 | Home > Maintenance & Modifications > Selectable Twin battery setup with VSR |
 
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8152   
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i am planning on leaving a 90 for long ish periods where it wont be started/cant be plugged in to a charger.
i would like to leave the vehicle battery connected. Would also like it to start when i need it To overcome this i have fitted a durite three way switch to allow Battery A only Battery B only Battery A and B combined. Batts are fitted in parallel through the switch. General driving around would be on A&B so both batteries are being charged. when due to be left for an extended period i would change it to 'A' on returning if the vehicle didnt have enough 'juice' in 'A' to start i could switch it to 'B' to start the vehicle then swtich back to A&B to charge both batts. As others will be using the vehicle and thinking of the simplest way of doing it (as they may not remember to put it back to 'A' from A&B when leaving for extended period) i was wondering if i could fit a VSR between A and B without going through the switch? You could then leave it on 'A' the whole time other than switching to 'B' to start if 'A' was too low. then switch back to 'A' So on 'A' it would charge 'B' through VSR when the voltage was high enough (engine running) but disconnect 'B' when turned off. Question is if it was switched to A&B through the three way switch what would it do to the VSR if both batts had 14.2v coming in not via VSR and VSR was between two +ve terminals of 'A' and 'B' the three way switch https://www.ebay.co.uk/itm/111817493774 which is an MBB for A to A&B to B. Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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28th Nov 2018 9:05am |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971  
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That shouldn't be an issue. The VSR will detect the high voltage, combine then you've got two current paths between the batteries.
The other option would be a VSR that's got a jump start facility like the Victron Cyrix series. Most of the time you're starting on Battery A, if Battery A is weak then push the manual link button and start from the combination. |
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28th Nov 2018 10:10am |
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| SteveG Member Since: 29 Nov 2011 Location: Norfolk Posts: 663 
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Wouldn't a simple isolator switch on the pos feed between batteries do the same thing? Turn on switch for normal operating mode with both batts connected and being charged.
When your leaving the 90 for long periods, just isolate battery B. Then when you want to use it again use the switch to connect both batteries together again, in case battery A doesn't have enough juice. Cheers steve |
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28th Nov 2018 4:43pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8152
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yep but then your draining B to A Steve, simialr to jump start only that B isint getting 14.2V into it at the time of switch Cheers
James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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28th Nov 2018 6:43pm |
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| miker Member Since: 13 Sep 2015 Location: Surrey Posts: 1768 
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A vsr like the victron cyrix (with the manual link button) is perfect for this application. The durite switch isn't necessary.
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29th Nov 2018 6:48am |
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| rallysteve Member Since: 10 Feb 2014 Location: Cumbria Posts: 2238 
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I run an albright HD isolator connected between my two matching batteries. This isolator is actuated by either a VSR which runs on the main battery side and connects both batteries to charge when the engine is running.
I also have a manual override switch which allows me to self jump start in the event that the main battery is flat or for use of both batteries whilst winching. My manual switch is connected to both batteries so that the relay can still be operated if either battery is totally flat. Steve 02' 110 TD5 Double Cab Rebuild Thread |
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29th Nov 2018 7:32am |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8152
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So the victron allows two Batts to work independently too?, a, b or a and b? Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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29th Nov 2018 7:51am |
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| JOW240725 Member Since: 04 May 2015 Location: Suffolk Posts: 7908 
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This all goes over my head but I wonder if a small solar panel would be an option to top up the batteries whilst left? My father used to leave a panel in the back window plugged into the cigerette lighter, which was enough to keep his RR ticking over. James
MY2012 110 2.2TDCi XS SW Orkney Grey - http://www.defender2.net/forum/topic43410.html MY1990 110 200TDi SW beautifully faded Portofino Red - https://www.defender2.net/forum/post743641.html#743641 MY1984 90 V8 Slate Grey - https://www.defender2.net/forum/post744557.html#744557 Instagram @suffolk_rovers |
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29th Nov 2018 9:58am |
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| rallysteve Member Since: 10 Feb 2014 Location: Cumbria Posts: 2238
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No its A or A+B. I am a bit confused why you want to be able to select A or B. If A (main battery has gone flat) then you would just want to connect A and B to get an effective jump start. I would want the 400A version of that type if you want to use it for cold cranking. Steve 02' 110 TD5 Double Cab Rebuild Thread |
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29th Nov 2018 10:07am |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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The 230A one is rated at 500A for cranking so should be enough.
I don't know about the cheapo VSRs, but much of the decent ones are "dual sensing", that is they don't care which is the starter battery and which is the auxiliary battery. Once the relay has closed it won't make any difference which way the current is flowing, it's just a piece of metal. |
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29th Nov 2018 12:19pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8152
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mainly because if A is really dead i dont want B just dumping charge into it and then not having enough to start the vehicle. If B is totally isolated and can be started without connecting to A this wont happen. When you jump off another vehicle the other vehicle is usually running. i have found with a really flat battery i have had to leave the other vehicle (the jumper) running to help trickle the dead battery before the dead vehicle (jumpee) will start as the dead battery is taking all the 'grunt' from the running vehicle. Trying to eliminate this Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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29th Nov 2018 9:16pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8152
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OK thank you that is key part i was after knowing. Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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29th Nov 2018 9:17pm |
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| SteveG Member Since: 29 Nov 2011 Location: Norfolk Posts: 663
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You could put isolators on both negative feeds of both batteries. Isolate B if leaving it for a long period and still need power for alarm etc. In the event that A is drained, isolate A, switch B back and start, then when it’s running switch A back. If you don’t need the auto switching of a VSR, in your use it doesn’t seem like you do, then the expense of a VSR with a manual switch appears to be unnecessary. |
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30th Nov 2018 7:53am |
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