# How to charge a 48V battery (12V battery * 4 in series connection) with a 12V charger?

I found a question about charging the battery with a 12 volt charger. However I’m confused as to do this?

First method, unhooking and charging each battery individually? But wouldn’t I be just shorting a battery out if I tried charging one at a time while they are still wired in series. Would charging the whole series only yield a 12 volt charge on the series? I was thinking of just buying a proper 48 volt charger

• There are 3 answers on the question that you link to that tell you what you should do . – Solar Mike Sep 9 '18 at 6:16
• So there’s no way of doing it proper with a single 12volt charger is that what I’m understanding? from the 3 answers?so either 2 24 volt chargers four 12 volt chargers or a single 48 volt charger ? – Gerald Leese Sep 9 '18 at 6:19

The easy (and proper?) way to charge a 48 volt battery bank is to use a 48 volt charger.

If you only have a 12 volt charger, you can charge the individual 12 volt batteries one-at-a-time without rewiring anything - your charger's negative terminal should not be connected to "Ground".

You could also use four separate 12 volt chargers, each one charging one of the four 12 volt batteries making up the 48 volt bank, as long as the outputs of the chargers are not connected to each other except at the batteries.

• I wonder what the cost of a 48v charger is compared to the total cost of 4 12v chargers, and then how easily 48v chargers are available compared to 12v chargers (any car parts store has 12v chargers...) – Solar Mike Sep 9 '18 at 6:27
• Do you know if I can pull the reading of each cell with a multimeter without disconnecting them? or am I gonna zap myself? I read that having them all at the same level is important – Gerald Leese Sep 9 '18 at 6:30
• I’m also curious what the differenceon hydro would be – Gerald Leese Sep 9 '18 at 6:30
• A 12 volt lead-acid battery consists of six cells connected in series - it is generally not possible (in batteries I've used) to connect to individual cells. For flooded cells (liquid electrolyte that you can "top up" with distilled water as needed), you can do an "equalizing charge" to ensure that all cells are fully charged and balanced - this procedure will result in much gassing of the electrolyte, requiring adding water to compensate for the water lost. This procedure MUST NOT be done on Gell Cells or AGM batteries, and preferably not on "maintenance-resistant" flooded batteries. – Peter Bennett Sep 9 '18 at 6:48
• You ought to buy a specify gravity float acid tester and measure each cell to record the readings after a full charge. This way you can satisfy your doubt of each battery perfect balance. If one cell is low in s.g. then you can expect the entire string to be as strong as this weakest cell. The s.g. is an indicator of both the kilofarad capacitance or Amp-hr capacity and series R or ESR from sulphation coating on the plates. Pulse charger addons help clean the plates when the charger is on activated by 13.5V with 100W 1us pulses that only draw a watt average power during float charging. – Sunnyskyguy EE75 Sep 9 '18 at 7:11

"If you only have a 12 volt charger, you can charge the individual 12 volt batteries one-at-a-time without rewiring anything - your charger's negative terminal should not be connected to "Ground"."

Note 1: The above statement is correct, however, I would strongly advice to disconnect batteries from each other before charging the 12V battery with a 12V charger. This helps with efficiency of charging.

Note 2: Even though a 48V system is normally charged with a 48V charger it is not the efficient way to charge. If you can use individual chargers per battery and able to disconnect batteries form each other before charging this is the best way to properly charge the batteries instead of charging them as a battery bank. But for practical purposes, if the battery bank is charged as a bank then use the manufacturer recommended equalization charging to bring each battery voltage back to nominal voltage at recommended interval. This process will ensure the individual batteries carry the load equally and will reduce internal resistance from developing and building and damaging the bank eventually. Remember it only takes a cell or a single battery to damage the whole battery bank performance.