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70 Posts
Discussion Starter #1
It looks like my adaptor plate should be finished this week and shipping ne=
xt week, so it's going to be time to really get busy and finally get my lit=
tle Datsun truck on the road. I could use some input on the 12 volt system.
=

The first option I am considering is building a 14 volt house battery. Sin=
ce I am using BB600 cells this would be simple and give me up to 40 ahrs of=
power. I have lights, a couple of contatctors, a heater blower, a blower =
for cooling my motor and windshield wipers to potentially run off this. I =
think a fully charged battery should give me a full hour of run time even i=
n a worst case scenario, and since these are NiCads they should hold a nice=
steady voltage. The downside to this approach is that I could potentially=
run this battery down and find myself stuck, of course with a set of jumpe=
r cables I could jump my house battery from my main pack and be on my way I=
suppose.
=

The next option would be to add a small DC/DC converter. I even have one t=
hat is rated 36 - 72 volts and 17 amps. It is the twin to the one I use on=
my motorcycle. I could set the voltage to a level that would kick in if t=
he house battery begins to sag under load. The problem with the one I alre=
ady have is that I am planning on running my main pack at a bit over 72 vol=
ts nominal (66 1.2 volt cells), and I'm not sure how the DC/DC will like th=
is.
=

The last option I have been considering is a voltage doubler to feed a regu=
lar proven EV style DC/DC like an IOTA. This has a few advantages that I l=
ike. First, there is a good chance that this truck may end up at 144 volts=
in the future at which point I could just remove the voltage doubler. I'm=
going to try the truck at 72 volts for now and see how I like it. Second,=
this option feels like a complete solution, where the others feel like the=
y are just adequate. The main problem is that I don't know what it takes to=
build a voltage doubler, although I'm under the impression that they are f=
airly simple circuits, but perhaps they are a bit trickier at these current=
levels. If the DC/DC is good for 40 or 50 amps that means the voltage dou=
bler would have to be built for twice that.
=

Any comments appreciated. Or if you know of a good DC/DC that that operate=
s well in the 60 - 90 volt range and that is easy to work with and readily =
available let me know.
=

thanks
damon
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70 Posts
Discussion Starter #2
You can put 2 or more diodes in series between the pack and input to =

your dc/dc to lower the voltage. I am using 2 bridge rectifier on my =

Astrodyne 72 volt dc/dc to keep it from kicking out on overvoltage, =

dropped the voltage down about 3-4 volts.
Bill

damon henry wrote:
> It looks like my adaptor plate should be finished this week and shipping =
next week, so it's going to be time to really get busy and finally get my l=
ittle Datsun truck on the road. I could use some input on the 12 volt syst=
em.
> =

> The first option I am considering is building a 14 volt house battery. S=
ince I am using BB600 cells this would be simple and give me up to 40 ahrs =
of power. I have lights, a couple of contatctors, a heater blower, a blowe=
r for cooling my motor and windshield wipers to potentially run off this. =
I think a fully charged battery should give me a full hour of run time even=
in a worst case scenario, and since these are NiCads they should hold a ni=
ce steady voltage. The downside to this approach is that I could potential=
ly run this battery down and find myself stuck, of course with a set of jum=
per cables I could jump my house battery from my main pack and be on my way=
I suppose.
> =

> The next option would be to add a small DC/DC converter. I even have one=
that is rated 36 - 72 volts and 17 amps. It is the twin to the one I use =
on my motorcycle. I could set the voltage to a level that would kick in if=
the house battery begins to sag under load. The problem with the one I al=
ready have is that I am planning on running my main pack at a bit over 72 v=
olts nominal (66 1.2 volt cells), and I'm not sure how the DC/DC will like =
this.
> =

> The last option I have been considering is a voltage doubler to feed a re=
gular proven EV style DC/DC like an IOTA. This has a few advantages that I=
like. First, there is a good chance that this truck may end up at 144 vol=
ts in the future at which point I could just remove the voltage doubler. I=
'm going to try the truck at 72 volts for now and see how I like it. Secon=
d, this option feels like a complete solution, where the others feel like t=
hey are just adequate. The main problem is that I don't know what it takes =
to build a voltage doubler, although I'm under the impression that they are=
fairly simple circuits, but perhaps they are a bit trickier at these curre=
nt levels. If the DC/DC is good for 40 or 50 amps that means the voltage d=
oubler would have to be built for twice that.
> =

