Lithium Ion Batteries
Hi All,

The cranking battery on my Swan 43 (Firebrand II, 41) is located under the navigation seat, along with a "smart" battery charger and a manual and an electric bilge pump. The battery has a capacity of 80 amp-hours and takes up a lot of space. I am currently looking at installing an additional high volume emergency bilge pump in the same area but will need to reduce the size of the battery.

I have been told that Lithium Ion batteries are much lighter and more compact than traditional Lead-Acid batteries. Has anyone had experience with Lithium Ion batteries in their Swan? If so, what sort of capacity would I require to provide adequate cranking power for a Volvo D2-40 diesel?

Also, is it possible to run a Lithium Ion cranking battery with Lead Acid house batteries. My house batteries are 3 X 80 amp hour Lead-Acid batteries and are relatively new. If possible, I would look at keeping them, at least until I get a bit further with the restoration work.

Best regards
Andrew
(Firebrand II, 43/41)

Dear Andrew
Suggest you also look at Optima Red Top starting batteries. The model 25/35 footprint is 237 x 170 mm, and it has sufficient cranking power for your engine, Volvo specified 700 CCA.
If it fits in there may be some cost advantage.

Kind regards
Lars

Hi Lars,

Good to hear from you. The Optima 25/35 looks like a good option for me. It's just over half the size of the existing battery and comes in well under half the cost of the Lithium Ion battery. An added advantage is that I won't have to alter the charging system.

I may revisit Lithium Ion batteries if I need added storage capacity in my house batteries when I eventually get to doing some extended cruising.

Many thanks for your help.
Andrew
(Firebrand II 43/041)

Andrew, while I'm not able to answer your capacity question, I have recently bought a set of LI batteries (at great cost) for my electric canal boat in Amsterdam. They have a lot of power for their size and weight and they can be left part charged which works well in this application.

I have had a couple of problems with my Mastervolt batteries though: 1. they have a power managment system on each battery which uses power even when the power is turned off on the boat. 2. I have had a sudden cut out for no logical reason requiring a battery reset.

Net, net I would recommend a more conventional battery for engine starting and see where the LI technology and prices go over time. That's what we will do on Tigris. Gavin

Hi Gavin, Professor,

Thanks for the advice. I think I'll wait a while before looking at the Lithium Ion batteries again. The thought of a small but constant drain from the battery management system is a little disconcerting as I don't have solar or wind generating capability as yet.

I'll be going with an Optima Yellow Top D34 lead acid battery. It's quite expensive for a lead acid battery, but still much cheaper than an equivalent Lithium Ion battery. It is also very compact relative to the old battery (less than half the size). This should provide the space I'm looking for under the navigation seat.

The D24 is only slightly larger (16 mm longer) than the Red Top 25/35, but has a bigger capacity (55 Ah vs 44 Ah). It also has deep-cycle capability rather than just providing a high starting current. I think this could be an advantage as my starting battery is also used to power my anchor winch.

Many thanks for your help,
Andrew
(Firebrand II 43/041)

Dear Andrew
When using the anchor windlass it would be advisable to also keep the engine running. The alternator will charge and reduce the load on the battery.
Kind regards
Lars

Thanks Lars,

That is my intended normal mode of operation.

Best regards
Andrew

Hi again Lars,

We are currently in the process of replacing the cranking battery on Firebrand II.

We have found that the bilge pump is connected to the cranking battery and not to the house batteries.

The previous owner kept Firebrand II on a swinging mooring and left her unattended for long periods of time. This may explain the size of the previous cranking battery.

Is it normal to run the bilge pump from the cranking battery, or should we be looking at swapping it and the new high volume emergency pump over to the house batteries?

Best regards
Andrew
(Firebrand II, 43/041)

Dear Andrew
Here an excerpt from the ISAF offshore special regulations:
"When an electric starter is the only method for starting the engine, the yacht shall have a separate battery, the primary purpose of which is to start the engine."
The meaning of this is that the starting battery must not be used to feed other consumers.
Kind regards
Lars

Hi Lars,

Thank you for the information. I thought the set-up was a bit strange. We have now installed the new cranking battery, and have connected both the old and new bilge pumps directly to the house batteries.

Best regards
Andrew
(Firebrand II, 43/041)