price around $80 each), and dollars in his pocket to buy a new cordless drill ... with 2 battery packs and a cordless torch ... around $35 on special.

Point noted that the chain saw battery packs will not last long.
There is a major hardware chain about to open its doors in the adjoining suburb so the neighbour believes with the pruning season coming that he could be in luck for the long handle chain saw replacement. I wonder why they keep changing the battery housings each season?

Old Salt has it right. You could change just the bad battery and not overload the new battery. This is because the available current has to go through all of the batteries in series, so if 5 of the batteries are kind of weak and won't put out their full amperage, the one new battery will comply and happily supply the same current--in effect, loafing along.

This isn't the case if all 6 batteries were in parallel.

You're faced with the old conundrum of "group replacement" VS "fix as they fail". If you change them all out when the first one fails, you can expect a reasonable working life before the next failure, but are probably leaving some money on the table by tossing batteries that still have some life left in them.

It seems to me that about 5 years is about what to expect for a lead-acid battery, so if the one battery that has failed is only 3 years old, you might expect the other 5 to last approximately another couple of years. (unless you bought low quality batteries that have lots of premature failures) Therefore, if you change only the one that fails, you can reasonably expect to have to service the next failure in a shorter time. No problem if you like doing this service and have a tester or a battery center that will test for you.

This is a constant headscratcher for businesses that have battery-backed up power supplies, where they may have many batteries in series as well as in parallel strings...do they replace the bum ones singly or do a group replacement?

Trying to rejuvenate batteries is a losing proposition. If you find something that really works, well, they've been selling various potions for fixing batteries since Volta was an apprentice. Most will give the battery a short term kick but end up just as bad or worse. For the best life, just buy quality batteries.

Jon.

Putting in a new battery will put a slight bit more strain on the remaining batteries, but that can be eliminated by putting in a used battery instead. Go behind the building where they stick the used batteries with your volt meter and load tester (buy one at harbor freight) and find the best used battery you can and swap with your bad battery. If you are sneaky and they don't catch you, it won't cost you. Many golf courses do this as a routine on their own carts, but always try to sell a customer on replacing all of them. I had an Electric car that had a 36 volt system and used to buy my batteries from a friend who went to the many Golf courses in Southern Nevada and bought all their used batteries for the scrap value. He would test the batteries and sell the good ones for10, 20, or 30% of new price depending on quality and sell the bad ones at a break even scrap value. He made good money. His batteries were fine.

My experience with this sort of situation is that the new battery will get overcharged as the charger will cycle to the demand of the older weaker batteries and tend to cook the new one. Finding a similar older one as previously suggested may be the best answer if you don't want to replace them all. ( I would probably go cheap too )

Good luck

They said right to replace all six batteries to improve life of battery system.

But by replacing batteries 1 by 1 after every battery die out then there is no problem also.

Good answer. Cannot add much to that essay other than if there was some way to get ALL the batteries working to their full potential, we might get fewer of them sitting in landfill. Fortunately, lead acid (and ni-cad) are almost all recycled, but lithium Ion batts seem to just end up in the dumpster. Hopefully that will change as the technology matures.

In my battery shop, we charged ni-cad cells in series. The ni cad cells are easy to pull out of the battery. Biggest problem was when we got a battery in which had an over temp during flight. Made the pilots nervous, for darned good reason! We used to titrate the cells to determine if they had gassed (airplanes are hard on batteries!) and we had a locker of bad cells. They never went into reverse charge, but they DID once in a while burn through their plate separators, and go into thermal runaway. I lived through several of those.

I had no problems with the lead acid....they would just sulphate until the dirt in the bottom shorted all the plates. Malory had the contract, and we tossed them aside rather than replace the cells. (I did that once and caught all kinds of shit for that. Likely they didn't like the propane torch melting the tar. Open flames...bad) But once in a while we would get a thermal runaway on "outside shop" batteries brought in by poor privates and corporals trying to get a month or two extra out of their vehicles. No big deal...but they tended to blow up under the load tests. Well, once in a while. I didn't bother too much with those...autopsies are time consuming...but it was an observation that even the nearly bulletproof lead acid batteries had similar problems with the ni-cads.

These minor observations meant to me that the right answer really WAS my Sergeant's answer....replace 'em all. Save problems with acid all over the vehicle down the road.

Nice post, interesting. Thanks.

Golf: "a bad way of spoiling a good walk" - Anon.

Recycle the whole thing. Either that or sell it spares-or-repairs on an internet auction site (name withheld).

As batteries age the internal resistance changes. It increases. The older batteries will drop more of the 36 volt load. This usually means they will over charge. The new battery will be under charged.

In dealing with the repairs of material handling equipment years ago. Some customers would ignore the suggestion of replacing them all to cut cost. They would soon find that it didn't save them money. Because it then comes to replacing them one after the other as they fail. Usually this detrimental to the new batteries and you never get the life out of them.

Unless this bank of batteries is less then six months old replace them all. If unsure of their age. There is a date code.

6... 6 volt battery bank? In series? SPLIT the bank to 2 sets of three (12 volt batt) 36v banks. Each bank of 36 volts. Then put a COLE HERSEE 48070 BATTERY ISOLATOR 3 - STUD 70 AMP 12 / 36 VOLT DC FULLY SEALED between the now 2 - 36volt banks. Charge through the isolator that evens the two banks charge level. Now you have one bank out and one bank back or both together if you want to install some switching (auto or manual). Also, the smaller group 24 12v deep cycle might fit into the old 6v batt boxes. Exchange a few of the 12v batt placements each year when you scrupulously clean the tops of the battery banks before re-watering to get extended life. I do not use AGMs for motoring at all, only for start/run of ICEs.