solenoid battery crossover

wowzer52 · Post by **wowzer52** » Sat Feb 26, 2011 4:19 pm

In a private e-mail I was asked about my battery system and thought I would share my response with everybody here in case someone can use some of this info...... I used two "continuous duty" solenoids, one per engine and used them as automatic "ignition activated battery switches". Wired much like dual Perko battery switches with one connected to each seperate engine ignition for activation. When the ignition is turned on to activate the coil it also activates the solenoid and attaches the house batteries to both engine batteries for starting and charging. When the ignition is turned off the solenoids are disabled, disconnecting the house batteries from the engine batteries creating 3 seperate systems, port engine, stbd engine and house. I also installed dual Perko switches for back-up. As compared to using a battery isolator which will charge all batteries while under way, using these solenoids will allow "full" battery power connection between the starters and batteries at the solenoid instantly not only for starting but also for charging while under way. As for my battery size, I tried an 8D in one of my boats and found that it was too heavy for one person to install or remove and didn't last any longer than two smaller ones. In fact, the smaller ones with the same amount of amps was easy to move, gave me lots of room in the bilge for engine maintainance and I could switch batteries if I had a problem. With an 8D in a smaller boat if one cell goes bad the party is over. I currently use 4 high quality group 27 12v batteries. A matched pair of "deep cycle" in parallel for the house and one "starting" for each engine. I installed LED lighting, a well insulated 12v/110v fridge, a 400 watt inverter used only for laptops and cell phone charging. Laptops are used for navigation, watching movies and entertainment and internet access is via a Droid cell phone USB connection or Wi-Fi at the dock. When laptops are fully charged before coming to the boat it is easier to maintain that charge than it is to fully charge them from the inverter. No TV, as our laptops and books (boating magazines and Chapmans) fulfill the need for entertainment. weather info. comes through the VHF radios and laptops. We have marine application propane cooking and a Dickenson propane fireplace/furness for heat while on the anchor. For dock charging I installed a 3 bank digital charger/maintainer, one bank for the house and one for each starting battery. I am not sure how long we can stay out but have stayed out four days and three nights with only the slightest drop in battery voltage measured from the Garmin GPS/chartplotter voltage setting. However, there was a time before replacing the old house batteries that came with the boat, no record of how old these were, when waking in the morning our batteries were about dead. When I turned on one of the LED lights they were dim and the fridge was not working. I started one of the engines and went on my way but replaced the house batteries before the next outing. The solenoid system worked perfectly. I did a ruff calculation of the approx. amp draw in a 24hr period and found that I have plenty of battery for "my" system, as the whole purpose is to save battery power. I will try to post more details about this on the forum if anyone is interested. Hope someone can use some of this info.

Big D · Post by **Big D** » Sat Feb 26, 2011 4:46 pm

Thanks Wowzer. I wanted to do the same thing with solenoids but I want to use the latching type. That way the coil isn't always activated. Would activate on crank and stay latched on until power was applied again. The problem is trying to apply temporary voltage to unlatch when turning engine off. I'll come up with something though.

rbcool · Post by **rbcool** » Sat Feb 26, 2011 5:49 pm

Hey Wowzer... off topic. I just ordered a new motorola Droid X. How do you like the droid??

Ron

wowzer52 · Post by **wowzer52** » Sat Feb 26, 2011 10:04 pm

I like the Droid but it is alot smarter than I am and my wife loves it. I use her Droid for scanning merchandise and checking prices or going online but I loose a lot of cell phones in the ocean and have broke a few so I've got this military spec phone that's pretty tough and water proof. The screen is really too small but it does get internet. I'm thinking of a new Droid for myself pretty soon but dang they're spendy and I hope they are a little tougher than they used to be.

risctaker · Post by **risctaker** » Tue Mar 01, 2011 2:51 pm

Nice Electrical Setup. Re: Your 3-bank charger, bear in mind that all chargers only have one central sensor than determines the type and amount of charge to apply to all banks. Even though you have a "3-bank" charger, there are not 3 separate charge-rate sensors in them. What this means is that your Starting and house batteries all all getting the same type and charge duration. Multi-bank chargers are designed so that all the banks have the same battery "types" connected to them. The risk you run by mixing the starting and deep cycle types on the same charger (multi-bank or not) is that one or the other will begin "gassing" (overcharging) while another bank is still looking for additional charge. The final solution for this is to have a separate charger for each battery "type". That way their float voltage is maintained without damaging an incompatible battery type.

