48 volt conversion problem

sseaner

I am looking for anyone that has done a 48v conversion on a series cart with 8 volt batteries. I just did my cart with a PQ motor and Alltrax 500 amp controller. The performance is subpar w/ a max speed of 22 on 23" tires. That is when the controller will give me 100% throttle which it does not do 99% of the time, only 89%. I am using new US battery 8vgce batteries with #2 cable. They are rated at 121 AH. Are these the problem? With the batteries fully charged, the voltage drops to 38 volts on takeoff. This is from the log from the controller as well as a separate volt meter on the batteries. The controller is set for top speed and max amperage. The throttle was checked with the M- terminal cable removed and the controller read 100% throttle and the LED change from green to yellow. Any ideas,

BGW

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PLUMQUICK

38 volts????? You must have a bad battery in your pack. Have you checked each battery with your volt meter under load to find out if you have one battery that is pulling down too far?

scottyb

Robbie I wondered that too? Look at the AH on these batteries. I am not familiar with them but, 121? The smallest 8v I sell is a 165ah but I recommend 190ah to anybody who asks.

Is anyone familiar with these batteries?

sseaner

I charged the batteries to full. 12 hours later each cell was reading 8.52. I used a hydrometer on all the cells and they are all good. I put the volt meter on each battery and then floored the cart. the drops were to 6.74, 6.40, 6.40, 6.40, 6.70, 6.74, It will only give me 100% throttle on first run after a charge. here is a log from the controller on a run after a charge.

TimeStamp,ThrottlePos,DiodeTemp,BatteryVoltage,Out putCurrent,BatteryCurrent,ErrorFlags
11/05/10 13:21:10.839 0,20.3,49.2,4.0,0.0,0x00
11/05/10 13:21:10.933 0,20.3,49.3,8.0,0.0,0x00
11/05/10 13:21:11.027 0,19.3,49.1,0.0,0.0,0x00
11/05/10 13:21:11.120 0,19.8,49.3,0.0,0.0,0x00
11/05/10 13:21:11.214 10,19.8,49.1,37.0,3.6,0x00
11/05/10 13:21:11.308 13,19.8,51.9,64.0,8.5,0x00
11/05/10 13:21:11.402 13,19.3,51.6,80.0,10.7,0x00
11/05/10 13:21:11.480 13,19.3,51.6,76.0,10.1,0x00
11/05/10 13:21:11.573 18,19.8,51.4,112.0,19.8,0x00
11/05/10 13:21:11.683 23,18.8,51.2,148.0,34.2,0x00
11/05/10 13:21:11.761 22,19.8,51.0,136.0,30.4,0x00
11/05/10 13:21:11.855 23,19.3,51.1,136.0,31.5,0x00
11/05/10 13:21:11.948 31,19.8,50.5,200.0,62.7,0x00
11/05/10 13:21:12.042 44,19.3,48.9,288.0,125.4,0x00
11/05/10 13:21:12.136 43,19.3,48.4,252.0,107.7,0x00
11/05/10 13:21:12.230 42,19.8,49.0,216.0,90.6,0x00
11/05/10 13:21:12.323 49,19.8,48.8,260.0,126.4,0x00
11/05/10 13:21:12.417 55,18.8,47.4,272.0,148.3,0x00
11/05/10 13:21:12.511 57,19.8,47.3,279.0,158.6,0x00
11/05/10 13:21:12.589 74,19.8,46.1,362.0,268.3,0x00
11/05/10 13:21:12.683 85,18.8,43.9,424.0,359.2,0x00
11/05/10 13:21:12.777 91,18.8,42.5,417.0,379.4,0x00
11/05/10 13:21:12.870 89,19.3,43.0,384.0,340.3,0x00
11/05/10 13:21:12.964 93,18.8,43.4,360.0,333.2,0x00
11/05/10 13:21:13.058 96,19.8,43.2,345.0,330.1,0x00
11/05/10 13:21:13.152 95,19.8,43.3,320.0,302.4,0x00
11/05/10 13:21:13.245 94,19.8,43.9,292.0,273.7,0x00
11/05/10 13:21:13.339 98,19.8,43.9,296.0,290.2,0x00
11/05/10 13:21:13.433 100,19.8,43.9,294.0,294.0,0x00
11/05/10 13:21:13.527 100,18.8,43.4,292.0,292.0,0x00
11/05/10 13:21:13.620 100,19.8,43.8,276.0,276.0,0x00
11/05/10 13:21:13.714 100,19.8,44.0,252.0,252.0,0x00
11/05/10 13:21:13.808 100,19.3,44.3,242.0,242.0,0x00
11/05/10 13:21:13.902 100,20.3,44.4,240.0,240.0,0x00
11/05/10 13:21:13.995 100,20.7,44.9,228.0,228.0,0x00
11/05/10 13:21:14.089 100,19.3,44.9,220.0,220.0,0x00
11/05/10 13:21:14.183 100,20.3,45.0,215.0,215.0,0x00
11/05/10 13:21:14.277 100,19.8,45.0,203.0,203.0,0


