A full and idle state of charge is indicated by a voltage of 12.7. Anything higher is either an indication of a charge being applied or the phenomenon referred to as surface charge. Generally a "dead" battery will read 10.5v or less. You should typically avoid discharging below 11.6 for the most number of years of service. I don't know what voltage the Li-ion battery packs read under no load but it has to be greater than 12.7v. However, the no load voltage is irrelevant since it actually only represents how much potential is present. Once attached to a "dead" battery the output of the jump pack will equal the terminal voltage of the dead battery. The terminal voltage will begin to rise as the starting battery is charged if by some strange condition you were able to supply so much more voltage than the battery could accept then the terminal voltage would be higher than the state of charge and if it was enough higher could theoretically reach the ACR voltage of 13.6. This seems unlikely and would absolutely necessitate and no load voltage much higher than 12.7. Old style jump packs with lead acid batteries or simply jumping a car with a spare battery only has the potential to start at 12.7 on the full battery ~10.5 on the dead the potential will eventually equalize between the two and assuming the same capacity you would end with 2 batteries at roughly 11.6 (I've over simplified it but for the purpose of discussion I think the example works).
In short, I agree with the previous listers that getting the terminal voltage to reach 13.6v and having the ACR engage would be unlikely at best. And that assumes that your ACR senses the start battery and not the house batt. If your alternator is applied to the house then there is no question the ACR should sense the house. However it *MIGHT* also sense the start. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Tue, Jul 14, 2020, 17:27 Charlie Nelson via CnC-List < cnc-list@cnc-list.com> wrote: > Following suggestions on this list, I purchased a NOCO Lithium battery > 'jump starter' to have on board if/when I might need to jump my starting > battery. Cheaper and lighter than another 12 volt battery and having done > this many times in various cars I have owned over the years, it is no big > deal to jump a dead battery. > > However, my boat has an ACR which, as I understand it, works to keep the > batteries charge states more or less equal while they are being charged, > either from shore power or the alternator. When no external charge is > supplied, it isolates the battery banks. So if it works as it should, and > my house batteries are drained accidently or just fail while at anchor > (say), I should be able to use the start battery to start the engine. In > fact, my battery switch has 2 positions (besides OFF), 1 (Normal) and > Combine Batteries. Unless both battery banks fail at the same time, I think > I would always have on board power to start the engine. In the very > unlikely event that I lose both battery banks, my NOCO might save the day. > > So here is the question in this unlikely scenario: > > When I jump start the engine, do I hook up the NOCO jump starting battery > to the 'start battery' in the boat? If the ACR has not failed, would it not > sense the increased charge state of the boat start battery and immediately > share the NOCO jump star power with the house batteries? If these are also > depleted, my NOCO jump starter might not have enough power to start the > engine, since the ACR would send a lot of this power to the house > batteries. > > If the above is not 'over thought', it suggests that I should isolate the > house batteries from the ACR before I try to jump the boat start battery > with the NOCO jump starter. > > Thoughts from the list would be appreciated! > > > Charlie Nelson > Water Phantom > 1995 C&C 36 XL/kcb > > > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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