> Any comments appreciated. Or if you know of a good DC/DC that that opera=
tes well in the 60 - 90 volt range and that is easy to work with and readil=
y available let me know.
> =

> thanks
> damon
> _________________________________________________________________
> Help yourself to FREE treats served up daily at the Messenger Caf=E9. Sto=
p by today.
> http://www.cafemessenger.com/info/info_sweetstuff2.html?ocid=3DTXT_TAGLM_=
OctWLtagline
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> =


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Discussion Starter #3
Hey, thanks. That's a great idea and one that I hadn't considered even tho=
ugh I have used the same trick before for other things :)

damon

> Date: Thu, 25 Oct 2007 09:11:55 -0700
> From: [email protected]
> To: [email protected]
> Subject: Re: [EVDL] Finshing it up DC/DC
>
> You can put 2 or more diodes in series between the pack and input to
> your dc/dc to lower the voltage. I am using 2 bridge rectifier on my
> Astrodyne 72 volt dc/dc to keep it from kicking out on overvoltage,
> dropped the voltage down about 3-4 volts.
> Bill

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70 Posts
Discussion Starter #4
Hi Damon,

I think voltage doublers only work on AC when
rectified to DC. So would not work off the battery.

Jeff M


--- damon henry <[email protected]> wrote:

>
<snip>
> The last option I have been considering is a voltage
> doubler to feed a regular proven EV style DC/DC like
> an IOTA. This has a few advantages that I like.
> First, there is a good chance that this truck may
> end up at 144 volts in the future at which point I
> could just remove the voltage doubler. I'm going to
> try the truck at 72 volts for now and see how I like
> it. Second, this option feels like a complete
> solution, where the others feel like they are just
> adequate. The main problem is that I don't know what
> it takes to build a voltage doubler, although I'm
> under the impression that they are fairly simple
> circuits, but perhaps they are a bit trickier at
> these current levels. If the DC/DC is good for 40
> or 50 amps that means the voltage doubler would have
> to be built for twice that.
>
> Any comments appreciated. Or if you know of a good
> DC/DC that that operates well in the 60 - 90 volt
> range and that is easy to work with and readily
> available let me know.
>
> thanks
> damon
>

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Discussion Starter #5
damon henry wrote:

> Any comments appreciated. Or if you know of a good DC/DC
> that that operates well in the 60 - 90 volt range and that is
> easy to work with and readily available let me know.

Check out Surepower <http://www.surepower.com/>; they're in your area and have good DC/DCs. The 71030i (used in GEM NEVs) delivers [email protected] and works with battery packs from 72-96V nominal.

As others have noted, a voltage doubler works on AC only. If you have a 30A output DC/DC delivering 12V from 144V input, then it draws about 2.5A @ 144V, or about 5A @ 72V on the battery side of a voltage step up device. This is far more managable a current level than you had thought. While a voltage doubler would not work, it is possible to use a vibrator circuit to chop the 72V DC allowing it to be stepped up by a transformer. I would suggest that unless you have lots more time than money you would be much better off to just buy a SurePower DC/DC and know that it will just work ;^>

Cheers,

Roger.



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Discussion Starter #6
Thanks Roger,

Not only is SurePower a local company based here in Portland, but they list=
Wrangler NW as one of their distributors. Wrangler NW is a local company =
that John Wayland introduced me to a couple of years ago. They stock all k=
inds of wire and connectors and are very EV friendly. I was already planni=
ng on putting in an order with them for my cables and connectors. I contac=
ted them and they quoted me $238.61 for the DC/DC. They are checking on le=
ad time, but I am pretty sure that I wil be getting one.

damon

> From: [email protected]
> To: [email protected]
> Date: Thu, 25 Oct 2007 11:58:56 -0700
> Subject: Re: [EVDL] Finshing it up DC/DC
>
> damon henry wrote:
>
>> Any comments appreciated. Or if you know of a good DC/DC
>> that that operates well in the 60 - 90 volt range and that is
>> easy to work with and readily available let me know.
>
> Check out Surepower ; they're in your area and have good DC/DCs. The 7103=
0i (used in GEM NEVs) delivers [email protected] and works with battery packs from =
72-96V nominal.
>

_________________________________________________________________
Help yourself to FREE treats served up daily at the Messenger Caf=E9. Stop =
by today.
http://www.cafemessenger.com/info/info_sweetstuff2.html?ocid=3DTXT_TAGLM_Oc=
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