Here is the next run. No 100% throttle;

11/05/10 13:22:28.730 0,20.3,45.4,0.0,0.0,0x00
11/05/10 13:22:28.823 4,19.8,45.4,0.0,0.0,0x00
11/05/10 13:22:28.917 12,20.3,49.4,46.0,5.6,0x00
11/05/10 13:22:29.011 15,20.3,49.4,80.0,11.6,0x00
11/05/10 13:22:29.105 15,20.3,49.2,84.0,12.2,0x00
11/05/10 13:22:29.183 15,19.3,49.1,74.0,10.7,0x00
11/05/10 13:22:29.277 15,20.3,49.0,80.0,12.2,0x00
11/05/10 13:22:29.370 18,19.3,49.2,100.0,17.6,0x00
11/05/10 13:22:29.464 18,20.7,49.1,100.0,18.0,0x00
11/05/10 13:22:29.558 18,19.8,49.0,92.0,17.0,0x00
11/05/10 13:22:29.652 20,19.8,48.9,113.0,23.0,0x00
11/05/10 13:22:29.745 26,19.8,48.5,152.0,39.9,0x00
11/05/10 13:22:29.839 25,20.3,48.3,140.0,35.7,0x00
11/05/10 13:22:29.933 26,19.8,48.3,136.0,35.7,0x00
11/05/10 13:22:30.027 29,20.3,48.2,152.0,43.5,0x00
11/05/10 13:22:30.120 32,20.3,47.9,160.0,51.5,0x00
11/05/10 13:22:30.214 33,20.3,47.9,164.0,54.0,0x00
11/05/10 13:22:30.292 33,20.3,47.9,146.0,48.1,0x00
11/05/10 13:22:30.402 35,20.3,47.9,142.0,49.6,0x00
11/05/10 13:22:30.495 36,19.3,47.9,148.0,53.4,0x00
11/05/10 13:22:30.573 36,20.3,47.9,145.0,52.9,0x00
11/05/10 13:22:30.667 38,19.3,48.0,144.0,54.8,0x00
11/05/10 13:22:30.761 42,20.3,47.5,156.0,64.8,0x00
11/05/10 13:22:30.855 42,20.3,47.4,152.0,64.4,0x00
11/05/10 13:22:30.948 43,20.3,47.4,156.0,66.7,0x00
11/05/10 13:22:31.042 42,20.3,47.5,148.0,62.1,0x00
11/05/10 13:22:31.120 42,19.8,47.5,148.0,62.7,0x00
11/05/10 13:22:31.214 44,19.8,47.5,140.0,60.9,0x00
11/05/10 13:22:31.308 45,19.8,47.6,146.0,65.8,0x00
11/05/10 13:22:31.402 48,20.7,47.3,156.0,75.2,0x00
11/05/10 13:22:31.495 49,19.8,47.1,153.0,75.0,0x00
11/05/10 13:22:31.589 51,19.8,47.2,160.0,81.6,0x00
11/05/10 13:22:31.683 55,20.3,46.8,162.0,89.6,0x00
11/05/10 13:22:31.777 54,19.3,46.8,158.0,84.9,0x00
11/05/10 13:22:31.870 55,19.3,46.8,164.0,90.7,0x00
11/05/10 13:22:31.964 60,20.3,46.9,180.0,107.3,0x00
11/05/10 13:22:32.058 71,20.7,45.8,241.0,172.0,0x00
11/05/10 13:22:32.152 75,21.2,44.9,248.0,184.8,0x00
11/05/10 13:22:32.245 80,19.8,44.5,248.0,197.4,0x00
11/05/10 13:22:32.339 89,19.8,44.0,288.0,255.2,0x00
11/05/10 13:22:32.433 93,20.3,43.1,290.0,268.4,0x00
11/05/10 13:22:32.527 92,19.8,43.1,280.0,256.9,0x00
11/05/10 13:22:32.620 93,20.3,43.2,263.0,245.5,0x00
11/05/10 13:22:32.714 93,19.8,43.7,252.0,235.2,0x00
11/05/10 13:22:32.808 94,19.8,44.0,236.0,221.2,0x00
11/05/10 13:22:32.902 91,20.3,44.1,214.0,195.5,0x00
11/05/10 13:22:32.995 93,19.8,44.4,212.0,197.9,0x00
11/05/10 13:22:33.105 93,19.8,44.9,197.0,182.3,0x00
11/05/10 13:22:33.183 92,20.3,44.9,195.0,178.9,0x00
11/05/10 13:22:33.292 93,20.3,44.9,194.0,181.1,0x00
11/05/10 13:22:33.386 94,20.3,45.0,184.0,172.5,0x00

