How can I charge a 48v system with a 14v DC alt?

[uzippy11]

Hi,

I have been given a 48v FC 5kVM / Best Power Technologies UPS.

I am planning on using 4 12v 875 Max cranking amps/125 hour Marine/RV deep cycle batteries connected parallel.

I would like to know if it is possible and the best way to charge the batteries with a 14v 400amp C712 electromagnetic alternator / C.E. Niehoff (used in Fire trucks)

Appreciate any and all suggestions

[wdyasq]

Your knowledge of electricity and electrical system will have a lot to do with the options you may have. BUT - if you think 4-12V batteries in parallel give one 48 Volts, you need to brush up on a bit of elementary electrical theory.

There can be several ways. One will be to change the connections from series (48V) to parallel and charge. Then when they are charged, switch back to series and hook back up to the UPS. This will probably require a bunch of switches and be a real pain.

A voltage booster may also be used.

You should be informed many have found a UPS is not an efficient method of conversion of DC to AC and most have a lot of problems. A good 'Google search' of the board will being up many posts about UPS units as inverters.

Personally, I don't thing there is a good way to do what you propose unless you have a free source of power.

Ron

[Flux]

You must connect the batteries in series for 48v.

A 12v nominal vehicle alternator will charge 48v if you drive it fast enough. You must remove any internal regulator and supply the field by other means and keep the field supply at no more than 12v.

Flux