<VV> 12 volt heaters.........400 watt?

[Frank DuVal]

Notes inserted below:

PatioMatt at aol.com wrote:

> 
>In a message dated 12/5/2008 1:47:24 P.M. Pacific Standard Time,  
>corvairduval at cox.net writes:
>
>Matt, so how do the golf cart batteries recharge? If from the  car
>alternator/generator, you still only have a source of 30 to 37 amps  
>=========================================================
> 
> charge??  just like a Motor Home!!  millions of units out  there working 
>fine!
> 
>1  A battery isolator [ diode!]
> 
>  2 - 6 volts in series = 12 volts...  Heater  wired to THEM!!   not the car  
>[ think coach batteries!]   Coach goes dead.. but RV's engine still cranks 
>and starts!
>  
>

This requires two diodes. One for each battery fed from the charging 
source (alternator). If only one diode is used, the current path from 
one battery still feeds the second battery, but not vice versa. So there 
is only isolation for one case (one battery going dead, not two, and the 
dead battery is the one connected to the charge source). I do have some 
of these special dual diodes made by Motorola a few years back that are 
perfect for one charge source, two battery systems. Good for 100 amps or 
more.

> 
> 
>2  KEY  is RESERVE CAPACITY!
> 
> 
> We have no idea how long the heater will run each drive...   what 
>conditions, etc...
> 
> IF  he were to run out on the way to  work... then 4  Batteries!  [ very 
>unlikely! ]
> 
> 
> To charge a 200 amp hour system...  from fully discharged.. at  30 amps 
>would take approx. 10 hours!! [  nothing is 100%  efficent!  ]
>  
>

And they (200 amp hour) will also run the heater for about 5 hours full 
on (figure you can't fully discharge the batteries and get much heat out 
at the end of the cycle). Should be long enought for any commute. Even here.

> 
> BUT  the batteries will start out fully charged...
>  
>

If you plug them in at home.

> 
> draw may be 30 amps....   but cars alternator, running  everything else is 
>only sending 15 amps to GC  batteries....
> 
>That's only a 15 amp  draw!   / 200  AH     13 Hours!! before batteries run 
>down!!
>  
>

Sound do-able. But if the commute is short, say 15 mins to a half hour 
(like most everywhere except So CA and around Washington DC), then with 
wipers, headlamps, ignition, [I guess I can't count the stock fan motor 
current since we aren't using it, darn] there will be not much left for 
recharging. This was the basis for my comment. Plugging in the batteries 
at home eliminates this problem, and kinda makes a Hybrid car! ggg   
Best of both worlds.  Hmm, just eliminating the stock fan motor 
{especially the replacement high volume model} may give enough 
recharging capacity.

> 
>AND a 60 amp Alt.  is super cheap and a bolt on!
>  
>

This of course is the obvious cure. And I did suggest it. But I was 
speaking of stock components to make it harder to do! ggg


Now for someone to run a heat loss calculation to see how many watts/BTU 
is needed to heat a Corvair passenger compartment in (insert your local 
mean winter temperature here) degree weather. I'm going to guess 400 
watts would only supplement the stock heater, not replace it.


Frank DuVal