Alternator(s) question

[Murv]

I've recently replaced one of the alternators on my twin engine mobo.
The connections on the back are (obviously) completely different. I've installed, the alternator, everything is working perfectly, but I have a mystery wire left with nowhere to connect it to.
It runs from a "split charge switch," when the switch is on, the wire is at the voltage of the second engine's battery bank, can I connect this wire to the main positive terminal on the new alternator? And if i do, does this just give the capability for both alternators to charge both battery banks, spreading the load between them?

 

[PaulRainbow]

I don't think you can. Can you post a pic of the old alternator and the new one ?

What engines do you have ?

 

[Murv]

TAMD61A's, I'll try and work out how to post pictures tomorrow. I think, from Googling, that the old alternator had twin pole connections, the new one doesn't. (I'm probably completely wrong on that)
On the old alternator, the split charge wire connected to a terminal that the regulator was connected to, on the new alternator, the regulator is connected straight to the single positive terminal.

 

[PaulRainbow]

TAMD61A's, I'll try and work out how to post pictures tomorrow. I think, from Googling, that the old alternator had twin pole connections, the new one doesn't. (I'm probably completely wrong on that)
On the old alternator, the split charge wire connected to a terminal that the regulator was connected to, on the new alternator, the regulator is connected straight to the single positive terminal.

I think you will find that what you are thinking od as the regulator is, in fact, a split charge diode. It's fixed to the rea of the alternator and look as if it's a part of the alternator. It is discontinued now. A picture will confirm.

If i am correct and you still want the engine to charge both batteries, you can fit an external device to do that.

 

[Alex_Blackwood]

I've recently replaced one of the alternators on my twin engine mobo.
The connections on the back are (obviously) completely different. I've installed, the alternator, everything is working perfectly, but I have a mystery wire left with nowhere to connect it to.
It runs from a "split charge switch," when the switch is on, the wire is at the voltage of the second engine's battery bank, can I connect this wire to the main positive terminal on the new alternator? And if i do, does this just give the capability for both alternators to charge both battery banks, spreading the load between them?

Is this any help?
ME08.

 

[Murv]

Is this any help?
ME08.

I did read that before, thank you, I don't think it really applies because it's more two starter circuits rather than a dedicated domestic and starter system

 

[Murv]

 

[Murv]

 

[Murv]

The top two images are the original alternator, the one below is the new one. The split charge cable is the thick, brown one, bottom left.

 

[PaulRainbow]

The top two images are the original alternator, the one below is the new one. The split charge cable is the thick, brown one, bottom left.

It is as i suspected. The device on the left, to which the thick red and thick brown cables are attached is a split charge diode.. It has been discontinued and wouldn't fit the new alternator anyway. It would be worth keeping the diode as a spare.

Your charging would typically be wired so the the thick red wire from each alternator goes to the engine start battery, with the thicker brown wire going to the domestic bank (kept separate from the engine batteries by the diodes). As it is now, the new alternator only charges the engine battery, you've lost half of your domestic charging.

You can restore the domestic charging in a few ways, the better of the two for your setup would be :

a) Fit a split charge diode. This can be mounted anywhere convenient between the alternator and the batteries. The thick red cable connects to the diode and the two diode outputs connect to each battery bank respectively. You will get around 0.7v voltage drop because of the diode.

b) Fit a Victron Argofet. You could fit a single engine version, just to the engine that you changed the alternator on, wiring is the same a above, with the addition of a 2.5mm negative wire, possible a switched positive. Or, you could fit a two engine version, where it has inputs for each engine and two outputs, one to each battery bank, plus the single negative and maybe a switched positive.

Any of the above are relatively simple to install. The twin engine Argofet would be my personal choice. Make sure you keep that redundant thick brown wire well insulated !

 

[Murv]

Thanks for that, I really appreciate your detailed reply.
The original battery configuration was two port batteries and two starboard, both in parallel, the Port set also doubled as the leisure bank which was obviously pretty feeble.
I've since built a large lithium battery which I use for the leisure bank (completely independent to the original lead acid batteries) so I don't really use the original batteries as a leisure bank.
The lithium only charges from the mains, although I could run the inverter from the lead acid with a two way switch and charge the lithium bank that way, although in practice the lithium bank gets me a solid 4 days off grid and I just spend a day in a marina to charge it back up.
Would I be better off just removing that split charge switch cable and fitting a battery to battery charger for the lithium, whether it's one smaller charger from each bank or a dual input?

 

[PaulRainbow]

Thanks for that, I really appreciate your detailed reply.
The original battery configuration was two port batteries and two starboard, both in parallel, the Port set also doubled as the leisure bank which was obviously pretty feeble.
I've since built a large lithium battery which I use for the leisure bank (completely independent to the original lead acid batteries) so I don't really use the original batteries as a leisure bank.
The lithium only charges from the mains, although I could run the inverter from the lead acid with a two way switch and charge the lithium bank that way, although in practice the lithium bank gets me a solid 4 days off grid and I just spend a day in a marina to charge it back up.
Would I be better off just removing that split charge switch cable and fitting a battery to battery charger for the lithium, whether it's one smaller charger from each bank or a dual input?

I think you're going to be wasting two useful things Murv. Charging both banks with each alternator, not massively wasteful on its own, as the batteries are all engine batteries now. A cheap and simple diode would cure that.

Also, not charging the Lithiums from the engines. I'm guessing your alternators are about 60a @24v ? That's a lot of potential power going to waste.