24 versus 12 V

[Gaspasser1]

I have two 12V 100 amp hour Dakota lithium batteries connected in series for my 24 volt trolling motor.
Can I connect to one of the two 12 V batteries to power my 12 V needs on the boat?
Thanks for your reply in advance.

 

[BentleyJ]

No, not unless you have a way to charge each battery individually at 12V. They will get out of balance by discharging one more than the other.

What you need is a 24V to 12V DCDC converter.

How many amps do you need for the 12V accessories on the boat?

EDIT: Here is an example.

https://www.amazon.com/Victron-Energy-Orion-Tr-240-Watt-Bluetooth/dp/B085G72RQ2/ref=pd_lpo_sccl_3/140-7566810-0546903?pd_rd_w=KuV5Y&content-id=amzn1.sym.1ad2066f-97d2-4731-9356-36b3edf1ae04&pf_rd_p=1ad2066f-97d2-4731-9356-36b3edf1ae04&pf_rd_r=BH261X91BKK8V1ZZRJX4&pd_rd_wg=mlAdc&pd_rd_r=7c96b809-079a-4fdf-bf58-64f60945e4b2&pd_rd_i=B085G72RQ2&psc=1

 

[Gaspasser1]

OK that makes sense, thank you very much.
I will look into a DC to DC inverter.

 

[SparkyGage]

No, not unless you have a way to charge each battery individually at 12V. They will get out of balance by discharging one more than the other.

What you need is a 24V to 12V DCDC converter.

How many amps do you need for the 12V accessories on the boat?

EDIT: Here is an example.

https://www.amazon.com/Victron-Energy-Orion-Tr-240-Watt-Bluetooth/dp/B085G72RQ2/ref=pd_lpo_sccl_3/140-7566810-0546903?pd_rd_w=KuV5Y&content-id=amzn1.sym.1ad2066f-97d2-4731-9356-36b3edf1ae04&pf_rd_p=1ad2066f-97d2-4731-9356-36b3edf1ae04&pf_rd_r=BH261X91BKK8V1ZZRJX4&pd_rd_wg=mlAdc&pd_rd_r=7c96b809-079a-4fdf-bf58-64f60945e4b2&pd_rd_i=B085G72RQ2&psc=1

Umm.... That victron "may" not be the right solution. Is the boat charging the battery from the motor/alternator?

If you are just wanting to run your 12v accessories, I'm thinking more like this: https://www.amazon.com/uxcell-Converter-Regulator-Transformer-Waterproof/dp/B01LYK6G2Y . You will need to calculate the maximum load, but if its just lights and a radio it should be OK. If you have a power trim, I would NOT use a converter and keep a separate battery due to the amp requirements.

I'm doing similar with my sail boat: I run a 86lb thrust trolling motor from a 24v battery but still have 12v running the cabin, currently on a second 12v battery. My plan is to add the above part and a switch so I can run the cabin from either battery. I'm doing this because I want a second 24v battery (range anxiety), and don't want to juggle 3 batteries.

Cheers

 

[CCJ]

The smart Orion units can be put in charger mode or power supply mode. When in power supply mode you can set the voltage and current.

 

[ZEUS-FL]

Is not this device a solution? maybe what is in discussion now?

Victron Battery Balancer

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[mikefitz]

connect to one of the two 12 V batteries to power my 12 V needs on the boat?

As discussed , no.
This 24 to 12 converter is ideal, 20 amp output.

https://www.amazon.com/Victron-Orion-Tr-12-20-DC-DC-converter/dp/B01M0HTT8D/ref=sr_1_6?crid=MP0OJ6LOCTLH&keywords=Victron%2B24%2Bto%2B12&qid=1707177941&sprefix=victron%2B24%2Bto%2B12%2Caps%2C408&sr=8-6&th=1

The Orion discussed earlier is a charger and although useable is more expensive. If 20 amps is not enough there are more powerful versions in the Victron series.

Is not this device a solution?

No, that's a battery balancer not a voltage converter. However it would be useful to ensure the two 12v batteries equally balanced. Eventually, where batteries , each with its own BMS, are charged in series, the charge each receives gets out of balance. The rectify this, each battery needs too be charged separately with 12v charger from time to time, or a battery balancer added .
If the OP always charges the batteries separately as 12v batteries then out of balance will not happen.

 

[ZEUS-FL]

I do not mean to use a voltage converter. I mean to wire the 12V equipment to only one battery and when became unbalance the balancer will do the job to keep both in balance. I have 7S Li-ion batteries packs 7S7P for 24V applications but i have connectors wired for 12V application on the same pack. When the became unbalance the 5A active balancer do the magic. I believe should work in a 2P2S case.

 

[ZEUS-FL]

Also depending how much Watts do you need in 12V (not crancking of corse) you can use a step down converter. I have this one and works very well. https://www.aliexpress.us/item/3256..._main.107.53101802KuDt14&gatewayAdapt=glo2usa

 

[SparkyGage]

I do not mean to use a voltage converter. I mean to wire the 12V equipment to only one battery and when became unbalance the balancer will do the job to keep both in balance. I have 7S Li-ion batteries packs 7S7P for 24V applications but i have connectors wired for 12V application on the same pack. When the became unbalance the 5A active balancer do the magic. I believe should work in a 2P2S case.

That seems like a lot of overhead (wear and tear) on that one cell and the system as a whole, vs using a DC-DC converter to supply the needed voltage and keep the pack functioning as a system. I'm curious what the long term affect on cell life compared to the others in the pack.

 

[Checkthisout]

I have two 12V 100 amp hour Dakota lithium batteries connected in series for my 24 volt trolling motor.
Can I connect to one of the two 12 V batteries to power my 12 V needs on the boat?
Thanks for your reply in advance.

Yes but you have to charge separately every once in awhile. Minn Kota and such make bank chargers that charge each battery separately depending on how fancy you want to get.

What are we talking? Fish Finder and a couple little Nav leds?

Military Equipment uses this method.

 

[jdege]

One thought - does your "12 V needs" include the bilge pumps?

Maybe it's just me, but I want as few parts, and as few possible points of failure, on my bilge pump circuits as possible.

 

[ZEUS-FL]

What I used to do in my bass boat back in the days with 2 lead acid deep cycle batteries was that I had the permanent connection for 24V but at the same time I had wiring for parallel connections with with switches to open and close the circuits for charging.

When I want to use the series configuration I open the parallels connections and vise versa for series to balance the batteries and charging as well. That should work in theory with the new batteries.