Lithium battery bank as auxiliary starter battery

[nortonscove]

Originally Posted by Pitchondesign

I'm no expert, but starters draw very high amperages, in the hundreds of amps, for a very short time. Typical lithium battery BMS systems will disconnect above a certain amperage, depending on the battery. It seems that you system with two 100 ah batteries might trip those BMS's. Might want to check.

I'm in this camp as the point of your house batteries is extended use but starter requires high amperage for turning the engine over. Better to go with a separate engine battery.

[friz]

Originally Posted by Adelie

Probably want to disconnect starting battery before connecting house or house will start recharging starter batt.

Which is not a bad thing.

[kirklkjb]

Originally Posted by nortonscove

I'm in this camp as the point of your house batteries is extended use but starter requires high amperage for turning the engine over. Better to go with a separate engine battery.

Starting a battery with Lion can be designed in. Tesla and others are moving to them,

250amps or more can be met but it needs to designed for.

FLA is very good at starting so why mess up a good thing?

If you do decide to use the li house batteries you’ll need some 300 amp cables or so and I’d suggest disconnecting the starting battery and the alternator to keep it from burning up. The li jumper kit seems like a better backup.

[Adelie]

Originally Posted by nortonscove

I'm in this camp as the point of your house batteries is extended use but starter requires high amperage for turning the engine over. Better to go with a separate engine battery.

If you have a large FLA house bank of deep cycle batteries (400+Ahr) it should have no problem starting an engine, even drawn down fairly far (50%), no individual battery will have that much demand on it.

The fact that the house battery is LFP changes things, the cells themselves will be fairly content putting out high amps, the problem is the BMS and where it will cut the flow off. It depends on the particular batteries you have and the BMS.

This video shows 316A starting a Yanmar 2QM.

https://www.youtube.com/watch?v=8hX7...ature=emb_logo

Battleborn indicates their 100Ahr battery can put out 200A for 30sec and higher loads for 1/2sec. https://1t1pye1e13di20waq11old70-wpe...-Cut-Sheet.pdf

Assuming the OP has 2 Battleborn or similar batteries and the engine isn't a monster they could probably use the house bank for starting with no problems. 3 batteries would almost certainly have no problem.

How much does the OP's motor draw when starting? He/she should measure it.

[Adelie]

Originally Posted by kirklkjb

Starting a battery with Lion can be designed in. Tesla and others are moving to them,

250amps or more can be met but it needs to designed for.

FLA is very good at starting so why mess up a good thing?

If you do decide to use the li house batteries you’ll need some 300 amp cables or so and I’d suggest disconnecting the starting battery and the alternator to keep it from burning up. The li jumper kit seems like a better backup.

The alternator needs to be left in a circuit so it can charge something.

I assume the alternator is or will be hooked up to charge the house bank generally and the starting battery will be charged vial alternate means (ACR, echo charger, separate alternator...). The only thing that should change is the source of power for the starter.

I would consider setting everything up to run off the house bank except the starter, even the power for the ignition switch and starter relay or have both starter, relay and switch change depending on which battery source is used.

[RogerLloyd]

How can a lithium jump start battery connected temporarily in parallel with a normal lead acid battery, even a house battery, be dangerous ?

[Adelie]

Charged lithium will immediately start trying to charge the low FLA at very high amps. Potential to overheat the starting battery and/or cabling. By high amps I mean 200A for several minutes at least tapering as the starter battery SoC increases.

[facciatosta]

Originally Posted by RogerLloyd

How can a lithium jump start battery connected temporarily in parallel with a normal lead acid battery, even a house battery, be dangerous ?

It depends on your definition of "a normal lead acid battery ".

[facciatosta]

When I added the 3rd AGM battery on my boat to handle the inverter used for the tea kettle and small fridge I added extra wire for the emergency in case I need to use AGM battery to start the engine.
This setup allows me connect any of 3 batteries to the starter individually or in any combination : 1+2, 1+3, 2+3 and 1+2+3. All done manually. I do not know if I ever need it but why to waste extra connection on switch #2 if it can be used?

https://www.cruisersforum.com/forums...cture33249.jpg

[Pete7]

Originally Posted by Adelie

Charged lithium will immediately start trying to charge the low FLA at very high amps. Potential to overheat the starting battery and/or cabling. By high amps I mean 200A for several minutes at least tapering as the starter battery SoC increases.

Just pondering what to do about this. I had planned on a big switch for emergency use connecting LFP house to AGM engine start battery, indeed I already have an spare yellow one from my BEP switch block.

However, I noticed that Will Prowse always connects a resistor to charge up an inverter to avoid the "big narly spark" in his words as the current rushes in. Clark in this YT suggests a power resistor before connecting lead acid to LFP, which is fine setting up occasionally but in an emergency what then? Throw the switch and turn the key hoping for the best?

https://www.youtube.com/watch?v=tAuP...k%27sAdventure

[kirklkjb]

Don't combine LI and Lead like he's promoting. See this: https://battlebornbatteries.com/batt...ium-lead-acid/

Do this instead: http://precisioncircuitsinc.com/wp-c...i-BIM-Rev1.pdf

Its a battery isolator recommended by Battleborn.

[kirklkjb]

Originally Posted by Deividas

Thinking about my Lithium house bank installation. Theoretically, Lifepo4 batteries (2x100Ah Renogy) could be used as auxiliary starter batteries in case the starter battery is discharged.



Will my setup work? Could I interconnect charged Lithium and discharged Lead-acid batteries in parallel to start an engine? And after the engine will start to disconnect the house bank?

Try this instead: Recommended by BattleBorn.
http://precisioncircuitsinc.com/wp-c...i-BIM-Rev1.pdf

Its a battery isolator. Given the description should fit the bill perfectly. It's waterproof to boot.

[Pete7]

Well, we have a series of threads which discuss doing just this, combining lead and LFP batteries:

https://www.cruisersforum.com/forums...nk-244996.html

Post No 1 in this thread is interesting and he isn't alone in doing this.

https://www.cruisersforum.com/forums...en-206424.html

[Pelagic]

Perhaps this is dumb, but why not have a dedicated Start Battery Charger that can be run off of Generator or Inverter when your FLA start batteries have sat too long at anchorage?

I am prepping for LFP in harmony with the Victron Multi 5k upgrade.
I took the old Skyla 24v/50a charger down to ER as a dedicated Start Battery Charger.

This way the two chemistries remain isolated

[Jerry Woodward]

So, I'm trying to put my catamaran on a diet. I currently have a 420AH house bank (4 LA golf cart) and one LA start battery. Last year, the start battery died and I had no problem starting the engines (Yanmar 2gm) with the house bank. This got me wondering why I need a start battery at all. In the event the house bank dies, then I could start the engines with one of these, as mentioned in an earlier post:

https://www.amazon.de/dp/B07MVY7K43/...pa_dk_detail_0
So, this would reduce my weight by about 100lbs, not bad.

When my LA bank needs replacing (pretty soon I think based on its age), I am considering replacing it with a Lithonics 315AH GTX, 68lbs. We don't have large power consumption and this should cover our power needs nicely.


With this, I would get rid of almost 500lbs of lead and replace it with 68lbs of LiPO4. The battery specs look like it would have no problem starting my engines, so I could use it as a house and start battery. I have a Balmar 6 series alt and MC 614 regulator, so the Lithonics battery would provide the alt cut off capability, eliminating the need for a separate LA battery.
Anyone see any problems with this setup?