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bru6ey
bru6ey

Posted: Sat Dec 27, 2014 11:34am

Post Subject: battery charging

Hello again I am looking to connect both alternator supplies to both battery banks to give extra charging to the domestic batteries as the starting alternator is under used just charging the starter battery the alternators are 70 amp and the domestics are 3 110amp plus a 110amp starter battery any advice thanks Bruce

bru6ey
bru6ey

Posted: Sat Dec 27, 2014 11:55am

Post Subject: battery charging

Just to add the domestic alternator has a sterling alternator regulator fitted thanks

Tony-B
Tony-B

Posted: Sat Dec 27, 2014 1:36pm

Post Subject: battery charging

I think that you need to carefully consider if any advantage this may yield is worth the effort. Assuming your battery bank size, alternator size, and electrical load are tolerably well matched and you are not over-discharging your batteries then the advantage you hope to gain is likely to only be present for an hour or so - or even less. Once the charging voltage has risen high enough for the voltage regulators to start to work one alternator may shut down possibly causing a warning lamp to glow. Sterling sell an Alternator to Battery charger that is designed to combine both alternator outputs and deliver it to both battery banks. The electrical notes on my website (tb-training.co.uk) has a diagram for using a split charge relay to combine both banks so both alternators charge then. However the problems I detail above are likely to occur. Nowadays I would suggest that you energise the relay by a switch so if one warning lamp starts to glow or if the domestic alternator shuts down you can turn the relay off so the system returns to "normal". To be honest I suspect what you gain may not be worth the effort or expense. It may give better long term results if you put the cost towards as much solar charging as you can afford. Have you done a power/energy audit and the charging calculations described in both sets of course notes (the maintenance notes are probably better). That will allow you to better understand what is going on. It would also be worth doing research on what limits battery life and the phenomenon known as sulphation. Then read up on battery testing.

Tony-B
Tony-B

Posted: Sun Dec 28, 2014 7:47am

Post Subject: battery charging

I think I should have pointed out that if you simply join both alternator man output leads you will in effect join your engine battery to your domestic bank so your domestic loads discharge both banks when the engine is stationary. This can easily lead to an inability to start the engine to recharge the batteries. Hence the use of a relay that automatically disconnects when the engine is stopped.

bru6ey
bru6ey

Posted: Sun Dec 28, 2014 9:20am

Post Subject: battery charging

many thanks for reply will leave well alone Happy New Year to you Bruce

Tony-B
Tony-B

Posted: Tue Dec 30, 2014 4:33pm

Post Subject: battery charging

I have just had a thought. If you want a cheap and easy way to test if paralleling the alternators actually makes a significant difference to charging time just use a heavy jump lead to join the engine battery positive and domestic battery positive once the engine is running. Remember to remove it as soon as you have stopped the engine. That will show how much faster the batteries are charged and also show if any warning lamp problems are likely. It would be bets if you have seem form of ammeter on the domestic circuit so you can see how long it takes to drop to about 2 to 2% of battery capacity (4 to 8 amps. This is more or less fully charged, but may take along time.

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