Alternator Rating of Sure Power split charge multi battery isolator

[catmandoo]

I have two alternators feeding into a Sure Power split charge(multi battery isolator ) diode unit .
It takes output from two alternators and has an input to three battery banks .

It gives a maximum alternator rating of 70 amps .

however the literature does not say whether this is for each input i.e. 140 amps total or for the combined input . I have contacted Sure Power but have not yet had an answer .

Does any body out there know ?

 

[VicS]

I would read the instructions as meaning 70 amps for each alternator .. 140 amps total.

 

[William_H]

Alternator rating

Yes I think that 70 amps each alternator would be within the ratings of the diodes. However if for some reason both alternators were pumping out their 70 amps at once the whole device may overheat due to all diodes being at full rating. This situation is highly unlikely unless you are running a huge inverter or similar load or have very flat batteries. Even then only a problem after some time. So yes probably safe to assume OK good luck olewill

 

[charles_reed]

I'd suggest that few diode units will stand an input of a total of 140 amps.

Mine melted all its potting compound under the input from a 100 amp alternator and was replaced by a 140 amp-rated one which has a very large heat sink and is about x2 the size.

Unless your two alternators have smart controllers, it's unlikely that they'll ever produce their rated output unless into faulty/fully discharged batteries.
Contrary to popular opinion the rated output is the maximum that the alternators are designed to produce.

 

[sailinglegend420]

................. it's unlikely that they'll ever produce their rated output unless into faulty/fully discharged batteries.
Contrary to popular opinion the rated output is the maximum that the alternators are designed to produce.

Sorry Charles, but it's very very easy for an alternator to produce its maximum output for a considerable period of time - and hence overheat - so if you have a multi-stage charger fit a temperature sensor that will control the output if it gets too hot.

Our alternator burnt out last year because we have AGM batteries which will take as much current as you can throw at them. So the batteries will easily be calling for 60 amps or more when 75% full, the nav equipment and auto pilot takes up to 15 amps, and the watermaker 25 amps. That's 100 amps from my 100 amp alternator under normal conditions.

Everything had been fine until we installed the watermaker!!!! The alternator had a dodgy internal connection and the temperature sensor did cut the power output to half and save the alternator from catching fire. Now I let the alternator bring the batteries up until the charging current is about 40 amps before running the watermaker.

 

[catmandoo]

I'd suggest that few diode units will stand an input of a total of 140 amps.

Mine melted all its potting compound under the input from a 100 amp alternator and was replaced by a 140 amp-rated one which has a very large heat sink and is about x2 the size.

Unless your two alternators have smart controllers, it's unlikely that they'll ever produce their rated output unless into faulty/fully discharged batteries.
Contrary to popular opinion the rated output is the maximum that the alternators are designed to produce.

I have 2 alternators one at 30 amps and the other at 70 amps with smart controllers on both . Amperage from the 70 amp unit had peaked at 60 amps and with ambient temperatures in Turkey at 35 degrees plus I found that the potting compound on the 70 amp alternator regulator mounted on its back had melted and drifted down to the brushes making them sticky at start up . In looking into it I realised that there were other units in the circuit that would then have temperature problems due to high current .
I wondered then if I had misinterpreted the Sure Power rating . and perhaps a need to increase cable size due to ambient temperature and lack of air circulation
Currently looking into fitting a blower to remove some of the heat .

What might be ok for Northern waters may not apply in the Med