A123's vs SLA's AH relationship
- Thread starter Spanky
- Start date
You can draw more amps with lithium. The real advantage is it will not loose power until the last few minutes before full discharge this is why a protection circuit is used. If you use a good lithium cell you can safely draw 40-50a of current. With a lead acid battery voltage begins to sag right after you start your discharge cycle, with lithium it does not sag much until it is done. The smaller ah lithium pack will take you farther on less ah's but how much is needed depends on your setup motor controller etc... The good lithium cells lifebatt, yesa, a123 will last 1000 cycles which means you can go very very far on one pack if you take care of it.
dogman dan
1 PW
Yes. If you were discussing less expensive lifepo4, I'd say just get a 20 ah pack, but with A123's the cost is an issue. A 16 ah pack should deliver 16 ah, untill many miles later, when it starts to wear out. A really high discharge rate can cause some pukerts effect, even with lifepo4, but with a123's it will take a lot of amp rate to do that.
you would need close to 16ah but when you got close to your destination you would still have close to the same performance as when you started with a lithium pack a comparable sla pack would have much lower performance near its full discharge state. The lithium pack if well cared for would last three times longer (more cycles) before it dies and is much lighter charges quickly A123 cells charge in 15 minutes and are a safer chemistry all around but... if a lithium is allowed to drop too low it is finished this is why a low voltage cutoff circuit is required.
pgt400
1 kW
Its impressive to me that your getting 16ah out of 20ah of SLA's. Are they full depleted at this point? What is your average amp draw? What is your average riding temperature? Oh, what brand SLA ?
Phil
Phil
dogman dan
1 PW
Yeah, I'm impressed too, normally you'd expect maybe 12 ah of usable power out of an sla 20 ah pack. Can't be running a big clyte motor. Or he pedals like zoot. But with larger batteries, peukerts does get less since the c rate is less.
Russell
1 MW
Yep, 16Ah from a 20Ah SLA pack seems pretty darn high :| The best I've gotten from my 36V/9Ah SLA pack out on the road is 60% of rated capacity (5.4Ah) when discharged over 1.5 hours. I'm replacing that nearly 18 lb pack with (3) 36V Bosch Fatpacks with which I'm hoping to get 6Ah, with a 60% weight savings. The weather has not cooperated however so I haven't been able to test them yet. Oh yeah the best part was the price; $119 after a 12% MS Cashback from eBay 
-R
-R
Thanks for all the input!
My cycle analyst shows 15 to 16AH used after each commute! I'm running X5 - I forget the name on the batteries, I've got duck tape covering the batteries and all the strapping to hold them on the bike. I live in southern California (Woodland Hills), so tipical tempetures in the 60's in the morning and 70's on the way home in the evening. 26 miles each way!!
I'm thinking about buying 128 of the ebay A123's and build a pack, and want to make sure I've got enough to make my commute!
My cycle analyst shows 15 to 16AH used after each commute! I'm running X5 - I forget the name on the batteries, I've got duck tape covering the batteries and all the strapping to hold them on the bike. I live in southern California (Woodland Hills), so tipical tempetures in the 60's in the morning and 70's on the way home in the evening. 26 miles each way!!
I'm thinking about buying 128 of the ebay A123's and build a pack, and want to make sure I've got enough to make my commute!
Russell
1 MW
My guess is either the batteries are bigger than you remember or the CA is not calibrated to your controller.
NOBODY gets 80% from SLA's on an electric bike :wink:
-R
NOBODY gets 80% from SLA's on an electric bike :wink:
-R
tostino
10 kW
I agree with Russell, you are not really getting that many AH for the size of the battery. To get 80% out of even the best SLA, you will need to discharge them at about c/5. For a 20ah battery (at c/20) that is 4 amps. Hardly enough to get you moving.
Russell
1 MW
Spanky said:
You can put an ammeter between the battery and controller and compare the amp reading on it with the instantaneous amps displayed on the CA.
-R
Kurt
10 kW
Even if you just use a cheep multimeater you can measure up to 10amp's dc. So you will have to be carfull how you go about it. Set the meter to amps dc, disconect one of your power lines from the battery and run the power through one of the meters probes and out the other so the current flows through the meter. Even if you just tape the wires to the probes.
Do it so you can have both the CA and meter connected at the same time.Then with you brake on simply and very very slowly apply a tiny little bit of throttle you will see the amps go up on the meter and the CA. Compare them.
About getting 16ah from a 20ah sla it sounds wrong to me. I was lucky to get 8ah from my 18ah sla battery's and that's running them until they are all but useless for powering my x5.
Kurt.
Do it so you can have both the CA and meter connected at the same time.Then with you brake on simply and very very slowly apply a tiny little bit of throttle you will see the amps go up on the meter and the CA. Compare them.
About getting 16ah from a 20ah sla it sounds wrong to me. I was lucky to get 8ah from my 18ah sla battery's and that's running them until they are all but useless for powering my x5.
Kurt.
pgt400
1 kW
Maybe he's using Fireflys :wink: I have a new Greensaver comming to compare with a standard SLA.
pgt400
1 kW
Likey just that the shunt cal is 15% or so. Mine was 5-6% off when compared to a Fluke.
John in CR
100 TW
Or just use the multimeter to check the amperage during charging. That times the time to charge is AH put back into them. Reduce that some for the heat loss during charging and that's how much you used during discharge.
John
John
