2nd 24 volt alternator... how large??

[Kevin Warnock]

I have a Xantrex/Trace 4024 inverter on my bus. I want to run one 10 amp AC from it while driving. I am considering powering it with the bus alternator, which is quite large.

I have read dozens of posts about the perils of trying to use the bus alternator to charge two banks of batteries. Thus, I am strongly inclined to install a second alternator, also 24 volts, and use that to keep the starting batteries charged and otherwise power the bus itself. I would rewire the existing bus alternator to only feed the house bank and inverter.

So, my question is this: How large an alternator do I need to keep the starting batteries charged and otherwise power the bus itself? I don't have bus AC, of course.

Separately, where should I mount the second alternator? My bus mechanic suggests by the blowers, up high in the engine compartment. He has seen this done on other buses, and is willing to install one like this on my bus.

Thanks,

Kevin

[TomC]

Usually there is an extra pulley already on the left side of the engine in the front (looking from the back of a T drive on the right side about mid way up).  Just use a 130amp Delco, Leece Neville, etc, and you're there!  Good Luck, TomC

[Stan]

If you are using regular flooded cell lead acid batteries, there is nothing wrong with using the bus alternator to charge them and it will keep the engine batteries charged at the same time. If you want to improve the charging curve, you can use a three stage voltage regulator on your present alternator.

[belfert]

If you are using regular flooded cell lead acid batteries, there is nothing wrong with using the bus alternator to charge them and it will keep the engine batteries charged at the same time. If you want to improve the charging curve, you can use a three stage voltage regulator on your present alternator.

I thought three stage regulators don't work all that well on flooded starting batteries?  I know they are great for flooed deep cycle batteries.

Brian Elfert

[NJT5047]

If you have a 50DN for OEM alternator, you have plenty of charging capacity already.  Sounds like you're not using the coach AC...?   The 10 amp AC powered thru an inverter won't be noticed. 
Cheers, JR

[RTS/Daytona]

Keven

NOT TO WORRY

Your 50DN 270 AMP alternator can handle it - here's how

Most Bus OEM A/C units have - 2 Condensor motors (3/4 hp) - 26V at 16 amps each = 26 x 16 x 2 = 832 watts
Most Bus OEM A/C units have - 1 Evaporator motors (1.5 hp) - 26V at 32 amps each = 26 x 32 x1 =  832 watts
total = 1664 watts

your 10 amp at 120 volt with a 90% effient inverter = 10 x 120 x .90 = 1080 watts

plus

50DN alternator a IDLE - max amps at 26 volts @ 165amps or 26v x 165amps --> 4290  WATTS !!!!!!

50DN alternator a 1000 rpms ------------26 volts @ 250amps or 26v x 250amps --> 6500 WATTS !!!!!!!

with that much power - now tell me there's not enough power to charge a good size battery bank

Pete RTS/Daytona

[pvcces]

That's tellin' them, Pete. And I agree. Whatever the charging misbehavior some people have had, I'm sure it was due to something not working as it should.

If a person has an auxiliary, then they will have at least two full charging systems, when they count the inverter. Boeings may have triple redundancy, but I don't really think that we need it.

For what it's worth.

Tom Caffrey
Suncatcher
Ketchikan, Alaska

[Hartley]

Pete,

I have a couple of motors from my old FLX and they were 2.0 hp @ 71 amps and 26 volts.
One that I took out of my MC9 condenser unit says 2.0 hp @26 volts but doesn't have an amp rating stamped on it.
I think I still have a couple of the 12 volt 3/4 hp ,motors from the Scenicruiser and they were marked 12 volts @70 amps.
the best part of those is that they are 2-speed motors.

The only way to really know is look at the ratings plate on the motor case. Seems like most that I have found
were made by Ohio Motors. ( but not in Ohio ? )...

[Stan]

Brian: You may be right but I don't know any technical reason why they wouldn't improve the charging on starting type batteries. You should be able to program the three stage regulator to provide the optimum charge curve for any type of battery.