Parallel Charge/Series Discharge of Batteries Using Modified Quadrupler

........Why?.........

For a start, batteries don't work well when you try and charge them with half wave rectified AC. The circuit is specifically designed for AC, not DC.

What on earth are you trying to accomplish?

Golf cart batteries are series connected,and series charged.

The problem is getting an exact balanced charge on all batteries when in series.

In parallel charging,all batteries will get same charge.

I intended to extend the circuit to 6 batteries each,and apply A/C to the input,not DC.

I could also put a capacitor across the battery connections to reduce the 30 cycle ripple somewhat.

I realize it will require some trial and error to get the right voltage for the desired charge state.

I have one "Yes" and one "No" to this question so far.

Yes but why, what's the application exactly?

Lets take a step back for a minute. Application, output current and voltage, battery type, etc.

Better we find out now and offer a solution that will work for your application than you experimenting with the circuit with expensive batteries and destroying them by using half wave rectified 60Hz alternating current with what appears to be no current limiting electronics to protect the batteries (you have not mentioned this). You will just kill the batteries trying to charge them with AC.

The application is to charge golf cart batteries in parallel,to insure equal charge

voltage on all batteries,and discharge them in series to provide the higher voltage for

the cart drive motor.(Either 36 volt(EZ GO) or 48 volt (Club Car))

All golf cart chargers charge the batteries in series,which can lead to unbalanced

charging of some of the batteries.

I am sure I am barking up the wrong tree,someone surely has tried this before

without success.

I know it can be done with relays,but I was trying to keep it solid state and simple if possible.

If you aren't happy with your existing charger my simple solution would be rewire the series battery connection to allow quick disconnection so you can separate the individual batteries and charge them individually with a decent charger. That's what I would do. In addition I think this question has been asked before on CR4, so try the site search function also.

Trying to use an alternating current Cockcroft-Walton voltage multiplier circuit (or similar) to charge golf cart batteries is just plain madness.

Battery charging is a process to restore the free electrons available on the plates.

If you charge the batteries in parallel the amount/quantity of current (electrons) each battery absorbs will be dependent on battery impedance and/or charge state.

Charging current in a series circuit is the same through each battery throughout all batteries in the circuit.

Charging in series will equalize all healthy batteries to the same voltage level.

If a battery in the circuit is suffering from lead-oxide plating or electrolyte degradation there is a much better chance of reviving the battery by charging it in series with other batteries.

The only improvement over charging batteries connected in series is to charge each battery individually.

The applied battery charging voltage needs to be as "steady-state" (smooth) as possible and applying half-wave voltage to any battery will damage the battery sooner or later.

OP said AC not half wave rectified...

Otherwise agree.

Cockcroft-Walton voltage multiplier circuits (or similar) use capacitors and diodes and the original plan by HiTekRedNek was to replace the capacitors with golf cart batteries, not just connect the batteries to the output of such a circuit. Series diodes and AC would give the half wave rectified waveform I mentioned.

False Premise Alert! "...In parallel charging,all batteries will get same charge...", not quite, they will all see the same charging voltage, but that does not guarantee that they accept the same charging current, that will depend upon the exact SOC (State of Charge) of each individual cell.

The only way you can guarantee equal SOC at the end of the cycle is to use an automatic equalizing system that boosts the charge voltage on the string, monitors each cell's SG (specific gravity), and cuts off the cell's voltage when the SG reaches the right value. Effective, but expensive to say the least.

I am aware that they will only get the same charge voltage in parallel,but it is better

than in series,where the voltages can vary from battery to battery in the string.

I have thought of making a by pass circuit with zener for each battery to bypass it

when it reaches the desired voltage, and shunting it to the next battery downstream,

and this may be the way to go.

It is true that the best way to to charge them individually,but this is too labor

intensive with multiple carts, like on a golf course.

Of course,your suggestion would be a more precise method ,and might be justified in

a large array,such a a solar farm, communications central office,etc.,but not for this

application.

Wait, what?

How many golf carts are we talking here? Is this a commercial venture? It sounds like you are trying to reinvent the wheel here.

What about investing in a better charger and using better batteries or battery balancing circuitry to assist in preventing individual battery overcharging / early detection of failing batteries?

Not a commercial venture.

There are 6 golf carts in my local "village" of relatives,and each has 6 batteries.

They are used for getting around in the neighborhood.

Some are 8 volt,some are 6 volt.

They rely on me for maintenance,and repairs.

They are all retired,and on fixed income.

I only charge for parts at cost.

