Review My Aux Battery Wiring Diagram?

[TommyBoyGomes]

Hi all,

I've installed the GoWesty aux battery kit into my '90 Multivan, but I now understand its limitations (low charging voltage for the aux battery) and would like to migrate to a better setup.

I'm moving to a setup that uses a thick gauge cable between the starting battery and the aux battery, so I've attached the below diagram for everyone's review to make sure I'm making the right changes. The diagram shows my existing setup and the proposed new setup that should give me much better charging voltages. I have several questions about this transition below for thesamba community because I'm not sure if I've shown all the wiring correctly:

Here are several questions about this setup (same questions as on the right side of the diagram):

1. I've installed an adjustable voltage regulator onto the alternator and I've adjusted it so that the starting battery is receiving 14.9V when the engine is at 4,000rpm. If I run 6-AWG cable from the starting battery to the aux battery, voltage drop calcs say that I'll be charging the aux battery at about 14.5-14.6V. The GoWesty Aux Battery Instructions say that their circuit breaker will trip if the aux battery receives more than 50A of charging current. Will this new setup exceed 50A now that the gauge of the charging wire is alot larger? I have the stock VW alternator.
2. Is the yellow cable in the GW kit the cable that's carrying the charge voltage? If so, can the 6-AWG cable from the starting battery take the place of this yellow cable in the GoWesty kit? Can I disconnect the yellow cable from the fuse panel and connect the 6-AWG cable from the starting battery to the post of the GW isolator where the yellow wire was previously connected?
3. Do the cables on both sides of the GW circuit breaker also need to be 6-AWG so that all cables going to the + post of the battery are 6-AWG?
4. Say I'm on a long trip and drive the van at highway speeds for 8 hours a day. Is it harmful to be charging the aux battery at around 14.5-14.6V for that length of time? My bat is the AGM battery from GW that has a charge rating of 14.7V. I know that when the solar charge controller is charging the aux battery, it has many different stages of adjusting voltage once the battery is full to ensure that it stays healthy. When the alternator is on though, this battery will see 14.5-14.6V of charge constantly for as long as the car is running. Is this ok?
5. Should I re-solder the red B11 and B12 wires to their original locations behind the fuse panel and use a male-spade connector on fuse #3 and send that to the + post of the Aux Battery? Wouldn't I need to add a fuse to here somewhere? If so, where and what rating should the fuse be? 15A or 20A?
6. If it's better to leave the red B11 and B12 wires in the GW 6-port splice connector, let me know.
7. The only reason I'm not considering a Yandina C100 is because it says that the Yandina will join the two batteries when either receive more than 13.3V. I don't want the batteries to be joined together when I plug in my solar panel (I only want to charge the aux battery). I'd rather the process be automatic.
8. Do I need to add any fuses along that 6-AWG cable inbetween the starting battery and the GW isolator?

Thanks for all the help!
_________________
1969 Squareback, 1776cc
1990 Vanagon Multivan

[jmranger]

14.9V at the starter battery

How to answer this? It's clear to me that you did a fair amount of reading. But as they say, "a little knowledge is dangerous". I feel that you're trying do design something overkill, and one possible outcome is an electrical fire. Let's try to avoid that.

A few random notes:
- Charging any regular lead-acid at that voltage will indeed charge it quickly, but with the consequence of boiling its electrolyte and almost certainly reducing its lifespan. Do you plan to check the electrolyte level weekly?
- If you have 14.9V at the battery, I wonder what kind of voltage you have in the engine bay - it'll certainly be above that. I don't know what kind of voltage is required to fry the ECU, but I'm asking you NOT to test it for us.
- You're not stating what chemistry/size your aux battery is, nor where it is located in the van. Optimal charge current/voltage depend on this.
- Regarding the super thick wire between both batteries: the biggest current you'll see there will not be determined by the alternator - it will be determined by the voltage difference between the starter and the aux battery. Said otherwise, if you fully charge the starter battery, significantly discharge the aux, and trick the isolator to combine them, yes, the breaker will trip. Possibly releasing smoke at the same time.

Please go read some of the numerous existing aux battery threads. I'm sure there are good one in the FAQ. You'll see that plenty of ideas have been discussed already, you'll see why some are good and other are bad. Hint: pay special attention to posts by crazyvwvanman and thatvwbusguy.

Regarding your issue about the Yandina, check the SurePower 1314A,discussed in this thread.

[pomfritz]

I added 2 6V golf cart batteries along with an Iota charger, Blue Sea isolator and fuse panel and a Trimetric battery monitor. System works great. I had to come up with my own schematic based on the ones the various parts come with. But really what helped a ton was getting in touch with Jay Brown, thatvwbusguy, he really is very knowledgable and provided me the parts I needed to put it all together. I also picked all the various wiring upgrades he makes, all super quality, great additions.

