Rewiring the batterys for an inverter General Forum Forums

Re-doing the power systems on Valkyr

When we got the boat it had two optima batteries one in the starter bank and one in the house bank. There were two other group 31 Sea Volt AGM batteries sitting on the boat not hooked up. My plan is to use the two group 31 Sea Volt AGM's along with 2 identical Group 31's that I have on my old boat to make a house bank of 440 AH. The two optima AGM batteries will go in the second engine starting bank. These are controlled from the stock DC switch panel that has a 1/2/All/Off switch integrated into it.

To charge the batteries Valkyr had a 3 stage computer controlled portable automotive 1/10/25 amp charger just clipped to one of the batteries. Though it is a very nice charger we would rather that the bank be charged independent of each other. We purchased a Xantrex XC 50 amp 12v 3 bank multi chemistry battery charger to rectify this. http://www.xantrex.com/web/id/.....roduct.asp

We got a pretty good deal by price matching at west marine $499 plus another 49 for a two year warranty that will replace it even if we drop it in the water. I normally don't do extended warranties as they mostly are a rip off but Xantrex doesn't have the greatest reputation with their support so we thought that a little extra caution would be good. Also it extends the warranty by a year which I liked also. We could have gone with a cheaper charger by several hundred dollars but this one can charge different chemistry banks separately as well as use input power from 240 volts down to about 90 volts.. basically no matter what the shore power is this charger can handle it. No having to go buy a new charger when in Europe etc.. Right now we only have two battery banks but if we ever get a powered winch there will be a battery up in the forward part of the boat that the third bank can handle.

Part of the battery equation is complicated by the inverter we are installing. A Xantrex Xpower 3000 watt inverter. http://www.xantrex.com/web/id/.....roduct.asp

It has a remote on off switch as well as a direct wire connection on the 120 side. The complication is that if we actually put much of a load on it the amp draw goes through the roof. As much as 350 amps at full capacity. I doubt we ever push it much over 200 amps but the system needs to be designed to handle that heavy of a draw or we could end up with smoking hot battery cables. Right now there are what look like 2 awg cables running from the battery switch to the batteries. Some of the cables connecting the existing batteries to each other look as if they are 4 awg.

2 awg sized cables have a max current capacity of 210 amps and 4 awg of 160 amps (those numbers are under ideal conditions, in a hot engine compartment knock off 25% at least). Both of these cable sizes are much to small to handle the potential current draw of the new inverter if all the current is trying to run through one set of cables.

Potential solutions are to move up to bigger cable such as 4/0 that is rated to 445 amps or to use a buss bar system where each individual battery is connected by its own positive and negative cable to the buss. You can use much smaller cable in this situation. 4 batteries connected to a buss by 4 awg cable can theoretically safely pull 640 amps as each set of cables can handle a part of the load in parallel. So 4x 160 amps per cable = 640 amps. If you add more batteries your capacity goes up from there. Another complication is that in an engine compartment that is hot you can't even draw the rated capacity through the cables. You need to de-rate them by as much ¼ their capacity. The longer, hotter and smaller the cables the more voltage drop you will get also. With bigger cables the voltage drop is much less. I purchased some of the cable from this vendor on the internet that I have delt with before and had good success with. http://shop.genuinedealz.com/M.....de%20Wire/ they sell cable and connectors at about 20% of what the same item at west marine would cost. I did purchase about 2/3 of my cable this time at west marine by price matching to get the cheaper price. I would rather over all buy localy than over the internet when I can just to support local vendors. I ended up paying a little more because of taxes than if I had bought it online. I wasn't able to price match the lug ends for the cable as west marine sells them in two lug boxes. I ordered the lugs from http://www.delcity.net/store/Heavy

This size buss should be able to handle in excess of 1000 amps so it is way over kill but the price was right. The next nearest thing I could find was well over 100 dollars each. I will have to build a shield that goes over the buses once they are installed to protect them and other stuff from accidentally shorting across them. Another nice thing is that I can use a tap and die to thread the holes and use 5/16 stainless bolts that exactly match the lug sizes to attach the lugs to the buss. All ends and attachments points will also be covered in vaseline or a special electrical grease to inhibit corrosion.

