Thread: Wots been Happening in 101 World

Originally Posted by 101 Ron

A bigger altenater a deep cycle battery is not really a good thing in Garrys <snip> < O.K can accept that >
The altenator will not work until it is excited via indicator light globe ( 24 volt ) via the ignition switch. <Absolutely correct, and I was wondering where the second alternator was getting it's exciter current!>
The relay Diana indicated is not really nessary. <see below>
The up shot of this is if you use the 60 amp altenator, it is not a ideal system.
Bigger altenators like bigger continous loads.

Not sure I can agree with you about the 24V exciter current powering up a secondary 12V system.

The use of the relay is to electrically isolate both systems otherwise you have the 24V and 12V systems electrically connected.

Using a relay is also what the Australian Army does in it's 12V/24V SIII FFR.

Diana - thanks for the wiring information. I changed over the 24v ignition system to a 12v one a few weeks back and already have the relay in place working on switched 24v to activate 12v for the ignition so I can just take a 12v lead from there to a 12v ignition light and then back to the alternator. Just wasn't sure where it had to go on the alternator.

At the moment the 24v (90amp) system charges two 12v 600cca starter batteries, the starter, lights, wipers, washers, fuel pump, instruments and switching relays for the 12v system. The 12v system (now 60amp) charges the dual purpose 105 Ah deep cycle/starter battery, the LPG system, trailer lights, radios, and anything connected like fridge, camp lighting, phone, laptop etc - it will also run my spare portable 15,000ib electric winch if I were to carry it.

It sounds all convoluted but it is a really simple solution that works well. I also carry an electronic 30amp 24v - 12v converter just in case the 12v system crashes and if the 24v system crashes I can play around with the 12v connections to give 24v with the aid of a portable power pack and a crank starter when I make it if needed.

I researched either changing over to 12v completely or having a 12v charger but it is not simple to simply pull the lot out - likewise a 12v charger with high enough amps to cover all scenarios is very expensive. So I have stayed with what was there as it does work well.

Thanks for all the comments

Garry

Garry

Sounds like you have it all in hand!

Diana

Originally Posted by Lotz-A-Landies

Not sure I can agree with you about the 24V exciter current powering up a secondary 12V system.

The use of the relay is to electrically isolate both systems otherwise you have the 24V and 12V systems electrically connected.

Using a relay is also what the Australian Army does in it's 12V/24V SIII FFR.

The alternator has the main cable going from the main connector to the battery. It also has a second wire on this main connector going somewhere - not sure where. There is no exciter on a seperate connector to D+. As the LPG does still work with the engine running and the secondary 12v battery removed, I assume 12v exciter for the 12v alternator comes from one of the starter batteries (2x12v in series) - the current required to excite the alternator is quite small so will not upset the charge levels of the two starter batteries.

If it stops raining tomorrow - I will see what is happening and find out where the excitement is coming from. Maybe the alternator gets its excitement from just one wire - I will investigate.

Garry

Too much excitement is not good!

Seeing that you have the two systems, it may be an opportune time to separate everything so that all 12V equipment works off the one 12V system and all 24V stuff off the 24V. Otherwise it all starts getting too confusing which of the three 12V batteries is running which 12V item.

As they say: Make it simple stupid! - Not suggesting that you are, but knowing that you have inherited the setup from the previous owner. (Although as I understand it, the 24V 101 has a number of functions that are 12V standard, like the fuel guage and sender. This may be the source of the LPG and 12V exciter current.) )

good advice di
be careful or it could end in tears , dont let the smoke out garry

Someone else expert in AC power generation may have to answer this for us. however I believe that the alternator initially needs an exciter current to the field to generate AC, which is then rectified into DC. If there is no exciter current, the globe blows or the wire disconnects, some alternators will self excite once they reach a certain speed.

This may be the reason your alternator has been working up to now without the exciter wire, however using the exciter/lamp circuit makes the generation more efficient, particularly at low revs.

yes that is right .. the alternator needs a dc voltage to activate
i had a duel system on my old 6 tonner it worked fine ran a lead from 12 v positive teminal and a switch worked for years no dramas