Do I need to upgrade the alternator

[Bex]

I was given two deep cycle batteries that were part of my clients computer system regular UPS replacement program (they had 160 to get rid of).
I just installed them in series, in the '76 Argosy.
So when plugged in to the tow vehicle, is the alternator charging them and the vehicle battery?
Its a 104 amp alternator, is that enough?
If the tow vehicle is plugged in, and the is no shore power, does the trailer draw from all three batteries or is the tow vehicle isolated from the draw by the univolt?

Thanks

Bex

[HowieE]

There is no need to change your alternator. The only reason for a larger alternator would be if you had a large draw like the lights on an parked ambulance.

Yes if you are dry camping and the TV is still connected the trailer will draw from all batteries.

[drboyd]

I take it the new batteries are 6 Volts each, to be in series. If they're (2) x 12 Volts in series, things are gonna get real fun real quick.

When the tow vehicle is plugged in, all three batteries are charged when the vehicle is running, and all three batteries are being drawn from when the vehicle is off. The Univolt does nothing to isolate them.

The alternator will only charge as fast as it can; you'll get what you get in terms of charging speed.

If you are still using the old Univolt, with the new AGM batteries, do yourself a big favor and switch that out to an intelligent charger - the guy at bestconverter.com gets good marks for his advice. Not only will you save a bunch of weight, you'll also keep from boiling your batteries to death.

[Jammer]

Originally Posted by Bex

So when plugged in to the tow vehicle, is the alternator charging them and the vehicle battery?

Maybe.

Mine did last fall. This spring it didn't. I found a failed relay and a corroded connector, both of which I fixed. Good thing I measured the charge current before depending on alternator charging the batteries, wasn't it?

You have to test this stuff, somehow, and be sure it's working, because the only indication of failure is that your batteries go dead when you need them.

Its a 104 amp alternator, is that enough?

It depends on what your goals are. A small-frame alternator like that will work OK and will charge the batteries to a degree most of the time. It may not charge them much under adverse conditions such as when the engine is idling, the headlights are on, and the heater fan is running. I upgraded mine. Depending on what your tow vehicle is, there may be upgrade that make sense.

If the tow vehicle is plugged in, and the is no shore power, does the trailer draw from all three batteries or is the tow vehicle isolated from the draw by the univolt?

It depends how your vehicle is wired. There is variation in new vehicles and then there are aftermarket modifications that may have changed things. Again the best thing to do is actually measure the current.

[Bex]

Yeah, in parallel, not series, thanks!.

Originally Posted by drboyd

I take it the new batteries are 6 Volts each, to be in series. If they're (2) x 12 Volts in series, things are gonna get real fun real quick.

When the tow vehicle is plugged in, all three batteries are charged when the vehicle is running, and all three batteries are being drawn from when the vehicle is off. The Univolt does nothing to isolate them.

The alternator will only charge as fast as it can; you'll get what you get in terms of charging speed.

If you are still using the old Univolt, with the new AGM batteries, do yourself a big favor and switch that out to an intelligent charger - the guy at bestconverter.com gets good marks for his advice. Not only will you save a bunch of weight, you'll also keep from boiling your batteries to death.

[Bex]

I did read in another thread that its unlikely the trailer batteries will charge and thats because of the thin wires running from the plug in through to the batteries themselves so its likely not something to be overly concerned with.

Many thanks for the comments.

[Jammer]

There are some situations where it is extremely useful, even critical. If it's below freezing or nearly so and you have the furnace on while under way, for example, you need it. I have found it pretty much necessary for winter boondocking, since I don't carry a generator.

[Bex]

Originally Posted by Jammer

There are some situations where it is extremely useful, even critical. If it's below freezing or nearly so and you have the furnace on while under way, for example, you need it. I have found it pretty much necessary for winter boondocking, since I don't carry a generator.

Do you know what the fix is? Do we need to run thicker gauge wire for the charge line? Does the TV battery need to be isolated from the trailer?