Looking into upgrading our failing Absorbent Glass Mat (AGM) house batteries to lithium-ion a couple of years ago, we found the price of a commercial system was somewhat beyond our budget.
Nevertheless, we wondered whether a DIY approach would bring the cost down to an affordable level and started investigating. Much of the information published about lithium upgrades seemed to focus on complex, expensive systems for bluewater boats (with electric galleys, watermakers, freezers, washing machines etc), and there appeared to be very little advice for more modest boats like ours.
So we designed our own system to suit our needs and came up with a simple and affordable solution.
There were a couple of areas where savings could be made immediately: virtually all of the published designs relied on replacing battery chargers for ones with ‘lithium profiles’, but that seemed unnecessarily wasteful and expensive and we designed our system to reuse existing chargers. Similarly, any advice given for alternator charging invariably stressed the need to buy additional equipment, and sometimes a new alternator. Again, this seemed rather extravagant, so our system uses the stock alternator without any expensive add-on electronic boxes.
The whole project went extremely well and the total cost of the lithium upgrade was less than £400; cheaper than buying another set of ‘disposable’ AGMs.
The system has now been in service for over two years, and in every respect a lithium-ion battery has been superior to our old AGMs; in fact, it has performed so well that we would never consider going back