I may add solar later on, I want to see how my power holds up with out it first. But if I do I would seriously consider the Trimetric Solar charger, which ties in nicely with the battery monitor. Google handybob solar to find this guys blog and very helpful advice on what works and doesn't.
_________________
83.5 233K. GW 2.3, SS exhaust, My German Frau named her Stefi

[TommyBoyGomes]

Thanks for the review. I too do not want to fry anything . I've actually read tons of threads on aux battery setups and have scoured SolarBob's website already as well (which is why I already have a Bogart Engineering Trimetric 2025 as my battery monitor), but I'm still learning obviously.

The Aux Battery is the standard Aux Battery from GoWesty (http://www.gowesty.com/ec_view_details.php?id=4295&category_id=&category_parent_id=) which is a sealed lead acid battery. I didn't see any charging voltage instructions on the battery itself, but I saw on another aux battery thread that it is meant to be charged at 14.7V. My solar system charges this battery at 14.7V max, but when the car is on it's only getting 14.0V with the GW setup.

The starting battery is a standard Group 41 battery. It doesn't have any charge info on it either, but I believe it's also a sealed lead acid battery. Should I turn down the voltage regulator on the alternator back down to the voltages the stock alternator was providing it without the voltage regulator (14.6V @ 4,000 RPM)?

Thanks for the tip on the SurePower 1314A. That replaces the GW isolator altogether and auto-combines the batteries when the van is running, right?

Do I keep the GW circuit breaker in place if I use the SurePower? What you mentioned about tripping the circuit breaker when there's a substantial voltage difference between the batteries is a good point. What is the best way to do this safely?

Thank you.
_________________
1969 Squareback, 1776cc
1990 Vanagon Multivan

[Gnarlodious]

1. If your cranking battery is lead-acid then 14.9 charging voltage is going to boil it out pretty quick.
Not normally. Maybe if your aux batt is discharged and your cranking batt is fully charged you will hit 50 amps. One way to reduce the current is to use a smaller cable, mine is #10 as I feet 6 is too big. If you are cranking off your aux batt then for sure you are going to exceed 50 amps.

2. Yes.
Yes.
I would suggest some distance between your fuse panel/dashboard and all auxiliary wiring. I don’t know why GoWesty recommends your wiring but after installing a number of their upgrades I have learned to not follow their instructions too closely.

3. Yes, if any stretch of your intertie cable is smaller than the rest that is not only suboptimal but can be a meltdown hazard as the smaller conductor will be the first to overheat.

4. Yes, the AGMs should float down to 13.5 volts after an initial high voltage recovery charge. Too much long-term high voltage charging will damage AGMs. You should turn on your lights to bring the voltage down.

No. There is a charge profile for AGMs that prevents overcharging that you see in the dedicated AGM smart chargers. Mine charges 14.8 for about 30 minutes that reduces to 13.5.

5. I don’t know what this means or why GoWesty has gotten involved in these connectors. My auxiliary wiring is all under the seat and I dislike complicated tie-ins to other systems. That way one system can totally fail or be disconnected and it has no effect on the other.

6. I would just change all this back to original.

7. Good idea. I have the Yandina and it works well except I have the 3-way switch so I can force-connect, automatic or force-disconnect. Seems to serve me well for 2 years now.

8. I would say no. Mine is #10 and I have no fusing, but it doesn’t run through any flammable material. #6 is that much more hazardous. You should look at your cable routing and evaluate its disaster proneness. One thing you can do is put a short stretch of #8 in a non-hazardous place and that will serve as a fusible link in case of meltdown.

PS: You are pretty good at drawing diagrams!

[jmranger]

I don't know the GW setup well enough to comment. As you've certainly read already, many here believe it undercharges the aux battery, because it uses the undersized VW fridge wiring.

Personal opinion: 14.6/14.7V at the starting battery is fine [Edit: well, maybe not. See thatvwbusguy's post below]. No need to ditch the adjustable voltage regulator, but if that's what your previous regulator was outputting, you may have wasted some money there. I'd just fully charge the batteries with a multi-stage AC charger before adjusting the regulator, and adjust with all loads (fan, headlights, ..) turned off, to ensure that the voltage doesn't go higher at other times. Yes, that means that with heavily discharged batteries and/or heavy loads, the charging voltage will be a bit lower, especially if any connection between the alternator and the batteries (and matching ground paths) are corroded.

One thing that's not initially obvious when designing battery systems is that wire resistance is as much your ally as your enemy.
Just for the fun of it, let's imagine a perfect system, with no resistance at all. Let's say that we connect a fully charged starting battery at 13+ volts to a moderately discharged aux battery at 11v. The good old Ohm's law says that the 2+ volt differential across a 0 ohm resistor will translate into... an infinite amount of amps. Ouch.
In real life, resistance is never zero, because batteries have an internal resistance too, but as Gnarlodious says, the wire does have a safety role to play. But this isn't a substitute for fuses.

[thatvwbusguy]

The first thing that pops into my mind is that this seems like an awful lot of effort just to charge a little 40Ah battery.