So a set of batteries is a great expense for most of them.($600+).

I am simply trying to extend the life of the batteries as much as possible.

Now, you have two why's.

Just get a good battery tender.

Or, maybe a solar panel on the roof.

I am guessing you are talking about something like charging them on 12 volts and discharging them as a 48 volt set.

If so yes it would work as long as the batteries are all of similar size and working conditions.

Ah, your thinking connect up batteries in series to get a higher voltage - No he's actually talking about the following kHz range ac charging circuit and replacing the capacitors with batteries and the kHz range transformer with a 60Hz transformer and charging the batteries in the circuit with AC.

http://en.wikipedia.org/wiki/Voltage_multiplier

Now what do you think.

I think that when no schematic is provided there are too many grey areas in how people could describe an electronic circuit.

So yes if he is referring to a charge pump type voltage multiplier then no it will not charge the batteries.

Now if I was to be really fussy about charging a battery bank to get uniform charge in a multi battery setup I would either use a small dedicated charger for each battery or a switched relay system that cycles one charger through all the batteries one at a time in a predetermined charging time cycle.

But being I am not that fussy I would use the regular charger and occasionally do independant battery top off with a separate charger one battery at a time when ever I added water or did some other sort of battery maintenance.

Simply put, no.

https://www.google.co.nz/#q=voltage+multiplier+operation

As an experiment try it out with some small AA batteries and see for yourself (with safety glasses and a fire extinguisher handy just in case). Doesn't really matter if they are rechargeable or not. Let us know what you discover please.

This is an interesting paper that describes improvements in charge acceptance using pulses of high charging current and short discharge pulses (a little further in the paper). Perhaps beyond a convenient set up, there could be benefits to cycle life and charge acceptance.

.

https://www.google.com/url?sa=t&source=web&rct=j&ei=MhZIVaSHH8W_ggT3w4CwCw&url=http://www.ipenz.org.nz/ipenz/publications/transactions/Transactions98/emch/2wilkinson.PDF&ved=0CBwQFjAA&usg=AFQjCNH3V8mMRIS7aFH0V-i9IkOmaQmyDw&sig2=mt1kk-n4693Y76jR5MK-wQ

Bad link?...does not work.

Probably my phones browser causing issues. Search" www.ipenz.org.nz>transaction>emch new pulse charging methodology for lead acid batteries "

That link works.

Very interesting.

Thanks!

The key word...."equalize".

Buy 3 or 4 10V 100VA transformers and add a full rectification circuit to each of them. The O/P voltages wil now be floating. Connect circuit 1 to battery 1, circuit 2 to battery 2, as the voltages are floating the 0V of the second battery will actually now be the charge level of the 1st battery but will still have full charge voltage accross the terminals. Each battery will have the charge Voltage relevant to its discharged Voltage and condition. The other batteries will stop charging when they reach full charge and the slower ones will stay on charge. 3 to 3, 4 to 4. Eatch battery will have its own 10 volt 10 Amp charger and the battery that charge faster than the other will lift the charging voltage accross the slow chargers and increase the charging current accross the slower ones. The safety in this circuit is that charging voltage can never exceed 14.5 V. If you are energetic you can add regulated circuits. I build one of these for a friend with 9V transformers but could never reach full charge as max voltage of 9 Volt is 13.5 volt and Lead Acid need 13.8 to 14.2 max . Natrium is 14V to 14.8V max. I added regulation to the one I made. Just remember that the 0Volt of the regulator must be connected to the Negatve O/P connection clip wire.

I rather expect that the 6 batteries in each vehicle will never be all equal capacity as they would have been replaced at various times when one or more falls over, Unless the owner likes replacing all 6 at once.

I would do it the simple way wire in 6 charging points and use 6 chargers with auto charge and trickle program. Why make life difficult?

I have a small electric car which uses 6 golf cart batteries and I agravate the situation by using it in parades on on 2 of the batteries loaded for 12 volts so I can go slow enough and have more control. The batteries of course do get out of balance. I do the balancing manually by simply taking readings with a cheap Harbor Freight volt meter and balance them using a fully rectified output of a Variac. It doesn't take long to get the experience of how to adjust the Variac and how long to leave it to get the batteries in balance. The trick is not to start from discharged with the Variac. I use the series charger until the highest battery reaches it's proper charged voltage and then "top off" the low cells without disconnecting the batteries. If the batteries on a golf cart are way off, the low units are probably close to failure. They should be close and only require a little "topping" to even them out. Many golf courses use this method of protecting batteries and it works but does require a little experience to get the timing correct.

