Lithium Battery Conversion

[Tom47]

Originally Posted by Volt_Ampere

I walk the course when the temps are below 95 degrees. From now until late spring I drive the cart to the course, walk 18 holes with a push cart, drive home. Driving distance round trip is 1.2 miles. When I ride the cart on either course, I put about 7.5 miles on the cart including to and from the course.

Biking is the best exercise I get, but 8 miles on our Worksman dual team trike is all I can do these days. Walking more than a mile in any weather does me in.

But I can easily do 20 miles on my cart!

[brianjwilson]

I believe the reason you sometimes need to get a second 48v lithium battery is not just for the desired longer range, but also because the battery has a maximum amperage output that you need to consider for your application. So if you have an upgraded motor / controller / etc. that draws higher amperage, and climb hills, etc., then the second battery ensures that plenty of amps are available when needed. That's my understanding at least. So I believe the recommendation is usually 48v x 2 batteries (to cover the amperage needs), and then add additional batteries only if longer range is needed.

[expoman55]

I am new to the lithium gig as well but from an electrical perspective having 48v cells in parallel ( assuming your cart is 48v as is mine) and to have more AH available perhaps than needed ALSO gives you a backup should one of your Battery BMS systems shut down the overall pack you still have one or maybe 2 packs to limp back home or where ever.. so if you have 2 or 3 48v packs at lets say 30AH and one is down then the other should be able in theory to get you home vs a single 48v pack like a custom offering with a single box ... Just my thinking seems having a little redundancy so to speak.

[Pat911]

Depends on the failure of the first battery. If it fails to a short you’re going to have a very bad situation with one or more batteries connected to it.

I’ve said it before and I’ll say it again, one correctly sized battery is the best solution.

Cheers
Pat.

[Tom47]

Originally Posted by Pat911

Depends on the failure of the first battery. If it fails to a short you’re going to have a very bad situation with one or more batteries connected to it.

I’ve said it before and I’ll say it again, one correctly sized battery is the best solution.

Cheers
Pat.

[expoman55]

Ok so ALL you BMS experts and battery experts : do these lithium batteries not have a BMS and short protection to not open up that battery output ? I would surely think the BMS monitors and all the tech money paid for these batteries single large capacity ( RoyPow ecobat, husky, big battery ) must have same issues if not.. Difference is a closed large pack goes out ALL goes out..

[Volt_Ampere]

They don't have short protection of the battery itself. Some BMS monitor total battery current and prevent overcurrent out of the total battery pack. I use a 300 amp fuse.

[DaveTM]

Originally Posted by expoman55

Ok so ALL you BMS experts and battery experts : do these lithium batteries not have a BMS and short protection to not open up that battery output ? I would surely think the BMS monitors and all the tech money paid for these batteries single large capacity ( RoyPow ecobat, husky, big battery ) must have same issues if not.. Difference is a closed large pack goes out ALL goes out..

My Alltrax Controller has settings where I can limit the amp draw from the battery pack no matter how many amps the motor is requesting.

[Pat911]

@Expoman55

Yes, they have BMS’s which will try to limit the current, but how fast will they react to a short circuit or how much current can they limit before blowing the internal fets? A short circuit on a 48v lithium pack will easily result in 1000+ amps. That will surely do a lot of damage to a BMS not rated for it and will also cause irreversible damage to the cells.

Also, in your example above, using your cart with only one smaller pack to limp home if the other has failed may result in damage to the second pack as you will be pushing it beyond its design limits. Smaller packs use smaller cells and lower rated BMS’s. Smaller cells not only have less capacity, but also have lower supply current limits. A 30Ah pack as you describe will most likely only be able to supply 30A continuous or 60A peak. Not enough for any cart.

Cheers
Pat.

[expoman55]

911 thanks for taking the time to respond.. Just for clarity I wan referring pretty much to 3 - like AH packs ( 30 AH or more) @48v in my example. thanks for the help.