electrical

Way back, when computers were young (me too) I was a technician keeping the temperamental mainframes of the time running…most of the time…sorta..OK, we considered 90% up-time a win.

Yup, the things broke down a lot! But one thing I never had trouble with was the supplies and conductors that passed hundreds of amps at just 5 volts—you think, low voltage coupled with high current is a problem on boats!

No overheating contacts, no poorly seated lugs, no hot wires, no nothing…not ever.

Why? Because all the components, both current producing and consuming, were rack mounted.

Racks With Backplanes Are Better

That said, it’s not the rack that was the only secret of this reliability, but rather that the current passed through mainly solid conductors—copper bars if memory serves—rigidly attached to the backplane.

Now I’m not an electrical engineer, but even so I think we can say with confidence that rack mounted backplane systems are intrinsically more reliable that typical sailboat system where components are spread all over the place and then connected together with flexible cables, each of which must be custom built on site, with all attendant opportunities for the installer to screw up—heck, just crimping a lug to pass several hundred amps reliably is a non-trivial skill.

Update 7th October: In light of things I learned in the comments, I made a few changes to this Tip including reducing the level of charge to 70% (from 80%) and sharing Emile’s experience with the Bluetooth in Victron Smart Lithium batteries.

A couple of weeks ago I read a particularly interesting article over at Pambo about the risk of trashing lithium batteries over a winter when the boat is stored in a cold location.

I highly recommend reading the original article in its entirety, but the key things I took away were:

1. LiFePO4 batteries do self discharge over time. 2-3% a month is a good estimate.
2. Parasitic loads that remain connected to the batteries can dramatically increase that discharge rate to the point that the batteries, if not regularly recharged, can be toast in just a month or two.
3. Most lithium batteries will be damaged if charged with the temperature below about 5C (41F), not very cold, making things doubly difficult to manage while the boat is stored in a cold place.
4. However, lithium batteries can be stored at much colder temperatures without damage; for example, Victron Smart Lithium can be stored down to -45C (-49F), which should work in most places.

Clearly the problem here, at least over say a six-month period, is not self discharge. For example, the battery could be charged to say 70% in the fall and six months later would be still a bit over 50%, assuming 3% (worst case).

Rather the real culprit is parasitic loads from the BMS as well as any connected monitoring systems, which can flatten the battery to destruction in a month or so.

Still Required?

Ever since we published my thought that lithium batteries had come of age, I have been pondering whether or not they have reached a point of reliability that would make me comfortable installing them on an offshore boat without the lead-acid serial backup we have recommended for years.

After all, we now have systems from Victron and Mastervolt that have, or at least can have if configured properly, redundancy with two or more BMSs. So surely the time has come?

After giving it a lot of thought, I’m not convinced, and would still install a serial lead-acid backup to support critical loads while upgrading to lithium on an offshore boat of mine.

Here’s why:

The release of the new Victron NG Smart Lithium Battery, that I wrote about a few days ago, got me musing about where we have got to with lithium batteries generally. Here’s how I see the state of play through the lens of my own experience.

Ben Stein, over at Panbo, has just published a good review of the new Victron NG LiFePO4 batteries and related BMSs, well worth the time to read for most any cruiser who is even faintly interested in lithium batteries.

I won’t try to duplicate the excellent job Ben has done describing what makes this new system from Victron exciting, but rather I’m going to highlight a few things that jumped out at me as probably¹ making this a good option for offshore cruising boats, particularly when paired with one or more Lynx Smart BMS NG(s):