Lithium battery as starter assist

[ramsaymike]

I am considering changing out the house batteries with a single 100 ah lithium. In certain conditions I need to use the battery combiner dash switch to start the engine. Would this still be possible with the lithium battery? Thanks.

[time2roll]

When you replace the start batteries consider going AGM that run at slightly higher voltage and generally better cranking amps.

[ramsaymike]

Thanks for the feedback. As background, the RV has the Ford 6l diesel and it takes a long crank to start cold due to a 'standplug' issue if I understand it correctly. Cranking speed is critical so if the starter batteries are not fully charged a little help makes a big difference. It is not an every start thing but is does come in handy. I am disappointed with the performance of the cheap house batteries and want to replace with 1 100ah lithium but don't really want to completely lose the battery assist.

[time2roll]

Maybe focus on keep ing the chassis battery charged. Trik-L-Start should work for you. Should also extend the battery life.

[Ivylog]

“I need to use the battery combiner dash switch to start the engine.” Because of the higher voltage I would hold the boost switch down for a minute to charge the engine batteries so even though the Lithium’s BMS will only give you 100 amps, the higher voltage should make the difference.

[pianotuna]

wa8yxm wrote:
I have a little LI battery pack.. designed specifically for jump starting. the battery is TEN that's right 10, amp hours.

Designed is the operative word. I have one that I used when I managed to hatch the battery on my generator. Nice piece of kit.

But the OP wants to use an LiFePo4 for starting. They are NOT designed with that in mind. It might work--but it might not.

It could be used to put some charge into the starter battery. But--how much and for how long?

It also may indicate that for large inverter use, one would need 3 or more LiFePo4, whereas an SiO2 could do the deed on a 3000 watt inverter, without harm to the battery.

[pianotuna]

otrfun,

Great to have those numbers! Thanks.

[otrfun]

pianotuna wrote:
. . . The battery management systems on Li batteries limit the output to about 100 amps (some are more some are less). The starter draws hundreds of amps . . .

Lifeblue 100ah Lifepo4's are capable of 100a continuous, 300a for for 3 seconds, and 500a for 500us (microseconds). I'm not saying you can use a lifepo4 for high surge, starter applications per se, but I believe they are capable of more surge current that some folks realize.

[wa8yxm]

Somethng many are forgetting is the voltage on LiFePO4 is slightly higher than Lead acid. to the Li's may charge the starting batteries

I have a little LI battery pack.. designed specifically for jump starting. the battery is TEN that's right 10, amp hours.

Never tried it on a motor home
but a 4lung car.. Varroom

[2oldman]

pianotuna wrote:
200 amps may not be enough to run a starter motor.

No, but as a bit of help to chassis batteries, perhaps. If it were my rig I'd go with 2.

[pianotuna]

Thanks for the info 2oldman

200 amps may not be enough to run a starter motor. On my Elantra--sure, on a diesel...iffy.

[2oldman]

pianotuna wrote:
Why? The battery management systems on Li batteries limit the output to about 100 amps (some are more some are less).

Battleborn will allow a 200a surge for 30 seconds.

[time2roll]

Yes. However 100 Ah might be light for general use and for the boost start. Worst case it will not work and you will have to do something else to get started.

[pianotuna]

ramsaymike wrote:
I am considering changing out the house batteries with a single 100 ah lithium. In certain conditions I need to use the battery combiner dash switch to start the engine. Would this still be possible with the lithium battery? Thanks.

The short answer is NO, unless there is a massive Li battery bank.

Why? The battery management systems on Li batteries limit the output to about 100 amps (some are more some are less). The starter draws hundreds of amps.

You could do what you want with an SiO2 battery, which are able to do a 4C rate continuously, and 9 C for 5 seconds (400 amps from a 100 amp-hour battery)

[2oldman]

Then you'll need an Li battery that can deliver 2c. Not all can.