Dual batteries

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timbeauford
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Dual batteries

Post by timbeauford » Thu Aug 01, 2019 4:53 pm

Hi.
So we have just bought a Bongo. Its a winter edition with two starter batteries. I want to swap the spare starter for a leisure battery. Is the second starter isolated from the main starter until you press the cold start switch? If it is can i get away with not putting in a split charge relay and simply stick in a leisure and rewire the fuse box to run internals from the leisure.

Cheers
Tim
Bob
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Re: Dual batteries

Post by Bob » Thu Aug 01, 2019 5:08 pm

Hi, and welcome.

No you can't is the short answer, the batteries work together. :wink:
timbeauford
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Re: Dual batteries

Post by timbeauford » Thu Aug 01, 2019 5:14 pm

Thanks Bob
Clears that up. Any recommendations on a good split charge relay brand?

Cheers
Tim
Bob
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Re: Dual batteries

Post by Bob » Thu Aug 01, 2019 6:36 pm

Mine's not converted and no LB so can't really help, but with luck Geoff, our electrical wizzard, will have some thoughts. :)
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g8dhe
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Re: Dual batteries

Post by g8dhe » Thu Aug 01, 2019 8:47 pm

Be aware that the two batteries are connected in parallel to the starter so when you disconnect the nearside battery the +ve connector
remains LIVE at all times so it needs to be well insulated and tucked well out of the way so that in a small front end collision it can't short to earth under ANY circumstances as there are NO fuses or otherwise you will have an arc welder flying free under the bonnet!
Geoff
2001 Aero V6, AFT, full side conversion.
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timbeauford
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Re: Dual batteries

Post by timbeauford » Fri Aug 02, 2019 11:36 am

Hi Geoff
Thanks for the advice. So being live constantly can I connect the the relay for the leisure battery to this cable instead of the main battery with a 12 volt power jointing box. Would make sense doing that as the cabling is aready in place.

Cheers
Tim
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g8dhe
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Re: Dual batteries

Post by g8dhe » Fri Aug 02, 2019 12:30 pm

No because there are no fuses in the cable the starter motor can take well over a 1000Amps in the first milliesecond or so! Your cables from each battery to the Split Charge Relay MUST be fused close to the battery (within a couple of inches) otherwise there not protecting the cable at all. The ideal situation is to physically remove that cable but to do that you need to take it off the starter motor and then bring it and its convoluted protector back out which is not an easy job as it passes thru the firewall etc.

You would be better off getting a proper quality Split Charge Relay kit from the likes of Karl https://www.ebay.co.uk/itm/Split-Charge ... SwgPBb5iIa
Geoff
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Alkers
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Re: Dual batteries

Post by Alkers » Fri Aug 02, 2019 1:59 pm

These are the best split charge setups going:http://www.smartgauge.co.uk/smartbank.html

See if you can get one on Ebay and get a 60A+ relay. A lot of the other relays advertised will not achieve anything near their labeled outputs.
timbeauford
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Re: Dual batteries

Post by timbeauford » Mon Aug 05, 2019 9:59 am

Great. Thanks for the advice. I will get one of Karls kits off Ebay.

Cheers
Tim
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