Overall the system works well and I’m pleased with it. However charging from the Multiplus is slower than I’d expected as it doesn’t employ Bulk charging for any significant period (if at all).
At the moment our typical discharge overnight is about 20% (ie. morning SoC around 80%; this morning 71%). When starting the generator the Multiplus may enter a Bulk phase briefly (charging at around 110 amps) which is fine, but after a few minutes (and sometimes immediately) drops to Absorption at perhaps 50-60 amps.
Boat consumptionn during charging is typically around 10ah.
I have tried disabling other charging sources (MPPT, DC:DC) but this has no effect.
My understanding (perhaps woefully wrong!) is that when DVCC is enabled the phases Bulk/Absorption/etc. are not relevant as it’s the battery that is controlling charging. Regardless, I’d expect to be able to charge at a Bulk rate when the SoC is 70-80%.
I suspect I’m doing something wrong: I’d be most grateful for some advice!
One question, at what voltage is the charging you refer to taking place, 13.5V or 14.2V.
If you read the Lynx BMS manual you will fi d that once the batteries are fully charged by one cycle at 14.2V, all subsequent top.up charging is at 13.5V until the batteries go below 70% SOC. This means that the charging current will be less. If 70% SOC is not achieved in 30 days then you will get a full 14.2V charge.
You have a massive bank compared to your use, you may be better off charging it every other day as that will then charge at 14.2V and make most use of your generator hours.
You could of course alter the repeated absorption interval and/or the SOC threshold.
See the linked section in the manual, especially the repeated absorption interval and SOC threshold.
Yes, the charging is at 13.5V, and as I’ve not dropped below the 70% SoC level for some time it sounds like your explanation is correct. I’ll try what you suggest.
Our current level of use is modest as we’re just coastal cruising at present. On longer journeys I expect autopilot and watermaker use will increase the consumption considerably.
Could you tell me: if I were to increase the SoC threshold would that have an effect on battery life?
I do not believe it will have a material effect as long as it is not held at 100% for long periods such as when you are in a marina. There are people who claim it is best to cycle them between 20% and 80% and others who say going to 100% is not an issue as long as you do not keep them there.
What I suggest you do not do is give them the full 2 hour absorption charge every day as they will not need that, just top them up to 90/95% and give them a longer charge for balancing every now and then, the default is every 30 days.