12v Diode Splitters

C

ctelfer38

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www.classic-cruising.com
A query for the electrical circuit experts on here. Having solved earlier battery power questions through advice on here, I return with another problem.
Firstly the system
I have a Volvo Penta 2003 engine with standard alternator feeding an input to a 70 amp Volvo Penta diode splitter sending a charging current to two battery banks. Domestic bank is 2X80 amp deep cycle and Engine bank is 1x105 amp starter battery.
I have an AC mains 11 amp charger for battery maintenance when alongside.
The splitter shows a drop of .56 from input to output which I believe is normal.

The problem.
The charger does not 'see' the batteries when connected through the splitter and will work only when the splitter is bypassed. On the one hand I understand why, as the spliitter should not let current flow back from the output post to the input. On the other - how can the charger be connected so that the splitter can do its job? What do others do?

Thus far I have identified three solutions, none very elegant.
1. Revert to a 1/2/All/Off manual switch.
2. Rig two battery chargers.
3. Change to a mains charger which does not need to 'see' the batteries before commencing charge.

Are there better solutions I have not identified?

Comment welcomed.
CBT
 
Why are you putting mains charger through diode splitter ?

You can buy a relay or electronic splitter from maplins that will auto divide the charger to whichever battery bank is needing charge.
But note that many 'clever' mains chargers will not work with splitters as it confuses the chip controled charger circuit. It wants to see the battery and decide about dropping to float charge or kick up to full charge. The splitter interferes with this function.
Answer I found was a bog standard non-clever charger ... to control it and stop over-charging ... I put it via a mains plug in timer.
 
A normal mains charger will not work well through a diode splitter. Even if it does start charging it will still not be set up for the voltage drop across the splitter.

I have a diode splitter for charging by the alternator (which is battery-sensing) but when using a Halfords mains charger I connect directly to the batteries - if necessary I connect it to both banks using the "emergency" position joins the domestic and engine batteries.

As an alternative in most cases there is no need to use a mains charger to recharge the engine battery so you can use the mains charger directly connected to the domestic bank.

You don't give the complete details, but you should not really be using a diode splitter without using a "battery sensing" alternator or regulator. The voltage drop across the splitter will ruin the charging and eventually significantly reduce the battery life.
 
For replacing a diode splitter, an X-split, here http://www.dg2k.co.uk/xsplit.htm, provides a good solution. Virtually zero charging voltage drop and complete isolation of the battery banks from each other. Different charging systems can be paralleled through them to the batteries, so it solves that problem. I have used one for years with complete satisfaction. Must be better than clunky old relays etc IMHO.
 
How about connecting a 56k Ohm to 1Meg Ohm resistor (value ½ to 1 Watt) across the Diode pack. This would allow the 'back' voltage that the charger requires to 'see' without passing too much current. The charger would / should then charge 'through' the diode pack? ;)

You could even put a 1Amp in-line fuse in there for piece of mind. :p
 
Although the XSplit is a good product it would not directly solve the OPs problem as the charger would probably still not detect the batteries and so still not start charging.
 
Just charge the house bank and then have a parallel switch for the start circuit if you need it. Better still buy a proper charger which will charge more than one battery at the same time. A 25 amp charger would be more appropriate for your capacity.
 
I'm not sure whether your question is related to alternator charging or mains charging? A mains charger should be connected directly to the batteries. The diode should only be used for the charge from the alternator. Can you elaborate?
 
12v Diode Splitter

Reply to all. Thanks folks. Your replies prompt me to try the following.
1. To uprate Mains charger to 25amps.
2. To divide the output from the Mains charger - with an on/off switch between the two and connect to each battery bank - probably via the outputs from the Volvo splitter - anyone see a problem with the latter?
CBT
 
Last edited:
ctelfer38 said:
Reply to all. Thanks folks. Your replies prompt me to try the following.
1. To uprate Mains charger to 25amps.
2. To divide the output from the Mains charger - with an on/off switch between the two and connect to each battery bank - probably via the outputs from the Volvo splitter - anyone see a problem with the latter?
CBT
Click to expand...

If you are going this route then consider a BEP Marine switching system with separate switches for each bank, a parallel and a VSR. Mains chargers usually have outputs for at least 2 batteries Have a look at Merlin www.power-store.com Other specialists have similar things but they offer a good range and lots of information.
 
Tranona said:
If you are going this route then consider a BEP Marine switching system with separate switches for each bank, a parallel and a VSR. Mains chargers usually have outputs for at least 2 batteries Have a look at Merlin www.power-store.com Other specialists have similar things but they offer a good range and lots of information.
Click to expand...

The OP could fit one of our small VSR's, that can be interfaced to the engine.

Which means the original diode splitter can remain, the existing charger can stay.

The VSR will charge the engine battery from the charger, the trip level can be set to suit the charger voltage. If the engine is started, the VSR will locked out, and the diodes splitter used, as it appears to work ok. Turn off the engine, and the VSR comes back on line.

Why do we make little problems so big and expensive.

Brian
 
Last edited:
12v Diode

Tranona said:
If you are going this route then consider a BEP Marine switching system with separate switches for each bank, a parallel and a VSR. Mains chargers usually have outputs for at least 2 batteries Have a look at Merlin www.power-store.com Other specialists have similar things but they offer a good range and lots of information.
Click to expand...

Tranona - That is a very useful link. Thanks to you - and the others. As always this forum comes up with the goods. Time for me to retire and research further on all of these options.
CBT
 
If you go for a BEP VSR system which has the 3 switches, I'd definitely recommend it as we have installed it many times but please, please take out the diodes. There is nothing worse than having a redundant, non-functioning and inferior system still screwed to a bulkhead after its use has long past.

The BEP switch cluster with VSR has redundancy built-in as if the VSR fails, you can use the emergency parallel to charge both sets of batteries.


Mark
www.boatdoctorni.com
 
markdj said:
If you go for a BEP VSR system which has the 3 switches, I'd definitely recommend it as we have installed it many times but please, please take out the diodes. There is nothing worse than having a redundant, non-functioning and inferior system still screwed to a bulkhead after its use has long past
Click to expand...

The OP says he has the Volvo diode splitter, which were mounted on the alternator, and battery sensed, so normally worked.

If he has one, and never had a problem, why is everyone spending his money ?

Okay if he has machine sense, and normal diodes fine replace them.

But you can get his current mains charger charging both batteries for around £35 / £40, and that was his original problem. Plus with his small battery bank size his 11 amp charger is adequate to maintain them, so why a 25 amp one.

All that cost, yet the forum spends most of it's time moaning about the cost of boating, funny old world.

Brian
 
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