2nd battery wiring q's

I'd like to add a 2nd battery to my boat in the nose for my stereo and ballast pumps, and think I have most of what I need to install it. The stock/starter battery is in the starboard rear locker, so there will be quite a distance between batteries. I don't know what size wires I'll need to run to connect the front battery to the battery switch, the starter battery to the battery switch and the switch to the starter. I've labelled those 1, 2 and 3 in the diagram. Since the run for #1 is probably about 20', I'd assume a fairly hefty set of wires would be needed?

Also, I'd really like to add a Battery Tender(or similar) to the HOUSE battery so it can get back up to speed while the boat sits overnight. I'm not much concerned with the starter battery since it will get the majority of the charging while I'm out. My question is would it be ok to leave my battery selector switch in position 1 while the battery tender is connected to the house battery, or will I have to switch it to OFF every time?

Finally, I'd love to know if there are any issues with my proposed setup! Thx in advance.

i don't know enough about all this stuff and i had to ask a bunch of questions and have a pro install it for me, but if you're going to goto all that trouble, you should be able to make that yandina c100 charge the house battery as well while you're out. that's the beauty of it, it will charge both once the starting battery gets up to full charge. the other thing to consider is, to get a charger/tender that will do smart 3-step charging for BOTH batteries. it will lengthen the life of both of them and you can use it while the boats in storage. it won't cost you that much more to get one that will do both. lots of people here use the battery tender stuff, i bought a chargetek 500 unit. it's just a little 5-amp unit, but it charges both independantly of each other. just a thought. mikeski or rod hopefully will see this and chime in. you're on the right track, i just can't validate that drawing.

Yeah, I've considered one of the battery tenders that can handle two batteries, but I have a similar dilemma in that I'll have a pretty long wiring run to get one of the batteries charged. Plus, I'd think I would still need to put the battery selector switch in the OFF position for the tender to work correctly. I'd like to get that confirmed.

I have to admit I pulled the above from what Mikeski was working on putting in his boat, but I don't think he's gotten a charging scheme worked out yet. Maybe he or Rod M. will jump in and set me straight.

Update.. I checked with the Battery Tender folks and they advised one of their 6amp chargers, which according to them has enough juice to keep the Combiner closed (>13.l3v) even in maintenance mode, so it should be able to keep both batteries at full via the combiner.

http://batterytender.com/product_info.php?products_id=7&osCsid=1736d0696670 beea5a019ffdcfd8259b

I'm close to pulling the trigger on it, but would love to have a 2nd opinion as it's a little bit of dough.

Also, anyone on the gauge wiring to the front? Would 4 gauge be OK for that long a run?

Joe I think you have it wired wrong. The alternator is supposed to be connected directly to either the house or starting bank (prefered method is to have it directly connected to the house bank since the bulk of the charge will go to the house after sitting for a long time). This is because the starting bank rarely takes more then a top off charge after starting the engine. This means the contacts inside only have to deal with a moderate transfer of current while equalizing and the contacts wont close until the house bank if fully topped off preventing multiple open-close cycles.

Joe:

Your wiring looks correct. The question I have is your intention for the battery switch.

With the battery combiner there will never be any need to switch the battery switch to anything other than "1", unless your main starting battery goes dead and you want to start off the stereo battery.

If you want the option of starting off the stereo battery then the wires to that battery are going to need to be rather large so that the drop in the wiring doesn't hurt you. I would suggest #2 or even #0 wire.

If you weren't concerned about trying to start off the stereo battery then I would recommend something lighter, perhaps #4 wire. It would carry enough current that it would give a nice assist to the starting battery in the "both" position, and might start a warm engine even if the starting battery was completely dead.

If you wanted to just discard the idea of starting off the stereo battery (note that in a pinch you could always disconnect the batteries and swap them physically) then I would do away with the battery switch and run #6 wire. In this case the wire only needs to be able to carry what the alternator can put out, minus what the rest of the boat is using. If you have a stock alternator then I doubt that you would ever be sending more than 50 amps up those wires.