From the buss I will then use a very short length of 4/0 cable to go to the inverter that will be on the other side of a bulkhead from the buss. The 4/0 cable will be protected by a heavy duty 250 amp fuse in a mega fuse holder as close to the buss as I can place it.

The inverter setup had some gotchas in it also. Valkyr has an existing shore power setup and about 9 110 outlets throughout the boat. There is no existing inverter or generator so there was no systems setup to switch from on type of 110 to another. You can't run your inverter and shore power at the same time. It will cause unspecified bad things to happen to your expensive inverter. The solution to this is to install a Automatic Transfer Switch. There are readily available commercial solutions for this but most of them start at about $200 and go up. After some digging I found a Iota product called the Iota Engineering ITS-30R 30 Amp AC Transfer Switch.

I found these to be a cheap solution at about $57 each. I only need one as I will for now just have shore power and inverter. You lead the power into the ITS-30R from both and if the shore power is on it disconnects the inverter. If the shore power is off and the inverter is on it will connect the inverter. If I ever decide to add a generator then I will add a second ITS-30R and series and it will chose the power source in this order. 1. shore power 2. generator 3. inverter.

Once the installation is finished I will update this with photos of the installation.

Scott

Re-doing the power systems on Valkyr
When we got the boat it had two optima batteries one in the starter bank and one in the house bank. There were two other group 31 Sea Volt AGM batteries sitting on the boat not hooked up. My plan is to use the two group 31 Sea Volt AGM's along with 2 identical Group 31's that I have on my old boat to make a house bank of 440 AH. The two optima AGM batteries will go in the second engine starting bank. These are controlled from the stock DC switch panel that has a 1/2/All/Off switch integrated into it.
To charge the batteries Valkyr had a 3 stage computer controlled portable automotive 1/10/25 amp charger just clipped to one of the batteries. Though it is a very nice charger we would rather that the bank be charged independent of each other. We purchased a Xantrex XC 50 amp 12v 3 bank multi chemistry battery charger to rectify this. http://xantrex.com/power-produ.....eries.aspx

http://www.scottcarle.com/word.....series.jpg

http://www.scottcarle.com/word.....er3000.jpg they sell cable and connectors at about 20% of what the same item at west marine would cost. I did purchase about 2/3 of my cable this time at west marine by price matching to get the cheaper price. I would rather over all buy localy than over the internet when I can just to support local vendors. I ended up paying a little more because of taxes than if I had bought it online. I wasn't able to price match the lug ends for the cable as west marine sells them in two lug boxes. I ordered the lugs fromhttp://www.delcity.net/store/Heavy!duty-Copper-Lugs/p_1012.a_1

http://www.scottcarle.com/word.....ussbar.gif How long the link will be good I don't know. However just searching for DC circuit breakers will usually pull some up.

Here are the buss bars installed and hooked up. I still have to create a cover for them so that no accidents happen. They are up high and recessed behind the portside opening into the engine compartment so it is unlikely that anyone would accidentally set a tool across them but I want a cover for them anyways. The entire bus bar is coated with a di-electric grease as well as all lugs and bolts. All connections to breakers and batteries are also all greased. I am hoping this will help retard any corrosion. All cables were made by me and glue lined heat shrink wrap was applied to every joint between cable and lug. If I was unable to get heat shrink on it then I used self sealing/amalgamating silicone tape to seal the lugs/cable.

I installed the xantrex 5012 in the compartment under the pilot berth on starboard. It is on the other side of the bulkhead you can see behind the buss bars above and about 30 inches below it. This makes for a very short cable run from it to the buss bars to charge the batteries. I used some of the left over 4AWG cable to connect it. A bit overkill but the whole system is very much over spec to keep voltage drop to a minimum. Here is a pic of the xantrex installed.

You can see the AC power line on the left and the positive and negative DC lines coming out on the right bottom. The other two lines are the remote panel data line and the grey temperature sensor that is installed on one of the batteries negative terminals. The temperature sensor allows the charger to reduce charging levels if the batteries are hot or get hot during charging to protect them from damage. The remote control panel is mounted with the other instruments at the chart table. See images below for the remote control panel.

let it not be said that I did this all on my own. I was closely supervised during this whole process by

Sailor

Sailor up in the galley cubard behind the stove. He has learned how to open this himself when he wants to get back in there."

]

Scott
September 26th 2010 onboard s/v Valkyr Southport NC.