Jump start

25931

25931

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Even after seventy years of messing about in boats I am still learning and need to learn more. On Monday I found that both batteries were flat , first lesson -make sure that they are turned off before leaving boat. I conected the trickle charger and when I went yesterday there was nothing like enough power, second lesson - take starter battery home to charge properly. I took the car's battery to jump start and found that the very snug, made to measure battery compartment made it impossible to attach the jump leads so, with some fiddling I disconnected the leads from the battery in order to clip the jump leads directly to them. My next move will be to mount some form of extension to the battery terminals so that I can clip on jump leads and I would appreciate suggestions . I am reasonably sure that this is the best way to make sure that the situation doesn't recur.
 
I've found that with modern diesels you can get them to turn over even with a tiny residue of battery power by decompressing the engine. I've had to do this a number of times when my batteries have been allowed to go flat at anchor in remote locations.
 
Best way of avoiding (but not totally eliminating) a flat engine start battery is to isolate it from the house battery and domestic circuits completely. Use a VSR to split the charge and switches to couple the two banks together in an emergency. BEP Marine do a very neat cluster of switches and VSR that will achieve this. Not the only way to do it but perfect for simple people.
 
Tranona said:
Best way of avoiding (but not totally eliminating) a flat engine start battery is to isolate it from the house battery and domestic circuits completely. Use a VSR to split the charge and switches to couple the two banks together in an emergency. BEP Marine do a very neat cluster of switches and VSR that will achieve this. Not the only way to do it but perfect for simple people.
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Quite so i have a Victron Cyrix i have fitted, it senses both batteries & when the battery charger is charging the domestic bank it also pulls-in the engine battery too
 
prv said:
I've found that modern diesels don't have decompressors any more :)

Pete
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Yes, I'm surprised by this. I've just checked the spec on the latest Yanmars which don't have de-compressors but do have glow plugs. A retrograde step IMO.
I haven't checked other manufacturers' specs so don't know whether this trend is universal.
 
ghostlymoron said:
Yes, I'm surprised by this. I've just checked the spec on the latest Yanmars which don't have de-compressors but do have glow plugs. A retrograde step IMO.
I haven't checked other manufacturers' specs so don't know whether this trend is universal.
Click to expand...

Well, I can report that my new Volvo D1-30 doesn't have any decompressors. I believe it has glow plugs, but only uses them in cold weather (there's no manual switch; when you press the start button it decides whether to glow or just start).

Pete
 
25931 said:
......My next move will be to mount some form of extension to the battery terminals so that I can clip on jump leads and I would appreciate suggestions ..
Click to expand...

would it be easier to clip onto the starter solenoid (large terminal) or the alternator output terminal plus any good ground on the engine. These are the same points electrically as the starter battery +/- terminals.
 
Much of the advice given is good. I imagine you have one of those 1,2,both switches which tend to be used by the lazy in both position at all times. It does make recharging easier but then effectively robs you of the isolated independent battery concept.
I would second the suggestion that you rewire the arrangement to use a Voltage Sensing Relay. This enables fully isolated battery systems with an automatic coupling together only when engine is charging. You will need 2 plain isolation switches one for each battery system ie engine and domestics. Then fit an emergency battery paralleling switch which will wire the 2 batteries for jump start. This type of systems means also that you can have a specialised engine start battery type and a specialised domestic battery (deep cycle) if you want.
If things are done correctly you should never need to remove your car battery to the boat for jump starting. Using clip on leads can be dangerous if sparking occurs especially near the battery where hydrogen can build up. If you want to extend the battery leads outside the battery box make the connection points some distance from the battery for safety.

There are 2 schools of thought on jump starting. With a good system it is only necessary if engine start battery dies. As it will eventually. To parallel another battery (your domestic battery or car battery) will add current to the bad battery to help start the engine. This means that when the engine starts you begin to charge the bad battery so just disconnect the jump battery.
On the other argument a battery that dies in some cases will simply discharge the jump battery so should be disconnected. Once engine is running it can be tricky to change from jump battery to original battery for charging. ( to test if battery is really dead.)

if you have a 1,2,both switch and habitually operate in both position. Beware you can have a battery die ie unable to start the engine alone but not be aware of it because the other battery has made starts possible. If you allow this to happen you are really back to one battery (non) reliability. These switches should only be in both position when engine is running. Start on alternate batteries each start and use just one battery for domestics. So if it is left on only one gets flattened.
Also as said it must be a tiny trickle charger if it did not provide enough charge over several hours for an engine start. Check it out may be a blown fuse or similar. Use an amp meter to check actual charge current.
good luck olewill
 
Just to add to the woes of the OP, discharging the batteries (and then leaving them discharged for a couple of weeks or more) is a really good way of killing the batteries.

One other thought: the trickle charger might not have been charging at all. Some chargers don't like being asked to charge totally flat batteries. They need to 'sense' some voltage to get them going.
 
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