My recommendation would be to completely remove anything on the charging side of the GoWesty setup and just leave the wiring that goes from the positive post of the auxiliary battery to the dash. As long as the accessories being powered via the auxiliary battery have been working properly, you can leave them as is. If you are starting to get sketchy connections from the 6-way connector, yank it out and set things back to stock with solder or quality crimp connectors.

Be sure to inspect the condition of the cable from the alternator to the starter as well as the main battery cable from the starter to the positive post of the starting battery (and all of the applicable terminals in between). You could do a voltage drop test on each cable if you want to know what type of shape the parts you can't see are in. Since you will ultimately be depending on these cables to charge your auxiliary battery, you want to confirm that they are in good shape.

Once you know that the stock cables are good to go, the most straightforward way I have found to connect the auxiliary battery to the starting battery is via the bolt on the positive battery clamp on the starting battery. Use a 1/4" ring terminal protected with high quality heat shrink tubing.

Your next choice is how you want to run the wire from the starting battery to the auxiliary battery. Some people run it across the aisle inside the van after removing a strip of the padding under the carpet. Others choose to drill a hole through each battery box and run the wire under the van. I have always gone with the "under the van" option (run the wire inside protective loom and install a rubber grommet in the hole in each battery box). If you use the aisle between the seat to travel from the front to the rear on a regular basis, the "under the van" approach is definitely recommended.

If you are planning to keep the small sealed battery that you have now, 10AWG or 8AWG wire between the batteries should be adequate. A larger battery would benefit more from the current carrying capacity of heavier gauge wire.

The choice of circuit protection is up to the installer. Since the main protection afforded by a fuse or breaker in this instance is to prevent the danger of a short to ground situation, physically protecting the wire well is often enough (it was good enough for VW on the main charging circuit after all). Fuses or circuit breakers can also be used as current limiting devices, but that is really the exception rather than the rule. If you do want to install circuit protection, place the fuse/breaker as close to the positive battery post on each battery as possible.

Based on your interest in not using a bi-directional ACR like the Yandina C100, I would still advise getting rid of the GW silver solenoid in favor of going with the SurePower 1314, which is a uni-directional voltage sensing relay that will connect the batteries to charge from the alternator, but will not send charging current from the solar (attached to the auxiliary battery) to the starting battery. This will completely eliminate the need to depend on the blue alternator field wire circuit to initiate charging.

Now for the "if I was doing this in my van" rundown: If the amount of Amp Hours from the GW battery has been serving you well so far, I would probably install a Group 41 starting battery under the driver's seat in its place and turn the voltage down to 14.3V at the alternator. There are more usable Amp hours in a Group 41 starting battery (about 65-70Ah) than any of the small AGM batteries that will fit under the seat. They also cost less than half the price, last about 4 years on average with responsible use and don't require any special charging considerations.

A SurePower 1314 connected with 8AWG wire would be my choice for charging from the alternator if I also wanted to ensure that all of the available current from my solar system was going to the auxiliary battery only.

Keeping things as simple as possible is almost always my first choice. I love the Group 27 or Group 31 deep cycle under the passenger side of the rear seat approach, but realize that it is not everyone's cup of tea. REgardless of the system design, simplicity reduces troubleshooting time, which leaves more time to enjoy the fruits of your labor.
_________________
Jay Brown
'85 Zetec Westfalia
Newmarket, NH


If you want others to be happy, practice compassion.
If you want to be happy, practice compassion.

[TommyBoyGomes]

Thanks thatvwbusguy,

I'll revise my diagram with to take into account some of your recommendations and re-post.

Quick question, what voltage should I have at the starter battery with all accessories off and the engine at 4k RPM? Or is there a benchmark/stock reading at another RPM that I should use? Thanks.
_________________
1969 Squareback, 1776cc
1990 Vanagon Multivan

[crazyvwvanman]

Take the voltage measurements at idle speed, after reving the motor for a second. The voltage should NOT go up just because you run the rpm up high. If it does then there is a problem to be tracked down.

The most critical measurement is voltage at the alternator, then compare that with what is at the battery. If it shows a big drop from one to the other then that indicates a problem to be tracked down.

Mark

[TommyBoyGomes]

Ok will do. What voltage should I expect to see at the alternator when idling?
_________________
1969 Squareback, 1776cc
1990 Vanagon Multivan

[crazyvwvanman]

The stock wbx alternator is rated at 14 volts. Idle, 2000, 4000, rpm doesn't matter. If it goes up when rpm goes up then something is wrong.

Typical at the stock alternator is 13.7 - 14.1 volts but it should still hold the same reading under the load of headlights, heater fan, etc. So whatever yours reads it should hold very near to it at all times.


VW says anything between 13.5 and 14.5 is ok but if it was as low as 13.6 I would do something about it like replace the regulator module. There are also adjustable regulators to let you set a desired voltage so perhaps 14.3 - 14.5 with one of those.

Mark

[TommyBoyGomes]

Ok thanks. Yep I have an adjustable voltage regulator, I'll turn it down to 14.5 so I still get max charging ability at my aux battery.
_________________
1969 Squareback, 1776cc
1990 Vanagon Multivan