ID #1159


I enquired about a split charge diode for a 91 volkswagon caravelle/transporter short wheelbase a friend is trying to convert, He tells me that he believes the alternator is 85amps. Would the 70amp diode suffice ,the only power req from the leisure battery is a rooflight and small water pump to sink. Also what does 1 in 2 out or 1 in 3 out mean. He is becoming a slight pain in the butt, so I would like to identify the right diode and get it fitted soon as possible. So once again thanks for your help hope you can identify the right one for me to order.

If the alternator is 85 amp, he really should use a 90 amp diode as the diode carries the maximum current not only to the additional battery, but also to the starter battery. Although the alternator doesn't produce 85 amps all the time, any short periods of over current can damage a smaller rated diode.
The 1 in 2 out is how it would be wired. So 1 in 2 out would be one alternator with two batteries (isolated from one another). A 2 in 3 out would be used where you have two alternators (two engines on a boat) feeding up to three isolated battery banks. So a 1 in 3 out is one alternator with three isolated battery banks.
If you fit a 1 in 2 out and disconnect one battery bank, do ensure the 'flying' battery lead from the diode is insulated to prevent it touching anything. It will be dead when the engine is not running, but you'll have sparks everywhere if left flopping around when the engine is running.
When it comes to the second battery, fit a tractor or lorry battery as it will be cheaper and charge quicker than any leisure battery.
You'll find helpful circuits here -

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