Estimated time for charging

Uncorruptable

Hi,

I need to charge a couple of 12v batteries like the one below,



I cant afford to buy a charger with LED saying when it is full but i do have a 12v car battery charger, how long would you reckon i should have them on charge individually safely to charge if the charger is running at about 3 amps?

Also, is it safe to run charging cables to both when not in series from the charger? I am assuming the charger will just supply them both as 1 12v battery, no?

Bruthal

Uncorruptable wrote: »

Hi,

I need to charge a couple of 12v batteries like the one below,



I cant afford to buy a charger with LED saying when it is full but i do have a 12v car battery charger, how long would you reckon i should have them on charge individually safely to charge if the charger is running at about 3 amps?

Also, is it safe to run charging cables to both when not in series from the charger? I am assuming the charger will just supply them both as 1 12v battery, no?

The charging current for such batteries would usually be 1/10c at most, which means the amp hours Capacity of the battery divided by 10, and so charging time would be 10 hours or slightly more.

If the battery is 12 ampere hours capacity, then it should be charged at no more than 1.2 amps, or about 1 amp for 12 hours.

If you were to parallel 2 or more, this can be added together to 3 amps to charge 3 etc. But thats not recommended if you are not able to ensure each battery is discharged to the same level before starting, and its recommended to charge one at a time.

Uncorruptable

robbie7730 wrote: »

The charging current for such batteries would usually be 1/10c at most, which means the amp hours Capacity of the battery divided by 10, and so charging time would be 10 hours or slightly more.

If the battery is 12 ampere hours capacity, then it should be charged at no more than 1.2 amps, or about 1 amp for 12 hours.

If you were to parallel 2 or more, this can be added together to 3 amps to charge 3 etc. But thats not recommended if you are not able to ensure each battery is discharged to the same level before starting, and its recommended to charge one at a time.

Hi Robbie,

Thanks for the info, thats very useful, there shouldnt be an iissue with the batteries being discharged the same amount, they are being used in an electric scooter in series to make 24vdc so they would be run down the same all the time, just that a charger for the scooter is €70 odd euro to buy with LED cut out indicator walk in & about €40 online before shipping charge.

I will take the batteries off series & feed the two from my car battery charger according to your guide above, then i will put them back in series to run in the escooter.

Thanks for the info.

Bruthal

Uncorruptable wrote: »

Hi Robbie,

Thanks for the info, thats very useful, there shouldnt be an iissue with the batteries being discharged the same amount, they are being used in an electric scooter in series to make 24vdc so they would be run down the same all the time, just that a charger for the scooter is €70 odd euro to buy with LED cut out indicator walk in & about €40 online before shipping charge.

I will take the batteries off series & feed the two from my car battery charger according to your guide above, then i will put them back in series to run in the escooter.

Thanks for the info.

When they are in series, they can discharge to different levels. But they should be ok to parallel for charging. If they are indeed 12 AH each, charging both together at 2 amps will charge them in 12 hours. Keep it at 2 amps though and not much higher.

Uncorruptable

Will do, thanks again.

Uncorruptable

Ok, just want to be sure before i do anything, i have modified the battery charger to have two cables feeding from both the positive & negative & colour coded brown & blue so there is no confusion when plugging them in each time, i also have plug in connectors crimped onto the ends of each cable.

When i read the info on the batteries i didnt want to put it on charge until i was sure it was ok & check back here,

Batteries are 12v & 12AH as you said they would be,



but there was additional info on them, have a look here,



What are the three lines telling me?

Tow

Stand By Use: The voltage charge them continuously at. When used in a 'Stand By' situation eg Emergency lighting, Alarm backup battery, UPS etc.

Cycle Use: The voltage to charge them at when charged and then run down. They will charge faster, but damage the battery if left charging too long. eg when used in a toy car.

Initial Current: Don't let the current they draw when charging exceed this value. When flat a battery can draw a lot of current, if the charger can supply it/does not restrict it. As the batteries charge the current will reduce until fully charged. Again exceeding this value will damage the battery.

Bruthal

Yea the initial current max is the max current they can take when fully discharged. It will reduce as the batteries charge up.

