Aux. battery & split charge.

[RMS]

Ian,

No, you don't need an isolator for the aux feed, just make sure the +ve terminal lead is fully insulated when you disconnect the battery so it can't touch to earth

Rob, if you use an auto sense type, you don't need a feed from the engine bay or dash, it just connects between the two batteries so easy-peasy

Michiel, again, if you use an auto-sense type you don't need to find a trigger feed from the regulator. As Ian says, just pick up a main feed from the battery, dynamo or starter switch

Cheers,
Robin.

[DrivingDutchman]

thanks for the advice gentlemen... Thats good news.

Michiel

[Dormy]

I have found the parts/info required to change an ACR alternator to battery sensing and hope it is of use to some: -

http://www.jcrsupplies.co.uk/products/A ... dvert.html

http://www.jcrsupplies.co.uk/products/A ... dvert.html

http://www.mgexp.com/phorum/read.php?1,2135169

You will need to scroll down through the mg forum a little to find the wiring. If the rectifier in my spare alt. isn't fried then I won't replace it but will run the necessary wire to the battery externally. This will leave the second big spade terminal free for my aux. battery connection.

I will probably use the 30amp auto-sensing relay as it is seems cheap enough. If it packs-up then it will be replaced with a simple relay.

[Dormy]

Found a schematic wiring diagram for a 17acr with 4 wire regulator (in a S3 maintenance manual as it happens).

The white (batt. sensed) and red (machine sensed) are wired parallel with a resistor introduced in series in the red wire. Unfortunately it doesn't give a value for this resistor but if I can access it I can measure it. Makes me think I can add a similar sized potentiometer to the white wire to fine tune the charging voltage. Shouldn't be possible to overcook things as the red wire would always act as a fail-safe.

Don't know if it will be worth the effort (though they have them on boat split-charge systems) so will try it without first and see how it goes.

Ian

[RMS]

Hi Ian,

This is the sort of thing I would probably have played around with in my younger days as I have a background in electronics, but these days tend to wonder if it would be worth it?

You won't get any extra current out of the alternator, and the standard machine/self sensing ones are fairly well regulated, I think.
What's half a volt here or there, unless you are running sensitive electronics/inverters etc.

I think you might be introducing more possible problem areas, especially if you need an emergency replacement in the middle of a trip, but that's just my 'current' opinion

Cheers,
Robin.

[Dormy]

Hi Robin,

I agree about going to too much trouble - diminishing returns and all that. I know you can never get more than the rated amps from the alternator, but I just want to ensure the leisure battery is full as it can be. According to the boat forums that 1/2 volt or so can actually make a lot of difference.

Whatever changes I do make it won't stop me being able to fit the bog standard alternator back on if this one eventually fails.

Regards
Ian

[RMS]

Ah yes, I can see how something like a yacht which uses an engine to charge batteries might need to optimise the charge as they want to minimise the time the engine is run and want to make sure the batteries are 'topped off'.

I'm still to be convinced that it would make a lot of difference to ours though.

Presumably most of our driving will be daytime, without headlights, so the voltage from the standard alternator should get up to max anyway, shouldn't it?

I'll have a look at the boat forum links Lynall supplied over on the S2C forum when I get time, to get my head around the advantages

Cheers,
Robin.

[Dormy]

Hi Robin,

Not just yachts but cruisers too, (and there are plenty in Norfolk) which run their engines whenever moving. Admittedly they have much bigger electrical loads and consequently much bigger battery banks.

Part of the problem last year after I managed to run down Dormy's battery was getting it to recharge to a reasonable level. The trips we were making (and I deliberately did a longer circular run) just weren't enough to get the battery back up. Consequently, using the Waeco the following night (even with the switch in the correct position) still left the battery unable to start the engine.


Neither the Esterel nor Dormy have space for a big leisure battery, so I will want the fairly small one I will probably have to fit to be charged as much as possible - once bitten twice shy, or am I being paranoid !


Regards
Ian

[RMS]

Just to add a little note to this, it might be worth considering a decent sized solar panel to supplement the auxilliary battery if you're staying in the same place for more than a couple of days.

Something like THIS.

A 60W panel, with controller, would (in ideal conditions!) produce around 4A of charge, all day while there is daylight not just sunshine, which should be sufficient to supplement the battery.

At 771 x 676 x 35 mm it should fit nicely on top of a roof rack box.

Obviously there are more powerful ones available, but the sizes can get a little unwieldy

Cheers,
Robin.

[Dormy]

You have just reminded me I bought a couple of these from Maplins when they were on special offer ( probably around Nov.)

They are probably at the smaller end of the output scale but must dig them out and sort out wiring them in.

Thanks
Dormy