I have two motors, one that requires 12v, and the other that requires 24v. Would it be a bad idea to have two 12v SLA batteries in series to give me the 24v which I can connect to the one motor, and then only use the one battery for the other?

The 12v motor (actually two wiper motors) is drawing around 5A continuous in total, and the 24v motor is drawing around 6A.

Is this going to be bad for the batteries? would I be better off with specific sources? (i.e two 12v in series for the 24v, and then a separate third for the 12v)?

 

to have two 12v SLA batteries in series to give me the 24v which I can connect to the one motor, and then only use the one battery for the other?

One battery will discharge twice as fast as the other. Charging these batteries in this setup is also tricky.

would I be better off with specific sources?

Yes, this is a better choice.

The 3rd option is to use a 12V to 6V switching convertor to power the 12 V motor off a 24 V setup.

 

What you have described is a fairly common situation. And just like already mentioned, the total current is drawn from the one battery and much less from the other. However, is this in a vehicle installation where all of the return power connections are to the vehicle frame ground? Or is this a non-vehicle application where each motor is electrically separate? In that case there are some options available that might be useful.

 

Ah ok, so something like this?

https://www.ebay.co.uk/itm/Dc-24v-T...le-Buck-Volt-Converter-Regulator/322724331129

Would this be a lot less efficient?

 

I have two motors, one that requires 12v, and the other that requires 24v. Would it be a bad idea to have two 12v SLA batteries in series to give me the 24v which I can connect to the one motor, and then only use the one battery for the other?

The 12v motor (actually two wiper motors) is drawing around 5A continuous in total, and the 24v motor is drawing around 6A.

Is this going to be bad for the batteries? would I be better off with specific sources? (i.e two 12v in series for the 24v, and then a separate third for the 12v)?

So the load on the first battery is 11A and the load on the second battery is 6A. The only challenge will be charging both batteries, because a simple 24 volt charging arrangement will not work right.

 

What you have described is a fairly common situation. And just like already mentioned, the total current is drawn from the one battery and much less from the other. However, is this in a vehicle installation where all of the return power connections are to the vehicle frame ground? Or is this a non-vehicle application where each motor is electrically separate? In that case there are some options available that might be useful.

It's an RC vehicle I am building. The motors are electricly separate as the frame is made from wood.

 

So the load on the first battery is 11A and the load on the second battery is 6A. The only challenge will be charging both batteries, because a simple 24 volt charging arrangement will not work right.

Currently, I take it apart to charge them - it's a little inconvenient, but I don't mind

 

Both methods will work, but I prefer using the stepdown converter. Light aircraft face a similar problem with 24V batteries and some 12V equipment. As charging is continuous while the engines are running (as in a car), the ones I have seen all use a stepdown supply. I have not seen a split battery supply.

 

If the 12 volt motors are very similar, and if they are always bot run at the same time, then it could work to put them in series. Then everything would run on 24 volts. It is an idea that may, or not, be applicable. But if it would work it would be a cheap and easy solution.