How to charge

[oiler]

I've been wondering....and no one i have asked can give me an answer.

Is it possible to charge a battery bank at say 24 volts in parallel, and at the same time use 48 volts from it in series?
The reason for doing this is i'm alredy using a 24 volt bank and i would like to add some 48 volt inverters.

Torsten

[mobile_bob]

i am assuming you have enough batteries so that you can split them into two groups of 24volts each
so that you can then series connect the two 24's into a 48volt source to power the inverters?

if so you cannot charge both 24volt banks generally from the same charging source, because you would have
a short circuit from the positive of one bank to the negative of the other, mid string. this is if you want to power
the 48volt inverter at the same time you are charging

if you can charge and not power the 48volt inverter, a simple series/parallel switching scheme would work well
to allow you to charge both halves from a 24volt source in parallel switch function and then switch over to 48 volt operation
via the series switch function.

if you have to have the ability to charge at 24 and use both at 48 at the same time, then you must provide two seperate
and isolated ground charging sources.

so i guess a couple of questions are in order

1. do you have enough batteries to make up two seperate 24volt banks?

2. what do you have to charge with for 24volts currently? is it a genny driven charger? solar? windgenerator? other?

3. if you are charging with an engine, could you install a 48volt nominal alternator system to charge the batteries wired
for 48, or do you need to retain 24volt battery capacity for other uses?

bob g

[BruceM]

Bob's right-  your 24V chargers must have isolated outputs.  One will be doing 0-24V and the other 24-48V.  If they are isolated, the outputs are transformer isolated, and they "won't care" if the negative terminal is connected to 24V relative to ground.

Buck converter/regulators (used for voltage step down only) don't have a transformer, and tend to be higher efficiency.  Their output is NOT isolated.

[oiler]

Bob
Shortening the mid string. Embarassing i couldn't see that myself.

I haven't got the batteries yet i'm in the planning phase, but i thought i might need som expert input before i got in too deep. Turns out i do need it

As now i charge 24 volts from my wind and solar setup and i need the 24 volts as we run qute a lot of 12v LED bulbs in series of two in order to have the right voltage. the number of bulbs in each room cannot be divided into 12v

My plan is to charge the  batteries from my 6/1 stc-10 but i also would like to use my current  wind /solar setup.

Another qestion is. My plan reg. inverters is to have three inverter chargers in order to get three phase  power, but can these three use from and charge the same bank?

As it is now, i'm powering the house directly from the STC. It works..even not too bad, but SWMBO DOES notice it as she cannot use washer,dryer, oven, stove and vacuumcleaner at the same time without a severe drop in voltage (and frequensy).
The reason to get inverters is to be able to run the whole caboodle as a standard three phase cirquit and help the poor 6/1 (and keep wifey happy)

Hope it makes sense to you.

Perhaps i can stepdown the 48 volts to 24 for my LED's. But the charging part i'm not sure how to get right.

Torsten

[BruceM]

Torsten, Given your use of 24V for lighting, it would make more sense to stay 24V.  Direct off the battery voltage lighting is a very nice solution- no losses, no equipment to fail, low EMF.  A healthier home situation.

Using a buck converter to take 48V down to 24V would also work, though you'd have to do some electronics work to depower the buck converter at night.
You'll also have to find one that can handle a 0 amp load. EMI will be a problem, and it's not cheap to solve via filters, but it can be done.  If you decide to go this way, send me the specs before you buy one and I'll check it out.

Best Wishes,
Bruce M
Snowflake, AZ

[oiler]

You are probably right about staying at 24v. Perhaps i should try a two string soloution and keep lights and turbine/solar together in one system, and inverters on a 48 volt battery charged from the 6/1

Thanks
Torsten