I have a 40 amp single high output charger for my deep cycle house bank and a smaller 20 amp 2-bank charger connected to my two separate (but same type) starting batteries.

wowzer52 · Post by **wowzer52** » Tue Mar 01, 2011 9:32 pm

My 3 bank digital charger has 3 seperate/individual charging systems. That is why I took out the old 3 bank charger and installed the new one. I researched first then read the fine print before spending so much money on a charger. I believe the old 3 bank charger was as you say and that is why I replaced it. If all 3 bank chargers were as you say, I would have kept the old one or bought a single heavy duty charger and paralleled all my charger hookups and got the same thing. I guess you get what you pay for.

Big D · Post by **Big D** » Tue Mar 01, 2011 9:47 pm

My remote charge display indicates different levels of output charge per bank if banks are at different levels of discharge; usually the case between start and house. This indicates to me that it is monitoring and supplying each bank accordingly.

wowzer52 · Post by **wowzer52** » Tue Mar 01, 2011 10:11 pm

One way to find out if yours charges at different rates is to use a amp meter to test each bank seperately after being out for a weekend. I use my multimeter alot because I don't like dead or dying batteries. A little research goes a long way.

Big D · Post by **Big D** » Tue Mar 01, 2011 10:17 pm

Wowzer, does your charger have a remote display? Mine very clearly displays amperage to each bank.

wowzer52 · Post by **wowzer52** » Tue Mar 01, 2011 10:47 pm

No remote display but it shows the ratings on led ladders on the face of the charger. I love this thing. No more cooked batteries and no guessing if one bank is charged or not.

risctaker · Post by **risctaker** » Wed Mar 02, 2011 10:09 am

Just for clarity, I wasn't questioning the ability of your multi-bank charger to put out different amperage to each bank based on the level of charge needed for that bank. What I was saying is that the same charger cannot distinguish between flooded (lead-acid), AGM or Gel batteries all of which need a different "type" of charge methodology.

ready123 · Post by **ready123** » Wed Mar 02, 2011 10:40 am

risctaker wrote:Just for clarity, I wasn't questioning the ability of your multi-bank charger to put out different amperage to each bank based on the level of charge needed for that bank. What I was saying is that the same charger cannot distinguish between flooded (lead-acid), AGM or Gel batteries all of which need a different "type" of charge methodology.

Can't fault the charger there... would one plan to mix battery types on a single charger?
Can one plan the mix to minimize any downside?

How I setup my mixed battery types which does not seem to be a problem after five years....
AGM house, charger set to AGM type.
Wet cell engine batteries... engine alternators only charge these underway.
The genny and shore power charge all three... on the hook the AGM is the only one that runs down.
My Xantrex charger does not seem to have caused any problems for the wet cells while bringing the AGM back to full charge. (I do have it set to not equalise).
All batteries still hold their charge over winter storage at sub freezing temperatures after 5 yrs of this treatment.

My choice to mix does not seem to have a visible downside.

risctaker · Post by **risctaker** » Wed Mar 02, 2011 10:50 am

Taking everything into consideration your setup seems to be working for you and that's all that counts right?

Big D · Post by **Big D** » Wed Mar 02, 2011 8:38 pm

Does anybody know the numbers? I seem to recall that AGM and wet cell have very similar charge rate specs.

wowzer52 · Post by **wowzer52** » Wed Mar 02, 2011 10:18 pm

My charger can be set for AGM or wet cell but I chose not to mix per charger manual recommendation, however, a local automotive and marine electrical company said the AGM batteries can be mixed but may not recharge completely with a wet cell charger. I guess I just haven't found a good reason to change to AGM, and the cost for a complete set of AGM would definatly be something to consider.