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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