Any other use for golf-cart charger?

[mm]

I have two 36 volt, 20 amp golf-cart chargers that no one else in town would be interested in repairing. One broke ten years ago, one two weeks ago, and the business which owns them have already bought a new one, and told me I could throw the old ones away.

Do you think it would have any other use for someone who didn't own a golf-cart, like me?

I'm sort of curious what's inside that might be different from any other charger -- it's fancier than my 1 amp and my 10 amp, with circuits to turn it off at full charge, to time how long it charged before that, etc. -- plus I just generally hate to throw things away.

One of them flashes numbers it shouldn't flash, and one was just dead iirc when they plugged it in. I'm thinking this second one might be easier to fix, but it seems to depend on being connected to a set of three car batteries in series to turn on, even when it is working. Maybe I can connect three 12 volt UPS / home-burglar-alarm-backup-batteries and get the same effect, or maybe it will overcharge them if it ever works???

They weigh about 20 pounds each, 8w x 7d x 10h inches and have a handle. Plus it sells for about 600 dollars locally and 300 and up online. A shame to throw it away.

[hrhofmann]

Is there a manufacturer's name anywhere?? Contact the mfgr and ask for a schematic.

[LSMFT]

Boat anchor comes to mind.

[trader4]

Put them up on Ebay. The more disclaimers you put like "flashing error codes and they apparently don't work", the more people will want them. Seriously. Take a look at some of the PCs people bid on that are 5 years old. I saw one where the listing clearly stated that they had never booted it up, have no idea if it works, no software, no returns, sold as is, etc. And people had bid it up already to $75.

[HeyBub]

I'd find an amateur electronics enthuasist (ham radio operator comes to mind) to see if repairs could be made cheaply. If so, sell the suckers on ebay. Current prices there range from $125 to $350.

If you're enough of a salesman, visit your local golf clubs. "Tell ya what I'm gonna do. I'm gonna sell you this charger for $200. You can be confident that if your current charger croaks, you can stay in business and not risk being beaten to death with a 9-iron. Further, I'm gonna throw in a TWO YEAR, MONEY-BACK, UNCONDITIONAL guarantee...."

Under that rubric, the worst that can happen is you break even.

[Jeff Thies]

No. If the batteries aren't the same size or the same level of discharge the strongest battery will take most of the charge. This is similar to memory effect in NiCad. Don't put them in series unless the batteries are even, which is unlikely outside a device that needs three.

The dead one could be easy to fix, it might even be just a fuse. Take it apart and take a look.

As far as usage, probably not much beyond their original intended.

Note that copper, in the transformer, is valuable. Your best bet, as has been suggested, is to try to fix the dead one and then sell them as a pair. Many people could make two out of one, since the symptoms are different.

Jeff

[mm]

A golf club is a good idea. I had hoped to figure out some way *I* could use one, not just sell it to make money, but even if they had given me the golf cart too, I really have no use for it. They own two ministorages and use golf carts to get around. One of them is gas and one battery operated. (The gas one still has a battery to start it, and an alternator, etc.)

Good idea.

Thanks. Thanks Jeff, and thanks everyone.

[Stormin Mormon]

Of course, you could list them on Ebay. As for uses, not much comes to mind. If you try to charge three batteries, they ought to be matched set for age, type, usage, etc. Not really practical.

[clare]

Actually you have it WRONG. Batteries are ALWAYS charged in series

36 volt chargers are becoming uncommon on golf carts, most are 48 and higher today (many even 72) - I use a 36 volt GC charger to charge the 36 volt battery pack for my E-Bike - but even there, 48 volts is much more common on the "good" ones, and 24 on the cheapies.

[Stormin Mormon]

When I READ the paragraph BEFORE your comment, it MADE perfect sense to ME. Charging in SERIES is best done when the batteries are EQUAL in BRAND, type and STATE of CHARGE.

I'd be WILLING to charge BATTERIES in PARALLEL since they all end up at the SAME VOLTAGE.

[jamesgangnc]

If you think a little harder about it, he is correct. A single 12v wet cell battery is comprosed of six 2 volt cells in series.

The conclusion you jumped to was that it's desirable not to charge several independent 6 or 12 volt batteries in series unless they are identical in composition and use. Even then it is a good idea to independently charge each one periodically to try to maintain identical charge states.

[clare]

Think about it - a "battery" is a string of cells in series. Charging batteries in series puts the same amount of current through each battery. Parallel charging is fraught with possibilities. Maintenance charging of warehoused batteries is done with all kinds of batteries, including different voltages and capacities, all connected in series, charging at 2.2 volts per cell, more or less. The precautions you state are mandatory for parallel charging, and almost irrelevent for series charging.

[Jeff Thies]

About what? Surely you are not advocating charging 3 unequally discharged backup batteries? That *is* the point. There is nothing wrong with charging in series provided the batteries are similar and in a similar state. Not that they would blow up, but the charging would be unequal with the weakest battery taking less and less charge after every cycle until it was dead. Hence the advice to discharge completely your NiCads from time to time, so they all start at the same (fully discharged) level. This is all basic ohms law with the voltage divided between all the batteries, the weak link progressively falls in voltage and hence the amount of charge it is given.