Id keep it down at 2 amps or below myself. Good chargers have a constant current for the first part of the charge cycle, and they increase the charging voltage a little as the battery charges, to maintain a constant charge current. As the battery nears full charge, they change to constant voltage so the charge current reduces until the charger senses the charge is full by cutting of at a certain low current amount, and so charging stops.

For the other types, start it off at 2 amps and see how that works time wise. Starting at 3.5 amps and the charge current will probably quickly reduce anyway.

Uncorruptable

Sorry for the late reply, the charger has a normal & fast setting on it, so i will set it to normal, plug in the connectors to the battery then plug in the charger & monitor the ampage it is drawing.

Cheers for the help.

Eóin.

Uncorruptable

Got the charger wires all pared & soldered on the double cables, installed male & female plugs on the wiring in necessary locations, plugged in the charger & its only running at a half an amp:(

Looks like it will have to be a 24 hour charge or shell out abot €60, think i will stick with the 24 hour charge.

Bruthal

Uncorruptable wrote: »

Got the charger wires all pared & soldered on the double cables, installed male & female plugs on the wiring in necessary locations, plugged in the charger & its only running at a half an amp:(

Looks like it will have to be a 24 hour charge or shell out abot €60, think i will stick with the 24 hour charge.

Are you sure the batteries were discharged? It will be a lower charging current if they are partly charged already.

Half an amp will only be a quarter amp into each battery and so would be a 48 hour charge if that was the case. A car battery charger should run higher than that if charging discharged batteries.

Did you try each battery on its own to see charge current?

Uncorruptable

robbie7730 wrote: »

Are you sure the batteries were discharged? It will be a lower charging current if they are partly charged already.

Half an amp will only be a quarter amp into each battery and so would be a 48 hour charge if that was the case. A car battery charger should run higher than that if charging discharged batteries.

Did you try each battery on its own to see charge current?

Definetly discharged, turn the key on & only a bare reading on the power level indicator on the handle bars & when you try & turn a light on nothing, only had enough power to barley light the indicator very weakly.

When the same charger was hooked to my car battery the amp meter shot up to between 2-3 amps, i will leave it charge over the day & have a look what registers on the Power level indicator on the unit itself.

I was a little surprised that it was so low i have to admit when i put it on last night, it did appear to be climbing slowly over the course of three hour until i shut it off for the night, i will have a look now & see what the ampage is running at & see if it has increased at all.

Perhaps i should double check my soldering of the cables coming from the charger, looked fine last night but perhaps they have snapped away or come loose.

Bruthal

Uncorruptable wrote: »

Definetly discharged, turn the key on & only a bare reading on the power level indicator on the handle bars & when you try & turn a light on nothing, only had enough power to barley light the indicator very weakly.

When the same charger was hooked to my car battery the amp meter shot up to between 2-3 amps, i will leave it charge over the day & have a look what registers on the Power level indicator on the unit itself.

I was a little surprised that it was so low i have to admit when i put it on last night, it did appear to be climbing slowly over the course of three hour until i shut it off for the night, i will have a look now & see what the ampage is running at & see if it has increased at all.

Perhaps i should double check my soldering of the cables coming from the charger, looked fine last night but perhaps they have snapped away or come loose.

Higher capacity batteries can accept a higher charge current at a given charge state anyway, but would expect it to be more dependent on the actual charger output voltage, so it might be slow charging these batteries if its just a fixed rate charger. Connecting your 2 in parallel makes it the same as a 12v 24 AH battery though, so you would expect some sort of decent charge if they are completely discharged.

How long since they were last charged? Maybe they are past their best. See how charging for the day goes.

Uncorruptable

robbie7730 wrote: »

Higher capacity batteries can accept a higher charge current at a given charge state anyway, but would expect it to be more dependent on the actual charger output voltage, so it might be slow charging these batteries if its just a fixed rate charger. Connecting your 2 in parallel makes it the same as a 12v 24 AH battery though, so you would expect some sort of decent charge if they are completely discharged.

How long since they were last charged? Maybe they are past their best. See how charging for the day goes.

It was a good while since they were charges alright, thing is, the amp meter started off at half an amp & has slowly crept up to just under 1 amp now.