Emergency starter

[Daydream believer]

I know the battery question has been done to death on this forum but I still have a query. sorry for the long explanation
I currently have Volvo 2020 MD & 2 AGM 105 amp batteries as starter & domestic. I need more amps so it has been suggested that I just link the 2 batteries in parallel & use them for combined domestic & starter. When the monitor shows them getting low start the engine & charge them up.
This seems risky so as I have a battery charger that will charge 3 batteries I thought of buying a small emergency AGM battery which will be charged up every time I get shore power. But not connected to the rest of the circuitry as the whole lot is a real nightmare of wiring

At first i thought I would then hook this up to the starter on the engine with jump leads if i got into trouble. I even thought i might put it in the engine bay wire it permanently with a switch & just flick the switch on & off to do an emergency start.

The problem is the glow plugs which need to pre heat
The glows have a relay in the wiring and I do not know why

So if i also take 2 wires to the glow plugs as well as the starter & have a 0-1-2 switch will that heat the glows then start the engine if i just move the switch over or will it run a current back through the rest of the wiring & burn the lot out

 

[pvb]

You already have the wiring for a domestic battery and a starter battery. Simply get an additional battery and transfer the starter battery connections to it - that's now your new starter battery. Then connect the old starter battery in parallel with the domestic battery (you'll need a couple of lengths of cable for this) - that's now your domestic bank.

 

[sarabande]

how about keeping the emergency battery as a separate entity and using a 1-2-Both-0 switch ? Separate connections to the glow plugs seems to be a complicated approach and likely to lead to confusion at an awkward moment. So you have

1 connects the emergency battery ONLY

2 connects the double domestic/engine bank ONLY

Both connects all three, e.g. for charging everything


I shall not go into the the different types of batteries best used for the separate tasks and power strategies of engine starting and domestic use....

 

[VicS]

You already have the wiring for a domestic battery and a starter battery. Simply get an additional battery and transfer the starter battery connections to it - that's now your new starter battery. Then connect the old starter battery in parallel with the domestic battery (you'll need a couple of lengths of cable for this) - that's now your domestic bank.

+ 1 for PVB's suggestion above.

Make sure the new starter battery is of adequate CCA and compatible ( ie another AGM) with the existing. A Red Flash High Rate battery might be a good choice, being of compact dimensions, http://www.dmstech.co.uk/downloads/DMS_data_redflash_highrate_web.pdf.


You can use your 3 output charger for charging the new set up as two banks.... usually the spare charger output would be paralleled with the output charging the larger bank, .... but see its instructions.

Glowplugs are normally controlled by a relay. They take a large current. By using a relay only the small current for the relay coil has to be taken through the ignition/starter switch and associated wiring
There is also a starter relay ( in addition to the starter solenoid)
If the engine is an early version there will probably also be an earthing relay.
Refer to the wiring diagram in the owners manual for details.


You dont however indicate how your present two battery system is managed . What isolating switch arrangement s do you have. Separate or 1,2 both switch. Or how the cahrging is managed. Manually via the switches, diode splitting, VSR or something more fancy.


.

 

[Daydream believer]

I should have mentioned that there is nowhere near the 2 batteries for an additional battery . In fact i am really stuck as to where to put the extra battery. The wiring to the batteries is a bit odd & I really am frightened to strip it all out & place it in a different place. I do not actually know how the engine charges the domestic battery- but it does. Much of the wiring is in ducting & inaccessible. That is why i do not want to mess with it. The idea is to stick a link between the 2 batteries & not touch anything else.
I have considered leaving terminals near the engine ready for emergency starting & just hooking the battery up if needed. I could then keep it in a box in the bow of the boat , hooked up to the shore power charger so it is ready for use
The switching consists of 2 independent switches 1 for each battery

 

[Daydream believer]

Glowplugs are normally controlled by a relay. They take a large current. By using a relay only the small current for the relay coil has to be taken through the ignition/starter switch and associated wiring
There is also a starter relay ( in addition to the starter solenoid)
If the engine is an early version there will probably also be an earthing relay.
Refer to the wiring diagram in the owners manual for details.


.

You are right about the relays as I had one fail on the glows & found it by a process of elimination
Are you saying that because of the relays I cannot just stick a jump lead on a starter to get it to spin & likewise for the glow plugs. because if I can then i can rig an emergency system

On my last boat ( 10 HP Lombardini)I was able to just stick a battery & a couple of jump leads to do an emergency start a bit like I used to do with my cars . I did not even need to use the starter switch because basically i bypassed it. I was just hoping to repeat the system but heat up the glows first as the engine will not start without pre heat.

 

[VicS]

The switching consists of 2 independent switches 1 for each battery

I take it then that you parallel them by simply switching both on ........ no additional paralleling/linking switch ... and that you can can use either for all purposes and charging by switching just that one on. If the engine charges the both batteries regardless of which is selected to be in service there must be some sort of split charging system. Diodes or VSR unless anything more fancy is fitted

You really should take the time and trouble to figure out how everything is wired and draw a decent diagram of it. In an emergency situation is not the time to try to fathom it all out.
Now is probably the time to take the bull by the horns and sort it out to incorporate the additional battery rather than messing about in the way you suggest, ending by up turning something "a bit odd" into total mess.

Separate feed and separate switch for the glowplugs when they should be fed from the engine electrics and controlled by the ignition starter switch ........ ugh!

