i have a problem with my daughters 24v ebike.

What i want to do is charge 2 12v battery(series so 24v) using the stock charger of the ebike. Charger is input: AC 90-240v 50-60hz output: DC 24v 1.6a-2.0a. Battery is 12v 9ah 20hr. I uploaded the picture of the charger and the battery. Will it be possible to charge using the 24v charger?

Thank you

 

Welcome to AAC!

It's never a good idea to charge batteries in series if they're not matched. The weaker battery will spend more time in overcharge and get cooked; further weakening it until it dies.

There's nothing you can do about the 6 series cells in the battery itself. They started out as matched as was economically feasible for the manufacturer. Eventually one cell will become significantly weaker than the rest and the battery's demise will accelerate.

 

If it's an actual charger for a 24 volt battery system (puts out an actual 28 - 29 VDC) then yes it will work fine assuming both batteries are matched set.

 

It looks like that 'wall wort' power supply puts out 24 VDC. 24 volts is not enough to charge two series connected 12 volt lead acid batteries. You really need 28 - 30 volts to get a full charge in that configuration. But I'll also echo others in that if you can charge each battery seperately, you are better off.

 

Boats & trucks with 24 volt systems charge 2 12 volt batteries in series with a 24 volt alternator.

Golf carts have 6 or more batteries all charged in series. Mixing old with new with different brands never mattered. Good ones were all within a few tenths of a volt of each other.

 

Your battery charger says 24 volts with a 1.6 to 2 amp load on it.

I would bet that open circuit voltage with no load it will put out about 27 volts. When the batteries are fully charged, there will be almost no load and the batteries / charger will end up around 26 volts.

 

Boats & trucks with 24 volt systems charge 2 12 volt batteries in series with a 24 volt alternator.

There are chargers that charge 2-4 NiMH batteries in series too. Does that mean it's a recommended way to charge batteries and maximize capacity/lifetime? No. Is it convenient? Yes.

The weak cell will charge first and it will be baked while the stronger cells continue charging. If those cells are used in series, the weak cell will be depleted first and will be reverse charged by the stronger cells. That will accelerate the demise of the weak cell.

For some battery chemistries (i.e. NiCd), a reverse charge of 0.2V is sufficient to cause it to short.

Golf carts have 6 or more batteries all charged in series. Mixing old with new with different brands never mattered. Good ones were all within a few tenths of a volt of each other.

Excerpt from Battery University article:
http://batteryuniversity.com/learn/article/bu_803a_cell_mismatch_balancing

 

I was a boat mechanic at marinas for 20 years. I had my tool chest mounted on a golf cart. I used it every day to go to jobs, when I needed parts at the ship's store and hauling heavy parts to the boats. Because 3 batteries were under my tool box, they seldom got the water checked. I probably had to replace one battery per year. I see the average price of 6 volt batteries is about $100.00. What do you think my employer would say if I told him I needed to replace $500.00 worth of good batteries to keep it a matched set?

 

What do you think my employer would say if I told him I needed to replace $500.00 worth of good batteries to keep it a matched set?

What does that have to do with the proper use of batteries?

 

12V batteries need ideally 13.8V each, that's 27.6V for two cells.

 

Your battery charger says 24 volts with a 1.6 to 2 amp load on it.

I would bet that open circuit voltage with no load it will put out about 27 volts. When the batteries are fully charged, there will be almost no load and the batteries / charger will end up around 26 volts.

So sir i cant use my stock 24vcharger to charge my 2 12v battery in series?

 

12V batteries need ideally 13.8V each, that's 27.6V for two cells.

I dont have any idea about electonics. I just want to know sir if my charger can charge my 12v batteries in series.

 

I dont have any idea about electonics. I just want to know sir if my charger can charge my 12v batteries in series.

Try it and see what voltage they go up to. If its more than 24 volts then yes it will work.

 

So sir i cant use my stock 24vcharger to charge my 2 12v battery in series?

Read and understand the information I posted in post #7.

If you charge two batteries in series, end of life for the weaker battery will be accelerated. The stronger battery could also die prematurely because it might not get a full charge.

When charging or using batteries in series, the batteries need to be matched. Mismatches will cause problems.

Trying to charge in series is convenient. Having to buy replacement batteries sooner because you abused them is dumb.

The "advice" given for the golf cart example was penny wise, pound foolish.

 

What i want to do is charge 2 12v battery(series so 24v) using the stock charger of the ebike.

I get the impression that the "stock charger" came with the ebike. If so, why are you concerned?

 

I get the impression that the "stock charger" came with the ebike. If so, why are you concerned?

The original battery of the ebike is one 24v batt and it was confiscated in my check in baggage in the airport. Due to less availability of 24v battery here in the Philippines I changed it to 2 similar 12v battery.

 

I changed it to 2 similar 12v battery

Just make sure the batteries are the same relative condition and amp hour capacity.

When you replace them, do them both at the same time. AFAIK, that recommendation is given for all things that use multiple batteries. If you don't, the weak battery is the weakest link.

For 2 series 12V lead acid batteries, it's better to charge them separately. That's not as convenient as charging in series, but the batteries will last longer. If you use some smart charger that uses charging current as a charge state indication, the stronger battery might not get fully charged. In lead acid, that causes sulfation.

Having 6 cells in series is bad enough, increasing to 12 decreases reliability; unless you're a battery manufacturer or have stock in a company that makes them.

 

Just make sure the batteries are the same relative condition and amp hour capacity.

I changed it to 2 similar 12v battery.

Yes. Go ahead and use the stock charger and don't worry about it.

 

If you are simply replacing a 24 volt battery with 2 12 volt batteries, and the batteries are reasonably well matched (same manufacturer, size, ratings, ideally same date code), then you are good to go. If that was the original charger, it will work just as well charging 2 12 volt batteries in series as it did charging the 24 volt battery. Don't worry, be happy.

 

Also make sure the battery capacity is the same as the single 24V battery. The charger is wimpy and is unlikely sophisticated enough to charge the batteries correctly.

Most manufacturers who use batteries don't care if they don't charge them correctly. They consider it a consumable and will likely exclude it from their standard warranty. Battery manufacturers only care if you're trying to make a claim on their warranty. If you haven't charged the batteries properly, they have a way to weasel out of their warranty.