Fitting Lithium, and other Electrical improvements

Midnight Star’s batteries were shot, to be honest. Despite six hours cruising days on the way from Gayton to Aylesbury, the inverter and fridge kept giving up the ghost if we stayed up too late. There was a new starter battery with it’s own 35 amp alternator, and 4 110aH leisure batteies which were by my estimate over 5 years old, charged by a seperate 70 amp alternator. The Shoreline could also charge the domestic batteries through the Victron Pheonix 1600/12 Invertor Charger – an old model that used a serial cable for connection to a computer, rather than the VE Direct bus.

The easiest option would have been to buy 4 cheap lesiure batteries, which would be good for a few years, or some more expensive ones that might last longer if we looked after them. We would probably need some monitoring equipment and avoid taking them below 50%. So, there goes the best part of a thousand pound.

The previous owner Glenn was very enthusiatic about fitting Lithium batteries to his new boat. He had bought a pair of 100aH drop in ones and with similar charging devices was getting plenty of life out of them. I asked on a Facebook forum and got mixed responses – the technology was too new, too expensive, there was nothing wrong with the old tech and so on was the general consensus. However, I continued to research how much we might need to spend and soon Firefox and my phone were swamped with advertising.

As I write this there seem to be three routes to go. Homebrew involves buying (possibly used) Lithium Iron Phosphate cells and being an electronics buff. Buying “drop-in” replacement batteries with their own built in management systems appears to be a simple solution, but there were a lot of worring unknowns in my opinion. The “proper” route was likely to be a full Victron system which would require well over £2k. I kept researching the middle option. Glenn had bought some Relion batteries, but they had gone up in price since he bought them. One supplier that did crop up on Google was Quality Source, and I decided to get in touch with then for advice, as the batteries seemed affordable. That turned out to be a very good decision, or at least I hope it turns out to be!

  • One 200aH Novel battery would mean it stayed in balance, two 100aH batteries would need occasional seperate charging to ensure they were used evenly, but were £400 cheaper.
  • If Lithium batteries fail, they just die completely, so having two would provide some form of backup.
  • It would be unwise to charge them directly from my alternator – the batteries should be OK but the alternator might not cope with long periods of high current and sudden cut off. There were various options to overcome this, but one solution was a conventional LA buffer battery feeding a Victron DC to DC convertor.

I decided to keep one of the leisure batteries in the engine bay to use as a buffer/protect, and fit the Lithiums inside the back cupboard. I’ve boxed them in but have the option of fitting fans to the box should they need cooling – they are near the hot water tank. It’s a relativly simple system should it turn out to be required.. The built-in BMS for each lithium should protect from charging at high or low temperatures that could damage them. The DC-DC convertor supplies up to 30 amps of charging to a Lithium profile. It can be disabled from charging with a switch, and is also bluetooth controlled, so you can transfer power from the buffer battery should you need to, even when the engine isn’t running. Here is a modified diagram based on Victron documentation.

When the kit arrived I could log into the batteries via bluetooth before I even took them out of the packaging! For the testing run I removed three of the LA leisure batteries from the engine bay and put the lithiums in their place. The Orion was attached to the steel bulkhead between the engine bay and the rear cupboard via tapped holes and bolts, and the wiring adjusted to suit.

When it was time to do the fitting properly, I was going to need proper Bus Bars and fuse holders inside the cupboard, particualrly if we wanted to add some proper solar power at a later date. For this I bought a Victron Lynx DC In box and followed the instructions on the internet to add four Mega fuses. A lot of effort (and money!) went into the cabling. A new battery Isolation switch was required for the buffer battery, and while I was about it I re-boxed that in as well. While doing so, I also improved the way the starter battery was fixed in the light of a looming BSS test.

More expense ensused when we decided to replace the working but shabby 12 volt fridge. To buy a 12v vewrsion what would be a £120 mains fridge costs arounf £500, because the compressor needs to be changed and the fridge re-charged. We bought a simple under-counter fridge form Inlander which didn’t have a freezer compartment to give more space for the likely contents.

Fitting should have been a simple swap with the old one, but we took advantage of a fan connection that when live when the compressor was running to fit a 12v computer fan to the side panel that would hopfully help the circulation of air over the elements at the back of the fridge and reduce the powe consumption. There was also a serial feed that allowed you to monitor the frigge with a computer, but we just fitted the suppied LED waring device. I’ve yet to see it flash, so eith it doesn’t work or everything is fine!

Another expense was a 12v TV. That would mean we would not need to run the inverter to watch TV, (and experiments showed that it drew quite a bit of current even without a load on it). Thr choice to 12v TVs is a bit better than 12v fridges, but the main brands (Cello and Ferguson) seemed to have quite a few issues, according to the reviews. We found a Sharp TV with both satelite and freeview tuners and Smart apps that could be updated. They could connect via a mobile phone hotspot, and that’s how we intend to watch it when we can’t get a TV signal for now. A satelite dish, dvd player and giving the boat it’s own phone mast may follow later.

A longer cruise is needed to see if we have got the right balance of batteries and appilances, and I suspect that if we don’t quite have enough charging capacity, the next step will be fitting solar panels.