| Author |
Message |
Brian Brown (Fishbowlbrian)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 11, 2005 - 5:21 pm: | |
Sorry for my ignorance in these matters, but basically I need to bring in an isolator [it's a Vanner Schottky 250A] into the charging circuit. The bus presently doesn’t have a means to charge the house batt without running the genset (through an old RV converter).
At the moment, I have an aftermarket one-wire (AFAIK)130A/ 14v alt that charges the coach side, so I was planning on splicing in the existing charging wire into the isolator’s center tap, put the coach batts on leg #1 of the isolator, and the house batt on leg #2. The run from the isolator to the house batt is about 20’. Some questions:
Do I calc. the voltage drop for such a run with the whole 130A? In other words, does the batt ever “take” that much or only when it’s discharged?
And how does the isolator know how much to “give” to each bank?
If it takes the whole 130A, the charging wire would be pretty freaking huge! I’m not averse to running a #0 if I have to, since I don't want it to overheat or have a serious voltage drop.
I’m still saving for a Trace Inv./Chg. that will solve a lot of these issues.
Thanks!
Brian Brown
PD4106-1175
Longmont, CO USA |
Jerry Liebler (Jerry_liebler)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 11, 2005 - 9:01 pm: | |
Brian,
You shouldn't use a diode type isolator with a 1 wire alternator. With the 1 wire the regulator is inside the alternator and it is set to charge the battery to about 13.8 volts. The isolator will add a voltage drop of about 1/2 volt which means niether battery will ever get more than 1/2 charged. To use the diode isolator you need an alternator that uses an external regulator and the regulator needs to sense the battery voltage after the isolator. The alternator will be controlled by the voltage on the sensed bank but it's output will divide to fully charge both batterys eventually. If this is a 4106, didn't it have a gear driven alternator that uses an external regulator and has an 'r' terminal? With the 'r' terminal it's easy to use a contactor as an isolator and avoid the heat and issues with diode isolators. Regarding the wire size bigger is better, make that 20' run at least 2 AWG, I'd prefer 00, and don't forget the ground side wire should be as large.
Regards
Jerry 4107 1120 |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 11, 2005 - 9:36 pm: | |
I dunno Jerry... But both RVs we owned had an alternator
with a self-contained regulator, and both had a diode type
battery isolator that kept the house and engine batteries well
charged.... and from depleting each other during use...
Am I missing something? |
Brian Brown (Fishbowlbrian)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 11, 2005 - 10:15 pm: | |
Jerry, I got the Schottky isolator because it has a very small voltage drop... 0.2v or so. Also, I can adjust the regulator on my alternator to compensate (presently at 14.4v, which is probably too high). It's an old Leece-Neville unit that someone went to a lot of trouble to put in place of the gear-driven stock model (must have died). I wish it still had the bigger stock alt., though.
I'll follow your recommend, though, and run some big honking wire.
Thanks,
BB |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 06, 2005 - 12:37 am: | |
Brian, as the charge tapers off because the batteries start to become charged, the drop in the long wire to the house batteries will play less and less of a role.
The most significant effect of the long wire's drop will be that it will add somewhat to the full recharge time. If will not affect the complete recharge if there is sufficient running time on the charging system, unless you reset the voltage regulator to make up for it. Don't.
It's a conservative practice to provide a big enough conductor to handle the full output of the alternator indefinitely. Be sure to ventilate the isolator, as well.
If you check available wire ratings, I think you will find that you can use #0 without worry.
The other thing to think about is whether you will ever want to sent boost current for your starter over that conductor. If so, consider that your starting bank might provide very little power, so that the full starting current might run through this conductor.
The reason for allowing for full starting current is because of the possibility that the engine might crank slowly, which will greatly raise the starting current.
Your call.
Tom Caffrey PD4106-2576
Suncatcher |
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