Col_T

On your second point @nicknorman. My original question was raised because I haven't seen anything that suggests it can gradually take the load off an alternator when a lithium bank is deemed full - be that at 100%, or 80%, or whatever - so was wondering whether an immediate chop, even with LAs in circuit, would damage the alternator?

Excellent. Very many thanks to everyone that has contributed. I would say this is CWDF at it's best - the question answered, with loads of relevant, detailed information - I couldn't ask for more. Thanks to all.

Thanks for the replies. I think I may not have phrased the question correctly. I understand that the LA battery is retained as a load dump when the BMS switches out lithiums out of the charging circuit; I was more interested in the effect that has on the alternator which, in my mind, goes from working flat-out to idling in fractions of a second e.g. is there any 'shock' loading that may damage the alternator over time? @Tony Brooks - my understanding, or perhaps misunderstanding, is that the battery chemistry effectively controls how much current it can take in 'absorption'. Is the alternator regulating voltage to produce a constant output wattage, or does it sense the current and just output that at the highest voltage it can?

If I understand correctly, a LA battery will take whatever current the alternator can generate in 'bulk' charge mode. In 'absorption' mode, the battery is no longer able to take unlimited current, so the alternator output current drops, and the voltage rises, until the current tapers down to a fully charged point, often defined as 1 or 2% of the battery's AH rating at 14.4v. Is this is correct, the alternator is worked pretty much flat-out during the early stage of charging but then eases-up to come to a controlled near shut-down. Charging an LiFePO4 from an alternator seems to be slightly different, in that the LiFePO4 (lithium) battery can take pretty much whatever the alternator can throw at it right up to fully charged, at which point whatever BMS is fitted should 'disconnect' the alternator to prevent the battery being over-charged. The alternator does not like this sudden 'chop' at all, which is why many lithium installations include LA battery(s) - the BMS switches out the lithiums, the alternator charging current goes to the LA so the alternator is happy. So, now to the question. How does the alternator deal with this if the LA battery is already fully charged when the BMS chops the lithiums from the charging circuit? The alternator will not be able to gently ease-up as it would if it was charging an LA only installation, it would be more like going from 'bulk' straight to 'float' - will this damage the alternator at all? I'm not thinking of going down the lithium route, just pure curiosity!

Or is it water on the camera lens??

Fair comment - but there are many people who are re-assured by documents like this, and who might agitate for the creation of such a thing.

Chap on the DBS Leoch stand, at the recent Caravan and Camping show, told me Lead Carbon are built the same way as AGM.

Thanks one and all - dedicated hull fitting it is.

Fair cop, MtB, we only have 360W of solar fitted so not many. That said, I'm sure I remember a post in which you said your Trojanoids had lost about half their capacity - something else I must have imagined!?

Might that be because your batteries have lost over 50% of badged capacity by any chance?

I'm thinking about installing a washing machine on the boat. The thought is to put it in the cupboard under the sink, so electrical and water supplies will be good and close. The question is about the discharge pipe outlet, and my thought is to connect this to the sink waste outlet, so that I don't need to put a separate hole in the hull, and put a non-return valve between the sink plug and the washing machine connection. Is there a better way of doing this?

Point 4 for Li's then - less time mucking about with batteries is a fair pro. Perhaps not - we, like many others, have sealed, maintenance free batteries installed. The only faffing I do is a quick wipe over with a cloth, and a quick check that there is no corrosion around the terminals, when I'm winterising the boat. I don't have lithiums, obviously, but I would expect they would require some kind of annual check, even if only to check that connections are still tight? If that is correct, then you may be back down to three plus points for lithiums. FWIW - I have also pondered installing lithiums and come to the conclusion that, because we cruise for only six or seven months a year, they don't really offer enough positives to outweigh the cost.

@WotEver, many thanks for this, and your patience! Another piece of the puzzle drops slowly into place!!

Sorry, @WotEver, I didn't ask the question correctly. Given the example of a battery needing 200Ah replaced, why will a 50A charger be in bulk until 150Ah has been put into the battery, whereas a 100A charger will only be in bulk until 100Ah has been put in or, to put to another way, why will the 100A charger not remain in bulk until the same charge level as the 50A charger e.g. 150Ah? Oh, hang on, the penny may have dropped! Are we saying that bulk charge is the phase during which the charger is outputting the maximum that it can, and that that phase ends at the point that the current demanded, and supplied, is less than the maximum the charger can provide?

Could you explain this, please? I'm not doubting you, I just don't understand.