Monday, May 14, 2012

Lithium batteries

I recently went through the exercise of researching and deciding to change Nimrod's batteries from Lead-acid AGM to Lithium.

I have made a web-page to describe the project, which you can see here.

The editor of Cruising Helmsman has expressed an interest in publishing it.

The Lithium batteries have replaced the AGM batteries with the following gains.
  1. Weight reduction from 192kg to 64kg.
  2. Usable capacity increase from 120ah to 280ah.
  3. Space saving by nearly half.
  4. Life expectancy increased by about three times.
  5. Money saving of $500 to $1,200.
So far sea-trials are favourable.


  1. Hi, I have been following your article regarding your installation of lithium batteries in Nimrod. I have also spoken to the supliers who were very helpful. It would be very interesting to know how your progress has been since the installation, your thoughts on where it could have been improved and whether you are still happy with the performance of the Lithium vs AGM etc.
    Any feedback would be great.

    1. Two years on I am very happy that I changed to lithium batteries.

      A few issues to report.

      1) We were struck by lightning, which fried most of the electronics on the boat, and triggered a complete electrical refit. The lithium batteries came through it fine, as far as I can see. Several marine electrical people have been on the boat and all have been very interested in the lithium batteries, with some significant inputs.

      2) The charging algorithm needs to be a bit different from the algorithm for AGMs. My original charger was a Victron Phoenix Multiplus 12/3000/120. It got fried. I now have a Magnasine MS-2712 Inverter/charger. Magnasine recently released a customizable algorithm which has made it easier to tune the set-up for lithium. It seems to be working well.

      3) The lithiums are more accepting of incoming current, so I can charge them more quickly. The new charger, and a new genset means that I can charge at 160 amps, whereas with the AGMs I could never drink faster than about 80 amps.

      4) The charging is also affected by the voltage curve. With AGMs, the voltage drops with a gentle slope. When the threshold is hit, the charger kicks in. Maybe when the battery bank was down to 80%. With lithiums, the voltage stays high for quite a long time, and then starts to drop more steeply. The curve is like a plateau followed by a cliff. The shape of Uluru. So the battery bank gets a lot lower before the charger kicks in.

      5) I think the Low Voltage Battery Isolator is an important protective device. After the lightning strike, I got mine tested. It proved to be giving phoney security, and didn't cut out at any voltage. I had the JayCar version. I have now replaced it with an Intervolt Voltage Sensing Relay.

  2. Hi Dave
    Enjoyed your blog and adventure, thank you. We are close to launching our Farrier F32 on the sunshine coast and have installed a CALB lithium 180amps system with BCU and Lithium charger as provided by EV power -Perth. I am having a problem with the regulator for the solar panels in that the reconnect voltage for pretty well all regulators (which are all designed for lead acid) is about 12.6- your steca is 12.7v. The normal voltage of a lithium battery is about 13.2v so the panels won't cut back in without a significant load to drop battery voltage. Have you had this problem and if so is it of concern?
    Cheers Ken

    1. Hi Ken,

      As noted above, in the lightning strike many bits of the original electrical system got fried, among them being the Steca. It has been replaced by a Morningstar Tristar MPPT 60A Solar Charge Controller TS-MPPT-60. It seems to work fine, and produces much more input than the old system. I don't completely understand how MPPT works, but I attribute the improvement to that.

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