Tapping of one of my 12 volt / 24 volt setup.

[WISportsman]

Hi,
Right now I'm running 2 12 volt, SLA batteries in series for my 24 volt trolling motor. I have my locators coming off of one of the 12 volt batteries. Now that I'm switching to LiFePO4,I'm wondering if this will be ok? TIA

 

[Q-Dog]

No. You will cause the batteries to eventually go out of balance with each other.

Running BMS controlled batteries in series has enough issues with maintaining balance without intentionally causing the batteries to go out of balance.

I do run one 24 volt pack made up of 12 volt LiFePO4, and use the Victron battery balancer on them.

Victron Energy BBA000100100 Battery Balancer

Victron Energy Battery Balancer

shop.pkys.com

 

[robbob2112]

That will cause an imbalance in the charging and the one not being tapped will end up finishing charge first and cut off before the other is full.

Running 2 in series like that you need to do 2 things to be trouble free

1. use an active equalizer like the HC01

Amazon.com

2. for your 12v loads use a 24v to 12v buck converter like this across the string

Amazon.com

You can try it with just tapping the single battery like you are now but monitor it for an imbalance after a while, but you will end up with the buck converter in the end

 

[WISportsman]

Thanks!

 

[AnarchyJet]

No one asked how you are charging the batteries? If you are using 2 separate 12v chargers for each battery, then I don't see a problem. If you are charging with 1 24v charger, then all the above is true.

 

[robbob2112]

No one asked how you are charging the batteries? If you are using 2 separate 12v chargers for each battery, then I don't see a problem. If you are charging with 1 24v charger, then all the above is true.

Using two 12v chargers like you describe is a horrible idea. The batteries will never have the same SOC and while it might work it isn't really a long term workable thing...

 

[JerryK]

The thing is most smaller inland boats/fishermen do use onboard chargers that are just that, multiple 12 volt charging banks within a single charger. There are also 24v and 36v onboard chargers.

 

[Texas-Mark]

Using two 12v chargers like you describe is a horrible idea. The batteries will never have the same SOC and while it might work it isn't really a long term workable thing...

Huh? It would work fine. How do you figure they would never have the same SOC? If both charge to 100%, the pack is then at 100%. I would even argue it would keep them balanced better than a single 24V charger that has no idea of the SOC of either battery. One battery could constantly be going into HV cutoff before the other is fully charged, keeping them constantly out of balance.