charging 12v battery banks wired in series

the_grube

the_grube

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Curious what others are doing;
  1. charging each battery individually with the serial connection(s) in place
  2. same as above but removing the serial connection(s)
  3. using a single higher voltage charger.
I have 2 LifePo4 100ah units that were bought at the same time. I was doing #1 above based on some internet research, but had a situation where the NOCO charger bank on one of the batteries threw a polarity reversed signal until I broke the serial connection. My theory is that battery lost so much charge that the current tried taking the path across the serial wire rather than into that battery and that bringing both batteries up to full charge individually will allow me to go back to #1...
 
the_grube said:
Curious what others are doing;
  1. charging each battery individually with the serial connection(s) in place
  2. same as above but removing the serial connection(s)
  3. using a single higher voltage charger.
I have 2 LifePo4 100ah units that were bought at the same time. I was doing #1 above based on some internet research, but had a situation where the NOCO charger bank on one of the batteries threw a polarity reversed signal until I broke the serial connection. My theory is that battery lost so much charge that the current tried taking the path across the serial wire rather than into that battery and that bringing both batteries up to full charge individually will allow me to go back to #1...
Click to expand...
So...are you using a 24 volt charger?
 
If my boat wasn't under a cover, I'd take a photo.

I use the NOCO charger for my 3 bank in series system. But you have to disconnect the series before charging. So my solution was to add these quick disconnect knobs so that I can just quickly unscrew the connection before plugging in the charger, Much easier than disconnecting the charger each time I want to use it.

 
Let's see. I do have a multi-bank NOCO charger, each bank is 12v. I've looked at some wiring diagrams that show higher voltage chargers for serial arrays-- those are probably industrial applications? So let's take that option off the table.

With regard to charging the batteries with our without the serial cable bonded: I've done some 'research' on the web and the advice varies. Some say that you should charge w/o the serial cable, some say you should charge with it in place. So I thought I'd ask folks here what they're doing.

@Evan B thanks for sharing your setup. If I went with the bond broken, I would consider putting in a quick disconnected on the serial bonding wire to simplify things. Sounds like that's what you have. Did you consider charging with the serial cable bonded like this video recommends? (should be linked to the charging section)
 
the_grube said:
Let's see. I do have a multi-bank NOCO charger, each bank is 12v. I've looked at some wiring diagrams that show higher voltage chargers for serial arrays-- those are probably industrial applications? So let's take that option off the table.

With regard to charging the batteries with our without the serial cable bonded: I've done some 'research' on the web and the advice varies. Some say that you should charge w/o the serial cable, some say you should charge with it in place. So I thought I'd ask folks here what they're doing.

@Evan B thanks for sharing your setup. If I went with the bond broken, I would consider putting in a quick disconnected on the serial bonding wire to simplify things. Sounds like that's what you have. Did you consider charging with the serial cable bonded like this video recommends? (should be linked to the charging section)
Click to expand...

Not entirely sure what he was getting at as far as a serial cable in the video to be honest. I have a three bank charger, one bank per battery. All stay connected to it at all times with the Noco charger installed in the boat. There's the quick disconnects in the series to break the series up during charging. It's been working just fine so probably won't change anything.
 
I have never disconnected anything when using my minnkota 2 bank charger for a 24V lithium battery system. I have 2 12V 100 ah Dakota batteries. Charging seems to always work fine, although I notice the battery closer to the TM usually takes 15-30 min longer to full charge. Not sure why. The minnkota manual says nothing needs to be disconnected to charge.
 
Just to clarify. Serial connection of two 12v batteries = 24v.

Parallel connection of two 12v batteries = 12v with more amp hours.

Lot of folks get this confused.
 
seems like this is one of those 'engineering' decisions with tradeoffs to make. Like I said in my OP I've been using a Noco charger with 2 12v banks, one attached to each 12v battery while the batteries were still wired in series. This has worked for me w/o any issues. I just recently had to disconnect that serial connection in order to get one of my Life Po4 batteries to take a charge ( it was showing the cross-wired warnging). so.... I'm gonna put a quick disconnect on my serial connection, and bring the batteries up from low charge states with the serial connection broken and top off and balance with the connection made.
 
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