The Offshore Voyaging Reference Site

Beware Lithium Battery Sales

In the last few weeks I have been getting a series of emails from Battle Borne aggressively promoting sale pricing on their lithium batteries, see the above.

As far as I can see, these are batteries that don’t have any way to communicate with external charging sources or even a way to inform you that they are about to load-dump and turn your lights out.

In our opinion, this type of battery is:

And further, our advice is that only batteries that can communicate through CANbuss (wires), not Wi-Fi or Bluetooth, with charging sources and monitoring systems should be used on boats, particularly offshore boats.

Much more here:

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Dick Stevenson

Hi John,
I believe the designer of the well-thought-of and communicates with lithium batteries alternator regulator (Wakespeed) is working at Battle Born and that BB is working towards communication capability for its batteries. I wonder if the sale is a “load dump” of soon to be “old design” batteries?
My best, Dick Stevenson, s/v Alchemy

Robert Cart

In the article about load dumps linked above, there is a little misinformation. When a BMS takes a battery offline it is not always a “load dump”. A load dump is when a load is removed suddenly before a generator can wind down. This burns up alternator diodes and causes transients that wreak havoc with electronics on board. However, when a BMS opens contacts without any charging source online, for example when undercharged, this is better called a source loss, inconvenient or worse, but not a load dump.

Stein Varjord

Hi Robert,
That’s exactly why “load dump” is the correct description. When the BMS disconnects the batteries it’s usually because they are getting charged too full. The charging source, usually the alternator, will suddenly loose its load, which causes a voltage spike, which fries the diodes and possibly other sensitive items connected to the same circuit.

Most such batteries are also too stupid to separate between a charge bus and a load bus. When there’s too much power on the batteries, we’re not allowed to use any of it…. The boat goes dark because of fully charged batteries. Incredibly poor thinking from the manufacturers. Or perhaps they did understand this, but were in a too big hurry to rip off an incompetent market?

Robert Cart

Hi Stein, a BMS also disconnects the battery when it is undercharged. Lithium cells cannot tolerate being fully depleted.

Drop in replacement LiFePO4 batteries have inbuilt BMS’s with only a single contactor (or usually mosfet) to take the battery offline when trouble is afloat.

My opinion is that these batteries serve a purpose and if understood for what they are, they are useful. However, you cannot guarantee their availability unless you manage them, so you can guarantee they do not see these trouble conditions. Protecting electronics from a load dump is only one trouble case, but any time you lose needed power it is a hassle or worse.

Robert Cart

Not to beat a dead horse, but it’s best to try to get everyone on the same page with accurate terms. Incorrect terminology often leads to confusion. Someone might incorrectly think that by solving an actual load dump situation they have also solved all cases when a battery goes offline unexpectedly for other reasons.