Alternator charge splitter

[Nick_H]

I have two "multi battery isolators" on the boat, one for each engine, which split the alternator charge between the domestic and start batteries and isolate the two banks. They are Volvo Penta branded, and rated at 70 amp, part # 872928. Both have failed such that they no longer charge the start batteries. They look like this:

Obviously I can just replace them, and they are not that expensive in boat terms, £150 each, but i'm wondering why they've failed. I don't have the details of my alternators to hand, but the standard fit for a VP D12-715 seems to be an 80 amp, so it appears that the isolators may be under specced.

There are lots of proprietary products available, would I be better to fit a 90 amp splitter like this one instead, and save myself a few quid into the bargain?

https://www.yachtbits.com/split-charge-diodes-and-vsrs/D90A2

 

[jamesm]

A few weeks ago, I had the same situation. I decided not to fit a diode, because of the voltage drop, so I ended up fitting one of these:

http://www.sp-shop.co.uk/Sterling-P...tion-Systems-12v-2X130A-4-out-PN-PSRT134.html

I currently have 2 x 38amp alternators, so there's plenty of capacity left if I upgrade them in the future.

It seems to do exactly what its supposed to and was fairly easy to fit (I have no connection to the manufacturer or supplier).

 

[Chris_d]

Had the same part and two failures, fitted the Stirling one at 20A higher rating and its not failed yet, if they run hot they need to be derated so a 70A splitter at 80degC becomes
a 60A splitter etc...

 

[kashurst]

unusual for them to fail but if they are underspecced thats most likely the cause - unless you have had boiled batteries recently indicating a possible alternator problem. Replacing them with a suitably rated equivalent should be perfectly OK, theres nothing special about a volvo split charge diode - except the price. Re the zero voltdrop device - seems to be gilding the lilly to me as the engine alternators usually measure the battery voltage at the starter motor solenoid, not the output voltage of the alternator to control charging.

 

[A_8]

I had one of those, they did not break but it was messy with the voltage drop so changed it to this http://www.ctek.com/gb/en/chargers/SMARTPASS seems to be working ok.

 

[Nick_H]

Thanks to all, i'll order a couple of the 90A Sterling splitters, anyone know if they are universal voltage, or do I need to order a 24V specific item.

 

[VicS]

Thanks to all, i'll order a couple of the 90A Sterling splitters, anyone know if they are universal voltage, or do I need to order a 24V specific item.

Yes if you have 24 volt systems you will need to order the 24 volt versions

See the Sterling power website for details of the full range , data sheets and fitting instructions. http://www.shop.sterling-power.com/acatalog/index.html


You could also consider the merits of VSRs.

 

[aquapower]

Thanks to all, i'll order a couple of the 90A Sterling splitters, anyone know if they are universal voltage, or do I need to order a 24V specific item.

The diode type like pictured above are same for all voltages, they can fail if battery's are turned off with engines running or a heavy load is drawn through them.