Battery Charging Voltage

Also charging and discharging is done simultaneously. Flow is like this:

Wall AC 220V---->Battery Charger----->4 x Battery 12V Connected in Series---->48V DC motor.

Hello Guest,

You don't advise what the specific type of lead-acid battery you are using, thus my advice is general.

The charge into a lead-acid battery is normally ¹⁴/₁₀ of the battery rating.

Example: 40 Amp hour battery = 10 hour discharge at 4 Amps, thus would need charging for 14 hours at 4 Amps.

The charging voltage needed to maintain the charge of 4 Amps into the 48 Volt battery will need to start at 56.8 volts (4 x 14.2 Volts) and as the acid conductivity (electrolyte Specific Gravity) increases as the cells are charged, the applied charging voltage normally will need to be reduced gradually, to prevent overcharging of your 48 Volt battery.

Do not make the error of using a simple 12 Volt charger to charge each 12 Volt battery separately, then when all are charged use them in series to obtain your required 48 Volt DC supply.

Car type lead-acid batteries normally show 13.6 volts across the battery terminals, after being removed from the charger for 1 hour (to allow all bubbles to rise out of solution).

The best type of charger for your 48 Volt battery is one like: Soneil Chargers 48 Volt 4808SRF 3.5Amp CC Dual Voltage Input 115/230VAC from: http://www.cloudelectric.com/inc/sdetail/785

This microprocessor type of charger (There are many different brands of microprocessor controlled charger which should do the job for you) may be permanently connected to your battery, and will never overcharge it once correctly set for your type of 48 Volt battery.

Kind Regards....

Thanks Sparkstation for the advice and this helps a lot.

I looked at the soneil datasheet for the suggested model. It says that charger at 48V, 3.5A whereas you suggested to charge start at 56.8V. Please let us know how this works.

By scaning thru some of the data found that initial 90% to be charged at 14.2V and later switch to 13.6V to charge remaining which would be slow. Can you suggest on this if this is required to follow for my kind of system.

Thanks

related question:

Since I'm connecting charging wires and discharge wires to same terminals of battery, how do we ensure that battery is getting charged properly. Since my DC Motor is functioning properly from battery, I know that discharge from battery is correct. Whereas I'm not sure about charging if it's done properly. While checking terminal voltage on that battery, since both (charge and discharge) connected to same terminals unable to figure-out what's happening? Any advice please.

Thanks

Hello again, Guest,

The charging voltage does not matter on this type of Battery Charger, because the microprocessor has been programmed with charging algorithms (the computer equivalent of a proper charging curve for the battery) - thus the battery is always charged at the most effective rate.

I personally use a 6/12/24 Volt microprocesser battery charger (of a different make), and the use of that charger has enabled recovery of batteries which were unable to be properly charged with the older type of charger.

When the charger is connected and switched on, the open circuit (unconnected to the battery) voltage is somewhat higher than the voltage rise when the charger is connected and switched on - this variation is easily seen on a Voltmeter.

Is your motor installation a mobile one?

If not, leave the microprocessor charger connected permanently, and it will maintain your battery at best condition automatically.

Charging rates for car type lead-acid batteries are normally 14.2 Volts, and may go up to 14.7 Volts (When connected to the 12 Volt battery terminals) but the actual Voltage is relatively unimportant, Charging Current in Amps is what the charging (or not) is all about.

As I stated earlier, if you use 4 x 12 Volt batteries in Series to provide 48 Volt supply for a motor, then it is very important to charge those same batteries as a Series unit, with a (nominal) 48 Volt charger.

If you charge those 12 V batteries separately, then connect in series to provide a 48 V supply, you can never guarantee that all cells have exactly the same charge, one will be less than the others, and that cell will over time, overheat slowly, have a higher internal resistance, and thus fail first, instead of the normal situation in a series circuit where all cells fail at nearly the same time.

I include below, the scanned Instructions for a typical Microprocessor controlled battery charger (The one I use) - Note the graphs showing the charge voltage over time

Trust that explains the situation for you.

Kind Regards....

Hi Sparky,

The charger you indicated is a neat little unit, I had one presented to me for repair but could not detect where problem was after checking all the usual items. I was wondering if you have run across a circuit diagram for for this model have run a net check with no luck.

Regards Garth.

Hello garth

Unfortunately I could not locate the actual Makers of the charger above, having spent a couple of fruitless hours trying for you.

They are "somewhere in China" according to the New Zealand importers, that's all I was told.

I do not have a circuit either, and trust that my unit will give many years of faithful service to me.

However, the NZ importers are receiving another phone call from me tomorrow, asking for Maker's website and/or email address, in case I ever need to repair the unit.

If/when I locate the information, I shall advise further in this thread.

Kind Regards....

The OP states in post #1 that he is charging/discharging at the same time, it seems that may confuse a "smart" charger?

Tom