The Sure Power 1315 can be wired to use a separate switch to combine the
batteries for starting, such as you did (works only when you want it
to), or it can be wired to the ignition/starter switch in which case it
would combine the batteries every time you use the starter.

Mike

Reinhard Vehring wrote:
> I'm running two yellow Optimas with a Sure Power 1315
> for more than two years now. Works great. Nice thing
> about the 1315 is that you can bridge it with a flip
> of a switch (which I put on the dash next to my two
> voltmeters) I've used that more than once to start the
> van after I've stupidly left the lights on (yes, I
> know, memory fades with age). Beats jumpstarting the
> rig :-) Especially if the next guy to get a jump start
> from is 100 miles away...
> Have fun,
> Reinhard
>
> 83 "Half-Syncro" Westy, Moose
> --- Dennis Haynes <d23haynes57@HOTMAIL.COM> wrote:
>
>> You went through a lot of trouble to basically do
>> what a battery combiner
>> or smart relay such as the sure power 1315 does. The
>> sure power uses a
>> wide range so that after cut out at 12 volts, it
>> will not cut back in
>> until one of the banks gets up to 13 volts which
>> would indicate a charge
>> source is now there. This set up arks great even
>> with a conventional
>> strting battery combined with deep cycles.
>>
>> Dennis
>>
>> -----Original Message-----
>> From: Vanagon Mailing List
>> [mailto:vanagon@gerry.vanagon.com] On Behalf Of
>> Martin Jagersand
>> Sent: Sunday, August 05, 2007 6:19 PM
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: T3 Westy's; batteries; how to have your
>> cake and eat it
>>
>> Hi,
>>
>> Following my dual 6V deep cycle install in a T4
>> Westy and the
>> recent flurry of battery emails to the list, I
>> started thinking of
>> what would be the best way to maximize deep cycle
>> Ah, while
>> minimizing space use in a T3 Westy.
>>
>> Removing the constraint of not converting storage
>> space into
>> battery space, one can of course put the tried and
>> true golf cart
>> size deep cycles in the locker under the bench seat.
>>
>> However, for many of us the under seat storage is an
>> important
>> locker to squeeze in bulky outdoor equipments, that
>> won't fit elsewhere.
>> For me so important so I even removed the heater in
>> there on my '85.
>>
>> So what remains to utilize are the two regular
>> battery lockers behind
>> drivers and passenger seats. One is already taken by
>> the starting
>> battery, and in the other one cannot fit a larger
>> than 55-70Ah
>> deep cycle. So what can one do to get 100+ Ah deep
>> cycle capacity?
>>
>> My proposed solution is to replace the typical
>> charge relay with a
>> battery voltage cut out relay (or "battery
>> protector"). That is one
>> of those devices that are advertised to protect your
>> starting battery
>> from discharging to a voltage below what's required
>> to start a car.
>>
>> Now instead of having one dedicated starting battery
>> and one deep
>> cycle battery, you need two deep cycle batteries
>> with enough CCA
>> to start your vehicle. They will be connected
>> together in parallel
>> for long periods, so they should be of same type and
>> age. (Otherwise
>> small differences in chemistry might make one
>> battery leak current into
>> the other, and thus parasitically discharge)
>>
>> Armed with a couple of 12V gel cell batteries (from
>> our robots at school),
>> a "battery protector" relay from Canadian tire, my
>> 1000W inverter, a
>> charger
>> and some test loads, I set out to test this idea.
>> (On the bedroom floor,
>> to
>> wife's dismay when she came home... I was quickly
>> booted out)
>>
>> I wired it together as follows: Battery 1 was wired
>> to charger and would
>> act as the starting battery in a vehicle setup.
>> Battery 2 was wired to
>> the inverter (and any other camping loads). The
>> "battery protector" was
>> set
>> up between the two batteries according to the
>> enclosed manual.
>>
>> In operation, it works like this: When charging, the
>> battery protector
>> puts both batteries in parallel, just like a dual
>> battery charge relay.
>> The difference is that when it stops charging, and
>> switches to
>> discharge during camping, the two batteries remain
>> connected,
>> but only until a certain voltage/discharge %-age is
>> reached. After
>> this, the relay cuts, and battery 1 becomes isolated
>> from battery 2.
>>
>> The experiment started well. Batteries both charged
>> up. I disconnected
>> the charger, and I could use the combined CA of both
>> to run loads.
>> On reaching 12V (corresponding to about 50% battery
>> capacity) the
>> relay would cut the connection as advertised on the
>> battery protector
>> box. Experiment successfully concluded I thought,
>> and prepared to
>> wrap up. Whoops, moments later, the battery
>> protector cut back in
>> again, then it would oscillate in and out, upping
>> and lowering the
>> voltage around the set point 12V, causing an alarm
>> buzzer to go off in the
>> inverter. (Alerting wife...)
>>
>> So what happened? When the battery protector cut the
>> connection
>> at 12 V, battery 1 that had been loaded, but now was
>> unloaded, would
>> recover after some time, voltage go up above 12V
>> again, and the battery
>> protector did exactly what it is supposed to do:
>> enable the connection
>> again.
>> Now being loaded, but not recharged, the voltage
>> would quickly drop below
>> 12V, causing the relay to cut, and this would go on
>> over and over again at
>> a
>>
>> rapid rate. (presumably until the battery was
>> discharged enough to remain
>> under 12V even unloaded)
>>
>> Not a pleasant effect! So how to solve? Turns out
>> the solution was
>> rather easy. Instead of having the negative "sense"
>> wire on battery 1, the
>> starting battery, (this is the normal setup as it
>> then measures the
>> voltage
>> of that "protected" battery.), i put the sense wire
>> on battery 2, the
>> camping battery. Now it worked great: When the
>> voltage dropped below 12V,
>> the relay would cut and separate the batteries.
>> Battery 2 remains loaded,
>> hence the sense voltage does not pop above 12V, and
>> the starting battery
>> remains protected, without any on-off oscillation.
>>
>> So end effect was that from my two 10Ah robot gel
>> cells got 10Ah while
>> both were connected, and another 5Ah from battery 2,
>> after disconnect,
>> while "protecting" 5Ah in battery 1. Scaling this to
>> two 70Ah deep
>> cycles (about the biggest size that can be squeezed
>> into the T3
>> battery boxes.), one would get 70Ah while in
>> parallel (at a very high
>> max current capacity, no problem to run your
>> cappuchino maker!),
>> then another 35Ah in single battery mode, making a
>> total of
>> 105Ah deep cycle capacity, and still fitting in the
>> standard spaces!
>> 50% remains in battery 1 for starting. (Other mixes
>> of starting/camping
>> Ah percentages can be had by varying  the cutoff
>> voltage.)
>> Like both having your cake and eating it...
>> An added bonus, is that in winter use (when we drive
>> to ski places,
>> but don't camp in the Westy), there is double the
>> CCA of one battery to
>> start the Diesel in my '82.
>>
>> Any cons? Well now both batteries will be cycled in
>> semi-deep cycle mode,
>> so the one used for starting will likely wear out a
>> bit faster than if it
>> had not been used for caming supply. On the other
>> hand, if the typical
>> use is using 70Ah or less, then the combined life of
>> both batteries
>> will be much better than if a single 70Ah deep cycle
>> was used to 70Ah,
>>
> === message truncated ===
>
>
>
>
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