Electrical engineering problem

[Dune]

The situation; I have a need for 32 volt (minimum) DC.
I have one bank of batteries wired for 24 volts (2 8Ds) in series charged by a 24 volt alternator.
I have one bank of batteries wired for 12 volts (2-8Ds) in parrallel, charged by a 12 volt alternater.

Can I join the two banks in series to create 36 volts? I would still need access to both 12 and 24 volt circuits.

My other options are to run a 32 volt alternater and a bank of four 8 volt batteries, or buy a very expensive inverter (32 volt output, very uncommon). The 32 volt device would cost several thousand to replace with a 12 volt version.

 

[woodgeek]

Little unclear....do you want to join the batteries while they are hooked up to charge, or can you charge them up, remove the charger and then wire/switch the batteries together?

If you wired the batteries in series, they would not discharge at the same rate, since one has a higher amp-hour capacity (the parallel one)....

Give us some more details.....what does the 32V load look like....there are some really nice and cheap DC-DC converters out there now. You could rewire the batteries to 12V all parallel, charge on a cheap 12V charger, and convert the 12 to 32 VDC to run the load.....

 

[Dune]

Little unclear....do you want to join the batteries while they are hooked up to charge, or can you charge them up, remove the charger and then wire/switch the batteries together?

If you wired the batteries in series, they would not discharge at the same rate, since one has a higher amp-hour capacity (the parallel one)....

Give us some more details.....what does the 32V load look like....there are some really nice and cheap DC-DC converters out there now. You could rewire the batteries to 12V all parallel, charge on a cheap 12V charger, and convert the 12 to 32 VDC to run the load.....

The batteries need to stay wired always. The 32 volt load is pretty small, an electo-magnetic clutch which is engaged aproximately 10 minutes per hour.
Each of the two banks has it's own alternator.
I haven't been able to find a reasonably priced 12-32 inverter. Can you suggest a source? Thanks.

 

[MasterMech]

Ok, I'm curious, WTH is this thing?

 

[Dune]

Ok, I'm curious, WTH is this thing?

Workboat. The 24 volt system is to start the diesel engine. The 12 volt system is for navigation electronics. The 32 volt clutch is a power take off to run a hydraulic pump to power deck machinery.

The starter circuit used to be 32 volt, but 32 is being phased out. The batteries are $1000 dollars each, with 4 being required.

It is possible that the clutch is 24 volt but I will not know until I can contact the manufacturer on monday.

 

[jharkin]

Short answer is yes, you can do it if you are careful. If you ran the setup down flat on the 36v load, you will damage the serial batteries since they would deep discharge below 12v while the parallel pack was still strong. Since you seem to have a light load and are setup to monitor and charge each pack seperately you should be ok.

 

[woodgeek]

The batteries need to stay wired always. The 32 volt load is pretty small, an electo-magnetic clutch which is engaged aproximately 10 minutes per hour.
Each of the two banks has it's own alternator.
I haven't been able to find a reasonably priced 12-32 inverter. Can you suggest a source? Thanks.

I put "12v buck boost modules" in the google and found this...

http://www.prodctodc.com/dcdc-1032v...le-power-stepup-module-p-85.html#.T_jZmnAtM7A

and

http://www.prodctodc.com/dc-nonisolated-converter-dc-booststep-up-c-1_15

for ~$7. Can't give you a guarantee, but looks like it would convert 12VDC to 32VDC at up to 150W or so. I'd prob buy two so I didn't get stuck out at sea if it quit !!

 

[Dune]

Short answer is yes, you can do it if you are careful. If you ran the setup down flat on the 36v load, you will damage the serial batteries since they would deep discharge below 12v while the parallel pack was still strong. Since you seem to have a light load and are setup to monitor and charge each pack seperately you should be ok.

The clutch switch is lit, and the pump adds noise as well. with 50 minutes to recover between each use, it shouldn't be an issue, in addition to the fact that there is tremendous excess amp storage compared to draw. Thanks, I wanted to make sure I wasn't missing something.

 

[Dune]

I put "12v buck boost modules" in the google and found this...

http://www.prodctodc.com/dcdc-1032v...le-power-stepup-module-p-85.html#.T_jZmnAtM7A

and

http://www.prodctodc.com/dc-nonisolated-converter-dc-booststep-up-c-1_15

for ~$7. Can't give you a guarantee, but looks like it would convert 12VDC to 32VDC at up to 150W or so. I'd prob buy two so I didn't get stuck out at sea if it quit !!

Thanks for the help. I will order one and torture test it.