One of the reasons for suggesting Red Flash batteries is their compactness, meaning that they can be tucked into a small space and even lying on their sides if necessary

 

[Davegriff]

I think the fact that the wiring's "a bit odd" and "Much of the wiring is in ducting & inaccessible" would concern me far more than the positioning of an extra battery.

Bite the bullet - wire the boat properly and in such a way that you can understand it. Won't matter much where or how many batteries you've got if a (serious) fault develops in the loom; a not unlikely situation if it really is out of the ordinary. Best bet always with boat electrics is KISS imho.

 

[Daydream believer]

I take it then that you parallel them by simply switching both on ........ no additional paralleling/linking switch ... and that you can can use either for all purposes and charging by switching just that one on. If the engine charges the both batteries regardless of which is selected to be in service there must be some sort of split charging system. Diodes or VSR unless anything more fancy is fitted

No the batteries are not connected I want to connect them to make use of the combined storage
The wiring at present is as fitted by Hanse from when i bought the boat new- very neat & very complicated.If I get any problems I will be in real difficulty
I have already fitted a reserve bypass circuit to the VHF & GPS in event of a burn out, I just need to couple it to a battery & swop the GPS & VHF wires & I can be up & running in 15 minutes. The wires are run through the panelling etc ready with easily connected terminals & fuse at the end
I just wanted a simple way of bypassing the lot. A diesel engine does not need electrics once it is running. The problem is how to start it if the main batteries are dead
As for the Volvo wiring from panel to engine- it is a total nightmare & I bet most owners would be lost if they had a problem, so i do not think I am alone in this

 

[JumbleDuck]

I should have mentioned that there is nowhere near the 2 batteries for an additional battery . In fact i am really stuck as to where to put the extra battery. The wiring to the batteries is a bit odd & I really am frightened to strip it all out & place it in a different place. I do not actually know how the engine charges the domestic battery- but it does. Much of the wiring is in ducting & inaccessible.

I felt a huge sense of relief last spring when I had pulled out all the battery wiring on my boat and was starting again from scratch, able to build a system I understood. Mind you, the next owner will probably feel the same on taking out my wiring!

 

[duncan99210]

The OP could simply buy a jump start battery pack to keep on the boat. If he gets a flat battery then simply hook the jump start leads to the engine battery and use the pack to start the engine. They need recharging every few months but otherwise are maintenance free and not to difficult to stow in some odd corner.

As regards the glow plugs, provided power is going to the engine harness (from the engine battery and or the jump start pack), then power will also be going to the glow plugs, so no need for any additional wiring to be fitted.

 

[prv]

I felt a huge sense of relief last spring when I had pulled out all the battery wiring on my boat and was starting again from scratch, able to build a system I understood.

Likewise - on two boats now

Mind you, the next owner will probably feel the same on taking out my wiring!

Hopefully not - I gave him a wiring diagram

Pete

 

[JumbleDuck]

Hopefully not - I gave him a wiring diagram

He had meant to do such a lot for Wrykyn cricket this term. He
had had an entirely new system of coaching in his mind. Now it might
never be used. He had handed it on in a letter to Strachan, who would be
captain in his place; but probably Strachan would have some scheme of
his own. There is nobody who could not edit a paper in the ideal way;
and there is nobody who has not a theory of his own about cricket
coaching at school.

From "Mike and Psmith", by P.G. Wodehouse (https://www.gutenberg.org/ebooks/10586)​

The same probably goes for wiring up boats. Anyway, no matter how good the intentions or how diligent the owner, I suspect that all boat electrical systems turn into tangled knitting nightmares over time.

 

[Daydream believer]

The OP could simply buy a jump start battery pack to keep on the boat. If he gets a flat battery then simply hook the jump start leads to the engine battery and use the pack to start the engine.

That seems a simple idea but will the flat batteries suck all the power out of the jump start battery rather than allow it to spin the engine

 

[duncan99210]

That seems a simple idea but will the flat batteries suck all the power out of the jump start battery rather than allow it to spin the engine

If you left the thing hooked up for any length of time before trying to start the engine the of course the charge would simply level out across the batteries. If you hook the thing up and start the engine immediately it'll work just fine.

 

[JumbleDuck]

If you left the thing hooked up for any length of time before trying to start the engine the of course the charge would simply level out across the batteries. If you hook the thing up and start the engine immediately it'll work just fine.

BTDTGTTS. It works just fine. The starter motor takes 100A+ which is way, way more than might be diverted into a flat battery.

 

[Daydream believer]

deleted

 

[Daydream believer]

The OP could simply buy a jump start battery pack to keep on the boat. If he gets a flat battery then simply hook the jump start leads to the engine battery and use the pack to start the engine. They need recharging every few months but otherwise are maintenance free and not to difficult to stow in some odd corner.

So the next question is

What one do i buy? i have heard comments about some being flat when wanted or just poor quality
Anyone with experience - there are lots of suppliers -but are some just carp

 

[sailorman]

So the next question is

What one do i buy? i have heard comments about some being flat when wanted or just poor quality
Anyone with experience - there are lots of suppliers -but are some just carp

i have a Halford`s one at home it cost about 50 sqiuds 2 yrs ago & has a compressor as well that is very handy.it can be charged 12 or 240v

 

[duncan99210]

I bought one from Halfords too. Can be charged either from the mains or from 12 v. You just need to check it every now and then to ensure its fully charged. The instructions recommend charging it once every three months and it has a tag on the handle where you can record when you charge it.