PLUMQUICK

If your voltage drops to 38 volts at take off..........what does the voltage come back up to once the cart gets up to power?

rabbitreborn

those are SubPar batteries. I tried them once and had the distributer take them back. They will not support the setup you have. They were made specifically as "cost effective" replacement batteries for golf courses. Look at the ratings for the batteries and you will see that at 75 amp draw they have a 60 minute reserve capacity. Your controller is capable of 500 amp output. It's never reaching that because the batteries are incapable of supplying it, but it is DEMANDING more power than the batteries are capable of supplying (that PQ motor is a power hungry beast). Hopefully whoever you purchased those batteries from is willing to exchange them out for a set that is more in tune with your needs. If you are going to use the US Batteries, I would reccommend the US 8VGC XC at a minimum but if you can afford the extra $$ get the US 8VGCHC XC.

scottyb

That confirms what I suspect, Only I have no experience with those... those, 'flashlight' batteries

scottyb

Maybe this is a good time to tell why I loose so many battery sales? I always suggest that people buy the battery with the biggest amperage capacity.... so they get a price on 190 ah batteries from me and 121ah batteries from my competitors ... The smaller batteries will last less time even if they do function.... so you pay less but you get less .... and in some cases ~ not enough.

rabbitreborn

Scotty, even in the "stock" golf cars, they are finding that these batteries will last 3 years Max (and usually not even a full 2 years). I had to spend over an hour explaining this to the Head Pro at a local course. They didn't listen to me, bought the "cheaper" batteries and a year later, called me for a complete fleet swapout apologizing the whole time. They actually tried running the fleet carts 2 rounds a day and discovered that within the first year more than half the cars could no longer make even 1 full round.

scottyb

Thanks for the fleet info. Nothing compares to testing a battery on a few hundred carts for 18 holes a day.

I suspected this was the problem but like I said ~ I have not used these batteries but, the AH looks poor. The motor is a stock rewind from PQ.