The local golf course has solved this problem...multiple carts = multiple chargers!

But each cart only hooks up to one charger at a time, HTRN is looking at 'speed-charging' a single golf cart by charging the individual batteries in the bank in parallel.

It seems like a good idea in theory, the batteries each get the individual attention from the charger, and weak or dying batteries can be more quickly identified as opposed to trying to determine if the 'general bank degradation' is due to 'normal wear and tead' across all batteries, or one bad battery 'hiding in the crowd.' The down side is cost, the added complexity would ramp up the 'base cost' of the golf cart, and for one or two it would be a good investment, retrofitting an entire fleet, or redesigning the model line, might be more money than a fleet owner / manufacturer may be willing to spend, as the ROI may not justify it.

After considering all of the feedback from the valuable answers,I must reconsider my options.

Although the idea of parallel charging has some advantages,so does series charging,as pointed out by others.

A group of relays could do the job,but that is too expensive and impractical.

A bypass circuit,triggered by an appropriate zener diode would take a fully charged battery out of the circuit,and pass it on to the next one in line.

This would prevent overcharging in the event of a weak battery in the string.

Does anyone see a "fly in the ointment" with this method?

I sincerely appreciate the feedback from everyone.

"A bypass circuit,triggered by an appropriate zener diode would take a fully charged battery out of the circuit,and pass it on to the next one in line."

No it won't.

First problem is that the charger is providing the charge voltage which will be divided relatively evenly among all cells.

Consider a 6 cell 12v battery under charge at 14.4v. That 14.4v will be distributed across all cells giving 2.4v per cell. This is an artificial cell voltage because, if you remove the charger the cell voltage will drop as the chemistry absorbs the charge into the plates. A zener diode, or any other voltage sensing device, must be able to differentiate between artificial and real long term cell voltage.

Below is a typical charge curve for a lead acid battery under charge. You can see that the battery has reached its full charge voltage long before the battery is fully charged. Even if the charger is removed during the last 50% of the charge cycle, the battery will show a full charge voltage for some time due to surface charge.

Surface charge during charging is due to the fact that the chemical reaction that draws the acid out of the lead plates and back into solution can only take place on the surface of the plates, and so that surface has a higher concentration of ions which, while raising the cell voltage, is quickly depleted if a load is applied. It takes time for the entire chemical reaction of charging to reset the chemistry of the cell.

These new aluminum ion batteries may be a game changer....low cost, 7500 cycles, short charge time <1 min....however energy density is only about half that of lithium ion batteries, but what it lacks in energy density it more than makes up for in cost and longevity and speed of charge and discharge....

http://blogs.scientificamerican.com/plugged-in/2015/04/14/stanford-researchers-unveil-new-ultrafast-charging-aluminum-ion-battery/

http://www.nature.com/nature/journal/v520/n7547/full/nature14340.html

Interesting. If this comes to market without major revisions to these preliminary characterizations, it will a great fit for residential battery backup.

.

One article you linked repeatedly noted that this techno would not end up in electric cars. While an energy density only 1/4 of lithium ion, their reasoning is clear.

However, with a power density 10 times greater than lithium ion and the ability to accept a charge in such a short time, these batteries might show up in electric vehicles. Probably not as he sole type of battery, but rather a potion of the total capacity that can accept charge quickly enough to make use of regeneration from more rapid braking.

OK I will bite on this conversation, all be it late to the game. I have two carts and two chargers one an old Lester dumb charger and one Lester smart charger. I have not had any problems with either one and both battery sets are only one year apart. The oldest set is almost 6 years old and are just now starting to get harder to fully charge overnite. I will try to equalize them again this weekend, they are on the smart charger. I equalize them by using my 12V charger that can equalize them as a pair, and do them one pair at a time.Then I re-pair them and equalize them again to check for any units out of sync on voltage and specific gravity on the acid. The way I have done them has served me well without any replaced batteries. The set on the dumb charger have been flying high without any issues as I equalize them every year as well just the same as the smart charger. This fall when I bring both carts home I am going to out fit one of them with solar panels, 9 -15 watt panels set in strings of three for 45 watts. I will see if that helps the charging situation as we only have one outlet for both carts which means only one gets charged each nite. I don't see any reason for a Rube Goldberg approach to charge batteries this way, and believe me I have tried a few different ways to charge these types of batteries and I have not found anything that works as well as the bulk chargers and an equalization charge from time to time. Check with me next summer and I will let you know if the solar panels helped.