12v versus 24v question

[heat checker]

Assuming 2 trolling motors of same thrust, both connected to 2 batteries. Will 24v draw down the batteries to a lesser degree than a 12v wired to 2 batteries? Guessing the 24v would give longer battery life (not run time) as the batteries would draw down and get recharged at exactly the same rate? But would the run time differ between the 12 and 24 volt?

[jeffreyd]

24v will give you more power and will last longer. when you tie two batteries 12 volt together you are not doubling the reserve capacity or the amps you only have the amps of the highest battery. while it will draw down equally, it will pull the system down faster on a 12 than 24v. on our fire trucks we ran 6 packs so basically 3 12 volt batteries tied together on one side and 3 on the other side. if one battery went bad all batteries got changed. so making sure that if you have two or more 12 volt tied together and one fails that you replace them both. reason being is the bad one is using all the amps the charging system can put in to keep it charged or get it brought back up. over time this starves the other battery(s) and when you change on single bad one you will find that the other one is quick to fail. good luck i would go 24 volt

[Whoaru99]

In theory two 12V batteries in parallel and two 12V batteries in series (24V) is the same net power (watts).

For example:

Two 12V, 105AH batteries in parallel will deliver 12V and 210AH for a total of 2520 watt-hours.

Two 12V, 105AH batteries in series will deliver 24V and 105AH for a total of 2520 watt-hours.

In practice the 24V system should be slightly more efficient so you should get somewhat longer overall runtime. Just how much I can't say for sure. Probably not night and day difference but should be an improvment worthy of incorporating if you can.

[BobT]

Whoaru99 is absolutely correct.

[fishwater]

With a 24V system you will see improved efficiency. You have less energy lost due to heat and internal resistance because of the lower operating current.

[heat checker]

Thanks guys.