Lithium Battery FAQ

Posted by Peter Kennedy on 2/13/2019 to Batteries (Lithium Ion)

Have you read my other blog posts on the MultiPlus and Lithium batteries?

Blog posts about Lithium Batteries
Blog posts about the MultiPlus and Quattro inverter/charger

My boat has Batteries and Inverter/Charger in the engine room. Would I be able to install Lithium in the same spot or would I have to move the batteries? If I had to move them, do I have to move the Inverter/Charger too?

Lithium batteries are a lot less troubled by heat that conventional batteries so putting them in the engine room is not a problem. They perform normally up to 50 Deg C and don’t use any temperature compensation for charging, storage is OK up to 70 Deg C. They are however affected by cold and with the Victron Smart Batteries charging shuts off below 5 deg C. I would say keep your project simple and keep them in the current location. Regardless of what you do the inverter charger needs to be near the batteries to keep the wire runs short. Inverter chargers are more susceptable to heat however and if you look at the spec. sheets the max output is usually reduced in hot conditions, so if they end up in the engine room you may need to oversize them.

My boat has a Volvo D2-50 engine with a 115A alternator. Would that be able to charge a lithium pack as is or would it need some assistance: either wiring external regulators/centerfielder, wiring in some Buck Boost from start battery to Lithium and just have the alternators charge the start battery, or perhaps something like the Sterling Alternator to Battery Charger? Would there be any issue with charge voltages between the lithium bank and the AGM start battery?

You will need to do something with the alternator. Lithium batteries have such a low internal resistance that they will make alternators work flat out and that could lead to premature failure. One way is to use an external regulator with temperature compensation so the output is reduced when the alternator gets hot. Another way is to use the Buck Boost DC DC Converter to limit the output. In most cases a battery combiner is placed between the (conventional) start battery and the Lithium start battery. This needs to be controlled by the BMS so it only works when BMS "allow to charge" signal is on and when the engine is running. When a conventional battery and a Lithium battery get combined together like this the Lithium battery wins! The system voltage becomes that of the Lithium battery. The Lithium battery voltage doesnt vary much over the charge cycle and only at the end of the charge does it go up noticeably. The start battery will not get overcharged but it would be nice if it had a shore power charger available from time to time to top it off completely and prevent sulfation. You can read more about this in my article about adding an alternator to a lithium battery setup

What to do with some of the other equipment I already have on board? Is it compatible with Victron?

My suggestion here is to concentrate on the batteries. The cost of the batteries is so much that the ancillary equipment to go with them is just a rounding error. In many cases it is possible to work with existing equipment but I wouldnt design your system around it.

Locating batteries on a Catamaran

I wouldn’t recommend splitting the bank between two hulls. They need to be all together in one bank. It is very important that all the batteries work identically. They go to great lengths to balance the cells within each battery and it stands to reason that you also want to balance the batteries themselves so they all do the same work. That means having exactly the same length cable for each battery.

Best candidates for Lithium Batteries

The earliest adopters of Lithium Batteries have been small RV Conversions like the Sprinter Van. The compact size and light weight of the batteries works for these vehicles where weight is important and space is at a premium. The rectilinear space available means it is all equally useful and nobody likes to give up prime real estate for batteries.

Boats came a bit later, the shape means you can tuck batteries away, but there is never enough room of course. The best candidates for Lithium were Catamarans. That is because they already have higher energy demands but they also have more space for solar panels. The bit missing was the link between the two, the batteries. That is why catamarans have for the most part the early adopters of Lithium Batteries.

Monohull sailboats are following in third place. The performance of the batteries doesnt mean anything unless you can also charge them up sufficiently. The lack of space for solar panels on monohulls means that to really reap the advantage of Lithium batteries they need to improve charging from other sources. Fortunately new pulley kits are now available which allow a substantial upgrade to alternators even on quite small engines.

The least likely candidate for Lithium Batteries are power boats. Its not that they couldnt use a better battery, its just that the advantages may not outweigh the costs. Power boats have lower use for batteries because when under way they always have an engine running that can provide power with an alternator. Battery systems tend to be smaller, there is often a generator. For those power boat owners that want to "go green" Lithium is a great way to go, the flat roofs are great places for solar panels.

2 Comments

Dave Green

Date 2/28/2019

Can you suggest a disconnect relay with low current draw for a 400 Ah 12 v catamaran house bank? Needs to be compatible with a 2 kw inverter/charger.

Peter Kennedy

Date 3/1/2019

The Victron 220 Amp Battery Protect is a low draw solid state relay that could be used but it would be right at its max current rating when powering a 2kw inverter charger and might not be able to handle the surge current. I dont have any bigger solid state relays and mechanical relays will all consume more power. The Blue Sea ML series could be used if you could arrange the turn-on and turn-off signals to be momentary. These relays only consume current when changing state, otherwise there is zero current draw.

Eric Blackburn

Date 5/17/2019

Battery Combiner AGM and Battleborn Lithium. I understand the Lithium "winning" between the batteries, so would the following scenario fix the problem of the starter battery not charging completely? Use a BlueSeas Battery combiner, an AGM starter battery, and Battleborn LifePo4 house batteries (500ah). The Alternator being connected to the AGM Starter battery. The combiner would combine the batteries above 13.0 volts. Since the Battleborn batteries have an automatic stop charge voltage above 14.7 volts (while still allowing discharge), would that then allow the starter battery to continue charging since the effect of the battleborn battery cutoff stops the batteries from being in parallel even though the combiner is still in the combine state?

Regular battery combiners dont work very well with Lithium batteries because the voltage doesnt vary enough to give a cue on when to combine and when to disengage. With the Victron batteries we sell the external BMS (Battery Management System) is available to give a cue to the combiner, Victron have made the Cyrix-Li-Ct combiner just for this purpose. Its not so easy with Battleborn batteries because you dont have access to the BMS, in fact the chief disadvantage of these kind of batteries is the problems you encounter trying to charge them from an alternator. For a bit more on the subject you can look at my other Blog post called "Adding an alternator to your lithium battery setup"