Improving Trim By Moving The Batteries

ggray

The recent post about trim tabs has me thinking again about moving the batteries forward to get the bow down...with less trim tab.

22 Cruiser with Honda 90, two batteries, one in each stern locker; trim tabs and Permatrim.

I haven't measured closely to make sure there is room under the vee berth, but if I could fit the two batteries there, I would be moving 85 pounds from the stern to the bow. There would be a lot of work to accomplish this, but I would think it would be quite effective in getting the bow down.

I would need to run heavier cables to the motor, and it would probably be best to use sealed batteries.

Is this a good idea? Would there be a problem at times with fuel tanks nearly empty? Has anyone done it?

thataway · Posted: Fri Oct 15, 2021 8:43 pm Post subject:

Reasons it is not a good idea:
You are permanently transferring weight forward, and may risk bow steering and broaching if running down wind/seas.

Your cables for the battery should be 1/00 to 2/00 for that distance. Check out the weight and the cost.

Flooded lead acid batteries inside a cabin is not advisable. When charging the batteries give off Hydrogen gas, which is explosive.

Flooded lead acid batteries have acid, and if it spills it is very corrosive.

westward · Posted: Fri Oct 15, 2021 10:52 pm Post subject:

I have done this before with good results, albeit not on a CD 22. AGM batteries can be installed in enclosed spaces, in any position desired. (The nervous part of me had me vent my enclosure anyway). You need to carefully size the wire for the runs, and place additional breakers on the battery end of the runs.

This is NOT to say doing so would be a good idea on your boat, just that it can and is done routinely and safely. Your particular trim situation will dictate. I will say, however, that the CD22 was designed around the lighter Johnson 70 2-stroke, and that modern 4 stroke mains and kickers, together with dual batteries and larger fuel tanks, tend to make these boats quite stern-heavy.

Best of luck, Mike

clayhubler · Posted: Fri Oct 15, 2021 11:38 pm Post subject:

The only reason I haven't done this yet is that I haven't had the time to work on the boat lately. My boat is very stern heavy. I'm going to use an agm in the vberth compartment just forward of the porta potty. I put larger trim tabs (12x12) on my boat and they are usually almost fully extended when running.

ssobol · Posted: Fri Oct 15, 2021 11:52 pm Post subject:

IMO, another thing to keep in mind is that the mountings for batteries in the bow probably need to be a bit sturdier than those for batteries in the stern. The bow is the moving part when the boat is in rough water, especially in a light hull like the C-Dory. These movements will impart accelerations to the batteries. Especially in those situations where the bow slams down. The relatively high inertias of heavy moving batteries can add higher loads to the mounts than what is experienced when the batteries are at the back of the boat.

Since forward mountings are not provided by the factory, make sure they are tough enough for your situation. Wouldn't want the batteries breaking loose and bouncing around.

ssobol · Posted: Fri Oct 15, 2021 11:53 pm Post subject:

IMO, another thing to keep in mind is that the mountings for batteries in the bow probably need to be a bit sturdier than those for batteries in the stern. The bow is the moving part when the boat is in rough water, especially in a light hull like the C-Dory. These movements will impart accelerations to the batteries. Especially in those situations where the bow slams down. The relatively high inertias of heavy moving batteries can add higher loads to the mounts than what is experienced when the batteries are at the back of the boat.

Since forward mountings are not provided by the factory, make sure they are tough enough for your situation. Wouldn't want the batteries breaking loose and bouncing around.

Peter & Judy · Posted: Sat Oct 16, 2021 11:13 am Post subject:

On my 22' I have a Honda 90, a Honda 9.9, two group 24 batteries, one on each side, add to that a two full tanks of gas and a 45 litre aux tank and then maybe more fuel and a cooler. I found that the boat was often rear heavy. My solution which killed two birds with one stone was to cut out the v-berth area and add hatches, which I filled with a lot of other stuff that cluttered up the cabin. The result with a heavier bow, is that the boat is more balanced with more weight up front. I have noticed a definite improvement in handling, especially when I get up on plane. Personally I would not move the batteries forward because of the many issues that others have mentioned in previous posts. I think that most boats that go out on extended cruises have lots of other stuff that could be moved forward instead.

T.R. Bauer · Posted: Sat Oct 16, 2021 11:13 am Post subject:

I would say there probably isn't a more stern heavy boat out there at times than mine with shrimps pots, hundreds of feet of sinking line, 3 batteries, twin engines and often a kicked too, 30 gallons of extra fuel, 6 gallons of water, and a big cooler with ice all thrown in the back. There might even be a 30 pack of Coors back there.....lol....It trims out and it have never seemed to be much of an issue in my opinion. I've put around 2500 hours on the boat and I'd probably notice if it were a serious issue. The only real problem is wishing I had about 150 hp when it's loaded like this, because the boat only goes around 18-20 mph and when you're shrimping spot is 60-70 miles away, it's a very long ride.

san juanderer · Posted: Sat Oct 16, 2021 2:56 pm Post subject:

OP said he would install " sealed" batteries. No need to discuss wet cells. OP said it would move about 85 #'s forward. How much weight does a anchor with chain add forward ? At least 85 #. Not enough to mention down seas running performance. How weight does an adult male sitting in the passenger front seat add to the forward ? More than 85#'s. Just use a large enough wire.

ggray · Posted: Sat Oct 16, 2021 11:09 pm Post subject:

This is great! Wonderful comments that give me a lot to think about. Thanks!

Of course, the big variable is the weight of the fuel...or where it is. Ideally tankage would be centrally located so the state of being filled would not change the trim. But that's not what we have.

It may not be very practical, but the battery(ies) might represent a moveable weight that could be shifted according to fuel/passenger load, and conditions. Hmm....

Or move gear forward as has been suggested. But as we use the boat now, there is not much gear to be shifted. Perhaps we should not fully fill the fuel tanks as mentioned in the other post.

I'll consider moving just one battery to see what happens. I can look into how small an Odyssey battery would be that is capable of starting my motor. That could save a little weight back there. Not much, but it would be sealed, and may be easier to fit in the bow area if I decide to do that.

I do appreciate ALL comments that have been made.

forrest · Posted: Sat Oct 16, 2021 11:47 pm Post subject:

Batteries weigh around 40 pounds each. Why don't you get 160 pound friend to sit where on the spot you want to move the batteries to and see if the difference in ride is worth the trouble. I doubt you will tell a difference. You could also remove 13 gallons of fuel (approx. 80 pounds), have an 80 pound child sit where the batteries would be and see if you notice a difference that way. Just some different ideas. I don't know if they would work. Good luck.

hardee · Posted: Sun Oct 17, 2021 1:28 am Post subject:

Or a bag or 2 of Dog food, a bucket of cat litter, or a gab of week killer or compost.

If you are just doing short day runs, you really don't need 80 gallons of fuel every time you leave the dock.

Harvey
SleepyC Moon

ggray · Posted: Sun Oct 17, 2021 8:09 am Post subject:

Yes, I can try those things.

I don't have full tanks all the time, but when I fuel up, I top off. Perhaps I will back off that some.

ssobol · Posted: Sun Oct 17, 2021 10:58 am Post subject:

Karl Konecny · Posted: Sun Oct 17, 2021 12:11 pm Post subject:

My boat had a similar setup when I purchased it although the two batteries where in the bilge between the gas tanks (bad idea). I moved the starter battery to the starboard lazarette and the house battery to the space below the v-berth. I built a battery mount supported by vibration isolaters (see photo in my album). The batteries have separate isolation switches. The setup works well.