Jumping Lead battery with Lithium

[BrockSolid]

I know this has been discussed, but not exact for my situation that I can find.
Slowly upgrading electronics on my boat. Currently have a very strong lead acid as my crank battery. Plan to run a single lithium for two ten inch graphs.Alreqdy running two lithiums in series for the TM.
i know I can tie them( crank and dedicated graph batteries) together with a jump/kill switch, but have some concerns. Obviously I would need to use a dual purpose lithium.
Just always worry about these things and don’t want to instantly break something, or damage it over time.
Could I just carry jumper cables and jump the crank as I’ve done many times over the years with traditional batteries?

[Zone18]

Might be cheaper and easier just to buy yourself a small jump pack and throw it in the boat.

[SGrem]

Blue Seas Add a battery switch

Will keep batteries and circuits seperate....then can emergency combine when needed.

[Marc Marcantonio]

My electronics dedicated battery is a 100aHr lithium (not a dual purpose), and my starting battery is an X2 AGM. They are tied together with a battery switch. I have used the battery switch to combine both batteries multiple times with no ill effects and feel comfortable this is a good way to back up the starting battery. Much easier than looking for and hooking up a jump battery, although a jump battery is a viable alternative. When considering a jump battery, I would have purchased one big enough for my truck engine (for dual use) and that drove the price up to the point that when considering the hassle of maintaining it, storing it, and connecting it I ended up going the jump switch instead.

[Mr Phoenix55]

Jump starting lithium with lead-acid battery IS NOT RECOMMENDED.
it can damage the lithium due to different charging profiles and voltage requirements of the two battery types.

[dwtaylor]

Jump starting lithium with lead-acid battery IS NOT RECOMMENDED.
it can damage the lithium due to different charging profiles and voltage requirements of the two battery types.

I think the OP is asking the opposite...jumping a lead battery with a lithium battery.

Most jump starters like a noco gb40 are lithium ion batteries and are meant to jump start a typical lead starting battery.

To the OP, I would recommend keeping a jump pack to jumpstart the cranking battery. A lot of lithiums today don't have the cranking amp rating and on some applications could exceed the bms amp rating and effectively trip the "breaker" inside the bms. There are lithiums rated for dual use and/or cranking and I think that would be more sufficient to wire in with a switch to use as a jumper.

[yam911]

Maybe the term "jump" is being misused.

I suspect the OP means to parallel his lead acid starting battery with his lithium house battery.

In which case the battery with the higher voltage will feed current to the battery with the lesser voltage. In the OP's case the lithium will supply current to the lead acid starting battery.

No problem doing just what the OP proposes.

This from Lithium Hub (Ionic)