Hi Joe and any others interested in this topic. I install lithium batteries as my side job and after installing lithium on our 38-ii and other large boats and consulting on another half dozen boats, I can speak with some authority on this topic.
*The risk of serious electrical or fire damage can be entirely mitigated by properly installing the right equipment and following a strict circuit topology. Most people who have installed lithium do not do this and this is precisely why we hear about "lithium fires" so commonly.* Before diving into the details, you should be aware that in order to safely install lithium batteries on a boat, you need to buy top-quality gear that is compatible with the exact lithium chemistry of your batteries. Can you use an AGM charge profile from the old charger you have lying around? Sure, you may be willing to take more risks than others but this is not acceptable in a professional install and it also reduces the efficiency of your expensive batteries that you bought for their high efficiency in the first place! It is these "indirect" costs of making the lithium safe aboard that will dramatically increase the investment cost. Also, in order to take full advantage of the perks of lithium you need to be able to efficiently charge the system. This means a substantial solar array or very high output alternator (often requiring serpentine belts and larger pulleys). *For the weekend sailor or anyone tied to a dock most of their season, these costs cannot be justified over conventional lead-acid or AGM technology.* My wife and I live aboard and spend our entire season on anchor or mooring. This is where lithium shines. We have 720 watts of solar and 320 Ah of lithium. *We run a fridge, separate freezer, fans, computers, microwave, electric kettle, with enough excess power each day to either make 6 gallons of hot water through the inverter or run a 5000 BTU air conditioner on high for 5 hours through the night.* We have all the luxuries of home and are never concerned about running out of power. *The details:* The Battleborn, Dakota, and Renogy batteries that advertise *a "drop-in" replacement for lead-acid should never be used on a boat*. These were designed for van-lifers who can pull over and escape if something goes horribly wrong. The key with lithium is that you need to protect both your boat and its electronics and your substantial investment in batteries. Lithium batteries will not tolerate overcharging, this is where the fire risk comes in. On the other hand, over-discharging will not cause a fire risk but will destroy your battery. The "drop-in" replacement batteries "solve" this by disconnecting their terminals in the case of either overcharge or over-discharge. This is unacceptable on a boat for two reasons: 1) most obviously, if you lose all DC power underway, you no longer have VHF, depth, chartplotter, bilge pumps, radar, etc. 2) if the alternator is spinning but there is no battery to accept the charge, it will send unregulated voltage through the entire electrical system. The proper way to install lithium involves implementing a dual-DC bus topology where all of the charge sources come into a single "charge bus" and all of the loads run on a separate "load bus". Victron Energy is the only company with off-the-shelf batteries and related components to implement such a system. Of course, the savy DIYer can build their own lithium banks and program a compatible battery management system to achieve a similar end result but this involves a serious appreciation for the nuances of lithium and circuitry design. Essentially, a battery management system (BMS) will both balance the individual cells in a battery and measure the voltage of each cell. If any single cell reaches its upper voltage threshold value, the BMS triggers a relay to disconnect the charge bus and prevent overcharging (keep in mind, there are other steps necessary to protect alternators, I'll come back to this later). If any cell reaches its lower voltage threshold, the BMS similarly triggers a relay disconnecting the load bus to prevent over-discharge. The separation of charge and load busses is critical as it allows the system to recover on its own. In the event of a low-voltage disconnect, the charge bus remains connected and the battery can recharge. In a high-voltage disconnect, the loads are still connected and can bring the battery back down to a safer voltage. To charge lithium from an alternator, you need a lead-acid or AGM in between to act as a buffer (most commonly, this can be your starter battery). The alternator charges the lead battery. Connected to the lead battery is a DC-DC charger that is capable of three-stage charging with LiFePO4 charge profiles. This charger then runs into the charge bus mentioned above. The Victron Energy Orion Smart charger <https://amzn.to/3kaCbG8> is a great choice here (Bluetooth programmable and automatically detects when the engine is running so that you cannot drain the start battery). The buffer battery protects both your boat's electronics from unregulated voltage in the event of a high-voltage disconnect and keeps your alternator from overheating. If you connect a 60 amp alternator to a 100 amp/hour lithium, the low internal resistance of the lithium will allow it to pull more amps than your alternator can keep up with. This will quickly burn out the alternator. Not to say that direct alternator charging of lithium can't be done, but it is usually cost prohibitive as the alternator needs to be extremely high output and have a sophisticated regulator designed for lithium. *The price:* Our lithium batteries, BMS, charge and load relays, shunt, wiring, bus bars, and monitoring computers and displays all in came to about $5000. This does not include the cost of solar charge controllers or panels, inverters, or alternator charging via DC-DC chargers. A 200 Amp-hour system could be done in the manner I outlined above with off-the-shelf parts and slightly less sophistication for around $3000. I hope this gives you and everyone else a good overview of what is involved in both the cost and installation. After writing this all up I feel like I can justify a self-plug. As I said, I do installs and consults part-time. If you're interested in pursuing lithium and just want some guidance I'm happy to answer questions with no strings attached. If you want a more in-depth consultation or are in the southern New England area and want help with the install, my work is high quality and my rates are very reasonable! Feel free to get in touch, Riley (860) 538 8446 On Tue, Sep 14, 2021 at 9:27 AM Della Barba, Joe via CnC-List < cnc-list@cnc-list.com> wrote: > My batteries are about shot and I am thinking of going to lithium > batteries. I have to say I thought I knew this stuff and it seems massively > confusing with a ton of directly contradictory information. One big issue > seems that if the BMS disconnects for any reason, that will do a lot of > damage to your alternator and perhaps other equipment too. Add to that my > regulator does not have a specific lithium setting, I would need to get > into the custom menus and try and make one. > > What seems to be the best bet is just to connect the alternator to the > start battery and use a DC-DC charger to charge the lithium bank. Some of > them also take solar input, so that saves me buying a solar controller with > lithium settings, which is something else I don’t currently have. > > > > Joe > > Coquina > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks > - Stu -- Fair winds and following seas, Charlotte Freeland & Riley Anderson SV Freight Train Middletown, CT USA
Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
