Batteries Discharging while under sail

[GlobalGaz]

Just wondering if anyone has struck this before I investigate further.
I have recently purchased a 1990 Beneteau 390 in the Philippines which has most of the original wiring. It had 2 x 100w and 2 x 120w solar panels fitted to which i have added 2 more 100w panels and now paired the panels into 3 banks at 24v into a brand new MPPT 40amp controller feeding the 2 near new 200amp/hour AGM batteries. The original 2003T Volvo has been fitted with an upgraded 100amp Alternator. The solar panels charge the batteries to 100% at 13.8volts fine and the engine starts fine overnight or after a few days at 13.4volts. With engine running the voltage peaks at 14.2. The problem I have is when under sail at any more than about 5 degrees to either side the batteries discharge sometimes down to as low as 12.2volts which will not start the engine. If we sit stationary for 1/2 an hour the voltage comes up enough to start the engine. I have disconnected anything that is not required, old inverter, reefer etc but am at a lost to explain why this is happening? Any ideas on where to start looking? Cheers Gary

[NYSail]

What orientation are your batteries? Maine Sail has a article on this.... have to be port / starboard oriented to keep lead covered when heeling. . not sure if that is your problem but worth a read.

[smac999]

With Agms it should not matter.

The better question is why the engine battery is dropping. Nothing should be on it.

[Pizzazz]

Most likely a battery problem, so Inwould replace them.

My first thought was, if you only have 200 AHr deep cycle batteries, they may not provide enough current to start the engine reliably. But I can start my Yanmar (100A start current) on a single 35 AHr AGM even at low charge. So, that is unlikely to be the problem. More likely, your batteries are bad.

In any case, I would recommend a starting battery and more main battery capacity to begin with. These days the standard is 4x golf carts + 1 starting sized for your engine. But the 4x golfs will start anything up to 3-4 kw starting motor.

[Tin Tin]

How old is the start battery. What brand, type and AH or CCA. Have you cleaned the terminals.

[hpeer]

This is an interesting problem. No direct answer but may be able to help with trouble shooting.

From the comfort of my saloon I would recommend acquiring an ammeter. A recording one would be ideal but not necessary. Record the current when still, when sailing flat and then when heeling. Look to see if there is some unexplained change in the current.

The 2 things h th at come to mind are:
1-the chart plotter and other instruments are drawing far more than you think
Or
2-when you heel over some wire or connection is being made to drain the battery.

Here is a completely wild ass guess, meant more as an example than reality; when you heel the bilge pump float switch causes the pump to work continuously and it eventually drain the battery. When you are flat it doesn’t run. An ammeter should show the change in current. Something like a bilge pump may not be wired through your panel and may not show up on the panel ammeter.

[MJH]

Originally Posted by GlobalGaz

Just wondering if anyone has struck this before I investigate further.
I have recently purchased a 1990 Beneteau 390 in the Philippines which has most of the original wiring. It had 2 x 100w and 2 x 120w solar panels fitted to which i have added 2 more 100w panels and now paired the panels into 3 banks at 24v into a brand new MPPT 40amp controller feeding the 2 near new 200amp/hour AGM batteries. The original 2003T Volvo has been fitted with an upgraded 100amp Alternator. The solar panels charge the batteries to 100% at 13.8volts fine and the engine starts fine overnight or after a few days at 13.4volts. With engine running the voltage peaks at 14.2. The problem I have is when under sail at any more than about 5 degrees to either side the batteries discharge sometimes down to as low as 12.2volts which will not start the engine. If we sit stationary for 1/2 an hour the voltage comes up enough to start the engine. I have disconnected anything that is not required, old inverter, reefer etc but am at a lost to explain why this is happening? Any ideas on where to start looking? Cheers Gary

My understanding is that AGM battery acceptance charge is 14.7V; 13.8V would be the setting for Gel batteries.
Boat heel should have no affect on AGM batteries.

My boat has a Volvo Penta D2-55B engine and the specifications for battery starting is 88AH, 700cca. I have had to supplement a Group27 battery with a U-1 to meet those requirements. Check your battery specs.

The start bank should only see a draw on starting and then recharge while sailing via solar. Something is wrong in your charging setup or perhaps the start battery is bad.

Lastly, as new-to-us boat owners we naively assume that the previous owners installed everything correctly, that has not been the case with me in many instances.

Good Luck.

~ ~ _/) ~ ~ MJH

[Brewgyver]

It's apparent from the OP's description that he has no start battery.

Of course, this is a perfect example of why any boat with an engine should have a separate engine start battery.

[GlobalGaz]

Thanks for the reply's. The orientation of the batteries is fore/Aft. The batteries look new and hold charge fine when not under sail, but i am unsure as to their actual age. There is a separate start and house battery both identical. However the engine starts better with both batteries so that is the way i had been running them, also the the solar for some reason is wired to only charge the start battery, i will rectify this next trip over there. I am starting to think the float switch / bilge pump may be the culprit I will check this next trip and report back. Thanks Gary

[Tin Tin]

A battery combiner would ensure both batteries get charged (assuming they are both serviceable), yet leaves the start battery isolated, also has an emergency cut-over switch to allow house battery to start engine.


https://www.victronenergy.com/batter...tery-combiners

[chris95040]

Originally Posted by hpeer

Here is a completely wild ass guess, meant more as an example than reality; when you heel the bilge pump float switch causes the pump to work continuously and it eventually drain the battery. When you are flat it doesn’t run. An ammeter should show the change in current. Something like a bilge pump may not be wired through your panel and may not show up on the panel ammeter.

Clever!!!

A few years ago we were sailing for a while at a steep angle of heel - "hey! the bilge pump is running, where are we taking on water?!?!" - Opened up the bilge in a hurry, looking for water, finally my eyes landed on the float switch and I went - orienting the switch fore + aft fixed it.

[Cheechako]

A) your engine should start fine at 12.2 volts
B) you might have a shorted battery cell in one battery.
C) Chris95040 might be right!

[billgewater]

Maybe you can do some eliminating while at a mooring. Use some water barrels etc .hanging from the boom which is then swung outboard. i.e. make the boat heel without sailing. It is amazing just how much heel you can induce this way in a controlled manner. Moving the boom out or back in is easily controlled with a few ropes and the main sheet. This will be very quiet and if it is a bilge pump you will be able to hear it. Also you can spend time trying to track down the problem by turning depth sounders and other nav. instruments off/on.

If nothing happens (i.e. the problem does not occur) then it may be due to the boat pitching when under sail rather than any heeling issue.

I would put my money on some loose wiring that shorts out when the boat heels, pitches or just wobbles but when you do track it down please let us all know.

[GlobalGaz]

Originally Posted by chris95040

Clever!!!

A few years ago we were sailing for a while at a steep angle of heel - "hey! the bilge pump is running, where are we taking on water?!?!" - Opened up the bilge in a hurry, looking for water, finally my eyes landed on the float switch and I went - orienting the switch fore + aft fixed it.

I notice the float switch is port / starboard so I'm starting to think this might be the issue? Also the bilge pump is currently not working (I have purchased a replacement) so have no idea what sort of current it is drawing in it's current state. cheers Gary