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Very interesting article. However, I would have appreciated an explanation of the acronyms (e.g. LFP, SOC).
Yep. Fair point. This article is really part two to the previous article on charging, where we hopefully defined all terms, but we couid have refreshed that.
“solid technical team that is willing to talk you through such issues, I have found that Victron and Sterling Power meet that threshold”
I have much praise for Victron equipment but tech support is not their strong point, in fact, when I contacted them with questions they always refer you to a dealer or distributor without offering any contact info. How were you able to receive tech support from them directly?
Ha! I actually had some access to the European team, in preparing this article.
I can recommend Blue Heron on the Mid-Atlantic area for quality equipment and excellent technical support/questions/solutions.
DC-DC converters are used to change voltage levels, not charge batteries. If you need to charge a battery from a DC source, you should be reaching for a DC-DC charger. Many of those can also be used in power-supply mode where they provide a fixed voltage.
In fact, the datasheet for the pictured product from Victron (the Orion-Tr DC-DC converter) says “Not intended for battery charging. Please consider using an Orion-Tr Smart for battery charging.”
The DC to DC converter is throwing me off a little. But if it was a DC to DC charger, are you saying that the alternator would charge the start battery and then the DC to DC would charge the lithium house bank? I thought it would be the other way around?
This might be a boiling the ocean question but can the DC to DC charger work both ways. Where by When being charged by the shore power the lithiums take the charge and then charge the start battery through the DC to DC charger and when being charged by the alternator the start battery then charges the house bank lithiums through the DC to DC charger? Clear as mud.. 🙂
To start from first principles, you don’t want to mix different chemistries on the same circuit. That means the house and start systems need to be entirely separate. The only exception is a DC to DC converter, becayse, technically, that does not represent a direct electrical connection (as they rely on an electrostatic or electromagnetic transfer of energy). As the lead acid and LFP systems charge at slightly different voltages, the simplest form of DC converter is a simple (fixed ratio) voltage dropper. The more sophisticated ones have ‘smart’ capability, which means that they can act in a more sophisticated way (most obviously with a CC/CV charge profile). A key point in the article is that DC converter manufacturers do not always make those sort of details clear. That may or may not matter too much, depending upon what sort of current it is delivering. So, to summarize, the typical system consists of an engine alternator connected to a lead acid battery and that feeds the input side of a DC converter, the output of which charges the LFP. You raise a good point, however, which is whether a DC converter can deliver a current in the opposite direction (eg can the LFP house system charge the lead acid start battery)? The answer is only if you buy a ‘bi-directional’ DC-DC converter (and, so far as I am aware, only Sterling Power offer one). I installed an Sterling Power bidirectional converter on my boat and it helps a lot, as you know that the start battery never gets neglected.