There are several advantages of dispensing with the battery switch:
1) You will never accidentially leave it in the "both" position and end up running both batteries down.

2) it is cheaper

3) you will never accidentially turn the switch to "OFF" while the engine is running and destroy the alternator.

The battery combiner will connect the two batteries when it is appropriate and disconnect automatically. The only downside is being able to quickly switch to the other battery for emergency starting, which of course assumes that you didn't run that battery down also.

As for the battery tender:

The big question is if the battery combiner will close at a battery voltage of 13.1 volts. That is right about the point where the combiner should sense and close, so it could go either way.

hey rod

question about my setup since you're posting, by the way you need a paypal button in your signature so we can just pay you for your replies.

i have dual blue tops, a blue sea switch, a yandina c100, and a chargetek 500. when i plug my my charger in, the yandina "conbined" light comes on and stays on at each of the 3 steps of charging including float. EVEN WHEN THE BATTERY SWITCH IS IN THE OFF POSITION. this isn't a problem is it? I had a "pro" wire it all up for me because I just don't understand this stuff enough, but I'm concerned that may be a problem??

The idea of the battery switch was to have flexibility in the instance of a dead starting battery. My thought was to install it back in the rear storage locker to lessen any accidental switch changes that could hurt the alternator. I've already purchased it, so it's pretty much a sunk cost.

I have a couple runs of 0/1 gauge wire I no longer will have use for, except they're only about 18' long. Not enough to make it clear up front.

I'll have to put some thought into if I'll really need full juice from the house battery for starting. At this point I'll probably go with lighter gauge (4?) and treat it as a last resort option. Of course, I can always just physically swap the batteries as you suggested, too. Oh, and I upgraded to a 100amp alternator last season. I assume 4 would still work?

The C100 is supposed to close at 13.3 volts, so assuming it is working as advertised my guess is the Battery Tender should do its duty?

Thanks for the reply! Now where's that Rod M paypal button?



(Message edited by superairdawg on March 30, 2006)

Start and charge are two seperate wires, not one so no I dont think its wired right as far as the alternator wire into the switch/combiner. http://www.hellroaring.com/4way.htm

Joe--
This is how I hooked mine up as well except I do not have the long runs.

Has anyone ever thought of/tried using the camper charge output of your truck to charge up your 2nd battery on the way home? This should eliminate the need for a on board charger and yoy could just install a 12v lighter socket in the bow and make a jumpper to your truck plug. I have been thinking of trying this but have not it should work?...

Good to hear. Sounds like it's going to boil down to whether I pony up for a large enough gauge wire to connect the front battery.

Bob--
He has it hooked up exactly like the Yandina instructions show it to be. The hellroaring wire up a bit different.

Bruce:

The combiner should click on during the first stages of charge, the only question is if it would stay on during "float". The combiner would have a voltage (around 13.2 volts) where they would initially click in, and then a lower voltage that it would have to drop to before it let go.

It sounds like it is working fine, don't worry about it.

okay, i see so you're saying it's combined because the starting battery hasn't dropped below the threshold then

that makes total sense...thanks again Rod

Here is a quote from install guide for the yandina http://www.yandina.com/acrobats/C150Data.pdf "If it is convenient it is safer to connect the alternator
output to the house battery so it receives its charge directly
with no switches that can turn it off accidentally." (bottom of page two on the left) This is the same combiner as the west marine one from what I can tell. Is anyone using one of these doing as prescribed in using a minimum of 6' of 6 gauge wire between the positives of the BC, or are you just using regular 4/2/0??

Reminder to all that has a AGM or gell cell batteries. Hook the blue wire on the combiner up to the starting battery + to prevent overcharging. I think most alternators are set up to charge conventional batteries. Have heard the blue tops will not last with the overcharge over time.