For unevenly charged batteries or batteries of different types, the best option is to charge them independently.

FYI, large battery arrays are usually in a series/parallel combo of some type. Look it up yourself.

Jeff

Batteries are ALWAYS charged in series

[Stormin Mormon]

Well, lets see. Now, lets look at the "irrelevant" factors, during a series charge as you seem to prefer.

We start charging. About an hour later, the battery #4 in the line is fully charged. We continue to pump in the two amp charge.

Hour two. Battery #3 is now fully charge. Battery #4 has been over charged for the last hour, and is losing water as it electrolyzes to hydrogen and oxygen.

Hour three. Battery #2 is fully charged. Battery #3 is rapidly losing water. Battery #4 is nearly dry. Candidly, I think you are mistaken.

[Stormin Mormon]

Clare says that with series charging. all those rules and factors are not relevant. Maybe you can help explain it to him?

[Jeff Thies]

Nope. Your explanation was better than any I had in mind!

Jeff

[clare]

You forget, series charging of a string of batteries is NOT constant current. It is constant voltage - and the current looks after itself. And I am NOT mistaken. I worked in the automotive field for many years, and the batteries in the warehouse were allways recharged every couple of months with the old Tungar battery charger - which was set to the proper VOLTAGE for the series string, and after several days of charging all the batteries were fully charged, and evenly charged. If someone miscalculated and set the voltage too high, they were all hot and gassing.

Generally we recharged at 2.3 volts per cell for a day or two, then

2.4 volts for another hour to 3 hours, depending on temperature etc. Hydrometer testing of one or two batteries in the string told when the batteries were fully charged - or simply checking to see that all the cells in a battery were gently and evenly bubbling.

If you charge in parallel and one battery is partly shorted (Low resistance) it hogs all the power and overheats, while the rest of the batteries get virtually nothing - and if the charge is not high enough for that scenario, the bad battery drains all the good ones.

[bud--]

If you have a series string of batteries the current through each battery is not the same - constant current? Please explain.

Charging a set of batteries in series, like a golf cart, you want all the batteries to be the essentially the same - type, amp-hour capacity, aging effects. And they should be used as a series string so their state of charge (as they are used) is about the same for each battery. In an old battery string you shouldn't replace one of the batteries.

Charging over several days is closer to a float charge.

If you charge at significant current you can get what Stormin nicely describes. Why do you think what Stormin describes won't happen.

You probably have batteries that are close to fully charged when you start and what you were doing was closer to a float charge.

If you have a few amps to very different batteries or very different state of charge Stornin has a good description of what will happen.

Evenly bubbling in a series string is an "equalization" charge and is occasionally done in a series string like a UPS.

Partly shorted is a red herring.

You can charge normal batteries in parallel. You are OK if it is at a float charge level (which is close to what you were doing). For a higher voltage (producing a significant charge current) for a timed period, if the state of charge is different or amp hour capacity is different you may lose water in some of the batteries (same as leaving a battery on a charger too long). It is a little safer than series in that batteries that are more discharged will have a higher charge current. In a series string the currents are all the same.

[clare]

The batteries varied from motorcycle and lawn tractor batteries to deisel truck batteries - 6, 8, and 12 volt - AH ratings from 12 to

300+, and cca from about 50 to over 1000.

No it's not. A battery with a lowwer than normal resistance is partly shorted unless it has a VERY LOW resistance, in which case it is shorted. Deteriorated separators or large amounts of sediment in the bottom of the case can cause a "partly shorted" cell - which usually, eventually, becomes a shorted cell.

Which is the general idea. Low charging rate - constant voltage, not constant current.

What is the best battery setup for an electric vehicle (assuming you MUST use lead acid batteries)? A series string of 12 300 ah 6 volt batteries for 72 volts, or a set of 12 300 ah 12 volt batteries set up Series/Parallell? And what is virtually "required" in order to successfully use the 12 volt batteries?

To use the 12 volt batteries you need to have equal length, equal resistance cables connecting the individual batteries in parrallel pairs - and then also connecting the parrallel pairs in series so you essentually have a ballanced grid tying all the batteries together - (and the batteries pretty well have to be identical - down to being dfrom the same production run and date code). that way a bad cell will only kill 2 batteries - the defective one and the one directly parallled with it. In a series string, even in a high load situation like an EV, the batteries should be of the same nominal capacity as far as AH and CCA rating, but are not NEARLY as sensitive as in a parallel situation.

Unlike you guys, I have built and driven electric vehicles. I've "done it" - and belive me, series works a LOT better than parallel.

[clare]

If you want an "authorative" answer look at

half way down the first section it discusses series and parallel connections - And a series connection with a failed cell has reduced power - or it quits. A parallel cell with a bad cell has reduced power or it overheats - and possibly burns.